This circuit for cars with fans was found in Silicon Chips documentation from the 90s. It is used to activate the fan when the radiator water temperature rises.
The figure shows how to use a varicap in a conventional tuning circuit. The circuit may be an...
This bridge circuit for the bench can have several uses. We found it in Radio Electronics magazine...
This VCO with a common operational amplifier was found in an old American documentation. The...