Patent Publication Number: US-11381265-B2

Title: Radio frequency module and communication device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is based on and claims priority to Japanese Patent Application No. 2020-076285 filed on Apr. 22, 2020. The entire disclosure of the above-identified application, including the specification, drawings and claims is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a radio frequency (RF) module and a communication device. 
     BACKGROUND 
     Mobile communication devices such as mobile phones include a power amplifier that amplifies a radio frequency transmission signal. 
     Japanese Unexamined Patent Application Publication No. 2010-118916 discloses a differential power amplifier that includes: a first transistor which receives an input of a non-inverted input signal; a second transistor which receives an input of an inverted input signal; and a transformer disposed on the output terminal side of the first transistor and the second transistor. The transformer includes magnetically-coupled two primary coils and one secondary coil. The two primary coils are connected to each other in parallel, and each magnetically coupled to the secondary coil, allowing the input impedance of the primary coils to be reduced without decreasing Q-factors. As a result, it is possible to improve power gain. 
     SUMMARY 
     Technical Problems 
     However, as recognized by the present inventor, when the differential power amplifier disclosed by Japanese Unexamined Patent Application Publication No. 2010-118916 is applied to a radio frequency front-end circuit that supports multi-band technologies, differential power amplifiers need to be provided for the respective communication bands, leading to an increase in the total number of power amplifiers arranged. Furthermore, the differential power amplifier includes a large number of circuit elements, and thus there arises a problem that the radio frequency module increases in size. 
     The present disclosure addresses the above-described problems, and is presented to provide a small-sized radio frequency module that includes a differential power amplifier and supports multi-band technologies, and a communication device including the radio frequency module. 
     Solutions 
     In order to provide such a radio frequency module and such a communication device as described above, a radio frequency module according to one aspect of the present disclosure includes a module board including a first principal surface and a second principal surface on opposite sides of the module board; a first power amplifier configured to amplify a transmission signal of a first frequency band; a second power amplifier configured to amplify a transmission signal of a second frequency band different from the first frequency band; a first output transformer including a first coil and a second coil; and a second output transformer including a third coil and a fourth coil. In this radio frequency module, the first power amplifier includes a first amplifying element and a second amplifying element, the second power amplifier includes a third amplifying element and a fourth amplifying element, one of ends of the first coil is connected to an output terminal of the first amplifying element, a remaining one of the ends of the first coil is connected to an output terminal of the second amplifying element, and one of ends of the second coil is connected to an output terminal of the first power amplifier, one of ends of the third coil is connected to an output terminal of the third amplifying element, a remaining one of the ends of the third coil is connected to an output terminal of the fourth amplifying element, and one of ends of the fourth coil is connected to an output terminal of the second power amplifier, the first power amplifier and the second power amplifier are disposed on the first principal surface, and the first output transformer and the second output transformer are disposed inside the module board or on the second principal surface. 
     Advantageous Effects 
     According to the present disclosure, a small-sized radio frequency module that includes a differential power amplifier and supports multi-band technologies, and a communication device including the radio frequency module are provided. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other advantages and features will become apparent from the following description thereof taken in conjunction with the accompanying Drawings, by way of non-limiting examples of embodiments disclosed herein. 
         FIG. 1  is a diagram illustrating a circuit configuration of a radio frequency module (or RF front-end circuitry) and a communication device according to an embodiment. 
         FIG. 2  is a diagram illustrating a circuit configuration of a transmission amplifier circuit. 
         FIG. 3A  is a schematic diagram illustrating a plan view configuration of a radio frequency module according to Working Example 1. 
         FIG. 3B  is a schematic diagram illustrating a cross-sectional configuration of the radio frequency module according to Working Example 1. 
         FIG. 4A  is a schematic diagram illustrating a plan view configuration of a first principal surface of a radio frequency module according to Variation  1 . 
         FIG. 4B  is a schematic diagram illustrating a plan view configuration of a first principal surface of a radio frequency module according to Variation  2 . 
         FIG. 5  is a schematic diagram illustrating a cross-sectional configuration of a radio frequency module according to Variation  3 . 
         FIG. 6A  is a schematic diagram illustrating a plan view configuration of a radio frequency module according to Working Example 2. 
         FIG. 6B  is a schematic diagram illustrating a cross-sectional configuration of the radio frequency module according to Working Example 2. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The following describes in detail embodiments of the present disclosure. Each of the embodiments described below illustrates a general or specific example. The numerical values, shapes, materials, structural components, the arrangement and connection of the structural components, and so on, illustrated in the following embodiments are mere examples, and therefore do not limit the present disclosure. Among the structural components in the following working examples and variations, structural components not recited in the independent claims are described as arbitrary structural components. In addition, the sizes of structural components and the ratios of the sizes in the drawings are not necessarily strictly illustrated. In each of the diagrams, substantially the same structural components are denoted by the same reference signs, and redundant description may be omitted or simplified. 
     In addition, in the following description, terms indicating relationships between components such as parallel and vertical and terms indicating the shapes of components such as a quadrilateral shape, and numerical ranges do not represent only the strict meanings but include also a substantially equivalent range, such as a difference of approximately several percent. 
     In addition, in the following description, in an example of A, B, and C being mounted on a board, “in a plan view of the board (or the principal surface of the board), C is disposed between A and B” means that at least one of a plurality of line segments connecting arbitrary points in A and arbitrary points in B passes through a region in C in a plan view of the board. Furthermore, a plan view of the board means that the board and circuit elements mounted on the board are orthographically projected on a plane parallel to the principal surface of the board. 
     In addition, in the following description, a “transmission path” refers to a transfer path including: a line along which a radio frequency transmission signal propagates; an electrode directly connected to the line; a terminal directly connected to the line or the electrode; and the like. Furthermore, a “reception path” refers to a transfer path including: a line along which a radio frequency reception signal propagates; an electrode directly connected to the line; a terminal directly connected to the line or the electrode; and the like. Furthermore, a “transmission and reception path” refers to a transfer path including: a line along which a radio frequency transmission signal and a radio frequency reception signal propagate; an electrode directly connected to the line; a terminal directly connected to the line or the electrode; and the like. 
     Embodiment 
     1. Circuit Configuration of Radio Frequency Module  1  and Communication Device  5   
       FIG. 1  is a diagram illustrating a circuit configuration of radio frequency module  1  and communication device  5  according to an embodiment. As illustrated in this diagram, communication device  5  includes radio frequency module  1 , antenna  2 , RF signal processing circuit (RFIC)  3 , and baseband signal processing circuit (BBIC)  4 . 
     RFIC  3  is an RF signal processing circuit that processes a radio frequency signal to be transmitted by antenna  2  and processes a radio frequency signal received by antenna  2 . More specifically, RFIC  3  performs signal processing, by down-conversion or the like, on a reception signal that has been input via the reception signal path of radio frequency module  1 , and outputs the reception signal generated by the signal processing to BBIC  4 . In addition, RFIC  3  performs signal processing, by up-conversion or the like, on a transmission signal that has been input from BBIC  4 , and outputs the transmission signal generated by the signal processing to the transmission signal path of radio frequency module  1 . 
     BBIC  4  is a circuit that performs signal processing using an intermediate frequency band having a lower frequency than a frequency band of a radio frequency signal that is transferred through radio frequency module  1 . The signal processed by BBIC  4  is, for example, used as an image signal for image display or as a sound signal for telephone conversation via a speaker. 
     RFIC  3  also functions as a controller that controls the connection of switches  41 ,  42 ,  43 , and  44  included in radio frequency module  1 , based on a communication band (frequency band) used. Specifically, RFIC  3  controllably switches connection between switches  41  to  44  included in radio frequency module  1 , by a control signal (not illustrated). More specifically, RFIC  3  outputs a digital control signal for controlling switches  41  to  44 , to power amplifier (PA) control circuit  80 . PA control circuit  80  of radio frequency module  1  outputs a digital control signal to switches  41  to  44  according to the digital control signal that has been input from RFIC  3 , thereby controlling connection and disconnection of switches  41  to  44 . 
     RFIC  3  also functions as a controller that controls the gains of transmission amplifier circuits  10  and  20  included by radio frequency module  1 , and power supply voltage Vcc and bias voltage Vbias that are supplied to transmission amplifier circuits  10  and  20 . More specifically, RFIC  3  outputs digital control signals to control signal terminal  140  of radio frequency module  1 . PA control circuit  80  of radio frequency module  1  outputs a control signal, power supply voltage Vcc, or bias voltage Vbias to transmission amplifier circuits  10  and  20  according to the digital control signal that has been input via control signal terminal  140 , thereby adjusting the gains of transmission amplifier circuits  10  and  20 . It should be noted that a control signal terminal that receives, from RFIC  3 , a digital control signal for controlling the gains of transmission amplifier circuits  10  and  20  may be different from a control signal terminal that receives, from RFIC  3 , a digital control signal for controlling power supply voltage Vcc and bias voltage Vbias to be supplied to transmission amplifier circuits  10  and  20 . In addition, the controller may be disposed outside RFIC  3 , for example, in BBIC  4 . 
     Antenna  2  is connected to antenna connection terminal  100  of radio frequency module  1 , and emits a radio frequency signal that has been output from radio frequency module  1 . In addition, antenna  2  receives a radio frequency signal from the outside, and outputs the received radio frequency signal to radio frequency module  1 . 
     It should be noted that, in communication device  5  according to the present embodiment, antenna  2  and BBIC  4  are not indispensable components. 
