Lab 5

E-mail: gomezmar@unlv.nevada.edu
9/28/15

Lab description


The purpose of this lab was to layout and simulate an inverter.

Lab Report


12u/6u Inverter

  • First a schematic for the 12u/6u inverter was created.



  • A symbol was created from the above schematic with some text indicating the type of inverter.



  • Then a layout for the inverter was created to match the schematic.



  • A DRC check was performed to be sure there were no errors on the layout.



  • Then an LVS was performed between the schematic and extracted layout and the net-lists were found to match.



48u/24u Inverter

  • A schematic for the 48u/24u inverter was created.
  • The schematic from the 12u/6u inverter was copied but the multiplier for the MOSFETS was changed to 4.



  • A symbol was created from the above schematic with some text indicating the type of inverter.



  • Then a layout for the inverter was created to match the schematic.



  • A DRC check was performed to be sure there were no errors on the layout.



  • Then an LVS was performed between the schematic and extracted layout and the net-lists were found to match.



Inverter simulations

  • Then the inverters that were created were simulated driving a capacitive load.
  • We started by simulating the operation of the 12u/6u inverter.



  • With a load of 100fF the resulting simulation can be seen below.



  • With a load of 1pF it takes longer for the capacitor to charge and dischrage so the output takes longer to change.



  • With a load of 10pF it takes even longer for the capacitor to charge and discharge so the output takes longer to change.
  • Therefore the amount of time between input changes was chnaged in order to see the full operation of the inverter.



  • With a load of 100pF it takes even longer for the capacitor to charge and discharge so the output takes longer to change.
  • Therefore the amount of time between input changes was chnaged in order to see the full operation of the inverter.



  • Then the operation of the 48u/24u inverter was simulated.



  • With a load of 100fF the resulting simulation can be seen below.



  • With a load of 1pF it takes longer for the capacitor to charge and dischrage so the output takes longer to change.



  • With a load of 10pF it takes longer for the capacitor to charge and dischrage so the output takes longer to change.
  • Here we did not need to change the amount of time between changes in the input like we did with the 12u/6u inverter with the same load.
  • Therefore it can be seen that with the bigger inverter the capacitor charges and discharges faster.



  • With a load of 100pF it takes even longer for the capacitor to charge and discharge so the output takes longer to change.
  • Therefore the amount of time between input changes was chnaged in order to see the full operation of the inverter.



Using UltraSim

  • Then the above simulations were performed using UltraSim (Cadence's fast SPICE simulator).
  • The results obtained were really similar to the ones obtained previously, but small changes can be seen.
  • A comparison between the simulations can be seen below, the biggest differences can be seen when the output is going from changing to being still.
  • It can be seen that the changes take longer to be visible in UltraSim as it is not as accurate.



  • All of the files for this lab can be found here: lab5.zip