Power amplifier

Abstract

Provided is a power amplifier capable of suppressing breakdown of a transistor even when the amplitude of a high-frequency signal is large. A power amplifier having multiple stages of amplification units including transistors whose emitters are grounded, the power amplifier including: a first amplification unit having a first transistor that amplifies an input high-frequency signal; a second amplification unit having a second transistor that amplifies the output of the first amplification unit; a voltage detection circuit provided with at least an impedance element and provided between the first transistor and the second transistor; and a protection circuit that reduces a base bias current supplied to at least one of the first transistor and the second transistor on the basis of an output of a voltage detection circuit including the impedance element.

Description

Technical Field

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

[0002] A high-frequency power amplifier is known that connects a plurality of amplifier stages including transistors and amplifies a high-frequency signal. The power amplifier disclosed in Patent Document 1 includes a protection circuit connected to the output of the amplifier stage. The protection circuit becomes conductive when the voltage amplitude becomes greater than a certain given voltage, and extracts the base current of the transistor constituting the preceding amplifier stage. Thus, the protection circuit protects the transistor from being broken down.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent No. 4685836

[0006] However, in the above-mentioned power amplifier, when the amplitude of the high-frequency signal is large and the protection circuit is repeatedly turned on and off, it may be impossible to suppress the breakdown of the transistor. Summary of the invention

[0007] Problem that the invention aims to solve

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a power amplifier capable of suppressing breakdown of a transistor even when the amplitude of a high-frequency signal is large.

[0009] Technical solutions to solve problems

[0010] In order to solve the above-mentioned problems and achieve the above-mentioned purpose, a power amplifier according to a certain embodiment of the present disclosure has a multi-stage amplifier section, wherein the amplifier section includes a transistor with an emitter grounded, wherein the power amplifier comprises: a first amplifier section having a first transistor for amplifying an input high-frequency signal; a second amplifier section having a second transistor for amplifying an output of the first amplifier section; a voltage detection circuit having at least an impedance element and arranged between the first transistor and the second transistor; and a protection circuit for reducing a base bias current provided to at least one of the first transistor and the second transistor based on the output of the voltage detection circuit including the impedance element.

[0011] Effects of the Invention

[0012] According to the present invention, even when the amplitude of a high-frequency signal is large, it is possible to suppress the breakdown of a transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1is a diagram showing a power amplifier of a comparative example.

[0014] Figure 2 It is a diagram showing a power amplifier according to the first embodiment of the present disclosure.

[0015] Figure 3 2 is a diagram showing an operation example of the voltage detection circuit.

[0016] Figure 4 It is a diagram showing an example of a state where a waveform is distorted.

[0017] Figure 5 This is a diagram showing the relationship between the detection voltage output from the voltage detection circuit, the extraction current extracted by the protection circuit, and the collector current of each transistor.

[0018] Figure 6 It is a diagram showing the relationship between the voltage level of the input high-frequency signal and the collector current.

[0019] Figure 7 It is shown for Figure 2 Figure 2 shows the voltage detection circuit of the power amplifier.

[0020] Figure 8 2 is a diagram showing a modified example of the voltage detection circuit.

[0021] Fig. 9 2 is a diagram showing a modified example of the voltage detection circuit.

[0022] Fig.10 2 is a diagram showing a modified example of the voltage detection circuit.

[0023] Fig.11 It is a diagram showing a first example of a level shift circuit and a protection circuit.

[0024] Fig.12 It is shown Fig.11 The waveform diagram of the level shift circuit and the protection circuit shown.

[0025] Fig.13 It is a diagram showing a second example of the level shift circuit and the protection circuit.

[0026] Fig.14 It is shown Fig.13 The waveform diagram of the level shift circuit and the protection circuit shown.

[0027] Fig.15 It is a diagram showing a third example of the level shift circuit and the protection circuit.

[0028] Fig.16 It is shown Fig.15 The waveform diagram of the level shift circuit and the protection circuit shown.

[0029] Fig.17 It is a diagram showing a fourth example of the level shift circuit and the protection circuit.

[0030] Fig.18 It is shown Fig.17 The waveform diagram of the level shift circuit and the protection circuit shown.

[0031] Fig.19 It is a diagram showing a fifth example of the level shift circuit and the protection circuit.

[0032] Fig. 20 It is shown Fig.19 The waveform diagram of the level shift circuit and the protection circuit shown.

[0033] Fig.21 It is a diagram showing a sixth example of the level shift circuit and the protection circuit.

[0034] Fig. 22 It is shown Fig.21 The waveform diagram of the level shift circuit and the protection circuit shown.

[0035] Fig.23 FIG. 1 is a diagram showing a first example of a combination of a level shift circuit and a protection circuit.

[0036] Fig.24 FIG. 2 is a diagram showing a second example of a combination of a level shift circuit and a protection circuit.

[0037] Fig.25 It is a diagram showing a power amplifier according to a second embodiment of the present disclosure.

[0038] Fig.26 It is a diagram showing a power amplifier according to a third embodiment of the present disclosure.

[0039] Fig. 27 1 is a diagram showing an example of a layout in which the power amplifier of the present disclosure is implemented on a substrate.

[0040] Fig.28 1 is a diagram showing an example of a layout in which the power amplifier of the present disclosure is implemented on a substrate.

[0041] Fig.29 1 is a diagram showing an example of a layout in which the power amplifier of the present disclosure is implemented on a substrate.

[0042] Description of Reference Numerals

[0043] 10, 10a, 10b, 10c: voltage detection circuit;

[0044] 20, 20a, 20b, 20c: level shift circuit;

[0045] 30, 30a, 30b: protection circuit;

[0046] 100, 100a~100f: power amplifier;

[0047] B11, B12, B13, B21, B22: bias circuit;

[0048] IB1, IB2: Bias input terminals;

[0049] L1, L2, L3: choke coils;

[0050] PA1, PA2, PA3, PA21, PA22: amplifier;

[0051] Pin: input terminal;

[0052] Pout, Pout1, Pout2: output terminals;

[0053] T: Balun transformer. DETAILED DESCRIPTION

[0054] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. In the following description of each embodiment, the same reference numerals are used for components that are the same or equivalent to other embodiments, and the description thereof is simplified or omitted. The present invention is not limited to each embodiment. In addition, the components of each embodiment include components that can be replaced and easily replaced by a person skilled in the art or substantially the same components. In addition, the structures described below can be appropriately combined. In addition, the structure can be omitted, replaced or changed without departing from the scope of the gist of the invention.

