1.5-V Linear CMOS OTA with -60dB IM3 for High Frequency Applications

A novel configuration of linearized Operational Transconductance Amplifier (OTA) for low-voltage and high frequency applications is proposed. By using double differential pairs and the source degeneration structure under nano-scale CMOS technology, the nonlinearity caused by short channel effect from small feature size can be minimized. A robust common-mode control system is designed for input and output common-mode stability, and thus reduces distortion caused by common-mode voltage variation. Tuning ability can be achieved by using MOS transistors in the linear region. The linearity of the OTA is about -60dB third-order inter- modulation (IM3) distortion for up to 0.9 VPP at 40 MHz. Ths OTA was fabricated by the TSMC 180-nm Deep N-WELL CMOS process. It occupies a small area of 15.1 x 10-3 mm2 and the power consumption is 9.5 mW under a 1.5-V supply voltage.