Power amplifier circuit, differential power amplifier circuit

Abstract

Provided is a power amplification circuit, a differential power amplification circuit, which improves input impedance for high-frequency signals. The power amplification circuit includes: a first transistor, a base or gate of which is supplied with a high-frequency signal through a capacitor and a bias current through a resistance element; a second transistor, an emitter or source of which is connected to the first transistor at a base or gate thereof, and an output terminal is connected to a collector or drain thereof; and a third transistor, a base or gate of which is connected to the first transistor at a collector or drain thereof, and a reference potential is connected to an emitter or source thereof, the third transistor being configured to increase a current flowing to the collector or drain thereof as a current flowing to the collector or drain of the second transistor increases.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a power amplification circuit, a differential power amplification circuit. BACKGROUND

[0002] There is known a power amplification circuit that includes a plurality of final-stage transistors with their emitters grounded, and a bias circuit that supplies a base bias to each of the final-stage transistors, and that inputs a high-frequency signal to the base of each of the final-stage transistors through a capacitor (see, for example, Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2001-274636 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the invention described in Patent Literature 1, the final-stage transistors need to have emitters with a large area in order to obtain a large output current. Therefore, in the invention described in Patent Literature 1, the parasitic capacitance between the base and the emitter in the final-stage transistors becomes large, and thus the impedance becomes small with respect to a signal in a high-frequency band. Thus, in the invention described in Patent Literature 1, there is a problem that the impedance of the final-stage transistors has a frequency characteristic, and that realization of a wide-band characteristic is hindered.

[0008] In addition, in the invention described in Patent Literature 1, since the impedance becomes small with respect to a signal in a high-frequency band, the capacitance of a capacitor for bias cutoff that is connected in series to the final-stage transistors is reduced. That is, in the invention described in Patent Literature 1, it is necessary to increase the size of the capacitor for bias cutoff, and there is a problem that the scale of the circuit becomes large.

[0009] Therefore, an object of the present disclosure is to provide a power amplification circuit that improves the input impedance with respect to a high-frequency signal.

[0010] MEANS FOR SOLVING THE PROBLEM

[0011] The power amplification circuit according to one aspect of the present application includes: a first transistor whose base or gate is supplied with a high-frequency signal through a capacitor and with a bias current through a resistance element; a second transistor whose emitter or source is connected to the base or gate of the first transistor and whose collector or drain is connected to an output terminal; and a third transistor whose collector or drain is connected to the base or gate of the first transistor and whose emitter or source is connected to a reference potential, the third transistor being configured to increase a current flowing to the collector or drain thereof as a current flowing to the collector or drain of the second transistor increases.

[0012] Effects of the Invention

[0013] According to the present disclosure, it is possible to provide a power amplification circuit that increases input impedance with respect to a high-frequency signal. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a configuration diagram showing an example of the configuration of the power amplification circuit of the present embodiment.

[0015] Figure 2 is a graph showing an example of the relationship between frequency and input impedance of the power amplification circuit of the first comparative example and the power amplification circuit of the present embodiment.

[0016] Figure 3 is a graph showing an example of the relationship between frequency and gain of the power amplification circuit of the first comparative example and the power amplification circuit of the present embodiment.

[0017] Figure 4 is a graph showing an example of the relationship between frequency and stability of the power amplification circuit of the first comparative example and the power amplification circuit of the present embodiment.

[0018] Figure 5 is a graph showing an example of the power amplification circuit in which a plurality of power amplification circuits are formed on the same semiconductor substrate.

[0019] Figure 6 is a configuration diagram showing an example of the configuration of the power amplification circuit of the first modified example.

[0020] Figure 7 is a configuration diagram showing an example of the configuration of the power amplification circuit of the second modified example.

[0021] Figure 8 is a configuration diagram showing an example of the configuration of the power amplification circuit of the third modified example.

[0022] Figure 9A is a configuration diagram showing an example of the configuration of the power amplification circuit of the fourth modified example.

[0023] Figure 9B is a configuration view showing an example of the configuration of the power amplification circuit of the fourth modification example.

[0024] Figure 10 is a configuration view showing an example of the configuration of the power amplification circuit of the fifth modification example.

[0025] Figure 11 is a configuration view showing an example of the configuration of the power amplification circuit of the sixth modification example.

[0026] Figure 12 is a configuration view showing an example of the configuration of the power amplification circuit of the seventh modification example.

[0027] Figure 13 is a configuration view showing an example of the arrangement of the structural elements of the power amplification circuit of the present embodiment.

[0028] Figure 14 is a view showing an example of the configuration of the power amplification circuit of the first comparative example.

[0029] Figure 15 is a view showing an example of the configuration of the power amplification circuit of the second comparative example.

[0030] Figure 16 is a view showing an example of the configuration of the power amplification circuit of the third comparative example.

[0031] Explanation of Reference Signs

[0032] 100... power amplification circuit,

[0033] 110, 120, 130, 140... transistor,

[0034] 150... capacitor,

[0035] 160... resistor. DETAILED DESCRIPTION

[0036] == Power Amplification Circuit 100 ==

[0037] Configuration

[0038] The power amplification circuit 100 is mounted on, for example, a portable telephone, and amplifies the power of a signal to be transmitted to a base station. The power amplification circuit 100 can amplify, for example, the power of a signal of a communication standard of 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, LTE-Advanced Pro, 6G (sixth generation mobile communication system), and the like. Note that the communication standard of the signal amplified by the power amplification circuit 100 is not limited thereto. The power amplification circuit 100 amplifies an input signal RFin and outputs an output signal RFout. The input signal is a radio frequency (RF) signal, and the frequency of the input signal is, for example, several GHz to several tens of GHz.

