CMOS Folded-Cascode OpAmp Generator

Disclaimer

• This is experimental.
• This tool does not always generate working opamp parameters.
• According to my test results, users still need quite much knowledge in analog IC design to make the generated parameters work well.
• The value of this tool may be saving hand calculation time.

Usage

1. Install Node.js and git.

2. Open a terminal, enter the following commands (the same on Windows, Linux, macOS).

   Clone the repository

   git clone https://github.com/dragonman225/opamp-generator.git

   Go into the directory

   cd opamp-generator

   Install Javascript libraries

   npm install

3. Edit src/config.yml. Change the process dependent parameters and performance specifications.

4. Start the interactive generator

   npm run start

• Check below for instance names of the MOSFETs.

Advanced Stuff

Using lambda lookup table

To consider channel-length modulation and get optimized MOSFET sizes, a lambda lookup table is needed. However, since the relationship of lambda and gate length is process-dependent, I do not provide my lookup table here. You need to do a simulation using your process model and save the lambda v.s. gate length curve as a compatiple CSV file described below, then edit the config to import.

1. Make your CSV file look like this. It can contain arbitrary rows of data.

   length,lambda_n,lambda_p
   1.8E-07,0.6,0.4
   1.9E-07,0.58,0.36
   2E-07,0.55,0.33
   

   • length is gate length in meters. lambda_n is lambda of NMOS. lambda_p is lambda of PMOS.
   • Hints :
     • lambda = 1 / (Id * ro - Vds).
     • Do simulation with given Id, Vds, and measure ro to get lambda. You can sweep through a range of gate length, and plot the results.
     • To maintain Id at different gate length, W/L ratio need to be constant, so width should also change with gate length.
     • Export the plotted NMOS and PMOS curves as CSV, and use Microsoft Excel or LibreOffice Calc to combine them, also change the column names.
2. Open src/config.yml, edit the lambda_table property. Change its value to your path. Absolute path is recommended.

   lambda_table: your_csv_lookup_table.csv

Concepts of Design Procedure

Please see presentation file : https://slides.com/aic999/deck