     Next, a detailed configuration of radio frequency module  1  will be described. 
     As illustrated in  FIG. 1 , radio frequency module  1  includes: antenna connection terminal  100 ; transmission amplifier circuits  10  and  20 ; low noise amplifier  30 ; transmission filters  61 T,  62 T, and  63 T; reception filters  61 R,  62 R, and  63 R; PA control circuit  80 ; matching circuits (matching network (MN))  51 ,  52 ,  53 , and  54 ; and switches  41 ,  42 ,  43 , and  44 . 
     Antenna connection terminal  100  is a common antenna terminal connected to antenna  2 . 
     Transmission amplifier circuit  10  is an amplifier circuit of a differential amplifier type that amplifies transmission signals of communication band A and communication band B that have been input through transmission input terminals  111  and  112 . It should be noted that radio frequency module  1  may include, instead of transmission amplifier circuit  10 , a first transmission amplifier circuit that amplifies a radio frequency signal of communication band A and a second transmission amplifier circuit that amplifies a radio frequency signal of communication band B. 
     Transmission amplifier circuit  20  is an amplifier circuit of a differential amplifier type that amplifies transmission signals of communication band C that have been input through transmission input terminals  121  and  122 . 
     PA control circuit  80  adjusts the gains of amplifying elements included in transmission amplifier circuits  10  and  20 , using a digital control signal input through control signal terminal  140 . PA control circuit  80  may be implemented as a semiconductor integrated circuit (IC). The semiconductor IC is configured by, for example, a complementary metal oxide semiconductor (CMOS). More specifically, the semiconductor IC is fabricated by silicon on insulator (SOI) processing. This allows manufacturing the semiconductor IC at a low manufacturing cost. It should be noted that the semiconductor IC may include at least one of GaAs, SiGe, or GaN. With this, it is possible to output a radio frequency signal having a high-quality amplification performance and noise performance. 
     Low noise amplifier  30  is an amplifier that amplifies radio frequency signals of communication bands A, B, and C with low noise, and outputs the amplified radio frequency signals to reception output terminal  130 . It should be noted that radio frequency module  1  may include a plurality of low noise amplifiers. For example, radio frequency module  1  may include a first low noise amplifier that amplifies radio frequency signals of communication bands A and B, and a second low noise amplifier that amplifies radio frequency signals of communication band C. 
     It should be noted that, in the present embodiment, communication bands A and B are lower in frequency than communication band C. Communication bands A and B are, for example, communication bands that belong to a middle band group (1.45 GHz to 2.2 GHz), and communication band C is, for example, a communication band that belongs to a high band group (2.3 GHz to 2.7 GHz). However, the high-low frequency relationship between communication band C and communication bands A and B is not limited to above-described example. Accordingly, communication bands A and B may be higher in frequency than communication band C. It should be noted that the middle band group is one example of the first frequency band, and communication band C is one example of the second frequency band different from the first frequency band. 
     Transmission filter  61 T is disposed on transmission path AT that connects antenna connection terminal  100  and transmission input terminals  111  and  112 , and passes a transmission signal in a transmission band of communication band A, among the transmission signals that have been amplified by transmission amplifier circuit  10 . Transmission filter  62 T is disposed on transmission path BT that connects antenna connection terminal  100  and transmission input terminals  111  and  112 , and passes a transmission signal in a transmission band of communication band B, among the transmission signals that have been amplified by transmission amplifier circuit  10 . Transmission filter  63 T is disposed on transmission path CT that connects antenna connection terminal  100  and transmission input terminals  121  and  122 , and passes a transmission signal in a transmission band of communication band C, among the transmission signals that have been amplified by transmission amplifier circuit  20 . 
     Reception filter  61 R is disposed on reception path AR that connects antenna connection terminal  100  and reception output terminal  130 , and passes a reception signal in a reception band of communication band A, among the reception signals that have been input through antenna connection terminal  100 . Reception filter  62 R is disposed on reception path BR that connects antenna connection terminal  100  and reception output terminal  130 , and passes a reception signal in a reception band of communication band B, among the reception signals that have been input through antenna connection terminal  100 . Reception filter  63 R is disposed on reception path CR that connects antenna connection terminal  100  and reception output terminal  130 , and passes a reception signal in a reception band of communication band C, among the reception signals that have been input through antenna connection terminal  100 . 
     Transmission filter  61 T and reception filter  61 R are included in duplexer  61  that has, as a passband, communication band A. Duplexer  61  transfers a transmission signal and a reception signal of communication band A in a frequency division duplex (FDD) system. Transmission filter  62 T and reception filter  62 R are included in duplexer  62  that has, as a passband, communication band B. Duplexer  62  transfers a transmission signal and a reception signal of communication band B in the FDD system. Transmission filter  63 T and reception filter  63 R are included in duplexer  63  that has, as a passband, communication band C. Duplexer  63  transfers a transmission signal and a reception signal of communication band C in the FDD system. 
     It should be noted that each of duplexers  61  to  63  may be a multiplexer including only a plurality of transmission filters, a multiplexer including only a plurality of reception filters, or a multiplexer including a plurality of duplexers. In addition, transmission filter  61 T and reception filter  61 R need not necessarily be included in duplexer  61 . Transmission filter  61 T and reception filter  61 R may be a single filter that transfers a transmission signal and a reception signal of communication band A in a time division duplex (TDD) system. In this case, a switch for switching between transmission and reception is disposed on at least one of a preceding stage or a following stage of the above-described single filter. In the same manner as above, transmission filter  62 T and reception filter  62 R need not necessarily be included in duplexer  62 . Transmission filter  62 T and reception filter  62 R may be a single filter that transfers a transmission signal and a reception signal of communication band B in the TDD system. In the same manner as above, transmission filter  63 T and reception filter  63 R need not necessarily be included in duplexer  63 . Transmission filter  63 T and reception filter  63 R may be a single filter that transfers a transmission signal and a reception signal of communication band C in the TDD system. 
     Matching circuit  51  is disposed on a path that connects switch  44  and duplexer  61 , and matches the impedance of switch  44  and antenna  2  with the impedance of duplexer  61 . Matching circuit  52  is disposed on a path that connects switch  44  and duplexer  62 , and matches the impedance of switch  44  and antenna  2  with the impedance of duplexer  62 . Matching circuit  53  is disposed on a path that connects switch  44  and duplexer  63 , and matches the impedance of switch  44  and antenna  2  with the impedance of duplexer  63 . 
     Matching circuit  54  is disposed on a reception path that connects low noise amplifier  30  and switch  43 , and matches the impedance of low noise amplifier  30  with the impedance of switch  43  and duplexers  61  to  63 . 
     Switch  41  includes common terminals  41   a  and  41   b , and selection terminals  41   c ,  41   d ,  41   e , and  41   f . Common terminal  41   a  is connected to input terminal  115  of transmission amplifier circuit  10 . Common terminal  41   b  is connected to input terminal  125  of transmission amplifier circuit  20 . Selection terminal  41   c  is connected to transmission input terminal  111 , selection terminal  41   d  is connected to transmission input terminal  112 , selection terminal  41   e  is connected to transmission input terminal  121 , and selection terminal  41   f  is connected to transmission input terminal  122 . Switch  41  is disposed on the input terminal side of transmission amplifier circuits  10  and  20 . In the above-described connection configuration, switch  41  switches connection of transmission amplifier circuit  10  between transmission input terminal  111  and transmission input terminal  112 , and switches connection of transmission amplifier circuit  20  between transmission input terminal  121  and transmission input terminal  122 . Switch  41  is implemented as, for example, a double pole four throw (DP4T) switching circuit. 
     It should be noted that switch  41  may include: a single pole double throw (SPDT) switch which includes common terminal  41   a  and selection terminals  41   c  and  41   d ; and an SPDT switch which includes common terminal  41   b  and selection terminals  41   e  and  41   f.    
     A transmission signal of communication band A, for example, is input through transmission input terminal  111 , and a transmission signal of communication band B, for example, is input through transmission input terminal  112 . A transmission signal of communication band C, for example, is input through transmission input terminals  121  and  122 . 
     A transmission signal of communication band A or B in the fourth generation mobile communication system (4G), for example, may be input through transmission input terminal  111 , and a transmission signal of communication band A or B in the fifth generation mobile communication system (5G), for example, may be input through transmission input terminal  112 . A transmission signal of communication band C in 4G, for example, may be input through transmission input terminal  121 , and a transmission signal of communication band C in 5G, for example, may be input through transmission input terminal  122 . 
     It should be noted that switch  41  may be an SPDT switching circuit including: a common terminal that is connected to a transmission input terminal (referred to as a first transmission input terminal) out of transmission input terminals  111 ,  112 ,  121 , and  122 ; one selection terminal that is connected to input terminal  115  of transmission amplifier circuit  10 ; and the other selection terminal that is connected to input terminal  125  of transmission amplifier circuit  20 . 
     In this case, for example, a transmission signal of any one of communication band A, communication band B, and communication band C is selectively input through the first transmission input terminal, and switch  41  switches connection of the first transmission input terminal between transmission amplifier circuit  10  and transmission amplifier circuit  20  according to the transmission signal that has been input. In addition, for example, a transmission signal of 4G or a transmission signal of 5G may be input through the first transmission input terminal, and switch  41  may switch connection of the first transmission input terminal between transmission amplifier circuit  10  and transmission amplifier circuit  20  according to the transmission signal that has been input. 
