AMPLIFIER CIRCUIT AND COMMUNICATION DEVICE

An amplifier circuit includes a high frequency input terminal and a high frequency output terminal, amplifiers, an output transformer having an input-side coil and an output-side coil, inductors, and a bypass capacitor. An output end of the amplifier is connected to one end of the input-side coil and one end of the inductor. An output end of the amplifier is connected to the other end of the input-side coil and one end of the inductor. The other end of the inductor, the other end of the inductor, and one end of the bypass capacitor are connected to a midpoint of the input-side coil. One end of the output-side coil is connected to the high frequency output terminal.

TECHNICAL FIELD

The present disclosure relates to an amplifier circuit and a communication device.

BACKGROUND ART

Patent Document 1 (FIG. 8 thereof) discloses a differential amplification type amplifier circuit having a first amplifier, a second amplifier, a first transformer (input transformer), and a second transformer (output transformer). One end of the output-side coil of the input transformer is connected to the input end of the first amplifier, and the other end of the output-side coil is connected to the input end of the second amplifier. One end of the input-side coil of the output transformer is connected to the output end of the first amplifier, and the other end of the input-side coil is connected to the output end of the second amplifier.

Patent Document 2 discloses a harmonic wave suppression circuit connectable to a transformer. A series connection circuit of two capacitors and an inductor is connected between one end and the other end of the input-side coil of the transformer.

CITATION LIST

Patent Documents

SUMMARY OF DISCLOSURE

Technical Problem

For example, as a configuration in which a power supply voltage or a bias voltage is supplied to the first amplifier and the second amplifier of the amplifier circuit disclosed in Patent Document 1, a configuration in which the power supply voltage or the bias voltage is supplied to the midpoint of the input-side coil or the output-side coil is assumed. In such a case, by providing the amplifier circuit disclosed in Patent Document 1 with a bypass capacitor between a power supply voltage supply terminal or a bias voltage supply terminal connected to the midpoint and the ground, and by adding the LC series resonance circuit disclosed in Patent Document 2, it is possible to achieve a small-sized amplifier circuit in which a power supply voltage or a bias voltage with suppressed high frequency noise is supplied.

However, in the case of the configuration in which the LC series resonance circuit disclosed in Patent Document 2 is added to the amplifier circuit disclosed in Patent Document 1, there is a problem that the impedance in a low frequency band corresponding to the signal bandwidth of a high frequency signal increases, and a so-called memory effect becomes significant, so that the ACLR (Adjacent Channel Leakage Power Ratio) deteriorates.

The present disclosure is made to solve the above problem, and a feature of the present disclosure is to provide a differential amplification type amplifier circuit and communication device in which the impedance in a low frequency band is reduced.

Solution to Problem

To achieve the above feature, an amplifier circuit according to the present disclosure includes: a high frequency input terminal and a high frequency output terminal; a first amplifying element and a second amplifying element; an output transformer having a first input-side coil and a first output-side coil; a first inductor and a second inductor; and a first bypass capacitor. An output end of the first amplifying element is connected to one end of the first input-side coil and one end of the first inductor. An output end of the second amplifying element is connected to the other end of the first input-side coil and one end of the second inductor. The other end of the first inductor, the other end of the second inductor, and one end of the first bypass capacitor are connected to the first input-side coil. One end of the first output-side coil is connected to the high frequency output terminal. The other end of the first bypass capacitor and the other end of the first output-side coil are connected to a ground.

Advantageous Effects of Disclosure

According to the present disclosure, it is possible to provide a differential amplification type amplifier circuit and communication device in which the impedance in a low frequency band is reduced.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described below with reference to the drawings. It should be noted that all the embodiments described below are comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement of components, connection forms and the like shown in the following embodiments are examples and are not intended to limit the present disclosure. Among the components in the following examples and variations, component(s) not described in the independent claims are described as optional component(s). Also, the size or size ratio of the components shown in the drawings is not necessarily strictly illustrated. In each drawing, substantially identical components are denoted by the same reference signs, and duplicate descriptions may be omitted or simplified.

In the present disclosure, the terms indicating relationships between elements, such as “parallel” and “orthogonal”, and the terms indicating the shape of elements, such as “rectangular”, as well as numerical ranges not only represent strict meanings, but also include substantially equivalent ranges, for example, with errors of several percent.

In the present disclosure, the term “connected” includes not only assuming directly connected by connection terminals and/or wiring conductors, but also assuming electrically connected via other circuit elements. Further, the expression “connected between A and B” means “connected to both A and B on a path connecting A and B”.

In the present disclosure, the expression “in plan view of the substrate” means viewing a substrate and circuit elements mounted on the substrate orthographically projected onto a plane parallel to the main surface of the substrate.

In the component arrangement of the present disclosure, the expression “a component is disposed on the substrate” includes that the component is disposed on the main surface of the substrate and that the component is disposed inside the substrate. The expression “a component is disposed on the main surface of the substrate” includes that the component is disposed above the main surface without contacting the main surface (for example, a component is stacked on another component disposed in contact with the main surface) in addition to that the component is disposed in contact with the main surface of the substrate. The expression “a component is disposed on the main surface of the substrate” may also include that the component is disposed in a recessed portion formed in the main surface. The expression “a component is disposed in the substrate” includes that the entire component is disposed between both main surfaces of the substrate but a portion of the component is not covered by the substrate and that only a portion of the component is disposed in the substrate, in addition to that the component is encapsulated in the module substrate.

In the present disclosure, the term “path” means a transmission line composed of a wire through which a high frequency signal propagates, electrodes directly connected to the wire, terminals directly connected to the wire or the electrodes, and/or the like.

In the present disclosure, the expression “the component A is arranged in series in the path B” means that both the signal input end and the signal output end of the component A are connected to the wire, the electrodes, or the terminals constituting the path B.

Embodiments

[1. Circuit Configuration of Amplifier Circuit and Communication Device]

The circuit configuration of an amplifier circuit10and a communication device4according to an embodiment will be described with reference toFIG.1.FIG.1is a circuit configuration diagram of the amplifier circuit10and the communication device4according to the embodiment.

[1.1 Circuit Configuration of Communication Device4]

First, the circuit configuration of the communication device4will be described. As shown inFIG.1, the communication device4according to the present embodiment includes a high frequency circuit1, an antenna2, and an RF signal processing circuit (RFIC: Radio Frequency Integrated Circuit)3.

The high frequency circuit1transmits a high frequency signal between the antenna2and the RFIC3. The detailed circuit configuration of the high frequency circuit1will be described later.

The antenna2is connected to an antenna connection terminal100of the high frequency circuit1, and transmits the high frequency signal outputted from the high frequency circuit1. The antenna2may also receive a high frequency signal from the outside and output the received high frequency signal to the high frequency circuit1.

The RFIC3is an example of a signal processing circuit for processing high frequency signals. Specifically, the RFIC3processes a transmission signal inputted from a baseband signal processing circuit (BBIC, not shown) by up-conversion or the like, and outputs a transmission signal generated by the signal processing to a transmission path of the high frequency circuit1. The RFIC3may also processes a received signal inputted via a reception path of the high frequency circuit1by down-conversion or the like, and outputs a received signal generated by the signal processing to the BBIC. The RFIC3has a control unit for controlling switches, amplifiers and the like of the high frequency circuit1. Note that a part or all of the functions as the control unit of the RFIC3may alternatively be implemented outside the RFIC3, for example, in the BBIC or in the high frequency circuit1.

The RFIC3also has a function as a control unit for controlling a power supply voltage Vcc and a bias voltage Vb to be supplied to each amplifier of the amplifier circuit10. Specifically, the RFIC3outputs a digital control signal to a power supply circuit (not shown) and a bias circuit (not shown). The power supply circuit and the bias circuit may also be disposed in the high frequency circuit1or the amplifier circuit10. The power supply voltage Vcc controlled by the digital control signal is supplied from the power supply circuit to each amplifier of the amplifier circuit10, and the bias voltage Vb controlled by the digital control signal is supplied from the bias circuit to each amplifier of the amplifier circuit10.

The RFIC3functions as a control unit for controlling the connection of switches51and54of the high frequency circuit1based on the communication band (frequency band) to be used.

Note that, in the communication device4according to the present embodiment, the antenna2is not an essential component.

[1.2 Circuit Configuration of High Frequency Circuit1and Amplifier Circuit10]

Next, the circuit configuration of the high frequency circuit1will be described. As shown inFIG.1, the high frequency circuit1includes an amplifier circuit10, filters52and53, the switches51and54, and the antenna connection terminal100.

