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Analog To Digital Conversion

IP.com Disclosure Number: IPCOM000074281D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Hartlipp, WE: AUTHOR

Abstract

A sawtooth wave and an Exclusive-OR circuit can be used to perform an analog-to-digital (A/D) conversion.

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Analog To Digital Conversion

A sawtooth wave and an Exclusive-OR circuit can be used to perform an analog-to-digital (A/D) conversion.

A voltage proportional to the analog data is brought into one leg of an Exclusive-OR circuit E-O. The other leg of E-O is conditioned by the output of a sawtooth generator ST-G which has a maximum amplitude equal to the maximum excursion expected on the data leg. E-O will supply a known output as long as its two input legs are at different potentials. This output will reverse itself for the instant that the two input legs are equal in potential, causing a pulse to be generated at the output of inverter I.

One method of using this pulse to accomplish the A/D conversion utilizes a counter C which is started at the same time as is ST-G, the output of 1 and C being fed to an AND circuit A. If, for example, the linear output of ST-G runs from 0 volts to 5 volts and C runs from 0 to 100 during the time of the sawtooth generation, then, if the analog data line were at 2.5 volts, the output pulse from E-O would be generated halfway through the count and a value of 50 would be read out at the output of A.

The accuracy of the A/D conversion is related to, and can be controlled by, the slope and linearity of the ST-G output and the speed with which C is running.

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