Gate shadow amplification circuit

Abstract

A gate-cathode amplifier circuit is provided that suppresses gain reduction even when the supply voltage is reduced. A high-frequency signal is input to a first transistor. At least one second transistor is connected to the gate-cathode of the first transistor. A bias circuit supplies bias voltage to at least one second transistor. A power supply line applies a variable supply voltage to the gate-cathode connection circuit containing the first transistor and at least one second transistor. The bias circuit includes a resistor divider circuit, a bias voltage source, and at least one first diode. The resistor divider circuit is connected between the power supply line and a reference potential, and has at least one voltage division point corresponding to at least one second transistor, supplying bias voltage to the corresponding second transistor based on the voltage of the at least one voltage division point. The bias voltage source generates a reference voltage, which becomes the basis for the bias voltage supplied to at least one second transistor.

Description

Technical Field

[0001] This invention relates to cascode amplifier circuits. Background Technology

[0002] A gate-cathode amplifier circuit using an envelope tracking method that modulates the power supply voltage based on an input signal is known (Patent Document 1). In the gate-cathode amplifier circuit disclosed in Patent Document 1, a bias voltage is generated by dividing the power supply voltage modulated based on the input signal using a resistor divider circuit. This bias voltage is supplied to the gate-cathode transistor.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Publication No. 2016-530845 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] When the power supply voltage is reduced, the bias voltage generated based on the reduced power supply voltage also decreases. If the bias voltage of the gate-cathode transistor decreases excessively, the gate-cathode transistor becomes off, resulting in a decrease in the gain of the gate-cathode amplifier circuit. The object of the present invention is to provide a gate-cathode amplifier circuit that suppresses the decrease in gain even when the power supply voltage is reduced.

[0008] Solution for solving the problem

[0009] According to one aspect of the present invention, a gate-cathode amplifier circuit is provided, comprising: a first transistor for receiving a high-frequency signal input; at least one second transistor connected to the gate-cathode of the first transistor; a bias circuit for supplying a bias voltage to the at least one second transistor; and a power supply wiring that applies a variable power supply voltage to a gate-cathode connection circuit including the first transistor and the at least one second transistor, the bias circuit comprising: a resistor divider circuit connected between the power supply wiring and a reference potential, having at least one voltage divider point corresponding to the at least one second transistor, and supplying a bias voltage to the corresponding second transistor based on the voltage of the at least one voltage divider point; a bias voltage source for generating a reference voltage, which forms the basis for the bias voltage supplied to the at least one second transistor; and at least one first diode connected between the output node of the bias voltage source and the at least one voltage divider point in a positive direction from the output node of the bias voltage source toward the at least one voltage divider point.

[0010] The effects of the invention

[0011] Even if the power supply voltage applied to the power supply wiring decreases, a reference voltage is applied from the bias voltage source to the voltage divider point of the resistor voltage divider circuit via the first diode. Therefore, even if the power supply voltage decreases, excessive decrease in the voltage at the voltage divider point is suppressed. Based on the voltage at this voltage divider point, a bias voltage is supplied to the second transistor, thereby suppressing the decrease in gain of the gate-cathode amplifier circuit. Attached Figure Description

[0012] Figure 1 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the first embodiment.

[0013] Figure 2 This is a graph illustrating an example of the relationship between the power supply voltage Vdd1 and the bias voltages Vg2, Vg3, Vg4, and Vg5 of the second transistor 12.

[0014] Figure 3 This is the equivalent circuit diagram of the gate-cathode amplifier circuit of the comparative example.

[0015] Figure 4 It means Figure 3 The graph shows the relationship between the power supply voltage Vdd1 and the bias voltage of the gate-cathode amplifier circuit in the comparative example.

[0016] Figure 5 This is the equivalent circuit diagram of the gate-cathode amplifier circuit of another comparative example.

[0017] Figure 6 It means Figure 5 The graph shows the relationship between the power supply voltage Vdd1 and the bias voltage of the gate-cathode amplifier circuit in the comparative example.

[0018] Figure 7 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the second embodiment.

[0019] Figure 8 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the third embodiment.

[0020] Figure 9 This is a graph illustrating an example of the relationship between the power supply voltage Vdd1 and the bias voltages Vg2, Vg3, Vg4, and Vg5 of the second transistor 12.

[0021] Figure 10 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the fourth embodiment.

[0022] Figure 11 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the fifth embodiment.

[0023] Figure 12 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the sixth embodiment.

[0024] Figure 13This is an equivalent circuit diagram of the bias voltage source 22 of the gate-cathode amplifier circuit in the 7th embodiment.

[0025] Figure 14 This is an equivalent circuit diagram of the bias voltage source 22 of the gate-cathode amplifier circuit in the 8th embodiment.

[0026] Explanation of reference numerals in the attached figures

[0027] 11. First transistor; 12. Second transistor; 20. Bias circuit; 21. Resistor voltage divider circuit; 21P, voltage divider point; 22. Bias voltage source; 22A, voltage regulator; 23. First diode; 24. Multistage diode circuit; 24A, third diode; 25. Low bias voltage source; 40. Second diode; 50. Power supply wiring; 51. Variable voltage power supply circuit; 61. Resistor voltage divider circuit; 61P, voltage divider point; 62. Switch; 63. Operational amplifier; 64. Transistor; 65. Resistor voltage divider circuit; 65P, voltage divider point; 66. Capacitor; 67. Temperature detection circuit; 70. Bias circuit; 71, 75. Matching circuit; 80. Control circuit. Detailed Implementation

[0028] [First Embodiment]

[0029] Reference Figure 1 and Figure 2 The gate-cathode amplifier circuit of the first embodiment will be described. Figure 1 This is an equivalent circuit diagram of the gate-cathode amplifier circuit of the first embodiment. The high-frequency signal Pin is input to the gate of the first transistor 11 via the impedance matching circuit 71. The bias circuit 70 supplies a bias voltage Vg1 to the gate of the first transistor 11 via the resistor element R1.

