Power Transistor Module Help!!!

Discussion in 'The Projects Forum' started by bmrdixon, Apr 1, 2010.

  1. bmrdixon

    Thread Starter New Member

    Mar 18, 2010
    I have a QM300HA-24 power transistor. I had another transistor driving the base of the bigger transistor with 14.8vdc. I have 23vdc into the collector. Why do i have round 20vdc coming out of the emitter??...i need 14 or so....does the internal diode across the collector / emitter have something to do with it??:eek: After more testing i found out that 20v is also on the base of the the bigger transistor feeding back into the emitter of the smaller transistor..whats up??
    Last edited: Apr 1, 2010
  2. SgtWookie


    Jul 17, 2007
    Post the schematic of your circuit. It will help us to help you much more quickly and accurately.
  3. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    You should fit resistors between base & emitter on each transistor.

    This bypasses any circuit leakage and ensures the transistors only conduct when they are supposed to.

    The resistor value depends on the circuit, it could be anything from 10K for a small signal transistor down to 100 Ohms for a power transistor.

    Try something like 4k7 on the driver and 470 Ohms on the power device.