(On the other hand, this is not beneficial in terms of cost as there are more parts involved.) This property offers the following benefits in suppressing noise. 8 LC filter configuration and frequency characteristics (4) Benefits of using LC filtersĪs shown above, filters with higher orders have steeper frequency characteristic slopes. If the capacitor and inductor constants are not set appropriately according to the impedance of the surrounding circuit, the frequency characteristics will not slope so steeply.įig. Note that the characteristics shown in Fig. Doing so merely increases the capacitor and inductor constants.

If two capacitors or inductors are combined together, the order of the filter will not increase. When combining parts, inductors and capacitors are alternated. (3) Alternate capacitors and inductors when combining them Filters with higher orders have steeper frequency characteristics. An L-type filter is a second order filter, while a π-type or T-type filter is a third order filter. The number of parts in a filter is referred to as the 'order' of the filter. Doing so can help to improve the filter's ability to pick out signals and noise (Fig. The slope of the frequency characteristics can be increased by 20dB by adding another part to the combination. (2) Each part increases the slope 20dB/dec. A π-type or T-type filter formed from a total of three parts will have a slope of 60dB/dec. If a single capacitor or inductor is used, the frequency characteristics will have a slope of 20dB/dec.Īn L-type filter, in which a single capacitor and single inductor are combined, will have a slope of 40dB/dec. 8 shows the basic characteristics of some LC filters that combine capacitors and inductors.

Filters that combine capacitors and inductors (1) LC filtersĬapacitors and inductors can be combined to improve frequency characteristics.

Clc pi filter design