Analysis of op-amp circuits to determine the effect of the op-amp VOS on their performance
is straightforward: The input voltage signal source is short-circuited and the op
amp is replaced with the model of Fig. 2.28. (Eliminating the input signal, done to simplify
matters, is based on the principle of superposition.) Following this procedure, we
find that both the inverting and the noninverting amplifier configurations result in the
same circuit, that shown in Fig. 2.29, from which the output dc voltage due to VOS is found
to be