Low power fast settling switched capacitor PTAT current reference circuit for low frequency applications

Abstract

This paper presents a low voltage, low power, fast settling switched capacitor based Proportional to Absolute Temperature (PTAT) current reference circuit. Unlike in a conventional resistor based PTAT current source, the proposed circuit saves a significant amount of silicon area on chip and hence the circuit becomes less susceptible to process variations. It creates a reference current of 1 nA from a 0.5 V power supply at room temperature (27◦C). It has PTAT characteristics in the temperatures from −10◦C to 80◦C. The circuit draws a very low power of 1.5 nW and exhibits a good supply voltage sensitivity of 3.2 %/V. A startup circuit connected to the PTAT source improves the transient response by reducing the settling time. To test the PTAT current reference circuit, a low power log-domain filter which can be used for biomedical applications is realised and biased with the proposed PTAT current source. Results show that the filter cutoff frequency is constant over temperature variations. The CMOS technology used for designing the circuits is UMC 65 nm and tool used for simulations is Cadence Virtuoso. © 2020 ASTES Publishers. All rights reserved.