Power amplifier, high-frequency module, and communication device

Abstract

Provided is a power amplifier that makes it possible to impart frequency characteristics to a voltage limit imposed by clamp diodes with respect to an output voltage of an amplifier circuit. A power amplifier (61) comprises an amplification circuit (63), a plurality of clamp diodes (D1), and a resonance circuit (70). The amplification circuit (63) amplifies a high-frequency signal. The plurality of clamp diodes (D1) are provided to a second path (M3) connecting the ground and an RF signal line (M1) that is connected to an output unit (63b) of the amplification circuit (63), the plurality of clamp diodes (D1) being connected in series with each other. At least a portion of the resonance circuit (70) is connected in series with the plurality of clamp diodes (D1).

Description

Power amplifiers, high frequency modules and communication devices

[0001] The present invention generally relates to a power amplifier, a high-frequency module, and a communication device, and more particularly to a power amplifier having a plurality of clamp diodes, a high-frequency module having the power amplifier, and a communication device having the high-frequency system.

[0002] The power amplifier disclosed in Patent Document 1 includes a power stage amplifier circuit (amplifier circuit), multiple clamp diodes, a switch, a temperature sensor, and a switch control circuit. The multiple clamp diodes are connected in series between an output of the power stage amplifier circuit and ground. The switch is connected between a lead-out point, which is an intermediate point between the multiple clamp diodes, and ground. The temperature sensor measures the temperature of the power stage amplifier circuit. The switch control circuit controls the switch to be on when the measurement value of the temperature sensor is equal to or less than a first threshold, and controls the switch to be off when the measurement value of the temperature sensor is equal to or greater than a second threshold.

[0003] In the power amplifier, when the switch is controlled to be on, the output voltage of the power stage amplifier circuit (i.e., the output voltage of the power amplifier) ​​is limited using the clamp diode between the power stage amplifier circuit and the draw point out of the plurality of clamp diodes. On the other hand, when the switch is controlled to be off, the output voltage of the power stage amplifier circuit is limited using all of the plurality of clamp diodes. That is, in the power amplifier, the number of the clamp transistors used to limit the output voltage of the power stage amplifier circuit is switched depending on the temperature of the power stage amplifier circuit.

[0004] Japanese Patent Application Laid-Open No. 2022-96838

[0005] In the power amplifier described in Patent Document 1, it is not possible to switch between enabling and disabling voltage limiting by the clamp diode on the output voltage of the power stage amplifier circuit (amplifier circuit) depending on the frequency of the output signal of the power stage amplifier circuit.

[0006] In view of the above problems, the present invention aims to provide a power amplifier, a high-frequency module, and a communication device that can provide frequency characteristics to the voltage limit by a clamp diode for the output voltage of an amplifier circuit.

[0007] A power amplifier according to one aspect of the present invention includes an amplifier circuit, a plurality of clamp diodes, and a resonant circuit. The amplifier circuit amplifies a high-frequency signal. The clamp diodes are connected in series to one another in a path connecting an RF signal line connected to an output of the amplifier circuit and ground. At least a portion of the resonant circuit is connected in series to the clamp diodes.

[0008] A high-frequency module according to one aspect of the present invention includes the power amplifier and a transmit filter, the transmit filter being connected to an output section of the power amplifier and having a passband that includes a transmit band of a first communication band.

[0009] A communication device according to one aspect of the present invention includes the high-frequency module and a signal processing circuit, the signal processing circuit being connected to the high-frequency module and processing a high-frequency signal.

[0010] The power amplifier, high frequency module, and communication device according to the present invention have the advantage that frequency characteristics can be imparted to the voltage limit imposed by the clamp diode on the output voltage of the amplifier circuit.

[0011] Fig. 1 is a block diagram of a high-frequency module and a communication device according to a first embodiment. Fig. 2 is a configuration diagram of a power amplifier provided in the high-frequency module. Fig. 3 is a configuration diagram of a power amplifier according to a first modification of the first embodiment. Fig. 4 is a configuration diagram of a power amplifier according to a second embodiment. Fig. 5 is a configuration diagram of a power amplifier according to the first modification of the second embodiment.

[0012] First Embodiment A radio frequency module 1 and a communication device 100 including a power amplifier according to a first embodiment will be described in detail with reference to the drawings.

[0013] (1) Overview As shown in Fig. 1, a power amplifier 61 according to the first embodiment includes a second amplifier circuit 63 (amplifier circuit), multiple clamp diodes D1, and a resonant circuit 70. The multiple clamp diodes D1 are provided in a path M3 (path) that connects a path M1 (RF signal line) connected to an output 63b of the second amplifier circuit 63 with ground, and are connected in series with each other. At least a portion of the resonant circuit 70 (the entire resonant circuit 70 in the example of Fig. 1) is connected in series with the multiple clamp diodes D1.

[0014] With this configuration, the resonant circuit 70 allows the clamp diode D1 to impart frequency characteristics to the voltage limiting of the output voltage of the second amplifier circuit 63. More specifically, when the frequency of the output signal of the second amplifier circuit 63 is within a certain frequency range that includes the resonant frequency of the resonant circuit 70, the resonant circuit 70 functions as a circuit with infinite impedance with respect to the output signal of the second amplifier circuit 63. Therefore, the output voltage of the second amplifier circuit 63 having a resonant frequency within the certain frequency range is not subject to voltage limiting by the clamp diode D1. As a result, the output voltage of the second amplifier circuit 63 having a frequency within the certain frequency range can be output to a stage downstream of the second amplifier circuit 63 at a voltage higher than the sum of the conduction voltages of the multiple clamp diodes D1. Furthermore, the output voltage of the second amplifier circuit 63 having a frequency outside the certain frequency range can be output to a stage downstream of the amplifier circuit 63 while being limited so as not to exceed the sum of the conduction voltages of the multiple clamp diodes D1.

