[Please help] Bipolar BD538 how to make sure it is in active region?

Discussion in 'General Electronics Chat' started by watercooler, Apr 8, 2009.

  1. watercooler

    Thread Starter New Member

    Apr 6, 2009
    Hi all, I have designed a simple circuit. It consists of a normal voltage regulator parallel with a PNP bipolar to provide high output current.

    The problem is that the bipolar is very hot.

    I tried to measure the voltage across the emitter-base junction, it is only about 0.3V. The VEC is 7V. The input current Ie is about 0.5A.

    My questions:

    1). Since the Veb is only 0.3V, is the Bipolar turned on or not?

    2). what is the operating region?

    3). is the overheating assocated with the Vbe=0.3??

    thanks a million
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    The data sheet on the transistor will answer the operating condition questions. Can you post up a schematic so we can see what the circuit looks like?