Design and Analysis of Current Differencing Transconductance Amplifier

Abstract

The current-mode devices play a vital role in the designing of the analog signal processing applications. Since the introduction of these devices, the continuous improvement in the performance parameters has been the most important aspect of research. As current differencing transconductance amplifier (CDTA) is used as a versatile circuit for designing different applications of analog signal processing like filters, oscillators, Schmitt triggers, monostable multivibrators etc., hence there has been a need of enhancing the performance of conventional CDTA. If all the performance parameters of the CDTA, the transconductance plays the most important role in deciding the performance of the designed applications and thus the enhancement of transconductance of CDTA is required while keeping in mind the other parameters. Thus, this research works includes the techniques to boost the transconductance of the conventional current differencing transconductance amplifier. Four different circuits to enhance the transconductance are proposed. All these circuits use a common source amplifier and merged it with some of the techniques to boost the transconductance. The different techniques applied are the use of parallel n- MOSFETs in the differential pair and a pair of cross-coupled n-MOSFETs across the differential pair. All the circuits are operated at the supply voltages of ±0.9 V. The comparison between all the proposed circuits is also done on the basis of transconductance and dynamic power and the best circuit was chosen as PCCDTACS. The maximum transconductance of 6.75 mS was achieved for PCCDTACS at a bias current of 200µA with the dynamic power of 3.44 mW. The proposed circuits have been designed and simulated in Cadence Virtuoso Analog Design Environment using BSIM3V3 180 nm CMOS technology. The comparison of the proposed PCCDTACS circuits with circuits available in literature shows that the proposed PCCDTACS circuit can be extensively used in the designing of analog signal processing applications.