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Monotonic Digital-To-Analog Converter Without Precisely Matched Resistors

IP.com Disclosure Number: IPCOM000040028D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01

Publishing Venue

IBM

Related People

Authors:
Frushour, JE Schrader, RE [+details]

Abstract

Standard digital-to-analog converter (DAC) configurations often have large positive or negative steps when a number of bits are turned off and the next most significant bit is turned on. A described circuit avoids this problem by not turning off the lower-order bits, and utilizing a second DAC. The circuit was used to solve a problem in which a DAC with a 600 mv range was required to be monotonic and have a resolution of 1.2 mv. The problem however was that resistor and transistor matching tolerances available on the integrated circuit chip were not adequate for the desired range. This problem occurred on the circuit when DAC bits 0-7 were switched off and bit 8 was switched on (bit 8 = most significant bit). This step caused either a large positive or large negative step to occur.