Found in 90s Popular Electronics, this circuit fires a load through a MOSFET from an audio signal applied to the input. Power supply is done according to the load.
Bipolar transistors are types of general use like BC548, while the power MOSFET can be of any type...
We found this circuit in an old documentation. Its purpose is to turn on warning lights when the...
This simple humidity alarm circuit includes a timed warning oscillator whose time is set to R4....