Patent Publication Number: US-2011057730-A1

Title: Radio frequency power amplifier

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to a radio frequency (RF) power amplifier used for amplifying power of an RF signal, and relates particularly to a multiband and multimode RF power amplifier which is compatible with different frequency bands and different wireless communication modes. 
     (2) Description of the Related Art 
     To enable global utilization of a digital mobile terminal, a mobile terminal which is usable in a multiband frequency range (such as a range centering on 2 GHz and a range centering on 900 MHz) and a multimode system (such as Global System for Mobile Communications (GSM), Digital Communication system (DCS), and Universal Mobile Transmission Standard (UMTS)) is rapidly growing popular. Normally, in the configuration of a transmission power amplifier which amplifies a high-level output of electric power in the mobile terminal, a couple of semiconductor transistors for amplifying radio frequencies are connected in multiple stages. For compatibility with multiple bands and multiple modes, various power amplifiers and wireless communication devices using such power amplifiers have been considered (for example, see: Japanese Unexamined Patent Application Publication No. 2005-294894; and Japanese Unexamined Patent Application Publication No. 2003-174111). 
     Generally, the power amplifier outputs a transmission power in a wide range of: approximately +35 dBm in GSM mode, approximately +33 dBm in DCS mode, and approximately +27 dBm to −50 dBm in UMTS mode. Particularly, near +35 dBm (GSM), +33 dBm (DCS), and +27 dBm (UMTS) where the power output within the mobile terminal is maximum, the influence on the receiving unit becomes maximum in the mobile terminal. Accordingly, it is necessary to suppress the influence to the receiving unit. 
     A power amplifier for the mobile terminal which is compatible with multiple bands and multiple modes has a configuration in which plural RF transmission circuits including a power amplifier are connected in parallel so as to secure radio frequency characteristics.  FIG. 7  shows a configuration of such a conventional RF power amplifier and a wireless communication device as described in Japanese Unexamined Patent Application Publication No. 2005-294894. 
     A wireless communication device  800  shown in  FIG. 7  includes: a microphone  801 ; a speaker  806 ; an RF power amplifier  810 ; an antenna switch  813 ; an antenna  814 ; a Radio Frequency IC (RFIC)  815  which converts a baseband signal into an RF signal or converts an RF signal into a baseband signal; a baseband signal processing device  816 ; a duplexer  817   a;  filters  818   a  and  818   b;  matching circuits  820  and  821 ; a switch  830 ; filters  840   b,    840   c,    840   d,  and  840   f;  a gain control device  860 ; RF receiving circuit devices  8120  to  8122 ; and a transmission circuit  8130 . Note that constituent elements enclosed by a dashed line constitute a first transmission path  8110 , and a combination including filter  818   a  among a combination of constituent elements enclosed by an alternate long and short dash line constitutes a second transmission path  8111 , and a combination including a filter  818   b  among a combination of constituent elements enclosed by an alternate long and short dash line constitutes a third transmission path  8112 . In this wireless communication device  800 , the first transmission path  8110  including the duplexer  817   a  is used for communications in the UMTS mode (using, for example, 2 GHz band) in accordance with Code Division Multiple Access (CDMA) scheme; the third transmission path  8112  including the filter  818   b  and the second transmission path  8111  including the filter  818   a  are used, respectively, for communications in GSM mode (using, for example, 900 MHz band) and communications in Digital Communication System (DCS) mode (using, for example, 1.8 GHz band) in accordance with Time Division Multiple Access (TDMA) scheme. 
     In addition, downsizing and cost reduction is considered to be an important issue for the multiband and multimode mobile communications device, and in order to respond to this, in recent years, efforts have been made to share a single input path between frequency bands of two frequency ranges when the frequency bands of RF signals input from RFIC  815  into the RF power amplifier  810  are relatively close to each other (such as frequency bands of 2 GHz and 1.8 GHz, and frequency bands of 850 MHz and 900 MHz). For example, an approach of deleting, in  FIG. 7 , the filter  840   c  and sharing one input path for inputting the two RF signals from the RFIC  815  to the RF power amplifier  810  has been considered. In this case, although it is necessary to improve the performance of the RFIC  815 , such a simplified interface between the RFIC  815  and the RF power amplifier  810  and the reduced number of terminals are expected to achieve improvements in size and costs. Thus, such a configuration can realize a wireless communication device which is compact, low cost, and capable of amplifying and transmitting electric power in response to multiple bands and multiple modes. 
     SUMMARY OF THE INVENTION 
       FIG. 8  is a diagram showing, in the case of adding one path of UMTS mode (for example, 850 MHz band) to the conventional wireless communication device described above, an example configuration of an RF power amplifier which is provided between an output of the RFIC, and matching circuits and filters in the wireless communication device. In other words, this RF power amplifier amplifies an RF signal of 850 MHz band within a frequency range at a low frequency side; an RF signal of 900 MHz band within a frequency range at the low frequency side; an RF signal of 1.8 GHz band within a frequency range at a high frequency side; and an RF signal of 2 GHz band within a frequency range at the high frequency side. In addition, the RF power amplifier is compatible with UMTS mode and DCS mode in the frequency ranges at the low frequency side, and is compatible with UMTS mode and GSM mode in the frequency ranges at the high frequency side. That is, the RF power amplifier shown in  FIG. 8  operates at plural frequency bands (multiband) and in plural modes (multimode) in each of the frequency bands. Note that the RF power amplifier  900  shown in the figure collectively includes one input terminal for adjacent frequency bands, and output terminals are provided for the respective modes and frequency bands. 
     The RF power amplifier  900  shown in the figure includes: power amplifiers  901 ,  902 ,  903 , and  904 ; input terminals IN 1  and IN 2 ; output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2 . 
     The power amplifier  901  amplifies a signal of 2 GHz band in UMTS mode, the power amplifier  902  amplifies a signal of 850 MHz band in UMTS mode, the power amplifier  903  amplifies a signal of 1.8 GHz band in DCS mode, and the power amplifier  904  amplifies a signal of 900 MHz band in GSM mode. 
     Of the RF signals input into the RF power amplifier  900 , the signals of 2 GHz band and 1.8 GHz band which have frequency bands relatively close to each other are input into an input terminal IN 1 , and the signals of 850 MHz band and 900 MHz band are input into the input terminal IN 2 , irrespective of modes. 
     The RF signal of 2 GHz band in UMTS mode, which is input into the input terminal IN 1 , is amplified by the power amplifier  901  to be output at the output terminal OUT_A 1 . Likewise, the RF signal of 1.8 GHz band in DCS mode, which is input into the input terminal IN 1 , is amplified by the power amplifier  903 , to be output at the output terminal OUT_B 1 . In addition, the RF signal of 900 MHz band in GSM mode, which is input into the input terminal IN 2 , is amplified by the power amplifier  904 , to be output at the output terminal OUT_B 2 . Likewise, the RF signal of 850 MHz band in UMTS mode, which is input into the input terminal IN 2 , is amplified by the power amplifier  902 , to be output at the output terminal OUT_A 2 . 
     As shown in  FIG. 8 , the output terminal OUT_A 1  for outputting the RF signal of 2 GHz band in UMTS mode and the output terminal OUT_A 2  for outputting the RF signal of 850 MHz band in UMTS mode are provided to be adjacent to each other or not to sandwich another output terminal in between, and the output terminal OUT_B 1  for outputting the RF signal of 1.8 GHz band in DCS mode and the output terminal OUT_B 2  for outputting the RF signal of 900 MHz band in GSM mode are provided to be adjacent to each other or not to sandwich another output terminal in between. 
     Here, an output line from the power amplifier  901  to the output terminal OUT_A 1 , an output line from the power amplifier  902  to the output terminal OUT_A 2 , an output line from the power amplifier  903  to the output terminal OUT_B 1 , and an output line from the power amplifier  904  to the output terminal OUT_B 2  are laid out with sufficient isolation secured so as to prevent the lines from crossing each other. 
     By adapting the configuration and layout of the RF power amplifier  900  as described above, it is possible to collectively provide connections between the output terminal OUT_A 1  and the duplexer and connections between the output terminal OUT_A 2  and the duplexer on a board in the wireless communication device, thus realizing, using a simple layout, a compact and low-cost wireless communication device. In addition, it is also possible to collectively provide connections between the output terminal OUT_B 1  and the filter and connections between the output terminal OUT_B 2  and the filter on the board in the wireless communication device, thus realizing, using a simpler layout, the compact and low-cost wireless communication device. 
     In such a wireless communication device using this RF power amplifier  900 , the RF signal of 2 GHz band in UMTS mode, which is output at the output terminal OUT_A 1 , is band-limited by the duplexer, to be transmitted from the antenna through the switch. The RF signal of 850 MHz band in UMTS mode, which is output at the output terminal OUT_A 2 , is band-limited by the duplexer, to be transmitted from the antenna  14  through the switch  13 . 
     In addition, the RF signal of 1.8 GHz band in DCS mode, which is output at the output terminal OUT_B 1 , is band-limited by the filter, to be transmitted from the antenna through the switch. The GSM signal of 900 MHz band in GSM mode, which is output at the output terminal OUT_B 2 , is band-limited by the filter  818   b,  to be transmitted from the antenna through the switch. 
