LTspice plot totally different from one on text book, what am I doing wrong?

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nicologhezzi

Joined Dec 30, 2018
2
Hi everybody. Just learning by my self some electronics for hobby. I try to plot the LTspice circuit I have here attached but it spits out a plot totally different from the one the text book shows. What am I doing wrong? Thank you and many regards.
 

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MrAl

Joined Jun 17, 2014
7,601
Hi everybody. Just learning by my self some electronics for hobby. I try to plot the LTspice circuit I have here attached but it spits out a plot totally different from the one the text book shows. What am I doing wrong? Thank you and many regards.
Hi,

You might get some pretty wild responses from this if you have absolutely no resistances in the circuit.
Normally each inductor would have some resistance, and the source would have some resistance, and there would be a load as cruts says.
Not sure where you got this circuit but check back and see if you can find where they place the resistances.
The curves you see drawn are purely theoretical.
What else might help is to detune the circuit a little, making one set of LC slightly different than the others.
Also, maybe this exercise was not made to be done on a simulator at all? It may be that you are supposed to find the poles and zeros and draw the true Bode plot, and just imagine the real plot as they have drawn there.
If you can print the entire exercise question it might help to understand what they really want in total.
 

Ylli

Joined Nov 13, 2015
950
You basically have three sections all tuned to 15.9 KHz. But as others have said, you really need a source and load resistance for any measurements to be meaningful. In addition, when you cascade several LC sections like that, each LC section influences the others. You may find that the real needed values are quite a bit different the simply making all section resonant at the same frequency.
 
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