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| Doubts about SPICE analysis |
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| RawCode:
Hello there! I'm an electronic enginering student, and at the moment I'm attending the ECAD subject. I use Micro-Cap 12.0.2.1 Evaluation Version as a ECAD software, and at the moment I can't switch to something simpler like LTSPICE, since i have to take an exam with Micro-Cap. First thing: what is, what is the purpose and when i should use the PSS(Periodic Steady State) analysis in the transient analysis? I was messing around with a guitar effect, but I found something strange in the simulation. Let's start. First thing strange: i was studying this buffer stage, which has this spectral response: Is that normal that i get a transient response (a sinusoidal wave @60k) of this kind? I mean, i know that there is a resonance at more or less 11kHz, but i didn't expected this behavior at the beginning, because i'm "far" from the resonance. (Blu=input, Red= output) Here it is another strange thing. I was analyzing the input and output impedance of this stage with the ac analysis - i'm using a what micro-cap calls "generic model" for the opamp.(blu=input, red=output) But in the plot of the analysis, it shows something strange, like a "resonance of impedance" at more or less 12kHz of almost 1Meg, and everywhere else an impedance of 10k. For me at least this is very strange, because i expected something near zero impedance. but if i remove the toggle to the option "operating point" i get this kind of impedance, which is more "reasonable". What am i doing wrong? Can you help me? |
| exe:
The oscillation could compensation/stability issue of the opamp. Which opamp is that? Anyway, I'd first increase the compensation cap to see if behavior changes. |
| RawCode:
--- Quote from: exe on March 10, 2019, 10:15:04 pm ---The oscillation could compensation/stability issue of the opamp. Which opamp is that? Anyway, I'd first increase the compensation cap to see if behavior changes. --- End quote --- I'm using the ne5532. I solved the issue with the impedance though, doing the analysis of the input impedance grounding the output and vice versa. I thought that I could do the complessive impedance analysis in one shot Inviato dal mio LG-H930 utilizzando Tapatalk |
| exe:
Did you ground the output of opamp? |
| RawCode:
Yes I did. Anyway I solved this simulation issues and all my doubts. Thanks :) Inviato dal mio LG-H930 utilizzando Tapatalk |
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