summaryrefslogtreecommitdiffstatshomepage
path: root/src/lib/netlist/analog/nld_mosfet.cpp
blob: ea717fdefee1cdba3d9d3fd7d30e5eb851a491da (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
// license:GPL-2.0+
// copyright-holders:Couriersud
/*
 * nld_mosfet.cpp
 *
 * Formulas in here based on the following Sources:
 *
 * https://www.imperial.ac.uk/pls/portallive/docs/1/7292573.PDF
 * http://www3.imperial.ac.uk/pls/portallive/docs/1/56133736.PDF
 * https://people.rit.edu/lffeee/SPICE_MOSFET_Model_Intro.pdf
 * https://people.rit.edu/lffeee/SPICE.pdf
 * http://web.mit.edu/course/6/6.012/SPR98/www/lectures/S98_Lecture10.pdf
 * http://homepages.rpi.edu/~sawyes/Models_review.pdf
 * http://jaco.ec.t.kanazawa-u.ac.jp/edu/mix/pdf/3.pdf
 *
 * Farid N. Naim, Circuit Simulation (Wiley-IEEE Press, 2010).
 * Stefan Jahn, Michael Margraf, Vincent Habchi and Raimund Jacob, "Qucs Technical Papers" (2007)
 *
 */

#include "netlist/solver/nld_solver.h"
#include "netlist/nl_setup.h"
#include "nlid_twoterm.h"

#include <cmath>

#define BODY_CONNECTED_TO_SOURCE	(1)

namespace netlist
{
namespace analog
{

	using constants = plib::constants<nl_double>;

	// -----------------------------------------------------------------------------
	// nld_FET - Base classes
	// -----------------------------------------------------------------------------

	/*! Class representing the nmos model paramers.
	 *
	 *  This is the model representation of the nmos model. Typically, SPICE uses
	 *  the following parameters. A "Y" in the first column indicates that the
	 *  parameter is actually used in netlist.
	 *
	 * | NL? |Name  |                                                            Description|Units  |Default   |Example          |
	 * |:---:|------|-----------------------------------------------------------------------|-------|---------:|----------------:|
	 * |  Y  |Vto   | Zero-bias threshold voltage                                           | V     | 0        | 1               |
	 * |  Y  |Kp    | Transconductance parameter                                            | A/V²  | 0.00002  | 0.00003         |
	 * |  Y  |Gamma | Bulk threshold parameter                                              | V^½   | 0        | 0.37            |
	 * |  Y  |Phi   | Surface inversion potential                                           | V     | 0.6      | 0.65            |
	 * |  Y  |Lambda| Channel-length modulation (level 1 and 2 only)                        | 1/V   | 0        | 0.02            |
	 * |     |Rd    | Drain ohmic resistance                                                |W|0|1|
	 * |     |Rs    | Source ohmic resistance                                               |W|0|1|
	 * |     |Cbd   | Zero-bias B-D junction capacitance                                    |F|0|20f|
	 * |     |Cbs   | Zero-bias B-S junction capacitance                                    |F|0|20f|
	 * |  Y  |Is    | Bulk junction saturation current                                      |A|0.00000000000001|1E-015|
	 * |  Y  |N     | Bulk diode emission coefficient                                       |-|1|*
	 * |     |Pb    | Bulk junction potential                                               |V|0.8|0.87|8|
	 * |     |Cgso  | Gate-source overlap capacitance per meter channel width               |F/m|0|0.00000000004|
	 * |     |Cgdo  | Gate-drain overlap capacitance per meter channel width                |F/m|0|0.00000000004|*
	 * |     |Cgbo  | Gate-bulk overlap capacitance per meter channel width                 |F/m|0|0.0000000002|*
	 * |     |Rsh   | Drain and source diffusion sheet resistance                           |W|0|10|*
	 * |     |Cj    | Zero-bias bulk junction bottom capacitance per square meter of junction area|F/m²|0|0.0002|*
	 * |     |Mj    | Bulk junction bottom grading coefficient                              |-|0.5|0.5|*
	 * |     |Cjsw  | Zero-bias bulk junction sidewall capacitance per meter of junction perimeter|F/m|0|1p|*
	 * |     |Mjsw  | Bulk junction sidewall grading coefficient                            |-|.50 level 1 	.33 level 2,3||
	 * |     |Js    | Bulk junction saturation current per square-meter of junction area|A/m|0|0.00000001|
	 * |  Y  |Tox   | Oxide thickness                                                       |m|0.0000001|0.0000001|
	 * |  Y  |Nsub  | Substrate doping                                                      |1/cm³|0|4000000000000000|
	 * |     |Nss   | Surface state density                                                 |1/cm²|0|10000000000|
	 * |     |Nfs   | Fast surface state                                                    |1/cm²|0|10000000000|*
	 * |     |TPG   | Type of gate material:  +1 opp. to substrate -1 same as substrate 	0 Al gate|-|1|
	 * |     |Xj    | Metallurgical junction depth                                          |m|0|1µ|*
	 * |  Y  |Ld    | Lateral diffusion                                                     |m|0|0.8µ|
	 * |  Y  |Uo    | Surface mobility                                                      |cm²/V/s|600|700|
	 * |     |Ucrit | Critical field for mobility degradation (level 2 only)                |V/cm|10000|10000|
	 * |     |Uexp  | Critical field exponent in mobility degradation (level 2 only)        |-|0|0.1|
	 * |     |Utra  | Transverse field coefficient (level 2 only)                           |-|0|0.3|*
	 * |     |Vmax  | Maximum carrier drift velocity (levels 2 & 3 only)                    |m/s|0|50000|
	 * |     |Neff  | Total channel-charge exponent (level 2 only)                          |-|1|5|
	 * |     |Kf    | Flicker noise coefficient                                             |-|0|1E-026|
	 * |     |Af    | Flicker noise exponent                                                |-|1|1.2|
	 * |     |Fc    | Coefficient for forward-bias depletion capacitance formula            |-|0.5|
	 * |     |Delta | Width effect on threshold voltage(levels 2 and 3)                     |-|0|1|
	 * |     |Theta | Mobility modulation (level 3 only)                                    |-|0|0.1|
	 * |     |Eta   | Static feedback (level 3 only)                                        |-|0|1|
	 * |     |Kappa | Saturation field (level 3 only)                                       |0.2|0.5|
	 * |     |Tnom  | Parameter measurement temperature                                     |ºC|27|50||
	 * |  Y  |L     | Length scaling                                                        |-|1.0||
	 * |  Y  |W     | Width scaling                                                         |-|1.0||
	 * */

