Harmonic nonlinearity in diff opmap

[manissri]

hi all
as the book tell that the fully differential(output is fully differential) has no even order nonlinearity due to differential output.
my question is how this even r odd hormonics affect the performance of opamp.
and if there is no even hormonics nonlinearity present in it then how the performance will improved.
plz give ur comments.
regards
manissri

 

[Rainbow00]

usually we use op amp to amplify signals. if we gives a perfect 2khz sine wave input we are expecting a a perfect 2khz sine wave output with maybe larger amplitude. with harmonics what you're going to get at output is not sine wave any more. it you see it in frequency domain it has all the spikes at the harmonic frequency due to nonlinearity of op amp.

if we can have perfect op amp i guess there is no use for small signal model. for bjt its exponential relationship and for mos its square relationship. mos are more linear than bjt since it only has 2nd order.

simple example, you design a unity gain buffer, do you want the signal distorted after passing through the buffer?


regards
gd