This circuit can work with almost any JFET. The circuit is from an Electronics Now from April 1993. It is powered by a 12 V battery, but can also be powered by 9 V.
This instrumentation amplifier with differential inputs was found in documentation from the 90s....
This circuit is from a Radio Electronics magazine from December 1958. The indicator instrument is analog...
Found in a 90s 303 Circuits, this circuit has an output power of 100 mW. L1 consists of 890 turns...