1. Journal Articles

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A 0.3-V, 2.4-nW, and 100-Hz fourth-order LPF for ECG signal processing
(2020) Rao G. H.; Sreenivasulu P.; Rekha S.; Bhat M.S.
An ultra-low voltage, low power bulk-driven voltage follower (VF) is proposed in this paper. Further, it is exploited to design a fourth-order low-pass filter (LPF) for electrocardiogram (ECG) signal processing. The filter is designed in UMC 180-nm CMOS technology and operates with an ultra-low supply voltage of 0.3 V. It consumes an extremely low power of 2.4 nW for a cutoff frequency of 100 Hz. Results of post-layout simulation show that the proposed filter provides a dynamic range (DR) of 51.6 dB even from a 0.3-V supply voltage. The filter achieves a Figure-of-merit (FoM) of 4.7 × 10−15, which is better than many designs listed in the literature. © 2020 John Wiley & Sons, Ltd.
A 0.3?V, 56?dB DR, 100?Hz fourth order low-pass filter for ECG acquisition system
(2019) Sreenivasulu, P.; Hanumantha, Rao, G.; Rekha, S.; Bhat, M.S.
This paper proposes an extremely low voltage, low power bulk-driven voltage follower (BD-VF). As an application of the proposed BD-VF, a 4th order low-pass filter (LPF) with cutoff frequency adjustable from 50 Hz to 250 Hz is designed for electrocardiogram (ECG) acquisition systems. The filter is implemented in UMC 180 nm CMOS technology occupying only 0.03 mm2 area. Post layout simulation results show that the filter offers 56 dB dynamic range even with an extremely low supply voltage of 0.3 V. The total power consumption of the filter is 4.8 nW for a cutoff frequency of 100 Hz. The Figure-of-merit (FoM) and capacitance/pole of the filter are 5.7 10?15 and 2.2 pF respectively. The proposed filter offers the lowest FoM compared to the state-of-the-art nW-class filters. 2019 Elsevier Ltd
A 0.8-V, 55.1-dB DR, 100 Hz Low-Pass Filter with Low-Power PTAT for Bio-Medical Applications
(2019) Hanumantha, Rao, G.; Rekha, S.
This paper presents a power efficient transconductor-capacitor ((Formula presented.)) filter for front-end processing of bio-medical signals. A low voltage, low-power transconductor with improved output resistance is proposed. It offers a transconductance ((Formula presented.)) of 5.85 nS while operating at a supply voltage ((Formula presented.)) of 0.8 V. Furthermore, a low-power Proportional to Absolute Temperature (PTAT) current reference circuit is designed to bias the transconductor and to make (Formula presented.) independent of temperature. It follows PTAT characteristics in the temperature range of ?20 (Formula presented.) C to 70 (Formula presented.) C and is less sensitive to (Formula presented.) variations. A second-order Butterworth low-pass filter (LPF) with a cutoff frequency of 100 Hz is implemented to validate the proposed transconductor and the PTAT circuit. The filter is designed in UMC 65 nm CMOS process and it takes an area of 0.065 mm (Formula presented.). While consuming a power of 47 nW, it offers a dynamic range (DR) of 55.1 dB. Figure-of-merit (FoM) of the filter is as low as (Formula presented.) J, which is found to be on par with the filters reported in the literature. 2019, 2019 IETE.
1,3,4-Trisubstituted pyrazole bearing a 4-(chromen-2-one) thiazole: Synthesis, characterization and its biological studies
(2015) Harikrishna, N.; Isloor, A.M.; Ananda, K.; Obaid, A.; Fun, H.-K.
A new series 3-{2-[N?-(1,3-disubstituted-1H-pyrazol-4-yl-methylene)-hydrazino]-thiazol-4-yl}-chromen-2-one (10a-l) was synthesized by a multi-step reaction. All the synthesized compounds were characterized by IR, NMR, and mass spectral studies, followed by elemental analysis. The newly synthesized thiazole compounds were screened for their in vitro antibacterial and antifungal studies against various microorganisms. Antimicrobial studies carried out by the well diffusion method, showed a very good zone of inhibition for both bacteria (at a range of 20-50 mm diameter) and fungi (at a range of 10-30 mm diameter). Minimum Inhibitory Concentration (MIC) required for the 100% inhibition of bacteria and fungi was found to be as low as 15.6 ?g ml-1 for a few of the synthesized compounds. The Royal Society of Chemistry 2015.
