Common Emmitter Help

Discussion in 'The Projects Forum' started by darylsingh, Jul 10, 2011.

  1. darylsingh

    Thread Starter New Member

    Jul 10, 2011
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    How do I figure out values for R1 and R2 of a Common Emmitter amplifier with a given Icq, VBE, and Beta?
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Hello daryl, welcome to AAC.

    How do I know what R1 and R2 are ?
     
  3. darylsingh

    Thread Starter New Member

    Jul 10, 2011
    15
    0
    The values of R1 and R2 are not given. I have attached the schematic that I have and I need to figure out the values of R1 and R2 with the ICQ=10mA, VBE=0.7V, and Beta = 100. Thanks for the help.
     
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    First calculate the base voltage, roughly IC*RE + VBE, but maybe your examiner expects you to know that IE is a bit bigger than IC? Then find the base current. You know the collector current and the current gain...

    Now work out the potential divider resistors: here there are many possibilities, but one rule of thumb might be to assume that the resistor to VCC passes 10*IB, and the resistor to ground passes 9*IB. Again, your teachers may expect some other rule to be followed.

    The answers may or may not be close to preferred values, and your teacher may or may not expect you to do something about that.
     
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