Low-Voltage Current and Voltage Reference Design Based on the MOSFET ZTC Effect

Most conventional CMOS technologies possess the so-called zero-temperature coefficient (ZTC) operating point where the transistor's drain current becomes nearly independent of temperature due to the mutual temperature cancellation of threshold voltage and carrier mobility. This paper discusses how this ZTC point can be exploited in the design of current and voltage references with low supply voltages. Besides a theoretical overview regarding the ZTC behavior, a current reference in a standard 0.25-μm CMOS technology operable from 1.3 V is presented. To further explore the possibilities of this approach, a voltage reference with a nominal supply voltage of just 0.5 V is designed and fabricated in a 130-nm technology. Measurement results are given for both circuits.