1,5-Dibromo-2,4-dimethoxybenzene
(2012) Vijesh, A.M.; Isloor, A.M.; Gerber, T.; Brecht, B.V.; Betz, R.
In the title compound, C8H8Br2O2, all non-H atoms lie essentially in a common plane (r.m.s deviation of all fitted non-H atoms = 0.0330 ). In the crystal, weak C-H?O hydrogen bonds connect the molecules, forming chains which extend along the b-axis direction.
1-(4-Bromophenyl)-2-(2-chlorophenoxy)ethanone
(2012) Shenvi, S.S.; Isloor, A.M.; Gerber, T.; Hosten, E.; Betz, R.
In the title compound, C14H10BrClO2, a twofold halogenated derivative of phenylated phenyloxyethanone, the least-squares planes defined by the C atoms of the aromatic rings subtend an angle of 71.31 (17) . In the crystal, C-H?O contacts connect the molecules into chains along the b-axis direction.
1-[(3-Benz-yloxy-2-nitro-phen-oxy)meth-yl]benzene
(2012) Fun, H.-K.; Arshad, S.; Ubaradka, S.R.; Shetty, P.; Isloor, A.M.
The asymmetric unit of the title compound, C20H17NO4, consists of two crystallographically independent mol-ecules. In one of the mol-ecules, the central benzene ring forms dihedral angles of 2.26 (6) and 58.68 (6) with the terminal benzene rings and the dihedral angle between the terminal benzene rings is 56.45 (6) . The corresponding values for the other mol-ecule are 35.17 (6), 70.97 (6) and 69.62 (6) , respectively. In the crystal, an inversion dimer linked by a pair of C-H?O hydrogen bonds occurs for one of the unique mol-ecules. C-H?? and ?-? [centroid-centroid distances = 3.7113 (8) and 3.7216 (7) ] inter-actions link the components into a three-dimensional network.
1-[5-Acetyl-2,6-dimethyl-4-(5-phenyl-1H-pyrazol-3-yl)-1, 4-dihydropyridin-3-yl]ethanone monohydrate
(2012) Isloor, A.M.; Malladi, S.; Sundershan, S.; Gerber, T.; Hosten, E.; Betz, R.
In the title compound, C20H21N3O 2 H2O, the aza-substitued six-membered ring adopts a L4 B conformation. In the crystal, classical N-H?O, N-H?N and O-H?O hydrogen bonds connect the entities into a three-dimensional network. Intramolecular C-H?O contacts are also observed.
1-Cyclohexyl-5-(4-methoxyphenyl)-1H-pyrazole-4-carboxy-lic acid
(2011) Fun, H.-K.; Quah, C.K.; Chandrakantha, B.; Isloor, A.M.; Shetty, P.
In the title compound, C17H20N2O 3, the meth-oxy-phenyl unit is disordered over two sets of sites in a 0.715 (4):0.285 (4) ratio. The pyrazole ring forms dihedral angles of 55.88 (16) and 72.6 (4) with the benzene rings of its major and minor components, respectively. The cyclohexane ring adopts a chair conformation and its C-N bond is in an equatorial orientation. In the crystal, molecules are linked into inversion dimers by pairs of O-H?O hydrogen bonds, generating R 2 2(8) loops..
1-Dibromomethyl-4-methoxy-2-nitrobenzene
(2009) Fun, H.-K.; Goh, J.H.; Chandrakantha, B.; Isloor, A.M.
The asymmetric unit of the title compound, C8H 7Br2NO3, comprises two crystallographically independent molecules (A and B). The nitro groups are twisted from the attached benzene rings, making dihedral angles of 39.26 (9) and 35.90 (9) in molecules A and B, respectively. In each mol-ecule, the dibromo-methyl group is orientated in such a way that the two Br atoms are tilted away from the benzene ring. An inter-esting features of the crystal structure is the two short Br?Br inter-actions which, together with inter-molecular C - H?O hydrogen bonds, link the molecules into an extended three-dimensional network. The crystal structure is further stabilized by weak C - H?? inter-actions. Fun et al. 2009.
