def run_main():
interp_method = 'spline'
sim_env = 'tt'
nmos_spec = 'specs_mos_char/nch_w0d5.yaml'
pmos_spec = 'specs_mos_char/pch_w0d5.yaml'
intent = 'lvt'
nch_db = get_db(nmos_spec, intent, interp_method=interp_method,
sim_env=sim_env)
nch_op = nch_db.query(vbs=0, vds=0.5, vgs=0.5)
pprint.pprint(nch_op)
# building circuit
cir = LTICircuit()
cir.add_transistor(nch_op, 'out', 'in', 'gnd', 'gnd', fg=2)
cir.add_res(10e3, 'out', 'gnd')
cir.add_cap(100e-15, 'out', 'gnd')
# get gain/poles/zeros/bode plot
trans_fun = cir.get_transfer_function('in', 'out', in_type='v')
print('poles: %s' % trans_fun.poles)
print('zeros: %s' % trans_fun.zeros)
# note: don't use the gain attribute. For some reason it's broken
print('gain: %.4g' % (trans_fun.num[-1] / trans_fun.den[-1]))
fvec = np.logspace(5, 10, 1000)
_, mag, phase = sig.bode(trans_fun, w=2 * np.pi * fvec)
# get transient response
state_space = cir.get_state_space('in', 'out', in_type='v')
tvec = np.linspace(0, 1e-8, 1000)
_, yvec = sig.step(state_space, T=tvec)
_, (ax0, ax1) = plt.subplots(2, sharex=True)
ax0.semilogx(fvec, mag)
ax0.set_ylabel('Magnitude (dB)')
ax1.semilogx(fvec, phase)
ax1.set_ylabel('Phase (degrees)')
ax1.set_xlabel('Frequency (Hz)')
plt.figure(2)
plt.plot(tvec, yvec)
plt.ylabel('Output (V/V)')
plt.xlabel('Time (s)')
plt.show()
def characterize_casc_amp(env_list,
lch,
intent_list,
fg_list,
w_list,
db_list,
vbias_list,
vload_list,
vtail_list,
vmid_list,
vincm,
voutcm,
vdd,
vin_clip,
clip_ratio_min,
cw,
rw,
fanout,
ton,
k_settle_targ,
scale_min=0.25,
scale_max=20):
# compute DC transfer function curve and compute linearity spec
ndb, pdb = db_list[0], db_list[-1]
results = solve_casc_diff_dc(env_list,
ndb,
pdb,
lch,
intent_list,
w_list,
fg_list,
vbias_list,
vload_list,
vtail_list,
vmid_list,
vdd,
vincm,
voutcm,
vin_clip,
clip_ratio_min,
num_points=20)
vmat_list, ratio_list, gain_list = results
# compute settling ratio
fg_tail, fg_in, fg_casc, fg_load = fg_list
db_tail, db_in, db_casc, db_load = db_list
w_tail, w_in, w_casc, w_load = w_list
fzin = 1.0 / (2 * ton)
wzin = 2 * np.pi * fzin
tvec = np.linspace(0, ton, 200, endpoint=True)
scale_list = []
cin_list = []
for env, vbias, vload, vtail, vmid, vmat in zip(env_list, vbias_list,
vload_list, vtail_list,
vmid_list, vmat_list):
# step 1: get half circuit parameters and compute input capacitance
in_par = db_in.query(env=env,
w=w_in,
vbs=-vtail,
vds=vmid - vtail,
vgs=vincm - vtail)
casc_par = db_casc.query(env=env,
w=w_casc,
vbs=-vmid,
vds=voutcm - vmid,
vgs=vdd - vmid)
load_par = db_load.query(env=env,
w=w_load,
vbs=0,
vds=voutcm - vdd,
vgs=vload - vdd)
cir = LTICircuit()
cir.add_transistor(in_par, 'mid', 'in', 'gnd', fg=fg_in)
cir.add_transistor(casc_par, 'out', 'gnd', 'mid', fg=fg_casc)
cir.add_transistor(load_par, 'out', 'gnd', 'gnd', fg=fg_load)
zin = cir.get_impedance('in', fzin)
cin = (1 / zin).imag / wzin
cin_list.append(cin)
