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PROGRAMMABLE RESISTOR VOLTAGE DIVIDER THAT SAVES AREA IN THE PHYSICAL CONSTRUCTION USED IN AN INTEGRATED CIRCUIT

IP.com Disclosure Number: IPCOM000013405D
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-18

Publishing Venue

IBM

Abstract

A very common circuit that is used on many integrated circuits is a programmable resistor voltage divider. The normal practice is to use FET 1 transistors as switches to select the resistors that are connected together to form the voltage divider. For best accuracy, the resistance of the FET switches must be much smaller than the resistors they are switching into and out of the circuit. If the resistors are of value 5 K ohms then the FET switch must be of resistance 5 ohms for an accuracy of 0.1%. An FET switch of this size can use many square microns of chip area. The circuit described below allows good accuracy without the requirement of very large FET switches. Referring to the above circuit diagram, some of the major components are identified.