Found in a Popular Electronics from the 90s, this circuit is intended to measure the harmonic distortion of an audio signal. The circuit can be tuned between 970 and 1030 Hz.
The circuit is from Motorola's Linear Databook from 1990, but the configuration is current because...
Found in a 90’s 73 magazine for radio amateurs, this circuit provides a few milliamps of output...
This is another one of the many versions of this circuit that we have in this section. We found it in...