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Go=K/(s*tau+1) is the formula for a first order lowpass with gain K.
This expression is used here to approximate the frequency-dependent opamp gain Go(s) by a first order function.
Thus: Vout=Go*Vdiff with Vdiff=Vp - Vn (differential input).
The bandwidth of the opamp with 100% feedback (unity follower) can be determined using the classical feedback formula
The feedback factor Fr in this case is "1".
i understand the question now but i have a new question.we have k and tau values but if i want to get Go value, ı should use s in formula.What value does s take.i know it is a domain not a value and should i transform it aything else?What is the purpose
here, the symbol s is nothing else than an abbreviation for jw. Thus s=jw=2*Pi*f.
Introduce Go into the expression for G and rearrange so that you get the same form as in the formula for G (that means: the constant in the denumerator is "1").
Then you can determine the new tau-value which is identical to 1/w.