1-Hexyl-3-Methylimidazolium Chloride-Potassium Carbonate Aqueous Two Phase System: Equilibrium Characteristics and BSA Partitioning Behavior
(2014) Regupathi, I.; Monteiro, S.L.
The partitioning behavior of the model protein (bovine serum albumin) was investigated in ionic liquid (1-hexyl-3-methylimidazolium chloride) -salt (potassium carbonate) based aqueous two phase system (ATPS). The phase diagram with binodal curve and tie lines for the selected ATPS was developed at different temperatures and analyzed through effective excluded volume (EEV) and Othmer-Tobias and Bancroft equations, respectively. The influence of various process parameters like the ionic liquid and salt concentration, system temperature, tie line length, phase volume ratio, and neutral salt addition on partition coefficient/extraction efficiency of BSA protein was evaluated. 2014 Copyright Taylor & Francis Group, LLC.
A 1.8 V 8.62 W Inverter-based Gain-boosted OTA with 109.3 dB dc Gain for SC Circuits
(2019) Kaliyath, Y.; Laxminidhi, T.
This paper presents a low-power inverter-based gain-boosted operational transconductance amplifier (OTA) for switched capacitor (SC) circuits operating at higher supply voltage (>1 V). The proposed OTA is implemented using UMC 180 nm CMOS technology with a supply voltage of 1.8 V and it offers a high dc gain with a unity gain bandwidth (UGB) suitable for audio applications. All the transistors of the proposed OTA are operated in sub-threshold region to minimize the power consumption. Gain-boosting technique is employed to achieve a higher dc gain. The post-layout simulations demonstrate the robust performance of the proposed OTA, which delivers a high dc gain of 109.3 dB and a UGB of 5.29 MHz at 81 phase margin (PM) with a capacitive load of 2.5 pF for a typical process corner at room temperature (27 C). The proposed OTA draws a quiescent current ((Formula presented.)) of 4.79 A, resulting in a power consumption of 8.62 W. 2019, 2019 IETE.
1.8 V, 25.9 nW, 91.86 dB dynamic range second-order lowpass filter tunable in the range 4-100 Hz
(2019) Reddy, J.R.M.K.; Laxminidhi, T.
A second-order lowpass Butterworth filter with tunable bandwidth capable of offering a dynamic range of 91.86 dB operating on a supply voltage of 1.8 V is presented. The proposed filter is based on a sub-threshold source follower. The transistor bias currents are switched to enable the bandwidth tuning in the range 4-100 Hz. A proportional to absolute temperature (PTAT) current reference circuit helps to keep the bandwidth intact across process, voltage and temperature variations. The filter, designed in 0.18 ?m standard CMOS process, consumes 25.9 nW making it a potential candidate for portable biomedical applications. The Institution of Engineering and Technology 2019.
A 10 kW ZVS integrated boost dual three-phase bridge DC DC resonant converter for a linear generator-based wave-energy system: Design and simulation
(2019) Harischandrappa, N.; Bhat, A.K.S.
The design and performance analysis of a 10 kW three-phase DC DC LCL-type resonant converter having a built-in boost function were carried out. This high-power converter is proposed for its application in grid-interfacing a linear generator (LG)-based wave-energy system. Fixed-frequency control is used, and the converter was designed to operate with a lagging power factor. It is shown that all switches turn on with zero-voltage switching (ZVS) for wide input voltage and load variations. This results in reduced switching losses and stresses, which is very important in large-power applications. The performance of the converter was studied through PSIM simulation software. Theoretical and simulation results are presented for comparison. Power-loss break-down analysis of the designed converter was carried out and the summary of results is presented. 2019 by the authors. Licensee MDPI, Basel, Switzerland.
A 10-Bit Differential Ultra-Low-Power SAR ADC with an Enhanced MSB Capacitor-Split Switching Technique
(2019) Polineni, S.; Bhat, M.S.; Rajan, A.
