Found in old documentation, this circuit uses a double gate MOSFET. The operating frequencies depend on the coil, and the indicator is a microammeter.
Although there is an enormous amount of 12 V voltage regulator integrated circuits, it may be that...
This interesting circuit, found in an old American publication, measures alternating signals in a...
This buffer and driver is from the integrated circuit manual itself, the Linear Technology LT1206. The...