Sallen and Key Filter 14.4

Unity Gain Sallen and Key Filter

SK Filter with Gain more than 1

R1=R2, C1=C2

Sensitivity of ω n

Sensitivity of Q

R2/R1=1, C2/C1=1, K=1 Q Q↑→Increased sensitivity to component variations

Q=2, C2/C1=1, R2/R1=1 K K↑→Increased sensitivity of Q to K increases

Q=2, C2/C1=1, K=2 R2/R

Q=2, R2/R1=1, K=2 C2/C

Summary SK filter shows more sensitivity to component variation as Q increases Low R2/R1 & C2/C1 leads to less sensitivy due to R1, R2, C1 and C2, but more sensitivity to K.