[0055] <First Embodiment>

[0056] Hereinafter, the first embodiment will be described. However, in order to facilitate understanding of the first embodiment, a comparative example will be described first.

[0057] (Structure of Comparative Example)

[0058] Figure 1 is a diagram showing a power amplifier 100 of a comparative example. Figure 1In the embodiment, the power amplifier 100 is a three-stage amplifier having amplifiers PA1, PA2, and PA3. That is, the power amplifier 100 has a first-stage amplifier PA1, a second-stage amplifier PA2, and a third-stage amplifier PA3. The amplifiers PA1, PA2, and PA3 amplify input high-frequency signals and output them to the subsequent stages in sequence. The amplifier PA1 is equivalent to the first amplifier of the present disclosure. The amplifier PA2 is equivalent to the second amplifier of the present disclosure. The amplifier PA3 is equivalent to the third amplifier of the present disclosure.

[0059] Amplifiers PA1, PA2, and PA3 all include transistors with grounded emitters. Amplifier PA1 includes a transistor Tr1 with grounded emitters, a capacitor C11 connected to the base of transistor Tr1, and resistors R11, R12, and R13. A bias current described later is provided to the base of transistor Tr1 via resistor R11. The emitter of transistor Tr1 is connected to a reference potential via resistor R13. As for the reference potential, a ground potential can be exemplified, but the present disclosure is not limited thereto. The same is true in the subsequent descriptions. The signal amplified by amplifier PA1 is output from the collector of transistor Tr1. A capacitor C10 and a resistor R10 are connected in series between the input and output of amplifier PA1. Transistor Tr1 is equivalent to the first transistor of the present disclosure.

[0060] The amplifier PA2 includes a transistor Tr2 with an emitter grounded, a capacitor C21 connected to the base of the transistor Tr2, and a resistor R21. A bias current described later is provided to the base of the transistor Tr2 via the resistor R21. The emitter of the transistor Tr2 is connected to a reference potential. The signal amplified by the amplifier PA2 is output from the collector of the transistor Tr2. The transistor Tr2 is equivalent to the second transistor of the present disclosure.

[0061] The amplifier PA3 includes a transistor Tr3 with an emitter grounded, a capacitor C31 connected to the base of the transistor Tr3, a capacitor C32 connected between the collector and the emitter of the transistor Tr3, and a resistor R31. A bias current described later is provided to the base of the transistor Tr3 via the resistor R31. The emitter of the transistor Tr3 is connected to a reference potential. The signal amplified by the amplifier PA3 is output from the collector of the transistor Tr3.

[0062] In addition, in the present disclosure, the transistor is set as a bipolar transistor, but the present disclosure is not limited to this. Regarding the bipolar transistor, a heterojunction bipolar transistor (HBT) can be exemplified, but the present disclosure is not limited to this. The transistor may also be, for example, a field effect transistor (FET). In this case, it is sufficient to reread the collector, base, and emitter as the drain, gate, and source, respectively. The transistor may also be a multi-finger transistor in which a plurality of unit transistors (also called "fingers") are electrically connected in parallel. The so-called unit transistor refers to the minimum structure that constitutes a transistor.

[0063] The power amplifier 100 includes an input terminal Pin, an output terminal Pout, power supply terminals VC1, VC2 and Vbat, and bias input terminals IB1 and IB2. A high-frequency signal RFin is input to the input terminal Pin, and a high-frequency signal RFout is output from the output terminal Pout.

[0064] The power amplifier 100 includes choke coils L1, L2, and L3. One end of each of the choke coils L1, L2, and L3 is connected to a power supply VCC. The other end of the choke coil L1 is connected to a power supply terminal VC1. The other end of the choke coil L2 is connected to a power supply terminal VC2. The other end of the choke coil L3 is connected to an output terminal Pout.

[0065] The power supply terminal VC1 is connected to the power supply VCC via the choke coil L1. The current flowing from the power supply VCC to the collector of the transistor Tr1 of the amplifier PA1 is set to the current Icc1. The power supply terminal VC2 is connected to the power supply VCC via the choke coil L2. The current flowing from the power supply VCC to the collector of the transistor Tr2 of the amplifier PA2 is set to the current Icc2. The output terminal Pout is connected to the power supply VCC via the choke coil L3.

[0066] In addition, the power amplifier 100 includes a bias circuit B11 provided for the amplifier PA1, a bias circuit B12 provided for the amplifier PA2, and a bias circuit B13 provided for the amplifier PA3. The bias circuit B11 is equivalent to the first bias circuit of the present disclosure. The bias circuit B12 is equivalent to the second bias circuit of the present disclosure.

[0067] The bias circuit B11 includes a transistor TrB1, a resistor RB1, transistors TrD11 and TrD12, and a capacitor CB1. One end of the resistor RB1 is connected to the base of the transistor TrB1, and the other end is connected to the bias input terminal IB1. The transistors TrD11 and TrD12 connect their bases and collectors, respectively, and thus each operates as a diode. One end of the capacitor CB1 is connected to the base of the transistor TrB1, and the other end is connected to a reference potential.

[0068] The bias circuit B12 includes a transistor TrB2, a resistor RB2, transistors TrD21 and TrD22, and a capacitor CB2. One end of the resistor RB2 is connected to the base of the transistor TrB2, and the other end is connected to the bias input terminal IB1. The transistors TrD21 and TrD22 connect their bases and collectors, respectively, and thus each operates as a diode. One end of the capacitor CB2 is connected to the base of the transistor TrB2, and the other end is connected to the reference potential.

