Low Voltage Low Power Single Ended Operational Transconductance Amplifier for Low Frequency Applications

This paper presents the designing of a low voltage low power single ended operational transconductance amplifier (OTA) for low frequency application. The designed OTA combines three different schemes i.e. current splitting, current cancellation and source degeneration technique. Source degeneration method using resistor is one of the most simple and ubiquitous technique to linearize the transfer characteristics of OTA. Current splitting technique is utilized to reduce the transconductance of OTA and to improve the linearity. Current cancellation technique is used to further reduce the transconductance. The OTA circuit is operated in sub-threshold region due to the stringent power limitation requirement in integrated circuits. The transconductance of the OTA is 4.5nA/V with a linear range of +/-0.25V. To test the applicability of the proposed OTA, a fifth order Butterworth OTA-C low pass filter is realized. The circuit is operated at a supply voltage of +/-0.5V and the power consumption of the filter is 487nW. The DC gain of the filter is -6.1dB with a cutoff frequency of 250Hz. THD of -50.61dB of the OTA-C filter is obtained for a 100mV(pp) signal with 100Hz frequency. The circuit shows the best THD performance with less pass band attenuation for single ended filter circuit. The circuit is simulated in cadence environment using 150nm CMOS process technology.