[0030] Four second transistors 12 connected in series are connected to the gate and cathode of the first transistor 11. Furthermore, the number of second transistors 12 is not limited to four; at least one is acceptable. For example, there may be one, two, three, or more than five second transistors 12.

[0031] NMOSFETs are used as transistor 11 and transistor 12. The source of transistor 11 is connected to the reference potential (ground), and a series circuit consisting of multiple transistors 12 is connected to the drain of transistor 11. Transistor 11 and the four transistors 12 are sequentially numbered from the reference potential side to distinguish them. Transistor 11 is the transistor of stage 1, and the four transistors 12 are numbered sequentially from 2 to 5. The transistor 12 with the sequential number n is called the second transistor 12 of stage n. The gates of the multiple transistors 12 are each AC grounded via capacitor C2.

[0032] The bias circuit 20 supplies bias voltages to the gates of the plurality of second transistors 12 via resistor R2. The bias voltages supplied to the gates of the second transistors 12 in stages 2 through 5 are labeled as Vg2, Vg3, Vg4, and Vg5.

[0033] Power supply wiring 50 is connected to a variable voltage power supply circuit 51. The variable voltage power supply circuit 51 applies a variable power supply voltage Vdd1 to the power supply wiring 50, which is modulated accordingly with the high-frequency signal Pin, using techniques such as envelope tracking (ET mode) and average power tracking (APT mode). The power supply voltage Vdd1 is variable within a set operating range.

[0034] Power supply wiring 50 applies a power supply voltage Vdd1 to the gate-cathode connection circuit containing the first transistor 11 and four second transistors 12 via choke coil L. In other words, the drain of the second transistor 12 in the fifth stage is connected to power supply wiring 50 via choke coil L. The amplified high-frequency signal Pout is output from the connection point between the gate-cathode connection circuit composed of the first transistor 11 and four second transistors 12 and the choke coil L via impedance matching circuit 75.

[0035] Next, the structure of the bias circuit 20 will be described. A resistor divider circuit 21 is connected between the power supply wiring 50 and the reference potential. The resistor divider circuit 21 has a voltage divider point 21P corresponding to each of the plurality of second transistors 12. Furthermore, when there is only one number of second transistors 12, the voltage divider point 21P of the resistor divider circuit 21 is also only one. The resistor divider circuit 21 supplies a bias voltage to the corresponding second transistor 12 based on the voltage of each of the plurality of voltage divider points 21P.

[0036] For example, the voltage of each of the multiple voltage divider points 21P is applied to the gate of the corresponding second transistor 12 via the resistor element R2. When the multiple voltage divider points 21P of the resistive voltage divider circuit 21 are sequentially labeled with identification numbers #2, #3, #4, and #5 from the reference potential side, the voltage divider points 21P with identification numbers #2, #3, #4, and #5 are respectively connected to the gates of the second transistors 12 in the second, third, fourth, and fifth stages. That is, the voltage divider point 21P that is relatively close to the reference potential among the multiple voltage divider points 21P is connected to the gate of the second transistor 12 that is relatively close to the first transistor 11 among the multiple second transistors 12.

[0037] A bias voltage source 22 generates a reference voltage Vgf1. A voltage regulator may be used as the bias voltage source 22. The reference voltage Vgf1 forms the basis for the bias voltage supplied to the plurality of second transistors 12. A first diode 23 is connected between the output node of the bias voltage source 22 and at least some of the voltage division points 21P of the resistor divider circuit 21. The first diodes 23 are connected in a positive direction from the output node of the bias voltage source 22 toward the voltage division points 21P. In the first embodiment, the first diode 23 is not connected at voltage division point 21P with identification number #2, and is connected at voltage division points 21P with identification numbers #3, #4, and #5, respectively.

[0038] Next, refer to Figure 2 The relationship between the power supply voltage Vdd1 and the bias voltages Vg2, Vg3, Vg4, and Vg5 of the second transistor 12 is explained. Figure 2 This is a diagram illustrating an example of the relationship between the power supply voltage Vdd1 and the bias voltages Vg2, Vg3, Vg4, and Vg5 of the second transistor 12. The bias voltages Vg2, Vg3, Vg4, and Vg5 are equal to the voltages at the voltage divider points 21P of the corresponding identification numbers #2, #3, #4, and #5 of the resistor divider circuit 21. Figure 2 The horizontal axis of the graph shows the normalized value of the supply voltage Vdd1, and the vertical axis shows the normalized value of the bias voltage. Furthermore, both the supply voltage Vdd1 and the bias voltage are normalized using the same voltage as a reference.

