Power amplifier circuit

Abstract

Provided is a high-efficiency power amplification circuit that uses a differential structure to amplify power. The power amplification circuit includes: an amplifier (107) that amplifies one signal (RF2) of a differential signal; an amplifier (108) that amplifies the other signal (RF3) of the differential signal; a transformer (101) having a primary winding (1011) and a secondary winding (1012) electromagnetically coupled to the primary winding (1011), one end of the primary winding (1011) being connected to the amplifier (107) and the other end being connected to the amplifier (108), one end of the secondary winding (1012) being connected to an unbalanced line (106) that transmits an unbalanced signal, and the other end being connected to a ground; and a capacitor (102) having one end connected to a midpoint of the primary winding (1011) and the other end connected to the ground.

Description

TECHNICAL FIELD

[0001] The present application relates to a power amplification circuit. BACKGROUND

[0002] In communication of a mobile body such as a portable telephone, a power amplification circuit that amplifies a Radio Frequency (RF) signal is used. In the power amplification circuit, high efficiency is required. In order to achieve high efficiency of the power amplification circuit, there is a power amplification circuit that amplifies a differential signal.

[0003] In Patent Literature 1, a power amplification circuit that synthesizes a differential signal amplified by an amplifier through a transformer is shown. In the power amplification circuit described in Patent Literature 1, a differential signal is input from two amplifiers to a primary winding of the transformer, and a signal that synthesizes the differential signal is output from a secondary winding.

[0004] PRIOR ART LITERATURE

[0005] PATENT LITERATURE

[0006] Patent Literature 1: U.S. Patent No. 10411662 Specification SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] In the power amplification circuit using the transformer, due to a parasitic capacitance generated between the primary winding and the secondary winding of the transformer, a deviation (unbalance) of a phase difference and an amplitude difference of the differential signal from ideal occurs. In the power amplification circuit described in Patent Literature 1, one end of the secondary winding of the transformer that synthesizes the differential signal is connected to a ground through a capacitor. By providing the capacitor, it is possible to reduce a difference in potential difference generated between the primary winding and one end and the other end of the secondary winding at one end and the other end, respectively. By reducing the difference in potential difference, the unbalance caused by the parasitic capacitance is reduced.

[0009] On the other hand, by providing the capacitor, a load impedance in a fundamental frequency when the load side is observed from each of the amplifiers that become a differential pair changes. Since the capacitor is provided at one of the secondary windings, the impedance when the load side is observed from each of the amplifiers becomes different values. In a case where the load impedances observed from each of the amplifiers are different, an unbalance remains in the differential signal input to the transformer. In a case where the unbalance exists in the differential signal, the power efficiency of an output signal that synthesizes the differential signal decreases.

[0010] The present application has been achieved in view of such a situation, and an object thereof is to provide a power amplification circuit that is highly efficient by power amplification using a differential structure.

[0011] Means for solving the problem

[0012] The power amplification circuit according to one aspect of the present application includes: a first amplifier that amplifies one signal of a differential signal; a second amplifier that amplifies the other signal of the differential signal; a transformer having a first winding and a second winding electromagnetically coupled to the first winding, one end of the first winding being connected to the first amplifier and the other end being connected to the second amplifier, one end of the second winding being connected to an unbalanced line that transmits an unbalanced signal and the other end being connected to a ground; and a capacitive element having one end connected to a midpoint of the first winding and the other end connected to the ground.

[0013] Effects of the invention

[0014] According to the present application, a power amplification circuit that efficiently amplifies power using a differential structure can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a circuit diagram of the power amplification circuit according to the first embodiment.

[0016] Figure 2 is a graph showing the load impedance of each amplifier in the power amplification circuit according to the first embodiment.

[0017] Figure 3 is a graph showing the loss of each amplifier in the power amplification circuit according to the first embodiment.

[0018] Figure 4 is a graph showing the phase difference of the signals from each amplifier in the power amplification circuit according to the first embodiment.

[0019] Figure 5 is a circuit diagram of the power amplification circuit according to the second embodiment.

[0020] Figure 6 is a graph showing the loss of each amplifier in the power amplification circuit according to the second embodiment.

[0021] Figure 7 is a circuit diagram of the power amplification circuit according to the third embodiment.

[0022] Figure 8 is a layout diagram of the transformer in the power amplification circuit according to the third embodiment.

[0023] Figure 9 is another layout diagram of the transformer in the power amplification circuit according to the third embodiment.

[0024] Figure 10 is another layout diagram of the transformer in the power amplification circuit according to the third embodiment.

[0025] Figure 11 is another layout diagram of the transformer in the power amplification circuit of the third embodiment.

[0026] Figure 12 is another layout diagram of the transformer in the power amplification circuit of the third embodiment.

[0027] Figure 13 is a circuit diagram of the power amplification circuit of the fourth embodiment.

[0028] Figure 14 is a circuit diagram of the power amplification circuit of the fifth embodiment.

[0029] Figure 15 is a circuit diagram of the power amplification circuit of the sixth embodiment.

[0030] Figure 16 is a circuit diagram of the power amplification circuit of the seventh embodiment.

