An Investigation into FGMOS circuits for signal processing

Abstract

The trend towards low-voltage/ low-power analog circuits has been growing immensely due to increased demand of smaller size and longer battery life for all portable applications. Meanwhile, single chip implementation of both analog and digital systems in mixed-signal systems is recommended for improved performance, lower cost and smaller size. However, single-chip systems are not only difficult to design and implement but also face a new critical constraint imposed by voltage scaling in the sub-micron CMOS technology in recent years. In digital circuit design, low-power consumption can be achieved by low supply voltage but this is not always the case for analog circuit design. As a result, low-power and low-voltage analog circuit solutions are essential for the development of single-chip systems. The use of floating-gate MOSFETs (FGMOS) in analog circuit research has steadily increased due to their great potential for low-voltage/ low-power design and compatibility with CMOS process technology. The FGMOS transistors are also widely used in analog and mixed signal circuits because the threshold voltage of FGMOS can be easily reduced without device scaling and any structural modifications. In this thesis, several FGMOS based circuits such as voltage-controlled resistors, current-to-voltage and voltage-to-current converters, variable transresistance amplifier have been developed. FGMOS based analog computational circuits such as reciprocal circuit, current-mode dividers, pseudo-exponential function generator and squarer have also been addressed in this work. The proposed circuits can be extensively used in the area of lowvoltage signal processing. All the proposed circuits have been simulated using ORCAD PSPICE and the results are compared with the existing circuits to demonstrate the effectiveness of the proposed circuits.