The amplifier circuit10amplifies high frequency transmission signals (hereinafter referred to as transmission signals) of band A and band B inputted from a high frequency input terminal101. The high frequency circuit1may include, instead of the amplifier circuit10, a first amplifier circuit for amplifying the transmission signal of the band A and a second amplifier circuit for amplifying the transmission signal of the band B.

In the present embodiment, each of the band A and band B is a frequency band predefined by a standardization organization or the like (for example, 3GPP (registered trademark) (3rd Generation Partnership Project), IEEE (Institute of Electrical and Electronics Engineers) and the like) for a communication system built using RAT (Radio Access Technology). In the present embodiment, the communication systems that can be used include, but are not limited to, a 4G (4th Generation)-LTE (Long Term Evolution) system, a 5G (5th Generation)-NR (New Radio) system, and a WLAN (Wireless Local Area Network) system.

The filter52is connected between the switches51and54, and passes, among the transmission signals amplified by the amplifier circuit10, the transmission signals in the transmission band of the band A. The filter53is connected between the switches51and54, and passes, among the transmission signals amplified by the amplifier circuit10, the transmission signal in the transmission band of the band B.

Each of the filters52and53may constitute a duplexer together with a reception filter, or may be a single filter for transmitting signals by TDD (Time Division Duplex) system. Assuming each of the filters52and53is a TDD filter, a switch for switching between transmission and reception is disposed in at least one of the preceding and succeeding stages of the single filter.

The switch51has a common terminal, a first selection terminal, and a second selection terminal. The common terminal is connected to a high frequency output terminal102of the amplifier circuit10. The first selection terminal is connected to the filter52, and the second selection terminal is connected to the filter53. In such a connection configuration, the switch51switches the connection between the amplifier circuit10and the filter52, and the connection between the amplifier circuit10and the filter53.

The switch54is an example of an antenna switch. The switch54is connected to the antenna connection terminal100, switches the connection and disconnection between the antenna connection terminal100and the filter52, and switches the connection and disconnection between the antenna connection terminal100and the filter53.

The high frequency circuit1may include a receiving circuit for transmitting the received signal received from the antenna2to the RFIC3. In such a case, the high frequency circuit1includes a low-noise amplifier and a reception filter.

An impedance matching circuit may be disposed between the high frequency output terminal102and the antenna connection terminal100.

With the above circuit configuration, the high frequency circuit1can transmit or receive the high frequency signal of either of the band A and band B. Further, the high frequency circuit1can perform at least one of simultaneous transmission, simultaneous reception, and simultaneous transmission and reception of the high frequency signals of band A and band B.

Note that it is sufficient for the high frequency circuit1according to the present disclosure to have at least the amplifier circuit10of the circuit configuration shown inFIG.1.

Here, the circuit configuration of the amplifier circuit10will be described in detail.

As shown inFIG.1, the amplifier circuit10includes amplifiers11and12, a preamplifier13, an output transformer21, an input transformer22, bypass capacitors41and42, a capacitor43, inductors31,32,33and34, the high frequency input terminal101, the high frequency output terminal102, a Vcc terminal103, and a Vb terminal104. The amplifier circuit10according to the present embodiment is a differential amplification type amplifier circuit having the amplifiers11and12.

The high frequency input terminal101is connected to the RFIC3. The high frequency output terminal102is connected to the antenna connection terminal100via the switches51and54and the filters52and53. The Vcc terminal103is an example of a power supply voltage supply terminal, and is connected to a power supply circuit (not shown) that outputs the power supply voltage Vcc. The Vb terminal104is an example of a bias voltage supply terminal, and is connected to a bias circuit (not shown) that outputs the bias voltage Vb. Each of the high frequency input terminal101, the high frequency output terminal102, the antenna connection terminal100, the Vcc terminal103, and the Vb terminal104may be a metal conductor such as a metal electrode or a metal bump, or may be a point (node) on a metal wiring.

The amplifier11is an example of a first amplifying element. The amplifier11amplifies the high frequency balanced signal outputted from one end of the output-side coil222, and outputs a first high frequency balanced signal. The amplifier12is an example of a second amplifying element. The amplifier12amplifies the high frequency balanced signal outputted from the other end of the output-side coil222, and outputs a second high frequency balanced signal.

Each of the amplifiers11and12has an amplification transistor. The amplification transistor is, for example, a bipolar transistor such as an HBT (Heterojunction Bipolar Transistor) or a field effect transistor such as a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). Assuming the amplification transistor is a bipolar transistor, the input end of the amplifier11becomes, for example, a base end of the bipolar transistor, and the output end of the amplifier11becomes, for example, a collector end of the bipolar transistor. Assuming the amplification transistor is a field effect transistor, the input end of the amplifier11becomes, for example, a gate end of the field effect transistor, and the output end of the amplifier11becomes, for example, a drain end of the field effect transistor.

The preamplifier13amplifies the transmission signal(s) of the band A and/or band B inputted from the high frequency input terminal101.

The input transformer22is an example of a first input transformer, and includes an input-side coil221and an output-side coil222.

The input-side coil221is an example of a second input-side coil. One end of the input-side coil221is connected to the high frequency input terminal101via the preamplifier13, and the other end of the input-side coil221is connected to the ground. The output-side coil222is an example of a second output-side coil. One end of the output-side coil222is connected to the input end of the amplifier11, and the other end of the output-side coil222is connected to the input end of the amplifier12. The input-side coil221and the output-side coil222are electromagnetically coupled to each other. With the above configuration, the input transformer22converts a high frequency non-balanced signal outputted from the preamplifier13into two high frequency balanced signals having mutually opposite phases (power distribution).

The input-side coil211is an example of a first input-side coil. One end of the input-side coil211is connected to the output end of the amplifier11, and the other end of the input-side coil211is connected to the output end of the amplifier12. The output-side coil212is an example of a first output-side coil. One end of the output-side coil212is connected to the high frequency output terminal102via the capacitor43, and the other end of the output-side coil212is connected to the ground. The input-side coil211and the output-side coil212are electromagnetically coupled to each other. According to the above configuration, the output transformer21combines the first high frequency balanced signal outputted from the amplifier11and the second high frequency balanced signal outputted from the amplifier12in power, and outputs a high frequency non-balanced signal.

The bypass capacitor41is an example of a first bypass capacitor. One end (one electrode) of the bypass capacitor41is connected to the midpoint of the input-side coil211and the Vcc terminal103, and the other end (the other electrode) of the bypass capacitor41is connected to the ground. The bypass capacitor41has a capacitance value of 100 pF or more, for example, and has a function of suppressing the fundamental waves of the high frequency signals outputted from the amplifiers11and12from leaking into the power supply circuit. Note that the bypass capacitor41may also be loaded in the power supply circuit.

The bypass capacitor42is an example of a second bypass capacitor. One end (one electrode) of the bypass capacitor42is connected to the midpoint of the output-side coil222and the Vb terminal104, and the other end (the other electrode) of the bypass capacitor42is connected to the ground. The bypass capacitor42has a capacitance value of 100 pF or more, for example, and has a function of suppressing the fundamental waves of the high frequency signals inputted to the amplifiers11and12from leaking into the bias circuit. Note that the bypass capacitor42may also be loaded in the bias circuit.

The bypass capacitors41and42have a function of reducing the impedance in a low frequency band (particularly in a low frequency band of 10 MHz or less).

The inductor31is an example of a first inductor. One end of the inductor31is connected to the output end of the amplifier11and one end of the input-side coil211, and the other end of the inductor31is connected to the midpoint of the input-side coil211. The inductor32is an example of a second inductor. One end of the inductor32is connected to the output end of the amplifier12and the other end of the input-side coil211, and the other end of the inductor32is connected to the midpoint of the input-side coil211.

Note that one end of the bypass capacitor41, the Vcc terminal103, the other end of the inductor31, and the other end of the inductor32are not limited to being connected to the midpoint of the input-side coil211, as long as they are connected to a node on the input-side coil211other than one end and the other end of the input-side coil211.

The inductor33is an example of a third inductor. One end of the inductor33is connected to the input end of the amplifier11and one end of the output-side coil222, and the other end of the inductor33is connected to the midpoint of the output-side coil222. The inductor34is an example of a fourth inductor. One end of the inductor34is connected to the input end of the amplifier12and the other end of the output-side coil222, and the other end of the inductor34is connected to the midpoint of the output-side coil222.

