On the topology and number of operating points of MOSFET circuits

Abstract

This paper reviews previous theory regarding the existence and uniqueness of dc operating points possessed by bipolar transistor circuits and applies it to MOSFET circuits. Two primary results are presented. First, it is shown that certain previous topological results regarding the uniqueness of dc operating points for bipolar junction transistor and JFET circuits do not strictly hold for MOSFET circuits. Second, a two-transistor MOSFET circuit that possesses five operating points is presented. This circuit is contrasted with previous results that indicate that two-transistor BJT circuits can possess no more than three operating points. The existence of this MOSFET circuit is justified by showing how the previous result breaks down in the case of circuits containing MOSFETs.