A ratio-independent algorithmic analog-to-digital converter combining current mode and dynamic techniques

An algorithmic analog-to-digital converter (ADC) that combines current mode and dynamic techniques is presented. The converter does not rely on high-gain amplifiers or well-matched components to achieve high resolution and is inherently insensitive to the amplifier's offset voltage. An analysis of the converter's limitations indicates that the resolution of practical circuits will be limited by the switch-induced charge injection. Ultimately, however, the kT/C noise leads to an area/resolution tradeoff and the transistor's thermal noise leads to a speed/power tradeoff. A prototype fabricated using a 3- mu m CMOS process achieved 10-bit resolution at a sampling rate of 25 kHz on an area of only 0.18 mm/sup 2/.<
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