See the last sentence of post 26135. Do you understand the difference between phase delay and transit time?
come on John - you've never trimmed feedback compensation for critical or overdamped response?
the fundamental of Black's insight, usefulness of negative feedback is trading the "excess" open loop gain for things we want - like greater linearity, desensitivity to device operating point gain/phase modulation
the gain/bandwidth, I/O impedance transformations are the basics of negative feedback theory
Last edited:
It's OK.
Feedback theory is not trivial and guys like jcx or Bruno can make my brain hurt.
Not quite all JCX. For as the frequency increases, negative feedback changes phase to the input, and distortion levels rise towards and can actually become positive feedback. Luckily bandwidth is usually limited to prevent any possible oscillation from occurring. "But distortions are usually higher at frequency extremes but within the audio band.
It is also important to understand, as point "A" arrives at the output, and is fedback to the input, "A" becomes "A1" now,,, is not a one time event.
"A1" does not just disappear but again arrives at the output and is again fedback to the input at BetaEo I believe it is called (been decades since I used the terminology), now called "A2". It becomes A3 until so small as to be inconsequential. This continually happens over time. Higher rates of feedback are worse.
Cheers.
Last edited:
So now you telling us that time is not involved when a signal is phase shifted? And the waveform is not changed?
Cheers.
So now you telling us that time is not involved when a signal is phase shifted? And the waveform is not changed?
No, I am telling you that before arguing with poets you have to learn the language. However, you can learn it during such arguments, but I don't think it is effective: not necessary good poets whom you attack are good teachers.
we were very poor when i was in college and i can only drool over this book on the store shelf........a few years ago i was able to download a copy of both RDH3 and RDH4.....it is my audio bible....
we were very poor when i was in college and i can only drool over this book on the store shelf........a few years ago i was able to download a copy of both RDH3 and RDH4.....it is my audio bible....
Nice Tony. Good work.
Cheers.
speaking of mentors...i miss the postings of PRR here....easily the best teacher around when he was here.....
thd and open loop phase shift applied as feedback -
when you look at the slope of the open loop bandwidth and you only use the magnitude shown for calc/sim, the phase shift associated with the slope prevents the reduction of distortion as completely as expected. Thus, on signals, the feedback phase shift can cause distortion of harmonics.
comment/review, pls.
when you look at the slope of the open loop bandwidth and you only use the magnitude shown for calc/sim, the phase shift associated with the slope prevents the reduction of distortion as completely as expected. Thus, on signals, the feedback phase shift can cause distortion of harmonics.
comment/review, pls.
Last edited:
"Bode Maximal Feedback" is a specific recipe – BJ Lurie's online book chapter deals with just that
the flat gain in the "working band" is a consequence of the best management of the phase shift for a given stable response - not at all realted to Otala's concerns
see specifically the “Bode Cutoff” page online in the Classical Feedback book Chapter 4
and Lurie points out how to use much more working band feedback with his Nyquist Stable page
the flat gain in the "working band" is a consequence of the best management of the phase shift for a given stable response - not at all realted to Otala's concerns
see specifically the “Bode Cutoff” page online in the Classical Feedback book Chapter 4
and Lurie points out how to use much more working band feedback with his Nyquist Stable page
- Status
- Not open for further replies.