by Jack Goho
Gideon Analytical Laboratories received two semi-operational LM386 operational amplifiers for failure analysis. An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. Op-amps are linear devices that have all the properties required for DC amplification and are used in signal conditioning, filtering, or to perform a variety of mathematical operations. The op-amps received were reported to have quiescent current 2 to 3 times the normal value. The goal was to determine the cause the failure.
Failure analysis ensued. Electrical testing confirmed the op-amps had excessive current and lower capacitance on the voltage output. Both op-amps had electrical stress on the output, which destroyed the diode junction at points on two trace lines within the package. The fail site was a junction separating the Vs rail from the Vout. This occurred because of excessive current beyond the device capability, therefore current was tunneling through the junction which caused a leakage path. Both op-amps had uplifted silicon oxide caused by excessive tunneling through the junction. This caused melting of metal and rendered the junction conductive.
Gideon Analytical Laboratories concluded that excess current was the reason for this failure. To remedy this problem, one could reduce the LM386 Op-amp stress by eliminating DC offset at the input, or by adding a series capacitor at one of the pins. Gideon Analytical Laboratories is the place to which to turn for all your failure analysis needs. With state of the art analytical equipment and over two decades of experience, Gideon Analytical Laboratories will identify exactly why and how parts fail. Information provided by Gideon Analytical Laboratories can help save companies time, money, and valuable resources.