Protective circuit

Abstract

This protective circuit includes: a comparison section that, when the signal level of a signal outputted from a prescribed amplifier among at least one amplifier in a power amplification circuit that includes at least one amplifier is a reference voltage or greater, outputs from an output terminal an output signal according to the difference between the signal level and the reference voltage; a DC removal unit that has one terminal electrically connected to the output terminal of the comparison unit and outputs, from another terminal, a signal obtained by removing a DC component of the output signal; and a detection unit that has an input terminal electrically connected to the other terminal of the DC removal unit, and outputs, from the output terminal, a control signal corresponding to the signal level of the signal output from the predetermined amplifier to a predetermined circuit capable of reducing the gain of the power amplification circuit.

Description

protection circuit

[0001] The present disclosure relates to protection circuits.

[0002] For example, it is known that a power amplifier circuit including a plurality of power amplifiers is provided with a protection circuit that detects saturation of the power amplifiers and protects the power amplifiers (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2008-294977

[0004] Patent Document 1 discloses a power amplifier circuit including a protection circuit that detects saturation of a power amplifier. The protection circuit described in Patent Document 1 electrically connects a detection terminal for detecting saturation of the power amplifier to the output terminal of a subsequent power amplifier. The protection circuit detects the collector voltage of the subsequent power amplifier through the detection terminal. When the detected collector voltage of the subsequent power amplifier exceeds a predetermined value, a current flows into the protection circuit from the collector of the subsequent power amplifier through the detection terminal. When a current flows from the subsequent power amplifier through the detection terminal, the protection circuit draws a current from the base and collector of the previous power amplifier through a predetermined transistor. Here, the predetermined value in the protection circuit is a voltage value at which the subsequent power amplifier operates in a safe operating area and at which the subsequent power amplifier can ensure a desired amplification gain. In other words, the protection circuit described in Patent Document 1 can prevent destruction of the power amplifier in the subsequent stage by suppressing the output of the power amplifier in the previous stage by drawing current from the base and collector of the power amplifier in the previous stage under overvoltage conditions in which the collector voltage of the power amplifier in the subsequent stage exceeds the rated voltage.

[0005] However, in the protection circuit described in Patent Document 1, the signal output from the protection circuit is input via a resistor to a predetermined transistor for suppressing the output of the power amplifier in the preceding stage. In this case, the DC component input to the predetermined transistor slows down the operation of the transistor, which may cause a delay in suppressing the output of the power amplifier in the preceding stage.

[0006] Therefore, an object of the present disclosure is to provide a protection circuit that can quickly perform suppression control of the gain of a power amplifier circuit.

[0007] A protection circuit according to one aspect of the present invention includes: a power amplifier circuit including at least one amplifier; a comparison unit that, when the signal level of a signal output from a predetermined amplifier of the at least one amplifier is equal to or higher than a reference voltage, outputs from an output terminal an output signal corresponding to the difference between the signal level and the reference voltage; a DC removal unit that has one terminal electrically connected to the output terminal of the comparison unit and outputs from the other terminal a signal obtained by removing a DC component from the output signal; and a detection unit that has an input terminal electrically connected to the other terminal of the DC removal unit and outputs from the output terminal a control signal corresponding to the signal level of the signal output from the predetermined amplifier to a predetermined circuit that can reduce the gain of the power amplifier circuit.

[0008] According to the present disclosure, it is possible to provide a protection circuit that can quickly perform suppression control of the gain of a power amplifier circuit.

[0009] 1 is a diagram showing an example of the configuration of a power amplifier circuit; FIG. 2 is a diagram showing the configuration of a power amplifier circuit according to a first modified example; FIG. 3 is a diagram showing the configuration of a power amplifier circuit according to a second modified example; FIG. 4 is a diagram showing an outline of the configuration of a protection circuit; FIG. 5 is a diagram showing an example of the configuration of a protection circuit; FIG. 6 is a diagram showing the configuration of a protection circuit according to a first modified example; FIG. 7 is a diagram showing another example of the configuration of a protection circuit according to the first modified example; FIG. 8 is a diagram showing another example of the configuration of a protection circuit according to the second modified example;

[0010] Hereinafter, each embodiment of the present disclosure will be described with reference to the drawings. Hereinafter, circuit elements with the same reference numerals will be referred to as the same circuit elements, and redundant description will be omitted.

[0011] ===Power Amplifier Circuit 1000=== The configuration of the power amplifier circuit according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of the power amplifier circuit 1000.

[0012] The power amplifier circuit 1000 is mounted on, for example, a mobile phone and is used to amplify the power of a signal to be transmitted to a base station. The power amplifier circuit 1000 can amplify the power of signals of communication standards such as 2G (second generation mobile communication system), 3G (third generation mobile communication system), 4G (fourth generation mobile communication system), 5G (fifth generation mobile communication system), LTE (Long Term Evolution)-FDD (Frequency Division Duplex), LTE-TDD (Time Division Duplex), LTE-Advanced, and LTE-Advanced Pro. Note that the communication standards of the signals amplified by the power amplifier circuit 1000 are not limited to these.

[0013] 1, the power amplifier circuit 1000 amplifies, for example, an input signal RFin input from an input terminal 1001 and outputs an output signal RFout from an output terminal 1002. The input signal RFin is a radio frequency (RF) signal, and the frequency of the input signal RFin is, for example, about several GHz.

[0014] <<Configuration>> As shown in FIG. 1 , the power amplifier circuit 1000 includes, for example, a driver stage amplifier (hereinafter referred to as a “driver stage amplifier 1100”), a final stage amplifier (hereinafter referred to as a “final stage amplifier 1200”), and a protection circuit 1300.

[0015] The driver stage amplifier 1100 is, for example, an amplifier that amplifies an input signal RFin and outputs a signal RF10. The driver stage amplifier 1100 is biased by, for example, a bias circuit 1400.

[0016] The final stage amplifier 1200 is an amplifier connected in series to the driver stage amplifier 1100. The final stage amplifier 1200 amplifies, for example, a signal RF10 and outputs a signal RF20. A signal based on the signal RF20 is output from the output terminal 1002 as an output signal RFout. The final stage amplifier 1200 is biased by, for example, a bias circuit 1500.

