Transient Analysis

Contents

Transient Analysis#

Time-domain simulation of an IHP circuit using ngspice.

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 nyancad.plot import timeplot
from InSpice import Simulator

hv.extension("bokeh")

scipy not available, fft plots will not work

ⓘ

Parameters#

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

# -- Transient parameters --
STEP_TIME = 1e-5  # time step (s)
START_TIME = 0  # start time (s)
END_TIME = 1e-3  # end time (s)
MAX_TIME_STEP = 1e-4  # max time step (s), 0 to let ngspice choose
USE_INITIAL_CONDITION = False

# -- Vectors to plot (node voltages / branch currents) --
# Leave empty to auto-select all node voltages after simulation.
VECTORS = []

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

print("Netlist nodes:", list(spice.node_names))
print("Netlist elements:", list(spice.element_names))

Netlist nodes: ['0', 'W2', 'GND', 'W3', 'W6']
Netlist elements: ['VV1', 'VV2', 'XM1', 'XM2', 'CC1']

Run transient simulation#

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.transient(
    step_time=STEP_TIME,
    end_time=END_TIME,
    start_time=START_TIME,
    max_time=MAX_TIME_STEP if MAX_TIME_STEP > 0 else None,
    use_initial_condition=USE_INITIAL_CONDITION,
)
print("Transient analysis complete.")

Warning: can't find the initialization file spinit.

Newer Ngspice version that could be unsupported 46

Transient analysis complete.

Results#

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

if not VECTORS:
    VECTORS = list(analysis.nodes.keys())
    print("Auto-selected:", VECTORS)

df = pd.DataFrame(index=np.array(analysis.time))
for vec in VECTORS:
    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']
Auto-selected: ['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']

	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
0.000000e+00	0.0	0.900000	0.0	0.0	0.900000	0.0	0.162154	0.900000	1.8
1.000000e-07	0.0	0.900314	0.0	0.0	0.900314	0.0	0.162154	0.900314	1.8
2.000000e-07	0.0	0.900628	0.0	0.0	0.900628	0.0	0.162154	0.900628	1.8
4.000000e-07	0.0	0.901257	0.0	0.0	0.901257	0.0	0.162154	0.901257	1.8
8.000000e-07	0.0	0.902513	0.0	0.0	0.902513	0.0	0.162153	0.902513	1.8
1.600000e-06	0.0	0.905026	0.0	0.0	0.905026	0.0	0.162153	0.905026	1.8
3.200000e-06	0.0	0.910052	0.0	0.0	0.910052	0.0	0.162151	0.910052	1.8
6.400000e-06	0.0	0.920101	0.0	0.0	0.920101	0.0	0.162144	0.920101	1.8
1.280000e-05	0.0	0.940169	0.0	0.0	0.940169	0.0	0.162114	0.940169	1.8
2.560000e-05	0.0	0.980078	0.0	0.0	0.980078	0.0	0.161999	0.980078	1.8
5.120000e-05	0.0	1.058089	0.0	0.0	1.058089	0.0	0.161559	1.058089	1.8
1.024000e-04	0.0	1.199959	0.0	0.0	1.199959	0.0	0.160000	1.199959	1.8
2.024000e-04	0.0	1.377804	0.0	0.0	1.377804	0.0	0.155528	1.377804	1.8
3.024000e-04	0.0	1.373144	0.0	0.0	1.373144	0.0	0.150494	1.373144	1.8
4.024000e-04	0.0	1.187760	0.0	0.0	1.187760	0.0	0.146276	1.187760	1.8
5.024000e-04	0.0	0.892460	0.0	0.0	0.892460	0.0	0.144661	0.892460	1.8
6.024000e-04	0.0	0.600041	0.0	0.0	0.600041	0.0	0.147135	0.600041	1.8
7.024000e-04	0.0	0.422196	0.0	0.0	0.422196	0.0	0.152982	0.422196	1.8
8.024000e-04	0.0	0.426856	0.0	0.0	0.426856	0.0	0.159944	0.426856	1.8
9.024000e-04	0.0	0.612240	0.0	0.0	0.612240	0.0	0.165662	0.612240	1.8
1.000000e-03	0.0	0.900000	0.0	0.0	0.900000	0.0	0.167841	0.900000	1.8

timeplot(df).opts(responsive=True, height=500)