Note that one end of the bypass capacitor42, the Vb terminal104, the other end of the inductor33, and the other end of the inductor34are not limited to being connected to the midpoint of the output-side coil222, as long as they are connected to a node on the output-side coil222other than one end and the other end of the output-side coil222.

The capacitor43is an example of a matching circuit, and is arranged in series between one end of the output-side coil212and the high frequency output terminal102. The capacitor43can suppress unnecessary signals among the signals outputted from one end of the output-side coil212.

Note that, in the amplifier circuit10according to the present embodiment, the preamplifier13, the input transformer22, the bypass capacitor42, the Vb terminal104, the inductors33and34, and the capacitor43are not essential components.

In the amplifier circuit10according to the present embodiment, the power supply voltage Vcc is supplied from the midpoint of the output transformer21to the output end of the amplifier11and the output end of the amplifier12by using the fact that the midpoint of the output transformer21is a virtual ground. Also, the bias voltage Vb is supplied from the midpoint of the input transformer22to the input end of the amplifier11and the input end of the amplifier12by using the fact that the midpoint of the input transformer22is a virtual ground.

[1.3 Circuit Configurations of Amplifier Circuits According to Variations 1 and 2]

FIG.2is a circuit configuration diagram of an amplifier circuit10A according to Variation 1. As shown inFIG.2, the amplifier circuit10A includes amplifiers11and12, a preamplifier13, an output transformer21, an input transformer22, bypass capacitors41and42, capacitors43,44and45, inductors31,32,33and34, a high frequency input terminal101, a high frequency output terminal102, a Vcc terminal103, and a Vb terminal104. The amplifier circuit10A according to the present variation differs from the amplifier circuit10according to the embodiment in that the capacitors44and45are added. Hereinafter, the amplifier circuit10A according to the present variation will be described with a focus on the differences from the amplifier circuit10according to the embodiment.

The capacitor44is an example of a first capacitor. One end (one electrode) of the capacitor44is connected to the other end of the inductor31and the other end of the inductor32, and the other end (the other electrode) of the capacitor44is connected to the ground. That is, the capacitor44is connected between the other ends of the inductor31and inductor32and the ground.

The capacitor45is an example of a second capacitor. One end (one electrode) of the capacitor45is connected to the other end of the inductor33and the other end of the inductor34, and the other end (the other electrode) of the capacitor45is connected to the ground. That is, the capacitor45is connected between the other ends of the inductor33and inductor34and the ground.

FIG.3is a circuit configuration diagram of an amplifier circuit10B according to Variation 2. As shown inFIG.3, the amplifier circuit10B includes amplifiers11and12, a preamplifier13, an output transformer21, an input transformer22, bypass capacitors41and42, capacitors43,46and47, inductors31,32,33,34,35and36, a high frequency input terminal101, a high frequency output terminal102, a Vcc terminal103, and a Vb terminal104. The amplifier circuit10B according to the present variation differs from the amplifier circuit10according to the embodiment in that the capacitors46and47and the inductors35and36are added. Hereinafter, the amplifier circuit10B according to the present variation will be described with a focus on the differences from the amplifier circuit10according to the embodiment.

The capacitor46and the inductor35are connected in series to each other to constitute an LC series resonance circuit61(first LC series circuit). The series connection circuit of the capacitor46and the inductor35is connected between the output end of the amplifier11and the ground. With the above configuration, the series connection circuit of the capacitor46and the inductor35has a function of suppressing harmonic waves outputted from the amplifier11. In the present variation, the inductor35is connected to the output end of the amplifier11and the capacitor46is connected to the ground, but the capacitor46may be connected to the output end of the amplifier11and the inductor35may be connected to the ground.

The capacitor47and the inductor36are connected in series to each other to constitute an LC series resonance circuit62(second LC series circuit). The series connection circuit of the capacitor47and the inductor36is connected between the output end of the amplifier12and the ground. With the above configuration, the series connection circuit of the capacitor47and the inductor36has a function of suppressing harmonic waves outputted from the amplifier12. In the present variation, the inductor36is connected to the output end of the amplifier12and the capacitor47is connected to the ground, but the capacitor47may be connected to the output end of the amplifier12and the inductor36may be connected to the ground.

With the configuration of the amplifier circuit10B according to Variation 2, since high-order harmonic components can be short-circuited by the first LC series circuit and the second LC series circuit, particularly second-order harmonic components can be suppressed.

[1.4 Amplifier Circuit According to Comparative Example]

FIG.4is a circuit configuration diagram of an amplifier circuit510according to a comparative example. As shown inFIG.4, the amplifier circuit510according to the comparative example includes amplifiers11and12, a preamplifier13, an output transformer21, an input transformer22, bypass capacitors41and42, a capacitor43, a high frequency input terminal101, a high frequency output terminal102, a Vcc terminal103, and a Vb terminal104. The amplifier circuit510according to the comparative example differs from the amplifier circuit10according to the embodiment only in that the inductors31to34are not added.

In the amplifier circuit510according to the comparative example, the power supply voltage Vcc is supplied from the midpoint of the output transformer21to the output end of the amplifier11and the output end of the amplifier12by using the fact that the midpoint of the output transformer21is a virtual ground. Also, the bias voltage Vb is supplied from the midpoint of the input transformer22to the input end of the amplifier11and the input end of the amplifier12by using the fact that the midpoint of the input transformer22is a virtual ground.

However, in the amplifier circuit510, since the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the amplifier11and the path for supplying the bias voltage Vb from the bypass capacitor41to the output end of the amplifier12include the inductance component of the input-side coil211, the impedance in a low frequency band such as 100 MHz, which is the baseband bandwidth of the NR signal, increases. Thus, there is a problem that the intermodulation distortion component generated by mixing the baseband with the fundamental wave band of the high frequency signal increases (i.e., so-called memory effect becomes significant), so that the ACLR of the high frequency signal in the fundamental wave band deteriorates.

Even assuming the LC series resonance circuit disclosed in Patent Document 2 is added to the amplifier circuit510according to the comparative example, the LC series resonance circuit is a circuit for suppressing high-order harmonic waves. Therefore, the impedance in the low frequency band of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the amplifier11and the path for supplying the bias voltage Vb from the bypass capacitor41to the output end of the amplifier12does not decrease, which also causes the memory effect to become significant, so that the ACLR of the high frequency signal in the fundamental wave band deteriorates.

[1.5 Comparison of Characteristics of Amplifier Circuits According to Embodiment and Comparative Example]

FIG.5is a graph showing frequency characteristics of the impedances of the amplifier circuits according to the embodiment and the comparative example. Specifically,FIG.5shows the impedance at the input ends (base ends) of the amplifiers11and12and the output ends (collector ends) of the amplifiers11and12.

In the amplifier circuit10according to the embodiment, the impedance in the vicinity of 100 MHZ (to 200 MHz), which is the baseband bandwidth of the NR signal, is reduced by almost half as compared with the amplifier circuit510according to the comparative example. This is because, in the amplifier circuit10, the inductor31is connected in parallel between one end and the midpoint of the input-side coil211, so that the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the amplifier11is reduced. In addition, this is because, in the amplifier circuit10, the inductor32is connected in parallel between the other end and the midpoint of the input-side coil211, so that the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the amplifier12is reduced.

In addition, this is because, in the amplifier circuit10, the inductor33is connected in parallel between one end and the midpoint of the output-side coil222, so that the inductance component of the path for supplying the bias voltage Vb from the bypass capacitor42to the input end of the amplifier11is reduced. In addition, this is because, in the amplifier circuit10, the inductor34is connected in parallel between the other end and the midpoint of the output-side coil222, so that the inductance component of the path for supplying the bias voltage Vb from the bypass capacitor42to the input end of the amplifier12is reduced.

FIG.6Ais a graph showing the ACLR of the amplifier circuit510according to the comparative example.FIG.6Bis a graph showing the ACLR of the amplifier circuit10according to the embodiment.FIGS.6A and6Bshow the output power dependence of the ACLR of the NR signal near the high frequency side (denoted as ACLR_U) and the output power dependence of the ACLR of the NR signal near the low frequency side (denoted as ACLR_L).

In the amplifier circuit510according to the comparative example, the ACLR_U is deteriorated relative to the ACLR_L. In contrast, in the amplifier circuit10according to the embodiment, the ACLR_U is particularly improved, and the asymmetrical characteristics of the ACLR_L and ACLR_U are suppressed to ensure symmetry. That is, in the amplifier circuit10according to the embodiment, by arranging the inductors31to34, the memory effect is suppressed by reducing the impedance in the low frequency band (baseband) without increasing the number of bypass capacitors, so that the ACLR is improved.

