Band Pass Filter

What is a Band Pass Filter?

A band-pass filter is a device that allows certain frequency bands to pass while blocking other frequency bands. For example, the RLC oscillator circuit is an analog bandpass filter.

A bandpass filter is a device that allows certain frequency bands to pass while blocking other frequency bands. For example, the RLC oscillator circuit is an analog bandpass filter. An ideal bandpass filter should have a completely flat passband, with no amplification or attenuation inside the passband, and all frequencies outside the passband are completely attenuated. Additionally, conversions outside the passband are performed over a very small frequency range.

Definition of bandpass filter
A band-pass filter refers to a filter that can pass frequency components in a certain frequency range, but attenuates frequency components in other ranges to a very low level, as opposed to the concept of a band-stop filter. An example of an analog bandpass filter is a resistor-inductor-capacitor circuit (RLC circuit). These filters can also be produced by combining low-pass filters with high-pass filters.

Applications of Bandpass Filters
Spectrum analyzers of many audio devices use this circuit as a bandpass filter to select signals in different frequency bands. On the display, the number of light-emitting diodes is used to indicate the magnitude of the signal amplitude. The center frequency of this active bandpass filter, the voltage gain at the center frequency fo is Ao=B3/2B1;
Quality factor, 3dB bandwidth B=1/(п*R3*C) can also calculate the parameter values of each component of the bandpass filter according to the Q, fo, and Ao values determined by the design. R1=Q/(2пfo AoC), R2=Q/[(2Q2-Ao)*2пfoC], R3=2Q/(2пfoC). In the above formula, when fo=1KHz, C takes 0.01Uf. This circuit can also be used for general frequency selective amplification. Active Bandpass Filter Circuit
This circuit can also use a single power supply, just bias the positive input of the op amp at 1/2V+ and connect the lower end of resistor R2 to the positive input of the op amp.