[0031] Figure 17 is a circuit diagram of the power amplification circuit of the eighth embodiment.

[0032] Figure 18 is a circuit diagram of the power amplification circuit of the reference example.

[0033] Figure 19 is a graph showing the load impedance of each amplifier in the power amplification circuit of the reference example.

[0034] Figure 20 is a graph showing the loss of each amplifier in the power amplification circuit of the reference example.

[0035] Figure 21 is a graph showing the phase difference of the signal from each amplifier in the power amplification circuit of the reference example.

[0036] Explanation of Reference Numerals:

[0037] 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G... power amplification circuit, 101, 109... transformer, 1011, 1091... primary winding, 1012, 1092... secondary winding, 102... capacitor, 103... inductor, 107, 108, 110... amplifier. DETAILED DESCRIPTION

[0038] Hereinafter, the embodiments of the present application will be explained in detail with reference to the drawings. Note that the same reference numerals are assigned to the same elements throughout the drawings and repeated explanation will be omitted.

[0039] The first embodiment will be explained. Figure 1A circuit diagram of the power amplification circuit 10 of the first embodiment is shown. The power amplification circuit 10 has a transformer 101, capacitors 102, 105, 111, 116, 118, 120, inductors 103, 104, 117, 119, amplifiers 107, 108, 110, a matching circuit 113, and termination circuits 114, 115.

[0040] The transformer 101 has a primary winding 1011 (first winding) and a secondary winding 1012 (second winding). The primary winding 1011 and the secondary winding 1012 are electromagnetically coupled. One end of the primary winding 1011 is connected to the output of the amplifier 107, and the other end is connected to the output of the amplifier 108. One end of the secondary winding 1012 is connected to the output terminal 122 through an unbalanced line 106 and the capacitor 105, and the other end is connected to the ground through the inductor 104.

[0041] One differential signal is input to one end of the primary winding 1011 from the amplifier 107, and another differential signal is input to the other end of the primary winding 1011 from the amplifier 108. The transformer 101 performs balanced-unbalanced conversion with respect to the differential signals input to the primary winding 1011. The signal converted to the unbalanced signal by the transformer 101 is output to the output terminal 122 through the unbalanced line 106 and the capacitor 105.

[0042] The other end of the capacitor 102 is connected to the ground through the inductor 104. The other end of the capacitor 102 is connected to the other end of the secondary winding 1012.

[0043] One end of the inductor 103 is connected to the midpoint of the primary winding 1011, and the other end is connected to one end of the capacitor 102. Note that the midpoint in the present application includes an offset of ±15% or so from the center of the primary winding 1011.

[0044] The inductor 104 is an inductance generated by a via hole provided in a substrate (not shown) on which the transformer 101 is provided, for connection to the ground.

[0045] The capacitor 105 is provided between the secondary winding 1012 and the output terminal 122. The capacitor 105 is provided so as to make the impedance with respect to the direct current component appear as an open circuit when the secondary winding 1012 is viewed from the output terminal 122.

[0046] The unbalanced line 106 is a wiring connected to one end of the secondary winding 1012. The signal synthesized by the transformer 101 is transmitted in the unbalanced line 106.

[0047] An input of the amplifier 107 (first amplifier) is connected to one end of the secondary winding 1092 of the transformer 109, and an output is connected to one end of the primary winding 1011 of the transformer 101. The amplifier 107 amplifies the signal RF2 from the transformer 109 and outputs a signal RF4.

[0048] An input of the amplifier 108 (second amplifier) is connected to the other end of the secondary winding 1092 of the transformer 109, and an output is connected to the other end of the primary winding 1011 of the transformer 101. The amplifier 108 amplifies the signal RF3 from the transformer 109 and outputs a signal RF5.

[0049] The transformer 109 has a primary winding 1091 and a secondary winding 1092. The primary winding 1091 and the secondary winding 1092 are electromagnetically coupled. One end of the primary winding 1091 is connected to an output of the amplifier 110 through a capacitor 111, and the other end is connected to a ground.

[0050] A signal RF1 amplified by the amplifier 110 is input to the primary winding 1091. The transformer 109 performs unbalanced balanced conversion with respect to an unbalanced signal input from the amplifier 110 through an unbalanced line (not shown). From one end of the secondary winding 1092, a signal RF2 is output, and from the other end, a signal RF3 is output, according to the signal input to the primary winding 1091. The signal RF2 and the signal RF3 are signals that are substantially opposite to each other.

[0051] The amplifier 110 (third amplifier) amplifies an input signal RFin input through an input terminal 121 and a matching circuit 113. The amplifier 110 outputs the signal RF1 to the transformer 109 through the capacitor 111. The capacitor 111 is provided to block a direct current component of the signal RF1. An output of the amplifier 110 is connected to a ground through a capacitor 112. The capacitor 112 is provided to adjust an impedance when the transformer 109 side is viewed from the amplifier 110.

[0052] The amplifiers 107, 108, and 110 are configured to include, for example, transistors such as heterojunction bipolar transistors (HBTs). Alternatively, the amplifiers 107, 108, and 110 can be configured to include field effect transistors.