[0039] The reference voltage Vgf1 is lower than the upper limit and higher than the lower limit of the operating range of the power supply voltage Vdd1. For example, the normalized value of the upper limit of the operating range of the power supply voltage Vdd1 is 1, and the lower limit is 0.2. The normalized value of the reference voltage Vgf1 is, for example, 0.4. The voltages of the voltage divider points 21P of the resistor voltage divider circuit 21, which are connected to the bias voltage source 22 via the first diode 23 and whose identification numbers are #3, #4, and #5, are not lower than the reference voltage Vgf1 - Vf. Here, Vf is the forward voltage of the first diode 23.

[0040] When the normalized value of the power supply voltage Vdd1 is 1, which is the upper limit of the operating range, the bias voltages Vg5, Vg4, Vg3, and Vg2 are approximately equal to the values ​​obtained by the voltage division obtained by the resistor voltage divider circuit 21. The voltage division ratio of the resistor voltage divider circuit 21 is set such that the bias voltages Vg5, Vg4, and Vg3 are higher than the reference voltage Vgf1, and the bias voltage Vg2 is lower than the reference voltage Vgf1.

[0041] When the power supply voltage Vdd1 decreases, the bias voltages Vg5, Vg4, Vg3, and Vg2 also decrease. After the bias voltages Vg5, Vg4, and Vg3 decrease to the reference voltage Vgf1 - Vf, if the power supply voltage Vdd1 decreases further, the first diode 23 will conduct. Therefore, the bias voltages Vg5, Vg4, and Vg3 stop decreasing and roughly represent constant values. The bias voltage Vg2 represents the potential difference between the bias voltage Vg3 and the base potential obtained by the voltage divider circuit 21. Therefore, when the power supply voltage Vdd1 decreases, the bias voltage Vg2 also stops decreasing at the moment when the bias voltage Vg3 stops decreasing.

[0042] Next, the superior effects of the first embodiment will be explained. When the bias voltage of the second transistor 12 drops excessively, the second transistor 12 turns off, and the gain of the gate-cathode amplifier circuit decreases significantly. In the first embodiment, as... Figure 2 As shown, the lower limit of the bias voltage of the second transistor 12 is limited by the bias voltage source 22 and multiple first diodes 23. As a result, a significant decrease in the gain of the gate-cathode amplifier circuit is suppressed.

[0043] Next, with Figure 3 and Figure 4 Compared to the comparative examples shown, the superior effects of the first embodiment will be explained. Figure 3 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the comparative example. Figure 3 In the comparative example shown, the resistor divider circuit 21 is not connected to the first embodiment ( Figure 1 The bias voltage source 22 and the first diode 23 are used for biasing.

[0044] Figure 4 It means Figure 3 The graph shows the relationship between the power supply voltage Vdd1 and the bias voltage of the gate-cathode amplifier circuit in the comparative example. Figure 4 The horizontal axis of the graph represents the normalized value of the supply voltage Vdd1, and the vertical axis represents the normalized value of the bias voltage. In this comparative example, the bias voltages Vg5, Vg4, Vg3, and Vg2 vary proportionally to the supply voltage Vdd1. Therefore, when the normalized value of the supply voltage Vdd1 decreases to the lower limit of the operating range of 0.2, the normalized values ​​of the bias voltages Vg5, Vg4, Vg3, and Vg2 decrease to less than 0.2.

[0045] In this structure, when the gain is referenced to the upper limit of the operating range (normalized value is 1) when the supply voltage Vdd1 is the supply voltage, the gain deviation (reduction) is large near the lower limit. Specifically, when the supply voltage Vdd1 is near the lower limit of the operating range (e.g., the normalized value is around 0.2), the bias voltages Vg2, Vg3, Vg4, and Vg5 are too low, resulting in a significant reduction in gain.

[0046] In contrast, in the first embodiment, such as Figure 2 As shown, when the power supply voltage Vdd1 is near the lower limit of the operating range (e.g., a normalized value of approximately 0.1), the bias voltages Vg3, Vg4, and Vg5 are maintained at values ​​higher than the lower limit of the operating range of the power supply voltage Vdd1, i.e., values ​​obtained by subtracting the forward voltage Vf of the first diode 23 from the reference voltage Vgf1. Therefore, even when the power supply voltage Vdd1 is reduced to near the lower limit of the operating range, the decrease in gain can be suppressed. Furthermore, the source voltage of the second transistor 12 in the second stage is lower than the source voltage of the second transistor 12 in the third stage and above, so even when the bias voltage Vg2 is reduced to near the lower limit of the power supply voltage Vdd1 (normalized value 0.2), the second transistor 12 does not turn off. Therefore, the decrease in gain of the gate-cathode amplifier circuit is suppressed. Furthermore, the voltage division ratio and reference voltage Vgf1 of the resistor divider circuit 21 are set such that even if the power supply voltage Vdd1 drops to its lower limit (normalized value 0.2), the bias voltage Vg2 remains at a value higher than the lower limit of the power supply voltage Vdd1.

[0047] Next, with Figure 5 and Figure 6 Compared to the comparative examples shown, the superior effects of the first embodiment will be explained. Figure 5 This is the equivalent circuit diagram of another comparative example of a gate-cathode amplifier circuit. Figure 5 In the comparative example shown, the resistor divider circuit 21 is connected between the fixed voltage Vsup and the reference potential.

