Amplification circuit

Abstract

To provide an amplifier circuit capable of temperature compensation using a small circuit.SOLUTION: An amplifier circuit includes a first amplifier 12 that amplifies a high frequency signal, and a load circuit that changes the load impedance of the first amplifier without being controlled by an external circuit such that the saturated power at a first temperature is higher than the saturated power at a second temperature lower than the first temperature, and the efficiency at the first temperature is lower than the efficiency at the second temperature.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an amplifier circuit, for example, an amplifier circuit having a load circuit. [Background technology]

[0002] Power amplifier circuits are used in mobile communication base stations. Amplifier circuits capable of changing the load impedance of the amplifier are known (for example, Patent Documents 1 and 2). It is also known to provide a temperature compensation circuit to compensate for temperature changes in the characteristics of the amplifier circuit (for example, Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2017-529747 [Patent Document 2] International Publication No. 2006 / 006244 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-37448 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-269351 Summary of the Invention [Problem to be solved by the invention]

[0004] When the temperature changes, the temperature characteristics of the amplifier change. As in Patent Documents 3 and 4, providing a temperature compensation circuit results in an increase in circuit size. Temperature compensation can be achieved by changing the load impedance, but controlling the load impedance from an external circuit results in an increase in circuit size.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide an amplifier circuit that is capable of temperature compensation using a small circuit. [Means for solving the problem]

[0006] One embodiment of the present disclosure is an amplifier circuit comprising: a first amplifier that amplifies a high-frequency signal; and a load circuit in which the load impedance of the first amplifier is changed without being controlled by an external circuit so that the saturation power at a first temperature is higher than the saturation power at a second temperature lower than the first temperature, and the efficiency at the first temperature is lower than the efficiency at the second temperature. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an amplifier circuit that uses a small circuit and is capable of temperature compensation. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of an amplifier circuit according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing input / output characteristics when the temperature in the post-stage amplifier circuit is changed. [Figure 3] FIG. 3 is a diagram showing input / output characteristics in the pre-amplifier circuit. [Figure 4] FIG. 4 is a Smith chart showing the load impedance in the pre-amplifier circuit. [Figure 5] FIG. 5 is a circuit diagram of a pre-amplifier circuit according to the first embodiment. [Figure 6] FIG. 6 is a circuit diagram of a pre-amplifier circuit according to a first modification of the first embodiment. [Figure 7] FIG. 7 is a plan view of a pre-amplifier circuit according to a first modification of the first embodiment. [Figure 8] FIG. 8 is a diagram illustrating the load impedance of the output load circuit in the first modification of the first embodiment. [Figure 9] FIG. 9 is a circuit diagram of a pre-amplifier circuit according to a second modification of the first embodiment. [Figure 10] FIG. 10 is a plan view of a pre-amplifier circuit according to a second modification of the first embodiment. [Figure 11] FIG. 11 is a diagram illustrating the load impedance of the output load circuit in the second modification of the first embodiment. [Figure 12] FIG. 12 is a circuit diagram of a pre-amplifier circuit according to a third modification of the first embodiment. [Figure 13] FIG. 13 is a circuit diagram of a pre-amplifier circuit according to a fourth modification of the first embodiment. [Figure 14] FIG. 14 is a circuit diagram of a pre-amplifier circuit according to a fifth modification of the first embodiment. [Figure 15] FIG. 15 is a circuit diagram of a pre-amplifier circuit according to a sixth modification of the first embodiment. [Figure 16] FIG. 16 is a circuit diagram of a pre-amplifier circuit according to a seventh modification of the first embodiment. [Figure 17] FIG. 17 is a circuit diagram of a pre-amplifier circuit according to Modification 8 of the first embodiment. [Figure 18] FIG. 18 is a circuit diagram of a pre-amplifier circuit according to a ninth modification of the first embodiment. [Figure 19] FIG. 19 is a circuit diagram of a pre-amplifier circuit in a tenth modification of the first embodiment. [Figure 20] FIG. 20 is a circuit diagram of a pre-amplifier circuit according to an eleventh modification of the first embodiment. [Figure 21] FIG. 21 is a circuit diagram of a pre-amplifier circuit according to the second embodiment. [Figure 22] FIG. 22 is a diagram illustrating the load impedance of the output load circuit in the second embodiment. [Figure 23] FIG. 23 is a block diagram of an amplifier circuit according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. (1) One embodiment of the present disclosure is an amplifier circuit including a first amplifier that amplifies a high-frequency signal, and a load circuit that changes the load impedance of the first amplifier without being controlled by an external circuit so that the saturation power at a first temperature is higher than the saturation power at a second temperature lower than the first temperature, and the efficiency at the first temperature is lower than the efficiency at the second temperature. This makes it possible to provide an amplifier circuit that can be temperature compensated using a small circuit. (2) The load circuit preferably includes a reactance element and a resistance element having a first resistance value at the first temperature and a second resistance value at the second temperature that are different from each other. (3) It is preferable that the reactance element is connected in series between the first amplifier and the output terminal, and the resistance element is connected in parallel to the reactance element between the first amplifier and the output terminal. (4) It is preferable that the load impedance is inductive, and that the resistance component of the load impedance at the first temperature is higher than the resistance component of the load impedance at the second temperature. (5) It is preferable that the reactance element is a capacitive element, and that the first resistance value is lower than the second resistance value. (6) The resistive element is preferably a thermistor. (7) It is preferable that the device further comprises a transistor having a first terminal connected to a first end of the reactance element and a second terminal connected to a second end of the reactance element, the transistor being the resistance element, and an adjustment circuit that makes the voltage of the control terminal of the transistor different between the first temperature and the second temperature. (8) It is preferable to include a diode that is the resistive element and is connected in parallel to the reactance element, and an adjustment circuit that changes the voltage difference across the diode between the first temperature and the second temperature. (9) The first amplifier is preferably a GaN HEMT. (10) It is preferable to include a second amplifier for amplifying the output signal of the first amplifier.

