In this paper we evaluate the effectiveness of current monitoring techniques in detecting Bridge and open defects in CMOS operational amplifiers. We evaluate the detection capabilities by using two current testing techniques. The first technique consists in the oversight of the transient supply current (IDDT) and the second technique consists in the monitoring of quiescent supply current (IDDQ). The most likely resistive and open defects are injected using fault injection additional transistors. Performances of the CMOS operational amplifier are also evaluated after each fault injection. Spice simulations were realized to compare the proposed test techniques and evaluate the best performing one.