RLC Notch Filter

As the name suggests RLC, this notch filter or bandstop filter contains passive elements resistor, inductor, and capacitor. Therefore, it is also known as a passive notch filter. The circuit diagram of the RLC notch filter is shown in the below figure.

RLC Notch Filter Circuit

The shunt element of an RLC notch filter is a series combination of L and C. The output is taken across this series combination of inductor and capacitor. The equivalent circuit and characteristics of the RLC notch filter are shown in the figure below.

RLC Notch Filter Equivalent Circuit

Here, the equivalent impedance of a series combination of the L and C is given by,

Now, the net impedance of the circuit is given by,

Now, applying KVL (Kirchhoff’s Voltage Law) in loop a-b-c-d to the equivalent circuit of RLC notch filter, we get,

Now, at the series resonance condition, the resonant frequency is given by

And the Q-factor is given by,

Where, = Bandwidth =

while, Hz is the lowest cut-off frequency, and Hz is the highest cut-off frequency. The characteristics of the notch filter is shown in the figure below.

Notch Filter Characteristics of a Notch Filter

RLC type Notch Filter can also be made by utilizing the circuit that is shown in the figure below.

RLC Notch Filter Circuit

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