[0010] [Details of the embodiments of the present disclosure] Specific examples of amplifier circuits according to embodiments of the present disclosure will be described below with reference to the drawings. Note that the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0011] [Example 1] A two-stage amplifier circuit will be described as a first embodiment. FIG. 1 is a block diagram of the amplifier circuit according to the first embodiment. As shown in FIG. 1, the amplifier circuit 100 includes a pre-stage amplifier circuit 10 and a post-stage amplifier circuit 20. The pre-stage amplifier circuit 10 includes an amplifier 12, an input matching circuit 14, an output load circuit 16, and a bias circuit 18. The post-stage amplifier circuit 20 includes an amplifier 22, an input matching circuit 24, an output load circuit 26, and a bias circuit 28. The pre-stage amplifier circuit 10 amplifies a high-frequency signal input to an input terminal Tin and outputs the signal to a terminal Tm. The post-stage amplifier circuit 20 amplifies a high-frequency signal amplified by the pre-stage amplifier circuit 10 and input to a terminal Tm and outputs the signal to an output terminal Tout. The amplifier circuit 100 is a power amplifier circuit used in mobile communication base stations such as 5G (5th Generation Mobile Communication Systems).

[0012] The amplifiers 12 and 22 are transistors such as field effect transistors (FETs), for example, GaN HEMTs (Gallium Nitride High Electron Mobility Transistors) or LDMOSs (Laterally Diffused Metal Oxide Semiconductors). The GaN HEMT is a HEMT having a GaN channel layer and an AlGaN barrier layer. The input terminals of the amplifiers 12 and 22 are, for example, the gates of the FETs, and the output terminals are, for example, the drains of the FETs.

[0013] The input matching circuit 14 matches the input impedance of the input terminal Tin to the input impedance of the amplifier 12. The output load circuit 16 is a circuit that sets the load impedance of the amplifier 12. The load impedance is the impedance when the output load circuit 16 is viewed from the output terminal (drain) of the amplifier 12. In the first embodiment, the load impedance of the output load circuit 16 changes with temperature. The bias circuit 18 supplies a bias voltage Vdd to the output terminal of the amplifier 12. The input matching circuit 24 matches the impedance of the output load circuit 16 to the input impedance of the amplifier 22. The output load circuit 26 is a circuit that sets the load impedance of the amplifier 22. In the first embodiment, the load impedance set by the output load circuit 26 is fixed regardless of temperature. The bias circuit 28 supplies a bias voltage Vdd to the output terminal of the amplifier 12. The pre-stage amplifier circuit 10 and the post-stage amplifier circuit 20 may each include a bias circuit that supplies a bias voltage to the input terminal of the amplifier 12 and the input terminal of the amplifier 22.

[0014] [Comparative Example 1] As a comparative example 1, a problem that arises when the load impedance of the output load circuit 16 viewed from the output terminal of the amplifier 12 is fixed will be described using GaN HEMTs as the amplifiers 12 and 22. In a power amplifier circuit for a base station, the output load circuit of the post-stage amplifier circuit 20 26 The load impedance is set so as to increase the efficiency. The figure shows the characteristics of the post-stage amplifier circuit 20 at 3.5 GHz in an amplifier circuit with an output power of 300 W class. stomach.

[0015] Figure 2 shows the input / output characteristics of the post-stage amplifier circuit as the temperature changes. In Figure 2, the horizontal axis represents input power Pin, and the vertical axis represents output power Pout, power gain Gain, and power-added efficiency Eff. The temperatures are -20°C, 30°C, and 80°C. As shown in Figure 2, as the temperature increases, the output power Pout, power gain Gain, and power-added efficiency Eff decrease. This is because as the temperature increases, the electron velocity and mobility in a high electric field in the channel layer of the GaN HEMT decrease.

[0016] In a 300W-class amplifier circuit, when amplifying a signal with a peak-to-average power ratio (PAPR) of 10dB, the modulated wave output of the post-stage amplifier circuit 20 is 45dBm (approximately 30W) and the peak output is 55dBm (approximately 300W). At 80°C, when the output power Pout is 55dBm, the power gain Gain is approximately 9dBm. Therefore, the output signal (signal at terminal Tm) of the pre-stage amplifier circuit 10 should have a saturated power Psat of 46dBm and a modulated wave output of 36dBm. Similarly, at 30°C, when the output power Pout is 55dBm, the power gain Gain is approximately 11dBm, so the saturated power Psat and modulated wave output of the pre-stage amplifier circuit 10 should be 44dBm and 34dBm, respectively. At −20° C., when the output power Pout is 55 dBm, the power gain is approximately 13 dBm, so the saturated power Psat and modulated wave output of the pre-amplifier circuit 10 only need to be 42 dBm and 32 dBm, respectively.