[0039] The power amplification circuit 100 of the present embodiment is an amplification circuit having a high input impedance. Referring to FIG. 1, the power amplification circuit 100 includes a transistor 110, a transistor 120, a transistor 130, a transistor 140, a capacitor 150, and a resistor 160. The power amplification circuit 100 amplifies an input signal RFin and outputs an output signal RFout. The input signal is a radio frequency (RF) signal, and the frequency of the input signal is, for example, several GHz to several tens of GHz. Figure 1 The structure of the power amplification circuit 100 will be described. Figure 1 is a structural diagram illustrating an example of the structure of the power amplification circuit 100 of the present embodiment. As shown in FIG. 1, the power amplification circuit 100 includes, for example, a transistor 110, a transistor 120, a transistor 130, a transistor 140, a capacitor 150, and a resistor 160. Note that although not particularly mentioned below, the collector of the transistor 110 and the collector of the transistor 120 in the power amplification circuit 100 of the present embodiment are connected to a terminal (not shown) of an external power supply through an output terminal 102. Figure 1

[0040] The transistors 110 to 140 are, for example, transistors that realize a high input impedance by being connected to each other. Hereinafter, as an example, a case where the transistors 110 to 140 are bipolar transistors will be described. Note that the transistors 110 to 140 can also be field effect transistors. In this case, the base of the transistors 110 to 140 is replaced with the gate, the collector of the transistors 110 to 140 is replaced with the drain, and the emitter of the transistors 110 to 140 is replaced with the source.

[0041] ​The transistor 110 is a transistor that amplifies the input signal RFin. At the base of the transistor 110, the input terminal 101 is connected through the capacitor 150. In addition, the base is supplied with a bias current from the bias circuit 103 through the resistor 160. The emitter of the transistor 110 is connected to the base of the transistor 120. In addition, the emitter can be connected to the collector of the transistor 140, for example. The collector of the transistor 110 is connected to the collector of the transistor 120. In addition, the collector of the transistor 110 can be connected to the output terminal 102, for example. In this way, the transistor 110 amplifies the input signal RFin by using an emitter follower circuit, and can increase the input impedance. Furthermore, since the transistor 110 is an emitter follower circuit, the output impedance can be reduced, so the voltage drop of the base current of the transistor 120 can be reduced.

[0042] The transistor 120 is a transistor that amplifies the input signal RFin amplified by the transistor 110 and outputs the output signal RFout. The transistor 120 is a transistor that is Darlington-connected to the transistor 110. Specifically, the emitter of the transistor 110 is connected to the base of the transistor 120. In addition, the base can be connected to the base of the transistor 130, for example. In addition, the base can be connected to the collector of the transistor 140, for example. The collector of the transistor 120 is connected to the output terminal 102. The emitter of the transistor 120 can be connected to a reference potential. The reference potential is ground, for example.

[0043] The transistor 130 is a transistor that increases the input impedance of the transistor 110 and suppresses thermal runaway of the transistor 120. The emitter of the transistor 130 is connected to a reference potential. The base of the transistor 130 is connected to the base of the transistor 120. In addition, the base is connected to the emitter of the transistor 110. The collector of the transistor 130 is connected to the base of the transistor 110. In the present embodiment, the transistor 130 and the transistor 120 form a mirror circuit. That is, the transistor 130 functions as a constant current source in the power amplifier circuit 100. Thereby, the base current of the transistor 110 can be introduced, so the input impedance of the transistor 110 can be increased. Therefore, the emitter current of the transistor 110 can be reduced, so the base current of the transistor 120 can be reduced and thermal runaway can be suppressed. Here, it is desirable to arrange the transistor 130 and the transistor 110 on the same semiconductor substrate so that they become the same temperature by thermal coupling. Thereby, the collector current of the transistor 130 increases in correspondence with the increase in the current of the transistor 120, so the base current of the transistor 110 decreases, and thermal runaway can be suppressed. Note that the operation of suppressing thermal runaway is described later.

[0044] The transistor 140 is a transistor for causing the transistor 110 to operate as an emitter follower. In other words, the transistor 140 is a transistor for increasing the current of the emitter of the transistor 110. The base of the transistor 140 is connected to the base of the transistor 130. The collector of the transistor 140 is connected to the emitter of the transistor 110. The base and the collector of the transistor 140 are connected. The emitter of the transistor 140 is connected to a reference potential. Thus, the transistor 140 can increase the emitter current of the transistor 110, and thus, can cause the transistor 110 to operate as an emitter follower to increase the input impedance. Note that the transistor 140 can be omitted.

[0045] The capacitor 150 is a coupling capacitor connected between the input terminal 101 and the base of the transistor 110. Note that in Figure 1 , the capacitor 150 is provided inside the power amplification circuit 100, but can be provided outside the power amplification circuit 100.

[0046] The resistor 160 is a resistive element connected between the bias circuit 103 and the base of the transistor 110. Note that in Figure 1 , the resistor 160 is provided inside the power amplification circuit 100, but can be provided outside the power amplification circuit 100.

[0047] <Comparison Example>

[0048] Referring to Figure 14 , the power amplification circuit 1000 of the first comparison example will be described. Figure 14 is a diagram illustrating an example of the structure of the power amplification circuit 1000 of the first comparison example. As Figure 14 indicated, the power amplification circuit 1000 includes, for example, a transistor 1100, a capacitor 1200, and a resistor 1300. The transistor 1100, the capacitor 1200, and the resistor 1300 are the same as the transistor 120, the capacitor 150, and the resistor 160 illustrated in Figure 1 . The base of the transistor 1100, which is the transistor of the final stage, is connected to the input terminal 1001 through the capacitor 1200, unlike the transistor 120.