[0069] The bias circuit B13 includes a transistor TrB3, a resistor RB3, transistors TrD31 and TrD32, and a capacitor CB3. One end of the resistor RB3 is connected to the base of the transistor TrB3, and the other end is connected to the bias input terminal IB2. The transistors TrD31 and TrD32 connect their bases and collectors, respectively, and thus each operates as a diode. One end of the capacitor CB3 is connected to the base of the transistor TrB3, and the other end is connected to the reference potential.

[0070] Furthermore, a capacitor Cb is connected between the power supply terminal Vbat and the reference potential of each of the bias circuits B11 , B12 , and B13 .

[0071] Here, the power amplifier 100 has a feedback circuit FB for adjusting the gain. The feedback circuit FB is connected between the amplifier PA1 and the amplifier PA2. One end of the feedback circuit FB is connected to the collector of the transistor Tr1 of the amplifier PA1. The other end of the feedback circuit FB is connected to the collector of the transistor Tr2 of the amplifier PA2. The feedback circuit FB of this example is a resistor Rfb that connects the collector of the transistor Tr1 and the collector of the transistor Tr2. The gain of the amplifier PA2 can be adjusted by the feedback circuit FB.

[0072] (Operation of Comparative Example)

[0073] The amplifier PA1 amplifies the high-frequency signal RFin, which is an input signal input to the input terminal Pin of the power amplifier 100. The output signal of the amplifier PA1 is input to the amplifier PA2. The amplifier PA2 amplifies the output signal of the amplifier PA1. The output signal of the amplifier PA2 is input to the amplifier PA3. The amplifier PA3 amplifies the output signal of the amplifier PA2 and outputs it from the output terminal Pout as a high-frequency signal RFout.

[0074] (Power Amplifier According to First Embodiment)

[0075] (structure)

[0076] Figure 2 1 is a diagram showing a power amplifier 100a according to a first embodiment of the present disclosure. Figure 2 The power amplifier 100a according to the first embodiment has the following structure, that is, in reference to Figure 1 In the power amplifier 100 of the comparative example described above, the voltage detection circuit 10 is provided in place of the feedback circuit FB, and the level shift circuit 20 and the protection circuit 30 are added.

[0077] Voltage detection circuit 10 instead Figure 1 The voltage detection circuit 10 is provided for the feedback circuit FB in the amplifier part PA1 and connected between the amplifier part PA2. One end of the voltage detection circuit 10 is connected to the collector of the transistor Tr1 of the amplifier part PA1. The other end of the voltage detection circuit 10 is connected to the collector of the transistor Tr2 of the amplifier part PA2. Figure 2 The voltage detection circuit 10 in the embodiment has a structure in which a resistor R1 as a first resistor and a resistor R2 as a second resistor are connected in series. A detection voltage Vdet as a DC voltage can be obtained from the connection point of the resistor R1 and the resistor R2. The resistor R1 and the resistor R2 connected in series are equivalent to the impedance element disclosed in the present invention. By using the resistor R1 and the resistor R2 as impedance elements, a DC voltage can be output. The structure and modified examples of the voltage detection circuit 10 will be further described later.

[0078] The level shift circuit 20 includes n (n is a natural number, the same below) transistors Tr11, Tr12, ..., and Tr1n. These n transistors connect the base and the collector respectively, so that they act as diodes respectively. Therefore, the voltage drop caused by the pn junction becomes n times, and the voltage level decreases according to the number of transistors connected. In other words, the level shift circuit 20 can transform the level of the DC voltage output from the voltage detection circuit 10. The structure and modification of the level shift circuit 20 will be further described later. Hereinafter, a circuit including one or more diodes such as a transistor that acts as a diode is referred to as a diode circuit.

[0079] The protection circuit 30 includes a transistor Tr21. The transistor Tr21 is equivalent to the third transistor of the present disclosure. When the transistor Tr21 is turned on, a current Idet flows. Since the current Idet flows, current can be drawn from the bias circuits B11 and B12, thereby reducing the bias current. The structure and modified examples of the protection circuit 30 will be further described later.

[0080] (action)

[0081] The transistor Tr2 of the amplifier PA2 has an emitter grounded. Therefore, the phase difference between the signal of the collector of the transistor Tr1 and the signal of the collector of the transistor Tr2 is about 180 degrees. By synthesizing the two signals with a phase difference of about 180 degrees in the voltage detection circuit 10, a detection voltage Vdet as a DC voltage can be obtained.

[0082] Figure 3 1 is a diagram showing an operation example of the voltage detection circuit 10. Figure 3 In the figure, the horizontal axis shows the passage of time, and the vertical axis shows the voltage value. Figure 3 In the embodiment, the phase difference between the voltage V1 appearing at the collector of the transistor Tr1 of the amplifier PA1 and the voltage V2 appearing at the collector of the transistor Tr2 of the amplifier PA2 is about 180°. Therefore, the voltage detection circuit 10 outputs the detection voltage Vdet by synthesizing the voltage V1 and the voltage V2. According to the detection voltage Vdet, the transistor Tr21 of the protection circuit 30 is operated, thereby flowing the current Idet, and the current can be drawn from the bias circuits B11 and B12, so that the bias current is reduced. That is, when the transistor Tr21 as the third transistor is turned on, the bias current supplied from the bias circuit B11 to the transistor Tr1 and the bias current supplied from the bias circuit B12 to the transistor Tr2 are reduced.

[0083] In the power amplifier 100a, choke coils L1 and L2 are connected between the line of the power supply VCC and the collectors of the transistors Tr1 and Tr2 of the amplifier units PA1 and PA2. Although the signal of the line of the power supply VCC is direct current, the amplitude of a high-frequency signal appears at the collectors of the transistors Tr1 and Tr2. If a DC voltage is to be obtained from the line of the power supply VCC in order to derive the DC voltage, it becomes necessary to add wiring and electrode pads for supplying power to the transistors, which is not preferred. Therefore, as described above, the values ​​of the resistors R1 and R2 connected between the two voltages V1 and V2 are set to offset the high-frequency amplitude that appears at their connection point. In this way, the two voltages V1 and V2 whose amplitudes differ in phase by approximately 180° are synthesized, as shown in FIG. Figure 3 As shown, a substantially direct current detection voltage Vdet can be derived.

