Power amplification circuit

Abstract

The present invention achieves a wide-band characteristic even if the impedance when the output side is viewed from output terminals of a carrier amplifier and a peak amplifier that constitute a Doherty amplifier is low. This power amplification circuit includes: a carrier amplifier and a peak amplifier that constitute a Doherty amplification circuit; a first transformer that has a primary winding connected to an output terminal of the carrier amplifier; a second transformer that has a primary winding connected to an output terminal of the peak amplifier; a signal line that connects one terminal of a secondary winding of the first transformer and one terminal of a secondary winding of the second transformer; a first capacitor; and second and third capacitors connected to the primary windings of the first and second transformers. One terminal of the first capacitor is connected to the signal line and the other terminal of the first capacitor is connected to a reference potential. The power amplification circuit satisfies expression (1) where CT is the sum of the capacitance values of the first capacitor and the signal line, ω0 is an angular frequency, and ZM is a load impedance.

Description

Power Amplifier Circuit

[0001] The present invention relates to a power amplifier circuit.

[0002] A power amplifier circuit having a Doherty amplifier configuration is disclosed in Non-Patent Document 1. Fig. 6 of Non-Patent Document 1 shows a conventional power amplifier circuit. The power amplifier circuit described in Non-Patent Document 1 has a configuration in which a converter that can be regarded as a current source is connected to the output side of a peak amplifier, and a converter that can be regarded as a voltage source is connected to the output side of a carrier amplifier. Non-Patent Document 1 discloses that this configuration makes it possible to obtain a Doherty amplifier with a wide matching ratio bandwidth.

[0003] Shohei Imai et al. “Bandwidth_Optimization_of_Doherty_Power_Amplifier_Based_on_Source_Converters_for_5G_Mobile_Handsets”, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL.70, NO.1, JANUARY 2022

[0004] In the power amplifier circuit described in Non-Patent Document 1, the converter that can be regarded as a current source is a converter that outputs a high impedance while maintaining the high impedance. On the other hand, the converter that can be regarded as a voltage source is a converter that converts a high impedance into a low impedance and outputs the low impedance. When the impedance seen from the output terminal of the carrier amplifier and the peak amplifier to the output side is low, there is a problem that it is difficult to obtain good characteristics over a wide frequency band, i.e., to realize wideband characteristics, due to the limitations of the conversion ratio of the converter.

[0005] The present disclosure has been made in view of the above, and its purpose is to provide a power amplifier circuit that can achieve wideband characteristics even when the impedance seen from the output terminal of the carrier amplifier and peak amplifier that constitute the Doherty amplifier is low on the output side.

[0006] In order to solve the above-mentioned problems and achieve the object, a power amplifier circuit according to an aspect of the present disclosure includes a carrier amplifier and a peak amplifier constituting a Doherty amplifier circuit, a first transformer having a primary side connected to an output terminal of the carrier amplifier, a second transformer having a primary side connected to an output terminal of the peak amplifier, a signal line connecting one end of the secondary side of the first transformer to one end of the secondary side of the second transformer, and a first capacitor, one end of the first capacitor is connected to the signal line and the other end of the first capacitor is connected to a reference potential, and a sum of capacitance values ​​of the first capacitor and the signal line is defined as C Ｔ and the frequency to be used is ω ０ (ω ０ = 2πf), and the load impedance is Z M When this is the case, the formula (1) is satisfied.

[0007] According to the present disclosure, wideband characteristics can be achieved even when the impedance seen from the output terminal of the carrier amplifier and peak amplifier constituting the Doherty amplifier is low.

