Design of high frequency OTA in 130nm CMOS technology with single 1.2V power supply

In this paper, a CMOS operational transconductance amplifier (OTA) for low power supply voltage and VHF continuous time filtering applications is described. The input stage of the proposed circuit is based on CMOS inverters. The transconductance of OTA is tuned using the bulk effect of transistors. A tuning circuit is also discussed. A good frequency behavior of the described OTA is obtained due to the lack of internal nodes. In order to enhance a DC voltage gain of the open loop OTA, a negative resistance circuit is employed. This circuit is also tuned. The proposed amplifier was designed and simulated using the UMC (United Microelectronic Corp., Taiwan) 130 nm process with the 1.2 V supply voltage. The OTA was used in the application of a third order Gm - C elliptic filter. SPECTRE simulation results show the cutoff frequency of about 800 MHz and the THD less than -40 dB for the output voltage up to 0.5 Vpp.