Patent ID: 7961049
Filing Date: 2011-06-14
Classification: H03F

Abstract:
1. An amplifier circuit, comprising: a reference connection and a first and second power supply connection for supplying voltages on mutually opposite sides of a voltage on the reference connection; an amplifier stage, comprising an amplifier transistor with a gate coupled to an input of the amplifier stage, a source coupled to the reference connection and a drain coupled to the first power supply connection; and a bias stage, comprising a bias transistor, a drain resistance and a source resistance, the bias transistor having a gate coupled to the second power supply connection, a source coupled to the second power supply connection via the source resistance, so that a voltage drop over the source resistance at least partly defines a gate source voltage of the bias transistor and a drain coupled to the reference connection via the drain resistance and to the gate of the amplifier transistor; wherein the bias stage comprises a further resistance, coupled from a circuit node carrying a voltage with a same polarity relative to the second power supply connection as the first power supply connection, to a node between the source of the bias transistor and the source resistance, for injecting current through the source resistance in addition to current originating from the drain resistance.