[0008] Fig. 1 is a block diagram showing a power amplifier circuit according to a first embodiment of the present disclosure. Fig. 2 is a block diagram showing a power amplifier circuit according to a second embodiment of the present disclosure. Fig. 3 is a block diagram showing a power amplifier circuit according to a third embodiment of the present disclosure. Fig. 4 is a block diagram showing a power amplifier circuit according to a fourth embodiment of the present disclosure. Fig. 5 is a diagram showing an example of a matching ratio bandwidth with respect to a transformer coupling coefficient. Fig. 6 is a diagram showing the relationship between the carrier-side and peak-side transformer coupling coefficients and a matching ratio bandwidth.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment, components that are the same as or equivalent to those in other embodiments will be given the same reference numerals, and their description will be simplified or omitted. The present invention is not limited to each embodiment. Furthermore, the components of each embodiment include those that are easily replaceable by those skilled in the art, or those that are substantially the same. Note that the configurations described below can be combined as appropriate. Furthermore, the configurations can be omitted, replaced, or modified within the scope of the gist of the invention.

[0010] (First Embodiment) (Configuration) Fig. 1 is a diagram showing a power amplifier circuit 100 according to a first embodiment of the present disclosure. As shown in Fig. 1, the power amplifier circuit 100 according to the first embodiment includes an input terminal 10, an output terminal 20, a divider 110, a carrier amplifier 120, a peak amplifier 130, a converter 140, a converter 150, a connection unit 160, and a matching circuit 200. The power amplifier circuit 100 is mounted in, for example, a mobile phone and is used to amplify the power of a signal to be transmitted to a base station. The power amplifier circuit 100 can amplify the power of signals of communication standards such as 2G (second generation mobile communication system), 3G (third generation mobile communication system), 4G (fourth generation mobile communication system), 5G (fifth generation mobile communication system), LTE (Long Term Evolution)-FDD (Frequency Division Duplex), LTE-TDD (Time Division Duplex), LTE-Advanced, and LTE-Advanced Pro. Note that the communication standards of the signals amplified by the power amplifier circuit 100 are not limited to these.

[0011] The input terminal 10 is a terminal for inputting an input signal RFin, and the output terminal 20 is a terminal for outputting an output signal RFout.

[0012] The power amplifier circuit 100 amplifies an input signal RFin input to an input terminal 10 and outputs an output signal RFout from an output terminal 20. The input signal RFin is a radio frequency (RF) signal. The frequency of the input signal RFin is, for example, about several GHz.

[0013] The divider 110 divides the input signal RFin into, for example, a signal RFin_a and a signal RFin_b whose phase is approximately 90 degrees ahead of the signal RFin_a. Here, "approximately 90 degrees" refers to a phase within a range of 90 degrees ±45 degrees. In this embodiment, since the carrier amplifier 120 and the peak amplifier 130 are differential amplifiers, as will be described later, the signals RFin_a and RFin_b are further divided into two input signals whose phases differ by approximately 180 degrees. Here, "approximately 180 degrees" refers to a phase within a range of 180 degrees ±45 degrees. While FIG. 1 illustrates a configuration in which the divider 110 is formed using a signal line, the configuration of the divider is not limited to this. For example, the divider may be formed using a transmission line, a 90-degree coupler, a transformer, or the like.

[0014] The carrier amplifier 120 and the peak amplifier 130 constitute a Doherty amplifier. The carrier amplifier 120 amplifies and outputs, for example, an input signal RFin_a. The peak amplifier 130 amplifies and outputs an input signal RFin_b. In this embodiment, for example, the carrier amplifier 120 is biased to be class AB, and the peak amplifier 130 is biased to be class AB or class C, which is a level different from the level to which the carrier amplifier 120 is biased.

[0015] That is, the carrier amplifier 120 operates in a range where the power level is equal to or greater than zero, regardless of the power level of the input signal RFin. On the other hand, the peak amplifier 130 operates in a range where the voltage level of the input signal RFin is equal to or greater than a level Vback that is a predetermined level lower than the maximum level Vmax. In other words, the peak amplifier 130 operates in a range where the power level of the input signal RFin is equal to or greater than zero and a predetermined level (e.g., about 6 dB) lower than the maximum level. In this way, by combining the operations of the two amplifiers according to the power level of the input signal, the range in which the carrier amplifier 120 operates at saturated output is expanded. Therefore, power efficiency is improved compared to a power amplifier circuit composed of only one amplifier.