[0084] In addition, until the voltage level of the input high-frequency signal RFin becomes below a certain given value, Figure 3 If the voltage level of the high-frequency signal RFin exceeds a certain given value, the waveforms of the voltages V1 and V2 are distorted. Figure 4 : is a diagram showing an example of a state where the waveform is distorted. Figure 4 As shown in FIG. 1 , if the amplitudes of the voltages V1 and V2 increase, the waveforms are distorted. At this time, a high-frequency amplitude appears in the detection voltage Vdet at the connection point between the resistors R1 and R2.

[0085] That is, if the amplitude of the high frequency exceeds a given amplitude, the amplitude of the high frequency that is not completely offset appears, and the detection voltage Vdet rises according to the amplitude. Therefore, if the base voltage of the transistor Tr21 exceeds the threshold value, the transistor Tr21 becomes conductive, and if the base voltage of the transistor Tr21 further rises, a part of the bias current continues to be drawn from the bias circuits B11 and B12 more strongly than when the detection voltage Vdet is only a DC voltage. Therefore, even if the voltage of the detection voltage Vdet itself is within the voltage range of normal use, it is possible to reliably and strongly prevent the breakdown of the transistor caused by the excessive amplitude of the high frequency.

[0086] Figure 5 2 is a diagram showing the relationship between the detection voltage Vdet output from the voltage detection circuit 10, the current Idet extracted as the extraction current by the protection circuit 30, and the collector current of each transistor. Figure 5 In FIG. 1 , the horizontal axis shows the voltage value of the power supply VCC, and the vertical axis shows the voltage value or the current value.

[0087] like Figure 5 As shown in FIG. 1 , if the detection voltage Vdet at the connection point of the resistor R1 and the resistor R2 increases, the base voltage of the transistor Tr21 of the protection circuit 30 increases. If the base voltage of the transistor Tr21 increases and exceeds a certain value, the transistor Tr21 becomes conductive. As a result, the current Idet as the extraction current increases. Since the current Idet as the extraction current increases, a part of the current of the bias circuits B11 and B12 can be extracted, and the bias current can be reduced. Therefore, the collector current Icc1 of the transistor Tr1 of the amplifier PA1 and the collector current Icc2 of the transistor Tr2 of the amplifier PA2 decrease.

[0088] Figure 6 : is a diagram showing the relationship between the voltage level of the input high-frequency signal RFin and the collector currents Icc1 and Icc2. Figure 6 In FIG. 1 , the horizontal axis shows the voltage value of the power supply VCC, and the vertical axis shows the current value. Figure 6The curve PH in FIG. 1 shows a case where the voltage level of the high-frequency signal RFin is high, and the curve PL shows a case where the voltage level of the high-frequency signal RFin is low. Figure 6 As shown, it can be seen that when the voltage level of the high-frequency signal RFin is high, the collector currents Icc1 and Icc2 decrease compared to when the voltage level of the high-frequency signal RFin is low.

[0089] (Example of voltage detection circuit)

[0090] Figure 7 It is shown for Figure 2 FIG. 1 is a diagram of a voltage detection circuit 10 of a power amplifier 100 a shown in FIG. Figure 7 The voltage detection circuit 10 shown has a resistor R1 and a resistor R2 connected in series. The resistor R1 is equivalent to the first resistor of the present disclosure. The resistor R2 is equivalent to the second resistor of the present disclosure. One end of the resistor R1 is connected to the collector of the transistor Tr1 of the amplifier PA1. The voltage V1 of the power supply terminal VC1 is applied to one end of the resistor R1. One end of the resistor R2 is connected to the collector of the transistor Tr2 of the amplifier PA2. The voltage V2 of the power supply terminal VC2 is applied to one end of the resistor R2. The detection voltage Vdet is obtained from the connection point of the other end of the resistor R1 and the other end of the resistor R2. The phase of the signal output from the collector of the amplifier PA1 and the signal output from the collector of the amplifier PA2 differs by about 180°. Therefore, by synthesizing these two signals in the voltage detection circuit 10, the amplitude of the two signals can be offset, and the detection voltage Vdet as a DC voltage can be obtained. The resistance values ​​of the resistors R1 and R2 are selected so that the high-frequency amplitude does not appear in the detection voltage Vdet at the connection point of the resistors R1 and R2.

[0091] Figures 8 to 10 1 is a diagram showing a modified example of the voltage detection circuit 10 . Figure 8 The voltage detection circuit 10a shown in FIG. Figure 7 The voltage detection circuit 10 shown in the figure has a structure in which one end of the resistor R2 is connected to the capacitor C1. Therefore, the resistor R1, the resistor R2, and the capacitor C1 are connected in series. The capacitor C1 is provided to block direct current. The capacitor C1 is equivalent to the first capacitor of the present disclosure. Figure 8 In the voltage detection circuit 10 a shown in the figure, the resistance values ​​of the resistors R1 and R2 and the capacitance value of the capacitor C1 are selected so that high-frequency amplitude does not appear in the detection voltage Vdet.

[0092] Fig. 9 The voltage detection circuit 10b shown in FIG. Figure 7The voltage detection circuit 10 shown in the figure has a structure in which one end of the resistor R1 is connected to the capacitor C2. Therefore, the capacitor C2, the resistor R1, and the resistor R2 are connected in series. The capacitor C2 is provided to block direct current. The capacitor C2 is equivalent to the first capacitor of the present disclosure. Fig. 9 In the voltage detection circuit 10 b shown, the resistance values ​​of the resistors R1 and R2 and the capacitance value of the capacitor C2 are selected so that high-frequency amplitude does not appear in the detection voltage Vdet.

[0093] Fig.10 The voltage detection circuit 10c shown in FIG. Figure 7 The voltage detection circuit 10 shown in the figure has a structure in which a resistor R3 and a capacitor C3 are added. The resistor R3 is equivalent to the third resistor of the present disclosure. The capacitor C3 is connected in series with the resistor R3. The capacitor C3 is equivalent to the second capacitor of the present disclosure. The capacitor C3 is provided to block direct current. The resistor R3 and the capacitor C3 are connected in parallel with the resistor R1 and the resistor R2. Fig.10 In the voltage detection circuit 10c shown, the resistance values ​​of the resistors R1, R2, and R3 and the capacitance value of the capacitor C3 are selected so that high-frequency amplitude does not appear in the detection voltage Vdet.