     As described above, in the RF power amplifier in the present example and the wireless communication device using the RF power amplifier, the line in UMTS mode from the duplexer does not cross the transmission path in GSM or DCS mode, thus avoiding a problem of deterioration of radio frequency characteristics such as deterioration of reception sensitivity of the receiving unit caused by the crossing of the transmission path in DCS mode and the reception path in UMTS mode from the duplexer, and achieving satisfactory wireless communication characteristics in small size at low cost. 
     In the RF power amplifier  900 , the power amplifiers  901  to  904  include, on a semiconductor chip, a number of active elements such as transistors and passive elements such as resistors. Here, these active and passive elements, lines, and external connection pads are connected via lines each made of a metal or a low-resistant semiconductor that is doped with impurities at high level concentration, and so on. Such lines are formed by a multilayer wiring technique for the semiconductor. In addition, as represented by a crossing portion  911 , each line in a portion where at least two lines cross each other is separated into upper and lower layers by, for example, a silicon dioxide film or silicon nitride film, so as to be insulated from each other. 
     However, coupling of electric signals occurs between upper and lower lines at the crossing portion  911  due to parasitic capacitance, causing an influence of the electric signals between lines which should be electrically independent, and such influence is mixed as noise. Particularly, the semiconductor chip dealing with the RF signal is subject to the influence of the RF signal propagated through another line, which influence grows larger as the frequency of the RF signal becomes higher, thus causing a problem of deterioration of electrical characteristics. 
     It is possible to give deterioration of isolation as an example of deterioration of electrical characteristics. Even in the configuration described above, isolation does not deteriorate for an RF signal at an intermediate frequency (IF) signal band that is a relatively low frequency band of 100 MHz or so, but the isolation deteriorates with an RF signal of 800 MHz or higher. A more serious problem is that the deteriorated isolation causes a load of the RF power amplifier in an off state to appear, resulting in impedance fluctuation and causing parasitic resonance. 
     An object of the present invention is to provide a multiband RF power amplifier which operates with improved isolation at multiple bands and in multiple modes in each of the bands. 
     To solve the problem described above, a radio frequency power amplifier according to an aspect of the present invention includes: a first power amplifying circuit which linearly amplifies a first radio frequency signal of a first frequency band; a second power amplifying circuit which linearly amplifies a second radio frequency signal of a second frequency band lower than the first frequency band; a third power amplifying circuit which nonlinearly amplifies a third radio frequency signal of the first frequency band; and a fourth power amplifying circuit which nonlinearly amplifies a fourth radio frequency signal of the second frequency band, and the first power amplifying circuit includes: a first input pad for wire bonding formed on a semiconductor substrate; a first input line formed on the semiconductor substrate and having one end connected to the first input pad; a first power amplifier formed on the semiconductor substrate and connected to the other end of the first input line; a first output line formed on the semiconductor substrate and having one end connected to the first power amplifier; and a first output pad formed on the semiconductor substrate and connected to the other end of the first output line, the second power amplifying circuit includes: a second input pad for wire bonding formed on the semiconductor substrate; a second input line formed on the semiconductor substrate and having one end connected to the second input pad; a second power amplifier formed on the semiconductor substrate and connected to the other end of the second input line; a second output line formed on the semiconductor substrate and having one end connected to the second power amplifier; and a second output pad formed on the semiconductor substrate and connected to the other end of the second output line, the third power amplifying circuit includes: a third input pad for wire bonding formed on the semiconductor substrate; a third input line formed on the semiconductor substrate and having one end connected to the third input pad; a third power amplifier formed on the semiconductor substrate and connected to the other end of the third input line; a third output line formed on the semiconductor substrate and having one end connected to the third power amplifier; and a third output pad formed on the semiconductor substrate and connected to the other end of the third output line, the fourth power amplifying circuit includes: a fourth input pad for wire bonding formed on the semiconductor substrate; a fourth input line formed on the semiconductor substrate and having one end connected to the fourth input pad; a fourth power amplifier formed on the semiconductor substrate and connected to the other end of the fourth input line; a fourth output line formed on the semiconductor substrate and having one end connected to the fourth power amplifier; and a fourth output pad formed on the semiconductor substrate and connected to the other end of the fourth output line, the first and second output pads are disposed next to each other, the third and fourth output pads are disposed next to each other, the first to fourth input lines do not cross each other on the semiconductor substrate, and the first to fourth output lines do not cross each other on the semiconductor substrate. 
     With this configuration, on the semiconductor substrate, no coupling of RF signals due to parasitic capacitance is caused between the first to fourth input lines and between the first to fourth output lines. As a result, the RF power amplifier according to the aspect of the present invention improves isolation, and can operate in multiple modes in each of the first and second frequency bands. In addition, the first to fourth input pads are for wire bonding, with which the first to fourth input pads can be easily connected to another pad by wire bonding, thus simplifying the circuit configuration. 
     Here, the first input pad may be wire-bonded to a first input unit which is provided on a board that is to be mounted with the radio frequency power amplifier and into which the first and third radio frequency signals are input, the second input pad may be wire-bonded to a second input unit which is provided on the board and into which the second and fourth radio frequency signals are input, the third input pad may be wire-bonded to the first input unit, and the fourth input pad may be wire-bonded to the second input unit. 
     With this configuration, it is possible to easily connect the first input unit and the second input unit, and the first to fourth input pads. 
     Here, the radio frequency power amplifier may include: a board; and the semiconductor substrate to be mounted on the board, and the board may include: a first line having one end connected to the first input unit; a first connection pad connected to the other end of the first line; a second line having one end connected to the first connection pad; a second connection pad connected to the other end of the second line; a third line having one end connected to the second input unit; a third connection pad connected to the other end of the third line; a fourth line having one end connected to the third connection pad; and a fourth connection pad connected to the other end of the fourth line, and the radio frequency power amplifier may further include: a first wire having one end bonded to the first input pad and the other end bonded to one of the first and second connection pads that is closer to the first wire; a second wire having one end bonded to the second input pad and the other end bonded to one of the third and fourth connection pads that is closer to the second wire; a third wire having one end bonded to the third input pad and the other end bonded to the other of the first and second connection pads that is closer to the third wire; and a fourth wire having one end bonded to the fourth input pad and the other end bonded to the other of the third and fourth connection pads that is closer to the fourth wire. 
     With this configuration, the first to fourth wires bonded to the first to fourth input pads cross, in the case of crossing the input lines, in an upper potion in a direction perpendicular to the input lines. Thus, compared to the case of lines crossing each other in outer and inner layers on a multilayer substrate made up of dielectrics, the RF power amplifier  100   a  according to the present embodiment has a small spatial permittivity between lines and thus allows securing a distance larger than an interlayer distance of the multilayer substrate. In addition, such bonding using wires allows securing a distance larger than an interlayer distance of the multilayer substrate. Accordingly, it is possible to improve isolation in the signal paths at an input side of the power amplifiers AMP 1  to AMP 4 . 
     Here, the radio frequency power amplifier may include: a fifth wire having one end bonded to the first input unit and the other end bonded to one of the first and third input pads that is closer to the first input unit; and a sixth wire having one end bonded to the other of the first and third input pads and the other end bonded to the one of the first and third input pads connected to the first input unit. 
     Here, the radio frequency power amplifier may include: a seventh wire having one end bonded to the second input unit and the other end bonded to one of the second and fourth input pads that is closer to the second input unit; and an eighth wire having one end bonded to the other of the second and fourth input pads and the other end bonded to the one of the second and fourth input pads connected to the second input unit. 
     Here, the radio frequency power amplifier may include: a fifth wire having one end bonded to the first input unit and the other end bonded to one of the first and third input pads that is closer to the first input unit; a sixth wire having one end bonded to the other of the first and third input pads and the other end bonded to the one of the first and third input pads connected to the first input unit; a seventh wire having one end bonded to the second input unit and the other end bonded to one of the second and fourth input pads that is closer to the second input unit; and an eighth wire having one end bonded to the other of the second and fourth input pads and the other end bonded to the one of the second and fourth input pads connected to the second input unit. 
     With this configuration, since the lines on the board that are for connecting the input units and input pads are no longer necessary, it is possible to downsize the radio frequency power amplifier and to remove insertion loss that is caused when the RF signal is passing through the lines. In addition, for example, since this allows continuous bonding from the first input unit to the third input pad via the first input pad, it is possible to reduce the number of times of bonding. Accordingly, this increases productivity and cost advantages. 
     Here, at least one of the first to fourth input pads may be disposed closer to a corresponding one of the first to fourth power amplifiers than the others of the first to fourth input pads. 
     With this configuration, the wires bonded to the pads do not cross each other, thus facilitating the layout of each wire. 
     Here, one of the first to fourth input pads that is next to the at least one of the first to fourth input pads that is disposed closer to the corresponding one of the first to fourth power amplifiers may be disposed at a predetermined position on a line extended from the input line connected to the corresponding one of the first to fourth power amplifiers. 
