Hi guys,
I am trying to build a state-variable audio filter and it simply just doesnt work as it should, by changing R3 and R4 it suppose to change the cut off frequency but I've simulated and built it on the breadboard they both seems to get the same result.
Bandpass don't appears to work as bandpass and highpass don't work as highpass, well hipass actually have the same response as bandpass :?
Something is just not right and I do not know what it is, can somebody help me!!!
Well, that's what it appears to be on the book Active-Filter Cookbook I have and also here on maxim-ic's **broken link removed**
I don't understand how IC1 can be a hi pass filter when it is just an non-inverting op amp configuration, I am currently very lost on this right now......
This is how I remember this setup. The first stage is somewhat different to yours. (Ignore my values as I just used the program's default drawing values)
It works in SwitcherCAD III. See below.
Edit:
Oops! I didn't notice that R12 (R5 in my schematic) is 20k. I tried that - it changes the response slightly, but still works. The One's configuration gives the same amplitude curves, but with different phase relationships.
I am just trying to find out if Orcad Pspice student version is not able to simulate correctly or it's something that I am not doing right .......... Can someone that uses Orcad student version confirm this?