# Designing DC Bias Circuit

Discussion in 'Homework Help' started by sparkey2000, Aug 12, 2008.

1. ### sparkey2000 Thread Starter New Member

Mar 9, 2008
8
0
Please can someone help me answer the attached question; I can work through examples and calculate IC, IE, VCE, IB and VBE etc.

However I'm stuck with the following question and I will need to do this for an exam this week; and help will be much appreciated.

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2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
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What results have you got for the problem?

3. ### yubyub Member

Aug 13, 2008
19
6
Rc + Re ~= 16k, since Vcq = Vcc/2, Rc ~= Re = 8k

Ib ~= 6.67µA R1 ~= 2.4M (i think?) R2 = R1?

Those are approximations, and i'm not sure about R1, R2. The lack of working would cause you to get no marks though.

Assuming you have a textbook with BJT's, you should have no problem doing the working out properly.

4. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Vcq equals 8 volts because it is half the Vcc, thus Rc=(Vcc-Vcq)/Ic

Rc=8V/1mA=8K

then we assume that Ie equals Ic and that Ve equals Vcc/10

thus Re=Ve/Ie=1.6V/1mA=1.6K

then we assume that R2 equals 0.1*150*Re

thus R2=24K

then Vb equals Ve+0.7=2.1V

then make the voltage divider equation to find R1