Patent ID: 6366169
Filing Date: 2002-04-02
Classification: H03F

Abstract:
A class AB output stage, comprising:(a) an amplifying stage adapted to produce first and second output signals which incrementally increase and decrease in response to an incremental increase and decrease, respectively, of a first input signal, and which also incrementally increase and decrease in response to an incremental increase and decrease, respectively, of a second input signal; (b) a pull-up transistor having a first electrode coupled to a first supply voltage conductor, a control electrode coupled to receive the second output signal, and a second electrode coupled to an output terminal, and a pull-down transistor having a first electrode coupled to a second supply voltage conductor, a control electrode coupled to receive the first output signal, and a second electrode coupled to the output terminal; (c) a first feedback circuit including a first current sensing transistor having a control electrode and first electrode connected to the control electrode and first electrode, respectively, of the pull-down transistor and a second electrode coupled to a first control input of the amplifying stage and operative to increase the control electrode voltage of the first current sensing transistor only until its second electrode current increases to a first predetermined value representative of a minimum desired quiescent current in the pull-down transistor, and a second feedback circuit including a second current sensing transistor having a control electrode and first electrode connected to the control electrode and first electrode, respectively, of the pull-up transistor, and a second electrode coupled to a second control input of the amplifying stage and operative to decrease the control electrode voltage of the second current sensing transistor only until its second electrode current increases to a second predetermined value representative of a minimum desired quiescent current in the pull-up transistor.