CSE 493/593 Fall 2023
Lab Assignments

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Lab 3: Implementation of a edge-triggered DFF using TG logic

For this lab, you will have to implement a positive edge-triggered D Flip Flop using Transmission Gate Logic

  1. Familiarize yourself with the difference between flipflops and latches.
  2. During simulation, make sure your stimuli (D and CLK) do not have same rising and falling edges. You should be able to demonstrate the functioning of the DFF for all cases and combinations of inputs.
  3. Keep the width of the PMOS transistors double the width of the NMOS transistors. The width of the NMOS and PMOS transistors should be 1.5um and 3um, respectively. Their lengths can both be set to 0.6um. Consider rise time and fall time to be 0.01ns.
  4. If your design requires, you can reuse the gates designed in Lab 0 and 1

Lab 2: Transistor Sizing a Complex CMOS Gate (Due: 10/24 in Lab)

Size all the transistors from Lab 1: Part III for

  1. Performance
  2. Symmetric rise and fall times

Reference: Transistor Sizing a Complex CMOS Gate from Lecture 6.

In all cases(including minimum W/L), report your observations(Propagation Delays, Rise/Fall times, Power Consumption) with supporting extracted view simulation results.

Lab 1: Getting Started with Cadence - Implementation of Basic Logic Gates (Due: 9/25, 9/26 in Lab)

What you can do before coming to the lab:

 

1.     It is highly recommended that you go over the Cadence setup and tutorial pages as you work on this assignment to correctly setup your tool and access. Follow all steps given under Cadence setup. The documentation provided under the help menu in each cadence tool also contains detailed information on using the tools.

2.     Go through the lecture that has covered the design of Complementary CMOS circuits and work on designing the circuit. This saves you time during the lab session and you have more time to work on your cadence implementation.

Part-I: CMOS Inverter Design

Design a CMOS inverter in Cadence. The width of the NMOS and PMOS transistors should be 1.5µm and 3µm, respectively. Their lengths can both be set to 0.6µm.

For simulations, set the inverter input signal to have a rise time of 0.5ns, fall time of 0.5ns, pulse width of 2ns, period of 5ns. Use model files, util/cadence/local/ncsu-cdk-1.6.0.beta-20150506/models/spectre/standalone/ami06N.m and /util/cadence/local/ncsu-cdk-1.6.0.beta-20150506/models/spectre/standalone/ami06P.m

  1. Create the inverter schematic using Virtuoso Schematic L
  2. Simulate the inverter using Spectre simulator in the Analog Design Environment L tool. Measure the propagation delay of the inverter in the waveform window
  3. Create an inverter symbol using Virtuoso Schematic L
  4. Layout the inverter in Virtuoso Layout XL. Extract the layout and simulate it. Measure the propagation delay of the inverter in the waveform window
  5. Is there a difference in the propagation delays between the circuit schematic and layout? Why/Why not?

Propagation Delay (tp): Propagation delay expresses the delay experienced by a signal when passing through a gate. tpLH defines the response time of the gate for a low to high output transition, while tpHL refers to a high to low transition. The overall propagation delay is conservatively defined as the average of the two delays tpLH and tpHL.

 

Part-II: Basic Logic Gates

You will have to implement the schematic and layout for basic 2-input gates

i.                 NAND

ii.                NOR

iii.              XOR

 

Create symbols for each schematic.

 

Useful tips:

 

1. Another important thing to note is to keep the width of the PMOS transistors double the width of the NMOS transistors. The width of the NMOS and PMOS transistors should be 1.5µm and 3µm, respectively. Their lengths can both be set to 0.6µm.

2. As you have to design 2-input gates, you should test your circuit for all possible combination of inputs. This can be done using two pulse inputs, one with twice the time period of the other. Another effective method to give stimuli is using bit inputs with 0.01ns rise and fall times.

Part-III: Implementation of Logic Function

Implement the given logic function using CMOS logic (Transistor level diagram).

F = ^[((AB)+C)D]

 

Size all transistors with their minimum default W/L