Another, basic, bypass capacitor question

[Bob Engelhardt]

I made a circuit with 5 op amps, to do a little calculation, with input
from switches and pots. I.e., dc. I didn't use bypass caps, but I'm
wondering whether I should have. I'm thinking that even though it is
dealing with dc signals, the op amps might be sensitive to ps noise.
And there have been a couple of instances of unexpected & unexplainable
behavior.

Is it worth the trouble to add them now?

Thanks,
Bob

 

[Sjouke Burry]

Bob Engelhardt wrote:

I made a circuit with 5 op amps, to do a little calculation, with input
from switches and pots. I.e., dc. I didn't use bypass caps, but I'm
wondering whether I should have. I'm thinking that even though it is
dealing with dc signals, the op amps might be sensitive to ps noise.
And there have been a couple of instances of unexpected & unexplainable
behavior.

Is it worth the trouble to add them now?

Thanks,
Bob
Any time you intend to design an amplifier, you

run a high risk of designing an oscillator instead.

So yes, you have to add de-coupling caps(~ .1 uf)
at the positive and negative supply pin to ground, or
with a singlesided supply, between plus and ground.
and keep the tracks to the connection points short
and straight.

If you suspect oscillation, measure some output,
and (nearly)touch parts of the print, oscillation is
very sensitive to stray capacitance.

 

[Bob Engelhardt]

Sjouke Burry wrote:

...
So yes, you have to add de-coupling caps ...

Thanks, I appreciate the help. Bob