[0053] The matching circuit 113 is a circuit provided to adjust an impedance between the input terminal 121 and an input of the amplifier 110.

[0054] A termination circuit 114 is provided between the output of the amplifier 107 and one end of the primary winding 1011. The termination circuit 114 has a capacitor 1141 and an inductor 1142, and is provided to terminate a high harmonic component in the output signal from the amplifier 107. A termination circuit 115 is provided between the output of the amplifier 108 and the other end of the primary winding 1011. The termination circuit 115 has a capacitor 1151 and an inductor 1152, and is provided to terminate a high harmonic component in the output signal from the amplifier 108. For example, the values of the capacitor 1141 and the inductor 1142 are determined to be an integral multiple of the frequency of the signal that is intended to be amplified by the amplifier 107. Similarly, the values of the capacitor 1151 and the inductor 1152 are determined to be an integral multiple of the frequency of the signal that is intended to be amplified by the amplifier 108.

[0055] A capacitor 116 is provided to connect one end and the other end of the primary winding 1011, and the capacitor 116 is connected to the outputs of the amplifier 107 and the amplifier 108, respectively. The capacitor 116 is provided to adjust the impedance on the side of the transformer 101 when viewing the outputs of the amplifier 107 and the amplifier 108.

[0056] The amplifiers 107, 108, the transformer 109, the amplifier 110, the capacitors 111, 112, the matching circuit 113, and the termination circuits 114, 115 are provided on a semiconductor substrate S. The ground in the semiconductor substrate S is connected to the ground of the substrate on which the power amplification circuit 10 is provided.

[0057] One end of an inductor 117 is supplied with the power supply voltage Vcc, and the other end is connected to the midpoint of the primary winding 1011. The power supply voltage Vcc is supplied to the amplifier 107 and the amplifier 108 through the inductor 117 and the primary winding 1011. A capacitor 118 is provided between the inductor 117 and the ground, and has a function of flowing an alternating component to the ground.

[0058] One end of an inductor 119 is supplied with the power supply voltage Vcc, and the other end is connected to the amplifier 110. The power supply voltage Vcc is supplied to the amplifier 110 through the inductor 119. A capacitor 120 is provided between the inductor 119 and the ground, and has a function of flowing an alternating component to the ground.

[0059] The power amplification circuit 10 converts the signal RF1, which is a signal obtained by amplifying the input signal RFin input from the input terminal 121 by the amplifier 110, into a differential signal through the transformer 109. The converted differential signal is amplified by the amplifier 107 and the amplifier 108, respectively. The differential signals from the amplifier 107 and the amplifier 108 are combined by the transformer 101, and are output as an output signal RFout from the output terminal 122. The power amplification circuit 10 is a power amplification circuit that performs differential amplification.

[0060] Referring to Figure 18 the power amplification circuit 1800, the features of the power amplification circuit 10 are explained. Figure 18 A circuit diagram of the power amplification circuit 1800 as a reference example is shown. In the power amplification circuit 1800, the primary winding 1011 is not connected to the ground through the inductor 103 and the capacitor 102, and the secondary winding 1012 is connected to the ground through the capacitor 1801 and the inductor 104, which is different from the power amplification circuit 10.

[0061] In Figure 2 a Smith chart of the power amplification circuit 10, a curve G1 representing the impedance when the transformer 101 side is viewed from the amplifier 107 and a curve G2 representing the impedance when the transformer 101 side is viewed from the amplifier 108 are shown, respectively. The locus of the impedance when the frequency of the input signal RFin is changed from 1.7 GHz to 2.7 GHz is a locus around the clock in the curve G1 from a position g11 to a position g12. In addition, the locus of the impedance in the curve G2 in the same frequency range becomes a locus around the clock from a position g21 to a position g22. Note that, in the simulation of the power amplification circuit 10, the inductance of the inductor 103 is 0.3 nH and the capacitance of the capacitor 102 is 12 pF. Figures 2 to 4

[0062] In Figure 2 the power amplification circuit 10, the difference between the locus of the curve G1 from the position g11 to the position g12 and the locus of the curve G2 from the position g21 to the position g22 is the difference in the impedance when the transformer 101 side is viewed from the amplifier 107 and the amplifier 108, respectively.

[0063] Figure 19 A similar Smith chart in the power amplification circuit 1800 is shown. In Figure 19 a Smith chart of the power amplification circuit 1800, the impedance when the transformer 101 side is viewed from the amplifier 107 is shown by a curve G3, and the impedance when the transformer 101 side is viewed from the amplifier 108 is shown by a curve G4. As in the case of Figure 2 , the locus of the impedance when the frequency of the input signal RFin is changed is a locus around the clock in the curve G3 from a position g31 to a position g32, and a locus around the clock in the curve G4 from a position g41 to a position g42.

[0064] In Figure 19 the power amplification circuit 1800, the difference between the locus of the curve G3 from the position g31 to the position g32 and the locus of the curve G4 from the position g41 to the position g42 is the difference in the impedance when the transformer 101 side is viewed from the amplifier 107 and the amplifier 108, respectively.

