Sallen and Key Filter Networks with Amplifier Gain Larger than or Equal to Unity
G.S. Moschytz · IEEE Journal of Solid-State Circuits · 1967
Noninverting operational amplifiers cannot readily be used for various Sallen and Key filters because they cannot provide gain less than unity. A simple network modification is suggested that overcomes this limitation and introduces an added degree of freedom with parameters that are determined by passive components only.