     In addition, switch  41  may be implemented as a double pole double throw (DPDT) switching circuit that includes two common terminals and two selection terminals. In this case, the first transmission input terminal is connected to one of the common terminals, and the second transmission input terminal is connected to remaining one of the common terminals. In addition, one of the selection terminals is connected to transmission amplifier circuit  10 , and remaining one of the selection terminals is connected to transmission amplifier circuit  20 . In this connection configuration, switch  41  switches connection of the one of the common terminals between the one of the selection terminals and the remaining one of the selection terminals, and switches connection of the remaining one of the common terminals between the one of the selection terminals and the remaining one of the selection terminals. 
     In this case, for example, a transmission signal of communication band A or B is input through the first transmission input terminal, and a transmission signal of communication band C is input through the second transmission input terminal. In addition, for example, a transmission signal of 4G is input through the first transmission input terminal, and a transmission signal of 5G is input through the second transmission input terminal. 
     Switch  42  includes common terminals  42   a  and  42   b , and selection terminals  42   c ,  42   d , and  42   e . Common terminal  42   a  is connected to output terminal  116  of transmission amplifier circuit  10 , and common terminal  42   b  is connected to output terminal  126  of transmission amplifier circuit  20 . Selection terminal  42   c  is connected to transmission filter  61 T, selection terminal  42   d  is connected to transmission filter  62 T, and selection terminal  42   e  is connected to transmission filter  63 T. Switch  42  is disposed on the output terminal side of transmission amplifier circuits  10  and  20 . In the above-described connection configuration, switch  42  switches connection of transmission amplifier circuit  10  between transmission filter  61 T and transmission filter  62 T, and connects and disconnects transmission amplifier circuit  20  and transmission filter  63 T. Switch  42  is implemented as, for example, a double pole triple throw (DP3T) switching circuit. 
     It should be noted that switch  42  may include: a SPDT switch including common terminal  42   a  and selection terminals  42   c  and  42   d ; and a single pole single throw (SPST) switch including common terminal  42   b  and selection terminal  42   e.    
     Switch  43  includes common terminal  43   a  and selection terminals  43   b ,  43   c , and  43   d . Common terminal  43   a  is connected to an input terminal of low noise amplifier  30  via matching circuit  54 . Selection terminal  43   b  is connected to reception filter  61 R, selection terminal  43   c  is connected to reception filter  62 R, and selection terminal  43   d  is connected to reception filter  63 R. In the above-described connection configuration, switch  43  connects and disconnects low noise amplifier  30  and reception filter  61 R, connects and disconnects low noise amplifier  30  and reception filter  62 R, and connects and disconnects low noise amplifier  30  and reception filter  63 R. Switch  43  is implemented as, for example, a single pole triple throw (SP3T) switching circuit. 
     Switch  44  is one example of an antenna switch, and connected to antenna connection terminal  100 . Switch  44  switches connection of antenna connection terminal  100  between (1) transmission path AT and reception path AR, (2) transmission path BT and reception path BR, and (3) transmission path CT and reception path CR. It should be noted that switch  44  is implemented as a multiple-connection switching circuit capable of simultaneously performing the connection of antenna connection terminal  100  with two or more of the above-described (1) to (3). 
     It should be noted that the above-described transmission filters  61 T to  63 T and reception filters  61 R to  63 R may be each, for example, one of an acoustic wave filter using a surface acoustic wave (SAW), an acoustic wave filter using a bulk acoustic wave (BAW), an LC resonant filter, and a dielectric filter, but not limited to these filters. 
     It should be noted that matching circuits  51  to  54  are not indispensable components for the radio frequency module according to the present disclosure. 
     In addition, a matching circuit may be disposed between transmission amplifier circuit  10  and switch  42 , and between transmission amplifier circuit  20  and switch  42 . In addition, a diplexer, a coupler, or the like may be disposed between antenna connection terminal  100  and switch  44 . 
     According to the configuration of radio frequency module  1 , transmission amplifier circuit  10 , switch  42 , transmission filter  61 T, matching circuit  51 , and switch  44  are included in a first transmission circuit that transfers a transmission signal of communication band A to antenna connection terminal  100 . Switch  44 , matching circuit  51 , reception filter  61 R, switch  43 , matching circuit  54 , and low noise amplifier  30  are included in a first reception circuit that transfers a reception signal of communication band A that has been received from antenna  2  via antenna connection terminal  100 . 
     In addition, transmission amplifier circuit  10 , switch  42 , transmission filter  62 T, matching circuit  52 , and switch  44  are included in a second transmission circuit that transfers a transmission signal of communication band B to antenna connection terminal  100 . Switch  44 , matching circuit  52 , reception filter  62 R, switch  43 , matching circuit  54 , and low noise amplifier  30  are included in a second reception circuit that transfers a reception signal of communication band B that has been received from antenna  2  via antenna connection terminal  100 . 
     In addition, transmission amplifier circuit  20 , switch  42 , transmission filter  63 T, matching circuit  53 , and switch  44  are included in a third transmission circuit that transfers a transmission signal of communication band C to antenna connection terminal  100 . Switch  44 , matching circuit  53 , reception filter  63 R, switch  43 , matching circuit  54 , and low noise amplifier  30  are included in a third reception circuit that transfers a reception signal of communication band C that has been received from antenna  2  via antenna connection terminal  100 . 
     According to the above-described circuit configuration, radio frequency module  1  is capable of at least one of transmitting, receiving, or transmitting and receiving a radio frequency signal of any one of communication band A, communication band B, and communication band C. Radio frequency module  1  is also capable of at least one of simultaneously transmitting, simultaneously receiving, or simultaneously transmitting and receiving a radio frequency signal of any one of communication band A, communication band B, and communication band C. 
     It should be noted that, the radio frequency module according to the present disclosure may be implemented without connecting the above-described three transmission circuits and the above-described three reception circuits to antenna connection terminal  100  via switch  44 , and the above-described three transmission circuits and the above-described three reception circuits may be connected to antenna  2  via different terminals. It is sufficient if the radio frequency module according to the present disclosure includes PA control circuit  80 , the first transmission circuit, and the third transmission circuit. 
     In addition, in the radio frequency module according to the present disclosure, it is sufficient if the first transmission circuit includes transmission amplifier circuit  10 . In addition, it is sufficient if the third transmission circuit includes transmission amplifier circuit  20 . 
     In addition, low noise amplifier  30  and at least one of switches  41  to  44  may be disposed in a single semiconductor IC. The semiconductor IC is configured by, for example, a CMOS. More specifically, the semiconductor IC is fabricated by SOI processing. This allows manufacturing the semiconductor IC at a low manufacturing cost. It should be noted that the semiconductor IC may include at least one of GaAs, SiGe, or GaN. With this, it is possible to output a radio frequency signal having a high-quality amplification performance and noise performance. 
       FIG. 2  is a diagram illustrating a circuit configuration of transmission amplifier circuit  10  according to the embodiment. As illustrated in the diagram, transmission amplifier circuit  10  includes: input terminal  115 ; output terminal  116 ; amplifying element  11  (a pre-stage amplifying element); amplifying element  12  (a first amplifying element); amplifying element  13  (a second amplifying element); interstage transformer  14  (a transformer); capacitor  16 ; and output transformer (balun: balanced-unbalanced transforming element)  15 . Amplifying elements  11  to  13 , interstage transformer  14 , and capacitor  16  are included in power amplifier  10 A. Power amplifier  10 A is one example of a first power amplifier. 
     Interstage transformer  14  includes primary coil  14   a  and secondary coil  14   b.    
     Amplifying element  11  includes an input terminal connected to input terminal  115 , and an output terminal connected to an unbalanced terminal of interstage transformer  14 . One of balanced terminals of interstage transformer  14  is connected to an input terminal of amplifying element  12 , and a remaining one of the balanced terminals of interstage transformer  14  is connected to an input terminal of amplifying element  13 . 
     A radio frequency signal input through input terminal  115  is amplified by amplifying element  11  in a state in which bias voltage Vcc 1  is applied to amplifying element  11 . The radio frequency signal that has been amplified is subjected to balanced-unbalanced transformation by interstage transformer  14 . At this time, a non-inverted input signal is output from the one of the balanced terminals of interstage transformer  14 , and an inverted input signal is output from the remaining one of the balanced terminals of interstage transformer  14 . 
     Output transformer  15  is one example of a first output transformer, and includes primary coil (a first coil)  15   a  and secondary coil (a second coil)  15   b . Primary coil  15   a  has one end connected to an output terminal of amplifying element  12 , and the other end connected to an output terminal of amplifying element  13 . In addition, bias voltage Vcc 2  is supplied to the midpoint of primary coil  15   a . Secondary coil  15   b  has one end connected to output terminal  116 , and the other end connected to the ground. In other words, output transformer  15  is connected between the output terminals of amplifying elements  12  and  13  and output terminal  116 . 
     Capacitor  16  is connected between the output terminal of amplifying element  12  and the output terminal of amplifying element  13 . 
     The non-inverted input signal amplified by amplifying element  12  and the inverted input signal amplified by amplifying element  13  are impedance transformed by output transformer  15  and capacitor  16  while being maintained in antiphase. In other words, the output impedance of power amplifier  10 A at output terminal  116  is matched with the input impedance of switch  42  and transmission filters  61 T and  62 T illustrated in  FIG. 1 , by output transformer  15  and capacitor  16 . It should be noted that the capacitive element connected between the ground and the path connecting output terminal  116  and secondary coil  15   b  also contributes to the above-described impedance matching. The above-described capacitive element may be disposed in series on the path connecting output terminal  116  and secondary coil  15   b , or the above-described capacitive element need not necessarily be included. 
