This simple Bargraph photometer with 4 LEDs was found in a 1997 documentation. The scale is adjusted in a trimpot and the sensor can be any common LDR. Power can be supplied by cells or battery.
This circuit is from Motorola's Linear Interface ICs from 1993. The circuit uses a booster...
Found in a 90s Popular Electronics, this circuit is intended for amplifying analog video signals....
The figure shows a NOR or Non-OU logic function shield using general purpose diodes and a common...