In the amplifier circuit10A according to Variation 1, the impedance in the low frequency band (baseband) can be further reduced by, in addition to the inductors31to34, grounding the midpoint of the input-side coil211in a more high-frequency manner by the capacitor44, so that the memory effect can be further suppressed.

[1.6 Voltage Combining Type Doherty Amplifier Circuit According to Variation 3]

FIG.7Ais a circuit configuration diagram of an amplifier circuit10C according to Variation 3. The amplifier circuit10C includes carrier amplifiers14and15, peak amplifiers16and17, preamplifiers18and19, output transformers21aand21b, input transformers22aand22b, bypass capacitors41,42aand42b, capacitors43and48, inductors31a,31b,32a,32b,33a,33b,34aand34b, a phase shift circuit60, a high frequency input terminal101, a high frequency output terminal102, a Vcc terminal103, and Vb terminals104aand104b. The amplifier circuit10C according to the present variation is a Doherty amplifier circuit having the carrier amplifiers14and15and the peak amplifiers16and17. The amplifier circuit10C according to the present variation differs from the amplifier circuit10according to the embodiment in that the carrier amplifiers14and15constitute a differential amplification type amplifier and the peak amplifiers16and17constitute a differential amplification type amplifier. Hereinafter, the amplifier circuit10C according to the present variation will be described with a focus on the differences from the amplifier circuit10according to the embodiment.

A Doherty amplifier circuit means an amplifier circuit that achieves high efficiency by using a plurality of amplifying elements as carrier amplifiers and peak amplifiers. A carrier amplifier means an amplifying element that operates in a Doherty amplifier circuit regardless of whether the power of the high frequency signal (input) is low or high. A peak amplifier means an amplifying element that mainly operates in a Doherty amplifier circuit assuming the power of the high frequency signal (input) is high. Therefore, assuming the input power of the high frequency signal is low, the high frequency signal is amplified mainly by the carrier amplifier, and assuming the input power of the high frequency signal is high, the high frequency signal is amplified and combined by the carrier amplifier and the peak amplifier. Due to such operation, in the Doherty amplifier circuit, the load impedance at low output power is increased assuming seen from the carrier amplifier, so that the efficiency at low output power is improved.

The Vcc terminal103is an example of the power supply voltage supply terminal, and is connected to a power supply circuit (not shown) that outputs the power supply voltage Vcc. The Vb terminal104ais an example of the bias voltage supply terminal, and is connected to a bias circuit (not shown) that outputs a bias voltage Vb1 supplied to the carrier amplifiers14and15. The Vb terminal104bis an example of the bias voltage supply terminal, and is connected to a bias circuit (not shown) that outputs a bias voltage Vb2 supplied to the peak amplifiers16and17.

The preamplifiers18and19amplify the transmission signal(s) of the band A and/or band B inputted from the high frequency input terminal101via the phase shift circuit60.

The phase shift circuit60distributes a signal RF0 outputted from the RFIC3, and outputs distributed signals RF1 and RF2 to the preamplifiers18and19, respectively. At this time, the phase shift circuit60adjusts the phases of the signals RF1 and RF2. For example, the phase shift circuit60shifts the signal RF2 by (−90+α)° with respect to the signal RF1.

The configuration of the phase shift circuit60and the preamplifiers18and19is not limited to the configuration described above. For example, the preamplifiers18and19may be disposed as one preamplifier in the preceding stage of the phase shift circuit60. Also, the amplifier circuit10C does not necessarily include the phase shift circuit60and the preamplifiers18and19.

Each of the carrier amplifiers14and15and the peak amplifiers16and17has an amplification transistor. The amplification transistor is, for example, a bipolar transistor such as an HBT or a field effect transistor such as a MOSFET.

The carrier amplifier14is an example of a third amplifying element, and amplifies a transmission signal of the band A or band B inputted to the carrier amplifier14. The carrier amplifier14is, for example, a class A (or class AB) amplifier circuit capable of performing amplification operation for all power levels of the signal inputted to the carrier amplifier14, and can perform highly efficient amplification operation, particularly in a low output region and a medium output region. The carrier amplifier14amplifies a high frequency balanced signal outputted from one end of the output-side coil222a, and outputs a third high frequency balanced signal.

The carrier amplifier15is an example of a fourth amplifying element, and amplifies a transmission signal of the band A or band B inputted to the carrier amplifier15. The carrier amplifier15is, for example, a class A (or class AB) amplifier circuit capable of performing amplification operation for all power levels of the signal inputted to the carrier amplifier15, and can perform highly efficient amplification operation, particularly in a low output region and a medium output region. The carrier amplifier15amplifies a high frequency balanced signal outputted from the other end of the output-side coil222a, and outputs a fourth high frequency balanced signal.

The peak amplifier16is an example of the first amplifying element, and amplifies a transmission signal of the band A or band B inputted to the peak amplifier16. The peak amplifier16is, for example, a class C amplifier circuit capable of performing amplification operation in a region where the power level of the signal inputted to the peak amplifier16is high. The peak amplifier16amplifies a high frequency balanced signal outputted from one end of the output-side coil222b, and outputs a first high frequency balanced signal.

The peak amplifier17is an example of the second amplifying element, and amplifies a transmission signal of the band A or band B inputted to the peak amplifier17. The peak amplifier17is, for example, a class C amplifier circuit capable of performing amplification operation in a region where the power level of a signal inputted to the peak amplifier17is high. The peak amplifier17amplifies a high frequency balanced signal outputted from the other end of the output-side coil222b, and outputs a second high frequency balanced signal.

A bias current smaller than the bias current applied to the amplification transistors of the carrier amplifiers14and15may be applied to the amplification transistors of the peak amplifiers16and17. Thus, the higher the power level of the signals inputted to the peak amplifiers16and17, the lower the output impedance becomes. Thus, the peak amplifiers16and17can perform an amplification operation with low distortion in a high output region.

The input transformer22ais an example of a second input transformer, and includes an input-side coil221aand an output-side coil222a.

The input-side coil221ais an example of a third input-side coil. One end of the input-side coil221ais connected to the high frequency input terminal101via the preamplifier18and the phase shift circuit60, and the other end of the input-side coil221ais connected to the ground. The output-side coil222ais an example of a third output-side coil. One end of the output-side coil222ais connected to the input end of the carrier amplifier14, and the other end of the output-side coil222ais connected to the input end of the carrier amplifier15. The input-side coil221aand the output-side coil222aare electromagnetically coupled to each other. With the above configuration, the input transformer22aconverts the high frequency non-balanced signal outputted from the preamplifier18into two high frequency balanced signals having mutually opposite phases (power distribution).

The input transformer22bis an example of the first input transformer, and includes an input-side coil221band an output-side coil222b.

The input-side coil221bis an example of the second input-side coil. One end of the input-side coil221bis connected to the high frequency input terminal101via the preamplifier19and the phase shift circuit60, and the other end of the input-side coil221bis connected to the ground. The output-side coil222bis an example of the second output-side coil. One end of the output-side coil222bis connected to the input end of the peak amplifier16, and the other end of the output-side coil222bis connected to the input end of the peak amplifier17. The input-side coil221band the output-side coil222bare electromagnetically coupled to each other. With the above configuration, the input transformer22bconverts the high frequency non-balanced signal outputted from the preamplifier19into two high frequency balanced signals having mutually opposite phases (power distribution).

The input-side coil211ahas one end thereof connected to the output end of the carrier amplifier14, and the other end thereof connected to the output end of the carrier amplifier15. The output-side coil212ahas one end thereof connected to the high frequency output terminal102via the capacitor43, and the other end thereof connected to one end of the output-side coil212b. The input-side coil211aand the output-side coil212aare electromagnetically coupled to each other. With the above configuration, the output transformer21acombines the third high frequency balanced signal outputted from the carrier amplifier14and the fourth high frequency balanced signal outputted from the carrier amplifier15in power, and outputs a high frequency non-balanced signal.

