Measurement of Standard Deviation for Threshold Voltage using Parallel-Connected MOSFETs

The test circuit, in which many same-structure MOSFETs are parallel-connected, is proposed for measuring the standard deviation for MOSFET threshold voltage. The threshold voltage, which is extracted from the drain-current vs. gate-voltage relation for this test circuit is different from the average value of those for the each individual MOSFETs included in this test circuit by the value depending on its standard deviation. By using this fact, the standard deviation for threshold voltage can easily be measured. This paper describes the measurement principle and confirms it, using IDS-VG relations for experimental MOSFETs.