[0094] (Example of level shift circuit and protection circuit)

[0095] Fig.11 It is shown for Figure 2 FIG. 2 is a diagram showing a first example of a power amplifier 100 a , a level shift circuit 20 , and a protection circuit 30 . Fig.12 It is shown Fig.11 The waveform diagrams of the operations of the level shift circuit 20 and the protection circuit 30 are shown.

[0096] As described above, the level shift circuit 20 includes n transistors Tr11, Tr12, ..., and Tr1n. The detection voltage Vdet output from the voltage detection circuit 10 is applied to the collector and base of the transistor Tr11. The detection voltage Vdet is applied to the base of the transistor Tr21 of the protection circuit 30 after the voltage level is converted by the level shift circuit 20. If the transistor Tr21 is turned on, Fig.12As shown in the curve S1 in FIG. 1 , the current Idet flows. As the current Idet flows, the power supply voltage VB for the bias circuits B11 and B12 decreases. That is, the current Idet is a current drawn relative to the power supply voltage VB. The protection circuit 30 reduces the base bias current supplied to the transistors Tr1 and Tr2 based on the voltage whose level is converted by the level shift circuit 20. That is, when the transistor Tr21 as the third transistor is turned on, the bias current supplied from the bias circuit B11 to the transistor Tr1 and the bias current supplied from the bias circuit B12 to the transistor Tr2 are reduced.

[0097] exist Fig.12 In FIG. 3 , the horizontal axis shows the detection voltage Vdet, and the vertical axis shows the current Idet. When the voltage applied to the base of the transistor Tr21 of the protection circuit 30 exceeds a given threshold, the transistor Tr21 becomes conductive. When the transistor Tr21 becomes conductive, the current Idet flows, and when the detection voltage Vdet increases, the current Idet as the extraction current increases.

[0098] Fig.13 It is a diagram showing a second example of the level shift circuit and the protection circuit. Fig.13 The level shift circuit 20a shown is in Fig.11 The level shift circuit 20 shown in the figure has a structure in which a resistor R4 is added. One end of the resistor R4 is connected to the emitter of the transistor Tr1n. The other end of the resistor R4 is connected to the reference voltage. Therefore, the detection voltage Vdet is divided by the level shift circuit including n transistors Tr11, Tr12, ..., and Tr1n and the resistor R4. The voltage divided by the resistor is applied to the base of the transistor Tr21 of the protection circuit 30. In addition, the resistor R4 is equivalent to the fourth resistor of the present disclosure.

[0099] Fig.14 It is shown Fig.13 The waveform diagram of the operation of the level shift circuit 20a and the protection circuit 30 shown in FIG. As described above, the voltage divided by resistance is applied to the base of the transistor Tr21 of the protection circuit 30. Fig.14 The dashed curve S1 is shown in Fig.12 Compared with the current Idet of FIG. 1 , in this example, as shown by the curve S2, the current Idet rises slowly. Fig.13 The level shift circuit 20 a and the protection circuit 30 shown can suppress a sharp rise in the current Idet as the extraction current by adding the resistor R4 .

[0100] Fig.15 FIG. 1 is a diagram showing a third example of a level shift circuit and a protection circuit. Fig.11In the protection circuit 30, when the power supply voltage VB drops to, for example, 0 V, the transistor Tr21 is reversely turned on, and a current flows from the base to the collector of the transistor Tr21. That is, it is also conceivable that the current Idet flows in the reverse direction.

[0101] In order to prevent the current Idet from flowing in the reverse direction, that is, to prevent the current from flowing backward, Fig.15 A transistor Tr22 is added to the protection circuit 30a. The base and collector of the transistor Tr22 are connected, so it acts as a diode. Therefore, it is possible to prevent the current Idet from flowing in the reverse direction. The transistor Tr22 is equivalent to the backflow prevention element of the present disclosure.

[0102] Fig.16 It is shown Fig.15 The waveform diagram of the operation of the level shift circuit 20 and the protection circuit 30a shown in FIG. Fig.16 As shown by the dashed curve S3 in FIG. 1 , the current Idet flows in the reverse direction. Fig.15 As shown in FIG. 1 , a transistor Tr22 is added which acts as a diode, thereby Fig.16 As shown by the solid line S4 in FIG. 1 , even if the detection voltage Vdet increases, current does not flow in the reverse direction.

[0103] Fig.17 1 is a diagram showing a fourth example of a level shift circuit and a protection circuit. Fig.17 In Fig.11 The level shift circuit 20 is a level shift circuit 20b in which a transistor Tr24 is added. The transistor Tr24 is provided between the transistor Tr1n and the transistor Tr21. The transistor Tr24 is turned on by the voltage whose level is converted by the level shift circuit. The transistor Tr24 is equivalent to the fourth transistor of the present disclosure.

[0104] Regarding the detection voltage Vdet, sometimes the resistor R1 and the resistor R2 (see Figure 2 ) to the level shift circuit 20. In this case, it is also conceivable that the base voltage for turning on the transistor Tr21 of the protection circuit 30 is insufficient. Therefore, a transistor Tr24 is added that is Darlington-connected to the transistor Tr21. The collector of the transistor Tr24 is preliminarily connected to the power supply terminal VC1 or VC2, and the power supply VCC is applied.

[0105] Fig.18 It is shown Fig.17 The waveform diagram of the operation of the level shift circuit 20 b and the protection circuit 30 is shown. Fig.18 The dashed curve S1 in the figure is equivalent to Fig.12By adding transistor Tr24, the current Idet in Fig.18 As shown by the solid line curve S5 in FIG. 2 , the current Idet can be increased sharply. Therefore, by adding the transistor Tr24, the speed of extracting the current can be increased.

[0106] Fig.19 FIG. 5 is a diagram showing a fifth example of a level shift circuit and a protection circuit. Fig.19 In the case of resistors R1 and R2 (refer to Figure 2 A resistor R5 is inserted between the connection point of the resistor R5 and the diode circuit. The operating point of the transistor Tr21 of the protection circuit 30 can be adjusted by the product of the resistance value of the resistor R5 and the current Iref flowing through the resistor R5, so that the entire curve of the current Idet is shifted.