[0049] Figure 14The power amplification circuit 1000 shown has a problem of an increase in the size of the circuit. Specifically, in the power amplification circuit 1000, unlike the power amplification circuit 100, the transistor 1100 is not Darlington-connected. Therefore, the base current of the transistor 1100 is significantly smaller in the power amplification circuit 1000 than in the power amplification circuit 100. Therefore, the input impedance of the transistor 1100 is significantly smaller. In the power amplification circuit 1000, the capacitance of the capacitor 1200 is determined so that the impedance of the capacitor 1200 with respect to the input impedance of the transistor 1100 does not increase for high-frequency signals. That is, in the case where the input impedance of the transistor 1100 is small, the capacitance needs to be increased, and therefore, the size of the capacitor 1200 needs to be increased. Therefore, in the power amplification circuit 1000, the size of the circuit increases.

[0050] Next, with reference to Figure 15 The power amplification circuit 2000 of the second comparative example will be described. Figure 15 is a diagram showing an example of the structure of the power amplification circuit 2000 of the second comparative example. As Figure 15 shown, the power amplification circuit 2000 is obtained, for example, by synthesizing the plurality of power amplification circuits 2100 to 2300 of the first comparative example on the same semiconductor substrate.

[0051] In the power amplification circuit 2000, there is a possibility that oscillation occurs in the plurality of amplification circuits 2100 to 2300. Specifically, in the power amplification circuit 2000, for example, in the case where the high-order harmonic current amplified by the amplification circuit 2100 flows backward to the collectors of the amplification circuits 2100 and 2200, the base of the amplification circuit 2100 is supplied again. At this time, in the case where the high-frequency current supplied to the base of the amplification circuit 2100 and the current supplied again to the base of the amplification circuit 2100 show a difference in one wavelength, the power amplification circuit 2000 oscillates.

[0052] Next, with reference to Figure 16 The power amplification circuit 3000 of the third comparative example will be described. Figure 16 is a diagram showing an example of the structure of the power amplification circuit 3000 of the third comparative example. As Figure 16 shown, the power amplification circuit 3000 is an amplification circuit composed of transistors that are Darlington-connected. The power amplification circuit 3000 includes a transistor 3100, a transistor 3200, a capacitor 3300, and a resistor 3400. The connection relationship of the transistor 3100, the transistor 3200, the capacitor 3300, and the resistor 3400 is the same as that of the transistor 110, the transistor 120, the capacitor 150, and the resistor 160, and therefore, the description thereof is omitted.

[0053] In the power amplification circuit 3000, there is a problem that thermal runaway occurs. Specifically, the transistor 3200 increases in temperature as the power consumption increases, and thus the voltage increases. In this case, the emitter potential of the transistor 3100 decreases when a constant voltage bias voltage is applied to the base of the transistor 3100, and thus the voltage between the base and the emitter of the transistor 3100 increases. In this way, the base current of the transistor 3100 increases. Moreover, since the base current of the transistor 3100 becomes Hfe (transistor amplification rate) times, the base current of the transistor 3200 increases. Therefore, the collector current of the transistor 3200 increases. As a result, the power consumption of the transistor 3200 further increases, and the above process is repeated to cause thermal runaway.

[0054] Operation

[0055] Return Figure 1 The operation of the power amplification circuit 100 will be described in comparison with the power amplification circuits 1000, 2000, and 3000 of the comparative examples.

[0056] As Figure 1 shown, the input signal RFin is supplied to the base of the transistor 110 through the capacitor 150. The transistor 110 amplifies the input signal RFin through an emitter follower and supplies it to the transistor 120. In addition, the emitter current of the transistor 110 is supplied as the collector current of the diode-connected transistor 140. As a result, the input impedance of the transistor 110 of the emitter follower can be increased. Moreover, the emitter current of the transistor 110 is supplied to the base of the transistor 130. The transistor 130 operates as a constant current source because it forms a mirror circuit with the transistor 140. Since the collector current flowing to the transistor 130 is constant, the current supplied from the bias circuit 103 does not become too small, and thus the transistor 130 increases the noise immunity of the power amplification circuit 100. As a result, the input impedance of the power amplification circuit 100 can be increased as described above, and thus the capacitor 150 can be reduced, so that the circuit can be reduced.

[0057] Here, the case where the input impedance of the power amplification circuit 100 is higher than that of the power amplification circuit 1000 of the first comparative example shown in FIG. 10 will be described with reference to FIG. 11. Figure 2 Figure 14 is higher than that of the power amplification circuit 1000 of the first comparative example shown in FIG. 10 will be described with reference to FIG. 11. Figure 2 is a graph showing an example of the relationship between the frequency and the input impedance of the power amplification circuit 1000 of the first comparative example and the power amplification circuit 100 of the present embodiment. In Figure 2 , the X axis is the frequency of a high-frequency signal, and the Y axis is the input impedance. As Figure 2 ​As shown, the input impedance of the power amplifier circuit 1000 in the first comparative example decreases as the frequency of the high-frequency signal increases. That is, in the power amplifier circuit 1000, the input impedance has frequency characteristics, making it difficult to match with a wide bandwidth, thus hindering its wide bandwidth performance. On the other hand, the input impedance of the power amplifier circuit 100 increases from the lower frequency band of the high-frequency signal towards 3.5 GHz. Even above 3.5 GHz, the input impedance decreases gradually. That is, in the power amplifier circuit 100, a high input impedance can be maintained over a wide bandwidth, thus enabling operation suitable for wide bandwidth operation.

[0058] Additionally, refer to Figure 3 To illustrate the gain of power amplifier circuit 100 and Figure 14 The gain of the power amplifier circuit 1000 in the first comparative example shown is higher. Figure 3 This is a diagram illustrating an example of the frequency-gain relationship between the power amplifier circuit 1000 of the first comparative example and the power amplifier circuit 100 of this embodiment. Figure 3 In this diagram, the X-axis represents the frequency of the high-frequency signal, and the Y-axis represents the gain. As an example, the gain is calculated by dividing the maximum effective power gain by the maximum stable gain. Figure 3 As shown, in the first comparative example, the power amplifier circuit 1000 experiences a larger drop in gain in frequency bands where the frequency of the high-frequency signal is greater than approximately 0.8 GHz. On the other hand, the gain of the power amplifier circuit 100 decreases by a fixed percentage depending on the frequency of the high-frequency signal. Therefore, the gain of the power amplifier circuit 1000 in the first comparative example is lower than that of the power amplifier circuit 100 in frequency bands where the frequency of the high-frequency signal exceeds 2.5 GHz. In other words, compared to the power amplifier circuit 1000 in the first comparative example, the power amplifier circuit 100 can improve gain within the frequency band used by the communication device.

