Temperature dependence of output voltage generated by interaction of threshold voltage and mobility of an NMOS transistor

Mutual compensation of mobility and threshold voltage temperature variation s may result in a zero temperature coefficient (ZTC) bias point of an NMOS transistor. The conditions under which this effect occurs, stability of thi s bias point, and the temperature dependence of the output voltage for a di ode-connected transistor operating in the vicinity of ZTC point are investi gated in this paper. Some possible applications of this effect include temp erature sensors with linear dependence of voltage versus temperature, and v oltage and current reference circuits. The theory is verified experimentall y investigating the temperature behavior of an NMOS transistor realized in 0.35 mum CMOS process. The design and simulation results of simple current and voltage reference circuits for implementation in 0.18 mum CMOS technolo gy are given.