Patent ID: 8848947

Claim:
A mobile device comprising: a processor for controlling operation of the mobile device; a communication subsystem coupled to the processor; a microphone system for generating a pre-amplified microphone signal to be encoded and transmitted over a network by the communication subsystem, the microphone system comprising: a microphone comprising an acoustic sensor for generating a microphone signal representative of an acoustic signal detected in a vicinity of the microphone, and an intrinsic pre-amplifier having an input terminal coupled to the acoustic sensor to receive the microphone signal and configured to generate the pre-amplified microphone signal at an output terminal of the intrinsic pre-amplifier; a current source coupled to the intrinsic pre-amplifier for supplying the intrinsic pre-amplifier with a pre-amplifier bias current; and a current source controller coupled to the current source, the current source controller configured to control the pre-amplifier bias current supplied by the current source based on a measured operating characteristic of the intrinsic pre-amplifier to maintain the intrinsic pre-amplifier at a predetermined bias point at which the intrinsic pre-amplifier generates the pre-amplified microphone signal by amplification of the microphone signal wherein the current source comprises one or more voltage-controlled current sources configured to generate the pre-amplifier bias current in response to a voltage control signal generated by the current source controller based on the measured operating characteristic; and wherein the current source controller comprises: a feedback sensor coupled to the output terminal of the intrinsic pre-amplifier for comparing the measured operating characteristic of the intrinsic pre-amplifier against the predetermined bias point; a variable voltage supply coupled to the feedback sensor and the current source, the variable voltage supply configured to generate the voltage control signal for the current source by sweeping the voltage control signal across a range of set voltages until the feedback sensor indicates that the measured operating characteristic of the intrinsic pre-amplifier has achieved the predetermined bias point; a sweep sequencer coupled to the variable voltage supply and configured, upon detecting power on of the mobile device, to rest the voltage control signal to an initial set voltage and initiate the sweeping of the voltage control signal across the range of set voltages a digital counter for outputting a digital count value, the digital counter configured to reset the digital count value to an initial value when the sweeping of the voltage control signal is initiated, and to hold the digital count value at a final value when the measured operating characteristic of the intrinsic pre-amplifier has achieved the predetermined bias point; and a digital to analog converter coupled to the digital counter for converting the digital count value outputting by the digital counter into the voltage control signal.