# bias Current Ic in PNP

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

## Determine the quiescent collector current of the pnp transistor

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1. ### freeze777 Thread Starter New Member

Apr 1, 2015
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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

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2. ### DickCappels Moderator

Aug 21, 2008
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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
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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
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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
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What is the collector current for Q1 ?

6. ### freeze777 Thread Starter New Member

Apr 1, 2015
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Both has bias currents Ic of 1mA

7. ### DickCappels Moderator

Aug 21, 2008
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1,082
Good job!

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