Devarshi Mrinal Das

A novel low-noise fully differential CMOS instrumentation amplifier with 1.88 noise efficiency factor for biomedical and sensor applications

In this paper, we present a novel instrumentation amplifier (INA) topology for mobile bio-medical data acquisition platforms. The proposed INA features a PMOS-NMOS complimentary transistor input pair biased in sub-threshold region to effectively boost the transconductance of the input pair and reduce the input referred noise. There are two embedded common-mode feedback circuits which help to establish the common-mode voltages without consuming extra power. One is at the output of the first stage (i.e. at the drain connection of the complimentary transistors) and the other at the final output stage. The INA provides a measured gain of 40dB and a bandwidth of 11kHz. The measured integrated noise is 0.78 µ V rms (50mHz to 11kHz) with measured CMRR of greater than 100dB. The proposed amplifier is versatile and hence capable of conditioning various bio-potential signals like Electrocardiogram (ECG), Electroencephalogram (EEG), Electromyogram (EMG) and Electrooculogram (EOG) as well as signals produced from sensors. A prototype chip has been fabricated in UMC 180nm mixed-mode CMOS technology operating at 1.8V power supply and occupying an area of 415 × 230 µ m 2 . The simulation and experimentally measured results are presented in this paper. NEF (noise efficiency factor) of 1.88 is obtained from measurement results. Hence the amplifier features for the first time a very low NEF (1.88) and high CMRR ( 100 dB ). A compact ExG conditioning and acquisition system has been developed and used to measure ECG, EEG, EMG and EOG signals from human subjects by deploying the proposed INA.

Design considerations for high-CMRR low-power current mode instrumentation amplifier for biomedicai data acquisition systems

This paper presents a design procedure for practical implementation of current mode instrumentation amplifier (CMIA). The design flow highlights the major tradeoffs in the design of CMIA, enabling a designer to optimize the design as per the desired critical performance specifications. PSRR analysis of the implemented CMIA is also presented. The target specifications comprise a CMRR better than 100 dB without using choppers and without trimming, programmable bandwidth, accurate and stable gain, rail to rail output swing with 100 pF capacitive load driving capability while minimizing the power dissipation and the area. The gain is programmable from 34 dB to 60 dB and the bandwidth is programmable upto 10 kHz. The thermal noise floor is 145 nV/√Hz. The presented chopper-less CMIA has been designed and optimized in 180 nm mixed-mode CMOS technology. It features high CMRR of > 112 dB in the presence of 4.5 mV input offset voltage without any chopper modulator.

A noise-power-area optimized novel programmable gain and bandwidth instrumentation amplifier for biomedical applications

In this paper, we are presenting a novel programmable gain and bandwidth instrumentation amplifier (PGB-INA) for biomedical applications. By virtue of its programmable gain and bandwidth, it can measure various bio-potentials such as ECG, EMG, EOG, etc. The proposed PGB-INA also features an extremely low input referred noise (1.34 μVrms within the integration bandwidth of 50 mHz to 11 kHz) and high CMRR (84 dB). The design is fabricated in 180 nm mixed-mode CMOS technology. The PgB-INA provides a measured programmable gain and bandwidth of 30 to 40 dB and 100 Hz to 2.7 kHz, respectively. The PGB-INA occupies die area of only 150 μm × 200 μm and consumes 18.3 μΑ current from 1.8 V supply. Various bio-potentials are measured using the proposed PGB-INA such as ECG, EMG and EOG which are also presented in the paper.

LNA-LO Co-design Considerations for Low Intermediate Frequency Receivers in 401-406 MHz MedRadio Spectrum for Healthcare Applications

This work proposes low noise amplifier (LNA) and local oscillator (LO) co-design considerations for low intermediate frequency (IF) receivers (RX) in the Medical Device Radiocommunication (MedRadio) band (401-406 MHz), which is used for biomedical applications. Supported with the analysis, proposed considerations are the experimental outcomes of measurements and characterization of fabricated ICs, which are not directly available in any of the previously published works. A phenomenon of IF shift with respect to received RF power level is explained for a practical RX system by presenting a detailed model for the parasitics of packaged integrated circuits (ICs) and printed circuit board (PCB). A general equation for the lower bound of IF (f_IFmin) is derived for a given maximum input RF power (P_inmax) in the presence of parasitic capacitances, which ensures a fixed IF. Measurement results of a low IF RX (Design1) show that f_IFmin is 1.96 MHz for Pinmax of -35 dBm and total parasitic capacitances of 1.7 pF, which matches with the proposed analytical model. A low IF RX (Design2) was also fabricated in 180 nm mixed mode CMOS technology by using the proposed considerations. The measurement results of Design2 show that problem of IF shift was completely removed and the IF remains fixed at 1.2 MHz even when the Pinmax is much more than -35 dBm.