[0015] (2) Configuration of the Communication Device As shown in FIG. 1 , the communication device 100 is a communication device including a high-frequency module 1. The communication device 100 is, for example, a mobile terminal (e.g., a smartphone), but is not limited to a mobile terminal and may be, for example, a wearable terminal (e.g., a smartwatch). The high-frequency module 1 is, for example, a module compatible with the 4G (fourth generation mobile communication) standard and the 5G (fifth generation mobile communication) standard. The 4G standard is, for example, 3GPP (registered trademark, Third Generation Partnership Project) or the LTE standard (registered trademark, Long Term Evolution). The 5G standard is, for example, 5G NR (New Radio).

[0016] In addition to the high-frequency module 1 , the communication device 100 further includes a signal processing circuit 2 and an antenna 3 .

[0017] The high-frequency module 1 is configured to amplify a reception signal (high-frequency signal) received by the antenna 3 and output the amplified signal to the signal processing circuit 2. The high-frequency module 1 is also configured to amplify a transmission signal (high-frequency signal) output from the signal processing circuit 2 and transmit the amplified signal from the antenna 3. The high-frequency module 1 is controlled by, for example, the signal processing circuit 2.

[0018] The signal processing circuit 2 is connected to the high-frequency module 1 and configured to process a received signal output from the high-frequency module 1. The signal processing circuit 2 is also configured to process a transmission signal to be output to the high-frequency module 1. The signal processing circuit 2 includes an RF (Radio Frequency) signal processing circuit 21 and a baseband signal processing circuit 22.

[0019] The RF signal processing circuit 21 is, for example, an RFIC (Radio Frequency Integrated Circuit), and performs signal processing on high-frequency signals (transmission signals and reception signals). The RF signal processing circuit 21 performs signal processing such as down-conversion on the reception signal output from the high-frequency module 1, and outputs the result to the baseband signal processing circuit 22. The RF signal processing circuit 21 also performs signal processing such as up-conversion on the transmission signal output from the baseband signal processing circuit 22, and outputs the result to the high-frequency module 1.

[0020] The baseband signal processing circuit 22 is, for example, a baseband integrated circuit (BBIC). The baseband signal processing circuit 22 outputs the received signal output from the RF signal processing circuit 21 to the outside. This output signal (received signal) can be used, for example, as an image signal for image display or as an audio signal for telephone calls. The baseband signal processing circuit 22 also generates a transmission signal from a baseband signal (e.g., an audio signal and an image signal) input from the outside and outputs the generated transmission signal to the RF signal processing circuit 21.

[0021] (3) Configuration of the High-Frequency Module 1 As shown in Fig. 1, the high-frequency module 1 includes a plurality of external terminals 10a to 10c and a plurality of electronic components. In the example of Fig. 1, the plurality of electronic components include a switch 20, matching circuits 31, 32, 51, and 52, a transmit filter 41, a receive filter 42, a power amplifier 61, and a low-noise amplifier 62.

[0022] The external terminal 10a is an antenna terminal to which the antenna 3 is connected. The external terminal 10b is connected to an output section (not shown) of the signal processing circuit 2 and is an input terminal for inputting a transmission signal processed by the signal processing circuit 2 to the high-frequency module 1. The external terminal 10c is connected to an input section (not shown) of the signal processing circuit 2 and is an output terminal for outputting a reception signal processed by the high-frequency module 1 to the input section of the signal processing circuit 2.

[0023] In the first embodiment, "A is connected to B" does not necessarily mean that A is directly connected to B, but also means that A is indirectly connected to B via another electronic component. Furthermore, "A is connected to B" means that A and B are electrically connected (i.e., electrically connected).

[0024] The switch 20 is, for example, an antenna switch. The switch 20 selects a connection destination of the external terminal 10a from among a plurality of filters (a transmit filter 41 and a receive filter 42 in the example of FIG. 1 ). The switch 20 is, for example, a switch IC (Integrated Circuit). The switch 20 is controlled by, for example, the signal processing circuit 2. The switch 20 has a common terminal 20a and a plurality of (two in the example of FIG. 1 ) selection terminals 20b and 20c. The common terminal 20a can be selectively connected to at least one of the plurality of selection terminals 20b and 20c. The common terminal 20a is connected to the external terminal 10a. The selection terminal 20b is connected to an output section 41b (described later) of the transmit filter 41 via a matching circuit 31. The selection terminal 20c is connected to an input section 42a (described later) of the receive filter 42 via the matching circuit 31.

[0025] The transmit filter 41 has a pass band that includes the transmit band of the first communication band. The transmit filter 41 has an input unit 41a and an output unit 41b. The input unit 41a is connected to the output unit 61b of the power amplifier 61 via a matching circuit 51. The output unit 41b is connected to the selection terminal 20b of the switch 20 via a matching circuit 31. The transmit filter 41 receives a signal (transmit signal) from the input unit 41a, restricts the input signal to a signal in the transmit band of the first communication band, and passes the restricted signal, and outputs the passed signal from the output unit 41b.