[0048] Figure 6 It means Figure 5 The graph shows the relationship between the power supply voltage Vdd1 and the bias voltage of the gate-cathode amplifier circuit in the comparative example. Figure 6 The horizontal axis of the graph represents the normalized value of the supply voltage Vdd1, and the vertical axis represents the normalized value of the bias voltage. A fixed voltage Vsup is applied to the resistor divider circuit 21, so even if the supply voltage Vdd1 changes, the bias voltages Vg2, Vg3, Vg4, and Vg5 remain constant. As a result, the gain reduction when the supply voltage Vdd1 drops to near its lower limit is suppressed. However, this leads to the problems described below.

[0049] When the supply voltage Vdd1 drops to near the lower limit of the operating range (e.g., a normalized value of approximately 0.2), the bias voltages Vg3, Vg4, and Vg5 are much higher than the supply voltage Vdd1. Therefore, particularly in the second transistor 12 of the fifth stage, the difference between the bias voltage Vg5 and the supply voltage Vdd1 becomes large, and the gate-drain voltage of the second transistor 12 of the fifth stage exceeds its withstand voltage. Consequently, the reliability of the gate-cathode amplifier circuit decreases.

[0050] In contrast, in the first embodiment, such as Figure 2 As shown, when the power supply voltage Vdd1 drops to near the lower limit of the operating range, the bias voltages Vg3, Vg4, and Vg5 drop to approximately the same value obtained by subtracting the forward voltage Vf of the first diode 23 from the reference voltage Vgf1. Therefore, the gate-drain voltage of each of the second transistors 12 is unlikely to exceed its withstand voltage. This suppresses any decrease in the reliability of the gate-cathode amplifier circuit.

[0051] Apart from Figure 3 , Figure 5 In addition to the comparative examples shown, digital arithmetic circuits, such as... Figure 2 As shown, the bias voltages Vg2, Vg3, Vg4, and Vg5 are varied. However, in this structure, AD conversion, digital calculation, and DA conversion using an AD converter that detects the power supply voltage Vdd1 are required, as well as DA conversion using a DA converter that generates the bias voltages are necessary. Therefore, the tracking speed of the bias voltages Vg2, Vg3, Vg4, and Vg5 relative to the change in the power supply voltage Vdd1 is slower.

[0052] It is also possible to use an analog operational circuit with an operational amplifier to replace the digital operational circuit. In this structure, the following speed of the bias voltages Vg2, Vg3, Vg4, and Vg5 relative to the change in the power supply voltage Vdd1 is limited by the operating speed of the operational amplifier.

[0053] In contrast, in the first embodiment, a resistor divider circuit 21 connected to the power supply voltage Vdd1 is used ( Figure 1 The bias voltage source 22 and the first diode 23 generate bias voltages Vg2, Vg3, Vg4, and Vg5, so there is almost no delay in the change of bias voltages Vg2, Vg3, Vg4, and Vg5 relative to the change of power supply voltage Vdd1.

[0054] As described above, in the first embodiment, gain deviation when the power supply voltage Vdd1 changes can be suppressed, high reliability can be maintained, and sufficiently fast following speed of bias voltages Vg2, Vg3, Vg4, and Vg5 relative to the change in power supply voltage Vdd1 can be achieved.

[0055] In the gate-cathode amplifier circuit of the first embodiment, the first transistor 11 and the second transistor 12 use NMOSFETs, but bipolar transistors can also be used. When bipolar transistors are used for the first transistor 11 and the second transistor 12, in the above description, the source, drain, and gate of the first transistor 11 and the second transistor 12 can be replaced with emitter, collector, and base, respectively.

[0056] [Second Embodiment]

[0057] Next, refer to Figure 7 The gate-cathode amplifier circuit of the second embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 1 and Figure 2 The structure shared by the gate-cathode amplifier circuit in the first embodiment described herein is omitted from the description.

[0058] Figure 7 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the second embodiment. In the first embodiment ( Figure 1 In the first embodiment, the resistor divider circuit 21 is directly connected to the power supply wiring 50. In contrast, in the second embodiment, the second diode 40 is connected between the power supply wiring 50 and the resistor divider circuit 21. The second diode 40 is connected in a positive direction from the power supply wiring 50 toward the resistor divider circuit 21.

[0059] Next, the superior effects of the second embodiment will be explained. The second diode 40 has the function of blocking the current from the bias voltage source 22 toward the power supply wiring 50 when the power supply voltage Vdd1 decreases and becomes lower than the reference voltage Vgf1. As a result, useless energy consumption caused by the current flowing from the bias voltage source 22 toward the power supply wiring 50 can be suppressed.

[0060] [Embodiment 3]

[0061] Next, refer to Figure 8 and Figure 9 The gate-cathode amplifier circuit of the third embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 1 and Figure 2 The structure shared by the gate-cathode amplifier circuit in the first embodiment described herein is omitted from the description.

[0062] Figure 8 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the third embodiment. In the first embodiment ( Figure 1 In the first embodiment, the same reference voltage Vgf1 is applied to the anodes of the plurality of first diodes 23. In contrast, in the third embodiment, the bias voltage source 22 has a plurality of output nodes, and reference voltages of different heights are applied to the anodes of the plurality of first diodes 23 respectively.

[0063] In addition, in the first embodiment ( Figure 1In the first embodiment, the first diode 23 is not connected to the voltage divider point 21P corresponding to identification number #2 of the second transistor 12 in the second stage. In contrast, in the third embodiment, the first diode 23 is connected to multiple voltage divider points 21P corresponding to identification numbers #2, #3, #4, and #5 of all the second transistors 12 in stages 2 through 5, respectively. Furthermore, in the third embodiment, similar to the first embodiment, the structure in which the first diode 23 is not connected to the voltage divider point 21P corresponding to identification number #2 of the second transistor 12 in the second stage can also be adopted.

