# US 10,771,029 B2 · Amplifier with scalable impedance adjustments over gain modes

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- Number: US 10,771,029 B2
- Document ID: US10771029B2
- Status: Granted
- Kind: B2
- Application number: 16/405,951
- Filed: 2019-05-07
- Published: 2019-10-31
- Granted: 2020-09-08
- Earliest claimed: 2016-08-31
- Assignees: Skyworks Solutions, Inc.
- Applicants: Skyworks Solutions, Inc.
- Inventors: Junhyung Lee
- Web page: https://patentgrep.com/patent/US10771029B2

## CPC

- H03G 3/3042: {in modulators, frequency-changers, transmitters or power amplifiers}
- H03F 1/0277: {Selecting one or more amplifiers from a plurality of amplifiers}
- H03F 1/223: {with MOSFET's}
- H03F 1/56: Modifications of input or output impedances, not otherwise provided for
- H03F 3/195: in integrated circuits
- H03F 3/211: {using a combination of several amplifiers (H03F3/60 takes precedence)}
- H03F 3/245: {with semiconductor devices only}
- H03F 3/72: Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal
- H03G 1/0029: {using field-effect transistors [FET]}
- H03G 1/0088: {using discontinuously variable devices, e.g. switch-operated}
- H03G 3/001: {Digital control of analog signals}
- H03G 3/3063: {using at least one transistor as controlling device, the transistor being used as a variable impedance device}
- H03F 2200/111: the amplifier being a dual or triple band amplifier, e.g. 900 and 1800 MHz, e.g. switched or not switched, simultaneously or not
- 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 2200/387: A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H03F 2203/7221: the gated amplifier being switched on or off by a switch at the output of the amplifier
- H04B 1/16: Circuits
- H03G: CONTROL OF AMPLIFICATION
- H03F: AMPLIFIERS
- H04B: TRANSMISSION

## Abstract

Disclosed herein are signal amplifiers that provide impedance adjustments for different gain modes. The impedance adjustments are configured to result in a constant real impedance for an input signal at the amplifier. The amplifiers include a scalable impedance adjustment circuit that adjusts inductance and/or a device width to compensate for changes in the total impedance presented to an input signal. By providing impedance adjustments, the amplifiers reduce losses and improve performance by improving impedance matching over a range of gain modes.

## Claims

### Claim 1

A radio-frequency (RF) signal amplifier configured to provide a plurality of gain modes, the signal amplifier comprising:
a power supply configured to provide a source current that differs for individual gain modes;
a gain stage including an RF stage transistor and a cascode stage transistor, the gain stage configured to receive the source current from the power supply to operate the gain stage at corresponding gain modes, a total input impedance presented to an input RF signal associated with a transconductance of the RF stage transistor; and
an impedance adjustment circuit coupled to the gain stage and configured to provide a tailored adjustment that compensates for changes in the transconductance using switchable inductive elements.

### Claim 2 (depends on 1)

The amplifier of claim 1 wherein the gain stage includes a plurality of switchable amplification branches each include a switching transistor and an RF stage transistor.

### Claim 3 (depends on 2)

The amplifier of claim 2 wherein in a first gain mode, a first plurality of the RF stage transistors is activated and in a second gain mode, lower than the first gain mode, a second plurality of the RF stage transistors is activated, the number of activated RF stage transistors being less in the second gain mode than the first gain mode.

### Claim 4 (depends on 1)

The amplifier of claim 1 wherein the amplifier is a low-noise amplifier (LNA).

### Claim 5 (depends on 1)

The amplifier of claim 1 wherein the switchable inductive elements include a plurality of switches that selectively couple corresponding inductive elements to a reference potential node.

### Claim 6 (depends on 1)

The amplifier of claim 1 wherein the tailored adjustment is configured so that the total impedance presented to the input RF signal is 50Ω for individual gain modes.

### Claim 7 (depends on 1)

The amplifier of claim 1 wherein the gain stage is scalable and includes a plurality of transistors in an electrically parallel configuration, each transistor associated with an individual switchable amplification branch that selectively activates the associated transistor.

### Claim 8 (depends on 7)

The amplifier of claim 7 wherein the impedance adjustment circuit is further configured to effectively scale a device width at a rate that matches a scaling of the source current for individual gain modes.

### Claim 9 (depends on 1)

The amplifier of claim 1 wherein the tailored impedance adjustment is further configured to result in a fixed real impedance for the total input impedance.

### Claim 10 (depends on 1)

The amplifier of claim 1 wherein the plurality of gain modes includes a low gain mode, a high gain mode, and one or more intermediate gain modes.

### Claim 11

A semiconductor die having a radio-frequency (RF) circuit, comprising:
a substrate; and
an RF amplifier configured to provide a plurality of gain modes implemented on the substrate, the RF amplifier including a power supply configured to provide a source current that differs for individual gain modes; the RF amplifier further including a gain stage including an RF stage transistor and a cascode stage transistor, the gain stage configured to receive the source current from the power supply to operate the gain stage at corresponding gain modes, a total input impedance presented to an input RF signal associated with a transconductance of the RF stage transistor; and the RF amplifier further including an impedance adjustment circuit coupled to the gain stage and configured to provide a tailored adjustment that compensates for changes in the transconductance using switchable inductive elements.

### Claim 12 (depends on 11)

The semiconductor die of claim 11 wherein the RF amplifier is a low-noise amplifier (LNA).

### Claim 13 (depends on 11)

The semiconductor die of claim 11 wherein the gain stage includes a plurality of switchable amplification branches each include a switching transistor and an RF stage transistor.

### Claim 14 (depends on 13)

The semiconductor die of claim 13 wherein in a first gain mode, a first plurality of the RF stage transistors is activated and in a second gain mode, lower than the first gain mode, a second plurality of the RF stage transistors is activated, the number of activated RF stage transistors being less in the second gain mode than the first gain mode.

### Claim 15 (depends on 11)

The semiconductor die of claim 11 wherein the tailored adjustment is configured so that the total impedance presented to the input RF signal is 50Ω for individual gain modes.

### Claim 16 (depends on 11)

The semiconductor die of claim 11 wherein the tailored impedance adjustment is further configured to result in a fixed real impedance for the total input impedance.

### Claim 17

A wireless device comprising:
an antenna configured to at least receive a radio-frequency (RF) signal;
an RF amplifier in communication with the antenna and configured to provide a plurality of gain modes to generate an amplified RF signal, the RF amplifier including a power supply configured to provide a source current that differs for individual gain modes; the RF amplifier further including a gain stage including an RF stage transistor and a cascode stage transistor, the gain stage configured to receive the source current from the power supply to operate the gain stage at corresponding gain modes, a total input impedance presented to an input RF signal associated with a transconductance of the RF stage transistor; and the RF amplifier further including an impedance adjustment circuit coupled to the gain stage and configured to provide a tailored adjustment that compensates for changes in the transconductance using switchable inductive elements; and
a transceiver configured to process the amplified RF signal.

### Claim 18 (depends on 17)

The wireless device of claim 17 wherein the wireless device is a cellular phone configured to utilize the plurality of gain modes in receive operations.

### Claim 19 (depends on 17)

The wireless device of claim 17 wherein the tailored adjustment is configured so that the total impedance presented to the input RF signal is 50Ω for individual gain modes.

### Claim 20 (depends on 17)

The wireless device of claim 17 wherein the tailored impedance adjustment is further configured to result in a fixed real impedance for the total input impedance.