[0026] The receive filter 42 has a pass band that includes the receive band of a second communication band, which may be the same as or different from the first communication band. The receive filter 42 has an input unit 42a and an output unit 42b. The input unit 42a is connected to the selection terminal 20c of the switch 20 via the matching circuit 32. The output unit 42b is connected to the input unit 62a of the low-noise amplifier 62 via the matching circuit 52. The receive filter 42 receives a signal (received signal) from the input unit 42a, restricts the input signal to a signal in the receive band of the second communication band, passes the signal, and outputs the passed signal from the output unit 42b.

[0027] The power amplifier 61 amplifies a signal (transmission signal) input to the high-frequency module 1 from the signal processing circuit 2 via the external terminal 10b. The power amplifier 61 is connected between the external terminal 10b and the transmission filter 41. The power amplifier 61 has an input section 61a and an output section 61b. The input section 61a is connected to the external terminal 10b. The output section 61b is connected to the input section 41a of the transmission filter 41 via the matching circuit 51. The power amplifier 61 amplifies the signal (transmission signal) input to the input section 61a and outputs the amplified signal from the output section 61b.

[0028] The low-noise amplifier 62 amplifies the output signal (received signal) of the receive filter 42. The low-noise amplifier 62 is connected between the external terminal 10c and the receive filter 42. The low-noise amplifier 62 has an input section 62a and an output section 62b. The input section 62a is connected to the output section 42b of the receive filter 42 via the matching circuit 52. The output section 62b is connected to the external terminal 10c. The low-noise amplifier 62 amplifies the signal (received signal) input to the input section 62a and outputs the amplified signal from the output section 62b.

[0029] The matching circuit 31 is a circuit for achieving impedance matching between the selection terminal 20b of the switch 20 and the transmit filter 41. The matching circuit 31 is connected between the selection terminal 20b of the switch 20 and the transmit filter 41.

[0030] The matching circuit 32 is a circuit for achieving impedance matching between the selection terminal 20c of the switch 20 and the receive filter 42. The matching circuit 32 is connected between the selection terminal 20c of the switch 20 and the receive filter 42.

[0031] The matching circuit 51 is a circuit for achieving impedance matching between the transmit filter 41 and the power amplifier 61. The matching circuit 51 is connected between the transmit filter 41 and the power amplifier 61.

[0032] The matching circuit 52 is a circuit for achieving impedance matching between the receiving filter 42 and the low-noise amplifier 62. The matching circuit 52 is connected between the receiving filter 42 and the low-noise amplifier 62.

[0033] (4) Operation of the high-frequency module

[0034] (4-1) Operation During Transmission During transmission by the high-frequency module 1, the common terminal 20a is connected to the selection terminal 20b in the switch 20. A transmission signal is input to the external terminal 10b from the signal processing circuit 2. The transmission signal input to the external terminal 10b passes through the power amplifier 61, the matching circuit 51, the transmission filter 41, the matching circuit 31, the switch 20, and the external terminal 10a in this order, and is then transmitted from the antenna 3.

[0035] (4-2) Operation During Reception During reception by the high-frequency module 1, the common terminal 20a is connected to the selection terminal 20c in the switch 20. Then, the received signal is received by the antenna 3. The received signal received by the antenna 3 passes through the external terminal 10a, the switch 20, the matching circuit 32, the receiving filter 42, the matching circuit 52, the low-noise amplifier 62, and the external terminal 10c in this order, and is then output to the signal processing circuit 2.

[0036] 2, the power amplifier 61 is a power amplifier including a multi-stage (two-stage in the example of FIG. 2) amplifier circuit (a first amplifier circuit 66 and a second amplifier circuit 63). In addition to the input section 61a and the output section 61b, the power amplifier 61 includes the first amplifier circuit 66, the second amplifier circuit 63, an input matching circuit 64, an output matching circuit 65, a power supply input section 61c, a plurality of clamp diodes D1, and a resonant circuit 70.

[0037] The path between the input port 61 a and the output port 61 b ​​is an RF (Radio Frequency) signal line through which a high-frequency signal flows. The first amplifier circuit 66, the second amplifier circuit 63, the input matching circuit 64, and the output matching circuit 65 are provided on the RF signal line.

[0038] The power supply input unit 61c is connected to a power supply 131 that outputs a DC power supply voltage Vcc (e.g., 3.4 V), and receives the power supply voltage Vcc from the power supply 131. The power supply input unit 61c is also connected to an output unit 66b (described later) of the first amplifier circuit 66, and applies the power supply voltage Vcc from the power supply 131 to the output unit 66b. The power supply input unit 61c is also connected to an output unit 63b (described later) of the second amplifier circuit 63, and applies the power supply voltage Vcc from the power supply 131 to the output unit 63b.

[0039] The first amplifier circuit 66 is, for example, a drive stage amplifier circuit, and amplifies a signal (transmission signal) input to the input section 61a. The first amplifier circuit 66 has an input section 66a and an output section 66b. The input section 66a is connected to the input section 61a via the input matching circuit 64. The output section 66b is connected to an input section 63a (described later) of the second amplifier circuit 63. The output section 66b is also connected to the power supply input section 61c, and receives a power supply voltage Vcc from the power supply input section 61c. The first amplifier circuit 66 amplifies the signal (transmission signal) input to the input section 66a in accordance with the power supply voltage Vcc from the power supply input section 61c, and outputs the amplified signal from the output section 66b.

[0040] The second amplifier circuit 63 is, for example, a power stage (also referred to as an output stage) amplifier circuit, and amplifies the output signal (transmission signal) of the first amplifier circuit 66. The second amplifier circuit 63 is, for example, an HBT (Heterojunction Bipolar Transistor). The second amplifier circuit 63 has an input section 63a and an output section 63b. The input section 63a is connected to the output section 66b of the first amplifier circuit 66. The output section 63b is connected to the output section 61b via an output matching circuit 65. The output section 63b is also connected to the power supply input section 61c, and receives the power supply voltage Vcc from the power supply input section 61c. The second amplifier circuit 63 amplifies the signal (transmission signal) input to the input section 63a in accordance with the power supply voltage Vcc from the power supply input section 61c, and outputs the amplified signal from the output section 63b.

