This circuit can be used as an amplifier for musical instruments or even with your cell phone. The circuit is old and was found in the 1990 edition of Radio Electronics Experimenter magazine.
This amplifier for automotive use was found in the SGS manual of linear integrated circuits of...
This circuit was found in documentation from the 70s. We can try current JFET transistors....
This circuit makes use of a thermometric sensor that heats or cools according to a current of air....