     With this configuration, since a larger area can be secured for the input lines that constitute the impedance matching circuit, it is possible to achieve a multistage matching circuit with improved performance, thus reducing loss due to impedance mismatching with the RF signal, or increasing a gain of the power amplifier. In addition, since this reduces the distance between each input unit and each input pad, and thus reduces the length of the wire between the input pad and the wire, it is possible to reduce phase shift and insertion loss in the wire. 
     Here, the first input unit may be disposed equidistant from each of the first and third input pads. 
     Here, the second input unit may be disposed equidistant from each of the second and fourth input pads. 
     With this configuration, it is possible to reduce input impedance mismatching of the RF power amplifier in each mode at the same frequency band. 
     Here, the semiconductor substrate may include a first semiconductor chip and a second semiconductor chip, the first and second power amplifying circuits may be formed on the first semiconductor chip, and the third and fourth power amplifying circuits may be formed on the second semiconductor chip. 
     Here, the semiconductor substrate may include a first semiconductor chip, a second semiconductor chip, and a third semiconductor chip, the third and fourth power amplifying circuits may be formed on the first semiconductor chip, the first power amplifying circuit may be formed on the second semiconductor chip, and the second power amplifying circuit may be formed on the third semiconductor chip. 
     Here, the semiconductor substrate may include a first semiconductor chip, a second semiconductor chip, and a third semiconductor chip, the first and second power amplifying circuits may be formed on the first semiconductor chip, the third power amplifying circuit may be formed on the second semiconductor chip, and the fourth power amplifying circuit may be formed on the third semiconductor chip. 
     Here, the semiconductor substrate may include a first semiconductor chip, a second semiconductor chip, and a third semiconductor chip, the second and third power amplifying circuits may be formed on the first semiconductor chip, the first power amplifying circuit may be formed on the second semiconductor chip, and the fourth power amplifying circuit may be formed on the third semiconductor chip. 
     Here, the semiconductor substrate may include four semiconductor chips, and the first to fourth power amplifying circuits may be formed in the semiconductor chips different from each other. 
     Here, the semiconductor substrate may be a semiconductor chip. 
     Here, the third and fourth power amplifying circuits may be rotated to be disposed at a predetermined angle with respect to the first and second power amplifying circuits. 
     With this configuration, it is possible to downsize the RF power amplifier. In addition, by forming a desired RF power amplifying circuit on the same or a different semiconductor substrate, it is possible to reduce phase shift, insertion loss, or loss caused by impedance mismatching, thus forming the RF power amplifier with improved isolation. 
     According to the present invention, it is possible to provide an RF power amplifier which operates with improved isolation at multiple bands and in multiple modes in each of the bands. 
     FURTHER INFORMATION ABOUT TECHNICAL BACKGROUND TO THIS APPLICATION 
     The disclosure of Japanese Patent Application No. 2009-205148 filed on Sep. 4, 2009 including specification, drawings and claims is incorporated herein by reference in its entirety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings that illustrate a specific embodiment of the invention. In the Drawings: 
         FIG. 1  is a block diagram showing an example configuration of a wireless communication device; 
         FIG. 2A  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to a first embodiment; 
         FIG. 2B  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the first embodiment; 
         FIG. 3A  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to a second embodiment; 
         FIG. 3B  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment; 
         FIG. 3C  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment; 
         FIG. 3D  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment; 
         FIG. 3E  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment; 
         FIG. 3F  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment; 
         FIG. 3G  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment; 
         FIG. 4A  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to a third embodiment; 
         FIG. 4B  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the third embodiment; 
         FIG. 4C  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the third embodiment; 
         FIG. 4D  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the third embodiment; 
         FIG. 5  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to a fourth embodiment; 
         FIG. 6  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to a fifth embodiment; 
         FIG. 7  is a diagram showing an example circuit configuration of a conventional wireless communication device; and 
         FIG. 8  is a diagram showing an example configuration of the RF power amplifier in the case of further adding one path in UMTS mode (for example, 850 MHz band) to the conventional wireless communication device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     First, a wireless communication device to which a radio frequency (RF) power amplifier according to a first embodiment is applied will be described.  FIG. 1  is a block diagram showing an example configuration of the wireless communication device. 
     A wireless communication device  10  shown in the figure corresponds to two frequency bands in UMTS mode (850 MHz band and 2 GHz band), GSM mode (900 MHz band) and DCS mode (1.8 GHz band). In other words, the wireless communication device  10  is compatible with four bands, three modes, for example. The wireless communication device  10  includes an RF power amplifier  11 , a receiving unit  12 , a switch  13 , an antenna  14 , an RFIC  15 , and a baseband LSI  16 . 
     The RF power amplifier  11  amplifies an RF signal output from the RFIC  15 . The configuration of the RF power amplifier  11  will be described in detail later. 
     The receiving unit  12  receives, via the switch  13 , a signal received by the antenna  14 . 
     The switch  13  has one output terminal connected to the antenna and six input terminals connected to one of duplexers  17   a  and  17   b,  filters  18   a  and  18   b,  and the receiving unit  12 , and passes a transmitted signal or a received signal by electrically connecting the output terminal and one of the input terminals. Note that two input terminals are connected to the receiving unit  12 . 
     The antenna  14  transmits the signal propagated via the switch  13 . In addition, the antenna  14  receives, as a received signal, a signal transmitted from another wireless communication device. 
     The RFIC  15  converts a baseband signal output from the baseband LSI  16 , into an RF signal. In addition, the RFIC  15  demodulates the received signal received by the receiving unit  12  and supplies the demodulated signal to the baseband LSI  16 . 
     The baseband LSI  16  performs, for example, signal processing such as compression and coding on an audio signal, so as to generate a baseband signal. The baseband LSI  16  supplies the generated baseband signal to the RFIC  15 . In addition, the baseband LSI  16  performs signal processing such as sampling on the baseband signal input from the RFIC  15 , so as to convert the baseband signal into an audio signal. 
     The duplexers  17   a  and  17   b  band-limit the signal in UMTS mode which is transmitted from the RF power amplifier  11 , and transmit the band-limited signal from the antenna  14  via the switch  13 . In addition, the duplexers  17   a  and  17   b  band-limit the signal from the switch  13  which is received by the receiving unit  12 . 
     The filters  18   a  and  18   b  band-limit the signals in DCS mode and GSM mode transmitted from the RF power amplifier  11 , and transmit the band-limited signal from the antenna  14  via the switch  13 . 
     The configuration as described above allows the wireless communication device  10  shown in  FIG. 1  to perform communication at four bands, three modes. 
     Next, an example of a detailed configuration of the RF power amplifier described above will be described. 
     The RF power amplifier according to the present embodiment is an RF power amplifier which amplifies RF signals of two frequency bands, and includes: a first power amplifying circuit which linearly amplifies a first RF signal of a first frequency band; a second power amplifying circuit which linearly amplifies a second RF signal of a second frequency band lower than the first frequency band; a third power amplifying circuit which nonlinearly amplifies a third RF signal of the first frequency band; and a fourth power amplifying circuit which nonlinearly amplifies a fourth RF signal of the second frequency band, and each of the power amplifying circuits (the first to fourth power amplifying circuits) includes: an input pad for wire bonding formed on a semiconductor substrate; an input line formed on the semiconductor substrate and having one end connected to the input pad; an amplifier formed on the semiconductor substrate and connected to the other end of the input line; an output line formed on the semiconductor substrate and having one end connected to the power amplifier; and an output pad formed on the semiconductor substrate and connected to the other end of the output line, the output pads of the first and second power amplifying circuits are disposed next to each other, the output pads of the third and fourth power amplifying circuits are disposed next to each other, the input lines of the respective power amplifying circuits do not cross each other on the semiconductor substrate, and the output lines of the respective power amplifying circuits do not cross each other on the semiconductor substrate. 
     With this, the RF power amplifier according to the present embodiment can improve isolation and operate at multiple bands and in multiple modes in each of the bands. 
       FIG. 2A  is a diagram showing a circuit configuration and layout of the RF power amplifier according to the first embodiment, which represents an example of the RF power amplifier. 
     The RF power amplifier shown in the figure includes, on a board: chips  200  and  201  that are the semiconductor substrates in the present invention; the first to fourth connection pads  105  to  108 , input terminals IN 1  and IN 2 , and output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2  (see  FIG. 1 ). 
     Note that in the present embodiment it is sufficient to be compatible with at least two frequency bands and two frequency modes, respectively, and for convenience of explanation, an example described hereafter is assumed to be compatible with four bands, three modes, that is, DCS mode of 1.8 GHz band, GSM mode of 900 MHz band, UMTS mode of 2 GHz band, and UMTS mode of 850 MHz band. In other words, the RF power amplifier operates at a first frequency band in the high frequency range and a second frequency band in the low frequency range, operating in DCS mode and UMTS mode at the first frequency band and in GSM mode and UMTS mode at the second frequency band. That is, the RF power amplifier operates at multiple bands including the first frequency band and the second frequency band and in multiple modes in each of the bands (the first and second frequency bands). 
