Teradyne, Inc.

Michael R Ferland

William J Bowhers

Roger V Burns, Jr

J Anson Whealler, Jr

Apparatus for automatically testing electronic circuits and performing time measurements, including a time measuring circuit for counting clock pulses provided between stop and start event edges presented to it, two independent input selectors for each selectively connecting one of a plurality of its inputs to the time measuring circuit, and a plurality of local comparators located within the test apparatus near sources of signals to be timed and generating an event edge upon receiving a signal crossing a threshold value. Also disclosed are making time measurements of signals at digital and analog pins using local comparators connected to input selectors over deskewed transmission paths and connecting a local comparator to the filter output of an analog instrument.

Time measurement in automatic test equipment

A differential input selector for selectively connecting one of a plurality of differential inputs to a differential output, the selector including a plurality of pairs of differential input lines, a differential output bus, and a separately powerable differential amplifier connected to each pair of input lines, the amplifier being directly connected to the differential output bus, the amplifier being powered on and off to selectively connect the pair of input lines to the output bus.

Differential input selector

Apparatus for measuring the difference between two voltages in which a first current proportional to the voltage difference is generated at a first point, and there is circuitry for delivering at a second point a second current that is based on the first current and is indicative of the voltage difference; the circuitry includes an uninterrupted current path from the first point to the second point and the current path has a circuit element across which at least a portion of the common mode voltage appears; and the circuit element provides an output current to the path which is independent of the voltage across the circuit element.

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Nashua, NH, United States of America

Michael R Ferland