Fault detection for linear analog circuits using current injection

A new test technique for linear analog circuits which employs current injection as input test stimulus is described. Our investigations have shown that current transitions resulting from a current injected on internal test points are significantly different for the fault free and faulty circuits. This can be used for fault detection purposes. In fact, the current injection as test input stimulus represents a powerful alternative to the test approaches based on conventional voltage input stimulus. The new approach allows one to improve the testability of various faults, which are difficult to detect or are untestable when using voltage-based test stimulus. In addition the technique has significant advantages for BIST purposes. The technique is illustrated by means of a modern opamp circuit and by considering catastrophic and gate-oxide-short (GOS) faults.