     The input terminal IN 1  corresponds to the first input unit in the present invention, and signals of two frequency bands in the high frequency ranges, that is, RF signals of 1.8 GHz band in DCS mode and of 2 GHz band in UMTS mode are input into the input terminal IN 1 . In addition, formed on the board  11   a  are: a line L 1  having one end connected to the input terminal IN 1 ; a pad  105  connected to the other end of the line L 1 ; a line L 2  having one end connected to the pad  105 ; and a pad  107  connected to the other end of the line L 2 . 
     In addition, the input terminal IN 2  corresponds to the second input unit in the present invention, and signals of the two frequency bands in the low frequency range, that is, RF signals of 900 MHz band in GSM mode and of 850 MHz band in UMTS mode are input into the input terminal IN 2 . In addition, formed on the board  11   a  are: a line L 3  having one end connected to the input terminal IN 2 ; a pad  106  connected to the other end of the line L 3 ; a line L 4  having one end connected to the pad  106 ; and a pad  108  connected to the other end of the line L 4 . 
     Note that the pads  105 ,  107 ,  106 , and  108  correspond to the first, the second, the third, and the fourth connection pads in the present invention, respectively. In addition, the lines L 1 , L 2 , L 3 , and L 4  correspond to the first, the second, the third, and the fourth connection lines in the present invention, respectively. 
     The chip  200  includes: a first power amplifying circuit  1  and a second power amplifying circuit  2  which require distortion characteristics, that is, linearly amplify the RF signal. The first power amplifying circuit  1  includes: a pad  101 , an input line L 11 , a power amplifier AMP 1 , an output line L 21 , and an output pad  111 . In addition, the second power amplifying circuit  2  includes: an input pad  102 , an input line L 12 , a power amplifier AMP 2 , an output line L 22 , and an output pad  112 . In addition, the pads  111  and  112  are disposed next to each other. 
     In addition, as with the chip  200 , the chip  201  includes: a third power amplifying circuit  3  and a fourth power amplifying circuit  4  which do not require distortion characteristics, that is, nonlinearly amplify the RF signal. The third power amplifying circuit  3  includes: an input pad  103 , an input line L 13 , a power amplifier AMP 3 , an output line L 23 , and an output pad  113 . In addition, the fourth power amplifying circuit  4  includes: an input pad  104 , an input line L 14 , a power amplifier AMP 4 , an output line L 24 , and an output pad  114 . In addition, the pads  113  and  114  are disposed next to each other. The power amplifiers AMP 3  and AMP 4  operate in a saturation region of transistors. 
     The power amplifier AMP 1 , which has an input side connected to the pad  101  via the input line L 11 , amplifies the RF signal of 2 GHz band in UMTS mode that is input from the pad  101 . Likewise, the power amplifier AMP 2  amplifies an RF signal of 850 MHz band in UMTS mode that is input from the pad  102 , the power amplifier AMP 3  amplifies an RF signal of 1.8 GHz band in DCS mode that is input from the pad  103 , and the power amplifier AMP 4  amplifies an RF signal of 900 MHz band in GSM mode that is input from the pad  104 . In addition, the power amplifier AMP 1  has an output side connected to the pad  111 , the power amplifier AMP 2  has an output side connected to the pad  112 , the power amplifier AMP 3  has an output side connected to the pad  113 , and the power amplifier AMP 4  has an output side connected to the pad  114 . 
     The pad  101  is electrically connected by wire bonding to the connection pad  105  formed on the board  11   a  via the wire  121 . In other words, the wire  121  has one end bonded to the pad  101 , and the other end bonded to the pad  105 . Likewise, the pad  102  is electrically connected to the pad  106  via the wire  122 , the pad  103  is electrically connected to the pad  107  via the wire  123 , and the pad  104  is electrically connected to the pad  108  via the wire  124 , respectively. 
     Note that the pads  101 ,  102 ,  103 , and  104  correspond, respectively, to the first, the second, the third, and the fourth input pads in the present invention. In addition, the wires  121 ,  122 ,  123 , and  124  correspond, respectively, to the first, the second, the third, and the fourth wires in the present invention. 
     In addition, the input line L 11  connecting the pad  101  and the power amplifier AMP 1  corresponds to the first input line in the present invention, the input line L 12  connecting the pad  102  and the power amplifier AMP 2  corresponds to the second input line in the present invention, the input line L 13  connecting the pad  103  and the power amplifier AMP 3  corresponds to the third input line in the present invention, and the input line L 14  connecting the pad  104  and the power amplifier AMP 4  corresponds to the fourth input line in the present invention. In addition, the power amplifiers AMP 1 , AMP 2 , AMP 3 , and AMP 4  correspond, respectively, to the first, the second, the third, and the fourth power amplifiers in the present invention. 
     In addition, the output line L 21  connecting the power amplifier AMP 1  and the pad  111  corresponds to the first output line in the present invention, the output line L 22  connecting the power amplifier AMP 2  and the pad  112  corresponds to the second output line in the present invention, the output line L 23  connecting the power amplifier AMP 3  and the pad  113  corresponds to the third output line in the present invention, and the output line L 24  connecting the power amplifier AMP 4  and the pad  114  corresponds to the fourth output line in the present invention. 
     In addition, the pads  111 ,  112 ,  113 , and  114  correspond, respectively, to the first, the second, the third, and the fourth output pads in the present invention. 
     Here, as shown in  FIG. 2A , the output line L 21  from the power amplifier AMP 1  to the pad  111 , the output line L 22  from the power amplifier AMP 2  to the pad  112 , the output line L 23  from the power amplifier AMP 3  to the pad  113 , and the output line L 24  from the power amplifier AMP 4  to the pad  114  do not cross each other. In addition, the input line L 11  from the pad  101  to the power amplifier AMP 1 , the input line L 12  from the pad  102  to the power amplifier AMP 2 , the input line L 13  from the pad  103  to the power amplifier AMP 3 , and the input line L 14  from the pad  104  to the power amplifier AMP 4  do not cross each other. 
     Thus, since the lines propagating RF signals do not cross each other on the chips  200  and  201 , it is possible to prevent deterioration of isolation of the RF signals between the pads  111  to  114 , which is caused by parasitic capacitance between lines. 
     In addition, the pads  111 ,  112 ,  113 , and  114  are connected, respectively, to the output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2  (see  FIG. 1 ). The output terminal OUT_A 1  outputs the signal of 2 GHz band in UMTS mode, which has been amplified by the power amplifier AMP 1 . The output terminal OUT_A 2 , which is disposed next to the output terminal OUT_A 1 , outputs the signal of 850 MHz band in UMTS mode, which has been amplified by the power amplifier AMP 2 . The output terminal OUT_B 1  outputs the signal of 1.8 GHz band in DCS mode, which has been amplified by the power amplifier AMP 3 . The output terminal OUT_B 2 , which is disposed next to the output terminal OUT_B 1 , outputs the signal of 900 MHz band in GSM mode, which has been amplified by the power amplifier AMP 4 . 
     An operation of the RF power amplifier according to the present embodiment will be described below. 
     Of the RF signals supplied from the RFIC  15  (see  FIG. 1 ) to the RF power amplifier, the RF signals of 2 GHz band and 1.8 GHz band of frequency ranges relatively close to each other are input into the input terminal IN 1 , and the RF signals of 850 MHz band and 900 MHz band are input into the input terminal IN 2 , irrespective of modes. 
     The RF signal of 2 GHz band in UMTS mode, which is input into the input terminal IN 1 , is input into the pad  101  formed on the chip  200  from the pad  105  formed on the board  11   a,  via the wire  121 . The RF signal of 2 GHz band in UMTS mode, which is input into the pad  101 , is amplified by the power amplifier AMP 1  via the input line L 11  on the chip  200 , to be output at the output terminal OUT_A 1 . 
     Likewise, the RF signal of 1.8 GHz band in DCS mode, which is input into the input terminal IN 1 , is input into the pad  103  formed on the chip  201  from the pad  107  formed on the board  11   a,  via the wire  123 . The RF signal of 1.8 GHz band in DCS mode, which is input into the pad  103 , is amplified by the power amplifier AMP 3  via the input line L 13  on the chip  201 , to be output at the output terminal OUT_B 1 . 
     In addition, likewise, the RF signal of 900 MHz band in GSM mode, which is input into the input terminal IN 2 , is input into the pad  104  formed on the chip  201  from the pad  108  formed on the board  11   a,  via the wire  124 . The RF signal of 900 MHz band in GSM mode, which is input into the pad  104 , is amplified by the power amplifier AMP 4  via the input line L 14  on the chip  201 , to be output at the output terminal OUT_B 2 . 
     In addition, likewise, the RF signal of 850 MHz band in UMTS mode, which is input into the input terminal IN 2 , is input into the pad  102  formed on the chip  200  from the pad  106  formed on the board  11   a,  via the wire  122 . The RF signal of 850 MHz band in UMTS mode, which is input into the pad  102 , is amplified by the power amplifier AMP 2  via the input line L 12  on the chip  200 , to be output at the output terminal OUT_A 2 . 