[0017] FIG. 3 is a diagram showing input / output characteristics of the pre-stage amplifier circuit. In FIG. 3, the horizontal axis represents output power Pout, and the vertical axis represents power gain Gain and power-added efficiency Eff. The temperature is 30°C. The black circles represent input / output characteristics when the load impedance is set so that the saturated power Psat is high (this is called output matching). The white circles represent input / output characteristics when the load impedance of the output load circuit 16 is set so that the power-added efficiency Eff at the operating point of 32 dBm is high (this is called efficiency matching). As shown in FIG. 3, with output matching, the saturated power Psat is approximately 46 dBm, and the efficiency Eff at 32 dBm is approximately 11%. With efficiency matching, the saturated power Psat is approximately 44.5 dBm, and the efficiency Eff at 32 dBm is approximately 21%. Thus, with efficiency matching, the efficiency Eff of the pre-stage amplifier circuit 10 is high, but the saturated power Psat is low. With output matching, the saturated power Psat of the pre-stage amplifier circuit 10 is high, but the efficiency Eff is low.

[0018] At a temperature of 80°C, the saturated power Psat of the pre-stage amplifier circuit 10 is required to be 46 dBm. Therefore, the load impedance of the pre-stage amplifier circuit 10 is output-matched. However, at a temperature of 30°C, the output power Pout of the pre-stage amplifier circuit 10 only needs to be 44 dBm. However, when the output load circuit 16 is fixed as in Comparative Example 1, the load impedance of the output load circuit 16 is fixed to output matching. Therefore, when the operating point is 32 dBm, the efficiency Eff of the pre-stage amplifier circuit 10 is 11%. Thus, in Comparative Example 1, the load impedance of the output load circuit 16 is set to output matching, resulting in poor efficiency at low temperatures. Here, it is possible to increase the size of the amplifier 12 of the pre-stage amplifier circuit 10 so that the saturated power Psat is 46 dBm even when efficiency matching is used. However, this would result in an increase in the size of the pre-stage amplifier circuit 10.

[0019] FIG. 4 is a Smith chart showing the load impedance in the pre-stage amplifier circuit. In FIG. 4, the standard impedance is 50Ω. Impedance 50 is the load impedance from 3.4 GHz to 3.6 GHz when output matching is performed, and the saturated power Psat is 46 dBm. Curve 51 surrounding impedance 50 is the contour line of the saturated power Psat, and the saturated power Psat decreases by 0.5 dBm toward the outer curve. Impedance 52 is the load impedance from 3.4 GHz to 3.6 GHz when efficiency matching is performed, and the efficiency Eff is 30%. Impedance 52 The curve 53 surrounding this is a contour line of efficiency Eff, and the efficiency Eff decreases by 3% as you move toward the outer curve 53. Impedance 50 is approximately 0.4 + 0.24j (j is the imaginary unit). Impedance 52 is approximately 0.2 + 0.18j. As such, the reactance components of both impedances 50 and 52 are positive (inductive), and impedance 50 has a higher resistance component than 52. Impedance 50 has a smaller reactance component / resistance component than 52.

[0020] [Output Load Circuit of Example 1] In the output load circuit 16 of the front-stage amplifier circuit 10 of the first embodiment, the load impedance is near 50 at high temperatures (e.g., 80°C) and near 52 at low temperatures (e.g., 30°C) without being controlled by an external circuit. As a result, the saturated power Psat of the front-stage amplifier circuit 10 can be set to 46 dBm at 80°C, as shown in the output matching of FIG. 3. Meanwhile, at low temperatures, the saturated power Psat of the front-stage amplifier circuit 10 decreases, but the desired 44 dBm is still obtained, as shown in the efficiency matching of FIG. 3. Moreover, the efficiency at the operating point of 32 dBm can be set to 21%. This allows a 7 W reduction in power consumption.

[0021] Fig. 5 is a circuit diagram of the front-stage amplifier circuit in the first embodiment. An input matching circuit is not shown in Fig. 5. As shown in Fig. 5, amplifier 12 is FET Q1, and the source S of FET Q1 is connected to ground Gnd, the gate G is connected to input terminal Tin, and the drain D is connected to node N1. A bias circuit 18 is connected to node N1. Output load circuit 16 includes a reactance element 15 connected in series between nodes N1 and N2, and a resistance element 17 connected in parallel with reactance element 15 between nodes N1 and N2.

[0022] Reactance element 15 is an element whose impedance is primarily a reactance component, such as a capacitive element such as a capacitor or an inductive element such as an inductor. Resistance element 17 is an element whose impedance is primarily a resistive component. The reactance of reactance element 15 has low temperature dependency, while the resistance value of resistance element 17 has very high temperature dependency. For example, the temperature coefficient of the absolute value of the impedance of resistance element 17 is greater than the temperature coefficient of the absolute value of the impedance of reactance element 15 at the operating frequency, by more than 10 times. The load impedance can be changed with temperature by changing the resistance value of resistance element 17 with temperature. To change the load impedance with temperature, the reactance of reactance element 15 can be changed with temperature. However, it is simpler to change the resistance value of resistance element 17 with temperature than to change the reactance of reactance element 15 with temperature.

