The following is online calculator for Sallen-Key 2nd Order Unity Gain Low Pass Filter Design. In Sallen-Key 2nd Order Unity Gain LPF Design the two resistors are chosen equal. The two capacitors are unequal. The capacitor sets the Q of the filter. The passband voltage gain is unity(Av=1). Sallen key filters are VCVS filters because the op-amp is used as voltage controlled voltage source. With VCVS filters Butterworth, Chebyshev, and Bessel filters can be implemented.
Notes on Sallen-Key 2nd Order Unity Gain LPF Design Calculator
The voltage gain of this filter is unity.
(
A_v=1
)
The Q of the filter is given by,
(
Q=0.5sqrt{frac{C_2}{C_1}} )
The pole frequency is given by,
(
f_p = frac{1}{2 pi R sqrt{C_1 C_2}}
)
The cutoff frequency is given by,
(
\ f_c = K_c f_p
)
For Butterworth filter;
Q=0.707 and Kc=1
For Bessel filter;
Q=0.577 and Kc=0.786
For best result select the capacitors value in the range 0.001uF and 0.1uF.