A fully differential energy-efficient switching scheme for binary-weighted capacitor digital-to-analog converter (DAC) is presented. It is observed that the proposed switching scheme reduces energy consumption of DAC by 97% and the capacitance area by 50% over the conventional ones. The effect of supply and common mode voltage variations on the linearity of successive approximation register (SAR) analog-to-digital converter (ADC) is reduced. Moreover, with this switching scheme, one can achieve the same dynamic range as the conventional one, with half the supply voltage as compared to the existing schemes. This makes the proposed switching method suitable for ultra-low-voltage SAR ADCs, which are widely used in biomedical applications. The proposed method is modelled using MATLAB. The results show that the nonlinearity (INL and DNL) caused by capacitor mismatch is reduced. The circuit-level implementation of 10-bit SAR ADC is simulated using UMC 90nm CMOS 1P9M process technology. 2018, King Fahd University of Petroleum & Minerals.
11.39 fJ/conversion-step 780 kS/s 8 bit switched capacitor-based area and energyefficient successive approximation register ADC in 90 nm complementary metal-oxide- semiconductor
(2018) Narasimaiah, J.D.; Tonse, L.; Bhat, M.S.
In this study, a design technique for low-energy consumption and area-efficient successive approximation register analogue-to-digital converter (ADC) is presented. Digital-to-analogue conversion equivalent voltage is acquired utilising passive sharing of charge between two unit capacitors and integration of the shared charge onto an input sample-and-hold capacitor, via a switched capacitor integrator circuit. The architecture is less parasitic sensitive and low noise, yielding an area and energyefficient ADC. To demonstrate the efficacy of the proposed technique, a 350 mV 8 bit 0.78 MS/s ADC is designed in a 90 nm complementary metal-oxide-semiconductor process. The ADC core has a small area footprint of 0.00145 mm2 and has a figure-of-merit of 11.39 fJ/conv-step. 2018, The Institution of Engineering and Technology.
14.5 fJ/conversion-step 9-bit 100-kS/s nonbinary weighted dual capacitor array based area and energy efficient SAR ADC in 90 nm CMOS
(2018) Narasimaiah, J.D.; Bhat, M.S.
In this work, design technique and analysis of low-energy consumption successive approximation register (SAR) analogue-to-digital converter (ADC) is presented. A dual capacitor array (CA) generates a digital-to-analogue reference voltage with increased accuracy. The CA supports multiple parallel operations to enhance conversion speed. Unit sized capacitors in CAs are few in number and present good capacitance density, thereby providing area efficiency and ease of routeing. A 9-bit SAR ADC using the proposed dual CA, implemented in a 90 nm CMOS process, has a small core area footprint of 0.00371 mm2. At a 1 V supply and 100 kS/s, the ADC achieves a signal-to-noise and distortion ratio of 53.55 dB and consumes 0.47 ?W, resulting in a figure-of-merit of 14.5 fJ/conversion step. The Institution of Engineering and Technology 2018.
(1Z)-1-(2,4-Dichloro-phen-yl)ethan-1-one semicarbazone
(2009) Fun, H.-K.; Balasubramani, K.; Vijesh, A.M.; Malladii, S.; Isloor, A.M.
In the title compound, C9H9Cl2N 3O, the semicarbazone group is approximately planar, with an r.m.s deviation from the mean plane of 0.011 (2) . The dihedral angle between the least-squares planes through the semicarbazone group and the benzene ring is 38.76 (9) . The crystal structure is further stabilized by N - H?O and C - H?O hydrogen bonding. Fun et al. 2009.
2,4-Dichlorobenzyl 2-methoxybenzoate
(2013) Isloor, A.M.; Garudachari, B.; Gerber, T.; Hosten, E.; Betz, R.
In the title compound, C15H12Cl2O 3, the aromatic rings make a dihedral angle of 10.78 (4) . In the molecule, there is a short C-H?O contact. In the crystal, C-H?O contacts connect the molecules into C(7)C(8) chains along the b axis. The shortest intercentroid distance between two benzoic acid aromatic systems is 3.7416 (8) .
2,6-Dichloro-3-nitro-pyridine
(2011) Fun, H.-K.; Arshad, S.; Chandrakantha, B.; Isloor, A.M.; Shetty, P.
The asymmetric unit of the title compound, C 5H 2C l2N 2O 2, consists of two crystallographically independent mol-ecules. The pyridine ring in each mol-ecule is essentially planar, with maximum deviations of 0.004 (4) and 0.007 (4) . Short Cl?O [3.09 (3) and 3.13 (4) ] and Cl?Cl [3.38 (12) ] contacts were observed. No significant inter-molecular inter-actions were observed in the crystal packing. Fun et al. 2011.