[0041] More specifically, the output port 63b of the second amplifier circuit 63 is connected to the input port 65a of the output matching circuit 65 via a path M1. The power supply input port 61c is connected to a branch point N1 of the path M1 via a path M2. The path M1 is an RF signal line that forms part of the RF signal line between the input port 61a and the output port 61b.

[0042] The input matching circuit 64 is a circuit for controlling the impedance between the input section 61 a and the first amplifier circuit 66. The input matching circuit 64 is connected between the input section 61 a and the first amplifier circuit 66. The input matching circuit 64 includes, for example, a capacitor and an inductor. The capacitor is connected, for example, between the input section 61 a and the first amplifier circuit 66. The inductor is connected, for example, between the end of the capacitor on the first amplifier circuit 66 side and ground.

[0043] The output matching circuit 65 is a circuit for controlling the impedance between the output section 61b and the second amplifier circuit 63. The output matching circuit 65 is connected between the output section 61b and the second amplifier circuit 63. The output matching circuit 65 includes, for example, an inductor and two capacitors. The inductor is connected, for example, between the output section 61b and the second amplifier circuit 63. The two capacitors are connected between both ends of the inductor and ground.

[0044] The multiple clamp diodes D1 are protection circuits that prevent the second amplifier circuit 63 from being destroyed by the output voltage of the second amplifier circuit 63. The multiple clamp diodes D1 are provided on a path M3 between the path M1 and ground. The path M3 connects a branch point N2 of the path M1 to the ground. The branch point N2 is, for example, located closer to the second amplifier circuit 63 than the branch point N1. The multiple clamp diodes D1 are connected in series with each other. The multiple clamp diodes D1 are provided on the path M3 so that the forward direction is from the branch point N2 toward the ground.

[0045] The conduction voltage of each of the multiple clamp diodes D1 is denoted by Vf. That is, each clamp diode D1 conducts when a voltage equal to or greater than the conduction voltage Vf is applied, and does not conduct when a voltage less than the conduction voltage Vf is applied. The number of multiple clamp diodes D1 is also denoted by N. For example, if Vf is 1.2 V and N is 8, then all of the multiple clamp diodes D1 switch from non-conductive (off) to conductive (on) when a voltage equal to or greater than 9.6 V is applied.

[0046] When the output voltage of the second amplifier circuit 63 is a voltage less than Vf×N, none of the multiple clamp diodes D1 are conductive. Therefore, the output current of the second amplifier circuit 63 does not flow to ground through the multiple clamp diodes D1. In this case, the output voltage of the second amplifier circuit 63 is not limited by the multiple clamp diodes D1 and is output to the output matching circuit 65 downstream of the second amplifier circuit 63. On the other hand, when the output voltage of the second amplifier circuit 63 is a voltage equal to or greater than Vf×N, all of the multiple clamp diodes D1 are conductive. Therefore, the output current of the second amplifier circuit 63 flows through the multiple clamp diodes D1 to ground. In this case, the voltage applied across the multiple clamp diodes D1 is Vf×N. Therefore, the output voltage of the second amplifier circuit 63 is limited to the same voltage as the voltage applied across the multiple clamp diodes D1 (Vf×N).

[0047] The resonant circuit 70 is a circuit that provides frequency characteristics to the voltage limiting effected by the clamp diode D1 on the output voltage of the second amplifier circuit 63. At least a portion of the resonant circuit 70 (the entire resonant circuit in the example of FIG. 1 ) is connected in series with multiple clamp diodes D1. More specifically, the resonant circuit 70 is provided on a path M3 that connects the path M1 to ground. In the example of FIG. 1 , the resonant circuit 70 is provided on the path M3 between the clamp diode D1a and ground. The clamp diode D1a is the clamp diode D1 connected to the end closest to ground among the multiple clamp diodes D1. The resonant circuit 70 is, for example, an LC resonant circuit including a capacitor C1 and an inductor L1. More specifically, the resonant circuit 70 is a parallel resonant circuit in which no current flows during resonance (i.e., a circuit with infinite impedance). The capacitor C1 and the inductor L1 are connected in parallel with each other. That is, the inductor L1 is connected between the clamp diode D1a and ground, and the capacitor C1 is connected in parallel with the inductor L1.

[0048] The resonant circuit 70 has a predetermined resonant frequency. The resonant circuit 70 not only resonates at the predetermined resonant frequency, but also substantially resonates at frequencies within a certain frequency range that includes the predetermined resonant frequency.

[0049] When the frequency of the output signal of the second amplifier circuit 63 is within the above-mentioned certain frequency range, the resonant circuit 70 resonates. Therefore, when viewed from the second amplifier circuit 63, the resonant circuit 70 appears as a circuit with infinite impedance (in other words, an open circuit). Therefore, the output signal of the second amplifier circuit 63 cannot flow through the resonant circuit 70. In other words, the output signal of the second amplifier circuit 63 does not flow to ground through the multiple clamp diodes D1. Therefore, the voltage limiting effect of the multiple clamp diodes D1 on the output voltage of the second amplifier circuit 63 no longer functions. As a result, the output voltage of the second amplifier circuit 63 can be greater than the voltage Vf×N.

