Found in an English publication in 1969, this circuit has a 600 kHz pass band. Ferranti's transistors support modern equivalents.
This circuit was found in a 1975 filter cookbook. The operational may be others, but they should...
We found this touch control on a Popular Electronics from 1970. The circuit makes use of an...
This circuit was obtained from an American documentation from 1976. The circuit can be adapted to...