A Novel High-Resolution Interface Circuit for Resistance Measurement

Resistive sensors have been widely used due to their advantages in high linearity and stable performance. Measurement of their resistance is a key issue in the sensor readout circuit design. In this paper, a novel resistance measurement interface circuit is proposed and fabricated in standard 180nm CMOS technology. The presented circuit consists of a bandgap reference, an auto-zero offset-stabilized amplifier, a damped-switch capacitor (SC) based self-adapted variable gain amplifier (VGA) and a 12-bit successive approximation register (SAR) analog-to-digital converter (ADC). The reference adopts a novel 2<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup>-order base-current compensation circuit to generate stable supply for the circuit. Auto-zero offset-stabilized amplifier reduces the effect of the input offset voltage and the self-adapted VGA increases the dynamic input range of resistance the circuit as well as reduces the offset of 2-stage amplifier. The experiment results indicate that the circuit has an input range of 50Ω~1.8KΩ. The maximum of relative error in the test is 1.82% @ about 100Ω and 0.64% @ about 1000Ω. The power consumption of the circuit is 221μW and the area of the core of the whole chip is 0.5192 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>.