# Op-amp Function generator HELP PLEASE

Discussion in 'General Electronics Chat' started by Hurdy, Feb 28, 2006.

1. ### Hurdy Thread Starter Senior Member

Feb 27, 2006
137
0
I have this function generator circuit that I really don't understand.
I think my biggest problem is that I can't get my head around how an op-amp works. I've tried reading them up on the net but I just can't get it.

Thank you for you time with me, it's very very much appreciated.

Rob

2. ### aac Active Member

Jun 13, 2005
35
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OK, here goes. Amp B is set up as an integrator. At some point the output of amp D will be close to 9V. In this condition the output will be ramping down because B is integrating the current through R4, R5. By changing R4 you can change the rate the output of the integrator ramps. At some point, the voltage at the plus of D crosses the threshold because of this ramp. Amp D is set up as a compare and will switch it's output to something close to ground when this happens. This causes B to ramp the other way forming the triangle. Amp A is just a buffer for the triangle. A crumy sine wave is created by clipping the triangle with the diodes.

In the third sentence the correct amplifier label is D not A as pointed out by Ron H, sorry about that.

3. ### Papabravo Expert

Feb 24, 2006
10,137
1,786
Sorry for the delay. AAC gave a good outline of the workings of your function generator. I had contemplated a longer and more thorough answer since it appears that you are unfamiliar with standard opamp configurations like "folower", "inverter", and "integrator".

Meaning no disrespect, but does the phrase "integrator" convey any meaning to you at all? If you have never taken calculus, there is no reason on Earth why it should mean anything to you. If you have taken calculus and know what an "integrator" is supposed to do my next question is about ordinary differential equations. Do you know what they are and how they are connected to simple circuits like the function generator?

I can adjust my response if I know your level of experience and knowledge.