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PNP switch question

  1. Jun 26, 2011 #1
    In a BJT PNP switch, why does the base voltage need to go to zero to turn it on.
    If Vee is 5V, the base has to be 5-0.7v to make the BE fwd biased.
     
  2. jcsd
  3. Jun 26, 2011 #2

    uart

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    "In a BJT PNP switch, why does the base voltage need to go to zero to turn it on." - It doesn't

    "If Vee is 5V, the base has to be 5-0.7v to make the BE fwd biased" - Correct.
     
  4. Jun 26, 2011 #3
    Great. I just simulated it, it works.
    Did the same thing last week, damn thing didn't work. That's why I doubted my understanding.

    The reason I started with PNP switch is bcoz I don't understand why the VCE sat of PNP pass transistor (in voltage regulator) is much less than NPN Vce sat.
     
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