[0017] The protection circuit 1300 is a circuit that detects the signal level output from a predetermined amplifier among the multiple amplifiers included in the power amplifier circuit 1000. Specifically, the protection circuit 1300 is a circuit that detects the signal level of the signal RF10 output from the final stage amplifier 1200, for example. The signal level is, for example, a voltage. The protection circuit 1300 detects, for example, a signal indicating the signal level (hereinafter, referred to as a "control signal D ｃｏｎｔ "), the bias supplied from the bias circuit 1400 to the driver stage amplifier 1100 is reduced. That is, the driver stage amplifier 1100 reduces the bias supplied from the bias circuit 1400 to the driver stage amplifier 1100 in response to the control signal D ｃｏｎｔ As is larger, the gain is smaller.

[0018] In this way, the power amplifier circuit 1000 can prevent breakdowns due to voltage fluctuations by reducing the gain of the driver stage amplifier 1100 at appropriate timing, for example, when the final stage amplifier 1200 is saturated or begins to saturate.

[0019] The protection circuit 1300 is not limited to detecting the signal level of the signal output from the final stage amplifier 1200, and may be configured to detect, for example, the signal level of the signal output from the driver stage amplifier 1100. In the following, as an example, the protection circuit 1300 will be described as detecting the signal level of the signal output from the final stage amplifier 1200.

[0020] Furthermore, the protection circuit 1300 is not limited to reducing the bias supplied from the bias circuit 1400 to the driver stage amplifier 1100. For example, in the power amplifier circuit 1000, when an attenuator (not shown) is provided in series in the stage preceding the driver stage amplifier 1100, the protection circuit 1300 controls the control signal D ｃｏｎｔ may be output to the attenuator.

[0021] <<First Modification>> The configuration of a power amplifier circuit 1000a according to a first modification will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of the power amplifier circuit 1000a according to the first modification. As shown in Fig. 2, in the power amplifier circuit 1000a according to the first modification, a protection circuit 1300 ｃｏｎｔ, the bias supplied from the bias circuit 1500 to the final stage amplifier 1200 is reduced. ｃｏｎｔ As θ increases, the gain of the final stage amplifier 1200 decreases. As a result, the power amplifier circuit 1000a can prevent the final stage amplifier 1200 from being destroyed by reducing the bias of the final stage amplifier 1200 at an appropriate timing when the final stage amplifier 1200 is saturated or begins to be saturated.

[0022] <<Second Modification>> The configuration of a power amplifier circuit 1000b according to a second modification will be described with reference to Fig. 3. Fig. 3 is a diagram showing the configuration of the power amplifier circuit 1000b according to the second modification. As shown in Fig. 3, the power amplifier circuit 1000b according to the second modification includes a Doherty amplifier circuit, as compared to the power amplifier circuit 1000. Specifically, the power amplifier circuit 1000b includes, for example, a common driver stage amplifier 1110, a driver stage carrier amplifier 1120, a final stage carrier amplifier 1130, a driver stage peak amplifier 1140, a final stage peak amplifier 1150, a protection circuit 1300, a distributor 1600, and a combiner 1700.

[0023] A Doherty amplifier circuit generally comprises a driver stage carrier amplifier 1120 and a final stage carrier amplifier 1130, which operate regardless of the power level of the input signal, and a driver stage peak amplifier 1140 and a final stage peak amplifier 1150, which are connected in parallel and turn off when the power level of the input signal is low and turn on when the power level is high. In the Doherty amplifier circuit, the peak amplifier is operated when the carrier amplifier approaches saturation. This allows the Doherty amplifier circuit to have improved efficiency compared to a normal power amplifier circuit.

[0024] The carrier amplifier is biased, for example, to class A, class AB, or class B. The peak amplifier is biased, for example, to class A, class AB, class B, or class C.

[0025] The divider 1600 divides, for example, the signal RFin into a signal to be input to the carrier amplifier and a signal to be input to the peak amplifier. The divider 1600 may be, for example, a distributed constant circuit such as a coupled-line 3 dB coupler or a Wilkinson divider. The combiner 1700 combines, for example, the signal RF10 output from the carrier amplifier and passing through a phase shifter (not shown) with the signal output from the peak amplifier, and outputs the signal Pout.

[0026] In the power amplifier circuit 1000b, the protection circuit 1300 appropriately detects the saturated state of the final-stage carrier amplifier 1130, thereby reducing the bias of the bias circuits 1111, 1121, and 1131 of at least one of the common driver stage amplifier 1110, the driver stage carrier amplifier 1120, and the final-stage carrier amplifier 1130. That is, the protection circuit 1300 reduces the bias of the control signal D ｃｏｎｔ This reduces the bias of at least one of bias circuits 1111, 1121, 1131 of common driver stage amplifier 1110, driver stage carrier amplifier 1120, and final stage carrier amplifier 1130. As a result, when final stage carrier amplifier 1130 is saturated or begins to be saturated, power amplifier circuit 1000b reduces the bias of final stage carrier amplifier 1130 at appropriate timing, thereby preventing damage to final stage carrier amplifier 1130.

[0027] In this way, the power amplifier circuit 1000b prevents destruction of the final-stage carrier amplifier 1130 by adjusting the bias of the carrier amplifier of the Doherty amplifier circuit. In order to achieve highly efficient operation in the Doherty amplifier circuit, the voltage amplitude of the power supply voltage supplied to the carrier amplifier is set to be larger than that of the power supply voltage supplied to the peak amplifier. Therefore, in the Doherty amplifier circuit, the instantaneous maximum voltage of the output terminal of the carrier amplifier (the collector or drain of the transistor constituting the carrier amplifier) ​​becomes higher than the instantaneous maximum voltage of the output terminal of the peak amplifier (the collector or drain of the transistor constituting the peak amplifier), which increases the likelihood of destruction of the carrier amplifier. Therefore, the power amplifier circuit 1000b has a configuration in which the protection circuit 1300 protects the carrier amplifier, which is more likely to be destroyed.

[0028] ===Protection Circuit 1300=== Next, the configuration of the protection circuit 1300 will be specifically described. In the following, as an example, the transistor will be described as a bipolar transistor. Note that the transistor may also be a FET (Field Effect Transistor). In other words, the emitter, collector, and base of a bipolar transistor can be respectively replaced with the source, drain, and gate of an FET.

