APPLICATIONS OF ELECTRONICALLY TUNABLE OTA

Abstract

Over the past decade there has been increasing recognition of the importance of access to communication infrastructures and services for economic and social development. Generally, in communication systems, the processing of signal is accomplished in a single or a set of mixed-signal IC most of which are based on CMOS technology. OTA is a popular choice to implement filters, multipliers, oscillators, and several other important building blocks while satisfying the requirement of high frequency stability, wide input voltage range etc. In the field of electric and electronic engineering, oscillators play an important role and have been widely applied in various aspects such as communications systems, instrumentation, measurement and signal processing, etc. The concept of oscillator design has been mainly on the requirement of multiple sinusoids which are 90◦ phase shifted, called Quadrature signal, for easy implementation with other circuits for example in the design of SSB modulator, etc. From the past, there have been attempts to synthesis the sine wave oscillator in both forms of current and voltage mode. The Voltage-mode Quadrature oscillator using 3 operational transconductance amplifiers (OTAs) and 3 grounded capacitors and 3 grounded Resistor is presented. The proposed oscillator provides 2 sinusoidal output voltages with 90º phase difference. The condition of oscillation and the frequency of oscillation can be electronically controlled by adjusting the bias current of the OTA.