# US 10,374,561 B2 · Amplification circuit

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- Number: US 10,374,561 B2
- Document ID: US10374561B2
- Status: Granted
- Kind: B2
- Application number: 15/914,674
- Filed: 2018-03-07
- Published: 2018-07-12
- Granted: 2019-08-06
- Earliest claimed: 2016-07-28
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Makoto Tabei; Daisuke Watanabe
- Web page: https://patentgrep.com/patent/US10374561B2

## CPC

- H03G 1/0035: {using continuously variable impedance elements}
- H03F 1/223: {with MOSFET's}
- H03F 1/301: {in MOSFET amplifiers (H03F1/303, H03F1/305, H03F1/308 take precedence)}
- H03F 1/56: Modifications of input or output impedances, not otherwise provided for
- H03F 1/565: {using inductive elements}
- H03F 3/193: with field-effect devices (H03F3/195 takes precedence)
- H03F 3/245: {with semiconductor devices only}
- H03F 2200/18: the bias of the gate of a FET being controlled by a control signal
- H03F 2200/222: A circuit being added at the input of an amplifier to adapt the input impedance of the amplifier
- H03F 2200/294: the amplifier being a low noise amplifier [LNA]
- H03F 2200/301: the loading circuit of an amplifying stage comprising a coil
- H03F 2200/387: A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
- H03F 2200/447: the amplifier being protected to temperature influence
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H03F 2200/492: A coil being added in the source circuit of a transistor amplifier stage as degenerating element
- H03G: CONTROL OF AMPLIFICATION
- H03F: AMPLIFIERS

## Abstract

Provided is an amplification circuit that amplifies an input signal and outputs an amplified signal. The amplification circuit includes: an amplification element that outputs the amplified signal from an output terminal thereof; an inductor having one end to which a power supply voltage is supplied and another end that is connected to the output terminal of the amplification element; a variable resistor that is connected in parallel with the inductor; and a resistance value adjusting circuit that adjusts a resistance value of the variable resistor in accordance with the temperature.

## Claims

### Claim 1

An amplification circuit that amplifies an input signal and outputs an amplified signal, the amplification circuit comprising:
an amplifier configured to output the amplified signal from an output terminal;
a variable resistance element connected between the output terminal and a power supply voltage; and
a resistance value adjusting circuit that is configured to adjust a resistance value of the variable resistance element,
wherein the variable resistance element comprises a first field-effect transistor (FET),
wherein the resistance value adjusting circuit comprises:
a first current generating circuit configured to generate a first current,
a second FET that is diode connected and through which the first current flows, and
a first voltage generating circuit configured to generate a first voltage that changes in accordance with a gate voltage of the second FET, and
wherein the resistance value adjusting circuit is configured to adjust a gate voltage of the first FET based on the first voltage.

### Claim 2 (depends on 1)

The amplification circuit according to claim 1, wherein the first voltage generating circuit comprises a diode that is connected to the second FET.

### Claim 3 (depends on 1)

The amplification circuit according to claim 1,
wherein the resistance value adjusting circuit further comprises:
a second current generating circuit configured to generate a second current, and
a second voltage generating circuit configured to generate a second voltage that changes in accordance with the second current, and
wherein the resistance value adjusting circuit is further configured to adjust the gate voltage of the first FET based on the second voltage.

### Claim 4 (depends on 1)

The amplification circuit according to claim 1, further comprising:
an inductor having one end to which a power supply voltage is supplied and another end that is connected to the output terminal of the amplifier,
wherein the variable resistance element is connected in parallel with the inductor.

### Claim 5 (depends on 1)

The amplification circuit according to claim 1, wherein the resistance value of the variable resistance element is adjusted in accordance with a temperature of the amplification circuit.