[0016] The carrier amplifier 120 and the peak amplifier 130 are each configured as a differential amplifier. The differential amplifier includes two paired amplifier elements. The carrier amplifier 120 includes a positive-side amplifier element 121 and a negative-side amplifier element 122. The peak amplifier 130 includes a positive-side amplifier element 131 and a negative-side amplifier element 132. Because the carrier amplifier 120 and the peak amplifier 130 are differential amplifiers, they amplify and output the potential difference between signals of the same amplitude and opposite phase input to each of the two amplifier elements. Therefore, when signals of the same amplitude and phase (e.g., noise, etc.) are simultaneously input to each of the two amplifier elements, these signals of the same amplitude and phase cancel each other out. In other words, using differential amplifiers for the carrier amplifier 120 and the peak amplifier 130 can suppress the generation of noise and harmonics of the input signal.

[0017] The amplifying element included in the differential amplifier is not particularly limited, but may be, for example, a bipolar transistor such as a heterojunction bipolar transistor (HBT), or a field effect transistor such as a metal-oxide-semiconductor field effect transistor (MOSFET).

[0018] The converter 140 is connected to the output side of the carrier amplifier 120. The converter 150 is connected to the output side of the peak amplifier 130. The converters 140 and 150 convert, for example, the characteristics (impedance, phase, etc.) of the carrier amplifier 120 and the peak amplifier 130, and output the amplified power toward the output terminal 20.

[0019] The converter 140 includes a transformer 141, which is a first transformer, and a capacitor 142. The transformer 141 includes an input winding (i.e., a primary winding) 141a and an output winding (i.e., a secondary winding) 141b. In the transformer 141, the input winding 141a and the output winding 141b are electromagnetically coupled, and the coupling coefficient is kc.

[0020] The capacitor 142 is connected in parallel to the input winding 141 a. One end of the input winding 141 a is connected to the output end of the amplifying element 121. The other end of the input winding 141 a is connected to the output end of the amplifying element 122. One end of the output winding 141 b is connected to the connection part 160. The other end of the output winding 141 b is connected to the matching circuit 200.

[0021] The converter 150 includes a transformer 151, which is a second transformer, and a capacitor 152. The transformer 151 includes an input winding (i.e., a primary winding) 151a and an output winding (i.e., a secondary winding) 151b. In the transformer 151, the input winding 151a and the output winding 151b are electromagnetically coupled, and the coupling coefficient is kp.

[0022] The capacitor 152 is connected in parallel to the input winding 151a. One end of the input winding 151a is connected to the output terminal of the amplifier element 121. The other end of the input winding 151a is connected to the output terminal of the amplifier element 122. One end of the output winding 151b is connected to a connection unit 160. The other end of the output winding 151b is connected to a reference potential. The connection unit 160 has the function of connecting the converter 140 that can be regarded as a current source and the converter 150 that can be regarded as a current source. Details of the converter that can be regarded as a current source are disclosed in Non-Patent Document 1, and will not be described here.

[0023] The matching circuit 200 is provided between the other end of the output-side winding 141b of the converter 140 and the output terminal 20. That is, the other end of the output-side winding 141b of the converter 140 is connected to the output terminal 20 via the matching circuit 200. The matching circuit 200 is a matching circuit that includes, for example, a TLT (Transmission Line Transformer).

[0024] The connection unit 160 includes a signal line 161 and a capacitor 162. The signal line 161 electrically connects the output winding 141b of the converter 140 and the output winding 151b of the converter 150. The signal line 161 electrically connects one end of the output winding 141b of the converter 140 and one end of the output winding 151b of the converter 150. One end of the capacitor 162 is connected to the signal line 161. The other end of the capacitor 162 is connected to the reference potential.