     Here, amplifying elements  11  to  13 , interstage transformer  14 , and capacitor  16  are included in power amplifier  10 A. In particular, amplifying elements  11  to  13  and interstage transformer  14  are often integrally formed as one chip, or on the same board. In contrast, output transformer  15  requires a high Q-factor to handle a high-power transmission signal, and thus is not integrally formed with, for example, amplifying elements  11  to  13  and interstage transformer  14 . In other words, among the circuit components included in transmission amplifier circuit  10 , the circuit components other than output transformer  15  are included in power amplifier  10 A. 
     It should be noted that amplifying element  11  and capacitor  16  need not necessarily be included in power amplifier  10 A. 
     According to the circuit configuration of transmission amplifier circuit  10 , amplifying elements  12  and  13  operate in antiphase. Here, fundamental-wave currents from amplifying elements  12  and amplifying element  13  flow in antiphase; that is, in opposite directions. Accordingly, a fundamental-wave current does not flow into a ground line or a power supply line located at a substantially equal distance from amplifying elements  12  and  13 . In view of the above, the inflow of an unnecessary current to the above-described lines is negligible. It is thus possible to inhibit a decrease in power gain that is found in conventional transmission amplifier circuits. In addition, since the non-inverted signal and the inverted signal amplified by amplifying elements  12  and  13  are combined, noise components superimposed equally on both of the signals can be canceled, and thus it is possible to reduce spurious waves such as harmonic components. 
     It should be noted that amplifying element  11  is not an indispensable component for transmission amplifier circuit  10 . An element that transforms unbalanced input signals to non-inverted input signals and inverted input signals is not limited to interstage transformer  14 . Capacitor  16  is not an indispensable component for performing impedance matching. 
     In addition, although not illustrated in the diagrams, transmission amplifier circuit  20  has a circuit configuration equivalent to the circuit configuration of transmission amplifier circuit  10  illustrated in  FIG. 2 . More specifically, transmission amplifier circuit  20  includes: input terminal  125 ; output terminal  126 ; amplifying element  21  (a pre-stage amplifying element); amplifying element  22  (a third amplifying element); amplifying element  23  (a fourth amplifying element); interstage transformer (a transformer)  24 ; capacitor  26 ; and output transformer (balun: balanced-unbalanced transforming element)  25 . Amplifying elements  21  to  23 , interstage transformer  24 , and capacitor  26  are included in power amplifier  20 A. Power amplifier  20 A is one example of a second power amplifier. 
     Interstage transformer  24  includes primary coil  24   a  and secondary coil  24   b.    
     Amplifying element  21  includes an input terminal connected to input terminal  125 , and an output terminal connected to an unbalanced terminal of interstage transformer  24 . One of balanced terminals of interstage transformer  24  is connected to an input terminal of amplifying element  22 , and a remaining one of the balanced terminals of interstage transformer  24  is connected to an input terminal of amplifying element  23 . 
     Output transformer  25  is one example of a second output transformer, and includes primary coil (a third coil)  25   a  and secondary coil (a fourth coil)  25   b . Primary coil  25   a  has one end connected to an output terminal of amplifying element  22 , and the other end connected to an output terminal of amplifying element  23 . In addition, bias voltage Vcc 2  is supplied to the midpoint of primary coil  25   a . Secondary coil  25   b  has one end connected to output terminal  126 , and the other end connected to the ground. In other words, output transformer  25  is connected between the output terminals of amplifying elements  22  and  23  and output terminal  126 . 
     Capacitor  26  is connected between the output terminal of amplifying element  22  and the output terminal of amplifying element  23 . 
     Here, amplifying elements  21  to  23 , interstage transformer  24 , and capacitor  26  are included in power amplifier  20 A. In particular, amplifying elements  21  to  23  and interstage transformer  24  are often integrally formed as one chip, or on the same board. In contrast, output transformer  25  is not integrally formed with amplifying elements  21  to  23  and interstage transformer  24 , for example. 
     It should be noted that amplifying element  21  and capacitor  26  need not necessarily be included in power amplifier  20 A. 
     According to the circuit configuration of transmission amplifier circuit  20 , it is possible to inhibit decrease in power gain that is found in conventional transmission amplifier circuits. In addition, since the non-inverted signal and the inverted signal amplified by amplifying elements  22  and  23  are combined, noise components superimposed equally on both of the signals can be canceled, and thus it is possible to reduce spurious waves such as harmonic components. 
     It should be noted that amplifying element  21  is not an indispensable component for transmission amplifier circuit  20 . An element that transforms unbalanced input signals to non-inverted input signals and inverted input signals is not limited to interstage transformer  24 . Capacitor  26  is not an indispensable component for performing impedance matching. 
     Amplifying elements  11  to  13  and  21  to  23  and low noise amplifier  30  include, for example, a field-effect transistor (FET), a hetero-junction bipolar transistor (HBT), etc. which include a Si complementary metal oxide semiconductor (CMOS) or GaAs as a material. 
     It should be noted that transmission amplifier circuit  10  need not necessarily include differential power amplifier  10 A, and may be an amplifier that includes a so-called single-end amplifying element which receives an unbalanced signal and outputs an unbalanced signal. In addition, transmission amplifier circuit  20  need not necessarily include differential power amplifier  20 A, and may be an amplifier that includes a so-called single-end amplifying element which receives an unbalanced signal and outputs an unbalanced signal. 
     Here, in radio frequency module  1 , transmission amplifier circuit  10  amplifies transmission signals of communication bands A and B, and transmission amplifier circuit  20  amplifies transmission signals of communication band C. In other words, the amplification performance of each of transmission amplifier circuits  10  and  20  is optimized in a specific frequency band (communication band), and thus radio frequency module  1  need to include a plurality of transmission amplifier circuits that support the respective frequency bands (communication bands). In addition, under the condition that radio frequency module  1  is mounted on a single mounting board, since a large number of circuit elements (amplifying elements  11  to and  21  to  23 , interstage transformers  14  and  24 , output transformers  15  and  25 , and capacitors  16  and  26 ) are included in transmission amplifier circuits  10  and  20 , radio frequency module  1  increases in size. 
     Furthermore, if the circuit elements are highly-densely mounted in order to reduce the size of radio frequency module  1 , high-power transmission signals output from output transformers  15  and  25  interfere with each other. As a result, there arises a problem of degradation of the signal quality of the transmission signals. 
     In view of the above, the following describes a configuration of radio frequency module  1  whose size is reduced while quality degradation of the transmission signals output from radio frequency module  1  is inhibited. 
     2. Arrangement Configuration of Circuit Elements of Radio Frequency Module  1 A According to Working Example 1 
       FIG. 3A  is a schematic diagram illustrating a plan view configuration of radio frequency module  1 A according to Working Example 1.  FIG. 3B  is a schematic diagram illustrating a cross-sectional configuration of radio frequency module  1 A according to Working Example 1. More specifically,  FIG. 3B  is a cross-sectional view taken along line IIIB-IIIB of  FIG. 3A . It should be noted that (a) in  FIG. 3A  illustrates a layout of the circuit elements when, of principal surfaces  91   a  and  91   b  located on opposite sides of module board  91 , principal surface  91   a  is viewed from the z-axis positive side. Meanwhile, (b) in  FIG. 3A  illustrates a perspective view of the layout of the circuit elements when principal surface  91   b  is viewed from the z-axis positive side. In  FIG. 3A , output transformers  15  and  25  formed in module board  91  are indicated by broken lines. 
     Radio frequency module  1 A according to Working Example 1 specifically illustrates the arrangement configuration of the respective circuit elements included in radio frequency module  1  according to the embodiment. 
     As illustrated in  FIG. 3A  and  FIG. 3B , radio frequency module  1 A according to the present working example further includes module board  91 , resin components  92  and  93 , and external-connection terminals  150  in addition to the circuit configuration illustrated in  FIG. 1 . 
     Module board  91  is a board which includes principal surface  91   a  (a first principal surface) and principal surface  91   b  (a second principal surface) on opposite sides thereof, and on which the above-described transmission circuit and the above-described reception circuit are mounted. As module board  91 , for example, a low temperature co-fired ceramic (LTCC) board having a stacked structure including a plurality of dielectric layers, a high temperature co-fired ceramic (HTCC) board, a component built-in board, a board including a redistribution layer (RDL), or a printed board or the like is used. 
     Resin component  92  is disposed on principal surface  91   a  of module board  91  and covers a portion of the above-described transmission circuit, a portion of the above-described reception circuit, and principal surface  91   a  of module board  91 . Resin component  92  has a function of ensuring reliability such as mechanical strength and moisture resistance of the circuit elements included in the above-described transmission circuit and the above-described reception circuit. Resin component  93  is disposed on principal surface  91   b  of module board  91  and covers a portion of the above-described transmission circuit, a portion of the above-described reception circuit, and principal surface  91   b  of module board  91 . Resin component  93  has a function of ensuring reliability such as mechanical strength and moisture resistance of the circuit elements included in the above-described transmission circuit and the above-described reception circuit. It should be noted that resin components  92  and  93  are not indispensable components for the radio frequency module according to the present disclosure. 
