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Low noise Preamplifier

Discussion in 'Sensors and Actuators' started by sandyyp, Feb 19, 2021.

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  1. sandyyp


    Feb 19, 2021
    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.

    Attached Files:

  2. danadak


    Feb 19, 2021
    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.


    Regards, Dana.
    Last edited: Feb 19, 2021
    Martaine2005 likes this.
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