Hello everyone.
I am trying to find out why I cannot use the neg feedback voltage divider on the famous VCVS topology (Ra and Rb from the fig below) to simply control the gain of a bandpass filter?
Using LTSpice, any attempt to change the gain using the above method fails. Results do not meet expectations at all and frequency response gets worse. According to a lot of info sources,
Now what am I missing here? Using the BP filter below, that has a center freq 4.5 kHz, I can control pretty much nothing with Ra and Rb... it just gets worse.
If I set Ra = Rb, I get a unity gain at the filter output. What must I do to get 2x gain? Standard non-inverting op amp negative feedback formulas don't work :/
Thank you in advance,
Simeon
I am trying to find out why I cannot use the neg feedback voltage divider on the famous VCVS topology (Ra and Rb from the fig below) to simply control the gain of a bandpass filter?
Using LTSpice, any attempt to change the gain using the above method fails. Results do not meet expectations at all and frequency response gets worse. According to a lot of info sources,
Code:
"[I]A definite advantage is the ability to precisely set the gain of the filter with resistors Ra and Rb, without upsetting the center frequency.[/I]"Now what am I missing here? Using the BP filter below, that has a center freq 4.5 kHz, I can control pretty much nothing with Ra and Rb... it just gets worse.
If I set Ra = Rb, I get a unity gain at the filter output. What must I do to get 2x gain? Standard non-inverting op amp negative feedback formulas don't work :/
Thank you in advance,
Simeon
