# US 10,312,867 B2 · Methods, modules and devices for detecting a saturation condition of a power amplifier

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- Number: US 10,312,867 B2
- Document ID: US10312867B2
- Status: Granted
- Kind: B2
- Application number: 15/641,309
- Filed: 2017-07-04
- Published: 2017-10-19
- Granted: 2019-06-04
- Earliest claimed: 2014-12-30
- Assignees: Skyworks Solutions, Inc.
- Applicants: Skyworks Solutions, Inc.
- Inventors: David Steven Ripley; Philip John Lehtola
- Web page: https://patentgrep.com/patent/US10312867B2

## CPC

- H03F 1/32: Modifications of amplifiers to reduce non-linear distortion (by negative feedback H03F1/34)
- H03F 1/0211: {with control of the supply voltage or current}
- H03F 1/0227: {using supply converters}
- H03F 1/22: by use of cascode coupling, i.e. earthed cathode or emitter stage followed by earthed grid or base stage respectively
- H03F 1/56: Modifications of input or output impedances, not otherwise provided for
- H03F 3/19: with semiconductor devices only
- H03F 3/191: Tuned amplifiers (H03F3/193, H03F3/195 take precedence)
- H03F 3/21: with semiconductor devices only {(H03F3/245 takes precedence)}
- H03F 3/24: of transmitter output stages
- H03F 3/245: {with semiconductor devices only}
- H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)}
- H04B 1/40: Circuits
- H04L 25/0278: {Arrangements for impedance matching}
- H04L 27/04: Modulator circuits; Transmitter circuits
- H03F 1/0261: {with control of the polarisation voltage or current, e.g. gliding Class A}
- H03F 1/30: Modifications of amplifiers to reduce influence of variations of temperature or supply voltage {or other physical parameters (in differential amplifiers H03F3/45479)}
- H03F 1/302: {in bipolar transistor amplifiers (H03F1/303, H03F1/305, H03F1/307 take precedence)}
- H03F 2200/171: A filter circuit coupled to the output of an amplifier
- H03F 2200/451: the amplifier being a radio frequency amplifier
- H03F 2200/462: the current being sensed
- H03F 2200/555: A voltage generating circuit being realised for biasing different circuit elements
- H03F 2200/78: A comparator being used in a controlling circuit of an amplifier
- H03G 3/3042: {in modulators, frequency-changers, transmitters or power amplifiers}
- H04B 2001/0408: {with power amplifiers}
- H03F: AMPLIFIERS
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H03G: CONTROL OF AMPLIFICATION

## Abstract

The present disclosure relates to methods, modules and devices for detecting and preventing occurrence of a saturation state in a power amplifier. A method is disclosed for detecting a saturation condition of a power amplifier, including monitoring a first base current of a first transistor of a cascade transistor pair of the power amplifier and a second base current of a second transistor of the cascade transistor pair. The method can also include generating a current ratio based on comparing the first base current and the second base current. The method can further include determining if the current ratio exceeds or satisfies a threshold value and modifying one or more operating characteristics of the power amplifier in accordance with a determination that the current ratio exceeds or satisfies the threshold value.

## Claims

### Claim 1

A method for detecting a saturation condition of a power amplifier, comprising:
monitoring a first base current of a first transistor of a cascode transistor pair of the power amplifier and a second base current of a second transistor of the cascode transistor pair;
generating a current ratio based on comparing the first base current and the second base current;
determining if the current ratio exceeds or satisfies a threshold value; and
modifying one or more operating characteristics of the power amplifier in accordance with a determination that the current ratio exceeds or satisfies the threshold value.

### Claim 2 (depends on 1)

The method of claim 1 wherein modifying the one or more operating characteristics of the power amplifier includes modifying at least one operating characteristic based on the current ratio.

### Claim 3 (depends on 1)

The method of claim 1 wherein comparing the first base current and the second base current is performed by a current comparator coupled to the power amplifier.

### Claim 4 (depends on 1)

The method of claim 1 wherein a value of the current ratio indicates that the power amplifier is in a compression state.

### Claim 5 (depends on 1)

The method of claim 1 wherein modifying of the one or more operating characteristics is performed by a saturation controller coupled to the power amplifier.

### Claim 6 (depends on 5)

The method of claim 5 wherein modifying one or more operating characteristics of the power amplifier includes modifying a supply voltage to the power amplifier.

### Claim 7 (depends on 5)

The method of claim 5 wherein modifying one or more operating characteristics of the power amplifier includes modifying a radio-frequency signal to the power amplifier.

### Claim 8 (depends on 5)

The method of claim 5 wherein modifying one or more operating characteristics of the power amplifier includes modifying a load impedance at an output of the power amplifier.

### Claim 9 (depends on 5)

The method of claim 5 wherein modifying one or more operating characteristics of the power amplifier includes maintaining the power amplifier out of a state of saturation.

### Claim 10

A power amplifier module comprising:
a power amplifier including a cascode transistor pair, the cascode transistor pair including a first transistor and a second transistor;
a current comparator configured to compare a first base current of the first transistor and a second base current of the second transistor to obtain a comparison value; and
a saturation controller configured to supply a first reference signal to a first operating module based on the comparison value, and configured to supply a second reference signal to a second operating module based on the comparison value.

### Claim 11 (depends on 10)

The power amplifier module of claim 10 wherein the first operating module includes a voltage converter configured to modify a supply voltage provided to the power amplifier based at least in part on the first reference signal.

### Claim 12 (depends on 11)

The power amplifier module of claim 11 wherein the saturation controller includes a digital-to-analog converter used to provide the first reference signal to the voltage converter.

### Claim 13 (depends on 10)

The power amplifier module of claim 10 wherein the second operating module includes a radio-frequency attenuator configured to modify an amplitude of a radio-frequency input signal supplied to the power amplifier based at least in part on the second reference signal.

### Claim 14 (depends on 13)

The power amplifier module of claim 13 wherein the radio-frequency attenuator is a digital attenuator.

### Claim 15 (depends on 13)

The power amplifier module of claim 13 wherein the radio-frequency attenuator is an analog attenuator.

### Claim 16 (depends on 10)

The power amplifier module of claim 10 wherein the saturation controller is further configured to supply a third reference signal to a third operating module based on the comparison value, the third operating module including an impedance matching network configured to modify a load impedance of a load line in electrical communication with the power amplifier based at least in part on the third reference signal.

### Claim 17 (depends on 16)

The power amplifier module of claim 16 wherein the saturation controller is further configured to reduce compression of the power amplifier by modifying the load impedance of the load line.

### Claim 18 (depends on 17)

The power amplifier module of claim 17 wherein the impedance matching network includes a switch capacitor and the saturation controller causes one or more switches of the switch capacitor to be opened or closed to modify the load impedance.

### Claim 19 (depends on 10)

The power amplifier module of claim 10 wherein the saturation controller is further configured to maintain the power amplifier out of saturation based at least in part on the comparison value.

### Claim 20

A wireless device comprising:
an antenna configured to at least transmit a signal from a transceiver, the signal being based at least in part on a radio frequency input signal supplied to a power amplifier of the transceiver; and
the transceiver including a power amplifier module, the power amplifier module including the power amplifier, a current comparator, and a saturation controller, the power amplifier including a cascode transistor pair, the cascode transistor pair including a first transistor and a second transistor, the current comparator configured to compare a base current of the first transistor and a base current of the second transistor to obtain a comparison value, the saturation controller configured to supply a first reference signal to a first operating module based on the comparison value, and configured to supply a second reference signal to a second operating module based on the comparison value.