IGBT Reverse Transfer Dynamic Capacitance

Abstract

Small-signal capacitance in every datasheet of insulated gate bipolar transistor (IGBT) is not accurate for understanding IGBT's switching because the bipolar current in the device creates abnormal depletion profiles. IGBT's reverse transfer dynamic capacitance is extracted for the first time with a five-contact method. While small-signal capacitance does not allow any current flow in the drift region due to the ground gate, the dynamic capacitance is the output of the time-dependent bipolar carriers during the inductive switching. For this reason, the magnitude and the shape of the dynamic capacitance are quite different from the small-signal capacitance found in most of the commercial datasheet. The discrepancy between the dynamic C GC and the small-signal C GC raises a fundamental question of whether the small-signal C GC in the datasheet is useful for considering the device's dynamic performance.