Anyone, feedback circuit

[Anonymous]

Can any one tell me what the purpose of a capacitor across feedback circuit.
I am working on a PI,at one time had a bad pulseing problem and no threshold tone.(sound)I stoped pulseing by replaceing some parts with new ones.Pulseing is slowly comeing back,can stop it with new parts.thats a waist of time and money.
I am trying to learn what each circuit does in PI.
I have been all through this PI teaching my self PI electronics.Right now I am at DC gain stage and threshold gain.
They both have a cap across feedback. Thanks
Frank.

 

[Anonymous]

Hi Frank,
The capacitor across the feedback resistor is there to limit the frequency response of the amplifier. From the integrator on, you are only dealing with low frequency signals and limiting the bandwidth cuts down on noise that may otherwise get through.
Eric.

 

[Anonymous]

Eric,
Thanks,Ill move on to a different circuit.So far I have replaced all resistors, ICs, caps,fets,1 transister.with primes(with-out a scope)if I replace all parts with new ones, same value.I might repair it.In doing so,I am learning about PI circuits.
Eric, in all my problems with this PI, IT still a good one.Its light and well balanced.when I first got it New,dept was 8" US nickel.had it past 13" at one time.
If you take it over and build it your self, I think that you should put it back on the market.
Frank