We found this circuit in the April 1993 Electronics Now magazine. Almost any general-purpose JFET can be used. Power is supplied by a battery (2 x 9V).
This circuit reinforces signals in a frequency range between 1500 and 2000 Hz for use in...
When a small air current reaches the piezoelectric sensor, a small audio signal is generated and...
This circuit is from a Poptronics, American magazine from August 2000. The circuit can be...