Found in a 90s Siliconix documentation, this high voltage power supply uses components from that time. MOSFETs can be current equivalents.
This circuit is from a 1982 documentation. Here we have an adaptation of the circuit already...
The integrated circuit used in this small transmitter is not very common today. The coil has its...
Like the previous circuits, this one uses a small speaker as a microphone and has two...