Built-in Current Sensor for Quiescent Current Testing in Analog CMOS Circuits

In this paper we present a new built in current sensor (BICS) for quiescent current testing- I_DDQ. This sensor has been designed using forward bias technique to limit the supply voltage degradation caused by quiescent current passing through the BICS to 2% of the supply voltage. A CMOS operational amplifier designed for operation at plusmn 2.5 V in 0.5 mum n-well CMOS process is used as the circuit under test (CUT). The faults simulating possible short and bridging defects are introduced using the fault injection transistors (FIT). A total of twenty short faults have been introduced into the CUT and nineteen of them been detected giving 95% fault coverage.