High energy oxygen irradiation-induced defects in Fe-doped semi-insulating indium phosphide by positron annihilation technique

Positron annihilation technique is applied to study the recovery of radiation-induced defects in 140 MeV oxygen (O6+) irradiated Fe-doped semi-insulating indium phosphide during annealing over a temperature region of 25∘C–650∘C. Lifetime spectra of the irradiated sample are fitted with three lifetime components. Trapping model analysis is used to characterize defect states corresponding to the de-convoluted lifetime values. After irradiation, the observed average lifetime of positron τavg = 263 ps at room temperature is higher than the bulk lifetime by 21 ps which reveals the presence of radiation-induced defects in the material. A decrease in τavg occurs during room temperature 25∘C to 200∘C indicating the dissociation of higher order defects, might be due to positron trapping in acceptor-type of defects (VIn). A reverse annealing stage is found at temperature range of 250∘C–425∘C for S-parameter probably due to the migration of vacancies and the formation of vacancy clusters. Increase in R-parameter from 325∘C to 425∘C indicates the change in the nature of predominant positron trapping sites. Beyond 425∘C, τavg, S-parameter and R-parameter starts decreasing and around 650∘C, τavg and S-parameter approached almost the bulk value showing the annealing out of radiation-induced defects.

Design and measurement techniques for a low noise amplifier in a receiver chain for MedRadio spectrum of 401–406 MHz frequency band

This work presents design and practical techniques to measure specifications of a low noise amplifier (LNA) in a complete receiver chain at Medical Device Radio Communication (MedRadio) band in 401–406 MHz frequency range. Supported by detailed quantitative explanations, the proposed measurement methods help in characterizing the LNA without duplicating it on the chip only for the characterization and promises to save experimental time and cost. A common source inductively degenerated LNA has been designed and fabricated in 180 nm mixed mode CMOS technology. The measurement results show that the LNA consumes 700 μW power while giving a voltage gain of 31 dB, S11<-14 dB and noise figure of 5.8 dB at 400 MHz frequency. Complete receiver chain measurements with this LNA confirms the results from the proposed methods.

A mismatch insensitive reconfigurable discrete time biosignal conditioning circuit in 180 nm MM CMOS technology

This paper presents a discrete time fully differential CMOS signal conditioning circuit for acquisition of biosignals. It is realized using switched capacitors (SC), which provides reconfigurability, high precision, high CMRR and low sensitivity to temperature and process variations. However, the SC circuit suffers from various errors like charge injection and clock feedthrough which have an impact on the precision of the signal sensing. Moreover fully differential circuit is very sensitive to capacitor mismatch leading to degradation of CMRR. To overcome this limitation, a new circuit configuration is presented, which uses the concept of error averaging. As a result, the circuit achieves minimum CMRR of 90 dB for frequencies in the range of 40–60 Hz, even in the presence of 0.1% capacitor mismatch, along with process and temperature variations. Simulation results show the worst case relative output error of ± 0.57% and ± 0.9% with DC and time varying input common mode voltage respectively. Also, the circuit achieves 10-bit resolution, even with capacitor mismatch and input common mode variations.

SAW resonator oscillator based injection locked OOK transmitter for MedRadio spectrum

This work presents a low power injection locked on-off keying (OOK) transmitter (TX) for the Medical Device Radio (MedRadio) communication band (401-406 MHz), which is suitable for health care applications. The TX is based upon a surface acoustic wave resonator (SAWR) oscillator, which directly generates a stable RF signal at 403.6 MHz and completely removes the power hungry frequency multiplying circuits from the transmitter. Designed and fabricated in 180 nm mixed mode CMOS technology, the measurement results of the SAWR oscillator show that it consumes 400 μA current from 1 V supply and exhibits a phase noise of about -101 dBc/Hz for center frequency of 403.6 MHz at an offset of 300 kHz. The post layout simulation results show that the output radiated power from the proposed TX is -17 dBm while consuming total power of 940 μW.

Bio-telemetry and bio-instrumentation technologies for healthcare monitoring systems

This work presents a review of advancements made in the areas of bio-telemetry and bio-instrumentation for healthcare applications, especially for remote health monitoring in developing nations. This paper presents a comprehensive study of suitable wireless, analog and RF IC technologies, their challenges and limitations, recent researches and future directions in these areas. As an outcome of this study, a prototype of a healthcare monitoring unit (HMU) has been also proposed by using commercial ICs in accordance with the recommendations given by the wireless planning commission (WPC) in India. Using the proposed HMU, bio-signal capturing and communication is demonstrated in home and infirmary environments. Supported with the practical implementation results for actual constraints and conditions, this work promises to give the scholars a quick start for their research in the area of remote healthcare monitoring.