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High Speed Stored Level Digital to Analog Converter

IP.com Disclosure Number: IPCOM000096692D
Original Publication Date: 1963-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Kulikowski, RJ: AUTHOR

Abstract

This D to A converter continuously decodes when responding to high speed inputs. The undesirable output excursions resulting from input levels which are not applied for a full time interval is eliminated by storing the old analog output as the inputs are changing. This is accomplished either by charging or discharging a capacitor while the inputs are present.

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High Speed Stored Level Digital to Analog Converter

This D to A converter continuously decodes when responding to high speed inputs. The undesirable output excursions resulting from input levels which are not applied for a full time interval is eliminated by storing the old analog output as the inputs are changing. This is accomplished either by charging or discharging a capacitor while the inputs are present.

When all inputs to side A are at a negative voltage and all inputs to side B are at 0 voltage, all diodes are backbiased, the transistors Q1 and Q2 are non conducting. The E Out is at 0 volts resulting in no charge across capacitor C. When input levels, representative of a binary digital value, are applied to side B, one or more of the diodes become forwardly biased. This permits a voltage drop across RX determined by the ratio of RX to the equivalent selected resistance. The voltage drop across RX causes Q1 to conduct and apply a negative charge on C. When the input levels are removed, the diodes are again reversely biased. Q1 becomes non conducting and the charge remains stored on C representing the old analog input. As more significant input values are applied to side B, larger negative charges are applied to C resulting in corresponding larger negative outputs at E out.

When an input value occurs which is less significant than that applied to side B, the input levels are applied to side A. As on side B, one or more of the diodes become forwardly biased...