Distortion Analysis

Analyze harmonic or spectral distortion in the circuit.

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
import pandas as pd
import holoviews as hv
from nyancad.watch import watch_project_dir, file_schematic
from nyancad.netlist import inspice_netlist
from InSpice import Simulator

hv.extension("bokeh")

ⓘ

Parameters

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

# -- Distortion parameters --
VARIATION = "dec"  # point spacing: "dec", "oct", or "lin"
NUM_POINTS = 10  # number of points
START_FREQ = 100  # start frequency (Hz)
STOP_FREQ = 1e4  # stop frequency (Hz)
F2_OVER_F1 = 0.9  # F2/F1 ratio for intermodulation (None for harmonic only)
SPECTRAL = False  # enable spectral (intermodulation) analysis

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)

Duplicated lib ('ihp/models/ngspice/models/cornerMOSlv.lib', 'mos_tt')

.title schematic
.lib /Users/pepijndevos/code/IHP/ihp/models/ngspice/models/cornerMOSlv.lib mos_tt
VV1 W2 GND DC 1.8
VV2 W3 GND DC 0.9 AC 1 sin(0.9 0.5 1k)
XM1 W6 W3 GND GND sg13_lv_nmos l={0.13 * 1e-6} m=1 ng=1 w={0.15 * 1e-6}
XM2 W2 W3 W6 W2 sg13_lv_pmos l={0.13 * 1e-6} m=1 ng=1 w={0.15 * 1e-6}
CC1 W6 GND 1u

Run distortion 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.distortion(
    variation=VARIATION,
    points=NUM_POINTS,
    start_frequency=START_FREQ,
    stop_frequency=STOP_FREQ,
    f2overf1=F2_OVER_F1 if SPECTRAL else None,
)
print("Distortion analysis complete.")

Warning: can't find the initialization file spinit.

Newer Ngspice version that could be unsupported 46

Distortion analysis complete.

Results

available = [*analysis.nodes.keys(), *analysis.branches.keys()]
print("Available vectors:", available)

df = pd.DataFrame(index=np.array(analysis.frequency))
for vec in analysis.nodes.keys():
    df[vec] = np.array(analysis[vec])
df

Available vectors: ['n.xm1.nsg13_lv_nmos#SI', 'n.xm1.nsg13_lv_nmos#GP', 'n.xm1.nsg13_lv_nmos#NOI', 'n.xm2.nsg13_lv_pmos#SI', 'n.xm2.nsg13_lv_pmos#GP', 'n.xm2.nsg13_lv_pmos#NOI', 'w6', 'w3', 'w2', 'vv1', 'vv2']

	n.xm1.nsg13_lv_nmos#SI	n.xm1.nsg13_lv_nmos#GP	n.xm1.nsg13_lv_nmos#NOI	n.xm2.nsg13_lv_pmos#SI	n.xm2.nsg13_lv_pmos#GP	n.xm2.nsg13_lv_pmos#NOI	w6	w3	w2
100.000000	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
125.892541	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
158.489319	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
199.526231	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
251.188643	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
316.227766	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
398.107171	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
501.187234	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
630.957344	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
794.328235	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
1000.000000	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
1258.925412	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
1584.893192	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
1995.262315	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
2511.886432	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
3162.277660	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
3981.071706	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
5011.872336	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
6309.573445	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
7943.282347	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j
10000.000000	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j	0.0+0.0j

plot = hv.NdOverlay(
    {
        k: hv.Curve((df.index, np.abs(df[k])), "Frequency (Hz)", "Distortion").opts(
            logx=True, logy=True
        )
        for k in df.columns
    }
)
plot.opts(responsive=True, height=500)

WARNING:param.OverlayPlot00356: Logarithmic axis range encountered value less than or equal to zero, please supply explicit lower bound to override default of 0.010.