LED VU meter using transistor is analog circuit to show level of power audio signal. You can build 5 LED to 20 LED display with PCB.
Simple circuit that you may need it. learn more!
See and try building Lie detector circuit. The resistance of human skin using transistors and LED displays is small and easy application.
It is Very simple amplifier circuit using transistor 2N3904 only, low noise than normal IC circuits, low distortion,frequency response: 20 Hz to 20 kHz.
Two circuits of Hifi transistor headphone amplifier!