The input-side coil211bis an example of the first input-side coil. One end of the input-side coil211bis connected to the output end of the peak amplifier16, and the other end of the input-side coil211bis connected to the output end of the peak amplifier17. The output-side coil212bis an example of the first output-side coil. One end of the output-side coil212bis connected to the other end of the output-side coil212a, and the other end of the output-side coil212bis connected to the ground. The capacitor48is connected between both ends of the output-side coil212b. The input-side coil211band the output-side coil212bare electromagnetically coupled to each other. With the above configuration, the output transformer21bcombines the first high frequency balanced signal outputted from the peak amplifier16and the second high frequency balanced signal outputted from the peak amplifier17in power, and outputs a high frequency non-balanced signal.

The high frequency non-balanced signal obtained by combining the signals outputted from the carrier amplifiers14and15in power and the high frequency non-balanced signal obtained by combining the signals outputted from the peak amplifiers16and17in power are combined in voltage by the output transformers21aand21b, and the high frequency signal combined in voltage is outputted from the high frequency output terminal102via the capacitor43.

The bypass capacitor41is an example of the first bypass capacitor. One end (one electrode) of the bypass capacitor41is connected to the midpoint of the input-side coil211a, the midpoint of the input-side coil211b, and the Vcc terminal103, and the other end (the other electrode) of the bypass capacitor41is connected to the ground. The bypass capacitor41has a function of suppressing the fundamental waves of the high frequency signals outputted from the carrier amplifiers14and15and the fundamental waves of the high frequency signals outputted from the peak amplifiers16and17from leaking into the power supply circuit.

The bypass capacitor42ais an example of a third bypass capacitor. One end (one electrode) of the bypass capacitor42ais connected to the midpoint of the output-side coil222aand the Vb terminal104a, and the other end (the other electrode) of the bypass capacitor42ais connected to the ground. The bypass capacitor42ahas a function of suppressing the fundamental waves of the high frequency signals inputted to the carrier amplifiers14and15from leaking into the bias circuit.

The bypass capacitor42bis an example of the second bypass capacitor. One end (one electrode) of the bypass capacitor42bis connected to the midpoint of the output-side coil222band the Vb terminal104b, and the other end (the other electrode) of the bypass capacitor42bis connected to the ground. The bypass capacitor42bhas a function of suppressing the fundamental waves of the high frequency signals inputted to the peak amplifiers16and17from leaking into the bias circuit.

In addition, the bypass capacitors41,42aand42bhave a function of reducing the impedance in a low frequency band (particularly at a frequency of 10 MHz or lower).

The inductor31ais an example of a fifth inductor. One end of the inductor31ais connected to the output end of the carrier amplifier14and one end of the input-side coil211a, and the other end of the inductor31ais connected to the midpoint of the input-side coil211a. The inductor32ais an example of a sixth inductor. One end of the inductor32ais connected to the output end of the carrier amplifier15and the other end of the input-side coil211a, and the other end of the inductor32ais connected to the midpoint of the input-side coil211a.

The inductor31bis an example of the first inductor. One end of the inductor31bis connected to the output end of the peak amplifier16and one end of the input-side coil211b, and the other end of the inductor31bis connected to the midpoint of the input-side coil211b. The inductor32bis an example of the second inductor. One end of the inductor32bis connected to the output end of the peak amplifier17and the other end of the input-side coil211b, and the other end of the inductor32bis connected to the midpoint of the input-side coil211b.

Note that one end of the bypass capacitor41, the Vcc terminal103, the other end of the inductor31a, and the other end of the inductor32aare not limited to being connected to the midpoint of the input-side coil211a, as long as they are connected to a node on the input-side coil211aother than one end and the other end of the input-side coil211a. Also, one end of the bypass capacitor41, the Vcc terminal103, the other end of the inductor31b, and the other end of the inductor32bare not limited to being connected to the midpoint of the input-side coil211b, as long as they are connected to a node on the input-side coil211bother than one end and the other end of the input-side coil211b.

The inductor33ais an example of a seventh inductor. One end of the inductor33ais connected to the input end of the carrier amplifier14and one end of the output-side coil222a, and the other end of the inductor33ais connected to the midpoint of the output-side coil222a. The inductor34ais an example of an eighth inductor. One end of the inductor34ais connected to the input end of the carrier amplifier15and the other end of the output-side coil222a, and the other end of the inductor34ais connected to the midpoint of the output-side coil222a.

The inductor33bis an example of the third inductor. One end of the inductor33bis connected to the input end of the peak amplifier16and one end of the output-side coil222b, and the other end of the inductor33bis connected to the midpoint of the output-side coil222b. The inductor34bis an example of the fourth inductor. One end of the inductor34bis connected to the input end of the peak amplifier17and the other end of the output-side coil222b, and the other end of the inductor34bis connected to the midpoint of the output-side coil222b.

Note that one end of the bypass capacitor42a, the Vb terminal104a, the other end of the inductor33a, and the other end of the inductor34aare not limited to being connected to the midpoint of the output-side coil222a, as long as they are connected to a node on the output-side coil222aother than one end and the other end of the output-side coil222a. Also, one end of the bypass capacitor42b, the Vb terminal104b, the other end of the inductor33b, and the other end of the inductor34bare not limited to being connected to the midpoint of the output-side coil222b, as long as they are connected to a node on the output-side coil222bother than one end and the other end of the output-side coil222b.

Note that, in the amplifier circuit10C according to the present variation, the preamplifiers18and19, the input transformers22aand22b, the bypass capacitors42aand42b, the Vb terminals104aand104b, the inductors33a,33b,34aand34b, and the capacitor43are not essential components.

In the amplifier circuit10C according to the present variation, the power supply voltage Vcc is supplied from the midpoint of the output transformer21aand the midpoint of the output transformer21bto the output ends of the carrier amplifiers14and15and the peak amplifiers16and17by using the fact that the midpoint of the output transformer21aand the midpoint of the output transformer21bare virtual grounds. Further, the bias voltage Vb1 is supplied from the midpoint of the input transformer22ato the input ends of the carrier amplifiers14and15by using the fact that the midpoint of the input transformer22ais a virtual ground. Further, the bias voltage Vb2 is supplied from the midpoint of the input transformer22bto the input ends of the peak amplifiers16and17by using the fact that the midpoint of the input transformer22bis a virtual ground.

With the above configuration, since the inductor31ais connected in parallel between one end and the midpoint of the input-side coil211a, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the carrier amplifier14is reduced. In addition, since the inductor32ais connected in parallel between the other end and the midpoint of the input-side coil211a, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the carrier amplifier15is reduced. Therefore, the output impedances of the carrier amplifiers14and15in a low frequency band such as the baseband can be reduced. In addition, since the inductor31bis connected in parallel between one end and the midpoint of the input-side coil211b, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the peak amplifier16is reduced. In addition, since the inductor32bis connected in parallel between the other end and the midpoint of the input-side coil211b, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the peak amplifier17is reduced. Therefore, the output impedances of the peak amplifiers16and17in a low frequency band such as the baseband can be reduced.

Further, since the inductor33ais connected in parallel between one end and the midpoint of the output-side coil222a, the inductance component of the path for supplying the bias voltage Vb1 from the bypass capacitor42ato the input end of the carrier amplifier14is reduced. Also, since the inductor34ais connected in parallel between the other end and the midpoint of the output-side coil222a, the inductance component of the path for supplying the bias voltage Vb1 from the bypass capacitor42ato the input end of the carrier amplifier15is reduced. Therefore, the input impedances of the carrier amplifiers14and15in a low frequency band such as the baseband can be reduced. Also, since the inductor33bis connected in parallel between one end and the midpoint of the output-side coil222b, the inductance component of the path for supplying the bias voltage Vb2 from the bypass capacitor42bto the input end of the peak amplifier16is reduced. Also, since the inductor34bis connected in parallel between the other end and the midpoint of the output-side coil222b, the inductance component of the path for supplying the bias voltage Vb2 from the bypass capacitor42bto the input end of the peak amplifier17is reduced. Therefore, the input impedances of the peak amplifiers16and17in a low frequency band such as the baseband can be reduced.

Thus, for example, the intermodulation distortion component generated by mixing the baseband with the fundamental wave band of the high frequency signal can be suppressed, so that the deterioration of the ACLR of the high frequency signal in the fundamental wave band can be suppressed.