[0064] The bias voltage source 22 and the plurality of first diodes 23 each include a plurality of voltage regulators 22A. The plurality of voltage regulators 22A apply a reference voltage Vgf to the anode of the first diode 23, which is connected to the voltage divider points 21P of identification numbers #2, #3, #4, and #5, respectively. 12 Vgf 13 Vgf 14 Vgf 15 Reference voltage Vgf 12 Vgf 13 Vgf 14 Vgf 15 The size relationship of Vgf is as follows. 12 <Vgf 13 <Vgf 14 <Vgf 15 .

[0065] Next, refer to Figure 9 The relationship between the power supply voltage Vdd1 and the bias voltages Vg2, Vg3, Vg4, and Vg5 of the second transistor 12 is explained. Figure 9 This is a graph illustrating an example of the relationship between the power supply voltage Vdd1 and the bias voltages Vg2, Vg3, Vg4, and Vg5 of the second transistor 12. In the first embodiment ( Figure 2 In the first embodiment, when the power supply voltage Vdd1 drops to near the lower limit of the operating range, the bias voltages Vg3, Vg4, and Vg5 are all close to the values ​​obtained by subtracting the forward voltage Vf of the first diode 23 from the reference voltage Vgf1. In contrast, in the third embodiment, when the power supply voltage Vdd1 drops to near the lower limit of the operating range, the bias voltages Vg2, Vg3, Vg4, and Vg5 are respectively close to the values ​​obtained by subtracting the forward voltage Vf of the first diode 23 from the reference voltage Vgf1. 12 Vgf 13 Vgf 14 Vgf 15 The value obtained by subtracting the forward voltage Vf of the first diode 23.

[0066] Next, the superior effects of the third embodiment will be explained. In the third embodiment, the lower limits of the bias voltages Vg2, Vg3, Vg4, and Vg5 when the power supply voltage Vdd1 is close to the lower limit of the operating range can be set separately. As a result, appropriate bias voltages can be supplied to the second transistors 12 of the second to fifth stages respectively.

[0067] [Example 4]

[0068] Next, refer to Figure 10 The gate-cathode amplifier circuit of the fourth embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 1 and Figure 2 The structure shared by the gate-cathode amplifier circuit in the first embodiment described herein is omitted from the description.

[0069] Figure 10 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the fourth embodiment. In the first embodiment ( Figure 1 In the first embodiment, a PN junction diode is used as the first diode 23. In contrast, in the fourth embodiment, a diode-connected NMOSFET (Non-Mechanical Modem) is used as the first diode 23, meaning an NMOSFET with its gate and drain connected. In the diode-connected NMOSFET, the drain and source serve as the anode and cathode of the diode, respectively. Alternatively, a diode-connected PMOSFET (Physical Modem with its gate and drain connected) can also be used as the first diode 23. When using a PMOSFET, the drain and source serve as the cathode and anode of the diode, respectively.

[0070] Next, the superior effects of the fourth embodiment will be explained. Similar to the first embodiment, the fourth embodiment suppresses a significant decrease in the gain of the gate-cathode amplifier circuit and also suppresses a decrease in reliability. Furthermore, in the fourth embodiment, the first diode 23 can be formed simultaneously with the first transistor 11 and the second transistor 12 during the manufacturing process.

[0071] Next, the gate-cathode amplifier circuit of the modified example of the fourth embodiment will be described. As a modified example of the fourth embodiment, the gate-cathode amplifier circuit of the second embodiment ( Figure 7 Similarly, a second diode 40 can be connected between the power supply wiring 50 and the resistor divider circuit 21. In this case, a diode-connected NMOSFET or PMOSFET can be used as the second diode 40.

[0072] [Version 5]

[0073] Next, refer to Figure 11 The gate-cathode amplifier circuit of the fifth embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 1 and Figure 2The structure shared by the gate-cathode amplifier circuit in the first embodiment described herein is omitted from the description.

[0074] Figure 11 This is the equivalent circuit diagram of the gate-cathode amplifier circuit of the fifth embodiment. The gate-cathode amplifier circuit of the fifth embodiment differs from that of the gate-cathode amplifier circuit of the first embodiment (…). Figure 1 In addition to the components of the bias voltage source 22, it also includes a multi-stage diode circuit 24 connected between the output node of the bias voltage source 22 and the reference potential. The multi-stage diode circuit 24 includes a plurality of third diodes 24A connected in multiple stages. The plurality of third diodes 24A are connected in a positive direction from the reference voltage Vgf1 at the output node of the bias voltage source 22 toward the reference potential.

[0075] At least one of the plurality of first diodes 23 is connected to the bias voltage source 22 via at least one third diode 24A in the multi-stage diode circuit 24. The first diode 23 connected to the voltage divider point 21P (closer to the reference potential) with a relatively smaller identification number is connected to the bias voltage source 22 via a relatively larger number of third diodes 24A compared to the first diode 23 connected to the voltage divider point 21P (closer to the power supply wiring 50) with a relatively larger identification number. Furthermore, at least one third diode 24A is connected between the anode of the first diode 23 connected to the voltage divider point 21P with identification number #2 and the reference potential.

