The AREA and M Element parameters, together with the SCALE and SCALM control options, control scaling. For all three model levels, the model parameters IS, CGD, CGS, RD, RS, BETA, LDEL, and WDEL, are scaled using the same equations.
Scaled parameters A, L, W, LDEL, and WDEL, are affected by option SCALM. SCALM defaults to 1.0. To enter the parameter W with units in microns, for example, set SCALM to 1e-6, then enter W=5; Star-Hspice sets W=5e-6 meters, or 5 microns.
Override global scaling that uses the .OPTION SCALM=<val> statement in a JFET or MESFET model by including SCALM=<val> in the .MODEL statement.
The direction of current flow through the JFET is assumed in JFET Current Convention, N-Channel. You can use either I(Jxxx) or I1(Jxxx) syntax when printing the drain current. I2 references the gate current and I3 references the source current. Jxxx is the device name. JFET Current Convention, N-Channel represents the Star-Hspice current convention for an n channel JFET.
For a p-channel device, the following must be reversed:
Star-Hspice uses three equivalent circuits in the analysis of JFETs: transient, AC, and noise circuits. The components of these circuits form the basis for all element and model equation discussion.
The fundamental component in the equivalent circuit is the drain to source current (ids). For noise and AC analyses, the actual ids current is not used. Instead, the partial derivatives of ids with respect to the terminal voltages, vgs, and vds are used.
The names for these partial derivatives are:
The ids equation accounts for all DC currents of the JFET. The gate capacitances are assumed to account for transient currents of the JFET equations. The two diodes shown in JFET/MESFET Transient Analysis are modeled by these ideal diode equations:
|
Nominal temperature of parameter measurements in °K (user-input in °C). Tnom = 273.15 + TNOM |
|
