Design of a Novel Linear 3-Input CMOS OTA and Its Application to Filter Realization

A novel voltage-tunable linear 3-input CMOS Operational Transconductance Amplifier (OTA) suitable for on-chip integration of advanced monolithic system is described. When a 3-input OTA is needed, a conventional 3-input OTA uses two 2-input OTAs and grounds one of 4 input terminals. This paper presents a method to reduce the number of MOS transistors and to save chip area by designing a 3-input OTA directly. A CMOS pair technique is introduced as a solution to minimize a matching problem. Simulation results show that the active chip area of the proposed 3-input OTA is reduced by 23.7% compared to a conventional one. The proposed 3-input OTA is applied to a realization of an OTA-C filter to verify the effectiveness.