Patent ID: 8164385
Filing Date: 2012-04-24
Classification: H03F

Abstract:
1. An amplifier circuit comprising: a first amplifier to amplify an input signal and to output a first amplified signal; a second amplifier to amplify the first amplified signal and to output a second amplified signal; and a feedback circuitry to feed back the second amplified signal to the input of the second amplifier; wherein, the feedback circuitry includes a transistor that receives at least part of the second amplified signal at a drain or collector and a resistor coupled between an emitter/source and the input of the second amplifier, a gate voltage that is different than the second amplified signal is applied to a gate of the transistor, and the transistor and the resistor keep the input level of the second amplifier constant by a source voltage or an emitter voltage obtained by applying a gate bias signal or a base bias signal.