[0107] Fig. 20 It is shown Fig.19 The waveform diagram of the operation of the level shift circuit 20c and the protection circuit 30 is shown. Fig. 20 The dashed curve S1 in the figure is equivalent to Fig.12 By adding resistor R5, the current Idet in Fig. 20 As shown by the solid line curve S6 in FIG. 8 , the entire curve of the current Idet can be shifted.

[0108] Fig.21 1 is a diagram showing a sixth example of a level shift circuit and a protection circuit. Fig.21 In the Fig.15 The protection circuit 30a is a protection circuit 30b in which a transistor Tr23 is added. The transistor Tr23 is provided on the reference potential side of the transistor Tr21. The transistor Tr23 corresponds to the fifth transistor of the present disclosure.

[0109] The control current Icont is applied to the base of the transistor Tr23. The control current Icont is equivalent to the given control signal of the present disclosure. As described later, by applying the control current Icont according to the operation mode of the power amplifier, the operation of extracting the current Idet can be executed or stopped.

[0110] Fig. 22 It is shown Fig.21 The waveform diagram of the operation of the level shift circuit 20 and the protection circuit 30b is shown. Fig. 22 The dashed curve S1 in the figure is equivalent to Fig.12 By turning on the transistor Tr23, the current Idet is extracted, so that Fig. 22As shown by the dotted line in FIG. 1 , the current Idet increases in accordance with the increase in the detection voltage Vdet. On the other hand, by turning off the transistor Tr23, the operation of extracting the current Idet is stopped, so that Fig. 22 As shown by the solid line S7 in FIG. 1 , the current Idet does not increase even if the detection voltage Vdet increases. In this way, the operation of extracting the current Idet can be executed or stopped by the control current Icont applied according to the operation mode of the power amplifier.

[0111] In addition, it is possible to refer to Figures 11 to 22 The structures of the level shift circuit and the protection circuit described above are combined. Fig.23 FIG. 1 is a diagram showing a first example of a combination of a level shift circuit and a protection circuit. Fig.23 The first example shown is a combination of reference Fig.13 The level shift circuit 20a described above and the reference Fig.21 An example of the protection circuit 30b is described. Fig.23 The structure of the first example shown can prevent the current Idet from flowing in the reverse direction, and can execute or stop the operation of extracting the current Idet.

[0112] Fig.24 FIG. 2 is a diagram showing a second example of a combination of a level shift circuit and a protection circuit. Fig.24 The second example shown is in reference to Fig.13 The level shift circuit 20a described above is added with reference to Fig.17 The transistor Tr24 described above is further combined with the reference Fig.21 An example of the protection circuit 30b is described. Fig.24 The structure of the second example shown can prevent the current Idet from flowing in the reverse direction, and can execute or stop the operation of extracting the current Idet, thereby increasing the speed of extracting the current.

[0113] (Effect)

[0114] The power amplifier 100a of the first embodiment can prevent breakdown of transistors included in the amplification section. Furthermore, when the detection voltage Vdet exceeds a predetermined voltage, current extraction continues, so the protection state continues, and breakdown protection can be performed more reliably.

[0115] <Second Embodiment>

[0116] (structure)

[0117] Fig.25 1 is a diagram showing a power amplifier 100b according to a second embodiment of the present disclosure. Fig.25The power amplifier 100b according to the second embodiment is configured such that, in the power amplifier 100a according to the first embodiment, a reference Fig.13 The level shift circuit 20a described above and the reference Fig.21 The protection circuit 30b is described.

[0118] exist Fig.25 In the embodiment, the power amplifier 100b according to the second embodiment includes amplifiers PA1, PA2, and PA3 and bias circuits B11, B12, and B13 corresponding thereto, similarly to the power amplifier 100a according to the first embodiment. The bias circuits B11, B12, and B13 have the same structure as the bias circuits B11, B12, and B13 of the power amplifier 100a. However, the base of the transistor TrD32 of the bias circuit B13 is connected to the base of the transistor Tr23 of the protection circuit 30b. Thus, a current mirror circuit is formed by the transistor TrD32 and the transistor Tr23.

[0119] (action)

[0120] When the control voltage applied to the bias input terminal IB2 exceeds a given value, the transistor Tr23 is turned on and the protection circuit 30b is activated. Thus, as in the power amplifier 100a according to the first embodiment, a current is drawn according to the detection voltage Vdet to protect each transistor Tr1 and Tr2. In addition, when the voltage applied to the bias input terminal IB2 is less than a given value, the transistor Tr23 is turned off and the protection circuit 30b is not activated.

[0121] (Effect)

[0122] The state of protecting each transistor Tr1 , Tr2 can be set to on or off according to the control voltage applied to the bias input terminal IB2 .

[0123] <Third Embodiment>

[0124] (structure)

[0125] Fig.26 1 is a diagram showing a power amplifier 100c according to a third embodiment of the present disclosure. The power amplifier 100c according to the third embodiment can handle amplification operations of two different wireless communication methods. The power amplifier 100c, for example, implements an amplification operation corresponding to a wireless communication method based on 2G (2nd Generation) (hereinafter referred to as 2G mode) and an amplification operation corresponding to a wireless communication method based on 5G (5th Generation) (hereinafter referred to as 5G mode).

[0126] exist Fig.26 The power amplifier 100c according to the third embodiment includes an amplifier PA1 at the first stage and amplifiers PA21 and PA22 at the second stage. The output of the amplifier PA1 is input to the amplifiers PA21 and PA22. The amplifiers PA21 and PA22 are a pair of differential amplifiers.

[0127] A capacitor Cin, inductors L12 and L13 connected in series, and a diode unit D11 are provided between the input terminal Pin and the amplifier unit PA1.

[0128] The amplifier PA1 includes a multi-finger transistor Tr1a, a capacitor C11a connected to the base of the transistor Tr1a, and a resistor R11a. The transistor Tr1a has an emitter grounded to form an amplifier circuit.

