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    Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Dear friends,

    I am trying to plot the GBW of my amplifiier under the whole range of the input common mode voltage (VIC). Therefore I run both the DC and AC analyses in the same time, I sweep the VIC from the DC setup from 0 to 3.3 V and from the AC analyses I must get the GBW.

    The problem when I run this setting the simulator is not giving me the GBW for every step in VIC, he is ignoring the DC sweep.

    I make trick to overcome this problem by sweeping the DC from the parametric analyses, it works fine but it is time consuming.

    Can you please suggest me method to fix the problem from DC analyses.

    Mr. Suta has already proposed me a solution for similar case but that setting was only to plot the transistor parameters.

    Thank you in advance

    Best Regards

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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Instead of doing a DC sweep, can you do a transient sweep of your VIC and run .ac at different points (time points which you have to enter by hand) of the transient sweep?


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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    DC Analysis is not required.

    Simply do parametric sweep for AC analysis from Cadence ADE.
    Or enclose ac analysis statement by sweep statement in netlist.


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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Quote Originally Posted by sutapanaki View Post
    Instead of doing a DC sweep, can you do a transient sweep of your VIC and run .ac at different points (time points which you have to enter by hand) of the transient sweep?
    Dear Suta,
    my supervisor suggested me not to include transient analyses to sweep the VIC, because transient simulation first it takes time and second it shows time behavoural of the circuit which we do not want to include in our basic ac simulation

    - - - Updated - - -

    Quote Originally Posted by pancho_hideboo View Post
    DC Analysis is not required.

    Simply do parametric sweep for AC analysis from Cadence ADE.
    Or enclose ac analysis statement by sweep statement in netlist.
    Dear pancho,
    Thank you for your reply,

    That is actually what I am doing right now, I am sweeping the VIC from parametric, but parametric takes more time than sweeping from DC analyses.
    Why sweeping VIC from DC analyses is not connected to ac simulation for every step ? or it is the nature of ADE simulator ?



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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Show me netlist when you invoke parametric sweep.


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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Quote Originally Posted by Junus2012 View Post
    Dear Suta,
    my supervisor suggested me not to include transient analyses to sweep the VIC, because transient simulation first it takes time and second it shows time behavoural of the circuit which we do not want to include in our basic ac simulation

    - - - Updated - - -



    It is true that transient may exercise time behavior of the circuit but this is in case if you change you VIC too fast. If the change is slow enough, then it is pretty much like DC.


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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Quote Originally Posted by pancho_hideboo View Post
    Show me netlist when you invoke parametric sweep.

    Dear Pancho,

    The parametric has no problem, it is well working, but I am asking why the simulation fail to present data in grpah if I do the sweep from DC ?

    - - - Updated - - -

    See the image below to better explain,

    you see the graph of the ICMR which I want to have, x-axis is the VIC that I sweep from 0 to 3.3.
    AV is the gain I should have from AC simulation

    Now the first thing I do is to run the DC and AC simulation together, the AC simulation to find the AV, the DC simulation is to sweep the VIC. This setup fails, the simulator is not running AC for every change in the VIC, he only take one value of VIC (the default value which i put to 1.65 V) then he run the AC simulation on it.

    in my second setup I only run the AC simulation, but I sweep the VIC by using the parametric sweep, this configuration is working.

    Click image for larger version. 

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    thank you once again again

    - - - Updated - - -

    Quote Originally Posted by sutapanaki View Post
    It is true that transient may exercise time behavior of the circuit but this is in case if you change you VIC too fast. If the change is slow enough, then it is pretty much like DC.
    Dear Suta,

    That is the reason why I would like to run it by transient



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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Dear friends,

    I recieved an answer from Cadence,

    there are two solutions:

    1. Simulation using ADE Explorer to set up the surrounding sweep, then spectre would (normally) run with similar efficiency to having a native sweep. That's because it groups the runs and ADE tells spectre to run each set of analyses without quitting the simulator - so you don't need to generate a new netlist, re-start the simulator, regain the license, parse the netlist and so on - spectre will change the parameter value in memory.

    Unfortunately my Cadence version is old and not supporting ADE Explorer

    2. By making Parametric analyses run faster

    check what:

    envGetVal("spectre.envOpts" "controlMode")

    returns. If that returns "interactive", then doing the parametric sweep should be quick (assuming you're not running in distributed mode in ADE L). If it's set to "batch" then do:

    envSetVal("spectre.envOpts" "controlMode" 'string "interactive")

    and restart ADE L and try the parametric analysis tool again.



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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Quote Originally Posted by Junus2012 View Post
    1. Simulation using ADE Explorer to set up the surrounding sweep,
    then spectre would (normally) run with similar efficiency to having a native sweep.
    I don't think so.

    Both ADE-XL(GXL) and ADE-Explorer have very large over head.
    So multiple sweep simulation speed is very slow compared to Spectre's native sweep ability.

    See "spectre -h sweep".
    https://www.edaboard.com/showthread.php?387035#3

    Quote Originally Posted by Junus2012 View Post
    Unfortunately my Cadence version is old and not supporting ADE Explorer
    https://www.edaboard.com/showthread.php?373647
    https://www.edaboard.com/showthread.php?381680

    Don't rely on Cadence-ADE.
    Rather don't use Cadence-ADE.
    Last edited by pancho_hideboo; 20th October 2019 at 07:06.


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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Quote Originally Posted by pancho_hideboo View Post
    I don't think so.

    Both ADE-XL(GXL) and ADE-Explorer have very large over head.
    So multiple sweep simulation speed is very slow compared to Spectre's native sweep ability.

    See "spectre -h sweep".
    https://www.edaboard.com/showthread.php?387035#3


    https://www.edaboard.com/showthread.php?373647
    https://www.edaboard.com/showthread.php?381680

    Don't rely on Cadence-ADE.
    Rather don't use Cadence-ADE.
    Dear Pancho,
    Thank you very much for your nice links,

    referring to your statment ''Or enclose ac analysis statement by sweep statement in netlist'', how to implement it? I am not familiar with Ocian in running my simulation, Only I use the GUI of the ADE

    To your next statement "Don't rely on Cadence-ADE.
    Rather don't use Cadence-ADE"

    What you suggest me then to use ?

    Thank you very much once again



  11. #11
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    Re: Problem in saving data during DC sweep simulation in Cadence Virtuoso

    Quote Originally Posted by Junus2012 View Post
    I am not familiar with Ocian in running my simulation
    OCEAN is not required.
    OCEAN is no more than an assistant of generating netlist.

    Quote Originally Posted by Junus2012 View Post
    What you suggest me then to use ?
    Excecute simulation from netlist directly as same as HSPICE.

    Modifying netlist manually.
    You can never utilize full ability of Cadence Spectre as far as you use GUI.


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