We found this configuration in a 70s American documentation. The circuit makes use of operational amplifiers of the time. Modern equivalents can be tested.
This ultra-simple circuit need a carbon microphone to operate. The circuit must be powered from D...
This logarithmic operational amplifier was found in the September 1994 issue of Electronics Now...
This circuit was found in an American 1980s documentation. It makes use of an unusual MOSFET today...