A sub-1V picowatt voltage reference with improved PSRR and line sensitivity for wearable biomedical applications

This paper presents a picowatt voltage reference circuit using a voltage regulation scheme consisting of a self-regulation native N-type transistor, a double regulation topology formed by a stacked structure of two native N-type transistors, and a P-type transistor-based self-biased current source, to feed a diode-connected P-type load and a PNP transistor load. This improves the line sensitivity and the power supply rejection ratio (PSRR) without the use of an on-chip capacitor. The circuit is designed in a 180 nm CMOS process with an area of 13,700 μm² and operates with a minimum supply voltage of 0.8 V. Post layout simulation results show that the circuit provides a constant output voltage of 160.2 mV with a temperature coefficient (TC) of 151.6 ppm/\(^{\circ }\)C from 0 to 100 \(^{\circ }\)C, a line sensitivity of 0.00114%/V, a PSRR of \(-\)72.6 dB at 100 Hz, and an untrimmed voltage accuracy (\(\upsigma /\upmu\)) of 0.99%.