Why does op amp go into oscillations when I increase the bias voltage?

[Su Ram]

Can anyone tell me why does my op amp goes into oscillations when I increae the bias volyage..I have decoupled the supply with 3 sets of capacitances on each side..still it just puffs up...

 

[hung_wai_ming@hotmail.com]

Op amp oscillations

Do u mean increase the bias current?
Or, u increase the bias voltage from your nmos based current mirror?

 

[A.Anand Srinivasan]

Re: Op amp oscillations

by increasing the bias current i think you are lowering the output resistance seen by the output capacitor and hence the phase shift is increasing due to the RC value....

 

[surianova]

Re: Op amp oscillations

by increasing the bias current i think you are lowering the output resistance seen by the output capacitor and hence the phase shift is increasing due to the RC value....

if the output resistance is lower, the phase shift shd be less right?

 

[Su Ram]

Re: Op amp oscillations

I gave an external power supply to the op amp (..with constant current) what dont understand is if the oscillations are due to any ground effects at the input or due to decoupling faults..