	class fet_model_t : public param_model_t
	{
	public:
		fet_model_t(device_t &device, const pstring &name, const pstring &val)
		: param_model_t(device, name, val)
		, m_VTO(*this,  "VTO")
		, m_N(*this,  "N")
		, m_ISS(*this,  "IS")  // Haven't seen a model using ISS / ISD
		, m_ISD(*this,  "IS")
		, m_LD(*this,  "LD")
		, m_L(*this, "L")
		, m_W(*this, "W")
		, m_TOX(*this, "TOX")
		, m_KP(*this, "KP")
		, m_UO(*this, "UO")
		, m_PHI(*this, "PHI")
		, m_NSUB(*this, "NSUB")
		, m_GAMMA(*this, "GAMMA")
		, m_LAMBDA(*this, "LAMBDA")
		, m_RD(*this, "RD")
		, m_RS(*this, "RS")
		{}

		value_t m_VTO; //!< Threshold voltage [V]
		value_t m_N;   //!< Bulk diode emission coefficient
		value_t m_ISS;  //!< Body diode saturation current
		value_t m_ISD;  //!< Body diode saturation current
		value_t m_LD;  //!< Lateral diffusion [m]
		value_t m_L;   //!< Length scaling
		value_t m_W;   //!< Width scaling
		value_t m_TOX; //!< Oxide thickness
		value_t m_KP;  //!< Transconductance parameter [A/V²]
		value_t m_UO;  //!< Surface mobility [cm²/V/s]
		value_t m_PHI; //!< Surface inversion potential [V]
		value_t m_NSUB;//!< Substrate doping [1/cm³]
		value_t m_GAMMA; //!< Bulk threshold parameter [V^½]
		value_t m_LAMBDA; //!< Channel-length modulation [1/V]
		value_t m_RD;  //!< Drain ohmic resistance
		value_t m_RS;  //!< Source ohmic resistance
	};

