This circuit, from the 70's, can be assembled with a more modern FET like the BF245. The circuit is powered by a 9 V battery, as its consumption is very low.
This circuit uses a 7-segment display to indicate the logic level of a test circuit. The power...
With the circuit shown, we have an excellent level for the signal obtained from an electret...
The integrated circuit used in this project is an old voltage comparator, since the configuration was...