     Here, as shown in  FIG. 2A , the output terminal OUT_A 1  for outputting the RF signal of 2 GHz band in UMTS mode and the output terminal OUT_A 2  for outputting the RF signal of 850 MHz band in UMTS mode are disposed to be adjacent to each other or not to sandwich another output terminal in between, and the output terminal OUT_B 1  for outputting the RF signal of 1.8 GHz band in DCS mode and the output terminal OUT_B 2  for outputting the RF signal of 900 MHz band in GSM mode are disposed to be adjacent to each other or not to sandwich another output terminal in between. 
     In addition, the output line L 21  from the power amplifier AMP 1  to the pad  111 , the output line L 22  from the power amplifier AMP 2  to the pad  112 , the output line L 23  from the power amplifier AMP 3  to the pad  113 , and the output line L 24  from the power amplifier AMP 4  to the pad  114  are disposed not to cross each other. 
     Accordingly, an output line from the power amplifier AMP 1  to the output terminal OUT_A 1 , an output line from the power amplifier AMP 2  to the output terminal OUT_A 2 , an output line from the power amplifier AMP 3  to the output terminal OUT_B 1 , and an output line from the power amplifier AMP 4  to the output terminal OUT_B 2  do not cross each other. 
     In addition, the input line L 11  from the pad  101  to the power amplifier AMP 1 , the input line L 12  from the pad  102  to the power amplifier AMP 2 , the input line L 13  from the pad  103  to the power amplifier AMP 3 , and the input line L 14  from the pad  104  to the power amplifier AMP 4  do not cross each other. 
     Accordingly, a sufficient isolation is secured for the RF signal of three bands, four modes (1.8 GHz band in DCS mode, 900 MHz band in GSM mode, 2 GHz band in UMTS mode, and 850 MHz band in UMTS mode), which is amplified by each of the power amplifiers (power amplifiers AMP 1 , AMP 2 , AMP 3 , and AMP 4 ). 
     By thus laying out each of the output terminals (output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2 ), as shown in  FIG. 1 , it is possible to collectively provide, on the board of the wireless communication device, the connection between the output terminal OUT_A 1  and the duplexer  17   a  and the connection between the output terminal OUT_A 2  and the duplexer  17   b,  thus allowing a compact and low-cost wireless communication device to be realized using a simpler layout. In addition, it is also possible to collectively provide, on the board of the wireless communication device, the connection between the output terminal OUT_B 1  and the filter  18   a  and the connection between the output terminal OUT_B 2  and the filter  18   b,  thus allowing a compact and low-cost wireless communication device to be realized using a simpler layout. 
     As described above, the RF power amplifier shown in  FIG. 2A  is an RF power amplifier which amplifies RF signals of two frequency bands and includes: a first power amplifying circuit  1  which linearly amplifies a first RF signal of a first frequency band; a second power amplifying circuit  2  which linearly amplifies a second RF signal of a second frequency band lower than the first frequency band; a third power amplifying circuit  3  which nonlinearly amplifies a third RF signal of the first frequency band; and a fourth power amplifying circuit  4  which nonlinearly amplifies a fourth RF signal of the second frequency band, and the power amplifying circuits  1  to  4  include, respectively: the input pads  101  to  104  for wire bonding which are formed on the chips  200  and  201 ; the input lines L 11  to L 14  formed on the chips  200  and  201  and having one end connected to the input pads  101  to  104 , respectively; the power amplifiers AMP 1  to AMP 4  connected to the other end of the input lines L 11  to L 14 , respectively; the output lines L 21  to L 24  formed on the chips  200  and  201  and having one end connected to the power amplifiers AMP 1  to AMP 4 , respectively; and the output pads  111  to  114  formed on the chips  200  and  201  and connected to the other end of the output lines L 21  to L 24 , respectively, and the first output pad  111  and the second output pad  112  are disposed next to each other, the third output pad  113  and the fourth output pad  114  are disposed next to each other, the input lines L 11  to L 14  do not cross each other on the chips  200  and  201 , and the output lines L 21  to L 24  do not cross each other on the chips  200  and  201 . 
     In other words, the plural lines from the power amplifiers AMP 1  to AMP 4  to the output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2  do not cross each other. With this, the RF power amplifier can improve isolation at the output side of the power amplifiers AMP 1  to AMP 4 , thus achieving improved isolation and enabling operation at multiple bands and in multiple modes in each of the bands. Specifically, since the power amplifiers AMP 1  to AMP 4  provide a large power output, the isolation at the output side of these power amplifiers AMP 1  to AMP 4  significantly contributes to the isolation of the RF power amplifier. In other words, by improving the isolation at the output side of the power amplifiers AMP 1  to AMP 4 , it is possible to effectively improve the isolation of the RF power amplifier. 
     In addition, the input lines L 11  to L 14  from the input terminal IN 1  and IN 2  to the respective power amplifiers AMP 1  to AMP 4  do not cross each other on the chips  200  and  201 . In other words, the lines from the pads  101  to  104  to the power amplifiers AMP 1  to AMP 4  do not cross each other. With this, it is possible to improve isolation at a crossing point of the signal paths at the input side of the power amplifiers AMP 1  to AMP 4 . 
     Furthermore, the pads  101  to  104  are pads for wire bonding, and are connected via the wires  121  to  124 , respectively. For example, the RF signal of 1.8 GHz in DCS mode, which is input from the input terminal IN 1 , is input into the power amplifier AMP 3  through a signal path that is the line L 2  connecting between the pads  105  and  107  on the board  11   a,  but the RF signal of 850 MHz in UMTS mode, which is input from the input terminal IN 2 , is input into a signal path that is the wire  122  provided from the pad  106  to the pad  102  so as to cross, above in the vertical direction, the line L 2  formed on the board. Thus, compared to the case of crossing lines using not wires but, for example, a multilayer substrate or the like for crossing the lines in outer and inner layers of the multilayer substrate made up of dielectrics, the configuration allows a small spatial permittivity between the lines, and also allows securing a distance larger than an interlayer distance of the multilayer substrate. Accordingly, it is possible to improve isolation at a crossing point of the signal paths at the input side of the power amplifiers AMP 1  to AMP 4 . In addition, in the configuration described above, the power amplifiers AMP 1  and AMP 2  formed on the chip  200  are used for RF power amplifiers compatible with UMTS mode, that is, requiring distortion characteristics, and the power amplifiers AMP 3  and AMP 4  formed on the chip  201  are used for RF power amplifiers compatible with DCS mode and GSM mode, that is, not requiring distortion characteristics. Thus, by forming, on separate semiconductor substrates, the power amplifiers AMP 1  and AMP 2  requiring distortion characteristics, that is, operating linearly, and the power amplifiers AMP 3  and AMP 4  not requiring distortion characteristics, that is, operating nonlinearly, it is possible to change the configuration of each of the semiconductor substrates according to the characteristics required of each of the power amplifiers, thus improving the radio frequency characteristics. 
     In addition, a line from the input terminal IN 1  to the pad  103  is formed to be longer than the line from the input terminal IN 1  to the pad  101  by including the line L 2 . Likewise, a line from the input terminal IN 2  to the pad  104  is formed to be longer than the line from the input terminal IN 2  to the pad  102  by including the line L 4 . With this, for the power amplifiers AMP 1  and AMP 2  that linearly operate, inductance by the length of the line L 2  causes a phase shift, thus making it more difficult to perform impedance matching. However, this produces an advantageous effect of allowing the power amplifiers AMP 3  and AMP 4  which nonlinearly operate to require less accurate impedance matching for obtaining distortion characteristics as compared to the power amplifiers AMP 1  and AMP 2 . 
     Note that the lines from the input terminals IN 1  and IN 2  to the pads  101  to  104  are not limited to the description above. For example, the line from the input terminal IN 2  to the pad  102  may be longer than the line from the input terminal IN 2  to the pad  104 . 
       FIG. 2B  is a diagram showing a configuration in which, the input terminal IN 2  is disposed closer to the pad  104  in the configuration in  FIG. 2A  described above, and the pad  106  connected to the line L 3  is connected to the pad  104 . In addition, in the configuration, the other end of the line L 4  having one end connected to the pad  106  is connected to the pad  108  disposed closer to the pad  102 , and the pad  108  is connected to the pad  102 . 
     With this configuration, an input impedance of the power amplifier AMP 2  which amplifies the RF signal of 850 MHz band in UMTS mode has a phase caused to rotate by the length of the line L 4  between the pads  106  and  108  on the board  11   a,  thus causing input impedance mismatching and deteriorating distortion characteristics and so on. On the other hand, for the power amplifier AMP 4  which amplifies the RF signal of 900 MHz band in GSM mode, no loss is caused by line loss or phase shift by the length of the line L 4 , thus producing an advantageous effect of improving gain. 
     Note that the power amplifiers AMP 1  to AMP 4  may use a compound-semiconductor heterojunction bipolar transistor and a field-effect transistor. 
     In addition, in the first embodiment of the present invention, an example of the RF power amplifier compatible with four bands, three modes such as 1.8 GHz in DCS mode, 900 MHz band in GSM mode, 2 GHz band in UMTS mode, and 850 MHz band in UMTS mode has been described, but another frequency band or mode may be added. 
