With this circuit it is possible to control the intensity of a signal digitally. The circuit is from Radio Electronics from February 1981. The power supply must be 18 V.
We found this circuit in a technical documentation on the National Semiconductor LM3909. The...
The LEDs act as diodes, so if good they will show the same characteristic curve. Arrangment shown...
This circuit is from an old English publication from 1968. We can implement it with TIP32...