[0050] Furthermore, if the frequency of the output signal of the second amplifier circuit 63 is not within the above-mentioned certain frequency range, the resonant circuit 70 does not resonate. Therefore, when viewed from the second amplifier circuit 63 side, the resonant circuit 70 appears as a circuit with finite impedance (in other words, a closed circuit). Therefore, the output signal of the second amplifier circuit 63 can flow through the resonant circuit 70. That is, the output signal of the second amplifier circuit 63 flows to ground through the multiple clamp diodes D1. Therefore, the voltage limiting effect of the multiple clamp diodes D1 on the output voltage of the second amplifier circuit 63 is functional. As a result, the output voltage of the second amplifier circuit 63 is limited to a voltage equal to or less than Vf×N.

[0051] The certain frequency range includes the pass band of the transmit filter 41. Therefore, when the second amplifier circuit 63 outputs a signal within the pass band of the transmit filter 41, the voltage of the output signal is not limited by the multiple clamp diodes D1 and is output to the downstream output matching circuit 65. As a result, the second amplifier circuit 63 can output a voltage higher than Vf×N to the downstream output matching circuit 65. On the other hand, when the second amplifier circuit 63 outputs a signal that is not included in the pass band of the transmit filter 41 (i.e., a signal that is not included in the certain frequency range), the voltage of the output signal is limited by the multiple clamp diodes D1 to a voltage equal to or lower than Vf×N and is output to the downstream output matching circuit 65.

[0052] In the first embodiment, the resonant circuit 70 is, for example, a band-elimination filter having a stop band that includes the transmission band of the transmission filter 41. Therefore, when the frequency of the output signal of the second amplifier circuit 63 is included in the stop band, the resonant circuit 70 blocks the output signal of the second amplifier circuit 63 from passing through the resonant circuit 70. As a result, the output signal of the second amplifier circuit 63 does not flow to the resonant circuit 70 side, but is output to the downstream output matching circuit 65. In other words, the voltage of the output signal of the second amplifier circuit 63 is output to the downstream output matching circuit 65 without being limited by the multiple clamp diodes D1. Therefore, the second amplifier circuit 63 can output a voltage higher than the voltage of Vf×N to the downstream output matching circuit 65.

[0053] On the other hand, when the frequency of the output signal of the second amplifier circuit 63 is not included in the stopband, the resonant circuit 70 does not prevent the output signal of the second amplifier circuit 63 from passing through the resonant circuit 70. That is, the output signal of the second amplifier circuit 63 flows through the multiple clamp diodes D1 to ground. As a result, the voltage of the output signal of the second amplifier circuit 63 is limited to a voltage of Vf×N by the multiple clamp diodes D1 and output to the output matching circuit 65 in the subsequent stage.

[0054] (6) Semiconductor Component Including Second Amplifier Circuit The second amplifier circuit 63 is configured as a semiconductor component 75. The multiple clamp diodes D1 are provided within the semiconductor component 75. That is, the semiconductor component 75 includes the second amplifier circuit 63 and the multiple clamp diodes D1. The semiconductor component 75 also includes multiple (e.g., three) external terminals 75a to 75c.

[0055] The external terminal 75b is an input terminal for inputting the output signal of the first amplifier circuit 66, and is connected to the output part 66b of the first amplifier circuit 66. The external terminal 75b is connected to the input part 63a of the second amplifier circuit 63.

[0056] The external terminal 75a is an output terminal for outputting the output signal of the second amplifier circuit 63 to the outside (the output matching circuit 65 in FIG. 2). The external terminal 75a is connected to the output part 63b of the second amplifier circuit 63 via a path M11. The external terminal 75a is connected to the input part 65a of the output matching circuit 65 via a path M12. The paths M11 and M12 constitute a path M1.

[0057] The external terminal 75c is a ground terminal connected to the ground. The external terminal 75c is connected to a branch point N1 of the path M12 via a path M31. A plurality of clamp diodes D1 are provided on the path M31. The external terminal 75c is connected to the ground via a path M32. The resonant circuit 70 is provided on the path M32. The paths M31 and M32 form a path M3.

[0058] (7) Effects The power amplifier 61 according to the first embodiment includes a second amplifier circuit 63, a plurality of clamp diodes D1, and a resonant circuit 70. The second amplifier circuit 63 amplifies a high-frequency signal. The plurality of clamp diodes D1 are provided in series with one another on a path M3 (second path) that connects a path M1 (first path) connected to the output 63b of the second amplifier circuit 63 with ground. The resonant circuit 70 is provided on the path M3.

[0059] According to this configuration, the resonant circuit 70 allows the clamp diode D1 to impart frequency characteristics to the voltage limiting of the output voltage of the amplifier circuit 63. More specifically, when the frequency of the output signal of the amplifier circuit 63 is within a certain frequency range that includes the resonant frequency of the resonant circuit 70, the resonant circuit 70 functions as a circuit with infinite impedance with respect to the output signal of the amplifier circuit 63. Therefore, the output voltage of the amplifier circuit 63 having a frequency within the certain frequency range is not subject to voltage limiting by the clamp diode D1. As a result, the amplifier circuit 63 can output an output voltage having a frequency within the certain frequency range to a stage downstream of the amplifier circuit 63 at a voltage higher than the sum (Vf×N) of the conduction voltages Vf of the multiple clamp diodes D1. Furthermore, the amplifier circuit 63 can output an output voltage having a frequency outside the certain frequency range to a stage downstream of the amplifier circuit 63 while limiting the output voltage so that it does not exceed the sum (Vf×N) of the conduction voltages Vf of the multiple clamp diodes D1. This makes it possible to prevent the output voltage of the second amplifier circuit 63 (the output voltage not included in the above-mentioned certain frequency range) from becoming an unintended high voltage.

