ADAPTIVE GATE CHARGING CIRCUIT FOR POWER FET

摘要

PURPOSE: To minimize a current drain from a charge supply source by feeding back the whole emitter current of a current mirror transistor(Tr) to its base and driving the current mirror TR as a diode. CONSTITUTION: When a current is not required for the gate of a power FET 14 in an adaptive gate charging circuit 10 connected between a charge pump 12 and the FET 14, the whole emitter current of a current mirror TrQ26 is fed back to its base. The TrQ26 is driven as a diode and a current drain on the pump 12 is simply reduced to 3μA. A leakage current (about 27μA) necessary for holding the gate of the FET 14 at a high state is supplied from the pump 12 through the TrQ26. Thereby the effective current ratio of the TrQ26 is automatically adapted to the necessary degree of the FET 14 and a current drain from the pump 12 can be minimized.