Found in a Popular Electronics from the 90s, this circuit can be used as an electrifier. T1 can be an old TV fly back transformer or an ignition coil.
This circuit simulates an inductor. Or operational amplifier of old type, but a configuration is...
We found this circuit in a 1967 Electronic Design. The circuit uses contemporary transistors that...
To control relays safely with double insulation, we suggest the circuit in the figure. The optical...