# Op Amp Filters



## chicago (Oct 20, 2007)

I noticed that EERM does not have a few of the more common op-amp circuits referenced in Figure 44.8

In particular, the following:

- high-pass filter

- band-pass filter

- band-reject filter

- differential amplifier

You would think that they would at least include this in the Appendix, but they don't. That's a shame because these filters are the most often used in the real world. I'm not going to spend valuable test time deriving the gains, should they ask a question involving one of them in the morning part.

Can anyone find a site out there which has the gains (Vo/Vin) in terms of R,C? It's astounding, but I have yet to find a website which gives an equation of the gains similar to the way EERM has for the low-pass filter in Figure 44.8(g).


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## jdd18vm (Oct 20, 2007)

chicago said:


> I noticed that EERM does not have a few of the more common op-amp circuits referenced in Figure 44.8
> In particular, the following:
> 
> - high-pass filter
> ...



Chi, take a trip to ncees site, download the FE Reference manual its free and has a lot of the basic info on all the stuff you and I have been asking about. I wont fair as well with the electronics as you but that may do you good. I only printed an bound the electrical related formulas from it. And being out of school 20 plus years some math stuff.

It has all the filter info and formulas (gain not that *I* get it)

GL


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## benbo (Oct 20, 2007)

The problem is that there are literally thousand of different configurations of op amp filters. I had a whole class on it in school (that I promptly forgot).

A quick internet search can find you some useful info -

http://ocw.mit.edu/NR/rdonlyres/38FF6DFD-7...23_op_amps2.pdf

http://ourworld.compuserve.com/homepages/B...owden/opamp.htm

On the other hand, any op amp circuit in the AM is going to be really simple. A quick analysis using the "Golden Rules" for ideal op amps (ie V+ = V-) should not be that hard.

And remmber that op amps can also be used as switches and comparators.


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