A 5-V 290- $\mu\hbox{W}$ Low-Noise Chopper-Stabilized Capacitive-Sensor Readout Circuit in 0.8- $\mu\hbox{m}$ CMOS Using a Correlated-Level-Shifting Technique

Abstract

In this brief, a low-power high-resolution readout front end intended for capacitive sensors is presented, in which the circuit uses correlated-level-shifting (CLS) and chopperstabilization (CS) techniques. CLS is a relatively new switchedcapacitor (SC) technique that is used to reduce errors from finite operational amplifier (op-amp) gain, whereas CS is a classic technique that is used to reduce the adverse effects of dc offset and low-frequency noise associated with the op-amp. In this brief, the capacitive sensor is physically emulated by a pair of on-chip differential variable capacitors that are in the femtofarad range. The proposed front end is designed in a 0.8-μm CMOS technology and consumes 290 μW from a single 5-V supply. The readout circuit achieves a capacitance noise floor of 0.018 aF/√Hz at 400 Hz with a sensitivity of 50 mV/fF.