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op-amp doubt

Discussion in 'General Electronics Discussion' started by krishnenduk, Aug 6, 2009.

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  1. krishnenduk

    krishnenduk

    1
    0
    Aug 6, 2009
    can anyone explain me in layman terms how an op-amp follows its input in a voltage follower? My doubt is, as the output is same as the input, in the next cycle both the inputs will be same voltage and as a basic operation voltage at the inverting terminal gets subtracted from non-inverting terminal and as a resull output must be 0.. But we are getting the same output as input.. how??
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    I'm not able to follow your reasoning, but think of it like this:
    The op-amp actually just amplifies the voltage-differential between its inputs by something like 100000 times. So if the +in is 0.1mV higher than the -in then the output will be at +10V, and if the +in is 0.1mV lower than the -in then the output will be at -10V.
    Connecting the output to the -in makes it follow the +in, for all practical purposes that is, you'll only lose 1/10th of a mV in full-swing amplitude.
    This small voltage is usually measurable with a normally sensitive DVM, just take into consideration that there also may be an input-offset-voltage of several mV.
     
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