| 摘要 |
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.
|