[0059] Additionally, refer to Figure 4 To illustrate the stability of the power amplifier circuit 100 and Figure 14 The power amplifier circuit 1000 in the first comparative example shown is higher than that. Figure 4 This is a diagram illustrating an example of the relationship between frequency and stability between the power amplifier circuit 1000 of the first comparative example and the power amplifier circuit 100 of this embodiment. Figure 4 In this diagram, the X-axis represents the frequency of the high-frequency signal, and the Y-axis represents a stability index (e.g., the k-factor). A stability index is, for example, used to determine the oscillation capability of a power amplifier circuit; a value greater than 1 is considered stable. Figure 4As shown, the power amplification circuit 1000 of the first comparative example is stable in a frequency band in which the frequency of the high-frequency signal is larger than 7.0 GHz. On the other hand, the power amplification circuit 100 is stable in a frequency band in which the frequency is larger than 1.0 GHz. That is, the power amplification circuit 100 can improve stability in a frequency band used by a communication device, as compared with the power amplification circuit 1000 of the first comparative example.

[0060] In addition, with reference to Figure 5 , a case in which oscillation can be suppressed as compared with the power amplification circuit 2000 of the second comparative example shown in Figure 15 is described. Figure 5 is a view showing an example of a power amplification circuit in which a plurality of power amplification circuits 100 are constituted on the same semiconductor substrate. As described above, in the power amplification circuit 2000 of the second comparative example shown in Figure 15 , a position at which oscillation occurs, Figure 5 , the plurality of power amplification circuits 100 suppress oscillation because the isolation degree of the transistor 120 of each power amplification circuit 100 is high. That is, in the plurality of power amplification circuits 100 shown in Figure 5 , in a case in which the high-order harmonic current amplified by the transistor 110 of a prescribed power amplification circuit 100 flows back to the collector of the transistor 110 of another power amplification circuit 100, the high-order harmonic current that flows back is isolated by the transistor 110. Specifically, the current that flows back to the collector of the transistor 110 is terminated at ground via the transistor 120 that is Darlington-connected to the transistor 110. Therefore, the current that flows back to the collector of the transistor 110 can be suppressed from reaching the base of the transistor 110. That is, the high-order harmonic current that flows back is not supplied again to the base of the transistor 110 of the prescribed power amplification circuit 100. Thus, oscillation can be suppressed.

[0061] Returning to Figure 1 , in a case in which the power amplification circuit 100 is operating and the consumption power of the transistor 120 increases, the temperature of the transistor 120 rises, and therefore the rise voltage becomes small and the base current of the transistor 110 increases. Thus, the collector current of the transistor 120 increases. In this way, as described above, in the power amplification circuit 3000 of the third comparative example shown in Figure 16 , thermal runaway is reached. On the other hand, in the power amplification circuit 100, when the temperature of the transistor 120 rises and the base current becomes large, the collector current of the transistor 130 becomes large. Thus, by introducing the base current of the transistor 110 to the collector of the transistor 130, the base current of the transistor 110 can be reduced. Thus, thermal runaway can be suppressed in the power amplification circuit 100.

[0062] First Modification

[0063] With reference to Figure 6The power amplification circuit 100a of the first modification example will be described. Figure 6 is a configuration view showing one example of the configuration of the power amplification circuit 100a of the first modification example. The power amplification circuit 100a of the first modification example is compared with the power amplification circuit 3000 of the third comparative example shown in FIG. 3. Figure 16 is able to suppress thermal runaway compared with the power amplification circuit 3000 of the third comparative example shown in FIG. 3. As shown in FIG. 1, Figure 6 The power amplification circuit 100a includes, for example, a transistor 110a, a transistor 120a, a transistor 130a, a transistor 140a, a capacitor 150a, and a resistor 160a.

[0064] The transistor 110a is a transistor that amplifies an input signal RFin. At the base of the transistor 110a, an input terminal 101a is connected through the capacitor 150a. In addition, a bias current is supplied from a bias circuit 103a to the base through the resistor 160a. The emitter of the transistor 110a is connected to the base of the transistor 120a. The collector of the transistor 110a is connected to the collector of the transistor 120a. In addition, the collector of the transistor 110a can also be connected to an output terminal 102a. In this way, the transistor 110a is able to improve the input impedance by amplifying the input signal RFin using an emitter follower circuit. Furthermore, since the transistor 110a is configured by the emitter follower circuit, the output impedance is able to be reduced, so the voltage drop of the base current of the transistor 120a is able to be reduced.

[0065] The transistor 120a is a transistor that amplifies the input signal RFin amplified by the transistor 110a and outputs an output signal RFout. The emitter of the transistor 110a is connected to the base of the transistor 120a. The collector of the transistor 120a is connected to the output terminal 102a. The emitter of the transistor 120a can also be connected to a reference potential.

[0066] The transistor 130a and the transistor 140a are transistors for suppressing thermal runaway by introducing the base current of the transistor 110a. At least either one of the transistor 130a or the transistor 140a is arranged on the same semiconductor substrate as the transistor 120a so as to be thermally coupled with the transistor 120a. The base / collector of the transistor 130a is connected between, and the emitter is connected to a reference potential. The base and the collector of the transistor 140a are connected to the base of the transistor 110a. The emitter of the transistor 140a is connected to the collector of the transistor 130a.

