Coupling capacitors

What is the function of coupling capacitors in multi stage amplifiers?

 

To pass the signal to the next stage without allowing the DC part to get through.

 

For blocking DC.
Usually amplifier will have a high gain. If you do not block the DC in each stage, the DC component will be very high and satuate each stage of the amplifier.

 

They also serve the function of screwing up the frequency response thus creating work for the big boys.

 

The presence of coupling capacitors usually means the amplifier design employing them has zero DC gain.

Very high gain amplifiers don't of necessity require coupling capacitors.

Consider for instance the operational amplifier which may have compensating capacitors included for particular reasons but not have coupling capacitors for DC isolation of stages.

DC coupled amplifiers are more difficult to design and control but not impossibly so.

 

I want to know about coupling capacitors. Is it used to block DC (one of elememts of input signal) go into DC stage or to block DC from DC stage go into previous amprifier(or something else)?

 

Where used, the capacitor isolates DC signal components between amplifier stages, including the amplifier's input and output terminals. DC isolation at a circuit node in the amplification chain applies only where a capacitor is correctly inserted in series with the signal path at the circuit "node" under consideration. Hence the isolation capacitor "performs" each of those functions you mention.

In the case of [negative] feedback applied within an amplifier, one may also insert a capacitor in the feedback path to prevent undesirable DC coupling between circuit nodes in the feedback path.

 

#12 had the best answer; to pass the ac part of the signal without alowing the dc part to get through

 

t n k has a problem answer.

1. Coupling capacitors are used to block dc regardless of the amplifier stage gain. If you have a stage gain of 3 and the input signal is 3mV riding on 30Vdc the amplifier saturates unless a coupling capacitor strips off the DC

2. High gain amplifiers need coupling capacitors more than low gain amplifiers.

3. Op amp circuits often use coupling capacitors to block dc.

You are correct about dc coupled amplifiers.