transient analysis

i have done a simulation on Bandpass filter. but when i do AC analysis i will get a straight line of input signal. how can i get continuous cycles of input signal. thankyou.

eSim 16-02-18, 8:45 p.m. sounndarrajan.v




You will be giving a wide range of frequencies, and you will be select AC as transient analysis.
Hence it shows Amplitude as a single line that is maintained across these frequency ranges.

16-02-18, 11:55 p.m. Gloria

Sorry I can't get you.?

Will you explain it once again? 
You mean I have to do transient analysis not an AC analysis right....
If I select transient and give start,stop,step Time no graph is plot.

17-02-18, 7:01 a.m. sounndarrajan.v


The Ac analysis will give you the frequency response for a different set of frequencies. If you want to see the frequency plot, you need to use plot_log.  So, the Amplitude will be represented in a single line, assuming we are giving the AC signal of constant amplitude.
If you want t see the transient analysis, you need to change the AC from eSim_source to Sine and use plot_v to see the response with respect to time. But, the sine will be of a single frequency.

17-02-18, 12:03 p.m. Gloria

if i change AC to sine source nothing is displayed.
if you want anything to see in project file??

17-02-18, 7:55 p.m. sounndarrajan.v

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I hope you understood the difference between AC analysis and Transient Analysis.

Please submit the project file. If there are any file missing, we will let you know.

17-02-18, 8:07 p.m. Gloria

of course, i know the differences.
i have seen others had done transient analysis and get continuous cycles of a sine wave while plotting.
but i cannot find it. if i rectify that it will help with the current project and future project as well.

17-02-18, 9:55 p.m. sounndarrajan.v


In the transient analysis based on the time step and the constant frequency(50,100,1Khz..), you will get the plot as sine signal. 
Since you are designing BPF, you need to plot the frequency response for a set of frequencies(1 to 1Mhz, 100 to 20Khz). To select the frequency range, you need to select AC analysis. In Ac analysis, the AC input has constant amplitude but the frequency changes. This is the reason, you will not be getting the plot of the sine wave over the set of frequencies.  

17-02-18, 10:16 p.m. Gloria

is it possible to get continuous sine wave in voltage plot(plot_v1) other than all things are working good.
only having doubt in that printing voltage plot.

17-02-18, 10:20 p.m. sounndarrajan.v

I think you have connected both plot_log and plot_v with the same node name.

Try to give different labels and then simulate it.

17-02-18, 10:34 p.m. Gloria

just keep BPF aside......
ok, let me know one thing when i place plot_v1 across input AC voltage(sine or AC) what will be the plotting?
whether it will be a straignt line or a continuous cycle of input.
if it is a straight line, what source is used to get a continuous wave?

17-02-18, 11:08 p.m. sounndarrajan.v

you will get amplitude plot(straight line).

You cannot get the continuous signal with AC analysis because of different frequency range.

17-02-18, 11:37 p.m. Gloria

how can I get a continuous plot?
when I do transient analysis it shows some errors..... but in AC analysis i get perfect output...

18-02-18, 6:23 p.m. sounndarrajan.v


Please understand the difference between the AC analysis and Transient analysis.
If you see plot_v the x-axis is with respect to time. So, as frequency changes the Time changes. So when you give set of frequencies the plot with respect to time varies. That is the reason, you will not get the continous signal. It is assumed as continuous because it is AC. 
When you give transient analysis, you give a SINGLE frequency. That means the time is constant. You will get a sine wave.

19-02-18, 11:09 a.m. Gloria

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