Patent ID: 6111464
Filing Date: 2000-08-29
Classification: H03F

Abstract:
An amplifier comprisinga) a first power transistor, having a gate and a drain;b) a first sense transistor, having a gate and a drain;c) a first current sensing circuit having an output and coupled to measure a current flow through the drain of the first sense transistor;d) a first bias circuit for generating a first bias voltage, the first bias voltage being coupled to the gate of the first power transistor and to the gate of the first sense transistor, the first bias circuit having a control input coupled to the output of the first current sensing circuit;e) circuitry for coupling an input signal to the gate of the first power transistor;f) circuitry for coupling an output signal from the drain of the first power transistor and for coupling power to the first power transistor; andg) circuitry for coupling power to the first sense transistor;h) wherein the first bias circuit is controlled by the output of the first current sensing circuit so as to maintain a constant current in the first sense transistor, and thereby also maintaining a substantially constant quiescent current in the first power transistor.