Symmetric circuit (or not) then to a more difficult question
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andy2
diyAudio Member

Join Date: Nov 2004
Location: StupidVille
Symmetric circuit (or not) then to a more difficult question

Quote:
 Let us go then, you and I ... Oh, do not ask, “What is it?” Let us go and make our visit.
I attached two circuits below. Which one would be symmetric and which one is not? Symmetric I mean if I connect the sine wave source one end, then measure the output on the other end, then swap end in term of source and output, would the output be different? Notice exercise only applies to pure sine wave.

Here are the options:

1. Both are symmetric
2. Both are non-symmetric
3. Only circuit 1 is symmetric
4. Only circuit 2 is symmetric
Attached Images
 circuit.png (7.4 KB, 129 views)

Last edited by andy2; 12th July 2019 at 07:24 PM.

andy2
diyAudio Member

Join Date: Nov 2004
Location: StupidVille
I have two more circuits. Again which is symmetric and which is not?

Possible options:

1. Both are symmetric
2. Both are non-symmetric
3. Circuit 1 is symmetric (which is pretty obvious since R1 = R1)
4. Circuit 2 is symmetric (probably not)
Attached Images
 circuit2.png (8.9 KB, 129 views)

 12th July 2019, 08:04 PM #3 nigelwright7557   diyAudio Member     Join Date: Apr 2008 Location: Carlisle, England If you get the same out on each phase of the signal then they are symmetric. In your first post neither are symmetric. In the second post both are symmetric. __________________ PCBCAD51 download or CDROM October 2019 version out now ..https://www.murtonpikesystems.co.uk
 12th July 2019, 08:17 PM #4 andy2   diyAudio Member   Join Date: Nov 2004 Location: StupidVille OK, so because of the diode in the first post, it is not symmetric? Also, is it true that if all components are passive (R, L, C), then all circuits are symmetric (I guess this would only be true if the source is pure sine wave, although it's hard for me to agree).
andy2
diyAudio Member

Join Date: Nov 2004
Location: StupidVille
So the next thing is I am going to place these circuits in my post #1 and post #2 into a conductive three dimensional structure, let's call it a metal structure, what would happen? Would the signal from left to right, right to left be symmetric?

See my drawing below. OK, I am using a crappy Paint program so hopefully I can rely on your imagination.

Please also keep in mind that the metal structure is a 3-dimensional structure (but Paint can only allow me drawing in 2D), so even if some of the circuits are symmetric in amplitude, the phase is not, and its phase will interact with other non-symmetric circuit, so the outcome is not easy to understand.

Let's assume that these parasitic circuits are much smaller than the metal structure in which they are imbedded, and even if they are randomly distributed, it is highly unlikely that the affects will be cancelled out.
Attached Images
 circuit3.png (8.9 KB, 123 views)

rayma
diyAudio Member

Join Date: Apr 2011
Quote:
 Originally Posted by andy2 is it true that if all components are passive (R, L, C), then all circuits are symmetric
Not true. For example, circuit #2 in your post #2 is not symmetric.

Input voltage at left end gives Vout/Vin = R2/(R1+ R2)

Input voltage at right end gives Vout/Vin = [ R2/(R2 + 1/sC1) ] = sR2C1/(1+sR2C1)

Last edited by rayma; 12th July 2019 at 10:19 PM.

 12th July 2019, 10:32 PM #7 andy2   diyAudio Member   Join Date: Nov 2004 Location: StupidVille Yeah, if I could find a free on-line circuit analysis tool, it can be simulated. It is possible that the amplitude portion could be symmetric, but the phase may not be.
rayma
diyAudio Member

Join Date: Apr 2011
Quote:
 Originally Posted by andy2 It is possible that the amplitude portion could be symmetric, but the phase may not be.
Not in either respect.

 12th July 2019, 10:58 PM #9 andy2   diyAudio Member   Join Date: Nov 2004 Location: StupidVille It would be nice if someone could post a simulation run. In term of DC, it probably is not symmetric in term of amplitude, but if the source is a sine wave, then it's hard to visualize, at least for me. If we have a simulation run, then it would be definitive with input and output waveform.
rayma
diyAudio Member

Join Date: Apr 2011
Quote:
 Originally Posted by andy2 If we have a simulation run, then it would be definitive with input and output waveform.
See the circuit equations in post #6. Left and right input results are not the same,
so the circuit is not symmetric. For DC, set s=0. A capacitor does not pass DC.

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