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SPICE HELP

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ANALA

New Member
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?
 

alec_t

Well-Known Member
Most Helpful Member
Welcome to ETO!
You can use the DELAY function to characterise a Behavioral Voltage or Behavioral Current source.
 

ANALA

New Member
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?
 

MikeMl

Well-Known Member
Most Helpful Member
Here how the Delay() function works in an Behavioral Voltage Source expression:

51.png

I delay V(in) by 200us, and multiply it by 2. Read the LTSpice Help file for circuit element B.
 

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MikeMl

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Most Helpful Member
Here is how you vary the delay timing:51a.png


You can make either argument to Delay() a function of various things. Either argument can be an arbitrarily complex expression which is a function of some node voltage, branch current, or a varying parameter as I show above.
 

Mosaic

Well-Known Member
To get a power graph (rather than a voltage y-axis) from a Behavioral Voltage component 'power expression', use a 1A current source on the output of the B component and Alt-click the Current source to display dissipated Watts on the graph.
 

ANALA

New Member
Here is how you vary the delay timing:View attachment 107549


You can make either argument to Delay() a function of various things. Either argument can be an arbitrarily complex expression which is a function of some node voltage, branch current, or a varying parameter as I show above.
I don't wish to introduce delay in my waveform but rather i want to calculate the delay of the inverter using my proposed equation. The simulated circuit can be used to calculate delay..this i m aware of..but in the second step i want to validate my proposed model against the simulated one...so how do i do this?
 

ci139

Active Member
proposed equation
the eq. at #1 is quite simplistic - that is - it means it's more likely to "match" (loosely) a huge amount of experiment data (with systematic errors -- not shown in your formula) why don't you show us the part of the grid with test points on the signal path & everything in between

the Spice is likely evt.-wise driven "quanted computation table" that hopefully preserves the energy conservation law e.g. all it's timing data is questionable or requires a sophisticated simulation setup . . .

+ your formulas dimensional (unit-wise) analysis makes me wonder how you get DELAY dimensioned by (SI) second considering the cap formula for example
 

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