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Spice Simulation help

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ANALA

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DELAY= exp[(Vth2-Vth1)/n*Vth] Is there any way so that i can input this equation to the SPICE tool and plot Delay Vs supply voltage?
 

Seems to me that you would instead simulate the circuit
and take the results of a .measure statement (set) -
if you want to calculate and plot from "inputs" then a
tool like Excel or Matlab seems more suitable.

I've used SPICE variants that had robust command-line
interfaces and could do stuff like this (loop, calc, stuff
to a vector, endloop, plot vector) but not sure whether
this is really practical in a "standard" SPICE with a
divorced waveform viewer, etc.
 

DELAY= exp[(Vth2-Vth1)/n*Vth] Is there any way so that i can input this equation to the SPICE tool and plot Delay Vs supply voltage?

If the variables Vth1, Vth2, n and Vth are all plotable vs supply voltage, then most packages will plot the equation vs supply voltage. I use Pspice and it will plot your equation.
 
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    ANALA

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My first step would be to implement and simulate an inverter using a particular technology node and plot delay vs supply voltage graph for different values of Vth.

Next i want to validate my model against the simulated one using my proposed equation and compare the 2 graphs...since i m knew to SPICE i dont know how to go ahead with the second step..

I basically want to know how can i enter the mentioned equation n plot the graph for different values of Vth,Vth1, Vth2 and supply voltage?

- - - Updated - - -

can you let me know the procedure so that i can plot the mentioned equation...it would be of great help..
 

I'd suggest you run a DC simulation with 2 nested sweeps, one sweep over your Vs range, another one over a (Vth2-Vth1) range.
From the simulation results it should be possible to plot your a.m. interrelation (DELAY) as a set of curves vs. Vs, with (Vth2-Vth1) as curve parameter.
 

Thank you but this is my first step which i m aware of...I m not sure how to calculate the delay using my proposed equation..
 

Delays are operators that affect process execution, they are not treated as electrical primitives, therefore this certainly would not be possible to simulate in SPICE due to a recursive access to the time variable. I mean, if both voltages varies along the time, the above equation should rather be wrote as this:

Code:
DELAY(t)= exp[(Vth2(t)-Vth1(t))/n*Vth(t)]

Anyway, if you just want to use SPICE as a plot tool, you can use the "voltage-dependent-voltage-source" to build a signal source ( with the purpose to be measured, not to supply anything ) having other signals as its argument along with any math opperations. I have used this approach in LTspice for example to convert the voltage read at certain point to the equivalent current seen at uC ADC result. Note that on its argument there are either constant parameter ( V_BUS=5v ) as well as a signal took from the actual circuit ( ADC_RES(t) ):

VDVS.png

For your case, you could use both the Vth1 and Vth2 as constant parameters for that equation.
 

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