# Homework Help: Power Spectral Density problem

1. Jun 9, 2007

### FunkyDwarf

1. The problem statement, all variables and given/known data
Calculate the noise equivalent bandwidth of the amplifier.

2. Relevant equations
A(f) = transfer function of the amplifier
B = (1/S(fo) )* Integral over all values of S(f)

3. The attempt at a solution

Ok we're given the integral of |A(f)| but im not sure how to go from that to a power spectral density function, because thats what S(f) is isnt it? Initially i used A(f) as S(f), which im pretty sure is wrong, but it worked in proving the approximation that B = A^2 fc for some charactaristic frequency fc. In this case i simply used S(fo) as A and the intergral as the one given.

I think that assumptions wrong but i don't know how to fix it :(

Thanks
-G

2. Jun 11, 2007

### Staff: Mentor

I don't know if I'll be able to be of much help on this one. The wikipedia.org page looks to be okay on this subject (as long as nobody edits it...)

http://en.wikipedia.org/wiki/Power_spectral_density

That page also has a pointer to a Wolfram page that you can have pretty good confidence in.

BTW, what is the definition of the Noise Equivalent Bandwidth of an amplifier?

This is an interesting paper from TI.... what learning resources do you have for your class?

http://focus.ti.com/lit/an/swra030/swra030.pdf

3. Jun 11, 2007

### FunkyDwarf

Ah hey thanks for replying man, its ok i actually found a past exercise sheet with the same question. Its actually quite hard, i think :(

thanks!
-G