[0065] ​Comparison within the frequency range of the input signal RFI from 1.7 GHz to 2.7 GHz Figure 2 The difference in impedance and Figure 19 When there is a difference in impedance, Figure 2 The differences are relatively small. That is, compared with the power amplifier circuit 1800, the power amplifier circuit 10 can reduce the impedance difference between the amplifier 107 and the amplifier 108.

[0066] exist Figure 3 In the diagram, curve L1, representing the loss between the output of amplifier 107 and output terminal 122 in power amplifier circuit 10, and curve L2, representing the loss between the output of amplifier 108 and output terminal 122, are shown respectively. Figure 4 The horizontal axis represents the frequency of the input signal RFin.

[0067] Figure 20 and Figure 3 Similarly, curve L3, representing the loss between the output of amplifier 107 and output terminal 122 in power amplifier circuit 1800, and curve L4, representing the loss between the output of amplifier 108 and output terminal 122, are shown respectively.

[0068] The loss between the output of amplifier 107 and output terminal 122 varies based on the voltage and current at the end of the primary winding 1011 connected to amplifier 107. Similarly, the loss between the output of amplifier 108 and output terminal 122 varies based on the voltage and current at the other end of the primary winding 1011 connected to amplifier 108. That is, the difference in loss shown as the difference between curves L1 and L2 corresponds to the difference in voltage and current at the endpoints of the primary winding 1011. The smaller the difference in loss, the smaller the imbalance in the amplitude of the differential signal, i.e., the difference in voltage and current at the endpoints of the primary winding 1011. The same applies to the difference between curves L3 and L4.

[0069] Within the frequency range of 1.7 GHz to 2.7 GHz, Figure 3 The difference ratio between curve L1 and curve L2 in the figure Figure 20 The difference between curves L3 and L4 is small. Therefore, compared with power amplifier circuit 1800, power amplifier circuit 10 can reduce the imbalance of differential signal amplitude.

[0070] Figure 4 The diagram shows the phase difference between the signal RF4 from amplifier 107 and the signal RF5 from amplifier 108 in the power amplifier circuit 10 when the input signal RFI is changed. Figure 21 The same phase difference is shown in power amplifier circuit 1800.

[0071] In the range of frequencies of 1.7 GHz to 2.7 GHz, the phase difference varies from 183° to 176°, and in the range of frequencies of 2.7 GHz to 3.7 GHz, the phase difference varies from 186° to 177°. That is, the power amplification circuit 10 can make the phase difference closer to 180°, which is the ideal value, compared with the power amplification circuit 1800. Figure 4 In the range of frequencies of 1.7 GHz to 2.7 GHz, the phase difference varies from 183° to 176°, and in the range of frequencies of 2.7 GHz to 3.7 GHz, the phase difference varies from 186° to 177°. That is, the power amplification circuit 10 can make the phase difference closer to 180°, which is the ideal value, compared with the power amplification circuit 1800. Figure 21 In the range of frequencies of 1.7 GHz to 2.7 GHz, the phase difference varies from 183° to 176°, and in the range of frequencies of 2.7 GHz to 3.7 GHz, the phase difference varies from 186° to 177°. That is, the power amplification circuit 10 can make the phase difference closer to 180°, which is the ideal value, compared with the power amplification circuit 1800.

[0072] In the power amplification circuit 10, as shown in Figure 2 , it is possible to reduce the imbalance of the amplitudes shown by Figure 3 and the imbalance of the phase differences shown by Figure 4 while reducing the difference in impedance.

[0073] In a transformer that ideally combines differential signals, a signal component including an odd-numbered component of a fundamental frequency is not generated at the midpoint of the primary winding. The reason for this is because the signals from the respective differential amplifiers cancel each other out at the midpoint. That is, in the case where the midpoint of the primary winding is observed from one of the differential amplifiers, the signal from the differential amplifier appears to flow to ground. That is, in the odd-numbered signal component, the impedance when the transformer 101 side is observed from the respective differential amplifiers appears to be virtually short-circuited through the primary winding 1011. The short circuit in the present application refers to a state in which, on a Smith chart, the real part is in the range of 0 to 5 ohms.

[0074] On the other hand, in an actual transformer, due to the parasitic capacitance between the primary winding and the secondary winding, the impedance when the midpoint of the primary winding is observed from the respective differential amplifiers deviates from the short-circuited state. In the power amplification circuit 10, the midpoint of the primary winding 1011 is ac-grounded through the capacitor 102. It is possible to adjust the capacitance value of the capacitor 102 so that the impedance when the midpoint of the primary winding 1011 is observed from the primary winding 1011 through the output of the amplifier 107 and the output of the amplifier 108 appears to be short-circuited with respect to the fundamental frequency of the input signal RFin.

[0075] As a result of this, the transformer 101 can reduce the imbalance of the differential signals, and the power amplification circuit 10 can perform more appropriate differential amplification. Furthermore, in the power amplification circuit 10, as shown in Figure 2 and the comparison with Figure 19 , the impedance when the transformer 101 side is observed from the amplifier 107 and the amplifier 108 does not greatly differ, and it is possible to reduce the imbalance.

