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Author

Chen Gao

Bio: Chen Gao is an academic researcher from University of Electronic Science and Technology of China. The author has contributed to research in topics: Instrumentation amplifier & Amplifier. The author has an hindex of 1, co-authored 3 publications receiving 2 citations.

Papers
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Journal ArticleDOI
TL;DR: A modified chopping structure is proposed to mitigate the mismatch effect of the pseudoresistors, and a successive-approximation based capacitor trimming loop is exploited to enhance the CMRR performance primarily.
Abstract: High common-mode rejection ratio (CMRR) with concurrent electrode offset rejection is essential for physiological signal acquisitions. This article presents a CMRR enhancement technique for ac-coupled instrumentation amplifiers (ACIAs), where the mismatch of passive components limits the CMRR performance primarily. A modified chopping structure is proposed to mitigate the mismatch effect of the pseudoresistors, and a successive-approximation based capacitor trimming loop is exploited. Fabricated in a 0.18- $\mu \text{m}$ CMOS technology, the ACIA draws $2.3~\mu \text{A}$ from a 1.2-V supply and exhibits 3.2- $\mu \text{V}\mathrm {_{rms}}$ input-referred noise over 0.5–400 Hz. The measured prototypes achieve > 110-dB CMRR at 50/60 Hz without any off-chip tuning.

8 citations

Journal ArticleDOI
TL;DR: In this article, a commonmode replication (CM-REP) technique was proposed to improve the CMRR and input CM impedance simultaneously by eliminating the CM current flow and its mismatch effect.
Abstract: High common-mode rejection ratio (CMRR) of an analog front end (AFE) requires high intrinsic CMRR of the front-end amplifier with high input common-mode (CM) impedance. This article presents a common-mode replication (CM-REP) technique, which replicates the input CM voltage over the front-end amplifier. By eliminating the CM current flow and its mismatch effect, CM-REP improves CMRR and input CM impedance simultaneously. Implementation considerations regarding the input CM range, on-chip, and off-chip parasitics have been discussed with practical techniques incorporated with the proposed CM-REP. Fabricated in a 0.18-μm CMOS technology, the measured instrumentation amplifier (IA) exhibits >130-dB CMRR and 50-GΩ input CM impedance at 50/60 Hz concurrently. The >110-dB CMRR is achieved with input CM up to 900 mVpp and >102-dB total CMRR (TCMRR) is obtained with 1-MΩ || 10-nF mismatch of source impedance. The prototype consumes 1.86 μA from a 1.8-V supply and occupies an active area of 0.227 mm².

3 citations

Proceedings ArticleDOI
01 Feb 2020
TL;DR: Interfacing with high-impedance sensors, such as dry-contacted electrodes and accelerometers requires high CMRR with sufficient input impedance concurrently, and feedback regulation of the power supply is often sophisticated and power-consuming.
Abstract: Interfacing with high-impedance sensors, such as dry-contacted electrodes and accelerometers requires high CMRR with sufficient input impedance concurrently. From the system point of view, the total CMRR (TCMRR) is determined by the intrinsic CMRR (ICMRR) of the front-end amplifier as well as the imbalance of source impedance; the latter has to be accommodated by large input common-mode (CM) impedance (Z IN , CM). Widely adopted CMRR enhancement techniques, i.e., chopping, common-mode feedback (CMFB), common-mode feedforward, improve ICMRR only [1]–[3]. Positive feedback improves the input differential-mode (DM) impedance (Z IN , DM) effectively [4]. However, it is the input CM impedance that contributes to the TCMRR, which has not been commonly noted. Single-ended amplifiers, e.g., active electrodes (AE) [3], [5], and traditional 3-opamp instrumentation amplifiers do not suffer from the confusion, where the Z IN , CM and Z IN , DM are inherently the same and are enhanced by the same mechanism for higher TCMRR. On the other hand, dedicated single-ended stages require extra design effort as well as power consumption. Pre-charge techniques improve Z IN , CM and Z IN , DM concurrently at low frequencies by employing two additional chopped buffers [6]. Power-supply regulation enhances both CMRR and (Z IN , CM). However, feedback regulation of the power supply is often sophisticated and power-consuming [7].

1 citations

Proceedings ArticleDOI
28 May 2022
TL;DR: In this article , an 8-channel bio-potential front-end with multi-channel common-mode replication (MC-CMR) has been implemented in a standard CMOS 0.18-$\mu$m process, and the measurement results show that the amplifier has an adjustable gain of 46 to 64 dB, the input reference noise within 1Hz to 1k Hz is 1.62$\mu \mathrm{V}{R}
Abstract: For a multichannel bio-potential signal acquisition front-end, it's total CMRR (TCMRR) is restricted by these three factors: the inherent CMRR (ICMRR) of the amplifier used in the acquisition front-end, the impedance mismatch of electrodes, and the systematic mismatch due to the shared reference electrode. This paper presents a 8-channel bio-potential front-end with multi-channel common-mode replication(MC-CMR). The frontend has been implemented in a standard CMOS 0.18-$\mu$m process, and the measurement results show that the amplifier has an adjustable gain of 46 to 64 dB, the input reference noise within 1Hz to 1k Hz is 1.62$\mu \mathrm{V}_{\mathrm{r}\mathrm{m}\mathrm{s}}$, TCMRR of the front-end is 100dB (at 50Hz). A single channel consumes 1.86$\mu$A at 1. 8V supply voltage, and the NEF is 2.7.

