Low voltage, low power CMOS analog circuit design techniques for mobile, portable VLSI applications

In the past decade, CMOS technology has played a major role in the rapid advancement and the increased integration of VLSI systems. CMOS devices feature high input impedance, extremely low offset switches, high packing density, low switching power consumption, and most importantly, they are easily scaled. With the reduction of the device minimum feature size, in order to prevent the transistor from breakdown because of the higher electrical field across the gate oxide and to ensure its reliability, the power supply voltage is necessary to be reduced.; With the reduction of the device minimum feature size, more and more transistors can be fabricated into a single chip. Nevertheless, the large amount of circuits integrated in a chip result in huge power consumption. Decrease of the supply voltage can not only ensure the device reliability, but also reduce power consumption in a significant amount. Furthermore, portable/mobile electronic equipments have become the trends of the present and future market demands. Low power supplies are the requirements of the portable/mobile electronic products.; In this dissertation, we focus on the low-voltage, low-power CMOS circuit design. Each circuit either features a rail-to-rail common-mode input voltage and/or consumes very low power. These circuits target applications in mobile telecommunications (rail-to-rail strong-inversion circuits) and in (portable) medical applications (low-power weak-inversion circuits). Three CMOS low-voltage rail-to-rail V-I converters are introduced. In each of the rail-to-rail V-I converters, an N-type V-I converter cell is connected in parallel with its P-type counterpart to achieve common-mode rail-to-rail operation. Based on the same approach for the rail-to-rail V-I converter, a rail-to-rail multiplier and a rail-to-rail input stage of a Differential Difference Amplifier (DDA)) are also designed accordingly. The rail-to-rail V-I converter and multiplier can be used as a basic building block to construct rail-to-rail analog computational circuits, and DDA-based analog circuits can provide a competitive design choice to Op-Amp-based circuits.; Through the use of the rail-to-rail V-I converter, a low-voltage 5th-order elliptic low-pass GM-C filter is designed. Because of the rail-to-rail OTAs inside, the resultant filter also has a rail-to-rail common-mode input voltage. This low-pass filter is designed for the application in baseband mobile/wireless communication. A V-I converter and a multiplier structures, which can work in either the weak-inversion or the strong-inversion saturation region, are described. By tuning the resistance value inside, the same circuit can work in both of these two regions. The weak-inversion V-I converter is applied into the design of a micropower weak-inversion GM-C filter. Because it is working in the weak-inversion region and its output current is in the {dollar}nA{dollar} level, only small capacitance is needed. Thus, a single-chip solution for a very low frequency filter is feasible. The cutoff frequencies of two weak-inversion low-pass filters cover the entire range of speech, so they are suitable for speech signal processing and medical hearing applications, such as integrated speech systems for hearing aids.; A low-voltage weak-inversion Variable Gain Amplifier (VGA) is described. The (VGA) circuit is basically comprised by an exponential converter, a four-quadrant analog multiplier, and an Operational Current Amplifier. Its applications are on the speech, audio signal processing and (portable) medical systems. Results are presented for all of these circuits.