A High-Speed Fully Differential Telescopic Op-Amp for Active Filter Designs in V2X Applications

In this paper, an ultra-wideband fully differential two-stage telescopic 65-nm CMOS op-amp is presented, which uses low-voltage design techniques such as level shifter circuits and low-voltage cascade current mirrors. The designed op-amp consists of two stages. While the telescopic first stage provides high speed and low swing, the second stage provides high gain and large swing. Common-mode feedback circuits (CMFB), which contain five transistors OTA and sensing resistors, are used to set the first-stage output to a known value. The designed two-stage telescopic operational amplifier has 41.04 dB lower frequency gain, 1.81 GHz gain-bandwidth product (GBW) and 51.9 degrees phase margin under 5 pF load capacitance. The design consumes a total current of 11.9 mA from a 1.2-V supply voltage. Presented fully differential two-stage telescopic op-amp by using low-voltage design techniques is suitable for active filter in vehicle-to-everything (V2X) applications with 120 mu m x 55 mu m layout area.