The Ideal Op Amp with Three Pins has the same behavior as the Ideal Op Amp, which has four pins. Only the negative output pin is left out. Both the input voltage and current are fixed to zero (nullator). At the output pin any voltage and any current are possible.

$i_{{\mathrm{in}}_n}\=i_{{\mathrm{in}}_p}\=0$

$v_{{\mathrm{in}}_n}\=v_{{\mathrm{in}}_p}\=0$