[1.7 Current Combining Type Doherty Amplifier Circuit According to Variation 4]

FIG.7Bis a circuit configuration diagram of an amplifier circuit10D according to Variation 4. The amplifier circuit10D includes carrier amplifiers14and15, peak amplifiers16and17, preamplifiers18and19, an output transformer21, input transformers22aand22b, bypass capacitors41,42aand42b, capacitors43,48,49aand49b, inductors31a,31b,32a,32b,33a,33b,34a,34b,37and38, a phase shift circuit60, a high frequency input terminal101, a high frequency output terminal102, a Vcc terminal103, and Vb terminals104aand104b. The amplifier circuit10D according to the present variation differs from the amplifier circuit10C according to Variation 3 in that the amplifier circuit10D is a voltage combining type Doherty amplifier circuit, while the amplifier circuit10C is a current combining type Doherty amplifier circuit. The amplifier circuit10D according to the present variation will be described with a focus on the differences from the amplifier circuit10C according to Variation 3.

The output transformer21includes an input-side coil211and an output-side coil212. One end of the input-side coil211is connected to the output end of the carrier amplifier14via the inductor37, and is connected to the output end of the peak amplifier16. The other end of the input-side coil211is connected to the output end of the carrier amplifier15via the inductor38, and is connected to the output end of the peak amplifier17. One end of the output-side coil212is connected to the high frequency output terminal102via the capacitor43, and the other end of the output-side coil212is connected to the ground. The input-side coil211and the output-side coil212are electromagnetically coupled to each other.

With the above configuration, a third high frequency balanced signal outputted from the carrier amplifier14and a first high frequency balanced signal outputted from the peak amplifier16are combined in current at one end of the input-side coil211, and a fourth high frequency balanced signal outputted from the carrier amplifier15and a second high frequency balanced signal outputted from the peak amplifier17are combined in current at the other end of the input-side coil211. The two high frequency balanced signals combined in current are combined in power by the output transformer21and outputted as a high frequency non-balanced signal from the high frequency output terminal102.

Note that it is sufficient that the inductors37and38are circuits for shifting the phase of signals; for example, the inductors37and38may be phase shifting lines.

The bypass capacitor41is an example of the first bypass capacitor, and one end (one electrode) of the bypass capacitor41is connected to the midpoint of the input-side coil211and the Vcc terminal103, and the other end (the other electrode) of the bypass capacitor41is connected to the ground. The bypass capacitor41has a function of suppressing the fundamental waves of the high frequency signals outputted from the carrier amplifiers14and15and the fundamental waves of the high frequency signals outputted from the peak amplifiers16and17from leaking into the power supply circuit.

The inductor31ais an example of the fifth inductor. One end of the inductor31ais connected to the output end of the carrier amplifier14and is connected to one end of the input-side coil211via the inductor37, and the other end of the inductor31ais connected to the midpoint of the input-side coil211. The inductor32ais an example of the sixth inductor. One end of the inductor32ais connected to the output end of the carrier amplifier15and is connected to the other end of the input-side coil211via the inductor38, and the other end of the inductor32ais connected to the midpoint of the input-side coil211.

The inductor31bis an example of the first inductor. One end of the inductor31bis connected to the output end of the peak amplifier16and one end of the input-side coil211, and the other end of the inductor31bis connected to the midpoint of the input-side coil211. The inductor32bis an example of the second inductor. One end of the inductor32bis connected to the output end of the peak amplifier17and the other end of the input-side coil211, and the other end of the inductor32bis connected to the midpoint of the input-side coil211.

Note that one end of the bypass capacitor41, the Vcc terminal103, the other end of the inductor31a, and the other end of the inductor32aare not limited to being connected to the midpoint of the input-side coil211, as long as they are connected to a node on the input-side coil211other than one end and the other end of the input-side coil211. Also, one end of the bypass capacitor41, the Vcc terminal103, the other end of the inductor31b, and the other end of the inductor32bare not limited to being connected to the midpoint of the input-side coil211, as long as they are connected to a node on the input-side coil211other than one end and the other end of the input-side coil211.

In the amplifier circuit10D according to the present variation, the preamplifiers18and19, the input transformers22aand22b, the bypass capacitors42aand42b, the Vb terminals104aand104b, the inductors33a,33b,34aand34b, and the capacitor43are not essential components.

In the amplifier circuit10D according to the present variation, the power supply voltage Vcc is supplied from the midpoint of the output transformer21to the output ends of the carrier amplifiers14and15and the peak amplifiers16and17by using the fact that the midpoint of the output transformer21is a virtual ground. Further, the bias voltage Vb1 is supplied from the midpoint of the input transformer22ato the input ends of the carrier amplifiers14and15by using the fact that the midpoint of the input transformer22ais a virtual ground. Further, the bias voltage Vb2 is supplied from the midpoint of the input transformer22bto the input ends of the peak amplifiers16and17by using the fact that the midpoint of the input transformer22bis a virtual ground.

With the above configuration, since the inductor31ais connected in parallel between one end and the midpoint of the input-side coil211, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the carrier amplifier14is reduced. In addition, since the inductor32ais connected in parallel between the other end and the midpoint of the input-side coil211, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the carrier amplifier15is reduced. Therefore, the output impedances of the carrier amplifiers14and15in a low frequency band such as the baseband can be reduced. In addition, since the inductor31bis connected in parallel between one end and the midpoint of the input-side coil211, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the peak amplifier16is reduced. In addition, since the inductor32bis connected in parallel between the other end and the midpoint of the input-side coil211, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output end of the peak amplifier17is reduced. Therefore, the output impedances of the peak amplifiers16and17in a low frequency band such as the baseband can be reduced.

Further, since the inductor33ais connected in parallel between one end and the midpoint of the output-side coil222a, the inductance component of the path for supplying the bias voltage Vb1 from the bypass capacitor42ato the input end of the carrier amplifier14is reduced. Also, since the inductor34ais connected in parallel between the other end and the midpoint of the output-side coil222a, the inductance component of the path for supplying the bias voltage Vb1 from the bypass capacitor42ato the input end of the carrier amplifier15is reduced. Therefore, the input impedances of the carrier amplifiers14and15in a low frequency band such as the baseband can be reduced. Also, since the inductor33bis connected in parallel between one end and the midpoint of the output-side coil222b, the inductance component of the path for supplying the bias voltage Vb2 from the bypass capacitor42bto the input end of the peak amplifier16is reduced. Also, since the inductor34bis connected in parallel between the other end and the midpoint of the output-side coil222b, the inductance component of the path for supplying the bias voltage Vb2 from the bypass capacitor42bto the input end of the peak amplifier17is reduced. Therefore, the input impedances of the peak amplifiers16and17in a low frequency band such as the baseband can be reduced.

Thus, for example, the intermodulation distortion component generated by mixing the baseband with the fundamental wave band of the high frequency signal can be suppressed, so that the deterioration of the ACLR of the high frequency signal in the fundamental wave band can be suppressed.

[2. Arrangement of Components of Amplifier Circuit]

Next, the arrangement of the components of the amplifier circuit10according to the embodiment will be described.

FIG.8is a plan view and a sectional view of the amplifier circuit10according to the embodiment. (a) ofFIG.8shows the arrangement of the circuit components assuming a main surface90aof a substrate90is viewed in a transparent manner from the positive direction side of a z-axis. (b) ofFIG.8is a sectional view taken along line VIII-VIII in (a) ofFIG.8. Note that, inFIG.8, some of the wires connecting the substrate90and each circuit component are omitted. The amplifier circuit10shown inFIG.8may further include a resin member covering the surface of the substrate90and a part of the circuit components, and a shield electrode layer covering the surface of the resin member; however, the resin member and the shield electrode layer are not shown inFIG.8.

In addition to the circuit configuration shown inFIG.1, the amplifier circuit10further includes the substrate90.

The substrate90has main surfaces90aand90bfacing each other, and is a substrate on which the circuit components constituting the amplifier circuit10are mounted. For example, a substrate having a multilayer structure formed by stacking a plurality of dielectric layers, a printed circuit board or the like can be used as the substrate90. Examples of the substrate having a multilayer structure formed by stacking a plurality of dielectric layers include an LTCC (Low Temperature Co-fired Ceramics) substrate, an HTCC (High Temperature Co-fired Ceramics) substrate, a substrate with built-in components, and a substrate having an RDL (Redistribution Layer).

As shown inFIG.8, the amplifiers11and12, the input transformer22, the inductors31to34, the bypass capacitor41, and the capacitor43are disposed on the main surface90aof the substrate90. The output transformer21is formed inside the substrate90.

The amplifiers11and12are included in a semiconductor IC80disposed on the main surface90a. The semiconductor IC80may be composed by using, for example, CMOS (Complementary Metal Oxide Semiconductor), and more specifically, may be manufactured by an SOI (Silicon on Insulator) process. The semiconductor IC may be composed of at least one of GaAs, SiGe, and GaN. Note that the semiconductor material of the semiconductor IC80is not limited to the above-described materials.

