Faculty Publications
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Publications by NITK Faculty
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Item Effect of finite gain and bandwidth of feed-forward compensated OTA on active-RC integrators: A case study(2012) Rekha, S.; Laxminidhi, T.This paper analyses the effect of finite gain-bandwidth of the operational transconductance amplifiers (OTAs) on active-RC integrators. A feed-forward compensated OTA is taken as the building block of active-RC integrator. A mathematical analysis is carried out on a first order low-pass active-RC filter designed in 180 nm CMOS technology to operate at a supply voltage of 0.5 V. A non-ideality factor (NIF) has been defined that accounts for the deviation of the response from the ideal. Simulations performed on the transistor level filter justifies the mathematical analysis presented. © 2012 IEEE.Item Effect of parasitics of feed-forward compensated OTA on Active-RC integrators(2013) Rekha, S.; Laxminidhi, T.This paper analyzes the effect of parasitics of the Operational transconductance Amplifiers (OTAs) on Active-RC Integrators. The analysis is carried out for an Active-RC integrator built around a feed-forward compensated OTA designed in 180 nm CMOS technology to operate at a supply voltage of 0.5 V. A non-ideality factor (NIF) has been defined that accounts for the deviation of the response of the Active-RC integrator from the ideal. Simulations performed on the transistor level integrator justifies the mathematical analysis presented. © 2013 Springer Science+Business Media New York.Item Ultra low power active-RC filter in 180 nm CMOS technology(2013) Rekha, S.; Laxminidhi, T.This paper presents the design of a low voltage, ultra low power fifth order Chebyshev low pass filter operating at a power supply voltage of 0.5 V in 180 nm CMOS technology. A CMOS inverter based transconductor is used as the building block. A sub-threshold model is developed for the transconductor as the transistors are operating in sub-threshold region. A feedforward compensated OTA is designed using this transconductor and is used to realize the filter. Designed filter has a cutoff frequency of 150 kHz and offers a dynamic range of 54.16 dB with a figure of merit of 0.02 fJ. Power consumed by the filter is 21.79 microwatt. © 2013 IEEE.Item Widely programmable high-frequency active RC filters in CMOS technology(Institute of Electrical and Electronics Engineers Inc., 2009) Laxminidhi, T.; Prasadu, V.; Pavan, S.We propose a circuit technique that enables the realization of widely programmable high-frequency active RC filters in CMOS technology. A fifth-order Chebyshev ladder filter having a digitally programmable 3-dB bandwidth (from 44 to 300 MHz) is used as a vehicle to validate our ideas. The opamp uses feedforward compensation for achieving high dc gain and wide bandwidth. The integrating resistors are realized as a series combination of a triode-operated MOSFET and a fixed polysilicon resistor. A charge-pump-based servo loop servoes the integrating resistor to a stable off-chip resistor. The principle of "constant capacitance scaling"is applied to the opamp and the integrating resistors so that the shape of the frequency response is maintained when the bandwidth is scaled over a 7 7times; range. The filter core, designed in a 0.18-?m CMOS process, consumes 54 mW from 1.8-V supply and has a dynamic range of 56.6 dB. © 2009 IEEE.Item Low voltage, low power chebyshev filter in 0.18 ?m cmos technology(2013) Rekha, S.; Laxminidhi, T.This paper presents an active-RC continuous time filter in 0.18 ?m standard CMOS technology intended to operate on a very low supply voltage of 0.5 V. The filter designed, has a 5th order Chebyshev low pass response with a bandwidth of 477 kHz and 1-dB passband ripple. A low-power operational transconductance amplifier (OTA) is designed which makes the filter realizable. The OTA uses bulk-driven input transistors and feed-forward compensation in order to increase the Dynamic Range and Unity Gain Bandwidth, respectively. The paper also presents an equivalent circuit of the OTA and explains how the filter can be modeled using descriptor state-space equations which will be used for design centering the filter in the presence of parasitics. The designed filter offers a dynamic range of 51.3 dB while consuming a power of 237 ?W. © 2013 World Scientific Publishing Company.