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    indivisual out different from differential output in fully differential amplifier

    Hello,

    attached is the transient pic of the fully differential amplifier I have designed,

    if you look to the vo+ and vo- you will see the sparks on it, however the differential coltage is clear due to the subtraction,

    my question, should I be concirned about the individual outputs or only have to look to the differential output (Vo_diff)

    thank you

    Click image for larger version. 

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    Re: indivisual out different from differential output in fully differential amplifier

    Is this a simulation or oscilloscope capture?

    if it's the signals from real hardware, as long as the spikes don't exceed any other circuit restrictions it should be ok. (This is kind of the point of differential signals, common mode noise gets rejected).


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    Re: indivisual out different from differential output in fully differential amplifier

    If your circuit following this one looks only at the diff signal and the common-mode spikes cause no harm, then it is ok. However, since this is targeted for a sample and hold, you have to make sure the signal differential and common-mode) has settled well within the targeted accuracy by the time you take a sample.


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    Re: indivisual out different from differential output in fully differential amplifier

    Dear friends,

    these result are from simulation
    and it is targeted for the sample and hold circuit

    if I want to calculate the settling time do i need to calculate it for the single ended of the two outputs or I calculate it for the differential output?



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    Re: indivisual out different from differential output in fully differential amplifier

    It is common that in fully differential circuits you work with half circuite. Then it doesn't really matter if you talk about single ended or differential amplifier.


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    Re: indivisual out different from differential output in fully differential amplifier

    Quote Originally Posted by sutapanaki View Post
    It is common that in fully differential circuits you work with half circuite. Then it doesn't really matter if you talk about single ended or differential amplifier.
    thank you Suta, talking about the fully differential signal I would say I have no problem but looking to each output then it is sparking



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    Re: indivisual out different from differential output in fully differential amplifier

    Voltage excursions are fine as long as you are within reliability limits. I don't know if you are worried about aging or not, but these voltage excursions impacts the performance over time rather than a dielectric breakdown the moment the circuit is turned on.

    If I were you, I would zoom into the edges of the waveform and see if there is something off there. It may or may not be a problem.

    - - - Updated - - -

    Voltage excursions are fine as long as you are within reliability limits. I don't know if you are worried about aging or not, but these voltage excursions impacts the performance over time rather than a dielectric breakdown the moment the circuit is turned on.

    If I were you, I would zoom into the edges of the waveform and see if there is something off there. It may or may not be a problem.



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