Patent ID: 7634096

Claim:
An amplifier circuit for a capacitive transducer, comprising: a preamplifier adapted to receive a transducer signal through a preamplifier input and provide an amplified transducer signal at a preamplifier output; a non-linear device including a pair of cross-coupled semiconductor devices, wherein a first terminal of one of the semiconductor devices is operatively coupled to the input of the preamplifier and a second terminal of the semiconductor device is operatively coupled to a bias control means, wherein each of the semiconductor devices is selected from the group consisting of a semiconductor diode and a transistor; and reference setting means adapted to provide a predetermined reference measure associated with a DC bias setting of the preamplifier, wherein the bias control means is responsive to a difference between the predetermined reference measure and the DC bias setting of the preamplifier to set a DC operating point of the preamplifier input.