[0060] In the power amplifier 61 according to the first embodiment, the resonant circuit 70 includes an inductor L1 and a capacitor C1 connected in parallel to each other. This configuration allows the resonant circuit 70 to be configured with a simple structure.

[0061] Furthermore, in the power amplifier 61 according to the first embodiment, a transmit filter 41 is connected to the output section 63b of the amplifier circuit 63. The transmit filter 41 has a pass band that includes the transmit band of the first communication band. The resonant circuit 70 is a band-elimination filter. The band-elimination filter has a stop band that includes the pass band of the transmit filter 41. With this configuration, the output voltage of a signal passing through the transmit filter 41 can be made higher than the sum (Vf×N) of the conduction voltages Vf of the multiple clamp diodes D1.

[0062] Furthermore, in the power amplifier 61 according to the first embodiment, the multiple clamp diodes D1 are provided inside the semiconductor component 75. This configuration can contribute to the miniaturization of the power amplifier 61.

[0063] The high-frequency module according to the first embodiment also includes a power amplifier 61 and a transmission filter 41. The transmission filter 41 is connected to an output section 61b of the power amplifier 61 and has a passband that includes the transmission band of the first communication band. This configuration makes it possible to provide a high-frequency module 1 that has the effects of the power amplifier 61.

[0064] The communication device 100 according to the first embodiment includes a high-frequency module 1 and a signal processing circuit 2. The signal processing circuit 2 is connected to the high-frequency module 1 and processes high-frequency signals. This configuration makes it possible to provide a communication device 100 that has the effects of a power amplifier 61.

[0065] (8) Modifications Modifications of the power amplifier 61 according to the first embodiment will be described. In the following description, the same configurations as those in the first embodiment will be omitted, and the description will focus on the configurations that are different from those in the first embodiment. The following modifications may be implemented in combination.

[0066] (8-1) Modification 1 As shown in Fig. 3, Modification 1 has the same configuration as Embodiment 1, except that at least one of the inductor L1 and the capacitor C1 (both in the example of Fig. 3) is replaced with a variable element (variable inductor L2, variable capacitor C2). That is, the power amplifier 61 according to Modification 1 includes at least one of the variable inductor L2 and the variable capacitor C2 (both in the example of Fig. 3). According to Modification 1, the resonant frequency of the resonant circuit 70 can be adjusted after the power amplifier 61 is manufactured.

[0067] (8-2) Modification 2 In the first embodiment, the high-frequency module 1 includes one transmit filter 41. However, the high-frequency module 1 may include multiple transmit filters. The multiple transmit filters include the transmit filter 41 and have different passbands. In Modification 2, the output signal of the power amplifier 61 passes through one of the multiple transmit filters and is transmitted from the antenna 3. In Modification 2, the fixed frequency range of the resonant circuit 70 includes the passbands of each of the multiple transmit filters. In other words, the stopband of the resonant circuit 70, which is a band-stop filter, includes the passbands of each of the multiple transmit filters. This allows the second amplifier circuit 63 to output a voltage exceeding Vf×N for signals within the passbands of each of the multiple transmit filters. Furthermore, the second amplifier circuit 63 can output a voltage limited to or below Vf×N for signals not included in the passbands of each of the multiple transmit filters.

[0068] (8-3) Modification 3 In the first embodiment, the semiconductor component 75 includes only the second amplifier circuit 63 out of the first amplifier circuit 62 and the second amplifier circuit 63. In Modification 3, the semiconductor component 75 includes both the first amplifier circuit 62 and the first amplifier circuit 63. In Modification 3, the semiconductor component 75 further includes a path between the first amplifier circuit 62 and the second amplifier circuit 63, a path between the second amplifier circuit 63 and the branch point N1, and the branch point N1.

[0069] (8-4) Modification 4 In the first embodiment, the entire resonant circuit 70 is connected in series with the multiple clamp diodes D1. However, only a part of the resonant circuit 70 (a part of the electronic components constituting the resonant circuit 70) may be connected in series with the multiple clamp diodes D1.

[0070] Second Embodiment A power amplifier 61 according to a second embodiment will be described with reference to FIG.

[0071] (1) Configuration As shown in Fig. 4, the power amplifier 61 according to the second embodiment differs from the power amplifier 61 according to the first embodiment in that the resonant circuit 70 is connected between two adjacent clamp diodes D1 among the multiple clamp diodes D1. In the example of Fig. 4, the resonant circuit 70 is connected between the first and second clamp diodes D1 from the ground side among the three clamp diodes D1.

[0072] Furthermore, in the power amplifier 61 according to the second embodiment, compared to the power amplifier 61 according to the first embodiment, at least one (inductor L1 in the example of FIG. 3 ) of the plurality of circuit elements (e.g., inductor L1 and capacitor C1) of the resonant circuit 70 is provided inside the semiconductor component 75. That is, in the second embodiment, of the plurality of circuit elements of the resonant circuit 70, the inductor L1 is provided inside the semiconductor component 75, and the capacitor C1 is arranged outside the semiconductor component 75. The capacitor C1 is configured as, for example, an SMD (Surface Mount Device) component that is separate from the semiconductor component 75.

[0073] More specifically, the semiconductor component 75 of the second embodiment is configured similarly to the semiconductor component 75 of the first embodiment, except that it further includes an inductor L1 and external terminals 75d and 75e.