[0025] (Effects) According to the power amplifier circuit 100 of the first embodiment, wideband characteristics can be achieved even when the impedances Z1 and Z2 are low when viewed from the output ends of the carrier amplifier 120 and the peak amplifier 130. Details of the effects and the conditions for achieving these effects will be described later.

[0026] Second Embodiment (Configuration) Fig. 2 is a diagram showing a power amplifier circuit 100a according to a second embodiment of the present disclosure. The power amplifier circuit 100a according to this embodiment differs from the power amplifier circuit 100 according to the first embodiment in that a connecting portion 160a is used instead of the connecting portion 160. The connecting portion 160a includes inductors 163 and 164. In other words, the power amplifier circuit 100a according to this embodiment has a configuration in which the inductors 163 and 164 are added to the power amplifier circuit 100 according to the first embodiment.

[0027] (Effect) According to the power amplifier circuit 100a of the second embodiment, wideband characteristics can be achieved even when the impedances Z1 and Z2 are low when viewed from the output ends of the carrier amplifier 120 and the peak amplifier 130. Details of the effect and the conditions for achieving this effect will be described later.

[0028] (Third Embodiment) (Configuration) FIG. 3 is a diagram showing a power amplifier circuit 100b according to a third embodiment of the present disclosure. The power amplifier circuit 100b according to this embodiment differs from the power amplifier circuit 100 according to the first embodiment in that a connection portion 160b is used instead of the connection portion 160. The connection portion 160b includes capacitors 143 and 153. That is, the power amplifier circuit 100b according to this embodiment has a configuration in which the capacitors 143 and 153 are added to the power amplifier circuit 100 according to the first embodiment. The capacitor 143 can also be considered a component of the converter 140a. The converter 140a has a configuration in which the capacitor 143 is added to the converter 140 of the power amplifier circuit 100. The capacitor 153 can also be considered a component of the converter 150a. The converter 150a has a configuration in which the capacitor 153 is added to the converter 150 of the power amplifier circuit 100.

[0029] (Effects) According to the power amplifier circuit 100b of the third embodiment, wideband characteristics can be achieved even when the impedances Z1 and Z2 are low when viewed from the output ends of the carrier amplifier 120 and the peak amplifier 130. Details of the effects and the conditions for achieving these effects will be described later.

[0030] 4 is a diagram showing a power amplifier circuit 100c according to a fourth embodiment of the present disclosure. The power amplifier circuit 100c according to this embodiment differs from the power amplifier circuit 100 according to the first embodiment in that a converter 140a is used instead of the converter 140, a converter 150a is used instead of the converter 150, and a connection unit 160c is used instead of the connection unit 160.

[0031] The converter 140a has a capacitor 143. The converter 140a has a configuration in which the capacitor 143 is added to the converter 140 of the power amplifier circuit 100. The converter 150a has a capacitor 153. The converter 150a has a configuration in which the capacitor 153 is added to the converter 150 of the power amplifier circuit 100.

[0032] The connecting portion 160c includes inductors 163 and 164. One end of the inductor 163 is connected to the capacitor 143. The other end of the inductor 163 is connected to one end of the capacitor 162. One end of the inductor 164 is connected to the capacitor 153. The other end of the inductor 164 is connected to one end of the capacitor 162. The other end of the capacitor 162 is connected to a reference potential.

[0033] (Effect) According to the power amplifier circuit 100c of the fourth embodiment, wideband characteristics can be achieved even when the impedances Z1 and Z2 are low when viewed from the output ends of the carrier amplifier 120 and the peak amplifier 130. Details of the effect and the conditions for achieving this effect will be described later.

[0034] Next, the conditions for realizing each of the above-described embodiments will be described. To realize each embodiment, the conditions of the following formulas must be satisfied.