The input-side coil211and the output-side coil212constituting the output transformer21are composed of planar conductors formed inside the substrate90. Assuming the main surface90ais viewed in plan view, the input-side coil211and the output-side coil212at least partially overlap with each other. Note that the input-side coil211and the output-side coil212may at least partially be formed at least on the main surface90aor inside the substrate90.

The inductors31and32are surface-mounted components, and are disposed on the main surface90a.

Assuming the main surface90ais viewed in plan view, the inductors31and32are disposed in a region surrounded by the output transformer21.

With such a configuration, since the area of the component mounting region of the substrate90can be reduced, the amplifier circuit10can be reduced in size. In addition, the wiring connecting the inductors31and32and the midpoint of the input-side coil211can be shortened. Thus, the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output ends of the amplifiers11and12can be shortened, so that the inductance component in the path can be reduced, and the impedance in the low frequency band can be further reduced.

The input-side coil221and the output-side coil222constituting the input transformer22are composed of planar conductors formed between the main surface90aand the semiconductor IC80. Assuming the main surface90ais viewed in plan view, the input-side coil221and the output-side coil222at least partially overlap with each other.

The inductors33and34are composed of planar conductors formed between the main surface90aand the semiconductor IC80. Assuming the main surface90ais viewed in plan view, each of the inductors33and34may be a coil having a meander shape, a spiral shape, or a linear shape.

It is sufficient that each of the input-side coil221, the output-side coil222, and the inductors33and34is at least partially formed at least on the main surface90aor inside the substrate90, for example, may be formed on a surface of the semiconductor IC80facing the main surface90a.

Here, assuming the substrate90is viewed in plan view, the input-side coil221, the output-side coil222, and the inductors33and34overlap with the semiconductor IC80.

With such a configuration, since the area of the component mounting region of the main surface90acan be reduced, the amplifier circuit10can be reduced in size.

Alternatively, at least one of the input-side coil221, the output-side coil222, and the inductors33and34may be included in the semiconductor IC80. With such a configuration, the amplifier circuit10can be reduced in size.

Further, the bypass capacitors41and42may alternatively be surface-mounted components disposed on the main surface90aor90b.

[3. Effects and the Like]

As described above, the amplifier circuit10according to the present embodiment includes a high frequency input terminal101and a high frequency output terminal102, amplifiers11and12, an output transformer21having an input-side coil211and an output-side coil212, inductors31and32, and a bypass capacitor41. The output end of the amplifier11is connected to one end of the input-side coil211and one end of the inductor31. The output end of the amplifier12is connected to the other end of the input-side coil211and one end of the inductor32. The other end of the inductor31, the other end of the inductor32, and one end of the bypass capacitor41are connected to the midpoint of the input-side coil211. One end of the output-side coil212is connected to the high frequency output terminal102. The other end of the bypass capacitor41and the other end of the output-side coil212are connected to the ground.

With such a configuration, since the inductor31is connected in parallel between one end and the midpoint of the input-side coil211, the inductance component of a path from the bypass capacitor41to the output end of the amplifier11can be reduced. Also, since the inductor32is connected in parallel between the other end and the midpoint of the input-side coil211, the inductance component of a path from the bypass capacitor41to the output end of the amplifier12can be reduced. Thus, the output impedance of the amplifiers11and12in a low frequency band such as the baseband can be reduced. Therefore, a differential amplification type amplifier circuit10in which the impedance in the low frequency band is reduced can be provided.

For example, the amplifier circuit10may further include a Vcc terminal103connected to the input-side coil211.

With such a configuration, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output ends of the amplifiers11and12can be reduced.

For example, the amplifier circuit10may further include an input transformer22having an input-side coil221and an output-side coil222, inductors33and34, and a bypass capacitor42, in which the input end of the amplifier11is connected to one end of the output-side coil222and one end of the inductor33, the input end of the amplifier12is connected to the other end of the output-side coil222and one end of the inductor34, the other end of the inductor33, the other end of the inductor34, and one end of the bypass capacitor42are connected to the midpoint of the output-side coil222, one end of the input-side coil221is connected to the high frequency input terminal101, and the other end of the bypass capacitor42and the other end of the input-side coil221are connected to the ground.

With such a configuration, since the inductor33is connected in parallel between one end and the midpoint of the output-side coil222, the inductance component of a path from the bypass capacitor42to the input end of the amplifier11can be reduced. Also, since the inductor34is connected in parallel between the other end and the midpoint of the output-side coil222, the inductance component of a path from the bypass capacitor42to the input end of the amplifier12can be reduced. Thus, the input impedance of the amplifiers11and12in a low frequency band such as the baseband can be reduced.

For example, the amplifier circuit10may further include a Vb terminal104connected to the output-side coil222.

With such a configuration, the inductance component of the path for supplying the bias voltage Vb from the bypass capacitor42to the input ends of the amplifiers11and12can be reduced.

For example, the amplifier circuit10A according to Variation 1 may further include a capacitor44connected between the other ends of the inductor31and inductor32and the ground.

With such a configuration, in addition to the inductors31and32, by grounding the midpoint of the input-side coil211in a more high frequency manner by the capacitor44, the impedance in a low frequency band such as the baseband can be further reduced, so that the memory effect can be further suppressed.

For example, the amplifier circuit10A according to Variation 1 may further include a capacitor45connected between the other ends of the inductor33and inductor34and the ground.

With such a configuration, in addition to the inductors33and34, by grounding the midpoint of the output-side coil222in a more high-frequency manner by the capacitor45, the impedance in a low frequency band such as the baseband can be further reduced, so that the memory effect can be further suppressed.

For example, the amplifier circuit10B according to Variation 2 may further include a first LC series circuit that is connected between the output end of the amplifier11and the ground and that is formed by connecting a inductor35and a capacitor46in series, and a second LC series circuit that is connected between the output end of the amplifier12and the ground and that is formed by connecting a inductor36and a capacitor47in series.

With such a configuration, since the high-order harmonic components can be short-circuited by the first LC series circuit and the second LC series circuit, particularly second-order harmonic components can be suppressed.

For example, the amplifier circuit10may further includes a substrate90, in which at least a part of the output transformer21is formed at least inside the substrate90or on the surface of the substrate90, each of the inductors31and32is a surface-mounted component disposed on the substrate90, and assuming the substrate90is viewed in plan view, the inductors31and32are disposed in a region surrounded by the output transformer21.

With such a configuration, since the area of the component mounting region of the substrate90can be reduced, the amplifier circuit10can be reduced in size. In addition, the wiring connecting the inductors31and32and the midpoint of the input-side coil211can be shortened. Thus, the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output ends of the amplifiers11and12can be shortened, so that the inductance component in the path can be reduced, and the impedance in a low frequency band can be reduced.

For example, in the amplifier circuit10, the amplifiers11and12may be included in a semiconductor IC80disposed on the substrate90, in which at least a part of the input transformer22, at least a part of the inductor33, and at least a part of the inductor34are formed at least inside the substrate90or on the surface of the substrate90, and assuming the substrate90is viewed in plan view, the input transformer22and the inductors33and34overlap with the semiconductor IC80.

With such a configuration, since the area of the component mounting region of the substrate90can be reduced, the amplifier circuit10can be reduced in size.

For example, in the amplifier circuit10, the amplifiers11and12, the input transformer22, and the inductors33and34may be included in the semiconductor IC80disposed on the substrate90.

With such a configuration, the amplifier circuit10can be reduced in size.

Further, for example, the amplifier circuit10C according to Variation 3 and the amplifier circuit10D according to Variation 4 include a high frequency input terminal101and a high frequency output terminal102, peak amplifiers16and17, an output transformer21b(or21) having an input-side coil211b(or211) and an output-side coil212b(or212), inductors31band32b, and a bypass capacitor41, in which the output end of the peak amplifier16is connected to one end of the input-side coil211b(or211) and one end of the inductor31b, the output end of the peak amplifier17is connected to the other end of the input-side coil211b(or211) and one end of the inductor32b, the other end of the inductor31b, the other end of the inductor32b, and one end of the bypass capacitor41are connected to the midpoint of the input-side coil211b(or211), and one end of the output-side coil212b(or212) is connected to the high frequency output terminal102, and the other end of the bypass capacitor41and the other end of the output-side coil212are connected to the ground. The amplifier circuits10C and10D may further include carrier amplifiers14and15and inductors31aand32a, in which the output end of the carrier amplifier14is connected to one end of the inductor31a, the output end of the carrier amplifier15is connected to one end of the inductor32a, and the other end of the inductor31aand the other end of the inductor32aare connected to one end of the bypass capacitor41and the input-side coil211b(or211).

