Extraction of Charge Partitioning in Multi-Terminal Devices with AC Analysis Approach

Low frequency, small-signal ac analysis of multi-terminal devices holds the promise of providing accurate charge partitioning information, which is of major concern to circuit designers. However, simple interpretation of the imaginary part of y -parameters as purely capacitive often leads to unphysical results when there are significant DC terminal currents. Although these 'abnormal' results in MOSFETs can be explained by the current sources in the equivalent circuit, extraction of charge partitioning from the conventional ac analysis is made impossible. A novel scheme is proposed using modified Jacobian in ac simulation for this purpose. Implementation of this scheme in PISCES leads to the results which eliminate negative capacitances while giving physically sound charge-partitioning information.