I was using the Analog Devices design Wizzard in order to design a band pass filter with theese characteristics:
Gain : 23 dB
Passband: -3dB at 15 KHz
Stopband: -40dB at 40 KHz
The filter has 4 stages (order 8), the first two stages look like a common Multiple feedback Band-pass Filter, the problem is that the last two stages look diferent:
Does anyone knows what is this topology?, for me looks like a sallen–Key topology for low pass filters, but I was not able to find any reference on Internet about multiple feedback band pass filters that use resitors (R4C R3C and R4D R3D) on the positive input of the operational amplifier.