Subash Chandra Bose

Bio: Subash Chandra Bose is an academic researcher from Central Electronics Engineering Research Institute. The author has contributed to research in topics: CMOS & Charge pump. The author has an hindex of 4, co-authored 6 publications receiving 27 citations. Previous affiliations of Subash Chandra Bose include Academy of Scientific and Innovative Research & Council of Scientific and Industrial Research.

A Novel Design Methodology for High Tuning Linearity and Wide Tuning Range Ring Voltage Controlled Oscillator

Abstract: This paper presents a novel design methodology of a CMOS current starved ring Voltage Controlled Oscillator (VCO) for wide tuning range and high linearity. The f-V tuning characteristic of the ring VCO depends on the current-voltage (Ibias-Vcontrol) characteristic of the replica bias and region of operation of current sources/sinks transistors (CSTs). The proposed design methodology linearizes the Ibias-Vcontrol characteristic and ensures the CSTs to operate in saturation region during switching and consequently enhances the tuning range without additional circuitry. The design is implemented in UMC 0.18 μm CMOS technology at 1.8 V supply voltage. The overall circuit consumes 260 μW power at 404.5 MHz, has a wide tuning range of 66 MHz to 875 MHz having 94.5% tuning linearity.

A Novel Fluorometric Bio-Sensing-Based Arsenic Detection System for Groundwater

Abstract: Arsenic that adversely affects human health is frequently reported in certain regions in India and other parts of the world. A low cost, portable, and eco-friendly field test system is required to monitor the levels of arsenic in drinking water procured from different tube wells and open wells. This paper presents the construction of biosensor strain by transforming E. coliDH $5\alpha $ with the plasmid pJSKV51 carrying in-frame promoter operator region as well as entire arsR gene, part of arsD gene and enhanced green fluorescent protein (EGFP) gene. This strain was able to induce EGFP in presence of arsenic III ion. This paper further presents a novel EGFP-based bio-electronic sensing methodology to develop a low-cost battery operated system to measure the fluorescence emitted by biosensor strain and display the numerical values of the concentrations of arsenic in water samples. In this method, a blue light of 480 nm excites the EGFP to produce a green fluorescence signal in proportion to arsenic concentration. The developed device includes a compact embedded system to measure the signal fluorescence using light sensor, programmable controllers and liquid crystal display to show the corresponding concentration of the arsenic in ppb. The experimental results show that the system can detect and display over a range from 5 to 100 ppb.

Ultra low power 12-Bit SAR ADC for wireless sensing applications

Abstract: This paper presents a 12-bit SA-ADC for portable low power wireless sensor systems. The proposed SA-ADC operates for rail-to-rail input range and achieves low power consumption. Split capacitor array based DAC and a novel charge-integration based dynamic comparator are used for low power consumption of the ADC. Measured DNL and INL are −0.59/0.67 LSB and −1.2/1.33 LSB respectively. At sampling rate of 100-kS/s with 1.8-V supply, the ADC consumes only 2-μW power and achieves a SNDR of 64.42-dB, SFDR of 71.2-dB resulting in an FoM of 14-fJ/Conversion-step. The ADC core occupies an area of 0.238-mm2 and is fabricated in AMS 0.35-μm CMOS technology.

DC Offset Modeling and Noise Minimization for Differential Amplifier in Subthreshold Operation

Abstract: This work presents the rigorous formulation of input referred offset voltage for differential amplifier, having the input pair devices in subthreshold region of operation. The formulation has been verified in 0.35 μm and 0.18 μm CMOS technologies by using Monte Carlo Simulation. Minimization of 1/f noise is the additional advantage of this method.

Characterization and Compensation Circuitry for Piezo-Resistive Pressure Sensor to Accommodate Temperature Induced Variation

Abstract: The paper presents a simple circuit for piezo-resistive pressure sensors which compensates the temperature dependency of sensors. The output of piezo-resistive sensors generally, decreases with the increase in temperature when subjected to constant voltage excitation. To control the change with temperature, a varying excitation method is used. The proposed technique utilizes current steering DACs and a digital controller to compensate the variations. The technique is experimentally verified at hardware level where the digital control circuit is implemented on FPGA and tested with ASICs comprising of interface circuit. For the purpose of compensation, temperature is sensed using the same sensor. The temperature resolved is less than 1 °C for a range of 10 °C to 70 °C with zero pressure correction technique. The test results for implementation show that the sensitivity and offset shift is compensated by a factor of 10 and 44 respectively. The complete fabricated chip, consisting of interface circuit and algorithm occupies 10 mm2 area.

Analysis and design of current starved ring VCO

Abstract: This paper focuses on and analysis and design of current starved voltage controlled ring oscillator. The analysis includes effect of delay time, phase noise, layout area, technology etc. on the frequency of oscillation at various power supplies and control voltages. The simulation results shows that the circuit has higher tuning range and low power consumption suitable for various application domains. Added benefit of this VCO is to maintain a constant amplitude level and oscillation. It is also proved here that the frequency of oscillation is inverse of the supply voltage and therefore consuming less power.

An Analog Front-End for a Multifunction Sensor Employing a Weak-Inversion Biasing Technique With 26 nVrms, 25 aCrms, and 19 fArms Input-Referred Noise

Abstract: An analog front-end (AFE) for a multifunction environmental sensor is proposed. The AFE is designed to be able to sense $1~\mu \text {V}$ , 1 fC, and 1 pA level signals in a low-frequency band around DC, and consists of an instrumentation amplifier (IA), a charge amplifier (CA), and a continuous time delta-sigma (CT- $\Delta \Sigma $ ) ADC. To reduce the low-frequency noise of operational amplifier (OPAMP) which is used for signal path, this paper proposes a weak-inversion biasing technique. The designed IA achieved 26 nVrms input-referred noise (IRN) in the band of 0.1–10 Hz with 0.22 mm2 die area. The designed CA achieved 25 aCrms IRN in charge sensing mode and 19 fArms IRN in current sensing mode in the band of 0.01–1 Hz, respectively, and occupies 0.12 mm2 die area. The AFE has been fabricated in a $0.18~\mu \text {m}$ CMOS process with 4.5 mm2 die area. The current consumption at 2.56 kHz output data rate (ODR) is 2.5 mA, reducing to $2~\mu \text {A}$ at 0.01 Hz ODR.

Design of Improved Performance Voltage Controlled Ring Oscillator

Abstract: Voltage Controlled Oscillator is one of the most important basic building block for analog, digital as well as in mixed signal circuits. This paper presents a new technique to improve the performance of ring oscillator. The VCO is based on single ended ring oscillator. The circuit is designed using 0.13 CMOS technology with supply voltage of 3.3 V. A VCO with high frequency range from 2.26GHz to 3.50 GHz is achieved by using this technique. Simulation results reveal the better performance of the proposed design as compared to existing current staved ring VCO in terms of oscillation frequency and power consumption.