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Symmetric circuit (or not) then to a more difficult question
Symmetric circuit (or not) then to a more difficult question
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Old 12th July 2019, 07:20 PM   #1
andy2 is offline andy2  United States
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Default Symmetric circuit (or not) then to a more difficult question

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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
File Type: png circuit.png (7.4 KB, 129 views)

Last edited by andy2; 12th July 2019 at 07:24 PM.
 
Old 12th July 2019, 08:00 PM   #2
andy2 is offline andy2  United States
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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
File Type: png circuit2.png (8.9 KB, 129 views)
 
Old 12th July 2019, 08:04 PM   #3
nigelwright7557 is offline nigelwright7557  United Kingdom
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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.
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Old 12th July 2019, 08:17 PM   #4
andy2 is offline andy2  United States
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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).
 
Old 12th July 2019, 08:31 PM   #5
andy2 is offline andy2  United States
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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.
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File Type: png circuit3.png (8.9 KB, 123 views)
 
Old 12th July 2019, 10:08 PM   #6
rayma is online now rayma  United States
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Quote:
Originally Posted by andy2 View Post
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.
 
Old 12th July 2019, 10:32 PM   #7
andy2 is offline andy2  United States
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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.
 
Old 12th July 2019, 10:37 PM   #8
rayma is online now rayma  United States
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Originally Posted by andy2 View Post
It is possible that the amplitude portion could be symmetric,
but the phase may not be.
Not in either respect.
 
Old 12th July 2019, 10:58 PM   #9
andy2 is offline andy2  United States
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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.
 
Old 12th July 2019, 11:01 PM   #10
rayma is online now rayma  United States
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Originally Posted by andy2 View Post
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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