A 90-dB DC gain high-speed nested gain-boosted folded-cascode opamp

A novel folded-cascode operational amplifier (opamp) employing the nested gain-boosted technique is presented. The gain-booster in the signal path consists of two-level recursive folded-cascode amplifier to achieve high gain and high speed. The opamp is designed and simulated in 0.13μm CMOS technology, bode-plot results that an open-loop gain over 90dB and a unity-gain frequency up to 4.75G for loads of 1.6pF have been obtained. Settling measurements shows that the opamp has a settling time less than 2.5ns. So the proposed opamp can be employed in high speed and high resolution Analog-to-Digital converters (ADCs) such as pipelined ADC.