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Analog to Digital Converter

IP.com Disclosure Number: IPCOM000073693D
Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Croisier, A: AUTHOR

Abstract

The coding mode and coding device described deals with a new type of pulse code modulation, similar to delta modulation, but in which the positive and negative current sources which charge and discharge the integrator capacity are replaced, respectively, by the positive voltage to be encoded and the negative reference voltage. The integrating capacity is charged by a current proportional to the input voltage, and discharged by a current proportional to a reference voltage. The coder delivers a binary pattern, the decoding of which is equal to the ratio of the input voltage over the reference voltage.

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Analog to Digital Converter

The coding mode and coding device described deals with a new type of pulse code modulation, similar to delta modulation, but in which the positive and negative current sources which charge and discharge the integrator capacity are replaced, respectively, by the positive voltage to be encoded and the negative reference voltage. The integrating capacity is charged by a current proportional to the input voltage, and discharged by a current proportional to a reference voltage. The coder delivers a binary pattern, the decoding of which is equal to the ratio of the input voltage over the reference voltage. The encoder shown in Figure A, is organized as a delta coder, except that the positive and negative current sources, which respectively charges and discharges the integrator capacity are replaced, respectively, by the positive voltage V(x) to be encoded and the negative reference voltage - V(y). The comparator checks the voltage across capacity C and resets the latch at each clock pulse, so that this voltage is constantly brought back to zero.

In the following, it is assumed that V(x) is a steady voltage over a large time interval T. Let m and n be, respectively, the number of 0 and 1 delivered by the encoder during interval T. Over T, a negligible average amount of charge enters or leaves capacitor C. m V(x) - n V(y) = 0. Since the probability P of having an 1 at the coder output is:

P = n over n + m we get: V(x) over V(y) = n over m = P...