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NMOS

Simple NMOS Transistor

 

Description

Equations

Variables

Connections

Parameters

Modelica Standard Library

Description

The NMOS component is a simple model of an n-channel metal-oxide semiconductor FET. The model does not contain capacitances. A large drain-source resistance, RDS, is included to avoid numerical difficulties.

An optional heat port may be connected to a heatsink, however, the electrical parameters are not temperature dependent.

On-Resistance

When used as a switch, the on-resistance of the transistor is approximately

Ron1βW/LvGSVT

where vGS is the applied gate-to-source voltage.

Because the default parameter values yield a relatively high on-resistance. the product βW/L should be increased by several orders of magnitude when using this device in a high-power application.

Equations

iB=iG=0

iD&equals;iS&equals;{iDvD<vSiDotherwise

iD&equals;uDSgDS&plus;{0uGST0vuDSuGST12uDSuDS<uGST12vuGST2otherwise

gDS&equals;{1RsmallRsmall<RDS<Rsmall1RDSotherwise

uBS&equals;{0uS<vBvBuSotherwise

uD&equals;{vSvD<vSvDotherwise

uDS&equals;uDuS

uGST&equals;K2uBS&plus;vGVTuSK5

uS&equals;{vDvD<vSvSotherwise

v&equals;βW&plus;dWL&plus;dL

Tint&equals;{TheatPortUse Heat PortTotherwise

LossPower&equals;iDvDvS

Variables

Name

Units

Description

Modelica ID

LossPower

W

Loss power leaving component via HeatPort

LossPower

TheatPort

K

Temperature of HeatPort

T_heatPort

Connections

Name

Description

Modelica ID

D

Drain

D

G

Gate

G

S

Source

S

B

Bulk

B

Heat Port

Conditional heat port

heatPort

Parameters

Name

Default

Units

Description

Modelica ID

W

2·10−5

m

Width of channel

W

L

6·10−6

m

Length of channel

L

β

4.1·10−5

AV2

Transconductance parameter

Beta

VT

0.8

V

Zero bias threshold voltage

Vt

K2

1.144

1

Bulk threshold parameter

K2

K5

0.7311

1

Reduction of pinch-off region

K5

dW

−2.5·10−6

m

Narrowing of channel

dW

dL

−1.5·10−6

m

Shortening of channel

dL

RDS

1·107

Ω

Drain-Source resistance

RDS

T

293.15

K

Fixed device temperature if the Use Heat Port parameter is set to false

T

Use Heat Port

false

 

True (checked) means heat port is enabled

useHeatPort

Modelica Standard Library

The component described in this topic is from the Modelica Standard Library. To view the original documentation, which includes author and copyright information, click here.

See Also

Analog Components

Electrical Library

MOSFET Transistors