PIR .5Hz noise seen in 2nd stage output amplifier

[dick_freebird]

One thing to look at is the comparator's (if present) output
loading, whether this and how it's returned are a significant
"knob". A series resistor between its output and load might
soften the "kick" usefully (at the cost of some speed, which
doesn't look to matter here).

 

[rohithkrishnan]

Hi,

Don´t change two or more items the same time.

* Change the first stage and see if the first stage causes the problem
* Change the second stage and see if the second stage causes the problem

Klaus

I've changed these step by step.After confirming that there is no noise after reducing first stage ,then increased the gain of 2nd stage

Rohith