Integrated System Labratory

                Rasoul Ghasemi, Hamid Charkhkar, Alireza Asadi, and Reza Lotfi

The main objective in this research is analyzing the effects of non-linear capacitors (such as MOS capacitors (MOSCAPs)) in switched-capacitor circuits including pipeline ADCs and switched-capacitor filters when they are used instead of conventional integrated capacitors like MIM caps. Because of the voltage dependent behavior of these capacitors, it’s necessary to use compensation techniques to reduce this drawback.By using MOSCAPs there is no need to extra process layers and the analog part of a circuit can be made as well as digital one. So, the fabrication cost decreases significantly. On the other hand, by decreasing supply voltage in future technologies, MOSCAPs show less non-linearity.What we have done in our research is a theoretical analysis of non-linear effects of voltage dependent capacitors in a single 1.5-bit stage of a pipeline ADC. We also designed and simulated a 10-bit, 1.8V, 40MS/s pipeline ADC using compensated MOSCAPs. This ADC achieves 51 dB SNDR and 55.5 dB SFDR. Extracted from this research, one paper has been accepted to be presented in ICM’06. We have submitted a paper to ISCAS 2006. Now, we are working to enhance the theoretical analysis and also studying SO configurations that employ MOSCAPs.