[0029] <<Outline of Protection Circuit 1300>> An outline of the configuration of the protection circuit 1300 will be described with reference to Fig. 4. Fig. 4 is a diagram showing the outline of the configuration of the protection circuit 1300. As shown in Fig. 4, the protection circuit 1300 includes, for example, an input terminal 1301, a detection terminal 1302, a comparison unit 1310, a DC removal unit 1320, and a detection unit 1330.

[0030] The input terminal 1301 is, for example, a terminal electrically connected to the output terminal of the final stage amplifier 1200 .

[0031] The detection terminal 1302 is a terminal for detecting the signal level of the output from the final stage amplifier 1200. The detection terminal 1302 is electrically connected to the bias circuit 1400 of the driver stage amplifier 1100, for example.

[0032] The comparator 1310 receives the output signal RF20 output from the output terminal of the final stage amplifier 1200 at its input terminal, and when the signal level of the output signal RF20 is equal to or higher than a reference voltage, outputs an output signal RF30 from its output terminal that corresponds to the difference between the signal level of the output signal RF20 and the reference voltage. The output terminal of the comparator 1310 is electrically connected to the DC removal unit 1320, which will be described later.

[0033] The DC removal unit 1320 removes the DC component from the output signal RF30 output from the comparison unit 1310 and outputs the output signal RF40. That is, the DC removal unit 1320 passes the high-frequency component in the output signal RF30. For example, one terminal of the DC removal unit 1320 is electrically connected to the output terminal 1310c of the comparison unit 1310, and the other terminal is electrically connected to the detection unit 1330, which will be described later.

[0034] The detector 1330 detects the output signal RF40 from which the DC component has been removed by the DC remover 1320. Here, the detector 1330 converts the output signal into a DC component and generates a control signal D ｃｏｎｔ Output.

[0035] The detection unit 1330 has, for example, an input terminal electrically connected to the other terminal of the DC removal unit 1320 and an output terminal electrically connected to the detection terminal 1302 .

[0036] In this way, when the instantaneous maximum voltage of the output signal output from the final stage amplifier 1200 approaches the voltage that will destroy the amplifier, the protection circuit 1300 outputs from the comparison unit 1310 the output signal RF30 that oscillates with the period of the output signal RF20 output from the final stage amplifier 1200. The protection circuit 1300 then removes the DC component from the output signal RF30 output from the comparison unit 1310, thereby improving the delay in the response time of the comparison unit 1310 that is caused by the DC component. Fluctuations in the bias point of the detection unit 1330 can also be suppressed.

[0037] On the other hand, the protection circuit of Patent Document 1 requires a long time to stabilize the DC component of the signal input to a predetermined transistor that suppresses the output of the power amplifier in the previous stage. In other words, the protection circuit of Patent Document 1 requires a long time until the response stabilizes because the DC component input to the transistor affects the operation of the protection circuit itself.

[0038] That is, the protection circuit 1300 has a configuration that removes the DC component of the output signal of the comparison unit 1310, so that the output signal does not affect the operation of the protection circuit 1300. As a result, the protection circuit 1300 has a significant advantage over the prior art in that it can improve the application time delay of each component.

[0039] The protection circuit 1300 may include an amplifier 1340. The amplifier 1340 is connected in series between the comparator 1310 and the DC remover 1320. In this way, the protection circuit 1300 outputs a high-frequency signal from the comparator 1310, so that amplification can be achieved with a simple configuration. The protection circuit 1300 amplifies the output signal RF30 output from the comparator 1310, thereby amplifying the control signal D ｃｏｎｔ Since the amplifier 1340 can be made larger, it is possible to sensitively monitor the saturation state of the final stage amplifier 1200. In the following, the protection circuit 1300 will be described as including an amplifier unit 1340, as an example.

[0040] <<Configuration of Protection Circuit 1300>> Next, an example of a specific configuration of the protection circuit 1300 will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of the configuration of the protection circuit 1300. As shown in Fig. 5, the protection circuit 1300 includes a comparison unit 1310, an amplification unit 1340, a DC removal unit 1320, and a detection unit 1330.

[0041] The comparison unit 1310 includes, for example, a reference potential unit D10 and a transistor Q10.

[0042] The reference potential section D10 is configured by, for example, connecting a plurality of diodes in series. The anode of the reference potential section D10 is electrically connected to the input terminal 1301, and the cathode of the other end is electrically connected to the ground. The plurality of diodes may be diode-connected transistors as shown in FIG. 5. For example, the reference potential section D10 may be configured by connecting ten diode-connected transistors in series to generate the reference voltage V ｒｅｆ may be configured to generate

[0043] The transistor Q10 is current-mirror-connected to one of the diode-connected transistors that make up the reference potential section D10 (e.g., the transistor corresponding to the other end). The emitter of the transistor Q10 is electrically connected to ground, the base is electrically connected to the base of one of the diode-connected transistors that make up the reference potential section D10, and the collector is electrically connected to the emitter of the transistor Q40 in the amplifier section 1340. This allows the comparator section 1310 to detect that the final-stage amplifier 1200 has reached saturation with a simple configuration.

[0044] The amplifier unit 1340 includes, for example, at least one transistor. Here, as an example, the amplifier unit 1340 is described as including a transistor Q40 and a transistor Q41.

[0045] The transistor Q40 has a base connected to a reference voltage V ｒｅｆ１ is supplied to transistor Q40, its emitter is electrically connected to the collector of transistor Q10 in comparison unit 1310 to receive output signal RF30, and its collector is electrically connected to the base of transistor Q41. In other words, the emitter of transistor Q40 corresponds to the input terminal of amplifier unit 1340, which is electrically connected to the output terminal of comparison unit 1310. The emitter of transistor Q40 is also electrically connected to ground through resistor R40. The collector of transistor Q40 is electrically connected to the power supply through resistor R41.

[0046] The transistor Q41 has a base connected to a reference voltage V ｒｅｆ２is supplied through resistor R42, the emitter is electrically connected to ground, and the collector is electrically connected to one end of DC removal unit 1320. In other words, the collector of transistor Q41 corresponds to the output terminal of amplifier unit 1340, which is electrically connected to one terminal of DC removal unit 1320. The collector of transistor Q41 is electrically connected to the power supply through resistor R43. The base of transistor Q41 may be electrically connected to the collector of transistor Q40 through a capacitor (not shown) for removing DC components. This more reliably removes DC components from signal RF20, thereby more reliably eliminating response delays.

