Pipeline type analog to digital converter including plural series connected analog to digital converter stages

摘要

An A/D converter block A/D1 converts an analog input signal Vin to a digital signal and outputs its D/A output. First SH/SUBT7, 8 sample the signal Vin and a voltage VRM at the same timing with said A/D conversion and output the results of subtraction of the respective sampling values and the D/A output during holding, respectively. The both results of subtraction are several tens mV and there is no need of taking account of the linearity of a differential amplifier DIFF11. During the sampling, a circuit SHR1 outputs the differential voltages between each reference tap voltage taken out from specific 2 points of the ladder-type resistor in the A/D converter block A/D1 and the voltage VRM while a differential amplifier DIFF12 applies the reference voltages to the next A/D converter block A/D2. Such operations are performed in each stage. Thus, it becomes possible to make any S/H circuit and amplifier of excellent linearity in the first stage unnecessary to reduce the electric power consumption.