Laboratory 03/04: A CMOS Inverter

Jörg Vollrath


Please do an electronic evaluation of the class microelectronics:

Static IV curves and dynamic behavior of an Inverter in 50nm technology are simulated. This practical training looks at the electrical behavior of a basic inverter in 50nm technology.

Inspecting the library for an Inverter

Open Electric. Load your Preferences from the last Laboratory. Change Preferences, Technology, Scale to mocmos scale 25nm. Change grid to 0.5 (icon in top row). Close all open libraries.
Load the library Lab02.jelib
Select "Use All New Settings"
Check one of the cells for design rules DRC. PFETs should be 2 by 10 and NFETs 2 by 7.

There are 4 Inverters in the library: inv_1x1, Inv_a, Inv_b, inv_3x1.

Design an inverter cell inv_9x1 with 9 unit transistors in parallel.
Add this inverter to the cell InvChain_dc.
Under tab 'Components' select 'Cell' and select your cell.
To look at the details of the cell use the Eye icon.

There are 2 simulations available: InvChain_dc; InvChainlong.

Simulate an Inverter

Select InvChain_dc {lay}.
Simulate it with SPICE.
Look at the voltages vin, vout1..vout5.

Make a printout (softcopy) of the result. What do you see? Why are the curves shifted?

Select InvChainlong{lay}

Simulate it with SPICE.
Look at the voltages vin, vout1..vout8.
Make a printout (softcopy) of the result. What do you see?
Measure the delay between input and output of the individual inverter for rising and falling output by comparing the 50% level.
Summarize the results. What do you see?
Measure the transition times from 10% to 90% of the level.
Calculate the transition times using SPICE measurement directives like:
.MEAS TRAN T2_V0790 WHEN V(vout7)=V(VDD)/2 FALL=1
Measure (.MEAS) in the transient simulation (TRAN) the time value named T2_V0790, when (WHEN) the voltage vout7 (V(vout7)) equals 0.9V at the first falling transition (FALL=1).
Each measurement value needs a unique label.
Use the LTSPICE Help function to look for .MEAS.
A propagation delay can be calculated using for example:
For each output voltage include a SPICE command to measure the transition times.
You can see the transition times in LTSPICE using View -> SPICE Error Log.
Copy the results to an editor or Excel for later use.


The report should include
1) Your experience during the practical training.
What obstacles did you experience how did you solve them? Please work in groups. You should also note down times you spent for each task.
2) Screenshots
Please send your electronic report including your names, group number and lab number to The filename should be < date:yyyy_mm_dd > _Lab03_ < LastName > .pdf.
Please obey the names rule, do not zip or tar the files.
You can use PDFCreator for creating pdf files via the print menue in Windows.