Micro-Cap v7.1.6 / RM

Both the original group of SPICE2 model levels 1, 2, and 3 and a BSIM group of models are supported. The BSIM models are supported as levels 4, 5, and 8. Level 4 is the original BSIM1 model. Level 2 is the improved BSIM2 model. Level 8 is the BSIM3 model version 3.3.2, derived from the UC Berkeley code dated 9/ 7/99. Levels 6 and 7 are not used.

<width> and <length> are the drawn device dimensions, before side diffusion, in meters. They can be specified in a circuit, or in a .MODEL or .OPTIONS statement. W and L VALUE attribute values supersede those in the .MODEL statement, which supersede those in the .OPTIONS statement.

The initialization [IC=<vds>[,vgs[,vbs]]] assigns initial voltages to the drainsource, gate-source, and body-source terms in transient analysis if no operating point is done (or if the UIC flag is set). The [OFF] keyword forces the device off during the first iteration of the DC operating point.

<sourceperiphery> and <drainperiphery> are the diffusion peripheries (m). <sourcearea> and <drainarea> are the diffusion areas (sq. m). Source and drain junction capacitances may be specified directly by the model parameters CBS and CBD. If absent, they are calculated from area and periphery terms.

The parasitic resistances may be specified directly with the model parameters RS, RD, RG, and RB. If unspecified, they are calculated from the product of the sheet resistivity, RSH, and the number of squares terms, <drainsquares>, <sourcesquares>, <gatesquares>, and <bulksquares>. If these terms are absent, or zero, and the model parameters RS, RD, RG, and RB are absent or zero, then the parasitic resistances are not included in the model.

<drainsquares> and <sourcesquares> default to 1.0. The other parameter line values default to zero. <width> and <length> default to DEFW and DEFL, defined in the Global Settings dialog box (SHIFT + CTRL + G).

<mval> is a multiplier (default = 1) that provides a way to simulate the effect of paralleling many devices. It multiplies the effective width, overlap, and junction capacitances, and the junction currents. It multiplies the drain and source areas, the device width, and the two peripheries, and divides the four resistances RS, RD, RG, and RB.

Model statement forms

.MODEL <model name> NMOS ([model parameters])

.MODEL <model name> PMOS ([model parameters])

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Model parameters for levels 1, 2, and 3

In addition to the 32 common parameters, the following table lists the additional parameters used in the level 1, 2, and 3 models.

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PBSW(T) = PBSW•(T/Tnom)- 3•VT•ln((T/Tnom))-EG(Tnom)•(T/Tnom)+EG(T)

PHI(T) = PHI•(T/Tnom)- 3•VT•ln((T/Tnom))-EG(Tnom)•(T/Tnom)+EG(T)

CBD(T) = CBD•(1+MJ•(.0004•(T-Tnom) + (1 - PB(T)/PB)))

CBS(T) = CBS•(1+MJ•(.0004•(T-Tnom) + (1 - PB(T)/PB)))

CJ(T) = CJ•(1+MJ•(.0004•(T-Tnom) + (1 - PB(T)/PB)))

CJSW(T) = CJSW•(1+MJ•(.0004•(T-Tnom) + (1 - PB(T)/PB))

The parasitic lead resistances have no temperature dependence.

Current equations

Only the Level 1 drain equations are shown here. The Level 2 and Level 3 current equations are too complex for presentation in this manual. Interested users should consult reference (2) for more information.

K = KP • W/ (L - 2 • LD)

VTH = VTO + GAMMA • ((PHI - VBS)1/2- √ (PHI))

Cutoff region: For Vgs < VT

Id = 0.0

Linear region: For Vgs > VTH and Vds < (Vgs - VTH)

Id = K•(Vgs - VTH - 0.5•Vds)•Vds•(1+LAMBDA•Vds)

Saturation region: For Vgs > VTH and Vds > (Vgs - VTH)

Id = 0.5•K•(Vgs - VTH)2•(1 + LAMBDA•Vds)

These equations are for an N-channel device.

Capacitance equations

Meyer model for gate capacitance

All levels use the SPICE 2G.6 capacitance model proposed by Meyer when XQC is specified or greater than 0.5. If XQC is specified and is less than or equal to .5, the Ward model is used. Meyer's model does not guarantee charge conservation, but is generally more robust than the Ward model.

The charges are modeled by three nonlinear capacitances, Cgb, Cgd, and Cgs.

Cox = COX • W • Leff

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If VBS ≤ FC • PBSW(T) then

f2(VBS) = 1/ (1 - VBS/PBSW(T))M Else

f2(VBS) = (1 - FC•(1+M)+M•(VBS/PBSW(T)))/ (1 - FC) (1-M)

If VBD ≤ FC • PB(T) then f1(VBD) = 1/(1 - VBD/PB(T))M

Else

f1(VBD) = (1 - FC•(1+M)+M•(VBS/PB(T)))/ (1 - FC) (1-M)

If VBD ≤ FC • PBSW(T) then

f2(VBD) = 1/ (1 - VBD/PBSW(T))M Else

f2(VBD) = (1 - FC•(1+M)+M•(VBD/PBSW(T)))/ (1 - FC) (1-M)

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Model parameters for level 4

These are the model parameters for the BSIM1 model, level 4. There are no default values. All parameter values must be specified.

Model parameters for level 4 (continued)

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