	// Have a common start for mosfets

	NETLIB_OBJECT(FET)
	{
	public:
		enum q_type {
			FET_NMOS,
			FET_PMOS
		};

		NETLIB_CONSTRUCTOR(FET)
		, m_model(*this, "MODEL", "NMOS")
		, m_qtype(FET_NMOS)
		{
		}

		NETLIB_IS_DYNAMIC(true)

		//NETLIB_RESETI();
		NETLIB_UPDATEI() { }

		q_type qtype() const { return m_qtype; }
		bool is_qtype(q_type atype) const { return m_qtype == atype; }
		void set_qtype(q_type atype) { m_qtype = atype; }
	protected:

		fet_model_t m_model;
	private:
		q_type m_qtype;
	};

	// -----------------------------------------------------------------------------
	// nld_QBJT_EB
	// -----------------------------------------------------------------------------


	NETLIB_OBJECT_DERIVED(MOSFET, FET)
	{
	public:
		NETLIB_CONSTRUCTOR_DERIVED(MOSFET, FET)
		, m_DG(*this, "m_DG", true)
		, m_SG(*this, "m_SG", true)
		, m_SD(*this, "m_SD", true)
		, m_D_BD(*this, "m_D_BD")
#if (!BODY_CONNECTED_TO_SOURCE)
		, m_D_BS(*this, "m_D_BS")
#endif
		, m_phi(0.0)
		, m_gamma(0.0)
		, m_vto(0.0)
		, m_beta(0.0)
		, m_lambda(0.0)
		, m_Leff(0.0)
		, m_Cox(0.0)
	{
			register_subalias("S", m_SG.m_P);   // Source
			register_subalias("G", m_SG.m_N);   // Gate

			register_subalias("D", m_DG.m_P);   // Drain

			connect(m_SG.m_P, m_SD.m_P);
			connect(m_SG.m_N, m_DG.m_N);
			connect(m_DG.m_P, m_SD.m_N);

#if 0
			if (m_model.m_CJE > 0.0)
			{
				create_and_register_subdevice("m_CJE", m_CJE);
				connect("B", "m_CJE.1");
				connect("E", "m_CJE.2");
			}
			if (m_model.m_CJC > 0.0)
			{
				create_and_register_subdevice("m_CJC", m_CJC);
				connect("B", "m_CJC.1");
				connect("C", "m_CJC.2");
			}
#endif
		}

	protected:

		NETLIB_RESETI();
		NETLIB_UPDATEI();
		NETLIB_UPDATE_PARAMI();
		NETLIB_UPDATE_TERMINALSI();

	private:

		nld_twoterm m_DG;
		nld_twoterm m_SG;
		nld_twoterm m_SD;

		generic_diode<diode_e::MOS> m_D_BD;
#if (!BODY_CONNECTED_TO_SOURCE)
		generic_diode<diode_e::MOS> m_D_BS;
#endif

		nl_double m_phi;
		nl_double m_gamma;
		nl_double m_vto;
		nl_double m_beta;
		nl_double m_lambda;

		/* used in capacitance calculation */
		nl_double m_Leff;
		nl_double m_Cox;

		//NETLIB_SUBXX(analog, C) m_CJE;
		//NETLIB_SUBXX(analog, C) m_CJC;
	};



	// ----------------------------------------------------------------------------------------
	// nld_Q - Ebers Moll
	// ----------------------------------------------------------------------------------------


	NETLIB_UPDATE(MOSFET)
	{
		if (!m_SG.m_P.net().isRailNet())
			m_SG.m_P.solve_now();   // Basis
		else if (!m_SG.m_N.net().isRailNet())
			m_SG.m_N.solve_now();   // Emitter
		else
			m_DG.m_N.solve_now();   // Collector
	}

	NETLIB_RESET(MOSFET)
	{
		NETLIB_NAME(FET)::reset();
#if 0
		if (m_CJE)
		{
			m_CJE->reset();
			m_CJE->m_C.setTo(m_model.m_CJE);
		}
		if (m_CJC)
		{
			m_CJC->reset();
			m_CJC->m_C.setTo(m_model.m_CJC);
		}
#endif
	}

