• Cadence Lab 1 18/08/23
  • Initial Instructions
  • Add elements
  • Open ADE L for analysis
  • Selecting Outputs
  • Display the I_d V_g curve
  • Output
  • Fullforms
  • Next lab session : Resistive Inverter
• Cadence Lab 2 25/08/23
  • Design Resisitive Load Inverter in Cadence.
  • Output
  • Possible Viva Questions
• Cadence Lab 3 01/09/23
  • CMOS Inverter using symbols
  • Output
• Cadence Lab 4 08/09/23
  • NAND, NOR, EXOR, EXNOR
  • Output
    • NAND Gate
• Cadence Lab 5 15/09/23
  • Half Adder, Full Adder
  • Output
• Viva Questions Finals
• Quiz
• End of Cadence 😄

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Cadence Lab 1 18/08/23

Initial Instructions

Open terminal in work folder

Create new library with desired name, under technology file click "Attach to a existing technology library".

Select "gpdk180" under the technology library to attach.

Create new cellview from the File section (top left of window).
Give name to cellview and wait a few seconds to get a grid workarea. We Integrate all instances here.

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Add elements

To add an instance, click I. Browse for libraries and select gpdk_180. From component select NMOS and select. Hover over the black grid area to drop the selected item.

Select library as analogLib and cell vdc, to get dc_voltage source. Create two dc sources for the component. Go to instance and add ground, mentioned as GND (from the same library analogLib).

To connect different components of the circuit, use narrow wire (right beside the add instance icon in the taskbar)

Give value to both voltage sources, by editing values from the property editor. Simply left click on the component to open its property editor. After giving suitable values, click on the "check and save" icon once.

Open ADE L for analysis

To go setup => Model libraries

Go to comp => / => TOOLS => PDK => gpdk180 v3.3 => models => spectre => gpdk.scs

This should put address of gpdk.scs into the Model Library Setup page. Under the "Section", choose "NN" from the dropdown. Click on Ok, to save NN. NN stands for Normal Normal.

Tasks

1. I_d V_d curve
2. I_d V_g curve

In the simulation window (ADE) choose AC DC trans.

Sweep variable : component parameter
Select voltage source at drain side, and choose voltage.
Change start, stop values.

Selecting Outputs

Outputs => To be plotted => Select on schematic
Click on node to get current values, clicking on wires will give voltage values.
This should update the ADE L panel, under outputs window NMO/D will be added. D stands for Drain.

Click on play button (green) on the right hand side. This will open up a Visualization window with a graph of I (in milli amperes) vs V (in Voltage).

Display the I_d V_g curve

Click on voltage source, click on dc voltage.
Outputs => To be plotted => Select on design => Select node of gate.

For multiple sweeps at once.
Go to tools => Parametertic Analysis
Click on left hand side, add variable, dropdown, select V_gs. Define uppper and lower limit "from" and "to", Step Mode : "Auto", Total Steps : 5

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Output

1. I_d vs V_d multiple V_g
   

2. I_d vs V_d
   

3. I_d vs V_g multiple V_d
   

4. I_d vs V_g
   

5. Circuit Schematic
   

Fullforms

"gpdk" , "ADE L" full form
ADE : Analog Design Environment
gpdk : Generic Process Design Kit

Next lab session : Resistive Inverter

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Cadence Lab 2 25/08/23

Design Resisitive Load Inverter in Cadence.

Similar to NMOS
Maintain record of previous lab-sessions (Objective, schematic, output, graph, calculation)

Resistor : 1 kilo ohm
Pulse width : 2s

Output

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Possible Viva Questions

1. Differentiate between pulse width and time period

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Cadence Lab 3 01/09/23

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CMOS Inverter using symbols

Why symbols
To make construction of complex circuits easier

Create pins (second from right in the top right corner)
V_dd V_ss and A are input pins
Y is an output pin

Check n save

Create => cellview => from cellview

Give top, bottom, left, right pins. Assign where each pin would be.

To use this as a black-box, create new cellview and import this using 'I'.

Run transient analysis, DC analysis.
Plot input and output, check where do the two graphs cross each other.

The crossing point should have voltage nearly equal to half of the input voltage

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Output

1. Inverter

2. Inverter_dc

3. Inverter_dc_with_input

4. Inverter_dc_with_multiple_input

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Cadence Lab 4 08/09/23

Extra Lab on Tuesday (12th September)

NAND, NOR, EXOR, EXNOR

Commands to open cadence
source_cshrs_new_12
virtuoso &
A window opens, click on new => cellview

To create NAND gate, use two pmos and to nmos, from the gpdk180_new library.
Circuit diagram is as follows :

NOTE : pMOS should be on top, nMOS should be on bottom.

Give inputs A, B such that all combinations of a two-bit system are available as inputs
As in, these combinations should exist [ (0,0), (0,1), (1,0), (1,1) ]

Create a symbol for the circuit, with A and B as left pins,V_dd as the top pin, GND as the bottom pin and C as the right pin (for output)

Close this window, from the CLI click on new_cellview and import the symbol created (from the roll_number wala folder).
Connect the pins with appropriate instances,
Period should be double that of width.

For voltage supply, choose a V_dc

Launch ADEL, import model libraries, choose NN. Select "tran" analysis

Output

NAND Gate

1. Output
   
   

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Cadence Lab 5 15/09/23

Half Adder, Full Adder

Submit hard copy of file by 12midnight, 15th september

Output

1. Half Adder circuit
   

   

2. Half Adder symbol
   

   

3. Half Adder Output
   

   

4. Full Adder circuit
   

   

5. Full Adder symbol
   

   

6. Full Adder Output
   

   

Viva Questions Finals

1. Implement given function using CMOS
2. What is work function, bandgap, electron affinity ?
3. What is threshold voltage ? Formula for the same
4. Types of capacitances in MOSFET
   • Gate capacitance
   • Wire capacitance
5. Why do we use MOSFETS ?
   • More chips can be fit in same silicon chip
   • Relatively faster
   • Better noise margin

Quiz

1. Full form of gpdk
   • Generic Process Design Kits
2. Full form of ADE
   • Analog Design Environment
3. Why do we see spiked when input signal switches ?
4. Which one is better CMOS inverter or resistive load inverter.
5. Draw the CMOS implementation for given functions.
6. Minimum number of transistors required to implement
   • Half Adder (spoiler alert 6)
   • Bhool gaya, cannot remember
7. What are universal gates ? Why are they named such.
   • NAND
   • NOR

End of Cadence 😄

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