[0023] A specific example of the output load circuit 16 in a modification of the first embodiment will be described below.

[0024] [Modification 1 of Example 1] FIG. 6 is a circuit diagram of a front-stage amplifier circuit in Modification 1 of Example 1. In FIG. 6, the input matching circuit is omitted. As shown in FIG. 6, the bias circuit 18 includes an inductor L1 and a capacitor C1. The inductor L1 is connected between nodes N1 and Nd. The capacitor C1 is connected between node Nd and ground Gnd. A drain bias voltage Vdd is applied to node N1. The inductor L1 is a choke coil for cutting high-frequency signals and is used for matching. The capacitor C1 is a bias capacitor.

[0025] The output load circuit 16 includes capacitors C2 and C3 and a thermistor RTH1. The capacitor C2 is a reactance element 15 connected between nodes N1 and N2. The capacitor C3 is connected between node N2 and terminal Tm. The thermistor RTH1 is a resistance element 17 connected in parallel to the capacitor C2 between nodes N1 and N2. The capacitor C2 is used for matching, and the capacitor C3 is used for DC blocking. The thermistor RTH1 has a negative temperature coefficient (NTC), and its resistance decreases as the temperature increases.

[0026] FIG. 7 is a plan view of a front-stage amplifier circuit in Modification 1 of Example 1. In FIG. 7, the input matching circuit 14 and the rear-stage amplifier circuit 20 are omitted. The conductor pattern 32 is indicated by hatching. As shown in FIG. 7, the conductor pattern 32 is provided on a dielectric substrate 30. The dielectric substrate 30 is, for example, a resin substrate such as FR-4 or a ceramic substrate. The conductor pattern 32 is, for example, a metal layer such as Cu or Au. A package which is FET Q1, chip capacitors which are capacitors C1 to C3, a chip inductor which is inductor L1, and a thermistor RTH1 are mounted on the dielectric substrate 30. The conductor pattern 32 corresponds to ground Gnd, input terminal Tin, terminal Tm, and nodes N1, N2, and Nd.

[0027] The load impedance when looking at the terminal Tm from the drain D of the FET Q1 was simulated. The simulation conditions are as follows: Capacitor C1: 4pF Capacitor C2: 0.2 pF Capacitor C3: 4pF Inductor L1: 1.2nH Thermistor RTH1: 220Ω at 25℃, 20Ω at 100℃ FETQ1: GaN HEMT

[0028] Fig. 8 is a diagram showing the load impedance of the output load circuit in Modification 1 of Example 1. As shown in Fig. 8, impedance 54 is the load impedance at a temperature of 100°C, and impedance 56 is the load impedance at a temperature of 25°C. The frequency is set to 3.4 GHz to 3.6 GHz. At 100°C, the load impedance becomes impedance 54, which is close to the output matching impedance 50, and at 25°C, it becomes impedance 56, which is close to the efficiency matching impedance 52.

[0029] [Modification 2 of Example 1] 9 is a circuit diagram of a pre-amplifier circuit in Modification 2 of Example 1. As shown in FIG. 9, the output load circuit 16 includes a transistor TR1, an inductor L2, resistors R1 and R2, capacitors C2 and C3, and a thermistor RTH1. The transistor TR1 is a resistive element 17 and is an NPN bipolar transistor. The emitter of the transistor TR1 E is connected to node N2, and the collector C is connected to node N1, and base B is connected to node N1 via thermistor RTH1 and resistor R1. Adjustment circuit 19 has thermistor RTH1 and resistor R1 and adjusts the base voltage of transistor TR1. The node between thermistor RTH1 and resistor R1 is N3, and the node between thermistor RTH1 and base B is N4. Node N2 is connected to ground via inductor L2 and resistor R2. The node between inductor L2 and resistor R2 is N5. Inductor L2 and resistor R2 form a bias circuit that supplies the emitter bias voltage of transistor TR1, resistor R2 is a bias resistor, and inductor L2 is a choke coil for cutting high-frequency signals.

[0030] The collector bias voltage of transistor TR1 is the voltage at node N1 and is higher than the emitter bias voltage (the voltage at node N2). When the temperature is high, the resistance value of thermistor RTH1 decreases, and the base voltage of transistor TR1 increases. Therefore, the resistance between the emitter and collector of transistor TR1 decreases. When the temperature is low, the resistance value of thermistor RTH1 increases, and the base voltage of transistor TR1 decreases. Therefore, the resistance between the emitter and collector of transistor TR1 increases. The other configurations are the same as those in FIG. 6 of Variation 1 of Example 1, and therefore description thereof will be omitted.

[0031] 10 is a plan view of a pre-stage amplifier circuit in Modification 2 of Example 1. As shown in FIG. 10, a package including FET Q1 and transistor TR1, chip capacitors including capacitors C1 to C3, chip inductors including inductors L1 and L2, chip resistors including resistors R1 and R2, and a thermistor RTH1 are mounted on a dielectric substrate 30. Conductor patterns 32 correspond to ground Gnd, input terminal Tin, terminal Tm, and nodes N1 to N5 and Nd. The other configurations are the same as those in FIG. 7 of Modification 1 of Example 1, and therefore will not be described again.

