This circuit uses a diode as a radiation sensor. The operational ones are old because the publication is from the 80's, but modern low voltage equivalents can be tested.
This circuit was found in a 1980s documentation. It decodes by identifying a certain frequency tone...
This circuit was found in a documentation by A. Fanzeres making use of a grounded metal housing...
We can obtain the characteristics of an operational amplifier with FET by adding FETs common to the...