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.
This is an interesting configuration obtained in an old circuit manual. The unijunction can be...
We have many versions of biofeedback with the 555 IC on this site. This is another one. We found it...
We have in the figure as a monostable a proximity switch where our body capacitance (estimated at 200...