Ngspice implements many of the BSIM models developed by Berkeley's BSIM group. BSIM stands for Berkeley Short-Channel IGFET Model and groups a class of models that is continuously updated. BSIM3 (11.2.10) and BSIM4 (11.2.11) are industry standards for CMOS processes down to 0.15 µm (BSIM3) and below (BSIM4), are very stable and are supported by model parameter sets from foundries all over the world. BSIM1 and BSIM2 are obsolete today.

In general, all parameters of BSIM models are obtained from process characterization, in particular level 4 and level 5 (BSIM1 and BSIM2) parameters can be generated automatically. J. Pierret [4] describes a means of generating a `process' file, and the program ngproc2mod provided with ngspice converts this file into a sequence of BSIM1 .model lines suitable for inclusion in an ngspice input file.

Parameters marked below with an * in the l/w column also have corresponding parameters with a length and width dependency. For example, vfb is the basic parameter with units of Volts, and lvfb and wvfb also exist and have units of Volt-meter.

The formula

[\begin{array}{ll} {P = P_{0} + \frac{P_{L}}{L_{\lbrack font\ rm\ \lbrack char\ e\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\lbrack char\ c\ mathalpha\rbrack\lbrack char\ t\ mathalpha\rbrack\lbrack char\ i\ mathalpha\rbrack\lbrack char\ v\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\rbrack}} + \frac{P_{W}}{W_{\lbrack font\ rm\ \lbrack char\ e\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\lbrack char\ c\ mathalpha\rbrack\lbrack char\ t\ mathalpha\rbrack\lbrack char\ i\ mathalpha\rbrack\lbrack char\ v\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\rbrack}}} & \ \end{array}]

is used to evaluate the parameter for the actual device specified with

[\begin{array}{ll} {L_{\lbrack font\ rm\ \lbrack char\ e\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\lbrack char\ c\ mathalpha\rbrack\lbrack char\ t\ mathalpha\rbrack\lbrack char\ i\ mathalpha\rbrack\lbrack char\ v\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\rbrack} = L_{\lbrack font\ rm\ \lbrack char\ i\ mathalpha\rbrack\lbrack char\ n\ mathalpha\rbrack\lbrack char\ p\ mathalpha\rbrack\lbrack char\ u\ mathalpha\rbrack\lbrack char\ t\ mathalpha\rbrack\rbrack} - DL} & \ \end{array}]

[\begin{array}{ll} {W_{\lbrack font\ rm\ \lbrack char\ e\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ f\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\lbrack char\ c\ mathalpha\rbrack\lbrack char\ t\ mathalpha\rbrack\lbrack char\ i\ mathalpha\rbrack\lbrack char\ v\ mathalpha\rbrack\lbrack char\ e\ mathalpha\rbrack\rbrack} = W_{\lbrack font\ rm\ \lbrack char\ i\ mathalpha\rbrack\lbrack char\ n\ mathalpha\rbrack\lbrack char\ p\ mathalpha\rbrack\lbrack char\ u\ mathalpha\rbrack\lbrack char\ t\ mathalpha\rbrack\rbrack} - DW} & \ \end{array}]

Note that unlike the other models in ngspice, the BSIM models are designed for use with a process characterization system that provides all the parameters, thus there are no defaults for the parameters, and leaving one out is considered an error. For an example set of parameters and the format of a process file, see the SPICE2 implementation notes [3]. For more information on BSIM2, see reference [5]. BSIM3 (11.2.10) and BSIM4 (11.2.11) represent state of the art for submicron and deep submicron IC design.