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 Help with complete understanding of "vsin" source in Cadence 

Last post Wed, May 14 2014 6:03 PM by jdp721. 8 replies.
Started by jdp721 11 May 2014 11:16 AM. Topic has 8 replies and 653 views
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  • Sun, May 11 2014 11:16 AM

    • jdp721
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    Help with complete understanding of "vsin" source in Cadence Reply
    Hi.

    I kind of thoroughly Googled before posting this question for seeking help from you guys! 

    The "vsin" source (in analogLib) of Cadence has many parameters: 

    i) AC magnitude, AC phase, DC voltage
    ii) Offset voltage, Amplitude, Frequency,...

    Question 1: Internet resources are indicating that parameters in (i) are for AC analysis, while that in (ii) are for Transient analysis - IS THIS TRUE? - because, I have seen in Cadence that changing the "AC phase" led to change in the Transient output waveform - is it so that the "AC phase" field is common between AC and Tran analyses?

    Question 2: what is the use of the "DC voltage" in (i) above? - because, I am seeing that people are setting this to '0 V' most of the times without any explanation!
    • Post Points: 20
  • Sun, May 11 2014 8:43 PM

    • smlogan
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    Re: Help with complete understanding of "vsin" source in Cadence Reply

    Dear jdp721,

     

    Q 1. Parameters AC magnitude and AC phase are only effective in an AC analysis. AC phase does not change the phase of vsin in a transient analysis - at least it does not in IC6.1. There is a parameter "Initial phase for sinusoid" than can be set to a non-zero value to set the phase of the source in a transient analysis. "DC voltage" sets the DC value of vsin in a DC operating point analysis or AV analysis. The vsin parameter "Offset voltage" sets the DC average of the vsin source in a transient analysis.

     Q 2. The DC voltage parameter can be used to set the DC value of the vsin source in a DC operating point analysis. This value can be different than parameter "Offset voltage" which is the average value in a transient analysis.

     

    This is what I observed from running a few test cases in IC6.1 and I hope this is useful.

    Shawn 

     

     

    • Post Points: 20
  • Mon, May 12 2014 2:20 AM

    Re: Help with complete understanding of "vsin" source in Cadence Reply

    Just to clarify what Shawn said. If you specify the DC voltage but not the "Offset voltage", when the DC voltage will be used as the mid-voltage of the sinusoid. If Offset voltage is specified, that is used instead (for the transient).

    For a DC analysis (or for any small signal analysis that requires a DC operating point), the DC value of the source is taken as the DC voltage (if specified), or if not specified, it's the time-zero value of the source. These could of course be different...

    Shawn is absolutely right in saying that the AC phase does not affect transient. It's the initial phase for sinusoid that affects that.

    I would generally recommend using vsource rather than vsin (they're the same thing in spectre) because the parameters are better organized.

    Regards

    Andrew.

    • Post Points: 35
  • Mon, May 12 2014 8:01 AM

    • smlogan
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    Re: Help with complete understanding of "vsin" source in Cadence Reply

     Hi Andrew,

     

    Thank you for your clarification concerning the use of parameter DC voltage in vsin during a transient analysis when "Offset voltage" is left blank. You are absolutely correct. I have noticed this and should have included it! Good poiint (again!).

     

    Shawn

    • Post Points: 20
  • Mon, May 12 2014 9:30 AM

    • jdp721
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    Re: Help with complete understanding of "vsin" source in Cadence Reply
    Many thanks Shawn and Andrew for your helpful replies - I simulated "vsin" for different settings and confirmed all the aspects that you pointed out above :) Goodbye!
    • Post Points: 5
  • Tue, May 13 2014 7:28 PM

    • jdp721
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    Re: Help with complete understanding of "vsin" source in Cadence Reply

    One more question - maybe it's too trivial:

    Does the properties of instances (e.g., "vsin" etc.) from "analogLib" used in the schematic change with the simulator (e.g., "spectre") being used? 

     

     

    • Post Points: 20
  • Wed, May 14 2014 11:04 AM

    • Tawna
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    Re: Help with complete understanding of "vsin" source in Cadence Reply

    Yes, they do.  Not all properties on an analogLib component (e.g. vsin, vsource, isource, port, etc.) are supported by all simulators.

    In fact, I recommend using vsource with sourcetype=sine instead of vsin if you are simulating with Spectre.  vsin is a subset of vsource.  New features are put into vsource. vsource has a much more intuitive GUI. 

    Similarly, if using spectre, I recommend port (instead of psin).  All of the port properties are documented in the SpectreRF User Guide (version 13.1 and 13.1.1).  Many of the port properties are the same as the vsource properties.

     best regards,

    Tawna

    best regards,

    Tawna

    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 5
  • Wed, May 14 2014 11:34 AM

    • Tawna
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    Re: Help with complete understanding of "vsin" source in Cadence Reply

    One more thing...

    Use the Tool Filter (In IC616, go to Options-Tool Filter) to limit what parameters are displayed in the schematic and in the Edit Properties/Add Instance form.

    For example, if you choose hspice (and deselect all others) and OK the form, you will see a different parameter set than if you check spectre (and deselect all others).

    best regards,

    Tawna

    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 20
  • Wed, May 14 2014 6:03 PM

    • jdp721
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    Re: Help with complete understanding of "vsin" source in Cadence Reply
    Many thanks Tawna for those very helpful and detailed reply and suggestions :-)
    • Post Points: 5
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Started by jdp721 at 11 May 2014 11:16 AM. Topic has 8 replies.