     As illustrated in  FIG. 3A  and  FIG. 3B , in radio frequency module  1 A according to the present working example, power amplifiers  10 A and  20 A, duplexers  61 ,  62 , and  63 , and matching circuits  51 ,  52 ,  53 , and  54  are disposed on principal surface  91   a  (a first principal surface) of module board  91 . PA control circuit  80 , low noise amplifier  30 , switches  41 ,  42 ,  43 , and  44  are each one example of the first circuit components, and disposed on principal surface  91   b  (a second principal surface) of module board  91 . Output transformers  15  and  25  are provided inside module board  91 . 
     In other words, according to the present working example, power amplifiers  10 A and  20 A are disposed on principal surface  91   a , and output transformers  15  and  25  are formed inside module board  91 . 
     According to the above-described configuration, it is possible to reduce the size of radio frequency module  1 A compared to the configuration in which power amplifiers  10 A and  20 A and output transformers  15  and  25  are all disposed on one surface of module board  91 . Accordingly, it is possible to provide small-sized radio frequency module  1 A that includes a differential power amplifier, and supports multi-band technologies. 
     It should be noted that, although not illustrated in  FIG. 3A , lines included in transmission paths AT, BT, and CT, and reception paths AR, BR, and CR illustrated in  FIG. 1  are provided inside module board  91  and on principal surfaces  91   a  and  91   b . In addition, each of the above-described lines may be a bonding wire having ends bonded to principal surfaces  91   a  and  91   b  and any of the circuit elements included in radio frequency module  1 A, or may be a terminal, an electrode, or a line disposed on a surface of any of the circuit elements included in radio frequency module  1 A. 
     Power amplifier  10 A is one example of a first power amplifier that amplifies a transmission signal of a first frequency band including communication bands A and B. Power amplifier  20 A is one example of a second power amplifier that amplifies a transmission signal of a second frequency band including communication band C. According to the present working example, the first frequency band (communication bands A and B) is lower than the second frequency band (communication band C). 
     In addition, in radio frequency module  1 A according to the present working example, in a plan view of module board  91 , output transformer  15  is disposed in region  153  (a first region) adjacent to outer side  103  (a first outer side) among four outer sides  101 ,  102 ,  103 , and  104  that define a first quadrilateral region in which power amplifier  10 A is disposed, as illustrated in (a) in  FIG. 3A . Output transformer  25  is disposed in region  254  (a second region) adjacent to outer side  204  (a second outer side) among four outer sides  201 ,  202 ,  203 , and  204  that define a second quadrilateral region in which power amplifier  20 A is disposed. Here, outer side  103  is, among the four outer sides  101 ,  102 ,  103 , and  104 , one of the sides other than outer side  101  that is closest to the second quadrilateral region in which power amplifier  20 A is disposed. Outer side  204  is, among the four outer sides  201 ,  202 ,  203 , and  204 , one of the sides other than outer side  201  that is closest to the first quadrilateral region in which power amplifier  10 A is disposed. 
     It should be noted that, in the configuration of radio frequency module  1 A according to the present working example in which output transformer  15  is disposed in the first region adjacent to the first outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the first outer side and output transformer  15 . In addition, in the configuration in which output transformer  25  is disposed in the second region adjacent to the second outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the second outer side and output transformer  25 . 
     According to the above-described configuration of radio frequency module  1 A according to the present working example, output transformer  15  that transfers a high-power transmission signal from power amplifier  10 A is not disposed in the region adjacent to outer side  101  that is closest to power amplifier  20 A. In addition, output transformer  25  that transfers a high-power transmission signal from power amplifier  20 A is not disposed in the region adjacent to outer side  201  that is closest to power amplifier  10 A. With this configuration, it is possible to avoid output transformer  15  and output transformer  25  from being put in a nearest-neighbor relationship. Accordingly, it is possible to inhibit high-power transmission signals output from power amplifiers  10 A and  20 A from interfering with each other. As a result, degradation of the signal quality of the transmission signals can be reduced. 
     In addition, power amplifier  10 A includes at least amplifying elements  12  and  13 , and power amplifier  20 A includes at least amplifying elements  22  and  23 . Accordingly, there are a large number of circuit elements. As a result, the mounting area of radio frequency module  1 A tends to be large. In contrast, in radio frequency module  1 A according to the present working example, power amplifiers  10 A and  20 A and the first circuit components such as PA control circuit  80 , low noise amplifier  30 , and switches  41 ,  42 ,  43 , and  44  are disposed separately on principal surface  91   a  and principal surface  91   b  of module board  91 . As a result, it is possible to further miniaturize radio frequency module  1 A. 
     It should be noted that radio frequency module  1  according to the present disclosure is not limited to the arrangement relation of output transformers  15  and  25  in radio frequency module  1 A according to Working Example 1. 
       FIG. 4A  is a schematic diagram illustrating a plan view configuration on principal surface  91   a  of radio frequency module  1 C according to Variation  1 . In the diagram, a layout of the circuit elements when, of principal surfaces  91   a  and  91   b  located on opposite sides of module board  91 , principal surface  91   a  is viewed from the z-axis positive side is illustrated. In addition, in the diagram, output transformers  15  and  25  formed in module board  91  are indicated by broken lines. 
     In radio frequency module  1 C according to the present variation, in a plan view of module board  91 , output transformer  15  is disposed in region  153  (a first region) adjacent to outer side  103  (a first outer side) among four outer sides  101 ,  102 ,  103 , and  104  that define a first quadrilateral region in which power amplifier  10 A is disposed, as illustrated in  FIG. 4A . Output transformer  25  is disposed in region  253  (a second region) adjacent to outer side  203  (a second outer side) among four outer sides  201 ,  202 ,  203 , and  204  that define a second quadrilateral region in which power amplifier  20 A is disposed. Here, outer side  103  is, among the four outer sides  101 ,  102 ,  103 , and  104 , one of the sides other than outer side  101  that is closest to the second quadrilateral region in which power amplifier  20 A is disposed. Outer side  203  is, among the four outer sides  201 ,  202 ,  203 , and  204 , one of the sides other than outer side  201  that is closest to the first quadrilateral region in which power amplifier  10 A is disposed. 
     It should be noted that, in radio frequency module  1 C according to Variation  1 , in a plan view of module board  91 , output transformer  15  may be disposed in region  154  (a first region) adjacent to outer side  104  (a first outer side) among the four outer sides  101 ,  102 ,  103 , and  104  that define the first quadrilateral region in which power amplifier  10 A is disposed. 
     According to the above-described configuration of radio frequency module  1 C according to the present variation, output transformer  15  that transfers a high-power transmission signal from power amplifier  10 A is not disposed in the region adjacent to outer side  101  that is closest to power amplifier  20 A. In addition, output transformer  25  that transfers a high-power transmission signal from power amplifier  20 A is not disposed in the region adjacent to outer side  201  that is closest to power amplifier  10 A. With this configuration, it is possible to avoid output transformer  15  and output transformer  25  from being put in a nearest-neighbor relationship. Accordingly, it is possible to inhibit high-power transmission signals output from power amplifiers  10 A and  20 A from interfering with each other. As a result, degradation of the signal quality of the transmission signals can be reduced. 
       FIG. 4B  is a schematic diagram illustrating a plan view configuration on principal surface  91   a  of radio frequency module  1 D according to Variation  2 . In the diagram, a layout of the circuit elements when, of principal surfaces  91   a  and  91   b  located on opposite sides of module board  91 , principal surface  91   a  is viewed from the z-axis positive side is illustrated. In addition, in the diagram, output transformers  15  and  25  formed in module board  91  are indicated by broken lines. 
     In radio frequency module  1 D according to the present variation, in a plan view of module board  91 , output transformer  15  is disposed in region  156  (a fourth region) adjacent to outer side  104  (a first outer side) among four outer sides  101 ,  102 ,  103 , and  104  that define a first quadrilateral region in which power amplifier  10 A is disposed, as illustrated in  FIG. 4B . Output transformer  25  is disposed in region  256  (a sixth region) adjacent to outer side  204  (a second outer side) among four outer sides  201 ,  202 ,  203 , and  204  that define a second quadrilateral region in which power amplifier  20 A is disposed. Here, outer side  104  is, among the four outer sides  101 ,  102 ,  103 , and  104 , one of sides other than outer side  101  that is closest to the second quadrilateral region in which power amplifier  20 A is disposed. Outer side  204  is, among the four outer sides  201 ,  202 ,  203 , and  204 , one of sides other than outer side  201  that is closest to the first quadrilateral region in which power amplifier  10 A is disposed. In addition, the first region adjacent to outer side  104  (the first outer side) among outer sides  101 ,  102 ,  103 , and  104  includes region  155  (a third region) adjacent to outer side  104  (the first outer side) and region  156  (the fourth region) that is located further away from the second quadrilateral region than region  155 . In addition, the second region adjacent to outer side  204  among outer sides  201 ,  202 ,  203 , and  204  includes region  255  (a fifth region) adjacent to outer side  204  (the second outer side) and region  256  (the sixth region) that is located further away from the first quadrilateral region than region  255 . 
     According to the above-described configuration of radio frequency module  1 D according to the present variation, output transformer  15  is not disposed in the region adjacent to outer side  101  that is closest to power amplifier  20 A, but disposed in, of the two regions adjacent to outer side  104 , region  156  that is located further away from power amplifier  20 A. Output transformer  25  is not disposed in the region adjacent to outer side  201  that is closest to power amplifier  10 A, but disposed in, of the two regions adjacent to outer side  204 , region  256  that is located further away from power amplifier  10 A. With this configuration, it is possible to avoid output transformer  15  and output transformer  25  from being put in a nearest-neighbor relationship. Accordingly, it is possible to inhibit high-power transmission signals output from power amplifiers  10 A and  20 A from interfering with each other. As a result, degradation of the signal quality of the transmission signals can be reduced. 
