Reduction of the temperature dependence of the channel resistance in a MOS transistor

Abstract

A. A, Redkokasha UDC 681.2.087.9:621.395Switching of intermediate-level voltages (5-10 V) into high-resistance loads by means of MOS transistor (MOST) switches presents no difficulties since signal-noise ratio is in this case quite high; however, the switching of low-level voltages or of intermediate-level voltages into low-resistance loads involves considerable errors.The problem is that conventional MOST channel resistance Ro on temperature.The well-known method of stabilizing the temperature dependence of Ro of an open MOST by applying a fixed gate-source voltage corresponding to the point of thermal stability [I, 2] is inapplicable to switches [2] since it increases Ro to several kiloohms.The circuit proposed in [3] avoids these difficulties. The principles of temperature compensation are discussed here using as an example a MOS transistor with an induced p-channel. According to experimental data [i, 2], the function Ro(T) is constant within the temperature range from 5 to 60~ provided the gate-source voltage Ug s = const. If T = const and Ug s is two to four times the threshold voltage Uo, the function Ro(AUgs) , where AUgs is a small deviation from Ugs, is also linear.Note that a temperature change AT = 10~ produces the same change in Ro as AUg s = 0.15 to 1.3 V.