bias Current Ic in PNP

Discussion in 'Homework Help' started by freeze777, Apr 1, 2015.

Determine the quiescent collector current of the pnp transistor

  1. question is wrong...

    0 vote(s)
    0.0%
  2. bias resistor value wrong

    0 vote(s)
    0.0%
Multiple votes are allowed.
  1. freeze777

    Thread Starter New Member

    Apr 1, 2015
    3
    0
    I was asked to find the quiescent collector current of the pnp transistor Q2.
    I got stuck in between a point where the base of pnp connected to the collector of npn.
    The npn transistor has bias current Ic=2 mA. which cause a Vc=4.3 V. But this will cause a drop of 1.4 V at the Base emitter of pnp...!! and i felt i am goin wrong somwhere
     
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,650
    632
    But the base-emitter voltage of the PNP is given as 0.7V. Consider the likely purpose of connecting the collector of the PNP to the emitter of the NPN.
     
  3. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    As beta is infinity, the base current of both transistors is zero. Makes the calculation easy.
    In fact, no calculator needed!

    Start by considering the resistors biasing the base of Q1. What is the current in these resistors? What is Q1 base voltage?
     
  4. freeze777

    Thread Starter New Member

    Apr 1, 2015
    3
    0
    Well... found my mistake.... i considered the sum of pnp collector current and npn emitter current as the emitter current of npn.
    Finally the answer is 1 mA :)
     
  5. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    What is the collector current for Q1 ?
     
  6. freeze777

    Thread Starter New Member

    Apr 1, 2015
    3
    0
    Both has bias currents Ic of 1mA
     
  7. DickCappels

    Moderator

    Aug 21, 2008
    2,650
    632
    Good job!
     
    freeze777 likes this.
Loading...