[0035] (Conditions for Realizing the First Embodiment) In order to realize the first embodiment, the following formula (1) must be satisfied. In formula (1), the sum of the capacitance values ​​of the capacitors 162 is C Ｔ and the angular frequency is ω ０ (2πf), and the load impedance seen from the output winding 141b of the converter 140 to the load side is Z M However, the total C Ｔ includes the capacitance of the signal line 161 relative to the reference potential. The frequency f used to calculate the angular frequency ω0 is the frequency used in the power amplifier circuit 100c, such as the frequency of the signal input to the power amplifier circuit 100c. By satisfying formula (1), the sum C Ｔ is approximately within the range of ±50% of the load impedance at the frequency used, making it possible to realize the first embodiment.

[0036] Furthermore, the following formula (2) must be satisfied: In formula (2), the ratio Z tar / Z M is the load impedance Z M Target impedance Z tarThe ratio of the load impedance Z M is the impedance seen from the transducer 140 to the output terminal 20 in FIG. 1. By satisfying equation (2), the coupling coefficients kc and kp are included in the range of 0.35≦k≦0.95, which allows for wideband characteristics to be realized as described later. Therefore, in the first embodiment, it is possible to realize a wide matching ratio bandwidth. Furthermore, in equation (2), the ratio Z tar / Z M is 0.09<Z tar / Z M <8.64, the coupling coefficients kc and kp will be within the range of 0.4≦k≦0.85, which will enable the realization of wider bandwidth characteristics and a wider matching ratio bandwidth than conventional techniques, as will be described later.

[0037] In addition, in formula (2), Z tar can be roughly calculated by the following equation (3). However, in formula (3), V cc is the supply voltage, P out is the saturated output voltage, and both are measurable values. cell is the number of amplifiers that make up the amplifier, which is a fixed value of "4" in this example. LOSS is measurable in the range of 80% to 90% (i.e., 0.8 to 0.9) as a general value, with a typical value being 85% (0.85).

[0038] (Conditions for Realizing the Second Embodiment) In order to realize the second embodiment, it is necessary to satisfy the above formula (1) and the following formula (4).

[0039] In equation (4), the inductance value L Ｔ' is the inductance value of each of the inductors 163 and 164. In equation (4), C1 is the capacitance value of each of the capacitors 142 and 152. By satisfying equation (4), the coupling coefficients kc and kp fall within the range of 0.35≦k<1.0, which allows for wideband characteristics to be achieved, as described below. Therefore, in the second embodiment, a wide matching ratio bandwidth can be achieved. Furthermore, by satisfying equation (4) with the right-hand side set to 2.60, the coupling coefficients kc and kp fall within the range of k≦0.85, which allows for a wider matching ratio bandwidth than conventional techniques to be achieved, as described below.

[0040] (Conditions for Realizing the Third Embodiment) In order to realize the third embodiment, it is necessary to satisfy the above formula (1) and the following formula (5).

[0041] In equation (5), C1 is the capacitance value of each of the capacitors 142 and 152. If the capacitance value of the capacitor 153 is C2, then C2′=C2 / (1−ω ０ ２ L Ｔ C ２ ) By satisfying equation (5), the coupling coefficients kc and kp fall within the range of 0.35≦k≦0.95, which allows for wideband characteristics to be realized as described below. Therefore, in the third embodiment, a wide matching ratio bandwidth can be realized. Furthermore, by satisfying equation (4) with the left side set to 0.19, the coupling coefficients kc and kp fall within the range of 0.4≦k, which allows for more reliable wideband characteristics to be realized as described below.

[0042] (Conditions for Realizing the Fourth Embodiment) To realize the fourth embodiment, the connecting portion 160c needs to operate as a quarter-wave line. The quarter-wave line is realized by the inductors 163 and 164 and the capacitor 162, which are lumped components, and the operation as a Doherty amplifier can be realized.

