Suitable for operation with high impedance microphones, this circuit was found in American documentation from the 90s. The transistor can be any general-purpose type.
This circuit is from a 1987 American publication called Electronics Handbook. The circuit can be...
We found this circuit in the March 1992 issue of Radio Electronics magazine. The circuit uses an...
When the input voltage is higher than 2/3 of the power supply voltage the green LEDs glows. When...