This circuit was found in a 90s Popular Electronics. The sensors can be common speakers that reach from 15k to 25 kHz, such as piezoelectric tweeters.
The JFETs of this old circuit admit modern equivalents and their characteristics determine the maximum...
This low power audio amplifier was found at 1992s Popular Electronics. Transistors are general...
This circuit transmits in the FM band. It is a good range FM transmitter found in a 90's Silicon...