This circuit can detect static charges or extremely low voltages. The circuit was found in ancient American documentation and makes use of a JFET. A BF245 which is a more modern transistor can be used.
This circuit is from American documentation from 1973. It can be used to indicate when the logic...
This circuit is from an old documentation. However, it can be mounted with modern equivalent...
This interesting circuit, found in an old American publication, measures alternating signals in a...