This circuit is from an old documentation, making use of an operational of the time. The circuit can be adapted to use modern components. The power supply must be symmetrical.
This FET voltmeter is from an old 1974 amateur radio publication. The circuit can use MPF102 or...
This indicator was found in a 1974 publication, but it can be fitted with the BC548 transistor or...
This circuit was found in the comparator's own documentation, serving others in the same series. The...