INVERTER DELAY LTSPICE

[ANALA]

I have simulated the inverter using LTSPICE...I m using this tool for the first time...I want to
1. measure the inverter delay
2. plot delay vs supply voltage

May i know the procedure to perform these two steps..

 

[MikeMl]

Post your .asc file.

You can measure delay from the plot, or using a .measure statement.

 

[ANALA]

Post your .asc file.

You can measure delay from the plot, or using a .measure statement.

But how do I do it for different values of supply voltage ?

 

[alec_t]

Post your asc file, so that we can see what you are currently doing.

 

[ANALA]

As requested i have posted .asc file on which i m working on...its basically a simple inverter...i want to measure the delay and plot it against supply voltage for different values of VDD

 

[ANALA]

Post your .asc file.

You can measure delay from the plot, or using a .measure statement.

Have attached the .asc file as requested.

 

[ANALA]

Post your asc file, so that we can see what you are currently doing.

Have attached the file as requested..

 

[alec_t]

Attached is your schematic marked up with one way you could change the supply voltage to test the effect on signal delay.

 

[ANALA]

Attached is your schematic marked up with one way you could change the supply voltage to test the effect on signal delay.

how do i measure the delay without using plot?

 

[alec_t]

Mike told you how in post #2.

 

[eTech]

you can do it like this:



1. Run trans simulation
2. view Spice error log
3. rht-click "Measurement: prop_delay"
4. select "plot .step'd meas'd data"
5. rht-click in new graph
6. select "add traces"
7. select "prop_delay"

But to use this method you have to use .measure statement(s).

 

[MikeMl]

Here a more thorough approach. Note that to realistically display the transit delay, you need to make the clock amplitude a function of Vdd. Furthermore, it is more realistic to drive the gates of the inverter under test with a signal that comes from another similar capacitively-loaded stage; not from an ideal voltage source with near-infinite rise/fall times.

I show how to use the cursors built-into the plot pane to display the delay from 50% on the red V(in) on the upper pane to the red V(out) on the lower pane.



The ultimate inverter delay measurement method is to build a ring-oscillator out of an odd number of inverters, typically 11 to 31 stages, and then just measure the frequency of oscillation.