Module 6.1 -FETs

Field-Effect Transistor

FET stands for _

Julius Edgar Lilienfeld

Who filed the first patent for the FET principle?

October 22, 1925

When was the first FET patent filed in Canada?

Oskar Heil

Who patented another FET in 1934?

electric field

FET controls conductivity of a channel using a(n) _

unipolar

FETs are _ devices (one type of charge carrier)

voltage-controlled

FETs are _ semiconductor devices

gate and source

The flow of majority carriers is influenced by voltage across _ terminals

faster

FETs are generally _ than BJTs when switching on and off

no stored charge

FETs switch faster because _ needs to be removed from the junction

no offset value

FET has _ when used as a switch

100 MΩ

FET has extremely high input impedance of typically _

high impedance

FETs are preferred in circuits requiring _

radiation, temperature

FET is relatively immune to _ and _ variations

silicon dioxide (SiO2)

FET makes use of insulating material _

greater thermal stability

FET can be operated to provide _ than BJT

less noisy, smaller

FET is _ than BJT
FET is _ than BJT in size

smaller gain-bandwidth, electrostatic discharge

FET has _ than BJT
FET has greater susceptibility to damage in _

JFET, MOSFET, MESFET

The three types of Field-Effect Transistors are _

Junction Field-Effect Transistor

JFET stands for _

Metal Oxide Semiconductor FET

MOSFET stands for _

Metal-Semiconductor FET

MESFET stands for _

Depletion MOSFET, Enhancement MOSFET

The two subtypes of MOSFET are _

three-terminal device

JFET is a _ containing one basic pn junction

source, gate, drain

The three terminals of a JFET are _

reverse-biased PN junction

JFET operates with a _ to control current in a channel

n-channel, p-channel

JFETs fall into two categories: _

depletion region

The gate junction creates a _ that narrows the channel

VGS = 0 V

IDSS is always specified when _

VDS = VP

Pinch-off occurs when _

VGS < 0 V

Channel is narrowed further when _

gate-source voltage

VGS is the bias voltage that controls _ of the channel

drain current

ID is the amount of majority carriers flowing out of the _

drain-source voltage

VDS is the bias voltage that causes majority carriers to _

IDSS

Maximum drain current when VGS = 0 V is called _

maximum current, VGS = 0 V

IDSS is the _ a JFET can produce, always specified at _

pinch-off voltage

VP is the value of VDS at which drain current becomes constant, called _

VGS = 0 V

Pinch-off voltage VP is always measured at _

VGS(OFF)

The value of VGS that causes ID = 0 is called _

equal magnitude, opposite sign

VGS(OFF) and VP are always _ but _

cutoff voltage

VGS(OFF) is also known as the _

ohmic region

When VGS = 0, JFET acts like a voltage-controlled resistor in the _

voltage-controlled resistor

In the ohmic region, JFET acts like a _

cutoff region

The region where VGS causes JFET to act as an open circuit is the _

maximum

In the cutoff region, channel resistance is at _

saturation region

The region where JFET is a good conductor controlled by VGS is the _

VGS

In the saturation region, JFET is controlled by _ while VDS has little effect

breakdown region

The region where VDS is high enough to cause uncontrolled current is the _

uncontrolled maximum current

Breakdown region causes the channel to pass _

Shockley's Equation

ID = IDSS[1 - VGS/VP]² is known as _

IDSS

When VGS = 0, Shockley's equation gives ID = _

0 A

When VGS = VP (cutoff), Shockley's equation gives ID = _

transfer curve

The plot of ID vs. VGS is called the _

VGS(off) = -VP

On the transfer curve, the x-intercept is at _

parabolic

The shape of the JFET transfer characteristic curve is _

drain characteristics

The transfer curve can be obtained from the _

PD = VDS × ID

The formula for power dissipated in a JFET is _

maximum allowable value

Power dissipated in a JFET must not exceed its _

increases

Maximum allowable power dissipation decreases as temperature _

derated

Maximum power must be _ as operating temperature increases

derating value

The _ is given in specification sheets

transconductance

gm is also called forward _ or transfer conductance

change in drain current

Transconductance gm measures _ for a given change in VGS

ΔID / ΔVGS

The basic formula for transconductance gm is _

VDS constant

gm is defined with _ held constant

(2IDSS/|VP|)[1 - VGS/VP]

The derived formula for gm in terms of IDSS and VP is _

gmo

Maximum transconductance when VGS = 0 is denoted as _

2IDSS / |VP|

The formula for maximum transconductance gmo is _

siemens (S)

The unit of transconductance gm is _