[0043] (Relationship between Transformer Coupling Coefficient and Matching Ratio Bandwidth) FIG. 5 is a diagram showing an example of the matching ratio bandwidth versus the transformer coupling coefficient. FIG. 5 corresponds to FIG. 16 in Non-Patent Document 1. In FIG. 5, the horizontal axis represents the coupling coefficient kc between the input winding 141a and output winding 141b of the carrier-side transformer 141, and the vertical axis represents the coupling coefficient kp between the input winding 151a and output winding 151b of the peak-side transformer 151. According to FIG. 5 and the description in Non-Patent Document 1, a matching ratio bandwidth of at least 7.5% can be achieved in conventional power amplifier circuits. In other words, a matching ratio bandwidth of 7.5% or more can achieve characteristics equivalent to those in Non-Patent Document 1, i.e., what is referred to as wideband characteristics in Non-Patent Document 1. The matching ratio bandwidth is the value (%) obtained by dividing the difference between the upper and lower limits of the frequency band by the average value of the upper and lower limits.

[0044] Fig. 6 is a diagram showing the relationship between the coupling coefficient k and the matched ratio bandwidth when it is assumed that the coupling coefficients of the carrier-side and peak-side transformers are the same. The dashed line in Fig. 6 indicates the relationship between the coupling coefficient and the matched ratio bandwidth in the circuit configuration described in Fig. 6 of Non-Patent Document 1. The solid line in Fig. 6 indicates the relationship between the coupling coefficient and the matched ratio bandwidth in the power amplifier circuit of the present disclosure (specifically, the power amplifier circuit 100c according to the fourth embodiment). The dashed line in Fig. 6 corresponds to a matched ratio bandwidth of 7.5%. Note that in Fig. 6, the characteristics of the circuit described in Fig. 6 of Non-Patent Document 1, shown by the dashed line, and the characteristics of the power amplifier circuit of the present disclosure were calculated under the same conditions set for the relevant parameters of each circuit as shown below. That is, the target impedance Z tar is 5 Ω, the design center frequency f0 is 3.75 GHz, and the load impedance Z M Each parameter was calculated with the inductance product ζ set to 27.2Ω and the inductance product ζ set to 16.5Ω.

[0045] As described above, it can be said that wideband characteristics can be achieved when the matching ratio bandwidth is greater than 7.5%. Therefore, as shown by the dashed line in Figure 6, in the case of the circuit configuration described in Figure 6 of Non-Patent Document 1, wideband characteristics can be achieved when the coupling coefficient k is approximately 0.57 or greater. In contrast, as shown by the solid line in Figure 6, in the case of the power amplifier circuit of the present disclosure, wideband characteristics can be achieved when the coupling coefficient k is approximately 0.35 or greater. In other words, the power amplifier circuit of the present disclosure can achieve wideband characteristics even with a lower coupling coefficient. In other words, the power amplifier circuit of the present disclosure can achieve wideband characteristics even when the impedances Z1 and Z2 seen from the output ends of the carrier amplifier 120 and the peak amplifier 130 to the output side are low.

[0046] Here, the upper limit of the coupling coefficient is theoretically 1.0. It can be seen that the power amplifier circuit of the present disclosure can achieve better characteristics than the circuit configuration of Non-Patent Document 1 even at a coupling coefficient of approximately 0.95, which is close to the upper limit. From the above, it can be seen that the power amplifier circuit of the present disclosure can achieve a matching ratio bandwidth equal to or better than that of a conventional power amplifier circuit when the coupling coefficient k is greater than or equal to 0.35 and less than 1.0. Furthermore, it can be seen that the power amplifier circuit of the present disclosure can achieve a wider matching ratio bandwidth than a conventional power amplifier circuit when the coupling coefficient is in the range of 0.35 to 0.95. Furthermore, it can be seen that when the coupling coefficient is in the range of 0.4 or greater, it can reliably achieve better characteristics than the circuit configuration of Non-Patent Document 1. Furthermore, when the coupling coefficient is in the range of 0.85 or less, it can achieve a matching ratio bandwidth that is approximately 5 points wider than that of a conventional power amplifier circuit, indicating a relatively large width of the matching ratio bandwidth.

