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(A_{v}=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

**Voltage Gain**

**Quality Factor(**Q)

**Pole Frequency**

The pole frequency is given by,

\( f_p = \frac{1}{2 \pi R \sqrt{C_1 C_2}} \)

**Cuttoff Frequency**

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

**Capacitor Values**

**Rolloff**

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What does Kc represent?