[0047] The DC removal unit 1320 includes, for example, a capacitor C20. The capacitor C20 has one terminal electrically connected to the collector of the transistor Q41 and the other terminal electrically connected to the detection unit 1330.

[0048] The DC removal unit 1320 removes DC components contained in the output signal RF20 amplified by the amplifier unit 1340, which cause the signal to take time to stabilize due to the influence of the operation of the comparator unit 1310 (e.g., the operation of the transistor Q10). That is, the DC removal unit 1320 outputs the output signal RF40, which is a high-frequency component, to the detector unit 1330. In this way, the DC removal unit 1320 DC-isolates the comparator unit 1310 and the detector unit 1330 so that the DC components that cause the signal to take time to stabilize do not act on the detector unit 1330. In other words, the protection circuit 1300 removes DC components that cause the signal to take time to stabilize and uses the high-frequency components as the detection signal. This eliminates the response delay that occurs when the DC components output from the comparator unit 1310 are used as the detection signal.

[0049] The detection unit 1330 is configured to include, for example, a transistor Q30. The base of the transistor Q30 is connected in series with the other end of the DC removal unit 1320 to receive the output signal RF30, the emitter is electrically connected to the ground, and the collector (output terminal) is electrically connected to the detection terminal 1302. It is also desirable that a capacitor C30 be provided between the collector of the transistor Q30 and the ground, which serves as a filter for suppressing the fundamental wave. The base of the transistor Q30 is connected to a reference voltage V ｒｅｆ１ is supplied through transistor Q51 and resistor R30. Furthermore, transistor Q30 smoothes the high frequency components of output signal RF40 output from DC removal unit 1320 into DC using a capacitor (not shown) for smoothing high frequency signals, and outputs the smoothed signal.

[0050] In the above description, the collector of transistor Q30 is electrically connected to detection terminal 1302, but the emitter may also be electrically connected to detection terminal 1302. This increases the input impedance of detection unit 1330, allowing for a smaller input current. In other words, it is possible to suppress AC interaction between detection unit 1330 and comparison unit 1310 and stabilize the AC output of comparison unit 1310.

[0051] <<Operation of Protection Circuit 1300>> Next, the operation of the protection circuit 1300 will be described.

[0052] The instantaneous maximum collector or drain voltage of the final stage amplifier 1200 increases as the final stage amplifier 1200 approaches saturation. The comparator 1310 compares the collector or drain voltage of the final stage amplifier 1200 with a reference voltage V ｒｅｆ When the voltage (signal level) of the input signal RF10 input to the input terminal 1301 is equal to or higher than the reference voltage V ｒｅｆ During the above period, the conduction state is established.

[0053] The conduction angle is the angular range over which the conduction state lasts, and the conduction angle increases as the input signal RF10 increases. As the conduction angle increases, the DC component of the output signal RF30 output from the comparator 1310 also increases.

[0054] In the conductive state, a voltage is supplied to the base of the current mirror-connected transistor Q10, turning the transistor Q10 on. When the transistor Q10 is on, a current flows to the collector of the transistor Q10, turning on the transistor Q40 of the amplifier 1340 and causing a current to flow to the collector of the transistor Q40. Then, a current flows to the base of the transistor Q41, causing the transistor Q41 to operate. The DC removal unit 1320 removes the DC component from the signal output from the collector of the transistor Q41 and outputs the high frequency component output signal RF40 to the detector 1330. The detector 1330 amplifies the output signal RF40 from which the DC component has been removed, smooths the amplified signal, and outputs the control signal D ｃｏｎｔ Output as

[0055] <<Protection Circuit 1300a According to First Modification>> Next, a protection circuit 1300a according to a first modification will be described with reference to Fig. 6. Fig. 6 is a diagram showing the configuration of the protection circuit 1300a according to the first modification. Below, only the configuration different from the protection circuit 1300 will be described, and unless otherwise specified, it will be assumed that the configuration is the same as the protection circuit 1300. Compared to the protection circuit 1300, the protection circuit 1300a has an amplifier unit 1340, a DC removal unit 1320, and a detection unit 1330 that are configured as differential circuits.

[0056] As shown in FIG. 6, the protection circuit 1300a includes an amplifier 1340a, a DC removal unit 1320a, and a detection unit 1330a.

[0057] The amplifier 1340a configures a differential circuit with a first amplifier 1341a and a second amplifier 1342a. That is, the amplifier 1340a amplifies the output signal RF30 output from the comparator 1310 and converts the output signal RF30 into a differential signal.

[0058] The first amplifier section 1341a may be configured, for example, by connecting multiple transistors Q40 and Q41 in cascade (i.e., among the multiple transistors, the output terminal of the previous transistor is connected to the input terminal of the next transistor).

[0059] The transistor Q40 has a base connected to a reference voltage V ｒｅｆ１ The emitter of the transistor Q40 is electrically connected to the ground through a resistor R40, and the collector is electrically connected to the base of a transistor Q41. The output signal RF20 output from the comparator 1310 is input to the emitter of the transistor Q40. The transistor Q41 has a base connected to a reference voltage V ｒｅｆ１ is supplied through a resistor R42, the emitter is electrically connected to ground through a transistor Q52 (for example, a transistor that serves as a current source), and the collector is electrically connected to a first DC removal unit 1321a described later.

[0060] The second amplifier section 1342a may be configured by connecting a plurality of transistors Q42 and Q43 in cascade, for example.

[0061] The transistor Q42 has a base connected to a reference voltage V ｒｅｆ１ The emitter of the transistor Q42 is electrically connected to the ground through a resistor R44, and the collector is electrically connected to the base of a transistor Q43. The collector of the transistor Q42 is connected to the ground through a capacitor C40 for attenuating high frequency components. The transistor Q43 has a base connected to a reference voltage V ｒｅｆ１ is supplied through a resistor R46, the emitter is electrically connected to the ground through a transistor Q52, and the collector is electrically connected to a second DC removal unit 1322a, which will be described later.

