Chopper-Stabilized Instrumentation Amplifier with Automatic Frequency Tuning Loop

Abstract

A variable-gain chopper-stabilized instrumentation amplifier (chopper IA), which employs a low pass filter (LPF) to attenuate the up-converted noise at the chopping frequency, is presented. The circuit is designed and fabricated with Taiwan Semiconductor Manufacturing Company (TSMC) (Hsinchu, Taiwan) 0.18 μm complementary metal-oxide-semiconductor (CMOS) technology. Consuming 1.1 mW from a 1.2 V supply voltage, the chopper IA achieves a variable gain of 20.7–48.5 dB, with a minimum bandwidth of 6.7 kHz and a common-mode rejection ratio (CMRR) of 95 dB below 10 kHz. By using the chopper technique, the input-referred noise of the chopper IA can be reduced to 0.28 μVrms (0~96 kHz), with a chopping frequency of 83.3 kHz. An automatic frequency tuning loop (ATL) is employed to adjust the corner frequency of the LPF dynamically so that the frequency ratio between the chopping frequency and the LPF corner frequency is 8.3, ensuring a noise reduction of 36.7 dB.

Low Noise, High Input Impedance Digital-Analog Hybrid Offset Suppression Amplifier for Wearable Dry Electrode ECG Monitoring

“…Electronics 2019,x, x FOR PEER REVIEW 2 of 13 low-frequency flicker noise of the amplifier [11]. However, chopping reduces the DC input impedance of the amplifier because the passive mixer at the input together with the input capacitor forms a switched-capacitor resistance.…”

“…First of all, it must be able to cope with the effects of large skin-electrode impedance changes on the signal, usually by a pre-amplifier with very high input-impedance to minimize signal attenuation and degeneration [5]. Chopper-stabilized amplifier is a popular front-end topology for ECG monitoring and neural recording [6][7][8][9][10], as the chopper technique is an effective way to suppress low-frequency flicker noise of the amplifier [11]. However, chopping reduces the DC input impedance of the amplifier because the passive mixer at the input together with the input capacitor forms a switched-capacitor resistance.…”

Editorial for the Special Issue on Interface Circuits for Microsensor Integrated Systems

“…There are 10 papers published in this Special Issue, covering micromachined sensors interfacing circuits [ 1 , 2 , 3 , 4 ], techniques for sensor interrogation and conditioning circuits [ 5 , 6 , 7 ], and sensors and systems design [ 8 , 9 , 10 ].…”

“…On the sensors and systems design, Wei and Bao presented a low power, energy-efficient precision CMOS temperature sensor based on bipolar junction transistors and a pre-bias circuit and bipolar core [ 8 ]. Wu et al presented an A variable-gain chopper-stabilized instrumentation amplifier (chopper IA), which employs a low pass filter (LPF) to attenuate the up-converted noise at the chopping frequency for micromachined sensors applications [ 9 ]. Liu et al presented a review of recent progress in the rapid sintering of nanosilver pastes: preparation of nanosilver particles and pastes, mechanisms of nanopastes sintering, and different rapid sintering processes were discussed [ 10 ].…”