Another Transistor Circuit Problem

Discussion in 'Homework Help' started by DYLH, Sep 15, 2013.

1. DYLH Thread Starter New Member

Aug 13, 2013
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For this practice problem, I don't see how the answers make sense.

From Ohm's law
V = IR
Vo = Io * 10,000
= 600 (10^-6) * 10,000 = 6

But Vo according to the Answer is 12.

How are they getting 12V and 600uA?

TIA_

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2. Jony130 AAC Fanatic!

Feb 17, 2009
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Have you try to write KCL for Vo node?

3. #12 Expert

Nov 30, 2010
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The example must be wrong. 12V/10K can't possibly result in a current that starts with "6".

4. Jony130 AAC Fanatic!

Feb 17, 2009
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My answer is Vo = 9V and Io = 900μA

DYLH and #12 like this.
5. DYLH Thread Starter New Member

Aug 13, 2013
28
1
Thanks, Jony130.. that's exactly what I got.

6. WBahn Moderator

Mar 31, 2012
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Is this also from Fundamentals of Electric Circuits by Alexander and Sadiku 5th edition?

There is a disturbing pattern developing here.

Are you finding very many of their problems have incorrect solutions? Or is it just that we are only seeing the very few that have issues?

Aside from that, it's a bit troubling that they are having you spend a lot of time analyzing circuits in which the answer is completely dependent on the transistor beta. Now, if they are just introducing the concept of transistors, that is not too unreasonable. But hopefully they have already pointed out that transistor beta is a very unreliable parameter and that if varies all over the place with temperature, current, voltage, from transistor to transistor, and with the phase of the moon. Then, hopefully, they will soon move on to circuit topologies in which that variation only has minimal impact on the circuit's behavior.

7. DYLH Thread Starter New Member

Aug 13, 2013
28
1
Yep, same book. There were perhaps some other problems I got hung up on in the review exercises of earlier chapters, but moved on. Now that I'm getting some confidence that I may have been doing things correctly, I'll go back and double check.

As far as the transistor analysis, these are essentially the very first intro to transistors in the text. Hopefully things turn around with regard to reliablity of the problems/answers.