Junction FET
In this topic:
Netlist Entry
Jxxxx drain gate source modelname [area] [OFF] [IC=vds,vgs] + [TEMP=local_temp] [M=mult] [DTEMP=dtemp]
| drain | Drain node |
| gate | Gate node |
| source | Source node |
| modelname | Name of model defined in a .model statement. Must begin with a letter but can contain any character except whitespace and period '.'. |
| area | Area multiplying factor. Area scales up the device. E.g. an area of 3 would make the device behave like 3 transistors in parallel. Default is 1. |
| OFF | Instructs simulator to calculate operating point analysis with device initially off. This is used in latching circuits such as thyristors and bistables to induce a particular state. See .OP for more details. |
| vds,vgs | Initial conditions for drain-source and gate-source junctions respectively. These only have an effect if the UIC parameter is specified on the .TRAN statement. |
| local_temp | Local temperature. Overrides specification in .OPTIONS or .TEMP statements. |
| mult | Device multiplier. Equivalent to putting mult devices in parallel. |
| dtemp | Differential temperature. Similar to local_temp but is specified relative to circuit temperature. If both TEMP and DTEMP are specified, TEMP takes precedence. |
N Channel JFET: Model Syntax
.model modelname NJF ( parameters )
P Channel JFET: Model Syntax
.model modelname PJF ( parameters )
JFET: Model Parameters
The symbols '???MATH???\times???MATH???' and '???MATH???\div???MATH???' in the Area column means that parameter should be multiplied or divided by the area factor respectively.
| Name | Description | Units | Default | Area |
| VTO | Threshold voltage | V | -2.0 | |
| VTOTC | VTO temp coefficient | V/???MATH???°???MATH???C | 0 | |
| DVT0 | Linear DIBL parameter | 0 | ||
| DVT1 | Non-linear DIBL parameter | 0.0 | ||
| DVT2 | Non-linear DIBL parameter, minimum value 0.1 | 1.0 | ||
| DVTP | DIBL exponent parameter | 2.0 | ||
| BETA | Transconductance parameter | A/V2 | 1e-4 | ???MATH???\times???MATH??? |
| BETATCE | BETA temperature coefficient | % | 0 | |
| LAMDA | Channel length modulation parameter | 1/V | 0 | |
| ALPHA | Impact ionisation coefficient | 0 | ||
| VK | Impact ionisation knee voltage | V | 0 | |
| RS | Source ohmic resistance | ???MATH???\Omega???MATH??? | 0 | ???MATH???\div???MATH??? |
| CGS | Zero-bias G-S junction capacitance | F | 0 | ???MATH???\div???MATH??? |
| CGD | Zero-bias G-D junction capacitance | F | 0 | ???MATH???\div???MATH??? |
| M | Grading coefficient | 1.0 | ||
| PB | Gate junction potential | V | 1 | |
| IS | Gate junction saturation current | A | 1e-14 | ???MATH???\times???MATH??? |
| N | Gate junction emission coefficient | 1 | ||
| ISR | Recombination current | 0 | ||
| NR | ISR emission coefficient | |||
| XTI | IS temperature coefficient | 3 | ||
| KF | Flicker noise coefficient | 0 | ||
| AF | Flicker noise exponent | 1 | ||
| FC | Coefficient for forward bias depletion capacitance | 0.5 | ||
| NLEV | Select noise model | 2 | ||
| GDSNOI | Channel noise coefficient. Use with NLEV=3 | 1.0 | ||
| TNOM, T_MEASURED | Reference temperature; the temperature at which the model parameters were measured | ???MATH???°???MATH???C | 27 | |
| T_ABS | If specified, defines the absolute model temperature overriding the global temperature defined using .TEMP | ???MATH???°???MATH???C | - | |
| T_REL_GLOBAL | Offsets global temperature defined using .TEMP. Overridden by T_ABS | ???MATH???°???MATH???C | 0.0 |
DIBL Equations
The parameters DVT0, DVT1, DVT2 and DVTP are non-standard. These accommodate drain-induced barrier lowering (DIBL) and modify the threshold voltage with Vds as follows:
\[ V_{th} = VTO - DVTO*V_{ds} - \frac{DVT1}{(DVT2+V_{ds})^{DVTP}} \]
Examples
Q2 is a U430 with a local temperature of 100???MATH???°???MATH???C.
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