# SPICE HELP

Status
Not open for further replies.

#### 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
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
Here how the Delay() function works in an Behavioral Voltage Source expression:

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

#### Attachments

• 448 bytes Views: 30
Last edited:

#### MikeMl

##### Well-Known Member
Here is how you vary the delay timing:

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

#### Attachments

• 11.8 KB Views: 34
Last edited:
Status
Not open for further replies.