EE229 2025 Activity 02

EE229 Activity 2: Nonlinearity (Due: Friday, 3/14, 5pm)

• Instructions: This activity a two-part problem, and you are expected to create a Google Colab file that contains your analysis and calculations, schematic, SPICE netlist, and simulation results. Please refer to this sample template. Copy the template to your Google drive, and edit as needed. Should you have any questions, clarifications, or issues, please contact your instructor as soon as possible.
• Submit your *.ipynb file here.
  • Please name your file LastName_FirstName_EE229_Activity02.ipynb.
• If you are new to ngspice, please refer to the ngspice user manual.
• At the end of this activity, the student should be able to:

1. Measure the nonlinearity in amplifiers using ngspice.

Part 0: Warm-Up

Go over the provided Google Colab notebook and make sure you understand how we simulated a simple common-source amplifier, obtained the output spectrum for different input voltages, and plotted the harmonic components as a function of the input voltage.

Note that running for the first time would restart the kernel, so you would need to run it again. Also, installing the Skywater 130nm design kit for the first time might take the Google servers around 10 minutes or so.

Part 1: Intermodulation (IM) Linearity Analysis

Given a simple common-source amplifier (in the provided Google Colab template) using the Skywater 130nm CMOS process:

1. Plot output spectrum and identify the intermodulation distortion terms, $IM_{2}$ and $IM_{3}$, and
2. Plot the fundamental and $IM_{3}$ versus the input signal, and calculate the input and output third-order intercept points, $OIP_{3}$ and $IIP_{3}$

Note: Use the input amplitudes given in the template, e.g. 2mV, 5mV, 10mV, 15mV, 20mV, and 25mV.

Part 2: Differential Amplifier Nonlinearity

Convert the given common-source amplifier to its differential equivalent, with approximately the same gain. Using the same input voltages as Part 1, but now as differential input voltages:

1. Draw the schematic of your circuit in the Google Colab notebook.
2. Plot the output spectrum of the differential output voltage, and identify the harmonic distortion terms $HD_{2}$ and $HD_{3}$.
3. Compare the output spectrum of the differential vs. the single-ended amplifier. Explain any differences.