Apparatus and methods for biasing power amplifiers

• US 9,362,870 B2
• Filed: 07/31/2014
• Issued: 06/07/2016
• Est. Priority Date: 08/01/2013
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Lam, Lui
• Primary Examiner(s): NGUYEN, HIEU P
• Application Number:
  US14/448,793
• Publication Number:
  US 20150035605A1
• Time in Patent Office: 677 Days
• Field of Search: 330/285, 330/296, 330/289, 330/51
• US Class Current: 1/1
• CPC Class Codes: H03F 1/0266 by using a signal derived from the input signal
• CPC Class Codes: H03F 1/302 in bipolar transistor amplifiers H03F1/303, H03F1/305, H03F1/307 take precedence
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 2200/18 the bias of the gate of a FET being controlled by a control signal
• CPC Class Codes: H03F 2200/336 A I/Q, i.e. phase quadrature, modulator or demodulator being used in an amplifying circuit
• CPC Class Codes: H03F 2200/387 A circuit being added at the output of an amplifier to adapt the output impedance of the amplifier
• CPC Class Codes: H03F 2200/408 the output amplifying stage of an amplifier comprising three power stages
• CPC Class Codes: H03F 2200/451 the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2203/21131 the input bias voltage of a power amplifier being controlled, e.g. by a potentiometer or an emitter follower
• CPC Class Codes: H03F 3/19 with semiconductor devices only
• CPC Class Codes: H03F 3/21 with semiconductor devices only H03F3/245 takes precedence
• CPC Class Codes: H03F 3/211 using a combination of several amplifiers H03F3/60 takes precedence
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• CPC Class Codes: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

Apparatus and methods for biasing power amplifiers are disclosed herein. In certain implementations, a power amplifier system includes a power amplifier and a bias circuit that generates a bias voltage for biasing the power amplifier. The bias circuit includes an amplifier, a current source for generating a reference current, and a reference transistor having a current therethrough that changes in relation to the bias voltage. The amplifier can control the bias voltage based on an error current corresponding to a difference between the reference current and the current through the reference transistor. The amplifier can be used to control the bias voltage such that the reference current and the current through the reference transistor are substantially equal.

Claims

1. A power amplifier system comprising:

a power amplifier configured to receive a radio frequency (RF) input signal, and to amplify the RF input signal to generate an RF output signal, the power amplifier further configured to receive a bias voltage that biases the power amplifier; and

a bias circuit configured to generate the bias voltage, the bias circuit including a bias circuit amplifier, a variable current source configured to generate a reference current, and a reference transistor having a current therethrough that changes in relation to the bias voltage, the bias circuit amplifier configured to control the bias voltage based on an error current corresponding to a difference between the reference current and the current through the reference transistor.

2. The power amplifier system of claim 1 wherein the bias circuit amplifier includes a transimpedance amplifier.

3. The power amplifier system of claim 1 wherein the bias circuit is configured to receive an enable signal, the bias circuit configured to selectively turn on or off the power amplifier based on a state of the enable signal.

4. The power amplifier system of claim 3 wherein at least one of the bias circuit amplifier or the variable current source turn on or off based on the state of the enable signal.

5. The power amplifier system of claim 1 further comprising a control circuit configured to control the reference current generated by the variable current source to compensate for temperature variation.

6. A power amplifier system comprising:

a power amplifier configured to receive a radio frequency (RF) input signal, and to amplify the RF input signal to generate an RF output signal, the power amplifier further configured to receive a bias voltage that biases the power amplifier, the power amplifier including a bipolar power amplifier transistor including a base that receives the bias voltage;

a bias circuit configured to generate the bias voltage, the bias circuit including a bias circuit amplifier, a current source configured to generate a reference current, and a reference transistor having a current therethrough that changes in relation to the bias voltage, the bias circuit amplifier configured to control the bias voltage based on an error current corresponding to a difference between the reference current and the current through the reference transistor; and

an isolation circuit electrically connected between the base of the bipolar power amplifier transistor and an output of the bias circuit amplifier.

7. The power amplifier system of claim 6 further comprising an array of transistor elements, the bipolar power amplifier transistor implemented by a plurality of transistor elements of the array, the reference transistor implemented by one or more transistor elements of the array.

8. The power amplifier system of claim 6 wherein the bipolar power amplifier transistor and the reference transistor are separated by a distance of less than about 9 μ

m to provide thermal coupling.

9. The power amplifier system of claim 6 wherein the bias circuit amplifier includes a transimpedance amplifier.

10. The power amplifier system of claim 6 wherein the bias circuit is configured to receive an enable signal, the bias circuit configured to selectively turn on or off the power amplifier based on a state of the enable signal.

11. The power amplifier system of claim 10 wherein at least one of the bias circuit amplifier or the current source turn on or off based on the state of the enable signal.

12. A power amplifier system comprising:

a power amplifier configured to receive a radio frequency (RF) input signal, and to amplify the RF input signal to generate an RF output signal, the power amplifier further configured to receive a bias voltage that biases the power amplifier, the power amplifier including a plurality of power amplifier stages arranged in a cascade; and

a bias circuit configured to generate the bias voltage, the bias circuit including a bias circuit amplifier, a current source configured to generate a reference current, and a reference transistor having a current therethrough that changes in relation to the bias voltage, the bias circuit amplifier configured to control the bias voltage based on an error current corresponding to a difference between the reference current and the current through the reference transistor.

13. The power amplifier system of claim 12 wherein the current source is a variable current source.

14. The power amplifier system of claim 12 wherein the bias circuit amplifier includes a transimpedance amplifier.

15. The power amplifier system of claim 12 wherein the bias circuit is configured to receive an enable signal, the bias circuit configured to selectively turn on or off the power amplifier based on a state of the enable signal.

16. The power amplifier system of claim 15 wherein at least one of the bias circuit amplifier or the current source turn on or off based on the state of the enable signal.

17. A power amplifier bias circuit for biasing a power amplifier, the power amplifier bias circuit comprising:

a bias circuit amplifier;

a variable current source configured to generate a reference current; and

a reference transistor having a current therethrough that changes in relation to a bias voltage, the bias circuit amplifier configured to control the bias voltage based on an error current corresponding to a difference between the reference current and the current through the reference transistor.

18. The power amplifier bias circuit of claim 17 wherein the bias circuit amplifier includes a transimpedance amplifier.

19. The power amplifier bias circuit of claim 17 further comprising a control circuit configured to control the reference current generated by the variable current source to compensate for temperature variation.

20. The power amplifier bias circuit of claim 17 wherein at least one of the bias circuit amplifier or the variable current source are turned on or off using an enable signal.