Second Order LC Low Pass Filter Calculator

byee-diary • • 2 min read
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Calculate resonant frequency(fr)
Inputs:




Theoretical Results:



Second Order LC filter Circuit Diagram
Calculate L:
Inputs:



Theoretical Results:
Formula Used:
\( L =\frac{1}{4 \pi^2 f_{r}^2 C}\)
Calculate C:
Inputs:



Theoretical Results:

Formula Used:
\( C =\frac{1}{4 \pi^2 f_{r}^2 L}\)

About LC Parallel Resonant Circuit Calculator

The above online calculator for second order LC low pass filter calculates the cutoff frequency and Q from given inductor, capacitor and load resistor values or calculate inductor, capacitor values from given cutoff frequency.

Notes on Second Order LC Low Pass Filter Calculator

The Q of the filter is given by,\[Q=\frac{R}{X_L}\]where, the inductor reactance \(X_L\) is calculated at the resonant frequency. When Q is high the gain will increase and in frequency response graph we will see peak. The following graph illustrates frequency response of LPF when Q is high.

frequency response of LPF at high Q
To get maximally flat response(Butterworth Response), Q should be 0.707 and at this Q=0.707 value the frequency response of the LC low pass filter will be like the following,
maximally flat frequency response of LPF
Higher order LC LPF

The quality factor Q of the LC parallel tank is given by the following equation:

\(Q=\frac{Energy \space  stored \space in \space Reactive \space component}{Energy \space dissipated}\) 

or, \(Q=\frac{X_C}{R_w}=\frac{X_L}{R_w}\)

Some example usage of this online LC parallel resonant circuit calculator are as follows.

- How does Single Diode Modulator Circuit work?
- Simple Amplitude Modulation (AM) circuit using Single Diode Modulator
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