[0062] The DC removal unit 1320a includes a first DC removal unit 1321a and a second DC removal unit 1322a. The first DC removal unit 1321a is a capacitor having one terminal electrically connected to the collector of transistor Q41 of the first amplifier unit 1341a and the other terminal electrically connected to a first detector unit 1331a (described later). The first DC removal unit 1321a outputs an output signal RF41, which is obtained by removing the DC component from the output signal RF20, from the other terminal. The second DC removal unit 1322a is a capacitor having one terminal connected in series to the collector of transistor Q43 of the second amplifier unit 1342a and the other terminal connected in series to a second detector unit 1332a (described later). The second DC removal unit 1322a outputs an output signal RF42, which is approximately 180 degrees out of phase with the output signal RF31, from the other terminal. Approximately 180 degrees includes the range of 135 degrees to 225 degrees, for example.

[0063] The detection unit 1330a includes, for example, a transistor Q30 and a transistor Q31. The base of the transistor Q30 is electrically connected to the other terminal of the first DC removal unit 1321a, the emitter is electrically connected to ground, and the collector is electrically connected to the detection terminal 1302. The base of the transistor Q31 is electrically connected to the other terminal of the second DC removal unit 1322a, the emitter is electrically connected to ground, and the collector is electrically connected to the detection terminal 1302. That is, the detection unit 1330a outputs, from the detection terminal 1302, a signal obtained by combining a signal output from the collector of the transistor Q30 and a signal output from the collector of the transistor Q31 that is approximately 180 degrees out of phase with the signal output from the collector of the transistor Q30. The bases of the transistors Q30 and Q31 are electrically connected to ground via a transistor Q50 (e.g., a transistor that serves as a current source).

[0064] In this way, because the protection circuit 1300a is configured with differential circuits, the leaking odd-order harmonic components cancel each other out, suppressing the impact of the leak on the circuit. As a result, the protection circuit 1300a can reduce the size of the filter circuit (not shown) that extracts the DC component and is provided downstream, thereby further improving the response time delay.

[0065] 7, a description will be given of the configuration of the protection circuit 1300a when a differential signal is input to the protection circuit 1300a from the differential final stage amplifier 1200. Fig. 7 is a diagram showing another example of the configuration of the protection circuit 1300a according to the first modified example.

[0066] 7 , the protection circuit 1300a is configured to receive differential signals RF21 and RF22, which are approximately 180 degrees out of phase, from the differential final-stage amplifier 1200. Specifically, the protection circuit 1300a includes a comparison unit 1311a and a comparison unit 1312a. Here, the description will be given assuming that the final-stage amplifier 1200 is configured to include a first final-stage amplifier 1210 and a second final-stage amplifier 1220.

[0067] The comparison unit 1311a includes a reference potential unit D10 and a transistor Q10. The reference potential unit D10 and the transistor Q10 are the same as the reference potential unit D10 and the transistor Q10 of the comparison unit 1310, and therefore a description thereof will be omitted.

[0068] The comparison section 1312a includes a reference potential section D11 and a transistor Q11.

[0069] The reference potential section D11 is configured by, for example, connecting a plurality of diodes in series. The anode of the reference potential section D11 is electrically connected to the input terminal 1301a, and the cathode of the other end is electrically connected to the ground. The plurality of diodes may be, for example, diode-connected transistors as shown in FIG. 7. For example, the reference potential section D11 may be configured by connecting ten diode-connected transistors in series to generate a reference voltage V ｒｅｆ may be configured to generate

[0070] The transistor Q11 is current-mirror-connected to one of the diode-connected transistors that make up the reference potential section D11 (e.g., the transistor corresponding to the other end). The transistor Q11 has, for example, an emitter electrically connected to ground, a base electrically connected to the base of one of the diode-connected transistors that make up the reference potential section D11, and a collector electrically connected to the emitter of the transistor Q42 of the second amplifier section 1342a.

[0071] In this way, since the protection circuit 1300a shown in FIG. 7 is composed of a differential circuit, the leaking odd-order harmonic components cancel each other out, suppressing the effects of leakage on the circuit and also being compatible with the differential final stage amplifier 1200.

[0072] <<Protection Circuit 1300b According to Second Modification>> Next, a protection circuit 1300b according to a second modification will be described with reference to FIG. 8. FIG. 8 is a diagram showing the configuration of the protection circuit 1300b according to the second modification. Below, only the configurations different from those of the protection circuit 1300a shown in FIG. 6 will be described, and unless otherwise specified, the protection circuit 1300b will be considered to be the same as the protection circuit 1300a shown in FIG. 6. For example, the amplifier unit 1340a, DC removal unit 1320a, and detection unit 1330a in the protection circuit 1300a are the same as the amplifier unit 1340b, DC removal unit 1320b, and detection unit 1330b in the protection circuit 1300b, and therefore their description will be omitted. Compared to the protection circuit 1300a, the protection circuit 1300b has a configuration in which a transistor Q12 is added to the comparison unit 1310a in the protection circuit 1300a.

[0073] 6, the comparator 1310b of the protection circuit 1300b includes a transistor Q12. The transistor Q12 receives the input signal RF20 output from the final stage amplifier 1200 at its collector, has its base electrically connected to the emitter of the transistor Q42 of the second amplifier 1342a, and has its emitter electrically connected to ground. The transistor Q12 operates when the instantaneous minimum voltage of the collector of the final stage amplifier 1200 approaches 0V. When the final stage amplifier 1200 is close to saturation, the instantaneous minimum voltage of the collector of the final stage amplifier 1200 approaches 0V. In other words, even when the final stage amplifier 1200 is in a saturated state where the instantaneous minimum voltage of the final stage amplifier 1200 approaches 0V, the protection circuit 1300b continues to receive a control signal from the detector 1330b. Ｄｃｏｎｔ Output the following.

[0074] In the protection circuit 1300b, the instantaneous maximum voltage of the collector of the final stage amplifier 1200 is equal to the reference voltage V ｒｅｆ When the instantaneous maximum voltage of the collector of the final stage amplifier 1200 approaches 0V, the reference potential section D10 and the transistor Q10 operate, and when the instantaneous minimum voltage of the collector of the final stage amplifier 1200 approaches 0V, the transistor Q12 operates. In other words, the protection circuit 1300b detects the saturation state of the final stage amplifier 1200 based on the upper and lower limits of the collector voltage of the final stage amplifier 1200, and can suppress the output of the final stage amplifier 1200. Furthermore, the protection circuit 1300b detects the saturation state of the final stage amplifier 1200 based on the upper and lower limits of the collector voltage of the final stage amplifier 1200 when the instantaneous maximum voltage of the collector of the final stage amplifier 1200 approaches the reference voltage V ｒｅｆ When the minimum instantaneous voltage of the collector of the final stage amplifier 1200 approaches 0V, the control signal D ｃｏｎｔ Therefore, the final stage amplifier 1200 can be prevented from being destroyed more reliably.

