Filter Circuits – Active Filters

jojo May 5, 2014 10 Comments
Introduction to Filters An electric filter is a network designed to attenuate certain frequencies but pass others without attenuation. A filter circuit, therefore, possesses at least one pass band — a band of frequencies in which the output is approximately equal to the input (that is, attenuation is zero) and an attenuation band in which output is zero (that is, attenuation is infinite). The frequencies that separate the different pass and attenuation bands are called the cut-off frequencies. Filters...

Series Inductor Filter

jojo June 17, 2014 4 Comments
Series Inductor Filter.       In this arrange­ment a high value inductor or choke L is connected in series with the rectifier element and the load, as illustrated in figure. The filtering action of an inductor filter de­pends upon its property of opposing any change in the current flowing through it. When the output current of the rectifier increases above a certain value, energy is stored in it in the form of magnetic field and this energy is...

RC filters-operation-circuit-diagram

jojo June 17, 2014 No Comments
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...

Choke input-L section filter

jojo June 17, 2014 1 Comment
A simple series inductor reduces both the peakand effective values of the output current and output voltage. On the other hand a simple shunt capacitor filter reduces the ripple voltage but increases the diode current. The diode may get damaged due to large current and at the same time it causes greater heating of supply transformer resulting in reduced efficiency. In an inductor filter, ripple factor increases with the increase in load resistance RL while in a capacitor filter...