The band pass filter is a type of filter circuit that is used to attenuate frequencies **above and below a designated band of frequencies called a passband**.

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

The band pass filter consists of a high pass filter and low pass filter *cascaded *in series.

Band pass filters contain four basic components that are used to determine the passband.

### Band Pass Filter Circuit

Band pass filters output a passband that is determined by two characteristic frequencies: the **low cut-off frequency F _{L}** and the

**high cut-off frequency F**. These frequencies are determined by the values of the components used.

_{H}The components of the high-pass filter stage, C_{1} and R_{1}, determine the value of the low cut-off frequency F_{L}.

The components of the low-pass filter stage, C_{2} and R_{2}, determine the value of the high cut-off frequency F_{H}.

This page contains a series of calculators to help you design and understand the band pass filter circuit.

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

## Band Pass Filter Cut-Off Frequency Calculator

The band pass 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 F_{L} requires (1) the resistance of R_{1}, and (2) the capacitance of C_{1}. Calculation of the high cut-off frequency F_{H} requires (1) the resistance of R_{2}, and (2) the capacitance of C_{2}. 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 F_{L} and F_{H} in the band-pass filter:

f_L = \frac{1}{2 \pi R_1 C_1}

f_H = \frac{1}{2 \pi R_2 C_2}

## Band Pass Filter Capacitor Selection Calculator

The band pass filter capacitor calculator can be used to calculate the values of capacitors needed to create a filter with a specific cut-off frequencies F_{L} and F_{H}.

Calculation of each capacitor value requires two inputs. C_{1} requires the low cut-off frequency F_{L} and the resistance of R_{1}. C_{2} requires the high cut-off frequency F_{H} and the resistance of R_{2}.

The following equations determine C_{1} and C_{2} in the band-pass filter:

C_1 = \frac{1}{2 \pi R_1 F_L}

C_2 = \frac{1}{2 \pi R_2 F_H}

## Band Pass Filter Resistor Selection Calculator

The band pass filter resistor calculator can be used to calculate the values of resistors needed to create a filter with a specific cut-off frequencies F_{L} and F_{H}.

Calculation of each resistor value requires two inputs. R_{1} requires the low cut-off frequency F_{L} and the capacitance of C_{1}. R_{2} requires the high cut-off frequency F_{H} and the capacitance of C_{2}.

The following equations determine R_{1} and R_{2} in the band-pass filter:

R_1 = \frac{1}{2 \pi C_1 F_L}

R_2 = \frac{1}{2 \pi C_2 F_H}

## Band Pass Filter Resonant Frequency Calculator

The band pass filter resonant frequency calculator can be used to determine the resonant, or center, frequency of a filter with cut-off frequencies F_{L} and F_{H}.

Calculation of the resonant frequencies requires both the low cut-off frequency F_{L} and high cut-off frequency F_{H}.

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