This paper presents a low-power CMOS analog front-end (AFE) IC designed with a selectable on-chip dual AC/DC- coupled paths for bio-sensor applications. The DC-coupled path can be selected to sense a biosignal with us...This paper presents a low-power CMOS analog front-end (AFE) IC designed with a selectable on-chip dual AC/DC- coupled paths for bio-sensor applications. The DC-coupled path can be selected to sense a biosignal with useful DC information, and the AC-coupled path can be selected for sensing the AC content of the biosignal by attenuating the unwanted DC component. The AFE IC includes a DC-coupled instrumentation amplifier (INA), two variable-gain 1st-order low pass filters (LPF) with tunable cut-off frequencies, a fixed gain 2nd-order Sallen-Key high-pass filter (HPF) with tunable cut-off frequencies, a buffer and an 8-bit differential successive approximation register (SAR) ADC. The entire AFE channel is designed and fabricated in a proprietary 0.35-μm CMOS technology. Excluding an external buffer needed to properly drive the ADC, the measured AFE IC consumes only 2.37 μA/channel with an input referred noise of ~40 μVrms in [1 Hz, 1 kHz], and successfully displays proper ECG (electrocardiogram) and electrogram (EGM) waveforms for QRS peaks detection. We expect that the low-power dual-path design of this AFE IC can enable it to periodically record both the AC and the DC signals for proper sensing and calibration for various bio-sensing applications.展开更多
The analog frontend(AFE)coupling circuit is a crucial processing element for data acquisition systems based on analog-to-digital converters(ADCs).Currently,high-speed and high-resolution ADCs are predominantly designe...The analog frontend(AFE)coupling circuit is a crucial processing element for data acquisition systems based on analog-to-digital converters(ADCs).Currently,high-speed and high-resolution ADCs are predominantly designed with differential input stages.Conventional highspeed ADC drivers are mainly AC-coupled by employing transformers(Baluns)or fully differential amplifiers(FDAs)with blocking capacitors.However,the results of this study indicate that a certain degree of DC offset error exists and manifests itself as the baseline error in the presence of power dividers connecting several DC-coupled channels that implement high-dynamic-range(HDR)signal conditioning.The study involves a theoretical analysis and explanation of the baseline offset error.The offset error can potentially lead to unexpected out-of-range issues for sampling devices,including high-speed ADCs and switched capacitor array ASICs.High-performance FDAs are adopted,and an offset-free DC-coupled AFE circuit is proposed to address the aforementioned issue using twostage amplification and a resistive attenuator.The proposed methodology is verified via circuit simulations and hardware design.Thus,the baseline offset problem can be accurately solved using the proposed circuit by minimizing the neglectable error.The proposed circuit facilitates improvements in the high-precision measurement of HDR signals in many nuclear physics experiments and some applications in the DC-coupling scheme with FDAs involving resistive power dividers.展开更多
文摘This paper presents a low-power CMOS analog front-end (AFE) IC designed with a selectable on-chip dual AC/DC- coupled paths for bio-sensor applications. The DC-coupled path can be selected to sense a biosignal with useful DC information, and the AC-coupled path can be selected for sensing the AC content of the biosignal by attenuating the unwanted DC component. The AFE IC includes a DC-coupled instrumentation amplifier (INA), two variable-gain 1st-order low pass filters (LPF) with tunable cut-off frequencies, a fixed gain 2nd-order Sallen-Key high-pass filter (HPF) with tunable cut-off frequencies, a buffer and an 8-bit differential successive approximation register (SAR) ADC. The entire AFE channel is designed and fabricated in a proprietary 0.35-μm CMOS technology. Excluding an external buffer needed to properly drive the ADC, the measured AFE IC consumes only 2.37 μA/channel with an input referred noise of ~40 μVrms in [1 Hz, 1 kHz], and successfully displays proper ECG (electrocardiogram) and electrogram (EGM) waveforms for QRS peaks detection. We expect that the low-power dual-path design of this AFE IC can enable it to periodically record both the AC and the DC signals for proper sensing and calibration for various bio-sensing applications.
文摘The analog frontend(AFE)coupling circuit is a crucial processing element for data acquisition systems based on analog-to-digital converters(ADCs).Currently,high-speed and high-resolution ADCs are predominantly designed with differential input stages.Conventional highspeed ADC drivers are mainly AC-coupled by employing transformers(Baluns)or fully differential amplifiers(FDAs)with blocking capacitors.However,the results of this study indicate that a certain degree of DC offset error exists and manifests itself as the baseline error in the presence of power dividers connecting several DC-coupled channels that implement high-dynamic-range(HDR)signal conditioning.The study involves a theoretical analysis and explanation of the baseline offset error.The offset error can potentially lead to unexpected out-of-range issues for sampling devices,including high-speed ADCs and switched capacitor array ASICs.High-performance FDAs are adopted,and an offset-free DC-coupled AFE circuit is proposed to address the aforementioned issue using twostage amplification and a resistive attenuator.The proposed methodology is verified via circuit simulations and hardware design.Thus,the baseline offset problem can be accurately solved using the proposed circuit by minimizing the neglectable error.The proposed circuit facilitates improvements in the high-precision measurement of HDR signals in many nuclear physics experiments and some applications in the DC-coupling scheme with FDAs involving resistive power dividers.
