Drive circuit for driving cascode bipolar-MOS circuit

Claim 1

A drive circuit for driving a cascode bipolar-MOS circuit having a first bipolar transistor and a MOS transistor coupled to each other through a cascode connection or series, said bipolar-MOS circuit being inserted in a current path to open and close said current path in response to a control signal supplied from the exterior of said cascode bipolar-MOS circuit to a gate of said MOS transistor, said drive circuit comprising: a second bipolar transistor coupled to said first bipolar transistor through a Darlington connection; current supply circuit including a D.C. power source and a first capacitor connected in series through a connection node which is coupled to a base of said second bipolar transistor for supplying a base current to said base of said second bipolar transistor wherein said first capacitor supplies a discharge current as an over shoot current of said second bipolar transistor to turn on said second bipolar transistor; a diode inserted between said base of said second bipolar transistor and a base of said first bipolar transistor for allowing a current to pass through said diode only in a direction from said base of said first bipolar transistor to said base of said second bipolar transistor; and a Zener diode having a cathode coupled to said base of said second bipolar transistor and an anode coupled to a source electrode of said MOS transistor.