     It should be noted that, in the configurations of radio frequency modules  1 A and  1 C in which output transformer  15  is disposed in the first region adjacent to the first outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the first outer side and output transformer  15 . In addition, in the configuration in which output transformer  25  is disposed in the second region adjacent to the second outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the second outer side and output transformer  25 . 
     In addition, in the configuration of radio frequency module  1 D in which output transformer  15  is disposed in the fourth region adjacent to the first outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the first outer side and output transformer  15 . In addition, in the configuration in which output transformer  25  is disposed in the sixth region adjacent to the second outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the second outer side and output transformer  25 . 
     Returning again to  FIG. 3A  and  FIG. 3B , in radio frequency module  1 A according to the present working example, a plurality of external-connection terminals  150  are disposed on the principal surface  91   b  (the second principal surface) side of module board  91 . Radio frequency module  1 A exchanges electrical signals with a motherboard disposed on the z-axis negative side of radio frequency module  1 A via the plurality of external-connection terminals  150 . As illustrated in (b) in  FIG. 3A , the plurality of external-connection terminals include: antenna connection terminal  100 ; transmission input terminals  111 ,  112 ,  121 , and  122 ; reception output terminal  130 ; and control signal terminal  140 . In addition, one or more of the plurality of external-connection terminals  150  are set to ground potential of the motherboard. Of principal surfaces  91   a  and  91   b , power amplifiers  10 A and  20 A which are difficult to reduce the height are not disposed on principal surface  91   b  facing the motherboard, but low noise amplifier  30 , PA control circuit  80 , and switches  41  o  44  which are easy to reduce the height are disposed on principal surface  91   b . Accordingly, it is possible to reduce the height of radio frequency module  1 A as a whole. 
     Power amplifiers  10 A and  20 A are components that generate a large amount of heat among the circuit components included in radio frequency module  1 A. In order to improve the heat dissipation property of radio frequency module  1 A, it is important to dissipate heat generated by power amplifiers  10 A and  20 A to the motherboard through a heat dissipation path having a small thermal resistance. If power amplifiers  10 A and  20 A are mounted on principal surface  91   b , the electrode lines connected to power amplifiers  10 A and  20 A are disposed on principal surface  91   b . For that reason, as the heat dissipation path, a heat dissipation path that passes though only a planar line pattern (along the xy plane direction) on principal surface  91   b  is included. The above-described planar line pattern is formed using a metal thin film, and thus has a large thermal resistance. For that reason, when power amplifiers  10 A and  20 A are disposed on principal surface  91   b , the heat dissipation property is decreased. 
     In contrast, in the case where power amplifiers  10 A and  20 A are disposed on principal surface  91   a  as in the present working example, it is possible to connect power amplifiers  10 A and  20 A to external-connection terminals  150  via penetrating electrodes that penetrates through module board  91  between principal surface  91   a  and principal surface  91   b . As a result, it is possible to exclude a heat dissipation path that passes through only the planar line pattern along the xy plane direction which has a large thermal resistance, from among the lines in module board  91 , as the heat dissipation paths for power amplifiers  10 A and  20 A. It is thus possible to provide radio frequency module  1 A having an improved heat dissipation property for dissipating heat from power amplifiers  10 A and  20 A to the motherboard. 
     In addition, in radio frequency module  1 A, power amplifier  10 A and power amplifier  20 A may be included in a single first semiconductor IC. 
     According to this configuration, it is possible to inhibit degradation of the signal quality of transmission signals, while reducing the size of the transmission amplifier circuit. 
     In addition, as illustrated in  FIG. 3A , it is desirable that a footprint of PA control circuit  80  does not overlap a footprint of output transformer  15  or a footprint of output transformer  25  in radio frequency module  1 A. 
     According to this configuration, PA control circuit  80  that inputs/outputs digital control signals and output transformers  15  and  25  are disposed with module board  91  interposed therebetween, and a sufficient distance is ensured between PA control circuit  80  and output transformers  15  and  25 . As a result, it is possible to inhibit output transformers  15  and  25  from being affected by a digital noise. It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     In addition, as illustrated in  FIG. 3A , it is desirable that a footprint of switch  42  does not overlap the footprint of output transformer  15  or the footprint of output transformer  25  in radio frequency module  1 A. 
     According to this configuration, it is possible to inhibit transmission signals output from output transformers  15  and  25  from leaking to an unconnected transmission or reception path via the off-capacitance of switch  42 . It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     In addition, as illustrated in  FIG. 3A , it is desirable that a footprint of switch  41  does not overlap the footprint of output transformer  15  or the footprint of output transformer  25  in radio frequency module  1 A. 
     According to this configuration, it is possible to inhibit transmission signals input through the transmission input terminal from leaking to an unconnected output transformer via the off-capacitance of switch  41 . It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     As illustrated in  FIG. 3A , PA control circuit  80 , switch  41 , and switch  42  may be included in a single semiconductor IC  70  in radio frequency module  1 A. 
     According to this configuration, PA control circuit  80 , switch  41 , and switch  42  are located in proximity to one another, and thus it is possible to miniaturize radio frequency module  1 A. Furthermore, since the control line that connects PA control circuit  80  and switch  41  and the control line that connects PA control circuit  80  and switch  42  can be shortened, it is possible to inhibit noise generation from the control lines. 
     In radio frequency module  1 A according to the present working example, low noise amplifier  30  and switches  43  and  44  are included in a single semiconductor IC  75 , and the single semiconductor IC  75  is disposed on principal surface  91   b.    
     According to this configuration, low noise amplifier  30 , switch  43 , and switch  44  disposed on the reception path are located in proximity to one another, and thus it is possible to miniaturize radio frequency module  1 A. 
     It should be noted that semiconductor IC  75  may not include at least one of switch  43  or switch  44 . 
     As illustrated in  FIG. 3A , in a plan view of module board  91 , it is desirable that footprints of output transformers  15  and  25  do not overlap a footprint of semiconductor IC  70 . 
     According to this configuration, it is possible to: inhibit output transformers  15  and  25  from being affected by a digital noise; inhibit transmission signals output from output transformers  15  and  25  from leaking to an unconnected transmission or reception path via the off-capacitance of switch  42 ; or inhibit transmission signals input through the transmission input terminal from leaking to an unconnected output transformer via the off-capacitance of switch  41 . It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     In radio frequency module  1 A according to the present working example, power amplifiers  10 A and  20 A are disposed on principal surface  91   a , and low noise amplifier  30  is disposed on principal surface  91   b . According to this configuration, power amplifiers  10 A and  20 A that amplify transmission signals and low noise amplifier  30  that amplifies reception signals are separately disposed on different sides of module board  91 , and thus it is possible to improve isolation between a transmission side and a reception side. 
     As illustrated in  FIG. 3A  and  FIG. 3B , in a plan view of module board  91 , external-connection terminals  150  set to ground potential are disposed between low noise amplifier  30  and output transformers  15  and  25 . 
     According to this configuration, the plurality of external-connection terminals  150  which are applied as ground electrodes are disposed between low noise amplifier  30  that significantly affects the reception sensitivity of the reception circuit and output transformers  15  and  25  that transfer high-power transmission signals. Accordingly, it is possible to inhibit degradation of reception sensitivity due to an inflow of a transmission signal and harmonic of the transmission signal to the reception path. 
     It should be noted that, although duplexers  61  to  63  and matching circuits  51  to  54  are mounted on principal surface  91   a  (the first principal surface), duplexers  61  to  63  and matching circuits  51  to  54  may be mounted on principal surface  91   b  (the second principal surface). In addition, although low noise amplifier  30 , PA control circuit  80 , and switches  41  to  44  are mounted on principal surface  91   b  (the second principal surface), low noise amplifier  30 , PA control circuit  80 , and switches  41  to  44  may be mounted on principal surface  91   a  (the first principal surface). 
     It is desirable that module board  91  have a multilayer structure in which a plurality of dielectric layers are laminated, and that a ground electrode pattern be formed in at least one of the plurality of dielectric layers. According to this configuration, the electromagnetic field shielding function of module board  91  is improved. 
     In addition, output transformers  15  and  25  are provided inside module board  91  in radio frequency module  1 A according to the present working example. In this case, the inductors included in output transformers  15  and  25  are planar coils implemented by electric conduction patterns of module board  91 , for example. In such arrangement configuration of output transformers  15  and  25 , it is desirable that footprints of power amplifiers  10 A and  20 A each do not overlap the footprint of output transformer  15  or the footprint of output transformer  25  in a plan view of module board  91 . 
     Output transformers  15  and  25  each require a high Q-factor to handle a high-power transmission signal. Accordingly, it is desirable to avoid a change in magnetic fields formed by output transformers  15  and  25  due to power amplifiers  10 A and  20 A being located in proximity to output transformers  15  and  25 . Power amplifiers  10 A and  20 A are not disposed in the above-described region where the footprints of power amplifiers  10 A and  20 A overlap the footprints of output transformers  15  and  25 , and thus it is possible to maintain a high Q-factor of each of the inductors included in output transformers  15  and  25 . 
     In radio frequency module  1 A according to the present working example, it is desirable that circuit components be not disposed in a region on principal surface  91   a  and principal surface  91   b  where circuit components overlap the footprints of output transformers  15  and  25  in a plan view of module board  91 . 
