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Taking the derivative produces a strange line plot

yannisuno

 Hello,

 I have a single NMOS device for which I sweep Vgs while keeping Vds constant.

 Ploting the drain current Id and taking its derivative, instead of producting a single line plot, I obtain a two lines plot which both connected to each other. Therefore, this plot is worng. I am using ver. IC6.1.4.

 Anyone knows what the problem is?

 Thanks,

Yannis

 

  • Not enough information to really help - most likely it's "finger trouble" but hard to know without knowing the precise details of what you're trying to do - it ought to work. Please state exactly what analysis you have set up (ideally include the input.scs) and if you're doing parametric analysis in ADE too, describe what you're doing.

    Also give the expression that  you're plotting, and ideally a picture of the resulting graph (you can save the graph as an image).

    Andrew

  •  Hello,

    first of all, many thanks for the reply.

    All I am trying to do is to plot the drain current Id of a single biased device (NMOS).

    It's a DC analysis that I am doing sweeping Vgs while keeping Vds at 10% of VDD.

    The expression in the calculator is the following: deriv(IS("/NM0/D"))

    and this is the plot I am getting:

    http://img843.imageshack.us/i/snapshotv.png/

  • Did you check the "hysteresis" checkbox on the DC form? That would sweep both up and then down - and so I can imagine you could get a similar trace. What do you get if you plot the signal (without the deriv)?

    Regards,

    Andrew.

  •  Yes, that solved the problem!

     Thanks!

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