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op-amp doubt

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

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  1. krishnenduk


    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


    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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