Variable bias control for switch mode RF amplifier

• US 6,323,731 B1
• Filed: 10/06/2000
• Issued: 11/27/2001
• Est. Priority Date: 10/06/2000
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Tropion Incorporated Corporation
• Inventors: McCune, Jr., Earl W.
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Choe, Henry
• Application Number:
  US09/684,496
• Time in Patent Office: 417 Days
• Field of Search: 330/207.A, 330/251, 330/296, 330/297
• US Class Current: 330/251
• CPC Class Codes: H03F 1/0227 using supply converters
• CPC Class Codes: H03F 1/0261 with control of the polarisation voltage or current, e.g. gliding Class A
• CPC Class Codes: H03F 1/3205 in field-effect transistor amplifiers
• CPC Class Codes: H03F 1/3223 using feed-forward H03F1/3211 takes precedence
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers

Abstract

The present invention, generally speaking, provides for the effective use of dynamic bias control in a switch-mode RF amplifier to achieve an output signal having wide dynamic range. In one aspect, a method is provided of amplifying an RF signal to produce a variable output signal using an amplifier including a final amplification stage having a control terminal. The method includes: applying to the control terminal of the final amplification stage a drive signal and a bias signal; and varying the bias signal as a function of a desired output power of the variable output signal. The drive signal and the bias signal together cause the final amplification stage to be driven repeatedly between two states, a hard-on state and a hard-off state, without operating in a linear operating region for an appreciable percentage of time, and the final amplification stage is controlled without continuous or frequent measurement and feedback adjustment of the variable output signal.

Claims

1. A method of amplifying an RF signal to produce a variable output signal using an amplifier including a final amplification stage having a control terminal, the method comprising the steps of:

applying to the control terminal of the final amplification stage a drive signal and a bias signal, wherein the drive signal and the bias signal together cause the final amplification stage to be driven repeatedly between two states, a hard-on state and a hard-off state, without operating in a linear operating region for an appreciable percentage of time, the final amplification stage being controlled without continuous or frequent measurement and feedback adjustment of said variable output signal; and

varying the bias signal and the drive signal as a function of a desired output power;

wherein the final amplification stage receives a supply voltage, further comprising varying the supply voltage to control amplitude of the variable output signal.

2. The method of claim 1, wherein the bias signal and the drive signal are decreased as said desired output power decreases.

3. An amplifier having a variable output signal, comprising:

a final amplification stage having a control terminal;

a driver stage preceding the final amplification stage, the driver stage producing a drive signal applied to the control terminal of the final amplification stage; and

control circuit producing a variable bias signal, also applied to the control terminal of the final amplification stage, the control circuitry varying the bias signal as a function of a desired output power of the variable output signal;

wherein the drive signal and the bias signal together cause the final amplification stage to be driven repeatedly between two states, a hard-on state and a hard-off state, without operating in a linear operating region for an appreciable percentage of time, the final amplification stage being controlled without continuous or frequent measurement and feedback adjustment of said variable output signal; and

wherein the final amplification stage receives a supply voltage, further comprising circuitry for varying the supply voltage to control amplitude of the variable output signal.

4. The apparatus of claim 3, wherein the control circuitry decreases said bias signal as said desired output power decreases.

5. The apparatus of claim 3, wherein the driver stage has a control terminal to which a fixed bias signal is applied.

6. The apparatus of claim 5, wherein the drive stage receives a driver supply voltage, further comprising driver control circuitry for varying the driver supply voltage to control amplitude of the drive signal.