[0076] In addition, in the power amplification circuit 10, by providing the inductor 103, compared with the power amplification circuit in which only the capacitor 102 connects the primary winding 1011 to ground as described in the second embodiment, it is possible to reduce the imbalance in a wider range of frequencies.

[0077] The second embodiment will be described. Following the second embodiment, descriptions of matters common to the first embodiment will be omitted; only the differences will be explained. In particular, the same effects produced by the same structure will not be mentioned repeatedly in each embodiment.

[0078] Figure 5 A circuit diagram of the power amplifier circuit 10A according to the second embodiment is shown. The power amplifier circuit 10A differs from the power amplifier circuit 10 in that it does not have an inductor 103 between the primary winding 1011 and ground, but instead has a capacitor 501.

[0079] Figure 6 and Figure 3 Similarly, the losses in the power amplifier circuit 10A are shown. Figure 6 In the diagram, curve L5 shows the losses for amplifier 107, and curve L6 shows the losses for amplifier 108. Even when only capacitor 501 is provided and the primary winding 1011 is connected to ground, the difference in losses can be reduced, for example, at frequencies around 2.0 GHz.

[0080] The third embodiment will be described. Figure 7 A circuit diagram of the power amplifier circuit 10B according to the third embodiment is shown. The power amplifier circuit 10B is a structure obtained by replacing the inductor 103 in the power amplifier circuit 10 with a line 701 that functions as an inductor element. The power amplifier circuit 10B can also reduce the imbalance of the differential signal in the same way as the power amplifier circuit 10. In the power amplifier circuit 10B, the line 701 and the transformer 101 are provided on the substrate U.

[0081] Regarding the stacked structure of the substrate U in the case where the inductor 103 is composed of line 701, refer to Figures 8 to 12 This will be explained. The substrate U, viewed from above, has... Figure 8 The stack of wiring layer 81 and wiring layer 82 shown.

[0082] A primary winding 1011 (first conductor portion), a line 701, and electrodes 8011 and 8012, all composed of conductors, are provided on the wiring layer 81 (first wiring layer). The primary winding 1011, partially circular in shape, is connected to the line 701 on the wiring layer 81. Electrode 8011 (first electrode) is connected to the line 701. Electrode 8012 (second electrode) is positioned facing electrode 8011. Electrode 8012 is connected to the wiring layer 82 through a through-hole 803 (first through-hole). For example, a capacitor 102 is mounted on electrodes 8011 and 8012 as a surface-mount component.

[0083] Wiring layer 82 (second wiring layer) is disposed opposite to wiring layer 81. A conductor portion 804 (second conductor portion) is disposed in wiring layer 82. Conductor portion 804 is a part of the secondary winding 1012, which includes the other end of the secondary winding 1012. Conductor portion 804 is disposed such that it partially overlaps with the primary winding 1011 when viewed from above the substrate U. Specifically, the portion of conductor portion 804 depicted as a partial circle overlaps with the primary winding 1011.

[0084] Conductor portion 804 is connected to capacitor 102 through through hole 803. Conductor portion 804 is connected to ground of substrate U through through hole 805 (second through hole). Conductor portion 804 is connected to another part of secondary winding 1012, which is disposed in a different wiring layer (not shown), through through hole 806.

[0085] Reference Figures 9 to 12 ,right Figure 8 Another example of a substrate U including wiring layer 81 and wiring layer 82 will be described. Figure 9 The diagram shows a substrate U in which wiring layer 81A (first wiring layer), wiring layer 91, wiring layer 82, and wiring layer 92 are sequentially disposed in the stacking direction. It should be noted that... Figures 9 to 12 In this case, there are 4 wiring layers, but the number of wiring layers on the substrate U is not limited to this, and other wiring layers can also be provided.

[0086] exist Figure 9 In the wiring layer 81A, a conductor portion 901 (first conductor portion) is provided as part of the primary winding 1011. The conductor portion 901 is provided on the wiring layer 81A in a manner that depicts a partial circle. The conductor portion 901 and Figure 8 The primary winding 1011 is also connected to the line 701. The conductor portion 901 is connected to the conductor portion 902 provided on the wiring layer 92 through through holes 9011 and 9012 provided at the end.

[0087] The wiring layer 91 has a conductor portion 903 connected to the conductor portion 804 of the wiring layer 82 via a through-hole 806. The conductor portion 903 is another part of the secondary winding 1012. The conductor portion 903 is provided on the wiring layer 91 in a partially circular manner. The conductor portion 903 is configured to partially overlap with the conductor portion 901 when viewed from above the substrate U. The conductor portion 903 is connected to the unbalanced line 106.

[0088] The wiring layer 92 has a conductor portion 902 that is connected to the conductor portion 901 through through holes 9011 and 9012 and serves as another part of the primary winding 1011. The conductor portion 902 is provided on the wiring layer 92 in a partially circular manner. The primary winding 1011 is constituted by the conductor portion 901 and the conductor portion 902. Furthermore, in Figure 9In the illustrated substrate U, the via hole 805 of the wiring layer 82 is connected to the ground through the wiring layer 92.

