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INVERTER DELAY LTSPICE

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ANALA

New Member
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

Well-Known Member
Most Helpful Member
Post your .asc file.

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

alec_t

Well-Known Member
Most Helpful Member
Post your asc file, so that we can see what you are currently doing.
 

ANALA

New Member
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
 

alec_t

Well-Known Member
Most Helpful Member
Attached is your schematic marked up with one way you could change the supply voltage to test the effect on signal delay.
 

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alec_t

Well-Known Member
Most Helpful Member
Mike told you how in post #2.
 

eTech

Well-Known Member
you can do it like this:

inverter_prop_delay.png

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).
 

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MikeMl

Well-Known Member
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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.

DT.png

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.
 
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