Applications of Self Cascode in Low Voltage Analog Design

Abstract

Research in analog integrated circuits has recently gone in the direction of low voltage, low-power design, especially in the environment of portable systems where the use of low supply voltage, preferably a single-cell battery is mandatory. These low voltage structures need to have reduced power consumption so as to maintain a longer battery lifetime. In this area, traditional voltage-mode techniques are being substituted by the current-mode approach, which has the recognized advantage to overcome the gain bandwidth product limitation, typical of operational amplifiers. Then, they do not require high voltage gains and have good performance in terms of speed, bandwidth and accuracy. newline newlineInside the current-mode architectures, the current mirrors can be considered as the newlinebasic building block. The concept of the current mirror was developed specifically for analog integrated circuit biasing and is a good example of a circuit that takes advantage of the excellent matching characteristics that are possible in integrated circuits. The current sources employing transistors/MOSFETs have been used in analog integrated circuits as biasing elements as well as load devices for amplifier stages. newlineThese current sources are an essential and integral part of many electronic circuits newlineand they contribute to more than 50% of the applications where primary concern is to newlinesupply constant current to various active devices so that their operative point and design parameters are maintained throughout the operating range. newlineFurther, this current mirror is also an essential building block of a current newlineconveyor. Current Conveyors are particularly attractive in portable systems, where low voltage low-power constraints have to be taken into account. Recent advances in newlineintegrated circuit technology have also highlighted the usefulness of current mirror and current conveyor solutions in the implementation of various digital circuits and other signal processing applications.