Design of single-stage folded-cascode gain boost amplifier for 14bit 12.5Ms/S pipelined analog-to digital converter

This paper describes the design and simulation of a fully-differential, high gain, high speed CMOS Operational Transconductance Amplifier (OTA). The op-amp is designed for unity gain sampler stage of 14bit 12.5Ms/s pipeline analog-to digital converter. The design is implemented using a folding cascode topology with the addition of gain boosting amplifiers for increased gain. Common-mode feedback (CMFB) is used to stable the designed OTA against temperature and other process variations. This design has been implemented in 0.13μm IBM RF mixed signal CMOS Technology. The Spectre simulation shows the DC gain of 91.5 dB and a unity-gain frequency of 714.5MHz with phase margin of 62° (double 7.5-pF load) while consuming 9 mW power. For the normal corner, the settling time to 1/2 LSB of 14bit A/D converter accuracy is 40 ns.