A ZTC-based 0.5V CMOS Voltage Reference

This paper presents a voltage reference circuit operational from a 0.5 V supply which is based on the zero-temperature coefficient (ZTC) operating point of a MOS transistor. The ZTC condition is reviewed and it is found that a MOSFET biased below its ZTC point with a PTAT current source can yield a temperature stable output at this low supply voltage. With this idea in mind, a circuit which does not rely on the availability of special devices like Shottky diodes is designed in 130 nm CMOS. Simulations show that this circuit generates an average reference voltage of 318 mV from a 0.5 V supply. The temperature coefficient is 154 ppm/K and the voltage reference has a power supply rejection ratio (PSRR) of 41 dB at DC.