`alpha = ( R_1 + R_2 ) / (2 * C_1 * R_1 * R_2 )`

Enter a value for all fields

The Attenuation α - Sallen-Key Filter calculator computes the filter based on two resistance measurements and the the capacitance.

INSTRUCTIONS: Choose units and enter the following:

• (R₁) This is the first resistance (see diagram)
• (R₂) This is the second resistance (see diagram)
• (C₁) This is the capacitance

Attenuation Sallen-Key Filter (α): The calculator returns the filter value in hertz.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

The formula for the alpha Sallen-Key Filter is:

   α= (R1+R2)/(2⋅C1⋅R1⋅R2)

where:

• α is the alpha Sallen-Key filter in units of frequency (e.g. hertz)
• R1 is the first resistance (see diagram)
• R2 is the second resistance (see diagram)
• C1 is the capacitance

This equation computes the attenuation factor of the unity gain low pass filter implementation of the Sallen-Key topology.  This electronic filter is a special case of a second-order unity gain filter version of the voltage-controlled voltage-source (VCVS) topology.

The attenuation factor `alpha` is given as a function of the Resistances (`R_1, R_2`) and the Capacitance (`C_1`) shown in the diagram.

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Sallen-Key Calculators:

• Sallen-Key α filter 
• Sallen-Key Q Factor (ω₀ ,α) 
• Sallen-Key Q Factor (R&C) 
• Sallen-Key Unity Gain Low Pass Filter - Transfer Function
• Sallen-Key Unity Gain Low Pass Filter - Transfer Function (f0)
• Sallen-Key Unity Gain Low Pass Filter - Transfer Function (R&C)