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PHASE SHIFT IN AN AMPLIFIER
- Thread starter 66OLEG
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Hi.
My circuit is suppose to produce 4 output sinusoidal signals with different (and switchable) amplitudes. It should be out of phase with Vref = 400 Hz sinus which I use as Vin for the first stage differential amp. The signal is then split into four branches with different gains.
The three inverting stage amp. gives me Vout= -A*Vin.
Seems to me it’s impossible to correct the propagation delay so I call it “phase shift” –for periodic signals it’s OK.
Will appreciate your advice.
Thank you.
My circuit is suppose to produce 4 output sinusoidal signals with different (and switchable) amplitudes. It should be out of phase with Vref = 400 Hz sinus which I use as Vin for the first stage differential amp. The signal is then split into four branches with different gains.
The three inverting stage amp. gives me Vout= -A*Vin.
Seems to me it’s impossible to correct the propagation delay so I call it “phase shift” –for periodic signals it’s OK.
Will appreciate your advice.
Thank you.
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- #5
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- #7
To Irstuff.
As an Aerospace dude
your probably familiar with Arinc565. My outputs are an altitude syncros and the Vref is an aircraft 400 Hz power line which NOBODY let me
delay.
And that new Ref should rather precede the outputs isn’t it?
Thank you.
As an Aerospace dude
your probably familiar with Arinc565. My outputs are an altitude syncros and the Vref is an aircraft 400 Hz power line which NOBODY let me delay.
And that new Ref should rather precede the outputs isn’t it?
Thank you.
I'm not sure I'm following. Your copy of the 400Hz reference is already delayed from the main line in any case, even if it's only 10 microsec or so.
Additionally, isn't the purpose of the 400Hz reference to use it for demodulating the synchro output? So there shouldn't be any issue with a phase lag between it and the main supply. The synchro to digital converter only uses the synchro outputs and the reference for demodulating the output. Therefore, the relative phase between the reference and syncho output is what counts, so if the reference is appropriately delayed to match phase with the outputs, there should be no problem.
TTFN
Additionally, isn't the purpose of the 400Hz reference to use it for demodulating the synchro output? So there shouldn't be any issue with a phase lag between it and the main supply. The synchro to digital converter only uses the synchro outputs and the reference for demodulating the output. Therefore, the relative phase between the reference and syncho output is what counts, so if the reference is appropriately delayed to match phase with the outputs, there should be no problem.
TTFN
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- #9
To Irstuff.
You are right –it’s the relative phase between Vref and outputs what counts.
And so was my initial question: how to shift sinusoidal signal with minimum hardware? It has to be moved to ~10° “left” (if you look on scope) or ~350° to the “right”.
Latter is less realistic-it’s almost 2.4mS. I recall some articles where negative feedback was used to compensate a phase shift on the output isolation trans but have no details.
Thank you.
You are right –it’s the relative phase between Vref and outputs what counts.
And so was my initial question: how to shift sinusoidal signal with minimum hardware? It has to be moved to ~10° “left” (if you look on scope) or ~350° to the “right”.
Latter is less realistic-it’s almost 2.4mS. I recall some articles where negative feedback was used to compensate a phase shift on the output isolation trans but have no details.
Thank you.
Hi,
From your description, and the phase shift observed, your three-stage amplifier must be ac-coupled between stages. These R-C couplings will give less than 2 x 90 deg phase shift hence the 10deg lag. You may get close to 0 deg shift if you can make the capacitors much larger - how close do you need it to be?
Alternatively, for a 10 deg phase difference have you considered a phase-advance C-R circuit at the input of the amplifier? You will need to adjust the overall gain a little, to compensate for the C-R network, but it's a lot easier than using tailored feedback around the whole amplifier.
Using negative feedback in the way you suggest is possible but very complex. Without doing a Nyquist plot of the complete setup you are liable to make the whole thing unstable and turn it into an oscillator at some other frequency.
From your description, and the phase shift observed, your three-stage amplifier must be ac-coupled between stages. These R-C couplings will give less than 2 x 90 deg phase shift hence the 10deg lag. You may get close to 0 deg shift if you can make the capacitors much larger - how close do you need it to be?
Alternatively, for a 10 deg phase difference have you considered a phase-advance C-R circuit at the input of the amplifier? You will need to adjust the overall gain a little, to compensate for the C-R network, but it's a lot easier than using tailored feedback around the whole amplifier.
Using negative feedback in the way you suggest is possible but very complex. Without doing a Nyquist plot of the complete setup you are liable to make the whole thing unstable and turn it into an oscillator at some other frequency.
cbarn24050
Industrial
Hi, the phase shift is due to the low pass filter effect of the amplifier. If you increase the bandwidth then the phase shift will reduce. At 400Hz it should be very easy to get the shift down to an allmost unmeasureable amount.
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