UWASIC Optimizer

Circuit parameter optimization library for XSchem analog design workflows using ngspice.

Development

Prerequisites

# Option 1: nixshell
nix-shell
# Option 2: download xschem and ngspice

maturin develop # Generate the python library
pytest test/ -v # Run Tests
python examples/optimizer.py # Run example

Python-Side Usage

Parameter Naming

Parameters must follow the format: COMPONENT_PARAMETER

• M1_W → alters width of transistor M1
• M1_L → alters length of transistor M1
• R1 → alters value of resistor R1

The library automatically maps parameter names to ngspice component parameters:

• Suffix _W → transistor width (uses @component[w] syntax)
• Suffix _L → transistor length (uses @component[l] syntax)
• Suffix _M → multiplier (uses @component[m] syntax)
• No suffix → component value (for R, C, etc.)

Control Blocks & Vector Naming

The library automatically handles .control and .endc blocks:

# Target definition
Target(metric="GBW", ...)

spice_code="""
.ac dec 50 1 1G
.control
run
meas ac gbw_val WHEN vdb(vout)=0 CROSS=1
.endc
"""

Example Structure

template/
├── OpAmp.sch        # Schematic
├── OpAmp.sym        # Symbol
└── OpAmp_tb.sch     # Testbench (required)
test_flow.py

The optimizer:

1. Generates netlist from OpAmp_tb.sch using xschem
2. Loads circuit into ngspice
3. Alters parameters for each iteration
4. Runs tests and extracts metrics
5. Computes cost and optimizes

Constraints

from uwasic_optimizer import ParameterConstraint, RelationshipType

constraints = [
    ParameterConstraint(
        target_param=M1_W,
        source_params=[M2_W],
        expression="XM2_W",  # M1_W = M2_W
        relationship=RelationshipType.Equals,
        description="Match differential pair widths",
    ),
]

Every parameter on the right hand side must be defined in source_params, you can use any valid mathetmatical expression in expression. The python side will tell you if you are missing any parameters or wrote an incorrect expression.

Supported relationships:

• Equals: target = expression
• GreaterThan: target > expression
• GreaterThanOrEqual: target ≥ expression
• LessThan: target < expression
• LessThanOrEqual: target ≤ expression

Publish to PyPi

git tag v0.0.* && git push origin v0.0.*