(3) If Vin2 = Vin3 = 0, a second-order high-pass filter can be obtained with
V1 /Vin1 and a second-order band-pass filter can be obtained with V2 /Vin1.
(4) If Vin2 = 0 and Vin1 = Vin3 = Vin, a second-order notch filter can be obtained
with V1 /Vin.
(5) If Vin1 = Vin2 = Vin3 = Vin and R1 = R2, a second-order all-pass filter can be
obtained with V1 /Vin.