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Thomas H Warner

Charles H Cox

David P Misunas

Robert G Jacobsen

An I-V curve tracer measures an I-V relationship of an electrical device during transient conditions. In operation, the curve tracer couples across the device a fixed-value inductive or capacitive load. While the current and voltage flowing through the device approach steady-state levels, the voltage and current are sampled and stored in a memory upon predetermined incremental changes in one parameter of the device such as voltage. A digital representation of one parameter, such as voltage, constitutes a memory address and another parameter, such as current, is stored at that address in the memory. A data processor subsequently retrieves the memory data and addresses to display or plot the I-V relationship of the device. This parametric sampling technique assures that the measurements are coincident in occurrence with the sweeping of the I-V curve and eliminates the need for complex control and timing circuits.

I-V Curve tracer employing parametric sampling

In a noise reduction system of the type in which an audio signal is delayed in time to permit detection of and reaction to impulse noise before application of the audio signal to a loudspeaker or the like, a transformed version of the audio signal is compared with its time-averaged value, and a resulting detection signal is processed into a control signal with blanking periods that vary as a function of corresponding impulse noise. The detection produces a response to both large impulses which stand out from the audio signal and small impulses which are hidden in the audio signal. The control signal tailors its response to the size of the impulse, blanking the audio signal substantially only for the duration of the impulse. Auxilliary circuitry is provided.

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Cambridge, MA, United States of America

Thomas H Warner