Added initial script for generating plots from FET simulator

Signed-off-by: Grzegorz Latosinski <glatosinski@antmicro.com>

scripts/python-skywater-pdk/skywater_pdk/fet_simulator/fet_simulator.py

@@ -0,0 +1,166 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#
+# Copyright 2020 SkyWater PDK Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import PySpice.Logging.Logging as Logging
+logger = Logging.setup_logging()
+from PySpice.Spice.Netlist import Circuit
+from PySpice.Unit import *
+import matplotlib.pyplot as plt
+from pathlib import Path
+import csv
+
+
+def create_test_circuit(fet_type, iparam, fet_L, fet_W, corner_path):
+    c=Circuit('gm_id')
+    c.include(corner_path)
+
+    # create the circuit
+    c.V('gg', 1, c.gnd, 0@u_V)
+    c.V('dd', 2, c.gnd, 1.8@u_V)
+    c.X('M1', fet_type, 2, 1, c.gnd, c.gnd, L=fet_L, W=fet_W, ad="'W*0.29'", pd="'2*(W+0.29)'", as_="'W*0.29'", ps="'2*(W+0.29)'", nrd="'0.29/W'", nrs="'0.29/W'", sa=0, sb=0, sd=0, nf=1, mult=1)
+    return c 
+
+
+def run_sim(c, iparam, fet_W):
+    sim = c.simulator()
+    sim.save_internal_parameters(iparam%'gm', iparam%'id', iparam%'gds', iparam%'cgg')
+
+    # run the dc simulation
+    an = sim.dc(Vgg=slice(0, 1.8, 0.01))
+
+    # calculate needed values..need as_ndarray() since most of these have None as the unit and that causes an error
+    gm_id = an.internal_parameters[iparam%'gm'].as_ndarray() / an.internal_parameters[iparam%'id'].as_ndarray()
+    ft = an.internal_parameters[iparam%'gm'].as_ndarray() / an.internal_parameters[iparam%'cgg'].as_ndarray()
+    id_W = an.internal_parameters[iparam%'id'].as_ndarray() / fet_W
+    gm_gds = an.internal_parameters[iparam%'gm'].as_ndarray() / an.internal_parameters[iparam%'gds'].as_ndarray()
+
+    return gm_id, ft, id_W, gm_gds, an.nodes['v-sweep']
+
+
+def init_plots():
+    figs = [plt.figure(), plt.figure(), plt.figure(), plt.figure()]
+    plts = [f.subplots() for f in figs]
+    figs[0].suptitle('Id/W vs gm/Id')
+    plts[0].set_xlabel("gm/Id")
+    plts[0].set_ylabel("Id/W")
+    figs[1].suptitle('fT vs gm/Id')
+    plts[1].set_xlabel("gm/Id")
+    plts[1].set_ylabel("f_T")
+    figs[2].suptitle('gm/gds vs gm/Id')
+    plts[2].set_xlabel("gm/Id")
+    plts[2].set_ylabel("gm/gds")
+    figs[3].suptitle('gm/Id vs Vgg')
+    plts[3].set_xlabel("Vgg")
+    plts[3].set_ylabel("gm/Id")
+    return figs, plts
+
+
+def gen_plots(gm_id, id_W, ft, gm_gds, vsweep, fet_W, fet_L, plts):
+    # plot some interesting things
+    plts[0].plot(gm_id, id_W, label=f'W {fet_W} x L {fet_L}')
+    plts[1].plot(gm_id, ft, label=f'W {fet_W} x L {fet_L}')
+    plts[2].plot(gm_id, gm_gds, label=f'W {fet_W} x L {fet_L}')
+    plts[3].plot(vsweep, gm_id, label=f'W {fet_W} x L {fet_L}')
+
+
+def read_bins(fname):
+    with open(fname, 'r') as f:
+        r = csv.reader(f)
+        return r
+
+
+def generate_fet_plots(fet_type, corner_path, bins_csv, outdir, outprefix, only_W=None, ext='png'):
+    iparam = f'@m.xm1.m{fet_type}[%s]'
+    # fet_W and fet_L values here are only for initialization, they are
+    # later changed in the for loop
+    c = create_test_circuit(fet_type, iparam, 0.15, 1, corner_path)
+    f = open(bins_csv, 'r')
+    bins = csv.reader(f)
+    # skip header
+    next(bins)
+
+    figs, plts = init_plots()
+    for dev, bin, fet_W, fet_L in bins:
+        fet_W, fet_L = float(fet_W), float(fet_L)
+        if only_W is not None and fet_W not in only_W:
+            continue
+        c.element('XM1').parameters['W'] = fet_W
+        c.element('XM1').parameters['L'] = fet_L
+        gm_id, ft, id_W, gm_gds, vsweep = run_sim(c, iparam, fet_W)
+        gen_plots(gm_id, id_W, ft, gm_gds, vsweep, fet_W, fet_L, plts)
+
+    figtitles = ['Id_w', 'fT', 'gm_gds', 'gm_id']
+    for fg, name in zip(figs, figtitles):
+        fg.legend()
+        fg.tight_layout()
+        fg.savefig(Path(outdir) / (outprefix + f'_{name}.{ext}'))
+    f.close()
+
+
+if __name__ == '__main__':
+    import argparse
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        'fet_type',
+        help='FET type to simulate'
+    )
+    parser.add_argument(
+        'corner_path',
+        help='Path to corner SPICE file containing FET definition',
+        type=Path
+    )
+    parser.add_argument(
+        'bins_csv',
+        help='Path to CSV file with fet_type, bin, fet_W and fet_L parameters',
+        type=Path
+    )
+    parser.add_argument(
+        'outdir',
+        help='Path to the directory to save the plots to',
+        type=Path
+    )
+    parser.add_argument(
+        '--outprefix',
+        help='The prefix to add to plot file names'
+    )
+    parser.add_argument(
+        '--only-w',
+        help='Simulate the FET only for a given fet_W values',
+        nargs='+',
+        type=float
+    )
+    parser.add_argument(
+        '--ext',
+        help='The image extension to use for figures',
+        default='png'
+    )
+    args = parser.parse_args()
+
+    if args.outprefix is None:
+        args.outprefix = args.fet_type
+
+    generate_fet_plots(
+        args.fet_type,
+        args.corner_path,
+        args.bins_csv,
+        args.outdir,
+        args.outprefix,
+        args.only_w,
+        args.ext)