High frequency amplifier

Patent metadata

Field	Value
Publication number	US-11025205-B2
Application number	US-201716478427-A
Country	US
Kind code	B2
Filing date	Feb 22, 2017
Priority date	Feb 22, 2017
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

When a potential difference V1 between a source terminal of an E-type FET (11) and a source terminal of a D-type FET (12) is larger than a threshold voltage Vth, a protection circuit (13) starts an operation to reduce the potential difference V1 such that the potential difference V1 is smaller than the threshold voltage Vth. This makes it possible to prevent destruction of the E-type FET (11) even when a signal to be amplified is an RF signal.

First claim

The invention claimed is:

1. A high frequency amplifier comprising:
a first transistor having a gate terminal or a base terminal, a high frequency signal to be amplified being supplied to the gate terminal or the base terminal of the first transistor, the first transistor having a source terminal or an emitter terminal, either of which is grounded;
a second transistor having a source terminal or an emitter terminal, either of which is connected to a drain terminal or a collector terminal of the first transistor, the second transistor having a drain terminal or a collector terminal, an amplified high frequency signal being output from the drain terminal or the collector terminal of the second transistor; and
a protection circuit to start an operation to reduce a potential difference between the source terminal or the emitter terminal of the first transistor and the source terminal or the emitter terminal of the second transistor to make the potential difference smaller than a threshold voltage when the potential difference is larger than the threshold voltage, wherein the protection circuit includes a drive signal output circuit that determines the threshold voltage used in the operation.

2. The high frequency amplifier according to claim 1 , wherein
the protection circuit includes a power supply circuit to apply a voltage to the gate terminal or the base terminal of the first transistor, and
the power supply circuit increases the voltage to be applied to the gate terminal or the base terminal of the first transistor when the potential difference between the source terminal or the emitter terminal of the first transistor and the source terminal or the emitter terminal of the second transistor is larger than the threshold voltage.

3. The high frequency amplifier according to claim 2 , wherein
a drive signal output circuit comprises one end connected to the drain terminal or the collector terminal of the first transistor, the drive signal output circuit outputting a drive signal from the other end thereof when the potential difference is larger than the threshold voltage, and
the power supply circuit includes:
a power supply terminal to which a voltage is applied;
a first resistor in which one end thereof is connected to the power supply terminal;
a third transistor having a drain terminal or a collector terminal, either of which is connected to the other end of the first resistor, the third transistor having a gate terminal or a base terminal, either of which is connected to the other end of the drive signal output circuit;
a second resistor in which one end thereof is connected to the source terminal or the emitter terminal of the third transistor; and
a third resistor in which one end thereof is connected to the other end of the second resistor and the gate terminal or the base terminal of the first transistor, and the other end thereof is connected to a ground.

4. The high frequency amplifier according to claim 3 , wherein the drive signal output circuit includes a diode, a comparator, or an operational amplifier as a component to output a drive signal when the potential difference is larger than the threshold voltage.

5. The high frequency amplifier according to claim 1 , wherein
the protection circuit includes a power supply circuit to apply a voltage to a gate terminal or a base terminal of the second transistor, and
the power supply circuit decreases a voltage to be applied to the gate terminal or the base terminal of the second transistor when the potential difference between the source terminal or the emitter terminal of the first transistor and the source terminal or the emitter terminal of the second transistor is larger than the threshold voltage.

6. The high frequency amplifier according to claim 5 , wherein
a drive signal output circuit comprises one end connected to the drain terminal or the collector terminal of the first transistor, the drive signal output circuit outputting a drive signal from the other end thereof when the potential difference is larger than the threshold voltage, and
the power supply circuit includes:
a power supply terminal to which a voltage is applied;
a first resistor in which one end thereof is connected to the power supply terminal;
a second resistor in which one end thereof is connected to the other end of the first resistor;
a third transistor having a drain terminal or a collector terminal, either of which is connected to the other end of the second resistor, and the third transistor having a gate terminal or a base terminal, either of which is connected to the other end of the drive signal output circuit;
a third resistor in which one end thereof is connected to a source terminal or an emitter terminal of the third transistor, and the other end thereof is connected to a ground;
a fourth resistor in which one end thereof is connected to the other end of the first resistor, and the other end thereof is connected to the gate terminal or the base terminal of the second transistor; and
a capacitor in which one end thereof is connected to the other end of the first resistor, and the other end thereof is connected to the ground.

7. The high frequency amplifier according to claim 6 , wherein the drive signal output circuit includes a diode, a comparator, or an operational amplifier as a component to output a drive signal when the potential difference is larger than the threshold voltage.

8. The high frequency amplifier according to claim 5 , wherein
a drive signal output circuit comprises one end connected to the drain terminal or the collector terminal of the first transistor, the drive signal output circuit outputting a drive signal from the other end thereof when the potential difference is larger than the threshold voltage, and
the power supply circuit includes:
a power supply terminal to which a voltage is applied;
a first resistor in which one end thereof is connected to the power supply terminal;
a third transistor having a drain terminal or a collector terminal, either of which is connected to the other end of the first resistor, the third transistor having a gate terminal or a base terminal, either of which is connected to the other end of the drive signal output circuit;
a second resistor in which one end thereof is connected to a source terminal or an emitter terminal of the third transistor;
a third resistor in which one end thereof is connected to the other end of the second resistor, and the other end thereof is connected to a ground;
a fourth resistor in which one end thereof is connected to the power supply terminal;
a fifth resistor in which one end thereof is connected to the other end of the fourth resistor, and the other end thereof connected to the gate terminal or the base terminal of the second transistor;
a capacitor in which one end thereof is connected to the other end of the fourth resistor and the other end thereof is connected between the other end of the second resistor and one end of the third resistor; and
a varactor diode in which one end thereof is connected to the other end of the capacitor, and the other end thereof is connected to the ground.

9. The high frequency amplifier according to claim 8 , wherein the drive signal output circuit includes a diode, a comparator, or an operational amplifier as a component for outputting a drive signal when the potential difference is larger than the threshold voltage.

10. The high frequency amplifier according to claim 5 , wherein
a drive signal output circuit comprises one end connected to the drain terminal or the collector terminal of the first transistor, the drive signal output circuit outputting a drive signal from the other end thereof when the potential diff

Assignees

• Mitsubishi Electric Corp

Inventors

• Kuwata Eigo
• Yamaguchi Yutaro

Classifications

• H10D62/8503

  Nitride Group III-V materials, e.g. AlN or GaN · CPC title

• H10D30/472

  having lower bandgap active layer formed on top of wider bandgap layer, e.g. inverted HEMT · CPC title

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title

• H03F1/523

  for amplifiers using field-effect devices (H03F1/526 takes precedence) · CPC title

• H03F1/22 Primary

  by use of cascode coupling, i.e. earthed cathode or emitter stage followed by earthed grid or base stage respectively · CPC title