Confused about operational amplifier configuration..

[DaveHardy]

I've got a few books about operational amplifiers that don't explain why I keep seeing this circuit below with a big electrolytic shunted between R37 and ground.  I simply can't figure out the point of putting a capacitor there.  Does anybody know why it is there or what it is called so that I can goole it? 

This circuit is for audio purposes.

[KJDS]

RIAA equalization is the most likely

[planet12]

"Shunted" makes it sound like you mean "in parallel with" R37.

If you're meaning a largish cap in series with R37, what this does is make the opamp work as a unity-gain voltage follower at DC, but with the programmed gain once the frequency is high enough to make the capacitors reactance small enough to no longer effect the gain; this is often used so DC offsets within the system do not accumulate and amplify (if they're not wanted - hence you'll frequently find this in audio systems).

[DaveHardy]

"Shunted" makes it sound like you mean "in parallel with" R37.

If you're meaning a largish cap in series with R37, what this does is make the opamp work as a unity-gain voltage follower at DC, but with the programmed gain once the frequency is high enough to make the capacitors reactance small enough to no longer effect the gain; this is often used so DC offsets within the system do not accumulate and amplify (if they're not wanted - hence you'll frequently find this in audio systems).

Yes, I meant in series. 

Thanks, this is the answer that I was looking for.  How can I Google this circuit to learn how to compute values, learn about the pros and cons, etc?  Is there any info on the web or in books that you could point me to that explains this circuit in detail?

Thanks for the help everyone.

[c4757p]

Just thoroughly read this article on impedance, and understand that a voltage divider works with complex impedances as well as pure resistances. Then once you understand the basic function of an op amp*, you can figure all these out with just a bit of algebra.

*The most basic, useful explanation of an 'ideal' op amp that I can think of (one of them, at least) is that the inputs take no current, and it moves its output towards the sign of whichever input is higher, in an attempt to make both inputs equal. If it cannot make them equal, it's said to be saturated. Once you've ascertained that it is able to make them equal and has not saturated, just calculate the output based on the assumption that both inputs are equal.

[c4757p]

Alternately, to simplify if you don't care about things like phase (basic filters, etc):

C = capacitance
L = inductance
f = frequency
X = reactance (the complex/AC part of the impedance)