A question for students - if you feed the ac input signal to a leading and lagging all-pass filter in parallel, then use a third op amp as a summing amplifier, what will the output be? And will it be the same for all frequencies within the RC filter range? Try it!
Sorry about that. I had a little technical glitch with that video. It should be up within a week. In the meantime, you can read the section on the adjustable inverter-noninverter in my op amps text. Remember, it's a free download- see link in the video description above.
Thank you for the video. I have a question. Here both filters have a descending phase as frequency increases. That is one filter goes from 0 to -180 and one from 180 to 0. Is it possible to have an ascending phase all-pass filter? (e.g a filter that goes from -180 to 0)
If I understand you correctly, you're asking for the same sort of circuit but with a positive slope, right? I am not sure that you could make one as simple as this little first order circuit. I'd have to think about that for a bit. I can't recall seeing one.
@@ElectronicswithProfessorFiore Yes, exactly. I'm looking for such allpass filter because I want to cancel out the phase shift caused by a preceding highpass filter. If possible then we can get a hp filter with flat phase response. But maybe such allpass filter is impossible in principle?
@@siarez It sounds like what you want is constant group delay or linear phase for your filter. In that case, I'd suggest looking at standard active filters using a Bessel alignment instead of the usual Butterworth (check the videos in the Op Amps playlist or chapter 11 of my free op amps text). A 2nd order Sallen & Key wouldn't be much more complicated than the circuit in the video above (as in another cap and maybe another resistor).
Yeah, it's just a matter of perspective. When most people think of filters, they think in terms of the amplitude (magnitude) response, so calling these "all -pass" makes a certain amount of sense. Of course, forgetting that filters also have a phase response can result in no end of difficulties...
@ElectronicswithProfessorFiore thanks for the reply. I'm just kind of stumble bumbling my way around, trying to satisfy my curiosity about different types of filters. I am approaching this from a perspective of "I'm curious and want to learn more about this synthesizer component" There sure does seem to be a bounty of learning videos on this tube.
Your students are really lucky, you're a fantastic professor!
Fascinating. I wish I could articulate the questions I have. I think I'll wait until we've journeyed a little further. Thanks again.
thanks professor fiore!
A question for students - if you feed the ac input signal to a leading and lagging all-pass filter in parallel, then use a third op amp as a summing amplifier, what will the output be? And will it be the same for all frequencies within the RC filter range? Try it!
So r3 and c1 determine the phase shift, for 120 deg at 100khz what would be the values? Thank you.
Can you please provide a link to the previous video that you mentioned.
Sorry about that. I had a little technical glitch with that video. It should be up within a week. In the meantime, you can read the section on the adjustable inverter-noninverter in my op amps text. Remember, it's a free download- see link in the video description above.
Thank you for the video. I have a question. Here both filters have a descending phase as frequency increases. That is one filter goes from 0 to -180 and one from 180 to 0. Is it possible to have an ascending phase all-pass filter? (e.g a filter that goes from -180 to 0)
If I understand you correctly, you're asking for the same sort of circuit but with a positive slope, right? I am not sure that you could make one as simple as this little first order circuit. I'd have to think about that for a bit. I can't recall seeing one.
@@ElectronicswithProfessorFiore Yes, exactly. I'm looking for such allpass filter because I want to cancel out the phase shift caused by a preceding highpass filter. If possible then we can get a hp filter with flat phase response. But maybe such allpass filter is impossible in principle?
@@siarez It sounds like what you want is constant group delay or linear phase for your filter. In that case, I'd suggest looking at standard active filters using a Bessel alignment instead of the usual Butterworth (check the videos in the Op Amps playlist or chapter 11 of my free op amps text). A 2nd order Sallen & Key wouldn't be much more complicated than the circuit in the video above (as in another cap and maybe another resistor).
What is the name of this software
TINA-TI, the free version of TINA available from ti.com
Maaaan, I wish they were just called phase shifters. That would make it easier to understand from the get go.
Yeah, it's just a matter of perspective. When most people think of filters, they think in terms of the amplitude (magnitude) response, so calling these "all -pass" makes a certain amount of sense. Of course, forgetting that filters also have a phase response can result in no end of difficulties...
@ElectronicswithProfessorFiore thanks for the reply. I'm just kind of stumble bumbling my way around, trying to satisfy my curiosity about different types of filters. I am approaching this from a perspective of "I'm curious and want to learn more about this synthesizer component" There sure does seem to be a bounty of learning videos on this tube.
@@CatFish107 True, but some of them are questionable because nothing is curated by "the algorithm" in terms of accuracy, so be careful.