     Note that the configuration according to the present embodiment includes, on the board  11   a,  the pads  105 ,  106 ,  107 , and  108  and the lines L 1 , L 2 , L 3 , and L 4 ; however, the board  11   a  is not essential, and even when the board  11   a  does not include the pads  105 ,  106 ,  107 , and  108  and the lines L 1 , L 2 , L 3 , and L 4 , it is possible to achieve an object of the present invention, so long as the configuration is such that the pads  101  to  104  are provided for wire bonding, and that the input lines L 11  to L 14  and the output lines L 21  to L 24  do not cross each other. 
     Second Embodiment 
     An RF power amplifier according to a second embodiment differs from the RF power amplifier according to the first embodiment in that: in the present embodiment, the third input pad of the third power amplifying circuit is disposed closer to the third power amplifier than the first, the second, and the fourth input pads. In addition, one of the first and third input pads is directly bonded to the input terminal IN 1 , and the other of the first and third input pads is connected to the first or third input pad connected to the input terminal IN 1 . Likewise, one of the second and fourth input pads is directly bonded to the input terminal IN 2 , and the other of the second and fourth input pads is connected to the second or fourth input pad connected to the input terminal IN 2 . With this configuration, the wires bonded to the pads do not cross each other, thus improving isolation at a crossing point of the signal paths at the input side of the power amplifiers AMP 1  to AMP 4 . The following description will be focused on the differences from the first embodiment. 
       FIGS. 3A to 3G  are diagrams each showing a circuit configuration of the RF power amplifier according to the second embodiment of the present invention and an actual layout of the circuit configuration on a board. Note that  FIGS. 3B to 3F  show the same structure as  FIG. 3A  except that: in  FIGS. 3B to 3F , the power amplifier formed on the semiconductor device is either integrated or separately provided on plural semiconductor substrates. 
       FIG. 3A  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the second embodiment. The RF power amplifier shown in the figure includes, on a board  11   a:  chips  200  and  201  that correspond to the semiconductor substrates in the present invention; a pad  105  connected to the input terminal IN 1 ; a pad  106  connected to the input terminal IN 2 , and output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2  (see  FIG. 1 ). 
     In addition, the RF power amplifier according to the present embodiment also includes: a wire  131  having one end bonded to the pad  105  and the other end bonded to the pad  101  that is closest to the pad  105 ; a wire  133  having one end bonded to the pad  103  and the other end bonded to the pad  101  connected to the pad  105 ; a wire  132  having one end bonded to the pad  106  and the other end bonded to the pad  102  that is closest to the pad  106 ; and the wire  134  having one end bonded to the pad  104  and the other end bonded to the pad  102  connected to the pad  106 . 
     Note that the wires  131 ,  133 ,  132 , and  134  correspond, respectively, to the fifth, the sixth, the seventh, and the eighth wires in the present invention. 
     An RF signal of 2 GHz band in UMTS mode, which is input into the input terminal IN 1 , is input into the pad  101  formed on the chip  200  from the pad  105  formed on the board  11   a,  via the wire  131 . The RF signal of 2 GHz band in UMTS mode, which is input into the pad  101 , is amplified by the power amplifier AMP 1  via the input line L 11  on the chip  200 , to be output at the output terminal OUT_A 1 . 
     An RF signal of 1.8 GHz band in DCS mode, which is input into the input terminal IN 1 , is input into the pad  103  formed on the chip  201  from the pad  101  formed on the chip  200 , via the wire  133 . The RF signal of 1.8 GHz band in DCS mode, which is input into the pad  103 , is amplified by the power amplifier AMP 3  via the input line L 13  on the chip  201 , to be output at the output terminal OUT_B 1 . 
     In addition, an RF signal of 850 MHz band in UMTS mode, which is input into the input terminal IN 2 , is input into the pad  102  via the wire  132 . The RF signal of 850 MHz band in UMTS mode, which is input into the pad  102 , is amplified by the power amplifier AMP 2  via the input line L 12  on the chip  200 , to be output at the output terminal OUT_A 2 . 
     In addition, an RF signal of 900 MHz band in GSM mode, which is input into the input terminal IN 2 , is input into the pad  104  formed on the chip  201  from the pad  102  formed on the chip  200 , via the wire  134 . The RF signal of 900 MHz band in GSM mode, which is input into the pad  104 , is amplified by the power amplifier AMP 4  via the input line L 14  on the chip  201 , to be output at the output terminal OUT_B 2 . 
     Here, a feature is that the pad  103  on the semiconductor chip is disposed further inside the chip  201  than the other pads in a horizontal direction with respect to the drawing. In other words, the pad  103  that is the third input pad of the third power amplifying circuit  3  is disposed closer to the power amplifier AMP 3  than the pads  101 ,  102 , and  104  that are the first, the second, and the fourth input pads in the present invention. 
     With this configuration, the wires bonded to the pads do not cross each other, thus facilitating the layout of each wire. In addition, the wire  133  is provided to cross, above in the vertical direction, the input line L 12  connecting the pad  102  and the power amplifier AMP 2 . Thus, compared to the case of crossing lines using not wires but, for example, a multilayer substrate or the like for crossing the lines in outer and inner layers of the multilayer substrate made up of dielectrics, the configuration allows a small spatial permittivity between the lines, and also allows securing a distance larger than an interlayer distance of the multilayer substrate. Accordingly, it is possible to improve isolation at a crossing point of the signal paths at the input side of the power amplifiers AMP 1  to AMP 4 . 
     The configuration described above not only improves isolation at the input signal paths but also produces advantageous effects of downsizing by eliminating the need for areas for the pads  107  and  108  on the board  11   a  provided in the first embodiment, and for the lines connecting between the pads on the board  11   a,  and of suppressing insertion loss that occurs when the signal passes through the lines. In addition, regarding wire bonding, it is conventionally necessary to perform connection processing four times, that is, on the pads  105  and  101 , the pads  106  and  102 , the pads  107  and  103 , and the pads  108  and  104 ; however, according to the present invention, it is only necessary to perform the processing two times, for example, by serially connecting the pads starting from the pad  105  to the pad  103  via the pad  101 , and from the pad  106  to the pad  104  via the pad  102 , thus increasing productivity and cost advantages. 
     The RF power amplifier shown in  FIG. 3B  includes a semiconductor substrate made up of the chips  201 ,  202 , and  203 , with the third power amplifying circuit  3  and the fourth power amplifying circuit  4  formed on the chip  201 , and the first power amplifying circuit  1  formed on the chip  202 , and the second power amplifying circuit  2  formed on the chip  203 . That is, the configuration is such that: the power amplifier AMP 1  is integrated on the chip  202 , the power amplifier AMP 2  is integrated on the chip  203 , the power amplifiers AMP 3  and AMP 4  are integrated on the chip  201 , and these are configured on the board  11   a  on which the pads  105  and  106  connected to the input terminals IN 1  and IN 2  are formed. In this case, the isolation of the power amplifiers AMP 1  and AMP 2  that are integrated on the chips  202  and  203 , respectively, is improved. 
     The RF power amplifier shown in  FIG. 3C  includes a semiconductor substrate made up of the chips  200 ,  204 , and  205 , with the first power amplifying circuit  1  and the second power amplifying circuit  2  formed on the chip  200 , and the third power amplifying circuit  3  formed on the chip  204 , and the fourth power amplifying circuit  4  formed on the chip  205 . 
     That is, the configuration is such that: the power amplifiers AMP 1  and AMP 2  are integrated on the chip  200 , the power amplifier AMP 3  is integrated on the chip  204 , the power amplifier AMP 4  is integrated on the chip  205 , and these are configured on the board  11   a  on which the pads  105  and  106  connected to the input terminals IN 1  and IN 2  are formed. In this case, the isolation of the power amplifiers AMP 3  and AMP 4  that are integrated on the chips  204  and  205 , respectively, is improved. 
     The RF power amplifier shown in  FIG. 3D  includes a semiconductor substrate made up of the chips  206 ,  207 , and  208 , with the second power amplifying circuit  2  and the third power amplifying circuit  3  formed on the chip  207 , and the first power amplifying circuit  1  formed on the chip  206 , and the fourth power amplifying circuit  4  formed on the chip  208 . 
     That is, the configuration is such that: the power amplifier AMP 1  is integrated on the chip  206 , the power amplifiers AMP 2  and AMP 3  are integrated on the chip  207 , the power amplifier AMP 4  is integrated on the chip  208 , and these are configured on the board  11   a  on which the pads  105  and  106  connected to the input terminals IN 1  and IN 2  are formed. In this case, the isolation of the power amplifiers AMP 1 , AMP 2 , AMP 3 , and AMP 4  that are integrated on the chips  206 ,  207 , and  208 , respectively, is improved. 
     The RF power amplifier shown in  FIG. 3E  includes a semiconductor substrate made up of the chips  209 ,  210 ,  211 , and  212 , with the first power amplifying circuit  1  formed on the chip  209 , the second power amplifying circuit  2  formed on the chip  210 , the third power amplifying circuit  3  formed on the chip  211 , and the fourth power amplifying circuit  4  formed on the chip  212 . 
