This nonlinear gain circuit was found in a 1965 Electronic Design. The configuration can be used as a basis for modern designs with equivalent transistors.
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...
This relay circuit with a dual channel MOSFET (not very common today) was found in an old American...
This application is not modern since few computers have parallel ports. But you can use this...