[0067] Here, the operation of the power amplification circuit 100a will be described. When the consumption power of the transistor 120a increases, the temperature rises, and the rise voltage decreases. Due to this, the emitter potential of the transistor 110a decreases. Therefore, the voltage between the base and the emitter of the transistor 110a increases, so the base current increases. At this time, the transistors 130a and 140a are thermally coupled with the transistor 120a, so the temperature rise occurs similarly to the transistor 120a. In this way, the emitter potential of the transistors 130a and 140a decreases, and the voltage between the base and the emitter increases. Due to this, the transistors 130a and 140a introduce the base current of the transistor 110a, so the base current decreases. Therefore, the transistors 130a and 140a can suppress thermal runaway of the power amplification circuit 100a.

[0068] <Second Modification Example>

[0069] Referring to Figure 7 , the power amplification circuit 100b of the second modification example will be described. Figure 7 is a configuration view showing an example of the configuration of the power amplification circuit 100b of the second modification example. The power amplification circuit 100b of the second modification example can be miniaturized compared with the power amplification circuit 100 shown in Figure 1 .

[0070] As shown in Figure 7 , the power amplification circuit 100b is obtained by replacing the transistor 120 of the power amplification circuit 100 with a plurality of transistors 121b and 122b connected in parallel. The bases of the transistors 121b and 122b are connected to each other, the collectors are connected to the output terminal 102b, and the emitters are connected to the reference potential. In the power amplification circuit 100 shown in Figure 1 , in the case where one set of the transistors 110, 130, and 140 is connected with respect to one transistor 120, the design becomes too large, the cost increases, and the size becomes large. Therefore, as shown in Figure 7 , the power amplification circuit 100b includes a plurality of transistors 121b and 122b in order to obtain the desired output signal RFout. Due to this, the power amplification circuit can be miniaturized, and the cost in production can be reduced. Note that, in Figure 7 , two transistors 121b and 122b are connected in parallel, but the number of transistors connected in parallel is not limited.

[0071] <Third Modification Example>

[0072] Referring to Figure 8 , the power amplification circuit 100c of the third modification example will be described. Figure 8is a configuration view showing an example of the configuration of a power amplification circuit 100c of a third modification. The power amplification circuit 100c of the third modification is different from the power amplification circuit 100 shown in Figure 1 in that the design becomes easy. As shown in Figure 8 , the power amplification circuit 100c is obtained by replacing the transistor 140 of the power amplification circuit 100 with a resistor 140c. The resistance value of the resistor 140c is determined so that a desired current flows to the emitter of the transistor 110.

[0073] Fourth Modification

[0074] The fourth modification of the power amplification circuit 100 will be described with reference to Figure 9A , Figure 9B . Figure 9A , Figure 9B is a configuration view showing an example of the configuration of a power amplification circuit 100d of the fourth modification. The power amplification circuit 100d of the fourth modification is different from the power amplification circuit 100 shown in Figure 1 in that it has a structure capable of supplying a bias current to the transistor 120 particularly in the B class or C class operation. The power amplification circuit 100d includes, for example, a transistor 110d, a transistor 120d, a transistor 130d, a constant voltage circuit 131d, a resistor 132d, a resistor 140d, a capacitor 150d, and a resistor 160d. Here, the transistor 110d, the transistor 120d, the capacitor 150d, and the resistor 160d are the same as the transistor 110, the transistor 120, the capacitor 150, and the resistor 160 of the power amplification circuit 100, and thus the description thereof is omitted.

[0075] The collector of the transistor 130d is connected to the base of the transistor 110d, the emitter is connected to a reference potential, and the base is connected to the base of the transistor 110d through the constant voltage circuit 131d and the resistor 132d. The constant voltage circuit 131d is an electronic element that supplies a prescribed voltage. As shown in Figure 9A , the constant voltage circuit 131d may, for example, be obtained by connecting two diodes in series. Further, as shown in Figure 9BAs shown, the constant voltage circuit 131d can be configured, for example, as a voltage dividing circuit 131d1 including a resistor 131d2 and a resistor 131d3 connected in series, and a transistor 131d4 having its base connected to a connection point Cp of the resistor 131d2 and the resistor 131d3. The voltage dividing circuit 131d1 is connected, for example, at one end to the base of the transistor 110d via a resistor 132d, and at the other end to the base of the transistor 130d. The base of the transistor 131d4 is connected to the connection point Cp of the resistor 131d2 and the resistor 131d3, the collector is connected to the base of the transistor 110d via the resistor 132d, and the emitter is connected to the base of the transistor 130d. Note that the constant voltage circuit 131d can be a direct current power source, a transistor connected between the base and the collector, or a transistor connected between the base and the emitter, and is not particularly limited. The resistor 132d is connected at one end to the base of the transistor 110d, and at the other end to the constant voltage circuit 131d. The resistor 140d is a resistor element connected at one end to the emitter of the transistor 110d, and at the other end to a reference potential. The resistor 140d is a resistor element for increasing the emitter current of the transistor 110d. That is, the resistor 140d can increase the input impedance of the transistor 110d. The resistor 140d can be a transistor, for example. The resistor 160d is connected at one end to the bias circuit 103d, and at the other end to the base of the transistor 110d via the resistor 132d.

[0076] Here, the operation of the power amplification circuit 100d will be described. In the power amplification circuit 100d, the transistor 120d needs to be biased below the operating point so that the transistor 120d does not flow current in the case of performing class B or class C operation. In the power amplification circuit 100d, the voltage of the constant voltage circuit 131d is used as a reference to bias the transistor 120d below the operating point. Figure 1 In the power amplification circuit 100 shown, the base of the transistor 120 is connected to the base of the transistor 130 without passing through a transistor, and thus, in the case where the transistor 120 does not flow current, current cannot flow in the transistor 130, and the transistor 120 cannot be biased below the operating point. On the other hand, in the power amplification circuit 100d, the transistor 120d can be biased below the operating point with the voltage of the constant voltage circuit 131d as a reference.

