Granted Patent B2

US 7,843,271 · App. 11/389,778 · Granted Nov 30, 2010

Abstract

Claims (29)

1. An audio amplifier comprising:

an output stage for generating an output stage voltage in response to an input signal and an output stage quiescent current;

a controlled current source, operatively coupled to the output stage, for controlling the output stage quiescent current in response to a quiescent current signal during a start-up cycle;

a ramp generator, operatively coupled to the output stage, for generating a ramp signal during the start-up cycle;

wherein the output stage, based on the ramp signal, ramps the output stage voltage from a supply voltage to a quiescent voltage; and

a signal operatively coupled to the ramp generator, for generating the quiescent current signal as a function of the ramp signal.

2. The audio amplifier of claim 1 wherein the quiescent current signal is a nonlinear function of the ramp signal.

3. An audio amplifier comprising:

an output stage for generating an output stage voltage in response to an input signal and an output stage quiescent current;

a controlled current source, operatively coupled to the output stage, for controlling the output stage quiescent current in response to a quiescent current signal during a start-up cycle; and

wherein the output stage quiescent current has a magnitude and the output stage voltage ramps during the start-up cycle and wherein the controlled current source controls the magnitude of the output stage quiescent current to increase monotonically with the ramping of the output stage voltage during the start-up cycle.

4. The audio amplifier of claim 1 wherein the controlled current source produces an offset current during the start-up cycle when the output stage voltage is ground.

5. The audio amplifier of claim 1 wherein the controlled current source includes a current mirror circuit.

6. The audio amplifier of claim 1 wherein the output stage and the controlled current source are implemented on an integrated circuit.

7. An method comprising:

controlling an output stage quiescent current of an audio amplifier during a start-up cycle and in response to a quiescent current signal;

ramping an output stage voltage of the audio amplifier from a supply voltage to a quiescent voltage during the start-up cycle; and

wherein the quiescent current signal is a function of the output stage voltage during the start-up cycle.

8. The method of claim 7 wherein the step of controlling the output stage quiescent current includes controlling the output stage quiescent current to an offset current during the start-up cycle when the output stage voltage is the supply voltage.

9. The method of claim 7 wherein the quiescent current signal is a nonlinear function of the output stage voltage during the start-up cycle.

10. The method of claim 7 wherein the output stage quiescent current signal has a magnitude that increases monotonically with ramping output stage voltage during the start-up cycle.

11. An method for starting an audio amplifier comprising:

applying an output stage quiescent current to an output stage of the audio amplifier;

ramping an output voltage of the output stage from a supply voltage to a quiescent voltage;

increasing a magnitude of the output stage quiescent current to an operating current level;

applying an input voltage to the audio amplifier after the output voltage has reached the quiescent voltage and the magnitude of the output stage quiescent current has reached the operating current level; and

wherein the step of increasing the magnitude of the output stage quiescent current includes controlling the magnitude of the output stage quiescent current as a function of the output stage voltage.

12. The method of claim 11 wherein the step of increasing the magnitude of the output stage quiescent current includes controlling the magnitude of the output stage quiescent current as a non-linear function of the output stage voltage.

13. The method of claim 11 wherein the step of increasing the magnitude of the output stage quiescent current includes increasing the magnitude of the output stage quiescent current monotonically with ramping output stage voltage.

Assignments (9)