Using operational amplifiers of the time, we found this circuit in documentation from the 90s. The configuration can be adapted to use modern operational amplifiers.
This circuit matches a source of high or medium impedance audio signals with a low impedance...
Found in a 1993 Electronics Hobbyst Handbook, this circuit uses components that are still common...
This pulse width-tuned circuit was found in the March 1996 issue of Electronics Now magazine. The...