[Multisim] AC Analysis and Transient Analysis problem

Discussion in 'The Projects Forum' started by Surtur, May 1, 2016.

  1. Surtur

    Thread Starter New Member

    Nov 22, 2015
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    0
    Hello everyone hope you are having good day. I'm trying to design 3 band pass filters in multisim that allows signals (10kHz,31kHz,51kHz) to pass. Well I designed so then while simulating them through AC analysis and I obtained satisfying results. But when it comes to Transient Analysis, output voltages make no sense at all. By the way, I'm converting the output signal to DC voltage using rectifier circuit. Can anyone notice the problem? You can see the circuit and the analysis results at the attachments. Thanks already.
     
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  2. crutschow

    Expert

    Mar 14, 2008
    13,019
    3,235
    What do you expect to see for the transient analysis?
    Why are you using a 1MHz input frequency?
    Your AC analysis looks like you are not using enough points for the plot.
    Why did you using a slow 1A rectifier instead of a small signal diode to rectify the signal?
     
  3. Surtur

    Thread Starter New Member

    Nov 22, 2015
    7
    0
    I would like to see 3 sharp bands with low bandwidth.
    I used 1MHz frequency just to see what happens.
    You are right, now I used 1000 points and the result is in attachment.
    Well, I do not have that much knowledge about diodes and didnt figure out which diode I should use. Could you suggest one?
     
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  4. crutschow

    Expert

    Mar 14, 2008
    13,019
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    A 1N4148 is a common small-signal diode.

    You didn't answer my question about what you expect to see in the transient response simulation.

    The highest frequency bandpass filter has a slow rolloff as compared to the other two filters. Is that what you wanted?
    If not, then there would seem to be an error in one or more of the part values for that filter.
     
  5. Surtur

    Thread Starter New Member

    Nov 22, 2015
    7
    0
    Okay I used the diode that you suggested and modified the filters. now Q is much higher than before and my transient analysis is far better. In transient analysis I wanted to obtain DC voltages for a given certain signal(10kHz, 31kHZ or 51kHz). incresing Q allowed me to obtain these. thank you problem is solved :D
     
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