Patent ID: 6373266
Filing Date: 2002-04-16
Classification: G01R

Abstract:
An apparatus for determining whether actual widths of resistors in an integrated circuit vary from design widths, comprising:(a) a reference resistor having a reference resistor design width; (b) a reference current source electrically coupled to said reference resistor; (c) a test current source, said reference current source and said test current source producing substantially equal currents; (d) a test series of resistors electrically coupled between said test current source and a ground, said test series comprising a test resistor having a test resistor design width disposed in series with a plurality of tuning resistors having substantially equal lengths, design widths, and depths, said reference resistor design width sized such that said reference resistor is less susceptible than resistors in said test series to resistance changes due to variations from design width; (e) a plurality of switches, each of said switches disposed in parallel with a different tuning resistor; and (f) a comparator having a first input electrically coupled to said reference resistor, a second input electrically coupled to said test series, and an output, whereby the resistance of said test series is variable to approximately match the resistance of said reference resistor by selectively triggering at least one of said switches when actual widths of resistors in said integrated circuit vary from said design widths.