     That is, the configuration is such that: the power amplifier AMP 1  is integrated on the chip  209 , the power amplifier AMP 2  is integrated on the chip  210 , the power amplifier AMP 3  is integrated on the chip  211 , and the power amplifier AMP 4  is integrated on the chip  212 , and these are configured on the board  11   a  on which the pads  105  and  106  connected to the input terminals IN 1  and IN 2  are formed. In this case, the isolation of the power amplifiers AMP 1 , AMP 2 , AMP 3 , and AMP 4  that are integrated on the chips  209 ,  210 ,  211 , and  212 , respectively, is improved. 
     The RF power amplifier shown in  FIG. 3F  includes a semiconductor substrate made up of the chip  213 , with the first power amplifying circuit  1 , the second power amplifying circuit  2 , the third power amplifying circuit  3 , and the fourth power amplifying circuit  4  formed on the single chip  213 . 
     That is, the configuration is such that: the power amplifiers AMP 1 , AMP 2 , AMP 3 , and AMP 4  are integrated on the chip  213 , and these are configured on the board  11   a  on which the pads  105  and  106  connected to the input terminals IN 1  and IN 2  are formed. In this case, since all the power amplifiers AMP 1  to AMP 4  are integrated on the chip  213 , the semiconductor chip needs to be mounted on the board  11   a  only once as compared to the cases of  FIGS. 3A to 3E , thus producing a cost advantage, and it is also possible to expect downsizing by eliminating the need for a space between the semiconductor substrates that is expected to cover unevenness in placement at the time of mounting. 
       FIG. 3G  shows an RF power amplifier in which the pad  106  connected to the input terminal IN 2  is disposed closer to the pad  104  as compared to the RF power amplifier shown in  FIG. 3A . In addition, the RF power amplifier according to the present embodiment also includes: a wire  132  having one end bonded to the pad  106  and the other end bonded to the pad  104  that is closest to the pad  106 , and a wire  134  having one end bonded to the pad  104  and the other end bonded to the pad  102  connected to the pad  104 . 
     By adapting this configuration, in the power amplifier AMP 4  compatible with 900 MHz band in GSM mode, insertion loss or loss due to phase shift is not caused in the wire between the pads  102  and  104  on the semiconductor chip, thus producing an advantageous effect of improving gain. 
     In addition, since such a configuration allows increasing the distance between the input terminals IN 1  and IN 2 , it is possible to improve isolation of the RF signals of the first and second frequency bands. 
     Note that the power amplifiers AMP 1  to AMP 4  may use a compound-semiconductor heterojunction bipolar transistor and a field-effect transistor. 
     In addition, in the second embodiment, an example of the RF power amplifier compatible with four bands, three modes, that is, 1.8 GHz in DCS mode, 900 MHz band in GSM mode, 2 GHz band in UMTS mode, and 850 MHz band in UMTS mode has been described, but another frequency band or mode may be added. 
     Third Embodiment 
     An RF power amplifier according to a third embodiment differs from the RF power amplifier according to the second embodiment in that: in the present embodiment, the second and fourth input pads are directly connected to the input terminal IN 2 . With this configuration, the transmission path of the RF signal of 900 MHz band in GSM mode is shorter than the transmission path in the second embodiment as shown in  FIG. 3A  by a length of the wire between the pad  106  on the board  11   a  and the pad  104  on the chip  201 , thus suppressing phase shift and reducing insertion loss or loss caused by impedance mismatching. The following description will be focused on the differences from the second embodiment. 
       FIGS. 4A to 4D  are diagrams each showing a circuit configuration of the RF power amplifier according to the third embodiment of the present invention and an actual layout of the circuit configuration on a board. 
       FIG. 4A  is a diagram showing an example circuit configuration and layout of the RF power amplifier according to the third embodiment. As with the RF power amplifier shown in  FIG. 3A , the RF power amplifier shown in the figure includes, on a board  11   a:  chips  200  and  201  that correspond to the semiconductor substrates in the present invention; a pad  105  connected to the input terminal IN 1 ; a pad  106  connected to the input terminal IN 2 , and output terminals OUT_A 1 , OUT_A 2 , OUT_B 1 , and OUT_B 2  (see  FIG. 1 ). 
     In addition, the RF power amplifier according to the present embodiment also includes: a wire  141  having one end bonded to the pad  105  and the other end bonded to the pad  101  that is closest to the pad  105 ; a wire  143  having one end bonded to the pad  103  and the other end bonded to the pad  101  connected to the pad  105 ; a wire  142  having one end bonded to the pad  106  and the other end bonded to the pad  102  that is closest to the pad  106 ; and a wire  144  having one end bonded to the pad  104  and the other end directly bonded to the pad  106 . 
     In addition, an RF signal of 900 MHz band in GSM mode, which is input into the input terminal IN 2 , is input into the pad  104  formed on the chip  201  from the pad  106  formed on the board  11   a,  via the wire  144  directly connected to the pad  104 . The RF signal of 900 MHz band in GSM mode, which is input into the pad  104 , is amplified by the power amplifier AMP 4  via the input line L 14  on the chip  201 , to be output at the output terminal OUT_B 2 . 
     With this configuration, the transmission path of the RF signal of 900 MHz band in GSM mode is shorter than the transmission path in the second embodiment as shown in  FIG. 3A  by a length of the wire  142  between the pad  106  on the board  11   a  and the pad  102  on the chip  200 , thus suppressing phase shift and reducing insertion loss and loss caused by impedance mismatching. 
     Compared to the RF power amplifying circuit shown in  FIG. 4A , in the RF power amplifying circuit shown in  FIG. 4B , the pad  106  connected to the input terminal IN 2  is disposed closer to the pad  104 , and the RF power amplifying circuit shown in  FIG. 4B  includes a wire  142  having one end bonded to the pad  106  and the other end bonded to the pad  104  that is closest to the pad  106 , and a wire  144  having one end bonded to the pad  102  and the other end directly bonded to the pad  106 . 
     That is, an RF signal of 850 MHz band in UMTS mode, which is input into the input terminal IN 2 , is input into the pad  102  from the pad  106  formed on the board  11   a,  via the wire  144  directly connected to the pad  102  on the chip  200 . The RF signal of 850 MHz band in UMTS mode, which is input into the pad  102 , is amplified by the power amplifier AMP 2  via the input line L 12  on the chip  200 , to be output at the output terminal OUT_A 2 . 
     With this configuration, the transmission path of the RF signal of 850 MHz band in UMTS mode is rendered shorter than in the transmission path in the RF power amplifier shown in  FIG. 4A  by a length of the wire  142  between the pad  106  on the board  11   a  and the pad  104  on the chip  201 , thus suppressing phase shift and reducing insertion loss and loss caused by impedance mismatching. 
     The RF power amplifying circuit shown in  FIG. 4C  has a feature that the pad  106  connected to the input terminal IN 2  is disposed beside a horizontal axis of the pad  103  on the chip  201 . That is, compared to the RF power amplifying circuit shown in  FIGS. 4A and 4B , in the RF power amplifying circuit shown in  FIG. 4C , the pad  106  is disposed equidistant from each of the pads  102  and  104 , and the RF power amplifying circuit includes a wire  145  having one end bonded to the pad  106  and the other end bonded to the pad  102 , and a wire  146  having one end bonded to the pad  106  and the other end bonded to the pad  104 . 
     This configuration, when adapted, produces an advantageous effect of reducing input mismatching in the RF power amplifier of 900 MHz band in GSM mode than in the case of the RF power amplifier shown in  FIG. 4A , and also reducing the input mismatching in the RF power amplifier of 850 MHz band in UMTS mode than in the case of the RF power amplifier shown in  FIG. 4B . 
     Note that the power amplifiers AMP 1  to AMP 4  may use a compound-semiconductor heterojunction bipolar transistor and a field-effect transistor. 
     In addition, in the present embodiment, the pad  106  connected to the input terminal IN 2  is directly connected to the pads  102  and  104 , but the configuration may be such that the pad  105  connected to the input terminal IN 1  is directly connected to the pads  101  and  103 . In addition, the pad  105  may be disposed equidistant from each of the pads  101  and  103 . 
     Variation of Third Embodiment 
     In the third embodiment, an example of the RF power amplifier compatible with four bands, three modes of 1.8 GHz in DCS mode, 900 MHz band in GSM mode, 2 GHz band in UMTS mode, and 850 MHz band in UMTS mode has been described, but another frequency band or mode may be added. In this case, it is possible to add another power amplifying circuit as shown in  FIG. 4D . 
     The RF power amplifier shown in  FIG. 4D  includes, in addition to the configuration of the RF power amplifier shown in  FIG. 4A , a fifth power amplifying circuit  5  which includes: an input pad  109 , an input line L 15 , a power amplifier AMP 5 , an output line L 25 , and an output pad  115 . In addition, the RF power amplifier shown in the figure includes, on the board  11   a:  chips  214  and  201  that correspond to the semiconductor substrates in the present invention; a pad  105  connected to the input terminal IN 1 ; a pad  106  connected to the input terminal IN 2 , and output terminals OUT_A 1 , OUT_A 2 , OUT_A 3 , OUT_B 1 , and OUT_B 2 . 
