A Measuring Method for MOST Transconductance and Its Variation

A precise method is given for measuring the transconductance of an MOS transistor (MOST) and also its value and rate of variation. The measuring setup uses a differential amplifier, in which the output voltage of a sample MOST operated as a common-source amplifier is compared with the reference voltage derived from the attenuators used as a standard, and also a synchronous demodulator, with which the difference signal obtained from the differential amplifier is converted into corresponding dc voltage used in determining the null point. The transconductance from the 0.1 to 100-m℧ range is measured with an accuracy of less than two percent, over the frequency range of 0.1-10 kHz. The transconductance variation in excess of 1 μ℧ and also the percentage variation of transconductance in excess of 0.2 percent for an MOST with a transconductance of 1 m℧ is measured. Measured examples are also given.