This small signal amplifier circuit was found in Motorola's 1969 documentation. The FET and the transistor can be of any type and is battery powered since the consumption is very low.
This circuit was published in an article in Radio Electronics magazine in October 1988. It uses...
This 3-component circuit uses an analog indicator. We found it in an old publication....
This simple circuit can be used to power a simple communication system using ordinary telephones....