The Pulse-width modulation (PWM) circuit in figure1 it works by making a square wave with a variable on-to-off ratio, the average on time may be varied from 0 to 100 percent. The IC 555 are main of this circuit which making a square wave with a variable on-to-off ratio, In put Frequency of cuitcuit we fix at 1 KHz
Pulse-width modulation : PWM 
