Found in a 90s Popular Electronics, this touch switch uses a single sensor. PLLs are common today. Observe the supply voltage range.
We found this circuit in an article in Electronics Now magazine from March 1996. The frequency is limited...
This circuit provides a good audio power from a signal at least 1 V of amplitude. The MOSFET must...
This converter can be used to send information remotely from linear transducers, converting...