This optical theremin was found in a 90s Hands-On Electronics. The basic frequency is given by C1 and the output is made in a speaker through a small output transformer.
This circuit is from a Linear Technology integrated circuit manual from the 1990s. The circuit...
The IC used in this project is not common these days, but if you have one you can build a high...
With this circuit, it is possible to excite a white LED or another type of high brightness with...