RC-filter
The drawbacks of pi-filters are the comparatively larger cost, more weight, bigger size and external field developed by the series inductor. However, these drawbacks can be overcome by replacing the series inductor by a series resistor R. Such a circuit is called the R-C filter circuit and is given in figure. By deliberate design R is kept much larger than XC1 at the ripple frequency. So the ripples are dropped across series resistor R instead of across the load resistor RL. Typically R is kept at least 10 times greater than XC2; this means that each section reduces the ripples by a factor of at least 10.
The main drawback of R-C filter is the large voltage drop in the series resistor R i.e. poor voltage regulation. It also needs adequate ventilation to dissipate the heat developed in the resistor R. Thus R-C filter is suitable only for light loads (small load current or large load resistance)
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