[0076] For example, voltage divider points 21P with identification numbers #2, #3, #4, and #5 are connected to the gates of the second transistor 12 in stages 2, 3, 4, and 5, respectively. The anode of the first diode 23 connected to voltage divider point 21P with identification number #2 is connected to the bias voltage source 22 via three third diodes 24A. The anode of the first diode 23 connected to voltage divider point 21P with identification number #3 is connected to the bias voltage source 22 via two third diodes 24A. The anode of the first diode 23 connected to voltage divider point 21P with identification number #4 is connected to the bias voltage source 22 via one third diode 24A. The anode of the first diode 23 connected to voltage divider point 21P with identification number #5 is connected to the bias voltage source 22 without via a third diode 24A.

[0077] Next, the superior effects of the fifth embodiment will be explained. First, we examine the case where the voltages of the anodes of all the first diodes 23, without the multi-stage diode circuit 24 connected, are equal to the reference voltage Vgf1. When the power supply voltage Vdd1 becomes lower than the reference voltage Vgf1, according to the voltage division ratio of the resistor voltage divider circuit 21, current flows from the voltage division point 21P of identification number #4 through the voltage division point 21P of identification number #5 to the power supply wiring 50. At this time, the bias voltage Vg4 of the second transistor 12 of the fourth stage is higher than the bias voltage Vg5 of the second transistor 12 of the fifth stage.

[0078] In contrast, in the fifth embodiment, a voltage divided by a multi-stage diode circuit 24 is applied to the anodes of the plurality of first diodes 23. That is, the voltage applied to the anode of the first diode 23 connected to the voltage divider point 21P of identification number #4 is lower than the voltage applied to the anode of the first diode 23 connected to the voltage divider point 21P of identification number #5. As a result, even when the power supply voltage Vdd1 becomes lower than the reference voltage Vgf1, current is difficult to flow from the voltage divider point 21P of identification number #4 to the voltage divider point 21P of identification number #5. Therefore, it is difficult to generate a state where the bias voltage Vg4 of the second transistor 12 of the fourth stage is higher than the bias voltage Vg5 of the second transistor 12 of the fifth stage.

[0079] As an example, the reference voltage Vgf1 can be divided by a multi-stage diode circuit 24, thereby applying the third embodiment ( ) to the anode of each of the first diodes 23 connected to the voltage divider points 21P of identification numbers #2, #3, #4, and #5. Figure 8 , Figure 9 The reference voltage Vgf shown is... 12 Vgf 13 Vgf 14 Vgf 15 The multi-stage diode circuit 24 is designed in a certain manner. In the fifth embodiment, a third diode 24A is connected between the anodes of the two first diodes 23 connected to the adjacent voltage divider point 21P. However, in order to apply an appropriate voltage to the anode of the first diodes 23, the number of third diodes 24A may be more than two.

[0080] For example, if the voltage applied to the anode of the first diode 23 connected to the voltage divider point 21P of identification number #2 becomes too low, the second transistor 12 of the second stage may disconnect. In order to maintain the voltage applied to the anode of the first diode 23 connected to the voltage divider point 21P of identification number #2 at a preferred level, the number of third diodes 24A connected between the anode of the first diode 23 connected to the voltage divider point 21P of identification number #2 and the reference potential may be set to two or more.

[0081] In order to make the voltage divided by the multi-stage diode circuit 24 less susceptible to the influence of the voltage at the voltage division point 21P of the resistor voltage divider circuit 21, it is preferable to use a diode with a lower on-resistance than the first diode 23 as the third diode 24A.

[0082] If the third diode 24A is disconnected, an appropriate voltage division ratio cannot be obtained. Therefore, it is preferable that the sum of the forward voltages of the multiple third diodes 24A (the forward voltage of the multi-stage diode circuit 24) is lower than the reference voltage Vgf1. Furthermore, if the forward voltage of the multi-stage diode circuit 24 becomes too low compared to the reference voltage Vgf1, the forward current flowing into the multi-stage diode circuit 24 becomes excessive. To suppress the forward current flowing into the multi-stage diode circuit 24, it is preferable that the forward voltage of the multi-stage diode circuit 24 is close to the reference voltage Vgf1. For example, the forward voltage of the multi-stage diode circuit 24 may be below the reference voltage Vgf1, but it is preferable that the number of third diodes 24A is determined in a manner that minimizes the difference between the forward voltage of the multi-stage diode circuit 24 and the reference voltage Vgf1. For example, the number of third diodes 24A can be determined in such a way that if a third diode 24A is added, the forward voltage of the multi-stage diode circuit 24 will be greater than the reference voltage Vgf1 (becoming the maximum number of times the forward voltage of the multi-stage diode circuit 24 is not greater than the reference voltage Vgf1).

[0083] [Sixth Embodiment]

[0084] Next, refer to Figure 12 The gate-cathode amplifier circuit of the sixth embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 11 The structure shared by the gate-cathode amplifier circuit in the fifth embodiment described herein is omitted from the description.

[0085] Figure 12 This is the equivalent circuit diagram of the gate-cathode amplifier circuit in the sixth embodiment. In the fifth embodiment ( Figure 11 In the first embodiment, the low-voltage side of the multi-stage diode circuit 24 is connected to a reference potential. In contrast, in the sixth embodiment, a low-bias voltage source 25 is connected to the low-voltage side of the multi-stage diode circuit 24. The low-bias voltage source 25 applies a low reference voltage Vgf2 to the end of the multi-stage diode circuit 24, which is higher than the reference potential and lower than the reference voltage Vgf1.

