We found this precision circuit in a manual from the 80's. The operational amplifier is of a common type at the time, and equivalents can be tested. Transistors are general purpose types.
This sensitive circuit detects the live pole of a power grid or outlet. The circuit makes use of a high...
This FET stage circuit was obtained from old American documentation but can be applied to any FET....
Found in old American documentation, this circuit can use crystals between 27.5 and 33 MHz...