The goal of this project is to design and layout a ring oscillator cell. Ring oscillators are widely used in digital electronics for various applications including voltage-control oscillators and hardware security. In this project you are asked to design the layout, and simulate a 5-stage ring oscillator cell. The circuit diagram of the ring oscillator is shown below. Top design with the minimum layout area will receive 10% bonus credit for this project.


                                    

1. The students will form groups of no more than four for this project. Make sure that the work is divided equally between the members of each group.
2. Design and test an inverter, first. Once you confirm the simulation results and DRC for the inverter block, then combine the inverters.
3. A student version of L-Edit is now available for this project. The L-Edit executable file is ledit.exe for download. All the design rules and layer definitions are in a setup file ledit.tdb. Ledit reads ledit.tdb, once it is launched. To perform circuit extraction, the device definition is in template.ext. Copy all three files into the directory that you create and work for this project. Design your layout, perform the design rule check (DRC), and extract SPICE file using L-Edit. To start, you can use this example, ledit_demo.tdb. Also you can download L-Edit Quick Start Guide for a brief tutorial for L-Edit.
4. The design rules for this project is a standard 2um process from MOSIS with 2 metal layers. Download and print the Design Rules for your reference . Use SCMOS column from the design rule tables. 
5. You can download and use the free student version of PSPICE. To start the tool, you can try the sample circuit file. A comprehensive user's guide for PSPICE can also be helpful. Please keep in mind that this student version of PSPICE cannot handle any circuit with more than 10 transistors.
6. Once the extracted SPICE file is created, use PSPICE transistor model that defines the MOSFETs and then perform the simulations by adding input voltage sources and commands to the extracted SPICE file.
7. The nominal power supply voltage is 5 V. Also, the ring oscillator must contain no more than 5 inverters because the student version of PSPICE can handle no more than 10 transistors.

A written report that contains the following items is required. Please email your report (doc or pdf) as well as your LEdit and SPICE files to me (pzarkesh@unm.edu) by the due date.

1. Brief explanation on how you designed your ring oscillator cell.
2. Screen shot of the complete layout with X and Y dimensions and the total area.
3. Original SPICE file (circuit netlist). The SPICE file must be generated by LEdit but have your added commands for the needed simulations.
4. Waveform from PSPICE simulation that shows the functionality of the ring oscillator. Clearly show the period of oscillation on the waveform. 
6. Summarize your layout area and measured frequency in a table.
7. A table showing the hour spent for each task by each member of the group.