[0086] Next, the superior effects of the sixth embodiment will be explained. In the sixth embodiment, a low-bias voltage source 25 is connected to the low-voltage side of the multi-stage diode circuit 24, thus enabling the application of a low reference voltage Vgf2 other than the reference potential. Therefore, the freedom of selection for the bias voltages Vg2, Vg3, Vg4, and Vg5 supplied to the plurality of second transistors 12 is increased. For example, if the bias voltage Vg2 of the second transistor 12 in the second stage becomes too low when a reference potential is applied to the low-voltage side of the multi-stage diode circuit 24, by setting the low reference voltage Vgf2 higher than the reference potential, the undesirable situation of the bias voltage Vg2 of the second transistor 12 in the second stage becoming too low can be avoided.

[0087] [Seventh Embodiment]

[0088] Next, refer to Figure 13 The gate-cathode amplifier circuit of the seventh embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 1 and Figure 2 The structure shared by the gate-cathode amplifier circuit in the first embodiment described herein is omitted from the description.

[0089] Figure 13 This is an equivalent circuit diagram of the bias voltage source 22 of the gate-cathode amplifier circuit in the 7th embodiment. In the 1st embodiment ( Figure 1 In the first embodiment, the reference voltage Vgf1 generated by the bias voltage source 22 is a fixed value. In contrast, in the seventh embodiment, the bias voltage source 22 can vary the reference voltage Vgf1.

[0090] A bandgap voltage VBG is applied to one end of a resistor divider circuit 61 with multiple voltage divider points 61P, and a reference potential is applied to the other end. Switch 62, in response to a control signal input from control circuit 80, selects one voltage divider point 61P from the multiple voltage divider points 61P of the resistor divider circuit 61 and connects the selected voltage divider point 61P to the output node. The voltage of the voltage divider point 61P selected by switch 62 is input to the inverting input node of operational amplifier 63.

[0091] A power supply voltage Vdd2 is applied to the transistor side of the series circuit consisting of a PMOSFET transistor 64 and a resistor divider circuit 65, while a reference potential is applied to the resistor divider circuit 65. More specifically, the source of transistor 64 is connected to the power supply voltage Vdd2, and the drain is connected to the resistor divider circuit 65.

[0092] The voltage divider point 65P of the resistor voltage divider circuit 65 is connected to the non-inverting input node of the operational amplifier 63. The output node of the operational amplifier 63 is connected to the gate of the transistor 64. The drain of the transistor 64 is connected to the reference potential via the capacitor 66. The reference voltage Vgf1 is output from the drain of the transistor 64.

[0093] The voltage at the voltage divider point 65P of the resistor voltage divider circuit 65 is controlled in such a way that the voltage at the voltage divider point 61P selected by the switch 62 is consistent with the voltage at the voltage divider point 61P selected by the switch 62 and the voltage division ratio of the resistor voltage divider circuit 65. That is, the bias voltage source 22 is configured to change the reference voltage Vgf1 in accordance with the control signal input from the control circuit 80.

[0094] Next, the superior effects of the seventh embodiment will be explained. In the seventh embodiment, the reference voltage Vgf1 can be varied. For example, the control circuit 80 controls the switch 62 accordingly with the operating range of the power supply voltage Vdd1, the operating frequency band of the gate-cathode amplifier circuit, and the power mode of the gate-cathode amplifier circuit (e.g., normal mode, low power mode), thereby enabling the second transistor 12 ( Figure 1 The lower limit of the bias voltage is adjusted to an appropriate value.

[0095] The function of the bias voltage source 22 in the 7th embodiment to change the reference voltage Vgf1 can also be applied to the 2nd embodiment. Figure 7 ), 3rd embodiment ( Figure 8 ), Example 4 ( Figure 10 ), 5th embodiment ( Figure 11 ) and the 6th embodiment ( Figure 12 The gate-cathode amplifier circuit of any embodiment of )

[0096] [Embodiment 8]

[0097] Next, refer to Figure 14 The gate-cathode amplifier circuit of the eighth embodiment will be described below. Hereinafter, the circuit will be compared with the reference circuit. Figure 13 The structure shared by the gate-cathode amplifier circuit in the seventh embodiment described herein is omitted from the description.

[0098] Figure 14 This is an equivalent circuit diagram of the bias voltage source 22 of the gate-cathode amplifier circuit in the 8th embodiment. In the 7th embodiment ( Figure 13 In the first embodiment, a voltage at a voltage divider point 61P selected based on a control signal from the control circuit 80 is applied to the inverting input node of the operational amplifier 63. In contrast, in the second embodiment, an output voltage from a temperature detection circuit 67 is applied to the inverting input node of the operational amplifier 63. The temperature detection circuit 67, for example, changes the output voltage in response to the ambient temperature.

