Found in Exar documentation from the 1980s, this circuit has a 60 dB cutoff at 1800 Hz. The circuit can be adapted to operate at other frequencies.
This setting appears multiple times on the site from different sources. This is from a 2000 manual...
This power supply was found in a RCA publication from the 1970s. The circuit uses transistors from that...
This circuit was obtained in a documentation about old neon lamps. The circuit indicates when a...