Another Basic Op-Amp Question

[bittware]

Hello experts,
In an odinary amplifying circuit, if the output occurs oscillation, what might be the root cause?

 

[ahmad_abdulghany]

it is may be due to fluctwations in input signal .. or phase shift by 180 degree in the feed back cicuit that makes it as if it was +ve feed back that make you lose control..

 

[electronics_kumar]

IN OPAMP SYSTEM

in control system perspective, its pole are lying in the right half of s-plane

OR

also in Z TRANSFORM poles are lying outsude of the unit circle.

OR

in analog electronics , it is having postive feedback also phasse shift is 0 or 360 aswell as product of gain for forward netwok and that feedback network is one.

OR

systems output for the given input is keeping on increasing
or
STILL MORE TO FIND

 

[Kral]

Let Rf = the feedback resistor value
Ri = the input resistor value
There are several things that you can check:
.
Is the Op Amp internally compensated for unity gain? If not, check that the external compensation (if there are provisions for this) is adequate for the closed loop gain (Rf/Ri) that you are providing.
.
Check that the connections to the OP Amp inputs are short.
.
Check that you have adequate power supply bypassing capacitors, with short connections, at the Op Amp power terminals. The capacitors must have low ESR (equivalent series resistance) at the frequency of interest. Usually ceramic types work well.
.
Regards,
Kral