[0032] The load impedance when looking at the terminal Tm from the drain D of the FET Q1 was simulated. The simulation conditions are as follows: Capacitor C1: 4pF Capacitor C2: 0.35pF Capacitor C3: 4pF Inductor L1: 1.1nH Inductor L2: 12nH Resistor R1: 0Ω Resistance R2: 33kΩ Thermistor RTH1: 220Ω at 25℃, 20Ω at 100℃ Transistor TR1: NPN transistor FETQ1: GaN HEMT

[0033] FIG. 11 is a diagram showing the load impedance of the output load circuit in Modification 2 of Example 1. As shown in FIG. 11, impedance 54 is the load impedance at a temperature of 100°C, and impedance 56 is the load impedance at a temperature of 25°C. The frequency is set to 3.4 GHz to 3.6 GHz. At 100°C, the load impedance is impedance 54, which is close to the output matching impedance 50, and at 25°C, the load impedance is impedance 56, which is close to the efficiency matching impedance 52. As described above, Modification 2 of Example 1 uses a transistor as the resistance element 17. This allows for a larger change in the resistance value of the resistance element 17 due to a change in temperature compared to Modification 1 of Example 1, which uses a thermistor RTH1 as the resistance element 17. Furthermore, the accuracy of the change in the resistance value of the resistance element 17 due to a change in temperature can be improved compared to Modification 3 of Example 1, which uses a diode D1 as the resistance element 17, which will be described later.

[0034] [Modification 3 of Example 1] FIG. 12 is a circuit diagram of a pre-amplifier circuit according to a third modification of the first embodiment. As shown in FIG. 12, an output load circuit 16 includes a diode D1, an inductor L2, a resistor R2, capacitors C2 and C3, and a thermistor RTH1. The diode D1 is a resistive element 17. The anode of the diode D1 is connected to a node N1, and the cathode is connected to a node N2. The node N2 is connected to ground via the inductor L2, the resistor R2, and the thermistor RTH1. The adjustment circuit 19 includes a resistor R2 and thermistor RTH1 and adjusts the voltage difference across the diode D1. When the temperature is high, the resistance of the thermistor RTH1 decreases, increasing the voltage difference between the nodes N1 and N2. The diode D1 is forward-connected, and as the voltage difference between the nodes N1 and N2 increases, the current flowing through the diode D1 increases rapidly. This decreases the resistance of the diode D1. When the temperature is low, the resistance value of the thermistor RTH1 increases, and the voltage difference between the nodes N1 and N2 decreases. This increases the resistance value of the diode D1. Therefore, the diode D1 can be used as the resistance element 17. By using the diode D1 as the resistance element 17, the resistance element 17 can be realized at lower cost than in Modification 2 of Example 1, which uses a transistor for the resistance element 17. Furthermore, the change in the resistance value of the resistance element 17 due to temperature changes can be made larger than in Modification 1 of Example 1, which uses the thermistor RTH1 for the resistance element 17. The other configurations are the same as those in FIG. 9 of Modification 2 of Example 1, and therefore description thereof will be omitted.

[0035] [Modification 4 of Example 1] FIG. 13 is a circuit diagram of a front-stage amplifier circuit in Modification 4 of Example 1. As shown in FIG. 13, an output load circuit 16 includes diodes D1, DX1 to DX3, an inductor L2, a resistor R2, and capacitors C2 and C3. In Modification 4 of Example 1, the thermistor RTH1 of Modification 3 of Example 1 is replaced with multiple diodes DX1 to DX3. An adjustment circuit 19 includes a resistor R2 and diodes DX1 to DX3. The diodes DX1 to DX3 are connected in series in the forward direction. As the temperature increases, the forward current of the diodes DX1 to DX3 increases rapidly, and the resistance values of the diodes DX1 to DX3 decrease. As the temperature decreases, the forward current of the diodes DX1 to DX3 decreases, and the resistance values of the diodes DX1 to DX3 increase. Therefore, the diodes DX1 to DX3 operate in the same manner as the thermistor RTH1 in Modification 3 of Example 1. This can be made less expensive than Modification 3 of Example 1, which uses the thermistor RTH1. The other configurations are the same as those of the third modification of the first embodiment shown in FIG. 12, and therefore the description thereof will be omitted.

[0036] [Modification 5 of Example 1] 14 is a circuit diagram of a pre-amplifier circuit in Modification 5 of Example 1. As shown in FIG. 14, the output load circuit 16 includes a transistor TR1, an inductor L2, resistors R2 and R3, capacitors C2 and C3, and a thermistor RTH1. The transistor TR1 is a resistive element 17, and is a PNP transistor. 。 Transistor TR1 emitter E is connected to node N1, the collector C is connected to node N2, and the base B is connected to ground via resistor R3 and thermistor RTH1. The adjustment circuit 19 has resistor R3 and thermistor RTH1 and adjusts the base voltage of transistor TR1. As the temperature rises, the resistance value of thermistor RTH1 decreases, and the base voltage of transistor TR1 decreases. This reduces the resistance value between the emitter and collector of transistor TR1. As the temperature drops, the resistance value of thermistor RTH1 increases, and the base voltage of transistor TR1 decreases. highThis increases the resistance value between the emitter and collector of the transistor TR1. Therefore, the transistor TR1 can be used as the resistance element 17. The other configurations are the same as those in FIG. 10 of the second modification of the first embodiment, and therefore a description thereof will be omitted.

