Active filters

Main use of filters is in analog to digital converters where low level signals picks up unwanted noises. These noises are then added to transducer output making results awkward in nature. Filters suppress the carrier component of a phase sensitive detector output and permits some phase. Filter are generally of four types-low pass filter, high pass filter, band pass filter and band reject filter. Examples for the low pass filters are butterworth filter, tchebychev filter, elliptical filter and bassel filter. There is no ripple in the pass band of butterworth filter and thus they have monotonically increasing attenuation. Tchebychev filter is characterized by ripple in the pass band.