[0089] Figure 10 Another example of the structure of the substrate U is illustrated. As in the case of the substrate U of Figure 8 The primary winding 1011 is also provided in the wiring layer 81, and the wiring layer 91 is provided between the wiring layer 81 and the wiring layer 82.

[0090] Figure 11 Another example of the structure of the substrate U is illustrated. As in the case of the substrate U of Figure 11 In the substrate U, the wiring layer 81A, the wiring layer 92, the wiring layer 91, and the wiring layer 82 are provided in this order in the stacking direction. The connection of the wiring layer 81A to the wiring layer 92 and the connection of the wiring layer 82 to the wiring layer 91 are the same as in the case of the substrate U of Figure 9 .

[0091] Figure 12 Another example of the structure of the substrate U is illustrated. As in the case of the substrate U of Figure 12 In the substrate U, the wiring layer 81A, the wiring layer 82, the wiring layer 91, and the wiring layer 92 are provided in this order in the stacking direction. The connection of the wiring layer 81A to the wiring layer 92 and the connection of the wiring layer 82 to the wiring layer 91 are the same as in the case of the substrate U of Figure 9 . In the example illustrated in Figure 12 , the via hole 805 of the wiring layer 82 is connected to the ground through the wiring layer 92.

[0092] The fourth embodiment will be described. Figure 13 A circuit diagram of the power amplification circuit 10C of the fourth embodiment is illustrated. In the power amplification circuit 10C, the other end of the capacitor 102 is connected to the ground through the semiconductor substrate S, unlike the power amplification circuit 10. In the power amplification circuit 10C, the other end of the capacitor 102 is connected to the inductor 104 and the ground, for example, by being connected to the ground side of the amplifier 108. In the power amplification circuit 10C, it is also possible to reduce the imbalance of the differential signal by adjusting the values of the inductor 103 and the capacitor 102, as in the power amplification circuit 10.

[0093] The fifth embodiment will be described. Figure 14 A circuit diagram of the power amplification circuit 10D of the fifth embodiment is illustrated. The power amplification circuit 10D is provided with a capacitor 1401 and an inductor 1402. In the power amplification circuit 10D, the midpoint of the primary winding 1011 is connected to the ground through the capacitor 1401. Further, the power supply voltage Vcc is supplied to the midpoint of the primary winding 1011 through the inductor 1402.

[0094] In the power amplification circuit 10D, the secondary winding 1012 is also supplied with the power supply voltage Vcc. However, the direct current component is blocked by the capacitor 105, and thus the influence on the output signal RFout can be suppressed.

[0095] The power amplification circuit 10D can not use the capacitor 118 for the AC ground of the power supply voltage, compared with the power amplification circuit 10, and thus the number of circuit elements can be reduced. Also, by the power amplification circuit 10D, the imbalance of the differential signal can be reduced as with the power amplification circuit 10.

[0096] The sixth embodiment will be described. Figure 15 A circuit diagram of the power amplification circuit 10E of the sixth embodiment is shown.

[0097] The power amplification circuit 10E has an inductor 1501 and a capacitor 1502. One end of the inductor 1501 is connected to the midpoint of the secondary winding 1092 (first winding) of the transformer 109. The other end of the inductor 1501 is connected to one end of the capacitor 1502. The other end of the capacitor 1502 is connected to the other end of the primary winding 1091 (second winding) and the ground.

[0098] In the power amplification circuit 10E, by the same effect as the power amplification circuit 10, the imbalance between the signal RF2 and the signal RF3 generated in the imbalance balance conversion of the transformer 109 can be reduced. The power amplification circuit 10E can balance the amplitudes and the phases of the differential signals input to the amplifiers 107 and 108, respectively. By reducing the imbalance of the differential signal before amplification, the imbalance of the differential signal synthesized by the transformer 101 can be reduced.

[0099] The seventh embodiment will be described. Figure 16 A circuit diagram of the power amplification circuit 10F of the seventh embodiment is shown. The power amplification circuit 10F has an inductor 1601 and a capacitor 1602. Note that the power amplification circuit 10F in the seventh embodiment and the power amplification circuit 10G in the eighth embodiment described later do not have the capacitor 111, unlike the power amplification circuit 10.

[0100] One end of the inductor 1601 is connected to the other end of the primary winding 1091 and the other end of the capacitor 1502, and the other end is supplied with the power supply voltage Vcc. One end of the capacitor 1602 is connected to the other end of the primary winding 1091, and the other end is connected to the ground. The power supply voltage is supplied to the amplifier 110 through the primary winding 1091 and the inductor 1601.

[0101] The power amplification circuit 10F can reduce the number of circuit elements, because it does not use the capacitor 120 for the AC ground of the power supply voltage, compared with the power amplification circuit 10E. In addition, the power amplification circuit 10F can use the primary winding 1091 for the inductive element provided between the amplifier 110 and the power supply, and thus can realize the miniaturization of the circuit. The power amplification circuit 10F can also reduce the imbalance of the differential signal, like the power amplification circuit 10E.

