DARLINGTON CONNECTION POWER TRANSISTOR

PURPOSE:To decrease the reverse bias voltage by connecting a diode in opposite polarity between an emitter of a pre-stage transistor (TR)-of Darlington connection and a module input terminal so as to quicken the turnoff. CONSTITUTION:The pre-stage TR 11 and the post-stage TR 12 are connected in Darlington to form a power TR and to constitute a module 1A. A base clamp diode D13, anti-parallel diodes D14, D15 and a speed up diode D16 are connected respectively between a collector, a base of the TR 11 and the input terminal of the module 1A. In giving a load current Ic to a load 31 of a main circuit 3, a switch SW21 of a drive circuit 2 is turned on and a switch SW 22 is turned off. In turning on the SW 21 and turning off the SW 22 to turn off the module 1A, the reverse bias base current IB2 flows through a loop comprising power supply 23 resistor 17 between base and emitter of TR 12 one diode D16zeta SW 22 to turn off the module 1A at a high speed.