# Transistor gain problem

1. Jul 20, 2012

### felipenavarro

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. Jul 20, 2012

### phinds

How many ma are in an amp? How many in .1 amp?

3. Jul 21, 2012

### felipenavarro

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. Jul 21, 2012

### phinds

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. Aug 13, 2012

### felipenavarro

oh! i dont know why it changed to ma the original problem uses mu i still need help with the problem! haha

6. Aug 13, 2012

### CWatters

The question says

So a gain of 100,000 would also be acceptable.

7. Aug 13, 2012

### felipenavarro

ah! got to read with more attention! thanks !