Varian Associates, Inc.

Arp Instruments, Inc.

Dennis P Colin

Alan R Pearlman

A logarithmic rf amplifier includes a plurality of cascaded stages each including a differential amplifier which performs full-wave rectification of the rf signal and a circuit for providing a video signal representative of the full-wave rectified rf signal. The logarithmic amplifier further includes a circuit for supplying rf signals of equal amplitude and opposite polarity to the inputs of the first differential amplifier stage and a circuit for summing the video signals from each of the stages and providing a logarithmic video output. The amplifier exhibits extremely fast pulse response and clean limiting.

Full wave, self-detecting differential logarithmic rf amplifier

A touch sensitive device is associated with at least one key of an electronic musical instrument such as an electronic organ, includes a layer of a pressure responsive, variable conductance material, and exhibits a switching action when subjected to pressure beyond a threshold pressure, any increase in pressure thereafter providing an increase in conductance up to a saturation pressure. The device may be used either as a combined switch and amplitude control or may be used in associated with one or more capacitors to provide either a high pass or low pass touch-control audio filter. In a totally polyphonic instrument a tone generator and touch-control filter are respectively associated with and responsive to each key depression, the output signal from each activated filter being coupled preferably to audio mixer circuitry.

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Beverly, MA, United States of America

Dennis P Colin