Summary 3-117 till 3-120FiltersA rectifier is an electrical device that rectify AC voltage to DC voltage. There are many type rectifier like full- wave rectifier, half- wave rectifier, bridge type rectifier and three- Phase rectifier. The output voltage of those rectifier are pulsating DC voltage. to make this pulsating output voltage more constant and useful they use filters.Capacitor- input filtersThe capacitor- input filter is a capacitor that is installed parallel with the lood so it can discharge on the lood. The capacitor charge when the pulsating output voltage of the rectifier rise from zero to peek and discharge when the voltage begin to drop to zero. The capacitor input filter work the same on full wave as on a half wave rectifier.choke- input filter A choke is a device when it is connected in series with the load it opposed any change in the load current. They use that characteristic of the choke to smooth out the DC so it remains at a constant value.PI filtersThe pi filter is that combine capacitor and choke. With this arrangement you get a better and smoother DC output.Amplifiers Amplifiers are devices that amplify a frequency from small to large. To do this they use a transistor.