	NETLIB_UPDATE_TERMINALS(MOSFET)
	{
		const nl_double polarity = (qtype() == FET_NMOS ? 1.0 : -1.0);

		const nl_double Ugd = -m_DG.deltaV() * polarity; // Gate - Drain
		const nl_double Ugs = -m_SG.deltaV() * polarity; // Gate - Source
		const nl_double Ubs = 0.0;                       // Bulk - Source == 0 if connected
		const nl_double Ubd = m_SD.deltaV() * polarity;  // Bulk - Drain = Source  - Drain
		const nl_double Uds = Ugs - Ugd;

#if (!BODY_CONNECTED_TO_SOURCE)
		m_D_BS.update_diode(Ubs);
#endif
		m_D_BD.update_diode(Ubd);

		// Are we in forward mode ?
		const bool is_forward = Uds >= 0;

		// calculate Vth
		const nl_double Vbulk = is_forward ? Ubs : Ubd;
		const nl_double phi_m_Vbulk = (m_phi > Vbulk) ? std::sqrt(m_phi - Vbulk) : 0.0;
		const nl_double Vth = m_vto * polarity + m_gamma * (phi_m_Vbulk - std::sqrt(m_phi));

		const nl_double Vctrl = (is_forward ? Ugs : Ugd) - Vth;

		nl_double Ids, gm, gds, gmb;

		if (Vctrl <= 0.0)
		{
			// cutoff region
		    Ids = 0.0;
		    gm  = 0.0;
		    gds = 0.0;
		    gmb = 0.0;
		}
		else
		{
			const nl_double Vds = std::abs(Uds);
		    const nl_double b   = m_beta * (1.0 + m_lambda * Vds);
		    if (Vctrl <= Vds)
		    {
			    // saturation region
		    	Ids = b * Vctrl * Vctrl / 2.0;
		    	gm  = b * Vctrl;
		    	gds = m_lambda * m_beta * Vctrl * Vctrl / 2.0;
		    }
		    else
		    {
			    // linear region
		    	Ids = b * Vds * (Vctrl - Vds / 2);
		    	gm  = b * Vds;
		    	gds = b * (Vctrl - Vds) + m_lambda * m_beta * Vds * (Vctrl - Vds / 2.0);
		    }

			// backgate transconductance
			const nl_double bgtc = (phi_m_Vbulk != 0.0) ? (m_gamma / phi_m_Vbulk / 2.0) : 0.0;
		    gmb = gm * bgtc;
		}

		// FIXME: these are needed to compute capacitance
		// nl_double Udsat = pol * std::max (Utst, 0.0);
		// Uon = pol * Vth;

		// compute bulk diode equivalent currents

		const nl_double IeqBD = m_D_BD.Ieq();
		const nl_double gbd = m_D_BD.G();
#if 0
		const nl_double IeqBS = m_D_BS.Ieq();
		const nl_double gbs = m_D_BS.G();
#else
		const nl_double IeqBS = 0.0;
		const nl_double gbs = 0.0;
#endif
		// exchange controlling nodes if necessary
		const nl_double gsource = is_forward ? (gm + gmb) : 0;
		const nl_double gdrain  = is_forward ?   0.0 : (gm + gmb);

		const nl_double IeqDS = (is_forward) ?
			   Ids - gm * Ugs - gmb * Ubs - gds * Uds
			: -Ids - gm * Ugd - gmb * Ubd - gds * Uds;

		// IG = 0
		const nl_double IG = 0.0;
		const nl_double ID = (+IeqBD - IeqDS) * polarity;
		const nl_double IS = (+IeqBS + IeqDS) * polarity;
		const nl_double IB = (-IeqBD - IeqBS) * polarity;

		const nl_double gGG = 0.0; // ok
		const nl_double gGD = 0.0; // ok
		const nl_double gGS = 0.0; // ok
		const nl_double gGB = 0.0; // ok

		const nl_double gDG =  gm; // ok
		const nl_double gDD =  gds + gbd - gdrain; // ok
		const nl_double gDS = -gds - gsource; // ok
		const nl_double gDB =  gmb - gbd; // ok

		const nl_double gSG = -gm; // ok
		const nl_double gSD = -gds + gdrain; // ok
		const nl_double gSS =  gbs + gds + gsource;  // ok
		const nl_double gSB = -gbs - gmb;

		const nl_double gBG =  0.0; // ok
		const nl_double gBD = -gbd; // ok
		const nl_double gBS = -gbs;
		const nl_double gBB =  gbs + gbd; // ok

