Audio VU Meter by LM324
This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324. It is a popular IC and should be available from many parts stores.
Read more : Audio VU Meter by LM324
Other Link
LM324 PWM Control Motor Speed
Park-Aid with IC LM324,555,7812
LED Voltmeter for car battery by LM324
