DC Sensitivity Analysis

Compute sensitivity of DC operating point to device parameters.

import os
import sys
from pathlib import Path

# Set working directory to the PDK root if running from scripts/
if Path.cwd().name == "scripts":
    os.chdir(Path.cwd().parent)

# Ensure ngspice shared library can be found (macOS homebrew)
if sys.platform == "darwin" and "/opt/homebrew/lib" not in os.environ.get(
    "DYLD_LIBRARY_PATH", ""
):
    os.environ["DYLD_LIBRARY_PATH"] = "/opt/homebrew/lib:" + os.environ.get(
        "DYLD_LIBRARY_PATH", ""
    )

import numpy as np
from nyancad.watch import watch_project_dir, file_schematic
from nyancad.netlist import inspice_netlist
from InSpice import Simulator

Parameters

SCHEMATIC = "rcfilter"  # stem of the .nyancir file
CORNER = "mos_tt"

# -- DC sensitivity parameters --
OUTPUT_VAR = "v(P2)"  # output variable to analyze sensitivity for

Load schematic and build netlist

project = watch_project_dir(".")
schem_data = await file_schematic(project, SCHEMATIC)
spice = await inspice_netlist(SCHEMATIC, schem_data, corner=CORNER)
print(spice)

.title schematic
VV1 net0 GND DC 0 AC 1
CC1 P2 net0 1u
RR1 P2 GND 1k

Run DC sensitivity analysis

simulator = Simulator.factory(simulator="ngspice-shared")

for osdi in [
    "ihp/models/ngspice/osdi/psp103.osdi",
    "ihp/models/ngspice/osdi/psp103_nqs.osdi",
    "ihp/models/ngspice/osdi/r3_cmc.osdi",
    "ihp/models/ngspice/osdi/mosvar.osdi",
]:
    simulator._ngspice_shared.exec_command(f"osdi {osdi}")

simulation = simulator.simulation(spice)
analysis = simulation.dc_sensitivity(
    output_variable=OUTPUT_VAR,
)
print("DC sensitivity analysis complete.")

Warning: can't find the initialization file spinit.

Newer Ngspice version that could be unsupported 46

DC sensitivity analysis complete.

Results

print(f"DC sensitivity of {OUTPUT_VAR}:")
for key in analysis.nodes.keys():
    val = np.array(analysis[key]).item()
    if abs(val) > 1e-12:
        print(f"  {key} = {val:.6g}")

DC sensitivity of v(P2):