[0037] [Modification 6 of Example 1] 15 is a circuit diagram of a front-stage amplifier circuit in Modification 6 of Example 1. As shown in FIG. 15, an output load circuit 16 includes a transistor TR1, diodes DX1 to DX3, an inductor L2, resistors R2 and R3, and capacitors C2 and C3. In Modification 6 of Example 1, the thermistor RTH1 of Modification 5 of Example 1 is replaced with a plurality of diodes DX1 to DX3 connected in the forward direction. An adjustment circuit 19 includes a resistor R3 and diodes DX1 to DX3. The other configurations are the same as those in FIG. 14 of Modification 5 of Example 1, and therefore description thereof will be omitted.

[0038] [Seventh Modification of the First Embodiment] 16 is a circuit diagram of a pre-amplifier circuit in Modification 7 of Example 1. As shown in FIG. 16, the output load circuit 16 includes a transistor TR1, an inductor L2, resistors R1 to R3, capacitors C2 and C3, and a thermistor RTH1. The transistor TR1 is a resistive element 17 and is a PMOS (Metal Oxide Semiconductor) transistor. The source of the transistor TR1 S is connected to node N1, the drain D is connected to node N2, and the gate Gis connected to node N6. A resistor R1 is connected between nodes N1 and N6. Node N6 is connected to ground via resistor R3 and thermistor RTH1. An adjustment circuit 19 includes resistors R1, R3, and thermistor RTH1, and adjusts the gate voltage of transistor TR1. As the temperature increases, the resistance of thermistor RTH1 decreases, and the gate voltage of transistor TR1 decreases. This decreases the source-drain resistance of transistor TR1. As the temperature decreases, the resistance of thermistor RTH1 increases, and the gate voltage of transistor TR1 increases. This increases the source-drain resistance of transistor TR1. Therefore, transistor TR1 can be used as resistor element 17. The other configurations are the same as those in FIG. 9 of Modification 2 of Example 1, and therefore a description thereof will be omitted.

[0039] [Variation 8 of Example 1] 17 is a circuit diagram of a front-stage amplifier circuit in Modification 8 of Example 1. As shown in FIG. 17, an output load circuit 16 includes a transistor TR1, diodes DX1 to DX3, an inductor L2, resistors R1 to R3, and capacitors C2 and C3. In Modification 8 of Example 1, the thermistor RTH1 of Modification 7 of Example 1 is replaced with a plurality of diodes DX1 to DX3 connected in the forward direction. An adjustment circuit 19 includes resistors R1 and R3 and diodes DX1 to DX3. The other configurations are the same as those in FIG. 16 of Modification 7 of Example 1, and therefore description thereof will be omitted.

[0040] [Modification 9 of Example 1] 18 is a circuit diagram of a pre-amplifier circuit in a ninth modification of the first embodiment. As shown in FIG. 18, an output load circuit 16 includes a transistor TR1, diodes DX1 to DX3, an inductor L2, resistors R1 and R2, and capacitors C2 and C3. In the ninth modification of the first embodiment, the thermistor RTH1 in the first modification of the first embodiment is replaced with a plurality of diodes DX1 to DX3 connected in the forward direction. An adjustment circuit 19 includes a resistor R1 and Diodes DX1 to DX3 The other configurations are the same as those of the first modification of the first embodiment shown in FIG. 9, and therefore the description thereof will be omitted. [Modification 10 of Example 1] 19 is a circuit diagram of a pre-amplifier circuit in Modification 10 of Example 1. As shown in FIG. 19, an output load circuit 16 includes a transistor TR1, an inductor L2, resistors R1 to R3, capacitors C2 and C3, and a thermistor RTH1. The transistor TR1 is a resistive element 17 and is an NMOS (Metal Oxide Semiconductor) transistor. The source of the transistor TR1 S is connected to node N2, the drain D is connected to node N1, and the gate G is connected to node N6. Resistor R1 and thermistor RTH1 are connected between nodes N1 and N6. Resistor R3 is connected between nodes N2 and N6. Adjustment circuit 19 has resistors R1, R3, and thermistor RTH1 and adjusts the gate voltage of transistor TR1. As the temperature increases, the resistance of thermistor RTH1 decreases, and the gate voltage of transistor TR1 increases. This reduces the source-drain resistance of transistor TR1. As the temperature decreases, the resistance of thermistor RTH1 increases, and the gate voltage of transistor TR1 decreases. This increases the source-drain resistance of transistor TR1. Therefore, transistor TR1 can be used as resistance element 17. The other configurations are the same as those in FIG. 9 of Modification 2 of Example 1, and therefore description thereof will be omitted.

[0041] [Modification 11 of Example 1] 20 is a circuit diagram of a front-stage amplifier circuit in an eleventh modification of the first embodiment. As shown in FIG. 20, an output load circuit 16 includes a transistor TR1, diodes DX1 to DX3, an inductor L2, resistors R1 to R3, and capacitors C2 and C3. In the eleventh modification of the first embodiment, the thermistor RTH1 in the tenth modification of the first embodiment is replaced with a plurality of diodes DX1 to DX3 connected in the forward direction. An adjustment circuit 19 includes resistors R1 and R3 and diodes DX1 to DX3. The other configurations are the same as those in FIG. 19 of the tenth modification of the first embodiment, and therefore description thereof will be omitted.

