Patent ID: 8705752

Claim:
A noise reduction circuit, comprising: a filter comprising two grounding resistors and two off-chip coupling capacitors coupled to an audio signal source; a programmable gain amplifier (PGA) coupled to the filter, the PGA having an input that allows a gain of the PGA to be adjusted in response to a control signal received on the input, wherein the PGA is formed by a cascade of a transconductance amplifier and a transimpedance amplifier based on the control signal; a synchronized switch pair configured to couple or uncouple an output of the transconductance amplifier to an input of the transimpedance amplifier based on the control signal; an analog-to-digital converter (ADC) coupled to the PGA; and a base band digital signal processor (DSP) coupled to the ADC, the base band DSP adapted to provide the control signal for the input to the PGA, based on a noise level of an output of the PGA.