Ultra Low-power Operational Amplifier Research Articles

Ultra low-voltage ultra low-power memristor based band-pass filter design and its application to EEG signal processing

Memristor has been claimed as the passive fourth fundamental circuit element in 1971. About four decades later, a physical realization which presents memristor behavior has resulted in significant interest on memristor and it is continuing to increase at a growing rate. Memristor can provide new possibilities in analog circuit design thanks to its properties which cannot be mimicked by older passive circuit elements. Since no practically available memristor exist on the market yet, obtaining of a practical implementation which behaves like a memristor is important from the point of view real-world circuit design. In this paper, an ultra low-voltage ultra low-power DTMOS-based memristor design is presented. Ultra low-voltage, ultra low-power operational amplifier and ultra low-voltage, ultra low-power multiplier are also designed to use in the implementation. Memristor design is composed of these two type active blocks using CMOS 0.18 µm process technology with symmetric ?0.25 V supply voltages. Our memristor is used in a second order Sallen---Key band-pass filter topology. Designed memristor-based Sallen---Key band-pass filter is then used for real electroencephalogram data processing. The simulation results show that the design of adjustable memristor memristance/memductance provides tunable filter parameters and without any significant distortion with appropriate parameter set even at ultra-low power levels and at very-low frequencies.

A Highly Linear Fully Integrated Powerline Filter for Biopotential Acquisition Systems

Powerline interference is one of the most dominant problems in detection and processing of biopotential signals. This work presents a new fully integrated notch filter exhibiting high linearity and low power consumption. High filter linearity is preserved utilizing active-RC approach while IC implementation is achieved through replacing passive resistors by R-2R ladders achieving area saving of approximately 120 times. The filter design is optimized for low power operation using an efficient circuit topology and an ultra-low power operational amplifier. Fully differential implementation of the proposed filter shows notch depth of 43 dB (78 dB for 4th-order) with THD of better than -70 dB while consuming about 150 nW from 1.5 V supply.