Transistor gain problem

  • #1

Homework Statement



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.)


Homework Equations


gain current = output current/imput current


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)
 

Answers and Replies

  • #2
phinds
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Homework Statement



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.)


Homework Equations


gain current = output current/imput current


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)

How many ma are in an amp? How many in .1 amp?
 
  • #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?
 
  • #4
phinds
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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?

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.
 
  • #5
oh! i dont know why it changed to ma the original problem uses mu i still need help with the problem! haha
 
  • #6
CWatters
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but if it is then how is it possible to get to 40,000 by multypling tens

The question says

If a transistor circuit is used to amplify a 2.5 uA signal to at least 0.1 A

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

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