Patent ID: 6366170
Filing Date: 2002-04-02
Classification: H03F

Abstract:
An amplifier output stage of an amplifier, said output stage comprising:a first PNP transistor having a collector coupled to an amplifier output and an emitter coupled to a first power supply rail; a second NPN transistor having a base for receiving an input signal and a collector coupled to a base of the first PNP transistor; a first frequency compensation capacitor having one terminal coupled to the collector of the first PNP transistor; and a bias circuit configured to provide a thevenin equivalent bias voltage having an associated output impedance, with the bias circuit coupled to the base of the first PNP transistor so that the first PNP transistor will conduct a desired quiescent current, with the equivalent bias voltage being independent of current flow in the first PNP transistor, and with the output impedance being sufficiently large to form a pole in combination with the frequency compensation capacitor at a frequency beyond a unity-gain frequency of the amplifier.