The model of the MESFET is identified by the type specifier NMF or PMF.

.MODEL <model name> NMF [model parameters]
.MODEL <model name> PMF [model parameters]

The MESFET model is derived from the GaAs FET model of Statz et al. The dc characteristics are defined by the parameters VTO, B, and BETA, which determine the variation of drain current with gate voltage, ALPHA, which determines saturation voltage, and LAMBDA, which determines the output conductance.

Two ohmic resistances, RD and RS, are included. Charge storage is modeled by total gate charge as a function of gate-drain and gate-source voltages and is defined by the parameters CGS, CGD, and PB.


Parameter Description Default Units Area
VTO pinch-off voltage -2.0 V  
BETA transconductance parameter 10-4 A/V2 *
B doping tail extending parameter 0.3  1/V *
ALPHA saturation voltage parameter 2.0 1/V *
LAMBDA channel-length modulation parameter 0 1/V  
RD drain ohmic resistance 0 Ω *
RS source ohmic resistance 0 Ω *
CGS zero-bias G-S junction capacitance 0 F *
CGD zero-bias G-D junction capacitance 0 F *
PB gate junction potential 1 V  
KF flicker noise coefficient 0    
AF flicker noise exponent 1    
FC coefficient for forward-bias depletion capacitance formula 0.5    


.MODEL ZMOD PMF ( VTO=-3 RD=20 RS=20  )

See also