# step 3A: construct differential circuit with vin_clip / 2.
vts, vmps, vmns, vops, vons = vmat[-1, :]
vinp = vincm + vin_clip / 4
vinn = vincm - vin_clip / 4
tail_par = db_tail.query(env=env, w=w_tail, vbs=0, vds=vts, vgs=vbias)
inp_par = db_in.query(env=env,
w=w_in,
vbs=-vts,
vds=vmns - vts,
vgs=vinp - vts)
inn_par = db_in.query(env=env,
w=w_in,
vbs=-vts,
vds=vmps - vts,
vgs=vinn - vts)
cascp_par = db_casc.query(env=env,
w=w_casc,
vbs=-vmns,
vds=vons - vmns,
vgs=vdd - vmns)
cascn_par = db_casc.query(env=env,
w=w_casc,
vbs=-vmps,
vds=vops - vmps,
vgs=vdd - vmps)
loadp_par = db_load.query(env=env,
w=w_load,
vbs=0,
vds=vons - vdd,
vgs=vload - vdd)
loadn_par = db_load.query(env=env,
w=w_load,
vbs=0,
vds=vops - vdd,
vgs=vload - vdd)
cir = LTICircuit()
cir.add_transistor(tail_par, 'tail', 'gnd', 'gnd', fg=fg_tail)
cir.add_transistor(inp_par, 'midn', 'inp', 'tail', fg=fg_in)
cir.add_transistor(inn_par, 'midp', 'inn', 'tail', fg=fg_in)
cir.add_transistor(cascp_par, 'dn', 'gnd', 'midn', fg=fg_casc)
cir.add_transistor(cascn_par, 'dp', 'gnd', 'midp', fg=fg_casc)
cir.add_transistor(loadp_par, 'dn', 'gnd', 'gnd', fg=fg_load)
cir.add_transistor(loadn_par, 'dp', 'gnd', 'gnd', fg=fg_load)
cir.add_vcvs(0.5, 'inp', 'gnd', 'inac', 'gnd')
cir.add_vcvs(-0.5, 'inn', 'gnd', 'inac', 'gnd')
# step 3B: compute DC gain
cir.add_vcvs(1, 'dac', 'gnd', 'dp', 'dn')
dc_tf = cir.get_transfer_function('inac', 'dac')
_, gain_vec = dc_tf.freqresp(w=[0.1])
dc_gain = gain_vec[0].real
# step 3C add cap loading
cload = fanout * cin
cir.add_cap(cload, 'outp', 'gnd')
cir.add_cap(cload, 'outn', 'gnd')
cir.add_vcvs(1, 'outac', 'gnd', 'outp', 'outn')
# step 4: find scale factor to achieve k_settle
# noinspection PyUnresolvedReferences
scale_swp = np.arange(scale_min, scale_max, 0.25).tolist()
max_kset = 0
opt_scale = 0
for cur_scale in scale_swp:
# add scaled wired parasitics
cap_cur = cw / 2 / cur_scale
res_cur = rw * cur_scale
cir.add_cap(cap_cur, 'dp', 'gnd')
cir.add_cap(cap_cur, 'dn', 'gnd')
cir.add_cap(cap_cur, 'outp', 'gnd')
cir.add_cap(cap_cur, 'outn', 'gnd')
cir.add_res(res_cur, 'dp', 'outp')
cir.add_res(res_cur, 'dn', 'outn')
# get settling factor
sys = cir.get_state_space('inac', 'outac')
_, yvec = scipy.signal.step(
sys, T=tvec) # type: Tuple[np.ndarray, np.ndarray]
k_settle_cur = yvec[-1] / dc_gain
# print('scale = %.4g, k_settle = %.4g' % (cur_scale, k_settle_cur))
# update next scale factor
if k_settle_cur > max_kset:
max_kset = k_settle_cur
opt_scale = cur_scale
else:
# k_settle is decreasing, break
break
if max_kset >= k_settle_targ:
break
# remove wire parasitics
cir.add_cap(-cap_cur, 'dp', 'gnd')
cir.add_cap(-cap_cur, 'dn', 'gnd')
cir.add_cap(-cap_cur, 'outp', 'gnd')
cir.add_cap(-cap_cur, 'outn', 'gnd')
cir.add_res(-res_cur, 'dp', 'outp')
cir.add_res(-res_cur, 'dn', 'outn')
if max_kset < k_settle_targ:
raise ValueError('%s max kset = %.4g @ scale = %.4g, '
'cannot meet settling time spec.' %
(env, max_kset, opt_scale))
scale_list.append(opt_scale)
return vmat_list, ratio_list, gain_list, scale_list, cin_list