[0042] In the third to eleventh modifications of the first embodiment, similarly to the first embodiment and its first and second modifications, the resistance component of the load impedance is high at low temperatures, and the load impedance is close to efficiency matching. As the temperature rises, the resistance component of the load impedance decreases, and the load impedance is close to output matching. 。 Therefore, the efficiency at room temperature can be increased.

[0043] [Example 2] The second embodiment is an example in which the resistance component of the load impedance during output matching is higher than the resistance component of the load impedance during efficiency matching. Fig. 21 is a circuit diagram of a front-stage amplifier circuit in the second embodiment. As shown in Fig. 21, the output load circuit 16 ,tree The capacitors C2 to C4 and the thermistor RTH1 are provided. The capacitor C2 is a reactance element 15. A capacitor C2 A thermistor RTH1 and a capacitor C4 are connected in parallel to the resistor RTH1. The thermistor RTH1 is a resistive element 17, has a PTC (Positive Temperature Coefficient), and has a resistance value that increases as the temperature increases. The other configurations are the same as those in FIG. 6 of the first modification of the first embodiment, and therefore a description thereof will be omitted.

[0044] The load impedance when looking at the terminal Tm from the drain D of the FET Q1 was simulated. The simulation conditions are as follows: Capacitor C1: 4pF Capacitor C2: 0.5 pF Capacitor C3: 4pF Capacitor C4: 2.2 pF Inductor L1: 1nH Thermistor RTH1: 6Ω at 25℃, 1kΩ at 100℃ FETQ1: GaN HEMT

[0045] Fig. 22 is a diagram showing the load impedance of the output load circuit in Example 2. As shown in Fig. 22, the resistance component of output matching impedance 50 is lower than that of efficiency matching impedance 52, and the reactance component is positive (inductive). Impedance 54 at a temperature of 100°C is close to impedance 50, and impedance 56 at a temperature of 25°C is close to impedance 52.

[0046] As in the second embodiment, even if the output matching impedance 50 and the efficiency matching impedance 52 are different from those in the first embodiment and its modified examples, by using the output load circuit 16, it is possible to make the load impedance at high temperatures approach the impedance 50 and the load impedance at low temperatures approach the impedance 52. Although the thermistor RTH1 has been described as an example of the resistive element 17, the resistive element 17 may also be a diode or a transistor.

[0047] [Example 3] 23 is a block diagram of an amplifier circuit according to a third embodiment. A bias circuit is not shown. As shown in FIG. 23, a plurality of pre-stage amplifier circuits 10 are provided. As in the first embodiment and its modified examples, it is sufficient that the load impedance of at least one of the output load circuits 16 of the plurality of pre-stage amplifier circuits 10 changes with temperature.

[0048] According to the first to third embodiments and their modifications, the output load circuit 16 (load circuit) in the pre-stage amplifier circuit 10 changes the load impedance of the amplifier (first amplifier) without being controlled by an external circuit so that the saturation power Psat at a high temperature (first temperature) is higher than the saturation power Psat at a low temperature (second temperature) and the efficiency Eff at a high temperature is lower than the efficiency Eff at a low temperature. This allows the saturation power Psat to be increased at high temperatures where high saturation power Psat is required, and the efficiency Eff to be increased at low temperatures where the saturation power Psat is sufficient. Therefore, the efficiency at low temperatures is increased, and power consumption can be reduced.

[0049] The high and low temperatures are, for example, 80°C and 30°C, respectively, and the difference between the high and low temperatures is, for example, 30°C or more, or 50°C or more. The difference in saturated power Psat between the high and low temperatures is, for example, 0.5 dBm or more, or 1 dBm or more. Furthermore, the difference in operating point efficiency Eff between the high and low temperatures is, for example, 5% or more, or 10% or more.

[0050] The output load circuit 16 includes a reactance element 15 and a resistance element 17 having a first resistance value at high temperatures and a second resistance value at low temperatures that are different from each other. It is easier to change the resistance value of the resistance element 17 with temperature than to change the reactance of the reactance element 15 with temperature. Therefore, it is easier to change the load impedance with temperature.

[0051] Reactance element 15 is connected in series between amplifier 12 and terminal Tm (an output terminal from which amplifier 12 outputs the amplified high-frequency signal). Resistance element 17 is connected in parallel to reactance element 15 between amplifier 12 and terminal Tm. This allows the load impedance to be changed.

[0052] 8 and 11 of the first embodiment and its modifications, the load impedances 54 and 56 are inductive, and the resistance component of the load impedance 54 at high temperature is higher than the resistance component of the load impedance 56 at low temperature. Therefore, by using the reactance element 15 and the resistance element 17, the load impedance 54 at high temperature is made closer to the output matching impedance 50, and the load impedance at low temperature is made 56 to the impedance of 52 for efficient matching. Get closer It is possible.

[0053] The reactance element 15 is a capacitive element, and the first resistance value of the resistance element 17 at high temperature is lower than the second resistance value at low temperature. This makes the load impedance 54 at high temperature closer to the output matching impedance 50, and the load impedance at low temperature 56 to the impedance of 52 for efficient matching. Get closer It is possible.