[0074] The external terminal 75d is connected to the end of the inductor L1 on the branch point N2 side and is an output terminal for outputting the voltage at a first end of the inductor L1 on the branch point N2 side to the external capacitor C1. The external terminal 75d is connected to the first end of the capacitor C1. The external terminal 75e is connected to a second end of the inductor L1 on the ground side and is an input terminal for inputting a voltage from a second end of the external capacitor C1 (the end opposite to the first end). The external terminal 75e is connected to the second end of the capacitor C1.

[0075] (2) Effects In the power amplifier 61 according to the second embodiment, the resonant circuit 70 is connected between two adjacent clamp diodes D1 among the multiple clamp diodes D1. This configuration improves the degree of freedom in the layout of the resonant circuit 70.

[0076] In the power amplifier 61 according to the second embodiment, the resonant circuit 70 includes a plurality of circuit elements (inductor L1 and capacitor C1 in the example of FIG. 4 ). At least one of the plurality of circuit elements (inductor L1 in the example of FIG. 4 ) is provided inside a semiconductor component 75 including the amplifier circuit 63. This configuration can contribute to the miniaturization of the power amplifier 61.

[0077] (3) Modifications Modifications of the power amplifier 61 according to the second embodiment will be described. In the following description, the same configurations as those in the second embodiment will be omitted, and the description will focus on the configurations that are different from those in the second embodiment. The following modifications may be implemented in combination.

[0078] (3-1) Modification 1 (3-1-1) Configuration As shown in Fig. 5, Modification 1 has the same configuration as Embodiment 2, except that the positions of the inductor L1 and the capacitor C1 are interchanged. More specifically, in Modification 1, the capacitor C1 is provided inside the semiconductor component 75. Even more specifically, the capacitor C1 is connected between two adjacent clamp diodes among the multiple clamp diodes D1. The inductor L1 is disposed outside the semiconductor component 75. More specifically, the inductor L1 is configured as an SMD component separate from the semiconductor component 75.

[0079] In the first modification, the external terminal 75d is connected to a first end of the capacitor C1 on the branch point N2 side. The external terminal 75d is also connected to a first end of the inductor L1. The external terminal 75e is connected to a second end of the capacitor C1 on the ground side. The external terminal 75e is also connected to a second end of the inductor L1 (the end opposite to the first end).

[0080] (3-1-2) Effects In the power amplifier 61 according to the first modification, the plurality of circuit elements of the resonant circuit 70 include a capacitor C1 and an inductor L1. The capacitor C1 is provided inside the semiconductor component 75. The inductor L1 is configured as an SMD component separate from the semiconductor component 75.

[0081] According to this configuration, the capacitor C1 is provided inside the semiconductor component 75, which allows the power amplifier 61 to be miniaturized. Furthermore, since the capacitor C1 is provided inside the semiconductor component 75, it can be configured to be smaller. Furthermore, since the inductor L1 is configured as an SMD component separate from the semiconductor component 75, the inductor L1 can be made larger. In this way, by making the capacitor C1 smaller and the inductor L1 larger, the resonant frequency band of the resonant circuit 70 can be made wider.

[0082] Although the first and second embodiments and their modifications have been described above, the first and second embodiments and their modifications may be combined and implemented.

[0083] (Aspects) The present specification discloses the following aspects.

[0084] A power amplifier (61) of a first aspect includes an amplifier circuit (63), a plurality of clamp diodes (D1), and a resonant circuit (70). The amplifier circuit (63) amplifies a high-frequency signal. The plurality of clamp diodes (D1) are provided in a path (M3) connecting an RF signal line (M1) connected to an output section (63b) of the amplifier circuit (63) and ground, and are connected in series with each other. At least a portion of the resonant circuit (70) is connected in series with the plurality of clamp diodes (D1).

[0085] According to this configuration, the resonant circuit (70) allows the clamp diode (D1) to impart frequency characteristics to the voltage limiting of the output voltage of the amplifier circuit (63). More specifically, when the frequency of the output signal of the amplifier circuit (63) is within a certain frequency range that includes the resonant frequency of the resonant circuit (70), the resonant circuit (70) functions as a circuit with infinite impedance with respect to the output signal of the amplifier circuit (63). Therefore, the output voltage of the amplifier circuit (63) having a frequency within the certain frequency range is not subject to voltage limiting by the clamp diode (D1). As a result, the output voltage of the amplifier circuit (63) having a frequency within the certain frequency range can be output to a stage downstream of the amplifier circuit (63) at a voltage higher than the sum (Vf × N) of the conduction voltages (Vf) of the multiple clamp diodes (D1). In addition, the output voltage of the amplifier circuit (63) having a frequency outside the above-mentioned certain frequency range can be limited so as not to exceed the sum (Vf × N) of the conduction voltages (Vf) of each of the multiple clamp diodes (D1), and can be output to a stage subsequent to the amplifier circuit (63).

[0086] In the power amplifier (61) of the second aspect, the resonant circuit (70) in the first aspect includes an inductor (L1) and a capacitor (C1) connected in parallel with each other.

[0087] According to this configuration, the resonant circuit (70) can be configured with a simple structure.

[0088] In the power amplifier (61) of the third aspect, in the first or second aspect, the resonant circuit (70) is connected between two adjacent clamp diodes (D1) among the plurality of clamp diodes (D1).

[0089] This configuration allows for greater freedom in the layout of the resonant circuit (70).

[0090] In the power amplifier (61) of the fourth aspect, in any one of the first to third aspects, the resonant circuit (70) includes at least one of a variable inductor (L2) and a variable capacitor (C2).

