This circuit converts BCD inputs to analog voltages. The operational amplifier must be powered according to the desired output voltage range. The circuit is from documentation from the 90s.
In the figure we have a bistable multivibrator using an operational one. The circuit is from old...
This is another of the Star Trek red alert circuit that you can find on this site. We took this...
This circuit for testing zener diodes by lifting their curve on an oscilloscope was presented in...