[0102] The eighth embodiment will be described. Figure 17 A circuit diagram of the power amplification circuit 10G of the eighth embodiment is shown. In the power amplification circuit 10G, the other end of the capacitor 1502 is connected to the terminal to which the amplifier 110 and the ground are connected, unlike the power amplification circuit 10E. In other words, in the power amplification circuit 10G, the other end of the capacitor 1502 is connected to the ground of the semiconductor substrate S through the ground side of the amplifier 110. The power amplification circuit 10G is connected to the terminal to which the amplifier 110 and the ground are connected. In the power amplification circuit 10G, the imbalance of the differential signal can also be reduced by adjusting the values of the inductor 1501 and the capacitor 1502, like the power amplification circuit 10E.

[0103] Note that, in the power amplification circuits 10E, 10F, and 10G, the transformer 101 that combines the amplified differential signal can also be connected as in the power amplification circuit 1800, for example. That is, the transformer that combines the power can also be connected other than the example shown in the power amplification circuit 10.

[0104] The above describes the respective embodiments of the present application. The power amplification circuits 10 and 10A include: an amplifier 107 that amplifies one signal RF2 of a differential signal; an amplifier 108 that amplifies the other signal RF3 of the differential signal; a transformer 101 that has a primary winding 1011 and a secondary winding 1012, one end of the primary winding 1011 is connected to the amplifier 107, and the other end is connected to the amplifier 108; one end of the secondary winding 1012 is connected to an unbalanced line 106 that transmits an unbalanced signal, the other end is connected to the ground, and the secondary winding 1012 is electromagnetically coupled to the primary winding 1011; and a capacitor 102 that has one end connected to the midpoint of the primary winding 1011 and the other end connected to the ground.

[0105] In the power amplification circuit 10, 10A, the midpoint of the primary winding 1011 is AC-grounded through the capacitor 102. Thereby, the capacitance value of the capacitor 102 can be adjusted so that, with respect to the fundamental frequency of the input signal RFin, the impedance observed from the output of the amplifier 107 and the output of the amplifier 108 when the midpoint of the primary winding 1011 is observed appears to be short-circuited. In the power amplification circuit 10, the unbalance of the differential signal generated by the transformer 101 can be reduced. By reducing the unbalance, the efficiency of the power amplification of the power amplification circuit 10 can be improved.

[0106] In addition, the power amplification circuit 10E includes the amplifier 107 that amplifies one signal of the differential signal, the amplifier 108 that amplifies the other signal of the differential signal, the transformer 109 that has a secondary winding 1092 and a primary winding 1091, one end of the secondary winding 1092 is connected to the amplifier 107, the other end is connected to the amplifier 108, one end of the primary winding 1091 is connected to an unbalanced line through which the unbalanced signal is transmitted, the other end is connected to the ground, and the primary winding 1091 is electromagnetically coupled to the secondary winding 1092, and the capacitor 1502 that has one end connected to the midpoint of the secondary winding 1092 and the other end connected to the ground.

[0107] In the power amplification circuit 10E, by the same effect as the power amplification circuit 10, the unbalance of the signal RF2 and the signal RF3 generated in the transformer 109 can be reduced. The power amplification circuit 10E can balance the amplitude and the phase of the differential signal input to the amplifier 107 and the amplifier 108, respectively. By reducing the unbalance of the differential signal before amplification, the unbalance of the differential signal synthesized by the transformer 101 can be reduced. By reducing the unbalance, the efficiency of the power amplification of the power amplification circuit 10E can be improved.

[0108] In addition, in the power amplification circuit 10, the other end of the capacitor 102 is connected to the other end of the secondary winding 1012. By connecting the capacitor 102 to the ground in this way, the unbalance of the differential signal generated by the transformer 101 can be appropriately reduced.

[0109] In addition, in the power amplification circuit 10C, the other end of the capacitor 102 is connected to the ground through the semiconductor substrate S on which the amplifier 107 and the amplifier 108 are provided. Thereby, by connecting the capacitor 102 to the ground in this way, the unbalance of the differential signal generated by the transformer 101 can be appropriately reduced.

[0110] Further, the power amplification circuit 10 is provided with an inductor 103 having one end connected to the midpoint of the primary winding 1011 and the other end connected to one end of the capacitor 102, and the capacitor 102 is connected to the midpoint of the primary winding 1011 through the inductor 103. By providing the inductor 103, adjustment of the impedance in the case where the midpoint of the primary winding 1011 is observed from the amplifiers 107 and 108 is more appropriately performed. Thereby, compared with the case where only the capacitor is used, it is possible to reduce the imbalance in a wider frequency range of the input signal RFin.

[0111] Further, in the power amplification circuit 10B, the inductor 103 is constituted by a wiring of the substrate U in which the inductor 103 is provided. Thereby, it is possible to reduce the number of circuit elements.

[0112] Further, in the power amplification circuit 10B, the substrate U is a laminate in which wiring layers including the wiring layers 81, 81A in which the primary winding 1011 or the conductor portion 901, the capacitor 102, and the inductor 103 are provided and the wiring layer 82 which is provided so as to connect the conductor portion 804 which is a part of the secondary winding 1012 and includes the other end of the secondary winding 1012 to the other end of the capacitor 102 and the ground, and partially overlaps with the primary winding 1011 or the conductor portion 901 in a plan view of the substrate U. Thereby, it is possible to realize the power amplification circuit 10B.

