Golden Rules of Op-Amp AnalysisRule 1: VA = VB
The output attempts to do whatever is necessary to make the voltage difference between the inputs zero.
The op-amp “looks” at its input terminals and swings its output terminal around so that the external feedback network brings the input differential to zero.
Rule 2: IA = IB = 0
The inputs draw no current
The inputs are connected to what is essentially an open circuit