[0077] Specifically, for example, in the case of class C operation, the transistor 120d does not flow current at all. That is, in class C operation, the base potential of the transistor 120d needs to be below the rise voltage. For example, in the case of class C operation, the base potential of the transistor 120d needs to be below the rise voltage, and the base potential of the transistor 130d needs to be below the rise voltage. In the power amplification circuit 100d, the base potential of the transistor 120d can be below the rise voltage, and the base potential of the transistor 130d can be below the rise voltage. Figure 1In the power amplifier circuit 100 shown, the base of the transistor 120 is not connected to the base of the transistor 130 via a transistor, and therefore the base potential of the transistor 120 does not become lower than the rise voltage. On the other hand, in the power amplifier circuit lOOd, a base-emitter voltage that is three times (hereinafter referred to as "3Vbe") is generated, for example, by the transistor l30d and the constant voltage circuit l3Id. Then, 3Vbe is dropped by the resistor l32d and supplied to the transistor l lOd. Thus, in the power amplifier circuit lOOd, the bias of the transistor l20d, which is Darlington-connected to the transistor l lOd, can be set lower than the base-emitter voltage Vbe.

[0078] Fifth Modification

[0079] Reference Figure 10 The fifth modification of the power amplifier circuit 100 will be described. Figure 10 is a configuration diagram showing an example of the configuration of the power amplifier circuit lOOe of the fifth modification. In the power amplifier circuit lOOe of the fifth modification, current flow from the transistor l lOe to the output terminal 102e can be prevented. In the power amplifier circuit 100, when the input signal RFin is large, the collector potential of the transistor 120 approaches 0V, and therefore the base potential of the transistor 110 becomes high, and current sometimes flows from the base of the transistor 110 to the output terminal 102e.

[0080] On the other hand, the power amplifier circuit lOOe has the diode 170e whose cathode is connected to the collector of the transistor l lOe and whose anode is connected to the collector of the transistor 120e. That is, in the power amplifier circuit lOOe, when current flows from the base of the transistor l lOe toward the output terminal 102e, the diode 170e becomes reverse-biased, and therefore no current flows in the output terminal 102e. Thus, the operation of the power amplifier circuit 100 is stabilized.

[0081] Sixth Modification

[0082] Reference Figure 11 The sixth modification of the power amplifier circuit 100 will be described. Figure 11 is a configuration diagram showing an example of the configuration of the power amplifier circuit lOOe of the fifth modification. In the power amplifier circuit lOOe of the fifth modification, current flow from the transistor l lOe to the output terminal 102e can be prevented. In the power amplifier circuit 100, when the input signal RFin is large, the collector potential of the transistor 120 approaches 0V, and therefore the base potential of the transistor 110 becomes high, and current sometimes flows from the base of the transistor 110 to the output terminal 102e. Figure 11 In the power amplifier circuit lOOe, the collector of the transistor l lOe is not connected to the output terminal 102, but is connected to the external power supply 104e. That is, in the power amplifier circuit lOOe, no signal is taken out from the collector of the transistor l lOe.

[0083] Seventh Modification

[0084] Reference Figure 12 A seventh modification of the power amplification circuit 100 will be described. Figure 12 is a configuration view showing one example of the configuration of the power amplification circuit 100g of the seventh modification. The power amplification circuit 100g of the seventh modification is a differential power amplification circuit including the power amplification circuit 100P and the power amplification circuit 100N. The power amplification circuit 100P, for example, can also be composed of a plurality of elements, and is input with the input signal +RFin of a prescribed phase. On the other hand, the power amplification circuit 100N, for example, can also be composed of a plurality of elements, and is input with the input signal -RFin which is inverted from the input signal +RFin. Note that the "inversion" is, for example, a phase difference of 135° to 225° with respect to the input signal +RFin. Thus, the wideband of the power amplification circuit 100g can be realized. In addition, since the power amplification circuit 100g is composed differentially, it is not necessary to provide a decoupling capacitor at the "P" point of the power amplification circuit 100. Thus, it is possible to avoid the large size and the delay caused by the provision of the decoupling capacitor. Furthermore, in the power amplification circuit 100g, in the case where a baseband signal is input from the bias circuit 103, for example, for controlling the base potential of the peak amplifier of the Doherty amplifier based on the envelope line of the high-frequency signal, it is possible to avoid the delay caused by the decoupling capacitor. Figure 12

[0085] Arrangement

[0086] Reference Figure 13 An arrangement of the structural elements of the power amplification circuit 100 will be described. Figure 13 is a configuration view showing one example of the arrangement of the structural elements of the power amplification circuit 100 of the present embodiment. In the present embodiment, for example, the X axis is an axis in one direction on the main surface of the semiconductor substrate 200, the Y axis is an axis orthogonal to the X axis on the main surface of the semiconductor substrate 200, and the Z axis is an axis orthogonal to the X axis and the Y axis. As shown in Figure 13 Figure 13 ​​As shown, the transistors constituting the power amplifier circuit 100 are formed on the semiconductor substrate 200. The semiconductor substrate 200 is connected to the prescribed substrate 400 by the bump 300, for example. The semiconductor substrate 200 is formed of a material different from the bump 300, and thus the coefficient of thermal expansion of the semiconductor substrate 200 is different from that of the bump 300. Therefore, the semiconductor substrate 200 is stressed from the bump 300 which expands and shrinks in accordance with a change in heat. That is, the transistors constituting the power amplifier circuit 100 formed on the semiconductor substrate 200 are stressed from the bump 300. Also, when the stress received between the transistors constituting the power amplifier circuit 100 differs, the characteristics between the transistors differ, and thus the operation of the power amplifier circuit 100 becomes unstable. Therefore, in the power amplifier circuit 100, at least a part of the final-stage transistor 120 and at least a part of the transistors 130, 140 for input impedance adjustment are arranged to overlap the bump in the XY plane. Thus, at least either one of the final-stage transistor 120 and the transistors 130, 140 receives the same stress as the bump 300, and thus the operation of the power amplifier circuit 100 is stable.