[0054] By using the thermistor RTH1 as the resistance element 17, the resistance value of the resistance element 17 can be made to vary depending on the temperature. 17 By using the thermistor RTH1, the accuracy of the changing resistance value can be improved, and the accuracy of the changing load impedance can be improved, thereby improving the characteristics of the amplifier circuit.

[0055] The resistor element 17 is a transistor TR1 having a first terminal connected to the first end of the reactance element 15 and a second terminal connected to the second end of the reactance element 15, and the adjustment circuit 19 causes the voltage of the control terminal of the transistor to differ between high and low temperatures. This allows the resistance value of the resistor element 17 to change more significantly when the temperature changes compared to when a thermistor RTH1 is used as the resistor element 17. Furthermore, the resistance value can be adjusted more precisely compared to when a diode D1 is used as the resistor element 17. When the transistor TR1 is a bipolar transistor, the first terminal is one of the emitter and collector, the second terminal is the other of the emitter and collector, and the control terminal is the base. When the transistor TR1 is an FET, the first terminal is one of the source and drain, the second terminal is the other of the source and drain, and the control terminal is the gate.

[0056] Resistance element 17 is a diode D1 connected in parallel to reactance element 15 between nodes N1 and N2, and adjustment circuit 19 changes the voltage difference across diode D1 at high and low temperatures. This allows the resistance value of resistance element 17 to change more when the temperature changes, compared to when a thermistor RTH1 is used as resistance element 17. Furthermore, resistance element 17 can be made less expensive than when a transistor TR1 is used as resistance element 17.

[0057] When the amplifiers 12 and 22 are GaN HEMTs, the output matching impedance 50 and the efficiency matching impedance 52 are as shown in Fig. 4. Therefore, it is preferable to provide the output load circuit 16.

[0058] A final-stage rear-stage amplifier circuit 20 is provided downstream of the pre-stage amplifier circuit 10. That is, an amplifier 22 (second amplifier) amplifies the output signal of the amplifier 12. In this case, as the temperature rises, the saturation power Psat of the final-stage rear-stage amplifier circuit 20 decreases, and it is therefore necessary to increase the saturation power Psat of the pre-stage amplifier circuit 10. On the other hand, at low temperatures, it is not necessary to increase the saturation power Psat of the pre-stage amplifier circuit 10. Therefore, by providing an output load circuit 16, it is possible to improve efficiency at low temperatures.

[0059] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, not by the meaning described above, and is intended to include all modifications within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0060] 10 Pre-amplifier Circuit 12 Amplifier (first amplifier) 14 Input matching circuit 15 Reactance element 16 Output load circuit (load circuit) 17 Resistive element 18 Bias circuit 19 Adjustment circuit 20 Post-amplifier circuit 22 Amplifier (second amplifier) 24 Input matching circuit 26 Output load circuit 28 Bias Circuit 30 Dielectric substrate 32 Conductor pattern 50, 52, 54, 56 Impedance 51, 53 curve

Claims

1. a first amplifier for amplifying a high frequency signal; a load circuit that changes the load impedance of the first amplifier without being controlled by an external circuit; Equipped with the load circuit includes a reactance element and a resistance element having a first resistance value at a first temperature and a second resistance value at a second temperature lower than the first temperature, the reactance element is connected in series between the first amplifier and an output terminal, and the resistance element is connected in parallel with the reactance element between the first amplifier and the output terminal; a resistance value of the resistive element changes between the first resistance value and the second resistance value, thereby changing the load impedance of the first amplifier so that a saturation power at the first temperature is higher than a saturation power at the second temperature and an efficiency at the first temperature is lower than an efficiency at the second temperature; a transistor having a first terminal connected to a first end of the reactance element and a second terminal connected to a second end of the reactance element, the transistor being the resistance element; an adjustment circuit that makes the voltage of the control terminal of the transistor different between the first temperature and the second temperature.

2. A first amplifier that amplifies a high-frequency signal; a load circuit that changes the load impedance of the first amplifier without being controlled by an external circuit; Equipped with the load circuit includes a reactance element and a resistance element having a first resistance value at a first temperature and a second resistance value at a second temperature lower than the first temperature, the reactance element is connected in series between the first amplifier and an output terminal, and the resistance element is connected in parallel with the reactance element between the first amplifier and the output terminal; a resistance value of the resistive element changes between the first resistance value and the second resistance value, thereby changing the load impedance of the first amplifier so that a saturation power at the first temperature is higher than a saturation power at the second temperature and an efficiency at the first temperature is lower than an efficiency at the second temperature; a diode connected in parallel to the reactance element and serving as the resistance element; an adjustment circuit that changes a voltage difference across the diode at the first temperature and the second temperature; An amplifier circuit comprising:

3. 3. The amplifier circuit according to claim 1, wherein the load impedance is inductive, and a resistance component of the load impedance at the first temperature is higher than a resistance component of the load impedance at the second temperature.

4. the reactance element is a capacitive element, 4. The amplifier circuit according to claim 3, wherein the first resistance value is lower than the second resistance value.

5. 5. The amplifier circuit according to claim 1, wherein the first amplifier is a GaN HEMT.

6. 6. The amplifier circuit according to claim 1, further comprising a second amplifier that amplifies the output signal of the first amplifier.

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