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Transistor gain problem

  1. Jul 20, 2012 #1
    1. The problem statement, all variables and given/known data

    If a transistor circuit is used to amplify a 2.5 mA signal to at least
    0.1 A, what must be the minimum gain of the transistor circuit?

    b. Assume the amplifier consists of a number of transistors in series,
    each with a gain of 10. How many transistors are needed in this circuit? (Hint: Two such transistors in series would provide a total gain
    of 10 × 10 = 100.)


    2. Relevant equations
    gain current = output current/imput current


    3. The attempt at a solution
    for the first question i got that the current gain should be 40,000 by dividing .1 by 2.5*10^-6. i am not sure if this is correct, but if it is then how is it possible to get to 40,000 by multypling tens?(for question b)
     
  2. jcsd
  3. Jul 20, 2012 #2

    phinds

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    How many ma are in an amp? How many in .1 amp?
     
  4. Jul 21, 2012 #3
    well 1 million in an amp and 100,000 in .1 amps, so is this the answer for question b? that would be 5 transistors of ten in a row.
    but dont i have to get the same answer (as a total amplification) as in question a?
     
  5. Jul 21, 2012 #4

    phinds

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    Ah, well now see ... THAT'S where your problem is the Greek letter mu is the symbol for micro. The "ma" means MILLIamp, not microamp.
     
  6. Aug 13, 2012 #5
    oh! i dont know why it changed to ma the original problem uses mu i still need help with the problem! haha
     
  7. Aug 13, 2012 #6

    CWatters

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    The question says

    So a gain of 100,000 would also be acceptable.
     
  8. Aug 13, 2012 #7
    ah! got to read with more attention! thanks !
     
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