[0087] Specifically, in the power amplifier circuit 100, when the transistor 120 generates heat, the semiconductor substrate 200 expands, and thus the transistor 120 is stressed from the bump 300. At this time, the base / emitter voltage of the transistor 120 changes in accordance with the stress. In the power amplifier circuit 100, the transistor 120 and the transistors 130, 140 overlap the same bump 300 in the XY plane, and thus the transistors 130, 140 are stressed equally to the transistor 120. Therefore, the change in the base / emitter voltage of the transistors 130, 140 is equal to that of the transistor 120. Thus, in the power amplifier circuit 100, even if the stress changes in accordance with a change in heat, the operation is stable.

[0088] Further, in the power amplifier circuit 100, it is desirable that all of the transistor 120, the transistor 130, and the transistor 140 overlap the same bump 300. Thus, the operation of the power amplifier circuit 100 is more stable.

[0089] Further, in the power amplifier circuit 100d, it is desirable that all of the transistor 120d, the transistor 130d, and the constant voltage circuit 131d overlap the same bump 300. Thus, the operation of the power amplifier circuit 100 is more stable.

[0090] Further, in the power amplifier circuit 100, 100d, it is also possible to arrange that the transistor 110, 110d and the transistor 120, 120d overlap the same bump 300. Thus, the operation of the power amplifier circuit 100, 100d is more stable.

[0091] SUMMARY

[0092] The power amplification circuit 100 includes:

[0093] The transistor 110 (first transistor) has a high-frequency signal supplied to its base through the capacitor 150 and a bias current supplied to its base through the resistor 160 (resistor element). The transistor 120 (second transistor) has its emitter connected to the base of the transistor 110 (first transistor) and its collector connected to the output terminal 102. The transistor 130 (third transistor) has its base connected to the collector of the transistor 110 (first transistor) and its emitter connected to a reference potential (e.g., ground). The transistor 130 (third transistor) is configured to increase the current flowing to its collector in response to an increase in the current flowing to the emitter of the transistor 110 (first transistor). Thus, the power amplification circuit 100 can achieve a high input impedance. In addition, the power amplification circuit 100 can increase the input impedance, and thus, can reduce the capacitor 150, and thus, can reduce the circuit.

[0094] In addition, the power amplification circuit 100 further includes an element having one end connected to the emitter of the transistor 110 (first transistor) and the other end connected to a reference potential, so that the transistor 110 (first transistor) operates as an emitter follower. Thus, the power amplification circuit 100 can increase the emitter current of the transistor 110 of the emitter follower, and thus, can increase the input impedance of the transistor 110.

[0095] In addition, the element of the power amplification circuit 100 is the transistor 140 (fourth transistor) having its collector connected to the emitter of the transistor 110 (first transistor) and its emitter connected to a reference potential. Thus, the power amplification circuit 100 can increase the emitter current of the transistor 110, and thus, can operate the transistor 110 as an emitter follower to increase the input impedance.

[0096] In addition, the element of the power amplification circuit 100c is the resistor 140c (first resistor element). Thus, the power amplification circuit 100c can increase the emitter current of the transistor 110 of the emitter follower, and thus, can increase the input impedance of the transistor 110.

[0097] Further, the power amplification circuit 100d further includes a resistor 132d (second resistance element) having one end connected to the base of the transistor 110d (first transistor), and a constant voltage circuit 131d having one end connected to the other end of the resistor 132d (second resistance element) and the other end connected to the base of the transistor 130d (third transistor). Thus, the power amplification circuit 100d can set the bias of the transistor 120d based on the voltage of the transistor 130d and the constant voltage circuit 131d even when performing class B or class C operation.

[0098] Further, the constant voltage circuit 131d of the power amplification circuit 100d is at least one diode having an anode connected to one end of the resistor 132d (second resistance element) and a cathode connected to the base of the transistor 130d (third transistor). Thus, the constant voltage source can be easily implemented.

[0099] Further, the constant voltage circuit 131d of the power amplification circuit 100d includes a voltage dividing circuit 131d including a resistor 131d2 (third resistance element) and a resistor 131d3 (fourth resistance element), and having one end connected to the other end of the resistor 132d (second resistance element) and the other end connected to the base or gate of the transistor 130d (third transistor), and a transistor 131d4 (fifth transistor) having a collector or drain connected to the other end of the resistor 132d (second resistance element), a base or gate connected to a connection point Cp of the resistor 131d2 (third resistance element) and the resistor 131d3 (fourth resistance element), and an emitter or source connected to the base or gate of the transistor 130d (third transistor). Thus, the constant voltage source can be easily implemented.

[0100] Further, the diode 131d of the power amplification circuit 100d includes a first diode having a cathode connected to the base of the transistor 130d (third transistor), and a second diode having a cathode connected to an anode of the first diode and an anode connected to one end of the resistor 132d (second resistance element). Thus, the constant voltage source can be easily implemented.

[0101] Further, the base of the transistor 130 (third transistor) of the power amplification circuit 100 is connected to the base of the transistor 120 (second transistor). Thus, in the power amplification circuit 100, the base current of the transistor 110 can be introduced, and thus the input impedance of the transistor 110 can be improved. Further, the emitter current of the transistor 110 is small, and thus the base current of the transistor 120 is small, and thermal runaway is suppressed.

