Analog pre-processing circuit for analog-to-digital converters of the folding type

摘要

Two-step ADC with coarse flash converter. The thermometer output of the MSB converter is converted by a thermometer current DAC and subtracted from a current representing the input signal. The difference current is converted to voltage to generate the residue ( fig. 3-4 ). The coarse ADC and the DAC are implemented by a N-MOS and a P-MOS transistor for each thermometer bit ( fig. 5 ).