Calculate Bandpass Active Filters
 The Butterworth filter
The Butterworth filter is a type of signal processing filter designed to have as
flat a frequency response as possible in the passband.
It is also referred to as a maximally flat magnitude filter.
 The Chebyshev filters
The Chebyshev filters are analog or digital filters having a steeper rolloff and
more passband ripple (type I) or stopband ripple (type II) than Butterworth filters.
Chebyshev filters have the property that they minimize the error between the
idealized and the actual filter characteristic over the range of the filter, but
with ripples in the passband.
This type of filter is named in honor of Pafnuty Chebyshev because its mathematical
characteristics are derived from Chebyshev polynomials.
Because of the passband ripple inherent in Chebyshev filters, the ones that have a
smoother response in the passband but a more irregular response in the stopband are
preferred for some applications.
 The Bessel filter
In electronics and signal processing, a Bessel filter is a type of linear filter
with a maximally flat group delay (maximally linear phase response). Bessel filters
are often used in audio crossover systems. Analog Bessel filters are characterized
by almost constant group delay across the entire passband, thus preserving the wave
shape of filtered signals in the passband.

 Q factor
The Q Factor is a measure of how "Selective" or "Unselective" the band pass filter
is towards a given spread of frequencies. The lower the value of the Q factor the
wider is the bandwidth of the filter and consequently the higher the Q factor the
narrower and more "selective" is the filter.

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Narrow 2 Pole Bandpass Active Filter (Bessel)
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