JFET and MESFET Temperature Equations

Temperature Parameters (LEVELs 1, 2, and 3) lists temperature effect parameters. The temperature effect parameters apply to LEVELs 1, 2, and 3. They include temperature parameters for the effect of temperature on resistance, capacitance, energy gap, and a number of other model parameters. The temperature equation selectors, TLEV and TLEVC, select different temperature equations for the calculation of energy gap, saturation current, and gate capacitance. TLEV is either 0, 1, or 2 while TLEVC is either 0, 1, 2, or 3.

Table 17-4: Temperature Parameters (LEVELs 1, 2, and 3)
Function	Parameter
capacitance	CTD, CTS
DC	M, TCV, XTI
energy gap	EG, GAP1, GAP2
equation selections	TLEV, TLEVC
grading	M
mobility	BEX
resistance	TRD, TRS

Temperature Effect Parameters

Name (Alias)	Units	Default	Description
BETATCE	1/°	0.0	Beta temperature coefficient for TriQuint model
BEX		0.0	Mobility temperature exponent, correction for low field mobility
CTD	1/°	0.0	Temperature coefficient for gate-drain junction capacitance. TLEVC=1 enables CTD to override the default temperature compensation.
CTS	1/°	0.0	Temperature coefficient for gate-source junction capacitance. TLEVC=1 enables CTS to override the default temperature compensation.
EG	eV	1.16	Energy gap for the gate to drain and gate to source diodes at 0 °K 1.17 - silicon 0.69 - Schottky barrier diode 0.67 - germanium 1.52 - gallium arsenide
GAP1	eV/°	7.02e-4	First bandgap correction factor, from Sze, alpha term 7.02e-4 - silicon 4.73e-4 - silicon 4.56e-4 - germanium 5.41e-4 - gallium arsenide
GAP2	x	1108	Second bandgap correction factor, from Sze, beta term 1108 - silicon 636 - silicon 210 - germanium 204 - gallium arsenide
M (MJ)		0.50	Grading coefficient for gate-drain and gate-source diodes 0.50 - step junction 0.33 - linear graded junction
N		1.0	Emission coefficient for gate-drain and gate-source diodes
TCV (VTOTC)	1/°	0.0	Temperature compensation coefficient for VTO (threshold voltage)
TLEV		0.0	Temperature equation selector for junction diodes. Interacts with the TLEVC parameter.
TLEVC		0.0	Temperature equation selector for junction capacitances and potential. Interacts with the TLEV parameter.
TPB	V/°	0.0	Temperature coefficient for PB. TLEVC=1 or 2 overrides the default temperature compensation.
TRD (TDR1)	1/°	0.0	Temperature coefficient for drain resistance
TRG (TRG1)	1/°	0	Temperature coefficient for gate resistance
TRS (TRS1)	1/°	0.0	Temperature coefficient for source resistance
XTI		0.0	Saturation current temperature exponent XTI=3 for silicon diffused junction or XTI=2 for Schottky barrier diode

Temperature Compensation Equations

Energy Gap Temperature Equations

To determine energy gap for temperature compensation, use the equation:

TLEV = 0 or 1

TLEV = 2

Saturation Current Temperature Equations

The saturation current of the gate junctions of the JFET varies with temperature according to the equation:

TLEV=0 or 1

TLEV=2

Gate Capacitance Temperature Equations

There are temperature equations for the calculation of gate capacitances. The parameters CTS and CTD are the linear coefficients. If the TLEVC is set to zero, the SPICE equations are used. To achieve a zero capacitance variation, set the coefficients to a very small value such as 1e-6 and TLEVC=1 or 2.