Comparative Analysis of Different Operational Transconductance Amplifiers

An operational-transconductance amplifier (OTA) is a type of amplifier that has the capability to convert an input voltage signal into an output current signal. Traditional Op-amp amplifies voltage signals directly while the OTA amplifies the current making it suitable for applications such as filters, voltage-controlled oscillators, and active filters. Similar to operational amplifiers, OTAs rely on both the supply voltage and gain. To maximize the advantage, the analog circuitry depends on various parameters such as bandwidth, common mode rejection ratio, gain, noise, and power consumption. High gain and less power consumption are preferred to fulfill the desired requirements. It is observed that the circuit which is based on the current mode is preferable as compared to the voltage mode. This paper analyzes and compares various operational-transconductance amplifiers while utilizing basic current mirrors, cascode, and cascade current mirrors. The OTA having a current mirror load and current sink shows better performance as it gives high gain and consumes less power. All three circuits are simulated in 90nm CMOS technology in Cadence Virtuoso.