[0075] 9, a description will be given of the configuration of the protection circuit 1300b when a differential signal is input to the protection circuit 1300b from the differential final stage amplifier 1200. Fig. 9 is a diagram showing another example of the configuration of the protection circuit 1300b according to the second modification.

[0076] 9 , the protection circuit 1300b is configured to receive differential signals RF11 and RF12 having a phase difference of approximately 180 degrees from the differential final-stage amplifier 1200. Specifically, the protection circuit 1300b includes a comparison unit 1311b and a comparison unit 1312b. Here, the description will be given assuming that the final-stage amplifier 1200 is configured to include a first final-stage amplifier 1210 and a second final-stage amplifier 1220.

[0077] The comparison unit 1311b includes a reference potential unit D10, a transistor Q10, and a transistor Q12. A differential signal RF11 is input to an input terminal 1301 of the comparison unit 1311b from the first final stage amplifier 1210. Note that the reference potential unit D10 and the transistor Q10 of the comparison unit 1311b are the same as the reference potential unit D10, the transistor Q10, and the transistor Q12 of the comparison unit 1310b shown in FIG. 8, and therefore a description thereof will be omitted.

[0078] The comparison unit 1312b includes a reference potential unit D12, a transistor Q13, and a transistor Q14. A differential signal RF12 having a phase difference of approximately 180 degrees from that of the differential signal RF11 is input to an input terminal 1301b of the comparison unit 1312b from the second final stage amplifier 1220.

[0079] The reference potential section D12 is configured by, for example, connecting a plurality of diodes in series. The anode of the reference potential section D12 is electrically connected to the input terminal 1301a, and the cathode of the other end is electrically connected to the ground. The plurality of diodes may be, for example, diode-connected transistors. For example, the reference potential section D12 may be configured by connecting ten diode-connected transistors in series to generate a reference voltage V ｒｅｆ may be configured to generate

[0080] The transistor Q13 is current-mirror-connected to one of the diode-connected transistors that make up the reference potential section D12 (e.g., the transistor corresponding to the other end). The transistor Q13 has, for example, an emitter electrically connected to ground, a base electrically connected to the base of one of the diode-connected transistors that make up the reference potential section D12, and a collector electrically connected to the emitter of the transistor Q42 in the amplifier section 1342b.

[0081] The transistor Q14 receives the differential signal RF12 output from the second final stage amplifier 1220 at its collector, has its base electrically connected to the emitter of the transistor Q40 in the amplifier unit 1341b, and has its emitter electrically connected to ground. The transistor Q14 operates when the instantaneous minimum voltage of the collector of the second final stage amplifier 1220 approaches 0V. When the second final stage amplifier 1220 approaches saturation, the instantaneous minimum voltage of the collector of the second final stage amplifier 1220 approaches 0V. In other words, even when the second final stage amplifier 1220 is in a saturated state where the instantaneous minimum voltage of the second final stage amplifier 1220 approaches 0V, the protection circuit 1300b continues to receive the control signal RF12 from the detector 1330b. Ｄｃｏｎｔ Output the following.

[0082] In the protection circuit 1300b shown in FIG. 9, the instantaneous maximum voltage of the collector of the differential final stage amplifier 1200 (1210, 1220) is equal to the reference voltage V ｒｅｆ When the instantaneous maximum collector voltage of the differential final stage amplifier 1200 approaches the reference voltage V, the reference potential section D10 and transistor Q10 of the comparison section 1311b and the reference potential section D12 and transistor Q14 of the comparison section 1312b operate. Furthermore, in the protection circuit 1300b shown in FIG. 9, when the instantaneous minimum collector voltage of the final stage amplifier 1200 approaches 0V, the transistor Q12 of the comparison section 1311b and the transistor Q14 of the comparison section 1312b operate. In other words, the protection circuit 1300b detects the saturation state of the differential final stage amplifier 1200 based on the upper and lower limits of the collector voltage of the differential final stage amplifier 1200, and can suppress the output of the differential final stage amplifier 1200. Furthermore, the protection circuit 1300b shown in FIG. 9 detects the saturation state of the differential final stage amplifier 1200 based on the upper and lower limits of the collector voltage of the differential final stage amplifier 1200, and can suppress the output of the differential final stage amplifier 1200.ｒｅｆ 8. When the instantaneous minimum voltage of the collector of the differential final stage amplifier 1200 approaches 0V, the control signal D ｃｏｎｔ Therefore, the differential final stage amplifier 1200 can be prevented from being destroyed more reliably.

[0083] ===Summary=== <1> In the power amplifier circuit 1000 including at least one amplifier, when the signal level of the signal RF20 (for example, signals RF21 and RF22 when the final stage amplifier 1200 is differential) output from, for example, the final stage amplifier 1200 (a predetermined amplifier) ​​of the at least one amplifier is equal to or higher than a reference voltage, the protection circuit 1300 ｒｅｆ a DC removal unit 1320 having one terminal electrically connected to the output terminal of the comparison unit 1310 and outputting from the other terminal a signal obtained by removing the DC component from the output signal RF30; a DC removal unit 1320 having a base (input terminal) electrically connected to the other terminal of the DC removal unit 1320 and outputting from a collector (output terminal) a control signal D corresponding to the signal level of the signal output from the final stage amplifier 1200 (a predetermined amplifier); ｃｏｎｔ and a detection unit 1330 that outputs the output signal RF30 from the comparison unit 1310 to a predetermined circuit that can reduce the gain of the power amplifier circuit 1000. As a result, the protection circuit 1300 removes the DC component from the output signal RF30 output from the comparison unit 1310, thereby improving the delay in the response time of the comparison unit 1310 that is caused by the DC component. It is also possible to suppress fluctuations in the bias point of the detection unit 1330. Therefore, when the final stage amplifier 1200 is saturated or begins to saturate, the protection circuit 1300 reduces the gain of the driver stage amplifier 1100 and the final stage amplifier 1200 at an appropriate timing, thereby suppressing the gain of the entire circuit. This makes it possible for the protection circuit 1300 to prevent damage to the final stage amplifier 1200 due to voltage fluctuations in the power amplifier circuit 1000.

