This circuit was found in a publication by Edelman from 1924. The power comes from the battery and the listening is through a high-impedance headphone.
This circuit is from the 80's, using an integrated of the time. The circuit serves as a reference,...
This circuit was obtained from an American 80's documentation. The operational ones can be...
This logarithmic gain operating configuration was found in the June 1994 Electronics Now magazine. The...