I am somewhat confused regarding the MFB filter naming custom. In the literature, I read of the Deliyannis form, the Deliyannis-Friend form, the Rauch form, and people seemingly confuse them.
There are essentially 3 circuits (assuming a bandpass for the sake of discussion):
- The simplest has 2 capacitors and 2 resistors
- This can be augmented with a third resistor that is used to divide down the input signal
- The most complex form adds a resistive divider for positive feedback to the noninverting input (often called "Q enhancement")
So, which one is which? If you know, please provide the bibliography, too.
It also crossed my mind that it might have something to do with capacitor choice, too. Both capacitors are usually chosen to have equal capacitance, "for convenience". Are there different names for the circuit with equal and nonequal capacitor values?