     The chip  214  includes pads  101 ,  102 ,  109 ,  111 ,  112 , and  115 , and power amplifiers AMP 1 , AMP 2 , and AMP 5 . In addition, the chip  201  includes pads  103 ,  104 ,  113 , and  114 , and power amplifiers AMP 3  and AMP 4 . Here, the pads  109  and  104  are disposed closer to the power amplifiers  5  and  4 , respectively, than the pads  101 ,  102 , and  103 . 
     In addition, the RF power amplifier shown in  FIG. 4D  also includes: a wire  141  having one end bonded to the pad  105  and the other end bonded to the pad  101  that is closest to the pad  105 ; a wire  147  having one end bonded to the pad  105  and the other end bonded to the pad  102 ; a wire  148  having one end bonded to the pad  103  and the other end bonded to the pad  102  connected to the pad  105 ; and a wire  142  having one end bonded to the pad  106  and the other end bonded to the pad  104  that is closest to the pad  106 , and a wire  144  having one end connected to the pad  109  and the other end bonded to the pad  104  connected to the pad  106 . 
     With the configuration shown in  FIG. 4D , it goes without saying that the same advantageous effect as in  FIGS. 4A to 4C  above can be expected, and the wires bonded to the pads do not cross each other, thus facilitating the layout of each wire. In addition, it is possible to improve isolation at a crossing point of the signal paths at the input side of the power amplifiers AMP 1  to AMP 5 . 
     Note that the power amplifiers AMP 1  to AMP 5  may use a compound-semiconductor heterojunction bipolar transistor and a field-effect transistor. In addition, the number of the semiconductor chips or the power amplifiers is not limited to the example described above, but may be changed in any manner according to the number of bands and modes. 
     Fourth Embodiment 
     An RF power amplifier according to a fourth embodiment differs from the RF power amplifier according to the second embodiment in that: in the present embodiment, the third input pad of the third power amplifying circuit is disposed closer to the third power amplifier than the first, the second, and the fourth input pads, and the fourth input pad of the fourth power amplifying circuit is disposed at a predetermined position on a line extended from the input line of the third power amplifying circuit. With this configuration, since a larger area can be secured for the input lines that constitute the impedance matching circuit, it is possible to achieve a multistage matching circuit with improved performance, thus reducing loss in the RF signal caused by impedance mismatching or increasing the gain of the power amplifier. In addition, since this reduces the distance between each input unit and each input pad and accordingly reduces the length of the wire between the input pad and the wire, it is possible to reduce phase shift and insertion loss in the wire. The following description will be focused on the differences from the first embodiment. 
       FIG. 5  is a diagram showing a circuit configuration of the RF power amplifier according to the fourth embodiment of the present invention and an actual layout of the circuit configuration on a board. 
     As shown in  FIG. 5 , the present embodiment has a feature that the pad  104  formed on the chip  201  in  FIG. 3A  is disposed beside a horizontal axis of the pad  103  on the chip  201 . That is, the pad  103  that is the third input pad of the third power amplifying circuit  3  is disposed closer to the power amplifier AMP 3  than the pads  101 ,  102 , and  104  that correspond, respectively, to the first, the second, and the fourth input pads in the present invention, and the pad  104  next to the pad  103  is disposed on a line extended from the input line L 13  connected to the power amplifier AMP 3  and is also disposed at a position such that a distance from the power amplifier AMP 3  to the pad  104  is equal to a distance from the first power amplifier AMP 1  to the pad  101 . Then, the input line L 14  is vertically bent from the power amplifier AMP 4 , to be connected to the pad  104 . 
     In addition, the RF power amplifier according to the present embodiment also includes: a wire  151  having one end bonded to the pad  105  and the other end bonded to the pad  101  that is closest to the pad  105 ; a wire  153  having one end bonded to the pad  103  and the other end bonded to the pad  101  connected to the pad  105 ; a wire  152  having one end bonded to the pad  106  and the other end bonded to the pad  102  that is closest to the pad  106 ; and a wire  154  having one end bonded to the pad  104  and the other end bonded to the pad  102  connected to the pad  106 . 
     An RF signal of 900 MHz band in GSM mode, which is input into the input terminal IN 2 , is input into the pad  104  formed on the chip  201  from the pad  102  formed on the chip  200 , via the wire  154 . The RF signal of 900 MHz band in GSM mode, which is input into the pad  104 , is amplified by the power amplifier AMP 4  via the line on the chip  201 , to be output at the output terminal OUT_B 2 . 
     With this configuration, the RF amplifying circuit according to the present embodiment allows securing a wider path between the pad  104  on the chip  201  and the power amplifier AMP 4  compatible with 900 MHz band in GSM mode than the second embodiment as shown in  FIG. 3A . In other words, since a larger area can be secured for the input line L 14  that is the impedance matching circuit for the RF signal of 900 MHz band in GSM mode, it is possible to achieve a multistage matching circuit with improved performance, thus reducing loss caused by impedance mismatching in the RF signal of 900 MHz band in GSM mode, or increasing the gain of the power amplifier. In addition, since this reduces the distance between the pads  102  and  104  and accordingly reduces the length of the wire between the pads  102  and  104 , thus reducing phase shift and insertion loss in the wire. 
     Note that in the present embodiment, the configuration is such that the third input pad  103  is disposed closer to the power amplifier AMP 3 , and the fourth input pad  104  adjacent to the third input pad  103  is disposed at the predetermined position on the line extended from the input line L 13  of the third power amplifying circuit  3 , but a pad other than the third and fourth pads may also be disposed in such a manner. 
     Fifth Embodiment 
     An RF power amplifier according to a fifth embodiment differs from the RF power amplifier according to the second embodiment in that: in the present embodiment, the third and fourth power amplifying circuits are rotated to be disposed at a predetermined angle with respect to the first and the second power amplifying circuits. With this configuration, it is possible to downsize the RF power amplifier. In addition, by forming a desired RF power amplifying circuit on the same or a different semiconductor substrate, it is possible to reduce phase shift, insertion loss, or loss caused by impedance mismatching, thus forming the RF power amplifier with improved isolation. The following description will be focused on the differences from the second embodiment. 
       FIG. 6  is a diagram showing a circuit configuration of the RF power amplifier according to the fifth embodiment of the present invention and an actual layout of the circuit configuration on a board. 
     As shown in  FIG. 6 , the present embodiment has a feature that: as compare to the RF power amplifier shown in  FIG. 3A , the chip  201  is rotated 90 degrees in a clockwise direction to be disposed. 
     In addition, the RF power amplifier according to the present embodiment also includes: a wire  161  having one end bonded to the pad  105  and the other end bonded to the pad  101  that is closest to the pad  105 ; a wire  163  having one end bonded to the pad  103  and the other end bonded to the pad  101  connected to the pad  105 ; a wire  162  having one end bonded to the pad  106  and the other end bonded to the pad  102  that is closest to the pad  106 ; and a wire  164  having one end bonded to the pad  104  and the other end bonded to the pad  102  connected to the pad  106 . 
     The second embodiment described earlier has a feature that the pad  103  on the chip  201  is disposed further inside the chip  201  than the other pads, that is, disposed closest to the power amplifier AMP 3 , but this case has resulted in narrowing the input path on the chip  201  for the power amplifier AMP 3  compatible with 1.8 GHz in DCS mode, that is, reducing size of the area for the input matching circuit formed between the pad  103  and the power amplifier AMP 3 . On the other hand, by disposing the chip  201  as in the present embodiment, the wire  163  connecting the pads  101  and  103  and the wire  164  connecting the pads  102  and  104  do not cross each other, so that the pad  103  need not be disposed closer to the power amplifier AMP 3 , and thus a larger area can be secured for the impedance matching circuit, thus achieving a multistage matching circuit with improved performance and reducing the loss caused by impedance mismatching or increasing the gain of the power amplifier. 
     In addition, by disposing the chip  201  as shown in the present embodiment, the distance between the pads  102  and  104  is reduced, with the length of the bond wire between the pads  102  and  104  reduced accordingly, thus producing another advantageous effect of reducing phase shift and insertion loss in the bond wire. 
     Note that in the present embodiment, the chip  201  is rotated in a clockwise direction, but it goes without saying that the same advantageous effect can be produced by rotating the chip  200  in an anticlockwise direction. 
     Thus far, the RF power amplifier according to embodiments of the present invention has been described with reference to the first to the fifth embodiments, but the present invention is not limited to these embodiments. Those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. 
     For example, in the descriptions above, the output terminals OUT_A 1  and OUT_A 2  connected to the duplexer have been disposed next to each other, but may be disposed at a distance as long as other terminals connected to the filters (for example, output terminals OUT_B 1  and OUT_B 2 ) are not disposed between the output terminals OUT_A 1  and OUT_A 2 . 
     Although only some exemplary embodiments of this invention 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 this invention. Accordingly, all such modifications are intended to be included within the scope of this invention. 
     INDUSTRIAL APPLICABILITY 
     An RF power amplifier according to the present invention is appropriate for multiband and multimode performance, and is applicable to a mobile terminal device and so on.