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Folded Pattern for Film Resistor with Trimmable Elements in Binary Sequence

IP.com Disclosure Number: IPCOM000050159D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Kiang, YC: AUTHOR [+2]

Abstract

A metal film pattern forms a ladder network with high resistance branches paralleling low resistance branches. A cut through the low resistance branch inserts the parallel high resistance into the circuit. The resistance portions are in a binary sequence so that the resistor can be adjusted to close precision over a wide resistance range. The ladder pattern is folded into a compact area.

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Folded Pattern for Film Resistor with Trimmable Elements in Binary Sequence

A metal film pattern forms a ladder network with high resistance branches paralleling low resistance branches. A cut through the low resistance branch inserts the parallel high resistance into the circuit. The resistance portions are in a binary sequence so that the resistor can be adjusted to close precision over a wide resistance range. The ladder pattern is folded into a compact area.

A precision resistor that is required for some circuits is often formed of a thin metal film that can be trimmed by means of a laser. In one technique, a high resistance length of metal is electrically paralleled at a number of points by a low resistance metal path. The resistor is trimmed to a selected value by cutting through the low resistance branch where the parallel high resistance branch is to be added to the total resistance value.

The drawing shows a pattern of a resistive metal that establishes a selected resistance between points 2 and 3. This path includes high resistance parts shown crosshatched and low resistance parts that are not crosshatched. The high resistance parts are of varying lengths to provide a binary sequence of resistances plus several units 4 of a uniform minimum length and a small resistance for a fine adjustment. Small holes can be formed in region 5 to increase the resistance by a small amount. The pattern can be a few hundred microns on a side. Thefilm thickness can be in...