Cited by
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Journal ArticleDOI
TL;DR: In this paper , the authors presented a high commonmode rejection ratio (CMRR), and high power-supply rejection ratio(PSRR) current-mode instrumentation amplifier (CMIA) to overcome the limitations of existing differential voltage second-generation current conveyors (DVCCII)-based CMIAs in achieving high CMRR.
Abstract: Abstract This study presents a high common-mode rejection ratio (CMRR), and high power-supply rejection ratio (PSRR) current-mode instrumentation amplifier (CMIA) to overcome the limitations of existing differential voltage second-generation current conveyors (DVCCII)-based CMIAs in achieving high CMRR. The design is based on a fully differential second-generation current conveyor block with a novel circuit design following by a current subtracting stage. The CMIA is designed and laid out in 130 nm CMOS technology operating under ± 1.2 V supply voltage in Cadence software. The post-layout simulation results show that the CMIA achieves low-frequency voltage and current CMRR- BW of 228.8 dB–10 kHz and 246 dB–10.6 kHz, respectively, with PSRR + /PSRR- of 108.2 dB/99.7 dB, power consumption of 507 µW, and a core area of 0.0015 mm 2 . The unique quality of the circuit is that, it does not need well-matched active blocks, but inherently improves CMRR, bandwidth, and PSRR; hence it gains an excellent choice for integration.

2 citations

Journal ArticleDOI
01 Jan 2022
TL;DR: In this article , the authors proposed a commonmode replication (CM-REP) technique, which replicates the input common-mode voltage over the front-end amplifier to improve CMRR and input CM impedance simultaneously.
Abstract: High common-mode rejection ratio (CMRR) of an analog front end (AFE) requires high intrinsic CMRR of the front-end amplifier with high input common-mode (CM) impedance. This article presents a common-mode replication (CM-REP) technique, which replicates the input CM voltage over the front-end amplifier. By eliminating the CM current flow and its mismatch effect, CM-REP improves CMRR and input CM impedance simultaneously. Implementation considerations regarding the input CM range, on-chip, and off-chip parasitics have been discussed with practical techniques incorporated with the proposed CM-REP. Fabricated in a 0.18- $\mu \text{m}$ CMOS technology, the measured instrumentation amplifier (IA) exhibits >130-dB CMRR and 50- $\text{G}\Omega $ input CM impedance at 50/60 Hz concurrently. The >110-dB CMRR is achieved with input CM up to 900 mV pp and >102-dB total CMRR (TCMRR) is obtained with 1- $\text{M}\Omega \|$ 10-nF mismatch of source impedance. The prototype consumes $1.86~\mu \text{A}$ from a 1.8-V supply and occupies an active area of 0.227 mm 2 .

2 citations

Proceedings ArticleDOI
28 Oct 2022
TL;DR: In this paper , a Capacitively-Coupled Chopper Instrumentation Amplifier (CCIA) with embedded DC feedback is proposed to reduce the noise of system.
Abstract: This paper presents a low noise and low power circuit for neural recording. A Capacitively-Coupled Chopper Instrumentation Amplifier (CCIA) with embedded DC feedback is proposed to reduce the noise of system. Implemented a continuous-time low-pass filter (LPF) at the output of the system and utilized bulk-feedback techniques to increase its output swing. Furthermore, the DC-block and Chopper-Capacitor-Chopper Integrator Based DC Servo Loop (C3IB-DSL) are combined to reduce the interferences. According to experiment, the circuit consumes only 0.3 µW at 1.2 V. In addition, the input-referred noise reached 2.1 µVrms and the noise efficiency factor (NEF) 3.6 at the same time. The proposed CCIA was simulated in a 180n CMOS process.
Proceedings ArticleDOI
26 Nov 2022
TL;DR: In this paper , an operational transconductance amplifier (OTA)-based self-biased, ultra-low power instrumentation amplifier is proposed, which produces a fixed gain of 61 dB with unity gain bandwidth of 4.1 KHz and input RMS noise voltage of 2.01 μV.
Abstract: In this article, an operational transconductance amplifier (OTA)-based self-biased, ultra-low power instrumentation amplifier is proposed. The design is performed in SCL 0.18 μm technology under 0.6 V power supply. The total current drawn from the supply is 144 nA, resulting in ultra-low power consumption of 86 nW. The entire circuit is self-biased by an in-built current reference circuit. The instrumentation amplifier produces a fixed gain of 61 dB with unity gain bandwidth of 4.1 KHz and input RMS noise voltage of 2.01 μV rms . The amplifier is aimed for bio-medical applications and is capable of amplifying a signal as low as 0.5 μV with an ultra-low frequency of 1 Hz also, serving the range of even the weakest possible bio-potential signal quite efficiently.