# Band Stop Filter Calculator

The band stop filter is a type of filter circuit that is used to attenuate frequencies above and below a designated band of frequencies called a stopband.

This page contains a series of calculators to aid in the design of band stop filter circuits.

A band stop filter consists of a high pass filter and low pass filter connected together in parallel.

They contain four basic components that are used to determine the stopband: two resistors R1 and R2, and two capacitors C1 and C2.

### Band Stop Filter Circuit

Band stop filters attenuate a stopband that is determined by two characteristic frequencies: the low cut-off frequency FL and the high cut-off frequency FH. This is similar to a band pass filter, and is essentially exactly the opposite. These characteristic frequencies are determined by the values of the components used.

The components of the low-pass filter stage, C1 and R1, determine the value of the low cut-off frequency FL.

The components of the high-pass filter stage, C2 and R2, determine the value of the high cut-off frequency FH.

It features calculators for the characteristic cut-off frequencies, values of the capacitors and resistors, and a resonant frequency calculator.

## Band Stop Filter Cut-Off Frequency Calculator

The band stop filter cut-off frequency calculator can be used to calculate the cut-off frequencies of the filter. Two inputs are required for each cut-off frequency.

Calculation of the low cut-off frequency FL requires (1) the resistance of R1, and (2) the capacitance of C1.

Calculation of the high cut-off frequency FH requires (1) the resistance of R2, and (2) the capacitance of C2.

Based on these values, the calculator will provide the cut-off frequency as well as the resonant frequency of the filter.

The following equations determine FL and FH in the band stop filter:

f_L = \frac{1}{2 \pi R_1 C_1}
f_H = \frac{1}{2 \pi R_2 C_2}

## Band Stop Filter Capacitor Selection Calculator

The band stop filter capacitor calculator can be used to calculate the values of capacitors needed to create a filter with a specific cut-off frequencies FL and FH.

Calculation of each capacitor value requires two inputs. C1 requires the low cut-off frequency FL and the resistance of R1. C2 requires the high cut-off frequency FH and the resistance of R2.

The following equations determine C1 and C2 in the band-stop filter:

C_1 = \frac{1}{2 \pi R_1 F_L}
C_2 = \frac{1}{2 \pi R_2 F_H}

## Band Stop Filter Resistor Selection Calculator

The band stop filter resistor calculator can be used to calculate the values of resistors needed to create a filter with a specific cut-off frequencies FL and FH.

Calculation of each resistor value requires two inputs. R1 requires the low cut-off frequency FL and the capacitance of C1. R2 requires the high cut-off frequency FH and the capacitance of C2.

The following equations determine R1 and R2 in the band-stop filter:

R_1 = \frac{1}{2 \pi C_1 F_L}
R_2 = \frac{1}{2 \pi C_2 F_H}

## Band Stop Filter Resonant Frequency Calculator

The band stop filter resonant frequency calculator can be used to determine the resonant, or center, frequency of a filter with cut-off frequencies FL and FH.

Calculation of the resonant frequencies requires both the low cut-off frequency FL and high cut-off frequency FH.

If these calculators didn’t help, check out our other calculators for electronics or our comprehensive tutorials!