[0047] The present disclosure may take the following forms with respect to the recitation of claims: <1> A Doherty amplifier circuit including a carrier amplifier and a peak amplifier, a first transformer having a primary winding connected to an output terminal of the carrier amplifier, a second transformer having a primary winding connected to an output terminal of the peak amplifier, a signal line connecting one end of a secondary winding of the first transformer and one end of a secondary winding of the second transformer, a first capacitor, a second capacitor connected in parallel to the primary winding of the first transformer, and a third capacitor connected in parallel to the primary winding of the second transformer, wherein one end of the first capacitor is connected to the signal line and the other end of the first capacitor is connected to a reference potential, and a sum of capacitance values ​​of the first capacitor and the signal line is defined as C Ｔ and the angular frequency is ω ０ and the load impedance is Z M A power amplifier circuit that satisfies the formula (1) when the load impedance Z M Target impedance Z tar The ratio Z tar / Z M <3> The power amplifier circuit according to <1>, further including: a first inductor connected in series between one end of the first capacitor and the secondary winding of the first transformer; and a second inductor connected in series between one end of the first capacitor and the secondary winding of the second transformer. <4> The power amplifier circuit according to <1> or <2>, further including: a first inductor connected in series between one end of the first capacitor and the secondary winding of the second transformer. Ｔ ', the capacitance value of the second capacitor is C1, and the inductance value of the second inductor is L Ｔ <5> The power amplifier circuit according to <1> or <3>, further including: a second capacitor connected in series between one end of the first capacitor and a secondary side of the first transformer; and a third capacitor connected in series between one end of the first capacitor and a secondary side of the second transformer. <6> The power amplifier circuit according to <3>, further including: a second capacitor connected in series between one end of the first capacitor and a secondary side of the second transformer; and a third capacitor connected in series between one end of the first capacitor and a secondary side of the second transformer. <6> The power amplifier circuit according to <1> or ...０ ２ L Ｔ C ２ ) and satisfying equation (5). <7> The power amplifier circuit according to any one of <1> to <6>, wherein the other end of the secondary side of the first transformer is connected to an output terminal via a matching circuit, and the other end of the secondary side of the second transformer is connected to a reference potential. <8> The power amplifier circuit according to <5>, wherein the other end of the secondary side of the first transformer is connected to an output terminal via a matching circuit, and the other end of the secondary side of the second transformer is connected to a reference potential. <9> The power amplifier circuit according to <5>, wherein the other end of the secondary side of the first transformer is connected to an output terminal via a matching circuit, and the other end of the secondary side of the second transformer is connected to a reference potential. <10> The power amplifier circuit according to <1> Ｔ and the frequency to be used is ω ０ and the load impedance is Z M When the load impedance Z is M Target impedance Z tar The ratio Z tar / Z M <9> A power amplifier circuit including a carrier amplifier and a peak amplifier constituting a Doherty amplifier circuit, a first transformer having a primary side connected to an output terminal of the carrier amplifier, a second transformer having a primary side connected to an output terminal of the peak amplifier, a signal line connecting one end of the secondary side of the first transformer and one end of the secondary side of the second transformer, and a first capacitor, one end of the first capacitor being connected to the signal line, and the other end of the first capacitor being connected to a reference potential, and a sum of capacitance values ​​of the first capacitor and the signal line being defined as C Ｔ and the frequency to be used is ω ０ and the load impedance is Z M When the load impedance Z is M Target impedance Z tarThe ratio Z tar / Z M satisfies Equation (2), and further includes a first inductor connected between one end of the first capacitor and the secondary side of the first transformer, and a second inductor connected between one end of the first capacitor and the secondary side of the second transformer, and an inductance value formed by the first inductor, the second inductor, and the signal line is set to L Ｔ And L Ｔ '=L Ｔ -(1 / ω ０ ２ C ２ <10> A power amplifier circuit including: a carrier amplifier and a peak amplifier constituting a Doherty amplifier circuit; a first transformer having a primary side connected to an output terminal of the carrier amplifier; a second transformer having a primary side connected to an output terminal of the peak amplifier; a signal line connecting one end of the secondary side of the first transformer and one end of the secondary side of the second transformer; and a first capacitor, one end of the first capacitor being connected to the signal line, and the other end of the first capacitor being connected to a reference potential, and a sum of capacitance values ​​of the first capacitor and the signal line being C Ｔ and the frequency to be used is ω ０ and the load impedance is Z M and the second transformer further includes a second capacitor connected in series between one end of the first capacitor and the secondary side of the first transformer, and a third capacitor connected in series between one end of the first capacitor and the secondary side of the second transformer, and the capacitance value of the third capacitor is C2, and the capacitance value C2'=C2 / (1-ω ０ ２ L Ｔ C ２<11> A power amplifier circuit that satisfies equation (5) when ∑ ∑ m ... Ｔ and the frequency to be used is ω ０ and the load impedance is Z M a power amplifier circuit that satisfies equation (1) when