[0091] According to this configuration, the resonant frequency of the resonant circuit (70) can be adjusted after the power amplifier (61) is manufactured.

[0092] In a fifth aspect of the power amplifier (61), in any one of the first to fourth aspects, a transmit filter (41) is connected to the output section (63b) of the amplifier circuit (63). The transmit filter (41) has a pass band that includes the transmit band of the first communication band. The resonant circuit (70) is a band-elimination filter. The band-elimination filter has a stop band that includes the pass band of the transmit filter (41).

[0093] According to this configuration, the output voltage of the signal passing through the transmission filter (41) can be made higher than the sum (Vf×N) of the conduction voltages (Vf) of the plurality of clamp diodes (D1).

[0094] In a power amplifier (61) of a sixth aspect, in any one of the first to fifth aspects, the resonant circuit (70) includes a plurality of circuit elements (an inductor L1 and a capacitor C1), at least one of which is provided inside a semiconductor component (75) including the amplifier circuit (63).

[0095] This configuration contributes to the miniaturization of the power amplifier (61).

[0096] In a seventh aspect of the power amplifier (61), in the sixth aspect, the plurality of circuit elements include a capacitor (C1) and an inductor (L1). The capacitor (C1) is provided inside a semiconductor component (75). The inductor (L1) is configured as an SMD component separate from the semiconductor component (75).

[0097] According to this configuration, the capacitor (C1) is provided inside the semiconductor component (75), so the capacitor (C1) can be made smaller. Also, the inductor (L1) is configured as an SMD component separate from the semiconductor component (75), so the inductor (L1) can be made larger. In this way, by making the capacitor (C1) smaller and the inductor (L1) larger, the resonant frequency band of the resonant circuit (70) can be made wider.

[0098] In the power amplifier (61) of the eighth aspect, in the sixth or seventh aspect, the plurality of clamp diodes (D1) are provided inside the semiconductor component (75).

[0099] This configuration contributes to the miniaturization of the power amplifier (61).

[0100] A high-frequency module (1) of a ninth aspect includes the power amplifier (61) of any one of the first to eighth aspects and a transmission filter (41). The transmission filter (41) is connected to an output section (61b) of the power amplifier (61) and has a passband that includes a transmission band of the first communication band.

[0101] According to this configuration, it is possible to provide a high frequency module (1) having the effect of a power amplifier (61).

[0102] A communication device (100) of a tenth aspect includes the high-frequency module (1) of the ninth aspect and a signal processing circuit (2). The signal processing circuit (2) is connected to the high-frequency module (1) and processes high-frequency signals.

[0103] According to this configuration, it is possible to provide a communication device (100) having the effect of the power amplifier (61).

[0104] REFERENCE SIGNS LIST 1 High frequency module 2 Signal processing circuit 3 Antenna 10a to 10c External terminal 20 Switch 20a Common terminal 20b, 20c Selection terminal 21 RF signal processing circuit 22 Baseband signal processing circuit 31, 32, 51, 52 Matching circuit 41 Transmitting filter 41a Input section 41b Output section 42 Receiving filter 42a Input section 42b Output section 61 Power amplifier 61a Input section 61b Output section 61c Power supply input section 62 Low noise amplifier 62a Input section 62b Output section 63 Second amplifier circuit (amplifier circuit) 63a Input section 63b Output section 64 Input matching circuit 65 Output matching circuit 65a Input section 66 First amplifier circuit 66a Input section 66b Output section 70 Resonant circuit 75 Semiconductor component 75a to 75e External terminals 100 Communication device 131 Power supply C1 Capacitor C2 Variable capacitor D1, D1a Clamp diode L1 Inductor L2 Variable inductor M1 Path (RF signal line) M2 Path M3 Path (path) M11 Path M12 Path M31 Path M32 Path N1, N2 Branch points Vcc Power supply voltage Vf Conduction voltage

Claims

1. A power amplifier comprising: an amplifier circuit for amplifying a high-frequency signal; a plurality of clamp diodes connected in series to each other and provided in a path connecting an RF signal line connected to an output section of the amplifier circuit and ground; and a resonant circuit, at least a portion of which is connected in series to the plurality of clamp diodes.

2. The power amplifier according to claim 1, wherein the resonant circuit includes an inductor and a capacitor connected in parallel with each other.

3. The power amplifier according to claim 1 or 2, wherein the resonant circuit is connected between two adjacent clamp diodes among the plurality of clamp diodes.

4. The power amplifier according to any one of claims 1 to 3, wherein the resonant circuit includes at least one of a variable inductor and a variable capacitor.

5. A power amplifier according to any one of claims 1 to 4, wherein a transmission filter having a pass band including the transmission band of a first communication band is connected to the output section of the amplifier circuit, and the resonant circuit is a band-elimination filter having a stop band including the pass band of the transmission filter.

6. A power amplifier according to any one of claims 1 to 5, wherein the resonant circuit includes a plurality of circuit elements, and at least one of the plurality of circuit elements is provided inside a semiconductor component including the amplifier circuit.

7. The power amplifier according to claim 6, wherein the plurality of circuit elements include a capacitor provided inside the semiconductor component, and an inductor configured as an SMD component separate from the semiconductor component.

8. The power amplifier according to claim 6 or 7, wherein the plurality of clamp diodes are provided inside the semiconductor component.

9. A high frequency module comprising: a power amplifier according to any one of claims 1 to 8; and a transmission filter connected to an output section of the power amplifier and having a pass band including the transmission band of a first communication band.

10. A communication device comprising: the high frequency module according to claim 9; and a signal processing circuit connected to the high frequency module for processing a high frequency signal.

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