MEASUREMENT OF STANDARD-DEVIATION OF THRESHOLD VOLTAGE BY USING PARALLEL-CONNECTED MOSFETS

A test circuit in which many MOSFETs of identical structure are parall el connected is proposed for measuring the standard deviation of MOSFE T threshold voltage. The threshold voltage, which is extracted from th e drain-current versus gate-voltage (I-DS-V-G) characteristic for this test circuit, differs from the average value of those for the individ ual MOSFETs included in this test circuit by an amount that depends on its standard deviation. Using this fact, the standard deviation of th e threshold voltage can easily be measured. This paper describes the m easurement principle, establishes its verification using I-DS-V-G char acteristics for experimental MOSFETs, and discusses its accuracy. (C) 1997 Scripta Technica, Inc.