Circuit arrangement for electronically generating a resistor setting and audio system based thereon
AssigneeAudio System DB AG
InventorJuerg Portmann
Life of this patent
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Abstract
A circuit arrangement for causing a resistor to assume a selectable value in which the resistor is photosensitive and optically isolated from the control circuitry used to drive a photodiode and so to generate the light which determines its resistance. The control circuitry includes a second photosensitive resistor arranged in a feedback loop and further arranged to be illuminated by a second photodiode in parallel with the first photodiode. The resistance value is selected by supplying the control circuit with an analog voltage signal which may be developed at the tap of a potentiometer either directly, or indirectly after conversion to a digital signal, storage, and eventual reconversion into an analog signal.
Claims17
A circuit arrangement comprising:
- means for generating a first control voltage;
- means for generating a second control voltage, and for varying said second control voltage in accordance with the resistance of an included first element whose resistance varies in accordance with an intensity of light incident upon said first element;
- first light generating means for illuminating said first element with light so that the resistance of said first element varies in accordance with the intensity of the light generated by said first light generating means;
- control output generating means, responsively connected to said means for generating said first control voltage and said means for generating and varying said second control voltage, for generating a control output in accordace with a difference between said first and second control voltages, said control output controlling said first light generating means so as to vary the resistance of the first element to such an amount that the difference between said first and second control voltages becomes zero;
- second light generating means, responsive to said control output, for generating light whose intensity varies with the magnitude of said control output;
- and
- a second element, arranged to be illuminated by said second light generating means, whose resistance varies in accordance with the intensity of light incident upon said second element, and so on the intensity of light generated by said second light generating means.
Dependencies are inferred from the claim text.