[0129] A diode section D12, a capacitor C12, and a balanced-unbalanced transformer T are provided between the amplifier section PA1 and the amplifier sections PA21 and PA22. The balanced-unbalanced transformer T is implemented by a transformer including a primary winding L11 and a secondary winding L21. The primary winding L11 and the secondary winding L21 are electromagnetically coupled to each other. One end of the primary winding L11 of the balanced-unbalanced transformer T is connected to the collector of the amplifier section PA1. The other end of the primary winding L11 is connected to the terminal T3. The primary winding L11 is equivalent to an impedance element of the voltage detection circuit of the present disclosure. By using the primary winding L11 as an impedance element, a DC voltage can be output.

[0130] The amplified output of the amplifier PA21 is applied to one end of the secondary winding L21 of the balun transformer T. The amplifier PA22 is connected to the other end of the secondary winding L21. A capacitor C210 is provided between both ends of the secondary winding L21.

[0131] The other end of the primary winding L11 of the balun transformer T is connected to the level shift circuit 20. The level shift circuit 20 includes transistors Tr11, Tr12, and Tr13 that operate as diodes. The level shift circuit 20 is connected to the protection circuit 30b. The structure of the protection circuit 30b is as shown in FIG. Fig.21 As described.

[0132] The amplifier PA21 includes a multi-finger transistor Tr211, a capacitor C211 connected to the base of the transistor Tr211, and resistors R211 and R212. The transistor Tr211 has an emitter grounded to form an amplifier circuit. A capacitor C212 is connected between one end of the capacitor C211 and one end of the resistor R212.

[0133] The amplifier PA22 includes a multi-finger transistor Tr221, a capacitor C221 connected to the base of the transistor Tr221, and resistors R221 and R222. The transistor Tr221 has an emitter grounded to form an amplifier circuit. A capacitor C222 is connected between one end of the capacitor C221 and one end of the resistor R222.

[0134] A diode D21 is provided between the amplifier PA21 and the output terminal Pout1. A diode D22 is provided between the amplifier PA22 and the output terminal Pout2. An inductor L22 and capacitors C31 and C32 connected in series are provided between the amplifiers PA21 and PA22 and the output terminals Pout1 and Pout2. One end of the inductor L22 is connected to the connection point of the capacitors C31 and C32. The other end of the inductor L22 is connected to the emitter of the transistor Tr211.

[0135] A bias circuit B21 is provided corresponding to the amplifier PA1. The bias circuit B21 includes a multi-finger transistor TrB1a, a transistor TrB1b, a capacitor CB11 connected between the base of the transistor TrB1a and a reference potential, a capacitor CB12 connected between the collector and the base of the transistor TrB1b, a resistor RB11, and a resistor RB12. When the transistor TrB1a is turned on, a bias current is supplied to the amplifier PA1. In addition, a capacitor Cb and a diode Db are connected between the power supply terminal Vbat and the reference potential of each bias circuit B21 and B22.

[0136] A bias circuit B22 is provided corresponding to the amplifiers PA21 and PA22. The bias circuit B22 includes a multi-finger transistor TrB22, a transistor TrB21, a capacitor CB21 connected between the bases of the transistors TrB21 and TrB22 and a reference potential, transistors TrD21 and TrD22 that operate as diodes, and a resistor RB22. When the transistor TrB21 is turned on, a bias current is supplied to the amplifier PA21. When the transistor TrB22 is turned on, a bias current is supplied to the amplifier PA22.

[0137] Terminals T1, T2, T5, T21, and T22 are connected to a reference potential. A power supply voltage is applied to terminal T3. By applying the power supply voltage to terminal T3, a DC voltage that appears in primary winding L11 is input to level shift circuit 20 as detection voltage Vdet. Control current Icont is applied to terminal T4. By setting transistor Tr23 of protection circuit 30b to an on state or an off state according to control current Icont, an action of extracting current of protection circuit 30b (hereinafter referred to as current extraction action) can be set to an execution state or a stop state.

[0138] (action)

[0139] In the power amplifier 100c, the output power of the wireless communication based on the 2G mode and the wireless communication based on the 5G mode is different. Specifically, in the case of the 2G mode and the case of the 5G mode, the amplitude of the high-frequency signal RFout1 output from the collector of the transistor Tr211 of the amplifier PA21 and the amplitude of the high-frequency signal RFout2 output from the collector of the transistor Tr221 of the amplifier PA22 are different.

[0140] In addition, the power supply voltage applied to the terminal T3 is different in the case of the 2G mode and the case of the 5G mode. In the case of the 2G mode, the current extraction action is set to the execution state by providing the control current Icont. On the other hand, in the case of the 5G mode, if the power supply voltage provided to the terminal T3 is high, the detection voltage Vdet becomes large, and the current extraction action will become the on state. Therefore, in the case of the 5G mode, the control current Icont is set to, for example, 0 amperes. As a result, the transistor Tr23 becomes the off state, so that the current extraction action can be set to the stop state and prevent the current extraction action from becoming the execution state.

[0141] (Effect)

[0142] In the case of the 2G mode where the breakdown test conditions are strict, a given control current Icont that is not 0 amperes is applied to set the protection circuit 30b to an operating state. In this way, the current Idet flows, the current is extracted, and the output power level of the amplifier PA1 is reduced, thereby reducing the power transmitted from the primary winding L11 side of the balanced-unbalanced transformer T to the secondary winding L21 side. As a result, the breakdown of the transistor Tr211 of the amplifier PA21 and the transistor Tr221 of the amplifier PA22 can be prevented. On the other hand, in the case of the 5G mode, by setting the control current Icont to 0 amperes, the current extraction action can be prevented from being executed.

[0143] <Example of Power Amplifier Layout>

[0144] Figure 27 to Figure 29 1 is a diagram showing an example of a layout in which the power amplifier of the present disclosure is implemented on a substrate. Figure 27 to Figure 29 The layout is schematically shown in the case where the power amplifier is implemented on a substrate.

