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Low noise Preamplifier

sandyyp

Feb 19, 2021
1
Joined
Feb 19, 2021
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Hello all,
I have designed Low noise preamplifier ckt and PCB. I have got my boards and i am testing them but while testing I am getting huge noise waveform at input as well as output. one thing I have observed is when i am only giving pulse signal to board then there is no noisy waveform but when i am giving power along pulse signal then i am getting huge noisy waveform. what can be the possible reasons and how can i tackle them?
PFA copy of my Circuit and PCB.
 

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danadak

Feb 19, 2021
781
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Feb 19, 2021
Messages
781
Some questions / observations :

1) What does noise look like, eg. scope capture ?
2) Have you looked at spectrum of noise for clues ?
3) Your bypassing on OA power pins seems a little unusual, eg. has
the ceramic for HF noise but nothing (tantalum) for LF noise. And what
is purpose of 10 ohms in power leads of OA ?
4) Load Z you are driving ?
5) Source Z when testing ?
6) Possible ground loops when testing with driving source ?
7) What is input sensor ? Part number.....

When you use caps for bypassing not all caps perform equally (ESR)
for the same C value. In particular not all manufactuers for the same tech-
nology get the same results, so prudent to pay attention to datasheet as well.

400px-Polymer-caps-Impedance-ESR-comparization.jpg


Regards, Dana.
 
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