International Business Machines Corporation

Daniel E Skooglund

Dale E Hoffman

Algirdas J Gruodis

Michael Anthony Sorna

Jeffrey Herbert Fischer

Albert Y Chang

Lawrence Joseph Grasso

Charles A Puntar

David K Johnson

Diane K Young

A current source circuit that operates advantageously in the linear region of an FET and that minimizes any voltage drop at its output node which is not load related. The circuit operates under the principle that the output current is dynamically measured without introducing any elements that affects the voltage drop across the FET. Its current source includes a pass device with feedback control, such that a constant current is obtained regardless of the load placed at the output terminal. The operation of the pass device is mirrored by a second pass device having physical dimension that only a fraction of those of the first pass device. A high input impedance differential amplifier, driven by the respective outputs of the first and second pass devices, forces the mirror pass device to the identical voltage as the first pass device.

Active, low Vsd, field effect transistor current source

A driver circuit is disclosed for use in testing bi-directional transceiver semiconductor products using a minimum of time and number of product accessing pins. The driver includes a pair of controllable amplitude current sources whose output currents are selectably switched into or partially away from the commonly connected emitters of a current switch. The current switch is energized by a variable voltage source and produces the output test voltage.

Driver circuit for testing bi-directional transceiver semiconductor

A method of operating a delay circuit to impose a selected delay on an electronic signal the delay circuit comprising a plurality of delay stages and means for directing the electronic signal through selected ones of the delay stages, the method comprising the steps of: measuring the actual signal delay through each of the delay stages; and selecting, based on the signal delays obtained in the measuring step, the delay stages through which the electronic signal is directed.

Programmable delay line utilizing measured actual delays to provide a

Disclosed is a method and circuit for reducing and maintaining constant overshoot in a high speed driver. The circuit includes a predriver circuit which is driven single endedly and a driver circuit which is differentially driven by the predriver outputs. The predriver and the driver are differential pairs, with commonly controlled individual transistor current sources. A diode has been added in series with each emitter of the differential pairs. Schottky diodes are preferable because of their low capacitance. The diodes increase the input switching voltage (the smallest input voltage swing that will cause the outputs to fully switch) of the differential pair because they must also be switched on and off. The increase results in an increase in effective transition time, which results in smaller overshoots because the circuit is being switched slower. The output amplitude of the driver is set by a voltage which controls the current source currents of the commonly controlled current sources. As the amplitude is decreased the input switching voltage decreases because the current through the devices decreases which results in smaller base-emitter and diode voltages. Due to the commonly controlled current sources, the predriver amplitude decreases as the driver amplitude decreases. The predriver is designed such that its variable output supplies the driver with the proper input switching voltage at any driver amplitude. This keeps the effective input transition time constant which results in constant output overshoot.

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Wappingers Falls, NY, United States of America

Daniel E Skooglund