Working of PNP transistor

Discussion in 'General Electronics Chat' started by logearav, Jan 9, 2013.

  1. logearav

    Thread Starter Member

    Aug 19, 2011
    Revered members,
    With the bias setup shown, the positive terminal of the battery repels the emitter holes toward the base, while the negative terminal drives the base electrons toward the emitter. When an emitter hole and a base electron meet, they combine.
    For each electron that combines with a hole, another electron leaves the negative terminal of the battery, and enters the base. At the same time, an electron leaves the emitter, creating a new hole, and enters the positive terminal of the battery.
    Electron leaving the emitter and going to positive terminal is agreeable on account of opposite polarity, but how an electron leaves the negative terminal of battery and enters base region (N region), since they are of same polarity, i.e negatively charged electron and negative N region. Won't there be repulsion?
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Your question is precisely why you need an external bias (voltage difference) to force electrons to flow.

    Your picture would be more understandable if you flip it on the horizontal axis to put positive battery terminal on top (that is the customary way to view schematics).

    Now, back to my first paragraph. No electrons will flow if you simple connect the emitter to the base (whether it is a PNP or an NPN). You need a voltage gradient for the electrons to FLOW. A PNP must have a voltage applied to the base that is 0.6 volts LESS than the voltage going into the emitter.
  3. Veracohr

    Distinguished Member

    Jan 3, 2011
    It's also exactly why voltage is also called "electromotive force".