A 0.9-V, 747-nW Capacitively Biased Diode-Based Single BJT Branch Bandgap Circuit

Abstract

In this paper, a bandgap reference (BGR) circuit that combines the capacitively biased diode (CBD) structure and the proportional-to-absolute-temperature (PTAT) voltage-embedded amplifier has been proposed. In order to enhance compatibility with digital domain supply voltage and achieve low power consumption, the supply voltage of the circuit is set at $0.9V$, benefiting from the fact that both the CBD structure and the PTAT-embedded amplifier can operate at sub-1 V supply voltages. The circuit generates a complementary-to-absolute-temperature (CTAT) voltage through the CBD structure. PTAT voltage is achieved by a PTAT-embedded amplifier in a unity-gain feedback configuration. The calibration of temperature coefficient (TC) is realized by applying a time-domain trimming method through an on-chip RC delay circuit. The reference clock frequency is a typical 32-kHz crystal oscillator clock frequency, enabling high versatility of the circuit. Implemented in 0.13- $\mu$m CMOS, measurement results show that the proposed BGR achieves an average temperature coefficient of 28 ppm/°C over −40°C to 125°C, voltage accuracy $(\sigma /\mu )$ of 0.25%, power supply rejection (PSR) of $-50\text{dB}@\text{10 Hz}$, with an active area of $0.03{\text{mm}}^2$, and a power consumption of $747\text{nW}$.