[0102] Further, the power amplification circuit 100e further includes a diode 170e (third diode) having a cathode connected to the collector or drain of the transistor 110e (first transistor) and an anode connected to the collector of the transistor 120e (second transistor). Thus, in the power amplification circuit 100e, even if the input signal RFin is large, no current flows from the base of the transistor 110e to the output terminal 102e, and thus the operation of the circuit is stable.

[0103] Further, the collector of the transistor 110f (first transistor) of the power amplification circuit 100f is connected to an external power supply 104f (bias power supply). Thus, the power amplification circuit 100f can prevent current from flowing from the transistor 110f to the output terminal 102f.

[0104] Further, the transistor 120 (second transistor) of the power amplification circuit 100b includes a plurality of transistors 121b, 122b connected in parallel. Thus, the power amplification circuit 100b can be miniaturized, and the cost of production can be reduced.

[0105] Further, the transistors 110 to 110d, the transistors 120 to 120d, and the transistors 130 to 130d of the power amplification circuits 100 to 100d are bipolar transistors. Thus, the power amplification circuits 100 to 100d can increase the input impedance of the transistors 110 to 110d.

[0106] Further, the power amplification circuit 100 is formed such that at least a portion of the transistor 120 (second transistor) and at least a portion of the transistor 130 (third transistor) formed on the semiconductor substrate 200 overlap the prescribed bump 300 that connects the semiconductor substrate 200 and a prescribed substrate 400 in plan view. Thus, at least either one of the transistor 120 and the transistor 130 of the final stage receives the same stress between the transistor 120 and the transistor 130 and the bump 300, and thus the operation of the power amplification circuit 100 is stable.

[0107] Further, the power amplification circuit 100g can avoid the increase in size and delay due to the provision of a decoupling capacitor by a differential amplification circuit including a power amplification circuit 100P (first power amplification circuit) supplied with an input signal +RFin (first high harmonic signal) of a prescribed phase and a power amplification circuit 100N (second power amplification circuit) supplied with an input signal -RFin (second high harmonic signal) that is inverted from the input signal +RFin.

[0108] The embodiments described above are used to facilitate understanding of the present disclosure, and are not intended to limit the interpretation of the present disclosure. The present disclosure can be changed or modified within the scope of the gist thereof, and the present disclosure also includes equivalents thereof. That is, a mode obtained by appropriately designing changes to the embodiments by those skilled in the art is included in the scope of the present disclosure as long as it has the features of the present disclosure. The elements and their configurations and the like possessed by the embodiments are not limited to the illustrated cases, and can be appropriately changed.

Claims

1. A power amplification circuit comprising: a first transistor whose base or gate is supplied with a high-frequency signal through a capacitor and whose emitter or source is supplied with a bias from a bias circuit through a resistive element; a second transistor whose base or gate is connected to the emitter or source of the first transistor and whose collector or drain is connected to an output terminal; and a third transistor whose collector or drain is connected to the base or gate of the first transistor and whose emitter or source is connected to a reference potential, the third transistor being arranged such that, in the event that the current flowing to the collector or drain of the second transistor increases, the current flowing to the collector or drain of the third transistor increases, the resistive element being connected between the bias circuit and the base or gate of the first transistor.

2. The power amplification circuit according to claim 1, wherein the power amplification circuit further comprises an element connected at one end to the emitter or source of the first transistor and at the other end to the reference potential, such that the current of the emitter or source of the first transistor increases.

3. The power amplification circuit according to claim 2, wherein the element is a fourth transistor, the collector or drain of the fourth transistor is connected to the emitter or source of the first transistor, and the emitter or source of the fourth transistor is connected to the reference potential.

4. The power amplification circuit according to claim 2, wherein the element is a first resistive element.

5. The power amplification circuit according to any one of claims 1 to 4, wherein the power amplification circuit further comprises: a second resistive element whose one end is connected to the base or gate of the first transistor; and a constant voltage circuit whose one end is connected to the other end of the second resistive element and whose other end is connected to the base or gate of a third transistor.

6. The power amplification circuit according to claim 5, wherein the constant voltage circuit includes at least one diode whose anode is connected to the one end of the second resistive element and whose cathode is connected to the base or gate of the third transistor.

7. The power amplification circuit according to claim 5, wherein the constant voltage circuit includes: a voltage dividing circuit composed of a third resistive element and a fourth resistive element, the voltage dividing circuit having one end connected to the other end of the second resistive element and the other end connected to the base or gate of the third transistor; and a fifth transistor whose collector or drain is connected to the other end of the second resistive element, whose base or gate is connected to the connection point of the third resistive element and the fourth resistive element, and whose emitter or source is connected to the base or gate of the third transistor.

8. The power amplification circuit according to any one of claims 1 to 4, wherein the base or gate of the third transistor is connected to the base or gate of the second transistor.

9. The power amplification circuit according to any one of claims 1 to 4, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The power amplification circuit further includes a third diode having a cathode connected to the collector or drain of the first transistor and an anode connected to the collector or drain of the second transistor.

10. The power amplification circuit according to any one of claims 1 to 4, wherein the collector or drain of the first transistor is connected to a prescribed power supply.

11. The power amplification circuit according to any one of claims 1 to 4, wherein the second transistor includes a plurality of transistors connected in parallel.

12. The power amplification circuit according to any one of claims 1 to 4, wherein the first transistor, the second transistor, and the third transistor are bipolar transistors.

13. The power amplification circuit according to any one of claims 1 to 4, wherein the power amplification circuit is formed such that at least a portion of the second transistor and at least a portion of the third transistor formed on a semiconductor substrate overlap, in plan view, a prescribed bump connecting the semiconductor substrate to a prescribed substrate.

14. A differential power amplification circuit, comprising: a first power amplification circuit according to any one of claims 1 to 13, which is supplied with a first input signal of a prescribed phase; and a second power amplification circuit according to any one of claims 1 to 13, which is supplied with a second input signal that is inverted from the first input signal.

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