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Low Resistance Test Circuit

IP.com Disclosure Number: IPCOM000091921D
Original Publication Date: 1968-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Jeenicke, EH: AUTHOR

Abstract

This circuit tests and classifies an unknown resistance R as having a value either too high, too low, or within a desired range. R is connected between current source 10 and DC voltage amplifier 20 so that small variations in very small values of R vary the output of amplifier 20. Biasing voltage sources 30 and 40 are adjusted according to the acceptable range of values for R. Opposite conductivity type transistors 50 and 60 have a common base connection to R through amplifier 20 and resistor 70. Resistor 70 protects the one forward biased transistor 50 or 60. When the value of R equals or exceeds the high limit, only transistor 50 turns on. Similarly, transistor 60 turns on when R equals or falls below the low limit. When the value of R is within the tolerance set on biasing voltages 30 and 40, neither transistor is on.

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Low Resistance Test Circuit

This circuit tests and classifies an unknown resistance R as having a value either too high, too low, or within a desired range. R is connected between current source 10 and DC voltage amplifier 20 so that small variations in very small values of R vary the output of amplifier 20. Biasing voltage sources 30 and 40 are adjusted according to the acceptable range of values for R. Opposite conductivity type transistors 50 and 60 have a common base connection to R through amplifier 20 and resistor 70. Resistor 70 protects the one forward biased transistor 50 or 60. When the value of R equals or exceeds the high limit, only transistor 50 turns on. Similarly, transistor 60 turns on when R equals or falls below the low limit. When the value of R is within the tolerance set on biasing voltages 30 and 40, neither transistor is on. In an even more precise alternative, transistors 50 and 60 are replaced with operational amplifiers.

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