This circuit makes use of a low impedance microphone. The relay is according to the supply voltage which can be between 9 and 15 V. The operational gain is approximately 100.
The circuit shown bellow is na áudio amplifier using Darlington transistor in a complementary...
Indicated for automotive use, this circuit was found in a Popular Electronics from the 90s. The...
This TTL circuit was found in an American documentation from the 80s. The components are common in the...