A 1.2-V 4.2-ppm/°C High-Order Curvature-Compensated CMOS Bandgap Reference

This study presents a high-precision CMOS bandgap reference (BGR) circuit with low supply voltage. The proposed BGR circuit consists of two BGR cores and a curvature correction circuit, which includes a current mirror and a summing circuit. Two BGR cores adopt conventional structures with the curvature-down characteristics. A current-mirror circuit is proposed to implement one of the BGR cores to have the curvature-up characteristic. Selection of the appropriate resistances in the BGR cores results in one reference voltage with a well balanced curvature-down characteristic and another reference voltage with an evenly balanced curvature-up characteristic. The summation of these reference voltages is proposed to achieve a high-order curvature compensation. This curvature correction circuit causes the proposed BGR circuit without any trimming to show a measured temperature coefficient (TC) as low as 4.2 ppm/degrees C over a wide temperature range of 160 degrees C (-40 similar to 120 degrees C) at a power supply voltage of 1.2 V. The average TC for 8 random samples is approximately 9.3 ppm/degrees C. The measured power-supply rejection ratio (PSRR) of -30 dB is achieved at the frequency of 100 kHz. The total chip size is 0.063mm(2) with a standard 0.13-mu m CMOS process.