Gain Allocation for Sallen and Key Biquads

Especially talking about the Sallen and Key Biquads or Circuitry, the flexibility of allocating different gains to different filter sections gives an extra degree of freedom in designing high order filters. This freedom of allocating different gains to different factors is termed as gain allocation, or gain assignment. However, there are no such decisive rules, this flexibility offers an opportunity to improve the overall design.

The different gain allocation at different section would affect the signal strength in each section. Hence, gain allocation can be used to make the maximum and minimum signal strength in the pass band in all sections as uniform as practical. This means the overall gain is shared without making the signal in one particular section either too strong to cause distortion or op amp latching, or too weak that falls below the noise threshold.

This gain allocation- gain compensation and enhancement can be performed for Sallen Key representation of Butterworth filter and similar circuitry. Compensation is done at the early stages where as the enhancement is done at the later stages. The purpose of compensation to do is in the order to avoid clipping.

More interesting topics for Active and Passive Filter Design and other discussions refer to

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