Mosplot

Mosplot is a Python framework for analog circuit design using the gm/ID methodology. It characterizes MOS transistors by simulation, builds design charts from the resulting data, and sizes complete circuits automatically across process corners.

The flow has three parts.

Lookup table generation. A DC sweep over length and terminal voltages is run with ngspice, HSPICE, or Spectre. The operating-point parameters (drain current, transconductances, output conductance, capacitances) are saved to one table per technology and corner. See lookup table generation.

Design charts. Current density, transit frequency, intrinsic gain, or any user expression can be plotted against gm/ID for each length, and exact values at an operating point are obtained by interpolation on the table. See design charts.

nmos = Mosfet(lookup_table=lookup_table, mos="nmos", vbs=0.0, vds=0.6)
nmos.plot_by_expression(
    x_expression=nmos.gmid_expression,
    y_expression=nmos.transit_frequency_expression,
    y2_expression=nmos.gain_expression,
)

Circuit optimization. A circuit is described once as a system of equations formulated with lookups into the table. The optimizer sizes it against the targets at all corners simultaneously, reports the performance at each corner, and writes a netlist for verification by simulation. Ready-made designs are included for amplifiers, current mirrors, and reference circuits; using one in a new technology needs only a configuration file with the tables, operating conditions, and targets. See circuit optimization.

Installation

Python 3.9 or later. Lookup table generation additionally requires one of the supported simulators (ngspice, HSPICE, or Spectre).

pip install git+https://github.com/medwatt/gmid.git

For development, install from a local clone:

git clone https://github.com/medwatt/gmid.git
cd gmid
pip install -e .

Citation

If this work is used in academic research, especially the optimization part, it would be nice if you could cite it:

@article{watfa2026residual,
  author  = {Watfa, Mohamed and Garcia-Ortiz, Alberto and Sassatelli, Gilles},
  title   = {A Residual-Equation Framework for {$\mathrm{gm}/I_D$} Analog Circuit Design
             with Automated Multicorner Sizing},
  journal = {IEEE Transactions on Circuits and Systems I: Regular Papers},
  year    = {2026},
  doi     = {10.1109/TCSI.2026.3736902}
}

Acknowledgments

The HSPICE output parser is based on hspiceParser.