     Output transformers  15  and  25  each require a high Q-factor to handle a high-power transmission signal. Accordingly, it is desirable to avoid a change in magnetic fields formed by output transformers  15  and  25  due to the other circuit components being located in proximity to output transformers  15  and  25 . Since no circuit component is disposed in the above-described region, it is possible to maintain a high Q-factor of each of the inductors included in output transformers  15  and  25 . 
     Formation regions of output transformers  15  and  25  in which output transformers  15  and  25  are formed are defined as follows. The following describes a formation region of output transformer  15 . Since a formation region of output transformer  25  is defined similarly to the definition of the formation region of output transformer  15 , the following description omits the definition of the formation region of output transformer  25 . 
     The formation region of output transformer  15  is a minimum region that includes a formation region in which primary coil  15   a  is formed and a formation region in which secondary coil  15   b  is formed, in a plan view of module board  91 . 
     Here, secondary coil  15   b  is defined as a line conductor disposed along primary coil  15   a  and located at a first distance, which is substantially constant, from primary coil  15   a . In this case, a second distance that is a distance from each end of the line conductor to primary coil  15   a  is greater than the first distance. An end and another end of secondary coil  15   b  are points at which the distance from the line conductor to primary coil  15   a  starts to change. Primary coil  15   a  is defined as a line conductor disposed along secondary coil  15   b  and located at a first distance, which is substantially constant, from secondary coil  15   b . In this case, a second distance that is a distance from each end of the line conductor to secondary coil  15   b  is greater than the first distance. An end and another end of primary coil  15   a  are points at which the distance from the line conductor to secondary coil  15   b  starts to change. 
     Alternatively, secondary coil  15   b  is defined as a line conductor disposed along primary coil  15   a  and having a first line width that is substantially constant. Primary coil  15   a  is defined as a line conductor disposed along secondary coil  15   b  and having a first line width that is substantially constant. 
     Alternatively, secondary coil  15   b  is defined as a line conductor disposed along primary coil  15   a  and having a first film thickness that is substantially constant. Primary coil  15   a  is defined as a line conductor disposed along secondary coil  15   b  and having a first film thickness that is substantially constant. 
     Alternatively, secondary coil  15   b  is defined as a line conductor disposed along primary coil  15   a  and having a first degree of coupling with primary coil  15   a  that is substantially constant. Primary coil  15   a  is defined as a line conductor disposed along secondary coil  15   b  and having a first degree of coupling with secondary coil  15   b  that is substantially constant. 
     It should be noted that external-connection terminals  150  may be columnar electrodes that penetrate through resin component  93  in the z-axis direction as illustrated in  FIG. 3A  and  FIG. 3B , or may be bump electrodes  160  formed on principal surface  91   b  as in radio frequency module  1 B according to Variation  3  as illustrated in  FIG. 5 . In this case, resin component  93  need not be provided on principal surface  91   b.    
     In radio frequency module  1 A according to Working Example 1 and radio frequency modules  1 C and  1 D according to Variations  1  and  2 , external-connection terminals  150  may be disposed on principal surface  91   a . In addition, in radio frequency module  1 B according to Variation  3 , bump electrodes  160  may be disposed on principal surface  91   a.    
     3. Arrangement Configuration of Circuit Elements of Radio Frequency Module  1 E According to Working Example 2 
       FIG. 6A  is a schematic diagram illustrating a plan view configuration of radio frequency module  1 E according to Working Example 2.  FIG. 6B  is a schematic diagram illustrating a cross-sectional configuration of radio frequency module  1 E according to Variation  2 . More specifically,  FIG. 6B  is a cross-sectional view taken along line VIB-VIB of  FIG. 6A . It should be noted that (a) in  FIG. 6A  illustrates a layout of the circuit elements when, of principal surfaces  91   a  and  91   b  located on opposite sides of module board  91 , principal surface  91   a  is viewed from the z-axis positive side. Meanwhile, (b) in  FIG. 6A  illustrates a perspective view of the layout of the circuit elements when principal surface  91   b  is viewed from the z-axis positive side. 
     Radio frequency module  1 E according to Working Example 2 shows a specific arrangement of circuit elements included in radio frequency module  1  according to the embodiment. Radio frequency module  1 E is different from radio frequency module  1 A according to Working Example 1 in the arrangement of output transformers  15  and  25 . Hereinafter, radio frequency module  1 E according to Working Example 2 will be described. In the description, the same points as those of radio frequency module  1 A according to Working Example 1 will be omitted, and different points will be mainly described. 
     As illustrated in  FIG. 6A  and  FIG. 6B , in radio frequency module  1 E according to the present working example, power amplifiers  10 A and  20 A, duplexers  61 ,  62 , and  63 , and matching circuits  51 ,  52 ,  53 , and  54  are disposed on principal surface  91   a  (a first principal surface) of module board  91 . PA control circuit  80 , output transformers  15  and  25 , low noise amplifier  30 , switches  41 ,  42 ,  43 , and  44  are disposed on principal surface  91   b  (a second principal surface) of module board  91 . PA control circuit  80 , low noise amplifier  30 , and switches  41 ,  42 ,  43 , and  44  are each one example of a first circuit component. 
     In other words, according to the present working example, power amplifiers  10 A and  20 A are disposed on principal surface  91   a , and output transformers  15  and  25  are disposed on principal surface  91   b.    
     According to the above-described configuration, it is possible to reduce the size of radio frequency module  1 E compared to the configuration in which power amplifiers  10 A and  20 A and output transformers  15  and  25  are all disposed on one surface of module board  91 . Accordingly, it is possible to provide small-sized radio frequency module  1 E that includes a differential power amplifier, and supports multi-band technologies. 
     Output transformers  15  and  25  are, for example, surface mount chip elements each including a plurality of inductors. Furthermore, output transformers  15  and  25  may be, for example, integrated passive devices (IPDs) in each of which passive elements such as an inductor and the like are mounted inside of or on the surface of a Si substrate in an integrated manner. When output transformers  15  and  25  are IPDs, miniaturization of radio frequency module  1 E can be facilitated. 
     In addition, in radio frequency module  1 E according to the present working example, in a plan view of module board  91 , output transformer  15  is disposed in region  153  (a first region) adjacent to outer side  103  (a first outer side) among four outer sides  101 ,  102 ,  103 , and  104  that define a first quadrilateral region in which power amplifier  10 A is disposed, as illustrated in (a) in  FIG. 6A . Output transformer  25  is disposed in region  254  (a second region) adjacent to outer side  204  (a second outer side) among four outer sides  201 ,  202 ,  203 , and  204  that define a second quadrilateral region in which power amplifier  20 A is disposed. Here, outer side  103  is, among the four outer sides  101 ,  102 ,  103 , and  104 , one of sides other than outer side  101  that is closest to the second quadrilateral region in which power amplifier  20 A is disposed. Outer side  204  is, among the four outer sides  201 ,  202 ,  203 , and  204 , one of sides other than outer side  201  that is closest to the first quadrilateral region in which power amplifier  10 A is disposed. 
     According to the above-described configuration of radio frequency module  1 E according to the present working example, output transformer  15  that transfers a high-power transmission signal from power amplifier  10 A is not disposed in the region adjacent to outer side  101  that is closest to power amplifier  20 A. In addition, output transformer  25  that transfers a high-power transmission signal from power amplifier  20 A is not disposed in the region adjacent to outer side  201  that is closest to power amplifier  10 A. According to this configuration, it is possible to avoid output transformer  15  and output transformer  25  from being put in a nearest-neighbor relationship. Accordingly, it is possible to inhibit high-power transmission signals output from power amplifiers  10 A and  20 A from interfering with each other. As a result, degradation of the signal quality of the transmission signals can be reduced. 
     It should be noted that, in the configuration of radio frequency module  1 E in which output transformer  15  is disposed in the first region adjacent to the first outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the first outer side and output transformer  15 . In addition, in the configuration in which output transformer  25  is disposed in the second region adjacent to the second outer side, in a plan view of module board  91 , another circuit element or circuit component may be disposed between the second outer side and output transformer  25 . 
     It should be noted that radio frequency module  1  according to the present disclosure is not limited to the arrangement relation of output transformers  15  and  25  in radio frequency module  1 E according to Working Example 2. Output transformers  15  and  25  may be in the arrangement relation illustrated in  FIG. 4A  and  FIG. 4B , and may be disposed on principal surface  91   b  instead of being formed inside module board  91 . 
     In radio frequency module  1 E according to the present working example, output transformers  15  and  25  are disposed on principal surface  91   b . However, it is desirable that the footprints of power amplifiers  10 A and  20 A each do not overlap the footprint of output transformer  15  or the footprint of output transformer  25  in a plan view of module board  91 . 
     Output transformers  15  and  25  each require a high Q-factor to handle a high-power transmission signal. Accordingly, it is desirable to avoid a change in magnetic fields formed by output transformers  15  and  25  due to power amplifiers  10 A and  20 A being located in proximity to output transformers  15  and  25 . Power amplifiers  10 A and  20 A are not disposed in the above-described region where power amplifiers  10 A and  20 A overlap output transformers  15  and  25 , and thus it is possible to maintain a high Q-factor of each of the inductors included in output transformers  15  and  25 . 
     In radio frequency module  1 E according to the present working example, it is desirable that circuit components be not disposed in a region on principal surface  91   b  and a region inside module board  91  where circuit components overlap output transformers  15  and  25  in a plan view of module board  91 . 
