Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Pnp transistor

  1. Sep 14, 2005 #1
    Consider a pnp transistor with [tex]{v_{EB}=0.7V[/tex] and [tex]{i_{E}=1mA[/tex]. Let the base be grounded and the emitter be fed by a 2 mA constant current source , and the collector be connected toa -5V supply through a 1-Killoohms resistance. if the temperature increases by 30 degree celsius, find the change in emitter and collector voltages. neglect the effect of [tex]{I_{CBO}[/tex]

    Now my dear friends! the problem im getting here is this that we are given to values for the emitter current. I just cant get how to use both of them to get the right answer. Secondly what temperature relationship should i use. I can tell u the right answers as well

    Ans: -60 mV and 0V

    please help me as soon as possible.

    Thanks in advance
  2. jcsd
  3. Sep 14, 2005 #2
    I noticed also that you are given 2 values for emitter current. It sounds like a pointless question to me.
  4. Sep 14, 2005 #3


    User Avatar

    I think the question is also missing relevant information. As I recall the temperature dependance of the current gain is mostly due to the fact the emitter injection efficiency changes with temp. To really figure it out I think you need to know about the doping of the transistor.

    From looking at the answer I'll bet you're supposed to apply some random rule of thumb given to you by your instructor because we often use -2mV/C here for envelope calculations. But given the contradicting information in my opinion it's really just an ill formed question.
  5. Sep 14, 2005 #4
    dont u think that the first value of the emitter current is actually that of the collector current. May be there is some misprinting in the book. If yes then what are ur ideas
  6. Sep 14, 2005 #5
    Unless the transistor has an incredibly low beta then I doubt it.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Pnp transistor
  1. Pnp transistor help (Replies: 9)

  2. Pnp npn transistors (Replies: 25)