This high impedance amplifier is from 1985 documentation by General Electronic. The amplifier with FET at the entrance is from the period and the source is 9 V.
Charcoal microphones are rare today. In the figure we have a circuit that shows the use of one of...
This circuit causes one LED to light up if the voltage falls below the value set in R3 and the...
Found in a 90’s Electronic Design, this circuit generates stable signals in frequency given by the...