     Output transformers  15  and  25  each require a high Q-factor to handle a high-power transmission signal. Accordingly, it is desirable to avoid a change in magnetic fields formed by output transformers  15  and  25  due to the other circuit components being located in proximity to output transformers  15  and  25 . Since no circuit component is disposed in the above-described regions, it is possible to maintain a high Q-factor of each of the inductors included in output transformers  15  and  25 . 
     3. Advantageous Effects, Etc. 
     As described above, radio frequency module  1  according to the embodiment includes module board  91  including principal surface  91   a  and principal surface  91   b  on opposite sides of module board  91 ; power amplifier  10 A configured to amplify a transmission signal of a first frequency band; power amplifier  20 A configured to amplify a transmission signal of a second frequency band different from the first frequency band; output transformer  15  including primary coil  15   a  and secondary coil  15   b ; and output transformer  25  including primary coil  25   a  and secondary coil  25   b . In radio frequency module  1 , power amplifier  10 A includes amplifying element  12  and amplifying element  13 , power amplifier  20 A includes amplifying element  22  and amplifying element  23 , one of ends of primary coil  15   a  is connected to an output terminal of amplifying element  12 , and a remaining one of the ends of primary coil  15   a  is connected to an output terminal of amplifying element  13 , one of ends of primary coil  25   a  is connected to an output terminal of amplifying element  22 , and a remaining one of the ends of primary coil  25   a  is connected to an output terminal of amplifying element  23 , power amplifier  10 A and power amplifier  20 A are disposed on principal surface  91   a , and output transformer  15  and output transformer  25  are disposed inside module board  91  or on principal surface  91   b.    
     According to this configuration, it is possible to reduce the size of radio frequency module  1  compared to the configuration in which power amplifiers  10 A and  20 A and output transformers  15  and  25  are all disposed on one surface of module board  91 . Accordingly, it is possible to provide small-sized radio frequency module  1  that includes a differential power amplifier, and supports multi-band technologies. 
     In addition, in radio frequency module  1 , in a plan view of module board  91 , output transformer  15  may be disposed in a first region adjacent to a first outer side of four outer sides  101  to  104  defining a first quadrilateral region in which power amplifier  10 A is disposed, and output transformer  25  may be disposed in a second region adjacent to a second outer side of four outer sides  201  to  204  defining a second quadrilateral region in which power amplifier  20 A is disposed. The first outer side is other than outer side  101  located closest to the second quadrilateral region among the four outer sides  101  to  104  defining the first quadrilateral region. The second outer side is other than outer side  201  located closest to the first quadrilateral region among the four outer sides  201  to  204  defining the second quadrilateral region. 
     According to this configuration, output transformer  15  that transfers a high-power transmission signal from power amplifier  10 A is not disposed in the region adjacent to outer side  101  that is closest to power amplifier  20 A. In addition, output transformer  25  that transfers a high-power transmission signal from power amplifier  20 A is not disposed in the region adjacent to outer side  201  that is closest to power amplifier  10 A. According to this configuration, it is possible to avoid output transformer  15  and output transformer  25  from being put in a nearest-neighbor relationship. Accordingly, it is possible to inhibit high-power transmission signals output from power amplifiers  10 A and  20 A from interfering with each other. As a result, degradation of the signal quality of the transmission signals can be reduced. 
     In addition, in radio frequency module  1 D, the first region may include a third region and a fourth region. The fourth region is located further away from the second quadrilateral region than the third region. The second region may include a fifth region and a sixth region. The sixth region is located further away from the first quadrilateral region than the fifth region. In a plan view of module board  91 , output transformer  15  may be disposed in the fourth region included in the first region, and output transformer  25  may be disposed in the sixth region included in the second region. 
     According to this configuration, output transformer  15  is not disposed in the region adjacent to outer side  101  that is closest to power amplifier  20 A, but disposed in, of the two regions included in the first region, the fourth region that is located further away from power amplifier  20 A. In addition, output transformer  25  is not disposed in the region adjacent to outer side  201  that is closest to power amplifier  10 A, but disposed in, of the two regions included in the second region, the sixth region that is located further away from power amplifier  10 A. According to this configuration, it is possible to avoid output transformer  15  and output transformer  25  from being put in a nearest-neighbor relationship. Accordingly, it is possible to inhibit high-power transmission signals output from power amplifiers  10 A and  20 A from interfering with each other. As a result, degradation of the signal quality of the transmission signals can be reduced. 
     In addition, radio frequency module  1  may further include a plurality of external-connection terminals  150  disposed on principal surface  91   b.    
     According to this configuration, since power amplifiers  10 A and  20 A which are difficult to reduce the height are not disposed, of principal surfaces  91   a  and  90   b , on principal surface  91   b  facing the motherboard, it is possible to reduce the height of radio frequency module  1  as a whole. 
     In addition, in radio frequency module  1 , power amplifier  10 A and power amplifier  20 A may be included in a single first semiconductor integrated circuit (IC). 
     According to this configuration, it is possible to inhibit degradation of the signal quality of transmission signals, while reducing the size of the transmission amplifier circuit. 
     In addition, radio frequency module  1  may further include PA control circuit  80  configured to control power amplifier  10 A and power amplifier  20 A. In radio frequency module  1 , PA control circuit  80  may be disposed on principal surface  91   b , output transformer  15  and output transformer  25  may be disposed inside module board  91 , and in a plan view of module board  91 , the footprint of PA control circuit  80  may not overlap the footprint of output transformer  15  or the footprint of output transformer  25 . 
     In addition, radio frequency module  1  may further include switch  41  connected to an input terminal of power amplifier  10 A and an input terminal of power amplifier  20 A, and in a plan view of module board  91 , the footprint of switch  41  may not overlap the footprint of output transformer  15  or the footprint of output transformer  25 . 
     According to this configuration, it is possible to inhibit transmission signals input through the transmission input terminal from leaking to an unconnected output transformer via the off-capacitance of switch  41 . It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     In addition, radio frequency module  1  may further include switch  42  connected to the output terminal of power amplifier  10 A and the output terminal of power amplifier  20 A, and in a plan view of module board  91 , the footprint of switch  42  may not overlap the footprint of output transformer  15  or the footprint of output transformer  25 . 
     According to this configuration, it is possible to inhibit transmission signals output from output transformers  15  and  25  from leaking to an unconnected transmission or reception path via off-capacitance of switch  42 . It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     In addition, in radio frequency module  1 , PA control circuit  80 , switch  42 , and switch  41  may be included in a single semiconductor integrated circuit (IC). 
     According to this configuration, PA control circuit  80 , switch  41 , and switch  42  are located in proximity to one another, and thus it is possible to miniaturize radio frequency module  1 . Furthermore, since the control line that connects PA control circuit  80  and switch  41  and the control line that connects PA control circuit  80  and switch  42  can be shortened, it is possible to inhibit noise generation from the control lines. 
     In addition, in radio frequency module  1 A, output transformer  15  and output transformer  25  may be disposed inside module board  91 , and in a plan view of module board  91 , the footprint of semiconductor IC  70  may not overlap the footprint of output transformer  15  or the footprint of output transformer  25 . 
     According to this configuration, it is possible to: inhibit output transformers  15  and  25  from being affected by a digital noise; inhibit transmission signals output from output transformers  15  and  25  from leaking to an unconnected transmission or reception path via the off-capacitance of switch  42 ; or inhibit transmission signals input through the transmission input terminal from leaking to an unconnected output transformer via the off-capacitance of switch  41 . It is thus possible to reduce degradation of the signal quality of radio frequency signals output from output transformers  15  and  25 . 
     In addition, radio frequency module  1  may further include low noise amplifier  30  disposed on principal surface  91   b , and in a plan view of module board  91 , external-connection terminal  150  set to ground potential may be disposed between low noise amplifier  30  and output transformer  15  and between low noise amplifier  30  and output transformer  25 . 
     According to this configuration, the plurality of external-connection terminals  150  which are applied as ground electrodes are disposed between low noise amplifier  30  that significantly affects the reception sensitivity of the reception circuit and output transformers  15  and  25  that transfer high-power transmission signals. Accordingly, it is possible to inhibit degradation of reception sensitivity due to an inflow of a transmission signal and harmonic of the transmission signal to the reception path. 
     In addition, communication device  5  includes: antenna  2 ; and RFIC  3  configured to process radio frequency signals transmitted and received by antenna  2 ; and radio frequency module  1  configured to transfer the radio frequency signals between antenna  2  and RFIC  3 . 
     According to this configuration, it is possible to provide communication device  5  that includes a differential power amplifier, achieves reduction of quality degradation in transmission signals, and supports multi-band technologies. 
     Other Embodiments, Etc. 
     Although the radio frequency module and the communication device according to the embodiment of the present disclosure have been described above based on the embodiment, the working examples, and the variations, the radio frequency module and the communication device according to the present disclosure are not limited to the foregoing embodiment, working examples, and variations. The present disclosure also encompasses: other embodiments achieved by combining arbitrary structural components in the above-described embodiment, working examples, and variations; variations resulting from various modifications to the above-described embodiment, working examples, and variations that may be conceived by those skilled in the art without departing from the essence of the present disclosure; and various devices that include the above-described radio frequency module and the communication device. 
     For example, in the radio frequency module and the communication device according to the foregoing embodiment, working examples, and the variations, another circuit element and line, for example, may be inserted in a path connecting circuit elements and a signal path which are disclosed in the drawings. 
     Although only some exemplary embodiments of the present disclosure have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the present disclosure. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is applicable widely to communication apparatuses such as mobile phones as a radio frequency module disposed in a multiband-compatible front-end unit.