| Analog-to-Digital Converter (ADC) microcircuits are required to meet stringent accuracy specifications in spite of their analog components' inherent nonidealities as well as the accuracy limitations due to fabrication technology. In this thesis, a 3-step Nyquist rate ADC is presented which makes use of bitstream processing to calibrate the digital-to-analog converter (DAC) and the residue amplifier, while using the same hardware to calibrate the sub-ADC. The system is designed to provide programmability and calibrate undesired circuit characteristics such as offset, gain error, and nonlinearity. Thus, the DAC can tolerate gain errors much higher than the standard amount, and has the potential to completely cancel nonlinearity and offsets in its transfer function. The offset of the residue amplifier can also be calibrated with this system. Moreover, the system eliminates the need for a reference ladder in the sub-ADC, and calibrates comparator offsets. Simulation and experimental results of the circuits fabricated in a 0.18mum CMOS process are presented. |
