A 12b 250 MS/s Pipelined ADC With Virtual Ground Reference Buffers

The virtual ground reference buffer (VGRB) technique is introduced as a means to improve the performance of switched-capacitor circuits. The technique enhances the performance by improving the feedback factor of the op-amp without affecting the signal gain. The bootstrapping action of the level-shifting buffers relaxes key op-amp performance requirements including unity-gain bandwidth, noise, open-loop gain and offset compared with conventional circuits. This reduces the design complexity and the power consumption of op-amp based circuits. Based on this technique, a 12 b pipelined ADC is implemented in 65 nm CMOS that achieves 67.0 dB SNDR at 250 MS/s and consumes 49.7 mW of power from a 1.2 V power supply

Design port and optimization of a high-speed SAR ADC comparator from 65nm to 0.11[mu]M

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, June 2011."May 2011." In title on title page, "[mu]" appears as lower case Greek letter. Cataloged from PDF version of thesis.Includes bibliographical references (p. 50-51).As the world continues to do more and more of its signal processing digitally, there is an ever increasing need for high speed high precision signal processors in consumer applications such as digital photography. Technological progress in CMOS fabrication has allowed chips to be made on nano scale processes, but this still comes at a steep price. Especially in chips for which analog components are a priority over digital components, some of the benefits of using nano scale processes diminish, such as smaller area. In these cases, it is worth investigating whether the same performance can be achieved with larger feature size, and therefore, cheaper processes. To that end, a three-stage comparator circuit for use in a digital camera SAR ADC has been ported from its original 65nm process to a 0.11[mu]m process. Its design has been analyzed and performance presented here. Additionally, an alternative latch-only architecture for the comparator has been designed and analyzed. In 0.11[mu]m the three-stage comparator operates at the same speed, 13% lower RMS noise contributing 0.9 bits difference, and 11% higher power than the original in 65nm. More noteworthy, the 0.11[mu]m latch-only comparator operates at 40% higher speed, equivalent noise, and 72% lower power.by Nora Iordanova Micheva.M.Eng