[Circuit Analysis] Hard Time to Decide...

dijkarte

Very interesting fact. Does this apply to amp's when connected to capacitors or inductors? AC too?

psparky

According to Kirchoff, current in equals current out....so yes, applies for caps, inductors and AC.

However, you will likely approach these problems differently as you will likely be looking for frequency response. Op amps can be filters. That being said, nodal analysis will still work, the math will just be much tougher because of the JWL and 1/JWC. YOu will also use bode plots to plot the frequency response.

If you take a op amp that does have caps and inductors or whatever, and a DC signal is used....the caps will open and the inductors will short as you know.

When dealing with frequency response, the op amps in school will typically take the -RF/RA approach...or the (1+RF/RA) approach. But you can always fall back on node analysis......what you are ussually looking for in these ideal op amps is the transfer function....or gain. Gain =Vout/Vin.

Btw....if you take a simple op amp that uses the above formula....simply do a nodal analysis on one of these simple ones and you will derive the two formulas above. Do it, it is worth the exercise.

jasonRF

I am vaguely familiar with the book (was an optional book for a class I took many years ago - I bought it but sold it back). Yes, it is rigorous, but you should probably already know basic circuits before you attempt it. Plus, $100+ for an out of print used book on circuits seems steep for most people. If I recall correctly it skips a lot of elementary stuff, but includes discussions of phase plane analysis of nonlinear circuits and all sorts of stuff I have never learned (I am not a circuits person ...).

An even older (not newer) book that might fit the bill a little better is "Basic Circuit Theory" by Desoer and Kuh. Used copies at amazon go for something like $15-$20. I think it is quite good, is more rigorous than the standard intro book, but starts a little more at the beginning of the subject. My copy is at work, but if I recall correctly it was written for Junior level classes at Berkeley, so would probably be good to at least have a good elementary level book to look at first.

good luck,

jason