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.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    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
     
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