where V_A is the so-called Early voltage. Analysis based upon a nullor leads to the output resistance of this current sink as R_out = r_O(? + 1) + R_C, where r_O is the small-signal transistor output resistance given by r_O = (V_A + V_CB)/i_out. See current mirror for the analysis.

Use of the nullor idealization allows design of the circuitry around the op-amp. The