[0084] <2> The protection circuit 1300 according to <1>, further including an amplifier unit 1340 having an input terminal (e.g., the emitter of the transistor Q40) electrically connected to the output terminal of the comparison unit 1310 and an output terminal (e.g., the collector of the transistor Q41) electrically connected to one terminal of the DC removal unit 1320. This enables the protection circuit 1300 to sensitively monitor the saturation state of the final stage amplifier 1200.

[0085] <3> The amplifier 1340a in the protection circuit 1300a includes a differential circuit (a circuit including transistors Q40 to Q43) including a transistor Q40 (first transistor) to whose emitter the output signal RF30 is input, and a transistor Q42 (second transistor) whose emitter or source is electrically connected to a reference potential, and the DC removal unit 1320a includes a capacitor C20 whose one terminal is electrically connected to the collector (or emitter) of a transistor Q41 (first transistor) whose base is connected to the collector (or emitter) of the transistor Q40. The protection circuit according to <2> includes a first capacitor (C20) and a second capacitor (C21) having one terminal electrically connected to the collector of a second transistor (Q43) whose base is connected to the collector (or emitter) of the transistor Q42. The detection unit 1330a includes a third transistor (Q30) having a base electrically connected to the other terminal of the first capacitor (C20) and a fourth transistor (Q31) having a base electrically connected to the other terminal of the second capacitor (C21). Because the protection circuit 1300a is configured as a differential circuit, odd-order harmonic components that leak cancel each other out, suppressing the effects of leakage on the circuit. This allows the protection circuit 1300a to reduce the size of a filter circuit (not shown) that extracts DC components and further improving response time.

[0086] <4> The protection circuit according to any one of <1> to <3>, wherein the comparison unit 1310 in the protection circuit 1300 includes a plurality of diodes or a plurality of diode-connected transistors, one end of which is electrically connected to an input terminal 1301 to which a signal RF20 output from the final stage amplifier 1200 (a predetermined amplifier) ​​is input and the other end of which is electrically connected to ground (reference potential), and includes a transistor Q10 (a fifth transistor) that is current-mirror-connected to any one of the plurality of diodes or any one of the plurality of diode-connected transistors and has a collector electrically connected to one terminal of the DC removal unit 1320. This enables the protection circuit 1300 to detect, with a simple configuration, that the final stage amplifier 1200 is saturated.

[0087] <5> The protection circuit according to any one of <1> to <3>, wherein the comparison unit 1310 includes a plurality of diodes or a plurality of diode-connected transistors, one end of which is electrically connected to an input terminal 1301 to which a signal RF20 output from a final stage amplifier 1200 (a predetermined amplifier) ​​is input and the other end of which is electrically connected to ground (reference potential), and includes a transistor Q10 (a fifth transistor) that is current-mirror-connected to any one of the plurality of diodes or any one of the plurality of diode-connected transistors; the protection circuit 1300 further includes an amplification unit 1340 including a transistor Q40 (a sixth transistor) having an emitter or a source electrically connected to a collector or a drain of the transistor Q10 (a fifth transistor); the DC removal unit 1320 has one terminal electrically connected to the collector or the drain of the transistor Q40 (sixth transistor); and the detection unit 1330 includes a transistor Q30 (a seventh transistor) having a base or a gate electrically connected to the other terminal of the DC removal unit 1320. This allows the protection circuit 1300 to detect that the final stage amplifier 1200 has reached saturation with a simple configuration.

[0088] <6> The protection circuit according to any one of <1> to <5>, wherein the comparator 1310b in the protection circuit 1300b includes a transistor Q12 (eighth transistor) to whose collector the signal RF20 output from the final stage amplifier 1200 (predetermined amplifier) ​​is input and whose base is electrically connected to the emitter of the transistor Q42 (second transistor). As a result, the protection circuit 1300b is configured to detect whether the instantaneous maximum voltage of the collector of the final stage amplifier 1200 is equal to or greater than the reference voltage V ｒｅｆ When the minimum instantaneous voltage of the collector of the final stage amplifier 1200 approaches 0V, the control signal D ｃｏｎｔ Therefore, the gain of the power amplifier circuit 1000 can be more reliably suppressed.

[0089] <7> The final stage amplifier 1200 (predetermined amplifier) ​​of the power amplifier circuit 1000 (amplifier circuit) is a first final stage amplifier 1210 (first amplifier) ​​and a second final stage amplifier 1220 (second amplifier) ​​that constitute a differential circuit, and the comparison unit 1310a in the protection circuit 1300a detects whether the signal level of the signal RF21 output from the first final stage amplifier 1210 (first amplifier) ​​is equal to or greater than the reference voltage V ｒｅｆ (first reference voltage) or higher, the signal level and the reference voltage V ｒｅｆ A comparator 1311a (first comparator) outputs a signal RF31 (first output signal) corresponding to the difference between the reference voltage V and the output of the transistor Q40 (first transistor), and a comparator 1311b (first comparator) outputs a signal RF31 (first output signal) corresponding to the difference between the reference voltage V and the output of the transistor Q40 (first transistor). ｒｅｆ (second reference voltage) or more, the signal level and the reference voltage V ｒｅｆ and a comparator 1312a (second comparator) that outputs a signal RF32 (second output signal) corresponding to the difference between the first reference voltage and the second reference voltage to the emitter of the transistor Q42 (second transistor). As a result, since the protection circuit 1300a is configured as a differential circuit, odd-order harmonic components that leak cancel each other out, which can suppress the influence of the leakage on the circuit and can also be used with the differential final-stage amplifier 1200.

[0090] <8> The protection circuit according to <7>, wherein the comparator 1311b in the protection circuit 1300b includes a transistor Q12 (ninth transistor) having a collector to which the signal RF21 output from the first final stage amplifier 1210 (first amplifier) ​​is input and a base electrically connected to the emitter of the transistor Q42 (second transistor), and the comparator 1312b includes a transistor Q14 (tenth transistor) having a collector to which the signal RF22 output from the second final stage amplifier 1220 (second amplifier) ​​is input and a base electrically connected to the emitter of the transistor Q40 (first transistor). ｒｅｆ If the instantaneous minimum voltage of the collector of the differential final stage amplifier 1200 approaches 0V, the control signal D ｃｏｎｔ Therefore, the gain of the power amplifier circuit 1000 can be more reliably suppressed.

