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 identifies the polarity of DC signals and if the signal is AC. The circuit is from...
In the figure we have a modified multiplier circuit that can operate with the sextuplicator with...
This circuit is from the Motorola Linear Databook published in 1990. The circuit for 1 kHz can be...