A folded cascode OTA using current-mode gain-boost amplifier

In this report, an OTA which is used in fully differential pipelined ADC was described. Using gain-boost architecture with current-mode single-ended amplifier, this OTA reduce parasitic taking by gain-boost amplifier to achieve high-gain and high-speed. Besides, a dual phase SC-CMFB circuit is introduced, and some methods are concerned to improve the performance. Then, by optimization the layout design, OTA's mismatch was reduced. This design was using SMIC 0.35um CMOS process and simulation both schematic and layout in Cadence. The result of the simulation shows that the OTA has a gain up to 105dB, a unity gain bandwidth of about 937MHz for a 2pF load, a settling time of about 4.4ns, a Common-Mode Range is 0.6V∼3.3V, a output swing is 0.6V∼3.1V, with the power supply of 3.3V, the dissipation is 39mW. This amplifier was used in a 10bit 100MHz pipelined ADC.