[0145] exist Fig. 27 In the embodiment, the power amplifier 100d includes an amplifier PA1, an amplifier PA2, an amplifier PA3, a voltage detection circuit 10, a level shift circuit 20, a protection circuit 30, and a power supply wiring for supplying a power supply voltage applied to power supply terminals VC1 and VC2. In addition, the power supply wiring for supplying a power supply voltage applied to power supply terminals VC1 and VC2 is respectively marked with the same reference numerals "VC1" and "VC2".

[0146] The amplifier PA1 is a first-stage (i.e., primary) amplifier. The amplifier PA2 is a second-stage (i.e., intermediate) amplifier. The amplifier PA3 is a third-stage (i.e., final) amplifier. The final-stage amplifier PA3 generates more heat than the amplifiers PA1 and PA2. Therefore, in the power amplifier 100d, Fig. 27 As shown in FIG. 1 , the level shift circuit 20 is provided near the third amplifier PA3. By laying out the components in this way, it is expected that the level shift circuit 20 and the third amplifier PA3 are thermally coupled. By thermally coupling the level shift circuit 20 and the third amplifier PA3, the threshold of the transistor in the level shift circuit 20 can be lowered when the input power level becomes high.

[0147] exist Fig.28 In the power amplifier 100e, with reference Fig. 27 Unlike the power amplifier 100d described above, the protection circuit 30 is provided near the third amplifier PA3. By laying out the components in this way, it is expected that the protection circuit 30 and the third amplifier PA3 are thermally coupled. Since the protection circuit 30 and the third amplifier PA3 are thermally coupled, the protection circuit 30 can start operating at a lower power supply voltage than when the output power of the power amplifier 100e is low.

[0148] exist Fig.29In the power amplifier 100f, the level shift circuit 20 and the protection circuit 30 are provided near the third amplifier PA3. By laying out the components in this way, it is expected that the level shift circuit 20 and the protection circuit 30 are thermally coupled with the third amplifier PA3. By thermally coupling the level shift circuit 20 and the protection circuit 30 with the third amplifier PA3, the threshold of the transistor in the level shift circuit 20 can be lowered, and the protection circuit 30 can start operating at a lower power supply voltage than when the output power of the power amplifier 100f is low.

Claims

1. A power amplifier having a multi-stage amplifier section, wherein the amplifier section includes a transistor with an emitter grounded, wherein: The power amplifier comprises: The first amplifier has a first transistor for amplifying an input high frequency signal; a second amplifier having a second transistor for amplifying the output of the first amplifier; a voltage detection circuit including at least an impedance element and arranged between the first transistor and the second transistor; as well as The protection circuit reduces a base bias current supplied to at least one of the first transistor and the second transistor based on an output of the voltage detection circuit.

2. The power amplifier according to claim 1, wherein: In the voltage detection circuit, as the impedance element, there is provided: a first resistor; and a second resistor connected to the first resistor, The output of the voltage detection circuit is obtained from a connection point between the first resistor and the second resistor.

3. The power amplifier according to claim 2, wherein: The first resistor is electrically connected to the collector of the first transistor. The second resistor is electrically connected to the collector of the second transistor. The output of the voltage detection circuit is obtained from a connection point between the first resistor and the second resistor.

4. The power amplifier according to claim 3, wherein: As the impedance element, the device further comprises: The first capacitor is connected in series with either the first resistor or the second resistor.

5. The power amplifier according to claim 2, wherein: The first resistor is electrically connected to the collector of the first transistor. The second resistor is electrically connected to the collector of the second transistor. As the impedance element, the device further comprises: a third resistor electrically connected to the collector of the first transistor; and a second capacitor connected in series with the third resistor, The third resistor and the second capacitor are connected in parallel with the first resistor and the second resistor.

6. The power amplifier according to claim 1 or claim 2, wherein: Also includes: a first bias circuit for supplying a bias current to the first transistor; and a second bias circuit for supplying a bias current to the second transistor; The protection circuit includes a third transistor that becomes conductive based on the output of the voltage detection circuit. When the third transistor becomes conductive, a bias current supplied from the first bias circuit to the first transistor and a bias current supplied from the second bias circuit to the second transistor are reduced.

7. The power amplifier according to claim 6, wherein: Also includes: a level shift circuit for converting the level of the voltage output from the voltage detection circuit; The level shift circuit includes a diode circuit, wherein the diode circuit includes more than one diode. The protection circuit reduces bias current supplied to the first transistor and the second transistor based on the voltage whose level is converted by the level shift circuit.

8. The power amplifier according to claim 7, wherein: The level shift circuit further comprises: a fourth resistor connected in series with the diode circuit, The third transistor is turned on according to the voltage divided by the diode circuit and the fourth resistor.

9. The power amplifier according to claim 8, wherein: The level shift circuit further comprises: The fourth transistor is turned on in response to the voltage whose level is changed by the diode circuit. When the fourth transistor is in an on state, a predetermined power supply voltage is input to the base of the third transistor.

10. The power amplifier according to claim 7, wherein: Also includes: The backflow prevention element prevents a current from flowing back from the third transistor to the first bias circuit and the second bias circuit.

11. The power amplifier according to claim 7, wherein: Also includes: The fifth transistor is turned on or off according to a given control signal. When the fifth transistor is in an on state, the third transistor is turned on to reduce the bias current supplied to the first transistor and the second transistor.

12. The power amplifier according to claim 7, wherein: The level shift circuit further comprises: A fifth resistor is connected in series between the voltage detection circuit and the diode circuit of the level shift circuit.

13. The power amplifier according to claim 1, wherein: Also includes: A balun transformer has a primary winding and a secondary winding. The primary winding is electrically connected to the first amplifier. The secondary winding is electrically connected to the second amplifier. The voltage detection circuit uses the primary winding as the impedance element and obtains the output using the primary winding.

14. The power amplifier according to claim 13, wherein: The second amplifier is a pair of differential amplifiers electrically connected to the secondary winding.

15. The power amplifier according to claim 7, wherein: Also includes: The third amplifier section operates as a power stage for amplifying the output of the second amplifier section. The first amplifier, the second amplifier, the third amplifier, the voltage detection circuit, the protection circuit, and the level shift circuit are formed on one substrate. In the substrate, at least one of the protection circuit and the level shift circuit is provided near the third amplifier.

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