[0091] <9> The power amplifier circuit 1000b (amplifier circuit) is a circuit including a carrier amplifier circuit configured of at least one carrier amplifier 1120, 1130, and a peak amplifier circuit configured of at least one peak amplifier 1140, 1150, and the comparator 1310 compares the maximum signal level of the signal RF20 output from the final-stage carrier amplifier 1130 (predetermined carrier amplifier) ​​of the at least one carrier amplifier in the carrier amplifier circuit with the reference voltage V ｒｅｆ and outputs an output signal corresponding to the difference between the control signal D ｃｏｎｔ to a predetermined circuit (here, at least one of the bias circuits 1111, 1121, and 1131 shown in FIG. 3 , or an attenuator not shown) capable of reducing the gain of the carrier amplifier circuit. As a result, the power amplifier circuit 1000b can suppress the gain of the power amplifier circuit 1000 by reducing the bias of the final-stage carrier amplifier 1130 at an appropriate timing when the final-stage carrier amplifier 1130 is saturated or begins to be saturated.

[0092] The above-described embodiments are intended to facilitate understanding of the present disclosure and are not intended to limit the present disclosure. The present disclosure may be modified or improved without departing from its spirit, and equivalents thereof are also included in the present disclosure. In other words, designs modified by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements and their arrangements included in the embodiments are not limited to those exemplified and can be modified as appropriate.

[0093] 1000...power amplifier circuit, 1100...driver stage amplifier, 1200...final stage amplifier, 1300...protection circuit, 1310...comparison section, 1320...DC removal section, 1330...detection section, 1340...amplification section.

Claims

1. A protection circuit comprising: a comparison section for, in a power amplifier circuit including at least one amplifier, outputting from an output terminal an output signal corresponding to the difference between the signal level and the reference voltage when the signal level of a signal output from a predetermined amplifier of the at least one amplifier is equal to or higher than a reference voltage; a DC removal section having one terminal electrically connected to the output terminal of the comparison section and outputting from the other terminal a signal obtained by removing the DC component of the output signal; and a detection section having an input terminal electrically connected to the other terminal of the DC removal section and outputting from the output terminal a control signal corresponding to the signal level of the signal output from the predetermined amplifier to a predetermined circuit capable of reducing the gain of the power amplifier circuit.

2. The protection circuit according to claim 1, further comprising an amplifier section having an input terminal electrically connected to an output terminal of said comparison section and an output terminal electrically connected to one terminal of said DC removal section.

3. The protection circuit of claim 2, wherein the amplification section includes a differential circuit including a first transistor to which the output signal is inputted at its emitter or source, and a second transistor whose emitter or source is electrically connected to a reference potential; the DC removal section includes a first capacitor having one terminal electrically connected to the collector or drain of the first transistor, and a second capacitor having one terminal electrically connected to the collector or drain of the second transistor; and the detection section includes a third transistor having a base or gate electrically connected to the other terminal of the first capacitor, and a fourth transistor having a base or gate electrically connected to the other terminal of the second capacitor.

4. A protection circuit as claimed in any one of claims 1 to 3, wherein the comparison section includes a plurality of diodes or a plurality of diode-connected transistors, one end of which is electrically connected to an input terminal to which a signal output from the specified amplifier is input and the other end of which is electrically connected to a reference potential, and a fifth transistor, which is current-mirror-connected with any one of the plurality of diodes or any one of the plurality of diode-connected transistors, and whose collector or drain is electrically connected to the one terminal of the DC removal section.

5. The protection circuit according to any one of claims 1 to 3, wherein the comparison section includes a plurality of diodes or a plurality of diode-connected transistors, one end of which is electrically connected to an input terminal to which a signal output from the specified amplifier is input and the other end of which is electrically connected to a reference potential, and includes a fifth transistor that is current-mirror-connected with any one of the plurality of diodes or any one of the plurality of diode-connected transistors, the protection circuit further includes an amplification section including a sixth transistor, the emitter or source of which is electrically connected to the collector or drain of the fifth transistor, the DC removal section has one terminal electrically connected to the collector or drain of the sixth transistor, and the detection section includes a seventh transistor, the base or gate of which is electrically connected to the other terminal of the DC removal section.

6. The protection circuit according to claim 3, wherein the comparison section includes an eighth transistor having a collector or drain to which the signal output from the specified amplifier is input and a base or gate electrically connected to the emitter or source of the second transistor.

7. The protection circuit according to claim 3, wherein the predetermined amplifier of the power amplifier circuit is a first amplifier and a second amplifier constituting a differential circuit, and the comparison section includes: a first comparison section that, when a signal level of a signal output from the first amplifier is equal to or higher than a first reference voltage, outputs a first output signal corresponding to a difference between the signal level and the first reference voltage to the emitter or source of the first transistor, and a second comparison section that, when a signal level of a signal output from the second amplifier is equal to or higher than a second reference voltage, outputs a second output signal corresponding to a difference between the signal level and the second reference voltage to the emitter or source of the second transistor.

8. The protection circuit according to claim 7, wherein the first comparison unit includes a ninth transistor having a collector or drain to which the signal output from the first amplifier is input and a base or gate to which the emitter or source of the second transistor is electrically connected, and the second comparison unit includes a tenth transistor having a collector or drain to which the signal output from the second amplifier is input and a base or gate to which the emitter or source of the first transistor is electrically connected.

9. The protection circuit according to any one of claims 1 to 8, wherein the power amplifier circuit is a circuit including a carrier amplifier circuit composed of at least one carrier amplifier and a peak amplifier circuit composed of at least one peak amplifier, the comparator outputs from an output terminal an output signal corresponding to the difference between a reference voltage and a maximum value of a signal level of a signal output from a predetermined carrier amplifier of the at least one carrier amplifier in the carrier amplifier circuit, and the detector outputs the control signal to a predetermined circuit capable of reducing the gain of the carrier amplifier circuit.

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