Abstract: This paper describes the design and analysis of a fully differential, gain-enhanced CMOS telescopic operational transconductance amplifier (OTA) used in a pipeline analog-to-digital converter (ADC).Specifications of the OTA are derived from the requirements of ADC.Simulation shows that for a 1pF load capacitance, this OTA achieves a high DC gain (approximately 145dB) and a wide unity-gain bandwidth (above 750MHz) at a phase margin 58°.In a configuration where the closed loop-gain is 4, the design spends about 18ns for settling with 0.05% accuracy.Simulations of this design are performed in SMIC CMOS 0.18μm technology.

Key words: OTA, gain-boost, CMFB