[0113] Further, in the power amplification circuit 10D, one end of the capacitor 1401 is connected to a power supply which supplies the power supply voltage Vcc to the amplifiers 107 and 108. Thereby, it is possible to reduce the number of circuit elements.

[0114] Further, in the power amplification circuit 10F, there is provided an amplifier 110 having one end connected to the primary winding 1091, and one end of the capacitor 1502 is connected to a power supply which supplies the power supply voltage Vcc to the amplifier 110. Thereby, it is possible to reduce the number of circuit elements.

[0115] Further, in the power amplification circuit 10G, the other end of the capacitor 1502 is connected to a terminal to which the amplifier 110 and the ground are connected. Thereby, it is also possible to reduce the imbalance of the differential signal synthesized by the transformer 101 by reducing the imbalance of the differential signal before amplification.

[0116] Further, the power amplification circuits 10E, 10F, and 10G are provided with an inductor 1501 having one end connected to the midpoint of the secondary winding 1092 and the other end connected to one end of the capacitor 1502, and the capacitor 1502 is connected to the midpoint of the secondary winding 1092 through the inductor 1501. Thereby, it is also possible to reduce the imbalance in a wider frequency range as in the power amplification circuit 10.

[0117] Note that each of the above-described embodiments is used for easy understanding of the present application, and is not used to limit the interpretation of the present application. The present application can be altered / modified within the scope thereof without departing from the spirit of the present application, and equivalents thereof are also included in the scope of the present application. That is, modes obtained by appropriately designing changes to each of the embodiments by those skilled in the art are also included in the scope of the present application, as long as the modes have the characteristics of the present application. For example, each element included in each of the embodiments, the arrangement thereof, materials, conditions, shapes, dimensions, and the like are not limited to the illustrated contents, and can be appropriately altered. In addition, each of the embodiments is illustrative, and partial replacement or combination of structures shown in different embodiments is of course possible, and these are also included in the scope of the present application, as long as the characteristics of the present application are included.

Claims

1. A power amplifier circuit, comprising: The first amplifier amplifies one signal of the differential signal; A second amplifier amplifies another signal of the differential signal; A transformer has a first winding and a second winding. One end of the first winding is connected to a first amplifier, and the other end of the first winding is connected to a second amplifier. One end of the second winding is connected to an unbalanced line for transmitting an unbalanced signal, and the other end of the second winding is connected to ground. The second winding is electromagnetically coupled to the first winding. The capacitor element has one end connected to the midpoint of the first winding, and the other end connected to ground through the second inductor element. The other end of the capacitor element is connected to the other end of the second winding.

2. The power amplifier circuit according to claim 1, wherein, The other end of the capacitor element is connected to the ground via a semiconductor substrate on which the first amplifier and the second amplifier are disposed.

3. The power amplifier circuit according to claim 1 or 2, wherein, One end of the first winding is connected to the output of the first amplifier. The other end of the first winding is connected to the output of the second amplifier.

4. The power amplifier circuit according to claim 3, wherein, The power amplifier circuit also includes an inductor, one end of which is connected to the midpoint of the first winding, and the other end of which is connected to one end of the capacitor. The capacitor element is connected to the midpoint of the first winding via the inductor element.

5. The power amplifier circuit according to claim 4, wherein, The inductor is formed by wiring on a substrate on which the inductor is disposed.

6. The power amplifier circuit according to claim 5, wherein, The substrate is a laminate containing wiring layers, the wiring layers comprising a first wiring layer and a second wiring layer opposite to the first wiring layer. The first wiring layer is provided with a first conductor portion that is all or part of the first winding, an inductor element connected to the first conductor portion, a first electrode connected to the inductor element, and a second electrode connected to a first through-hole of the substrate. The second wiring layer is configured such that a second conductor portion, which includes the other end of the second winding and is part of the second winding, is connected to the first through-hole and the second through-hole connected to the ground, and partially overlaps with the first conductor portion when viewed from above on the substrate.

7. The power amplifier circuit according to claim 3, wherein, One end of the capacitor element is connected to a power source that supplies the power supply voltage to the first amplifier and the second amplifier.

8. The power amplifier circuit according to claim 1 or 2, wherein, One end of the first winding is connected to the input of the first amplifier. The other end of the first winding is connected to the input of the second amplifier.

9. The power amplifier circuit according to claim 8, wherein, The power amplifier circuit also includes a third amplifier whose output is connected to one end of the second winding. One end of the second winding is connected to the power supply voltage that supplies the third amplifier.

10. The power amplifier circuit according to claim 9, wherein, The other end of the capacitor element is connected to the terminal of the third amplifier that is connected to ground.

11. The power amplifier circuit according to claim 8, wherein, The power amplifier circuit also includes an inductor, one end of which is connected to the midpoint of the first winding, and the other end of which is connected to one end of the capacitor. The capacitor element is connected to the midpoint of the first winding via the inductor element.

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