Apparatus and method for pop-and-click suppression with fast turn-on time

Patent 7164312 Issued on January 16, 2007. Estimated Expiration Date:

August 2, 2024. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

Patent References

3795876

Muting circuit with operational amplifier
Patent #: 4288753
Issued on: 09/08/1981
Inventor: Babano

Electrical filter
Patent #: 4733205
Issued on: 03/22/1988
Inventor: Hughes

Rapid slewing filter
Patent #: 4739189
Issued on: 04/19/1988
Inventor: Kellogg

Audio amplifier turn-off control circuit Patent #: 5703528
Issued on: 12/30/1997
Inventor: Nebuloni, et al.

Inventors

Assignee

National Semiconductor Corporation

Application

No. 10910691 filed on 08/02/2004

US Classes:

330/9, WITH PERIODIC SWITCHING INPUT-OUTPUT (E.G., FOR DRIFT CORRECTION)381/94.5, Soft switching, muting, or noise gating333/14, AMPLITUDE COMPRESSION AND EXPANSION SYSTEMS (I.E., COMPANDERS)330/51, COMBINED WITH AUTOMATIC AMPLIFIER DISABLING SWITCH MEANS333/172, RC or RL type327/555, Selective type signal filtering (e.g., from low pass to high pass, etc.)361/18Voltage regulator protective circuits

Examiners

Primary: Pascal, Robert
Assistant: Wong, Allen

Attorney, Agent or Firm

International Class

H03F 1/02

Abstract

A circuit for audio amplification includes an amplifier and a first input resistor. The amplifier is arranged to provide an amplifier output signal that is based, in part, on a capacitively-coupled audio input signal. The capacitively-coupled audio input signal is based, in part, on an input RC value. The input RC value is given by the input capacitance times the input resistance. The input resistance is reduced during the turn-on in order to achieve a fast turn-on time with minimal pop-and-click noise. Also, the input resistance is increased to its normal value after the turn-on so that full audio fidelity is substantially maintained during normal operation.