A Low-Power, Low-Noise, Resistive-Bridge Microsensor Readout Circuit with Chopper-Stabilized Recycling Folded Cascode Instrumentation Amplifier

Abstract

In this paper, a low-power and low-noise readout circuit for resistive-bridge microsensors is presented. The chopper-stabilized, recycling folded cascode current-feedback instrumentation amplifier (IA) is proposed to achieve the low-power, low-noise, and high-input impedance. The chopper-stabilized, recycling folded cascode topology (with a Monticelli-style, class-AB output stage) can enhance the overall noise characteristic, gain, and slew rate. The readout circuit consists of a chopper-stabilized, recycling folded cascode IA, low-pass filter (LPF), ADC driving buffer, and 12-bit successive-approximation-register (SAR) analog-to-digital converter (ADC). The prototype readout circuit is implemented in a standard 0.18 µm CMOS process, with an active area of 12.5 mm2. The measured input-referred noise at 1 Hz is 86.6 nV/√Hz and the noise efficiency factor (NEF) is 4.94, respectively. The total current consumption is 2.23 μA, with a 1.8 V power supply.

Keywords

• low-noise
• resistive microsensor
• sensor readout circuit
• chopper stabilization
• recycling folded cascode instrumentation amplifier