Low-Noise Resistive Bridge Sensor Analog Front-End Using Chopper-Stabilized Multipath Current Feedback Instrumentation Amplifier and Automatic Offset Cancellation Loop

Abstract

Resistive bridge sensors are used in many application areas to measure changes in physical parameters. To amplify the resistive changes from sensing elements with high precision, various offset contributors in the resistive bridge and amplifiers should be minimized. This study proposes a low-noise resistive bridge sensor analog front-end (AFE) using a chopper-stabilized multipath current feedback instrumentation amplifier (CFIA) and an automatic offset cancellation loop. The proposed circuit exploits a multipath chopper-stabilized architecture for obtaining low noise performance and wide bandwidth characteristics. This circuit can minimize the offsets in the bridge and the high frequency and low frequency amplifiers, while achieving high precision resistive signal acquisition. The high frequency path of the multipath amplifier uses the CFIA topology with class-AB output stage. The offset in the high frequency path is stabilized by the low frequency path amplifier with a high gain and low noise chopper amplifier. The up-modulated offset in the low frequency chopper amplifier path is reduced by the AC-coupled ripple reduction loop (RRL). An automatic offset calibration loop (AOCL) circuit was designed to calibrate the offset due to the bridge mismatch. The AOCL reduces the bridge offset using a successive approximation register (SAR)-based binary-search algorithm. The gain of the proposed circuit is adjustable from 15.56 dB to 44.14 dB. The AFE is implemented in a 0.18 μm CMOS process and draws 123 μA current from a 3.3 V supply. The input referred noise and noise efficiency factor (NEF) are 14.6 nV/√Hz and 6.1, respectively.INDEX Resistive analog front-end, current feedback instrumentation amplifier (CFIA), multipath amplifier, automatic offset calibration loop (AOCL)

A Modulation Method for Tunnel Magnetoresistance Current Sensors Noise Suppression

“…high-frequency ripple suppression loops as alternative solutions [11]. Regarding modulation-demodulation, the ΔΣ modulator structure is extensively utilized in digital chips and integrated into TMR magnetic sensor interface circuits [12,13].…”

“…Current feedback structures can fundamentally address this issue, with recent research focusing on chopping amplifiers based on these structures [ 7 , 8 , 9 , 10 ]. Within chopping technology, designing low-frequency low-pass filters presents increased complexity in CMOS circuits, leading to the rising trend of employing high-frequency ripple suppression loops as alternative solutions [ 11 ]. Regarding modulation-demodulation, the ΔΣ modulator structure is extensively utilized in digital chips and integrated into TMR magnetic sensor interface circuits [ 12 , 13 ].…”

Design and Analysis of a High-Gain, Low-Noise, and Low-Power Analog Front End for Electrocardiogram Acquisition in 45 nm Technology Using gm/ID Method

“…Although digital circuits have already been working on technology nodes (interchangeable with channel length) lower than 5 nm [1,2], their analog circuit counterparts have not advance at the same pace. For the past two decades, most analog circuits have been developed using a 180 nm node or above [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] due to some benefits enjoyed by the larger technology nodes, for example, ease of design, larger amplification, low noise, etc. However, in mixed-signal circuits, analog circuits need to be fabricated with the digital circuits on the same chip to meet various purposes [18].…”

Low-Noise Chopper-Stabilized Zero-Drift Amplifier With SAR-Assisted Automatic Offset Calibration Loop

“…The RRL can reduce the ripples and acts as the notch filter at the chopper frequency. The notch in the transfer function caused by the RRL operation can be compensated for using a multipath amplifier structure by adding a high frequency path (HFP) in parallel with a low frequency path (LFP) [20]- [21]. Designing the LFP of the multipath amplifier structure is important to suppress the low-frequency flicker noise components and to achieve the thermal-noise-limited uniform noise spectral density.…”

“…However, the utilization of large resistors and capacitors in building both the LPF and the HPF can result in substantial area consumption. In [21], an AC-coupled RRL approach was employed to achieve lownoise characteristics in the LFP. This approach can potentially induce secondary offsets in the amplification stage of the RRL itself.…”