		// Source connected to body, Diode S-B shorted!
		const nl_double gSSBB = gSS + gBB + gBS + gSB;

		//                 S          G
		m_SG.set_mat(    gSSBB,   gSG + gBG, +(IS + IB),       // S
					   gGS + gGB,    gGG,      IG       );     // G
		//                 D          G
		m_DG.set_mat(     gDD,       gDG,    +ID,              // D
					      gGD,       0.0,    0.0        );     // G
		//                 S          D
		m_SD.set_mat(     0.0,    gSD + gBD,  0.0,             // S
					   gDS + gDB,    0.0,     0.0);            // D

	}


	NETLIB_UPDATE_PARAM(MOSFET)
	{
		set_qtype((m_model.model_type() == "NMOS") ? FET_NMOS : FET_PMOS);

		/*
		 * From http://ltwiki.org/LTspiceHelp/LTspiceHelp/M_MOSFET.htm :
		 *
		 *		VTO, KP, LAMBDA, PHI and GAMMA. These parameters are computed
		 *		if the process parameters(NSUB, TOX,...) are given, but
		 *		user-specified values always override.
		 *
		 *	But couldn't find a formula for lambda anywhere
		 *
		 */

		m_lambda = m_model.m_LAMBDA; // FIXME: m_lambda only set once

		// calculate effective channel length
		m_Leff = m_model.m_L - 2 * m_model.m_LD;
		nl_assert_always(m_Leff > 0.0, "Effective Lateral diffusion would be negative for model " + m_model.name());
		if (m_model.m_TOX > 0.0)
			m_Cox = (constants::eps_SiO2() * constants::eps_0() / m_model.m_TOX);
		else
			m_Cox = 0.0;

		// calculate DC transconductance coefficient
		if (m_model.m_KP > 0)
			m_beta = m_model.m_KP * m_model.m_W / m_Leff;
		else if (m_Cox > 0 && m_model.m_UO > 0)
			m_beta = m_model.m_UO * 1e-4 * m_Cox * m_model.m_W / m_Leff;
		else
			m_beta = 2e-5 * m_model.m_W / m_Leff;

		// Bulk diodes

		m_D_BD.set_param(m_model.m_ISD, m_model.m_N, exec().gmin(), constants::T0());
#if (!BODY_CONNECTED_TO_SOURCE)
		m_D_BS.set_param(m_model.m_ISS, m_model.m_N, exec().gmin(), constants::T0());
#endif

		//FIXME::UT can disappear
		const double Vt = constants::T0() * constants::k_b() / constants::Q_e();

		// calculate surface potential if not given

		if (m_model.m_PHI > 0.0)
			m_phi = m_model.m_PHI;
		else if (m_model.m_NSUB > 0.0)
		{
			nl_assert_always(m_model.m_NSUB * 1e6 >= constants::NiSi(), "Error calculating phi for model " + m_model.name());
			m_phi = 2 * Vt * std::log (m_model.m_NSUB * 1e6 / constants::NiSi());
		}
		else
			m_phi = 0.6;

		// calculate bulk threshold if not given
		if (m_model.m_GAMMA > 0.0)
			m_gamma = m_model.m_GAMMA;
		else
		{
			if (m_Cox > 0 && m_model.m_NSUB > 0)
				m_gamma = std::sqrt (2.0 * constants::Q_e() * constants::eps_Si() * constants::eps_0() * m_model.m_NSUB * 1e6) / m_Cox;
			else
				m_gamma = 0.0;
		}

		m_vto = m_model.m_VTO;
		nl_assert_always(m_vto != 0.0, "Threshold voltage not specified for " + m_model.name());

		/* FIXME: VTO if missing may be calculated from TPG, NSS and temperature. Usually models
		 * specify VTO so skip this here.
		 */

		m_Cox = m_Cox * m_model.m_W * m_Leff;

	}

} // namespace analog

namespace devices {
	NETLIB_DEVICE_IMPL_NS(analog, MOSFET, "MOSFET", "MODEL")
} // namespace devices

} // namespace netlist