[0099] Next, the superior effects of the eighth embodiment will be explained. For example, when the ambient temperature changes, the first diode 23 ( Figure 1The forward voltage Vf of the first diode 23 changes. If the reference voltage Vgf1 remains unchanged when the forward voltage Vf changes, the lower limit of the voltage at the voltage divider point 21P changes. In the eighth embodiment, when the forward voltage Vf of the first diode 23 changes due to temperature changes, the lower limit of the voltage at the voltage divider point 21P can be kept constant by changing the reference voltage Vgf1 in a way that compensates for this change. As an example, when the ambient temperature rises, the forward voltage Vf of the first diode 23 decreases. The reference voltage Vgf1 can be decreased accordingly to the amount of decrease in the forward voltage Vf.

[0100] Furthermore, it can compensate for changes in the gain of the gate-cathode amplifier circuit caused by variations in ambient temperature. For example, the gain of the gate-cathode amplifier circuit decreases when the ambient temperature rises. By increasing the reference voltage Vgf1 when the ambient temperature rises, the decrease in gain can be compensated. In this case, the change in the forward voltage Vf of the first diode 23 caused by the temperature change can be taken into account, thus changing the reference voltage Vgf1.

[0101] Next, the gate-cathode amplifier circuit of the modified example of the eighth embodiment will be described. In the eighth embodiment, the temperature detection circuit 67 changes the output voltage based on the ambient temperature. As a modified example of the eighth embodiment, it can also be configured as follows: with the first diode 23 ( Figure 1 The temperature change of the first diode 23 and the second transistor 12 causes a corresponding change in the output voltage of the temperature detection circuit 67. For example, the temperature detection circuit 67 may have a temperature sensor formed on the same substrate as the semiconductor substrate on which the first diode 23, the first transistor 11, or the second transistor 12 are formed, and disposed in the vicinity of these elements.

[0102] The function of the bias voltage source 22 in embodiment 8 to change the reference voltage Vgf1 in accordance with temperature can also be applied to embodiment 2. Figure 7 ), 3rd embodiment ( Figure 8 ), Example 4 ( Figure 10 ), 5th embodiment ( Figure 11 ) and the 6th embodiment ( Figure 12 The gate-cathode amplifier circuit of any embodiment of )

[0103] The above embodiments are illustrative, and it is self-evident that partial substitutions or combinations of the structures shown in different embodiments are possible. The same effects achieved by the same structures in multiple embodiments are not mentioned sequentially in each embodiment. Furthermore, the present invention is not limited to the above embodiments. For example, various changes, improvements, combinations, etc., are possible, as will be apparent to those skilled in the art.

Claims

1. A gate-cathode amplifier circuit, wherein, The gate-cathode amplifier circuit includes: The first transistor is used to input high-frequency signals; At least one second transistor is connected to the gate and cathode of the first transistor; A bias circuit that supplies a bias voltage to the at least one second transistor; and The power supply wiring applies a variable power supply voltage to the gate-cathode connection circuit containing the first transistor and at least one second transistor. The bias circuit includes: A resistor divider circuit is connected between the power supply wiring and the reference potential, and has at least one voltage divider point corresponding to the at least one second transistor, and supplies a bias voltage to the corresponding second transistor based on the voltage of the at least one voltage divider point; A bias voltage source generates a reference voltage, which forms the basis for the bias voltage supplied to the at least one second transistor; and At least one first diode is connected between the output node of the bias voltage source and the at least one voltage divider point in a positive direction from the output node of the bias voltage source toward the at least one voltage divider point.

2. The gate-cathode amplifier circuit according to claim 1, wherein, The gate-cathode amplifier circuit also includes a second diode between the power supply wiring and the resistor divider circuit, the second diode being connected in a positive direction from the power supply wiring toward the resistor divider circuit.

3. The gate-cathode amplifier circuit according to claim 1 or 2, wherein, The at least one first diode is composed of a diode-connected transistor.

4. The gate-cathode amplifier circuit according to any one of claims 1 to 3, wherein, The bias voltage source is configured to change the reference voltage in accordance with the input control signal.

5. The gate-cathode amplifier circuit according to claim 4, wherein, The gate-cathode amplifier circuit also includes a temperature detection circuit that detects the temperature and applies the control signal to the bias voltage source based on the detected temperature.

6. The gate-cathode amplifier circuit according to any one of claims 1 to 5, wherein, The at least one second transistor comprises a plurality of second transistors interconnected by their gate cathodes. The at least one voltage divider point includes multiple voltage divider points corresponding to the multiple second transistors that are interconnected by their gate cathodes. The at least one first diode comprises a plurality of first diodes respectively connected to at least a portion of the plurality of voltage divider points.

7. The gate-cathode amplifier circuit according to claim 6, wherein, The bias voltage source has multiple output nodes, and applies reference voltages of different heights to the multiple first diodes respectively.

8. The gate-cathode amplifier circuit according to claim 6 or 7, wherein, The gate-cathode amplifier circuit also includes a multi-stage diode circuit composed of multiple third diodes, which are connected in multiple stages between the output node of the bias voltage source and a low reference voltage lower than the reference voltage, with the direction from the reference voltage toward the low reference voltage being positive. At least one of the plurality of first diodes is connected to the bias voltage source via at least one third diode in the multi-stage diode circuit. The first diode connected to the voltage divider point that is relatively close to the reference potential among the plurality of voltage divider points is connected to the bias voltage source via a relatively larger number of third diodes compared to the first diode connected to the voltage divider point that is relatively close to the power supply wiring.

9. The gate-cathode amplifier circuit according to claim 8, wherein, The gate-cathode amplifier circuit also includes a low-bias voltage source that generates a voltage higher than the reference potential as the low reference voltage.

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