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hysteresis using vcvs

gau27

Hi fellow forum users,

Guess most of you will read this only in the New Year, yet hope someone like me working just before x'mas will take a peek at my issue!

I'm toying with the vcvs PWL transfer char. to simulate a hysteresis comparator.

Sim errors saying I've got infinite slope for the PWL char. Not sure how we implement this.

Appreciate any ideas.

  • Your transfer function appears to have an error in it - I'm assuming input 3 should be avdd/2+Vh/2. Anyway, even with that corrected, this isn't going to work because it requires some kind of "state" to be maintained and the vcvs won't do that - it's a stateless transfer function (i.e. for every input value there's a single output value).

    Your best bet would be to write a VerilogA model. This model on the Designer's Guide site is a good start - it's a Verilog-AMS model and would need to be changed to have a voltage output rather than a logic output, but you get the idea: dg-vams4-14

    Regards,

    Andrew.

  • Thanks for the quick reply, Andrew.

    Yes, you're right about the  PWL input3 value, good spot!

    I was coding a veriloga model in parallel but still wanted something with ideal components without positive feedback. Anyhow, now I've got one with resistors implementing the hysteresis.

    Thanks & wish you a Merry Christmas

    Gautham

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