This filter for receiving audio in telegraphy was found in a magazine 73 for radio amateurs, in an edition of the 80s. The circuit is tuned to 700 Hz and has a 200 Hz bandpass.
The circuit in the figure uses the four current amplifiers of the LM3900 to generate a sawtooth signal...
The presented circuit was suggested by the 1994 Linear Applications Handbook from National...
This circuit was found in a Motorola documentation from 1968. The load current is 10 A. The...