[0048] 10 Input terminal 20 Output terminal 100, 100a, 100b, 100c Power amplifier circuit 110 Distributor 120 Carrier amplifier 121, 122, 131, 132 Amplifying element 130 Peak amplifier 140, 140a Converter 141, 151 Transformer 141a, 151a Input side winding 141b, 151b Output side winding 142, 143, 152, 153, 162 Capacitor 150, 150a Converter 160, 160a, 160b, 160c Connection portion 161 Signal line 163, 164 Inductor 200 Matching circuit

Claims

1. A Doherty amplifier circuit including a carrier amplifier and a peak amplifier, a first transformer having a primary winding connected to an output terminal of the carrier amplifier, a second transformer having a primary winding connected to an output terminal of the peak amplifier, a signal line connecting one end of a secondary winding of the first transformer and one end of a secondary winding of the second transformer, a first capacitor, a second capacitor connected in parallel to the primary winding of the first transformer, and a third capacitor connected in parallel to the primary winding of the second transformer, wherein one end of the first capacitor is connected to the signal line and the other end of the first capacitor is connected to a reference potential, and a sum of capacitance values ​​of the first capacitor and the signal line is defined as C Ｔ and the angular frequency is ω ０ and the load impedance is Z M A power amplifier circuit that satisfies formula (1) when 2. Load impedance Z M Target impedance Z tar The ratio of Z tar / Z M The power amplifier circuit according to claim 1 , wherein:

3. The power amplifier circuit according to claim 1 or 2, further comprising: a first inductor connected in series between one end of the first capacitor and the secondary winding of the first transformer; and a second inductor connected in series between one end of the first capacitor and the secondary winding of the second transformer.

4. The inductance value of the first inductor is L Ｔ ', the capacitance value of the second capacitor is C1, and the inductance value of the second inductor is L Ｔ 4. The power amplifier circuit according to claim 3, wherein, when C1 is a capacitance value of the third capacitor, the following formula (4) is satisfied:

5. The power amplifier circuit according to claim 1 or 3, further comprising: a fourth capacitor connected in series between one end of the first capacitor and the secondary winding of the first transformer; and a fifth capacitor connected in series between one end of the first capacitor and the secondary winding of the second transformer.

6. The capacitance value of the fourth capacitor and the capacitance value of the fifth capacitor are C2, and the capacitance value C2'=C2 / (1-ω ０ ２ L Ｔ C ２ 6. The power amplifier circuit according to claim 5, which satisfies formula (5) when 7. A power amplifier circuit as claimed in any one of claims 1 to 6, wherein the other end of the secondary winding of the first transformer is connected to an output terminal via a matching circuit, and the other end of the secondary winding of the second transformer is connected to a reference potential.

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