With such a configuration, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output ends of the carrier amplifiers14and15can be reduced. Thus, the output impedance of the carrier amplifiers14and15in a low frequency band such as the baseband can be reduced. Further, the inductance component of the path for supplying the power supply voltage Vcc from the bypass capacitor41to the output ends of the peak amplifiers16and17can be reduced. Thus, the output impedance of the peak amplifiers16and17in a low frequency band such as the baseband can be reduced. Therefore, it is possible to provide a Doherty amplifier circuit in which the intermodulation distortion component generated by mixing the baseband with the fundamental wave band of the high frequency signal is suppressed, and the deterioration of the ACLR of the high frequency signal in the fundamental wave band is suppressed.

For example, the amplifier circuits10C and10D further include an input transformer22bhaving an input-side coil221band an output-side coil222b, inductors33band34b, and a bypass capacitor42b, in which the input end of the peak amplifier16is connected to one end of the output-side coil222band one end of the inductor33b, the input end of the peak amplifier17is connected to the other end of the output-side coil222band one end of the inductor34b, the other end of the inductor33b, the other end of the inductor34b, and one end of the bypass capacitor42bare connected to the midpoint of the output-side coil222b, one end of the input-side coil221bis connected to the high frequency input terminal101, and the other end of the bypass capacitor42band the other end of the input-side coil221bare connected to the ground. The amplifier circuits10C and10D may further include an input transformer22ahaving an input-side coil221aand an output-side coil222a, inductors33aand34a, and a bypass capacitor42a, in which the input end of the carrier amplifier14is connected to one end of the output-side coil222aand one end of the inductor33a, the input end of the carrier amplifier15is connected to the other end of the output-side coil222aand one end of the inductor34a, the other end of the inductor33a, the other end of the inductor34a, and one end of the bypass capacitor42aare connected to the output-side coil222a, and the other end of the bypass capacitor42ais connected to the ground.

With such a configuration, the inductance component of the path for supplying the bias voltage Vb1 from the bypass capacitor42ato the input ends of the carrier amplifiers14and15can be reduced. Thus, the input impedance of the carrier amplifiers14and15in a low frequency band such as the baseband can be reduced. Further, the inductance component of the path for supplying the bias voltage Vb2 from the bypass capacitor42bto the input ends of the peak amplifiers16and17can be reduced. Thus, the input impedance of the peak amplifiers16and17in a low frequency band such as the baseband can be reduced. Therefore, it is possible to provide a Doherty amplifier circuit in which the intermodulation distortion component generated by mixing the baseband with the fundamental wave band of the high frequency signal is suppressed, and the deterioration of the ACLR of the high frequency signal in the fundamental wave band is suppressed.

The communication device4according to the present embodiment includes the RFIC3that processes a high frequency signal, and the amplifier circuit10that transmits the high frequency signal between the RFIC3and the antenna2.

With such a configuration, the effects of the amplifier circuit10can be realized in the communication device4.

Other Embodiments and the Like

The amplifier circuit and the communication device according to the embodiment of the present disclosure have been described with reference to the embodiment and the variations; however, the amplifier circuit and the communication device according to the present disclosure are not limited to the embodiment and the variations described above. The present disclosure also includes other embodiments realized by combining any components of the above embodiment and the variations, modified examples obtained by applying various modifications that a person skilled in the art can think of to the above embodiment and the variations without departing from the spirit of the present disclosure, and various apparatuses incorporating the above amplifier circuit and the communication device.

For example, in the amplifier circuit and the communication device according to the above embodiment and variations, other circuit elements and wiring may be inserted between the paths connecting the circuit elements and the signal paths disclosed in the drawings.

Features of the amplifier circuit and the communication device according to each of the above embodiments will be described below.

An amplifier circuit comprising:a high frequency input terminal and a high frequency output terminal;a first amplifying element and a second amplifying element;an output transformer having a first input-side coil and a first output-side coil;a first inductor and a second inductor; anda first bypass capacitor,whereinan output end of the first amplifying element is connected to one end of the first input-side coil and one end of the first inductor,an output end of the second amplifying element is connected to an other end of the first input-side coil and one end of the second inductor,an other end of the first inductor, an other end of the second inductor, and one end of the first bypass capacitor are connected to the first input-side coil,one end of the first output-side coil is connected to the high frequency output terminal, andan other end of the first bypass capacitor and an other end of the first output-side coil are connected to a ground.
<2>

The amplifier circuit according to <1>, further comprising:a power supply voltage supply terminal connected to the first input-side coil.
<3>

The amplifier circuit according to <1> or <2>, further comprising:a first input transformer having a second input-side coil and a second output-side coil;a third inductor and a fourth inductor; anda second bypass capacitor,whereinan input end of the first amplifying element is connected to one end of the second output-side coil and one end of the third inductor,an input end of the second amplifying element is connected to an other end of the second output-side coil and one end of the fourth inductor,an other end of the third inductor, an other end of the fourth inductor, and one end of the second bypass capacitor are connected to the second output-side coil,one end of the second input-side coil is connected to the high frequency input terminal, andan other end of the second bypass capacitor and an other end of the second input-side coil are connected to the ground.
<4>

The amplifier circuit according to <3>, further comprising:a bias voltage supply terminal connected to the second output-side coil.
<5>

The amplifier circuit according to any one of <1> to <4>, further comprising:a first capacitor connected between the other ends of the first inductor and second inductor and the ground.
<6>

The amplifier circuit according to <3> or <4>, further comprising:a second capacitor connected between the other ends of the third inductor and fourth inductor and the ground.
<7>

The amplifier circuit according to any one of <1> to <6>, further comprising:a first LC series circuit that is connected between the output end of the first amplifying element and the ground and that is formed by connecting an inductor and a capacitor in series; anda second LC series circuit that is connected between the output end of the second amplifying element and the ground and that is formed by connecting an inductor and a capacitor in series.
<8>

The amplifier circuit according to <3> or <4>, further comprising:a substrate,whereinat least a part of the output transformer is formed at least inside the substrate or on a surface of the substrate,each of the first inductor and the second inductor is a surface-mounted component disposed on the substrate, andassuming the substrate is viewed in plan view, the first inductor and the second inductor are disposed in a region surrounded by the output transformer.
<9>

The amplifier circuit according to <8>, whereinthe first amplifying element and the second amplifying element are included in a semiconductor IC disposed on the substrate,at least a part of the first input transformer, at least a part of the third inductor, and at least a part of the fourth inductor are formed at least inside the substrate or on the surface of the substrate, andassuming the substrate is viewed in plan view, the first input transformer, the third inductor, and the fourth inductor overlap with the semiconductor IC.
<10>

The amplifier circuit according to <8>, wherein the first amplifying element, the second amplifying element, the first input transformer, the third inductor, and the fourth inductor are included in a semiconductor IC disposed on the substrate.

The amplifier circuit according to any one of <1> to <10>, further comprising:a third amplifying element and a fourth amplifying element; anda fifth inductor and a sixth inductor,whereinan output end of the third amplifying element is connected to one end of the fifth inductor,an output end of the fourth amplifying element is connected to one end of the sixth inductor, andan other end of the fifth inductor and an other end of the sixth inductor are connected to the one end of the first bypass capacitor and the first input-side coil.
<12>

The amplifier circuit according to <11>, further comprising:a second input transformer having a third input-side coil and a third output-side coil;a seventh inductor and an eighth inductor; anda third bypass capacitor,whereinan input end of the third amplifying element is connected to one end of the third output-side coil and one end of the seventh inductor,an input end of the fourth amplifying element is connected to an other end of the third output-side coil and one end of the eighth inductor,an other end of the seventh inductor, an other end of the eighth inductor, and one end of the third bypass capacitor are connected to the third output-side coil, andan other end of the third bypass capacitor is connected to the ground.
<13>

A communication device comprising:a signal processing circuit that processes a high frequency signal; andthe amplifier circuit according to any one of <1> to <12> that transmits the high frequency signal between the signal processing circuit and an antenna.

INDUSTRIAL APPLICABILITY

The present disclosure, as an amplifier circuit and a communication device arranged in a front-end section, can be widely used in communication devices such as cellular phones.

REFERENCE SIGNS LIST