semiconductors

final test

JFET means

junction field-effect transister

what is a JFET

a voltage control device, the output characteristics of the device are controlled by its input voltage (not current)

the terminals of the FET are

Gate, Source, and Drain

the terminals of the FET are equivalent

Gate = BJT Base

Source = BJT emmiter

Drain = BJT collector

p-channel JFET

has a p-type channel and a n-type gate

n-channel JFET

has a n-type channel and a p-type gate

the n-channel JFET is normally used with _ while p-channel JFET is normally used with _

positive supply voltages, negative supply voltages

the current through a JFET is controlled by

varying the width of the channel

there are two ways to vary the width of the JFET channel

increasing Vds while holding Vgs constant or increasing Vgs while holding Vds constant

what is pinchoff voltage (vp)

value of drain-source voltage that causes drain current to reach its maximum value at a given value of Vgs

what is shorted-gate drain current (idss)

maximum possible value of drain current for a given JFET

Idss is always measured at Vgs= _ and Vds = _

vgs = 0v and vds = vp

Id is always less than or equal to

Idss

the gate-source junction of a JFET is what biased

reversed biased

as Vgs decreases, Id _

decreases

gate-source cutoff voltage (vgsoff) is the value of vgs that causes drain current to 

drop to zero

since the gate-source junction of a JFET is reversed bias, its gate input impedance is

extremely high

ability of a JFET to amplify is described as ___ and is merely the change in drain current divided by the change in gate voltage

transconductance

although voltage gain appears low in a JFET, it is almost

infinite

transconductance is indicated as Mhos or siemens and is typically what range for the MPFLOD trransisiter

2.5 mmhos - 7.5mmhos

the gate for a JFET is considered an __ and draws __ from the source

open circuit, no power

the main drawback for the metal oxide semiconductor JFET is 

that the JFET gate must be reversed biased for proper operation

why does the metal oxide semiconductor have to be reverse bias?

in order to delete the channel of free carriers, thus controlling the size of the channel

the type operation for a metal oxide semiconductor JFET is refered to as 

depletion-mode operation 

a depletion-type device would be one that used an input voltage to do what?

to reduce the size of the channel from its zero-bias size

the metal oxide semiconductor FET, or MOSFET is a device that can be operated in the _ this means that the input signal an be used to _ 

enhancement mode, increase the size of the channel

the metal oxide semiconductor FET, or MOSFET is not restricted to operating with _ which makes it a _ over the JFET

its gate reversed biased, improvement

MOSFETS are very sensitive to _ due to the _ 

static electricity, thin layer of silicon dioxide(SiO2) a glasslike material that is an insulator

there are two basic types of MOSFET, _ and _

Depletion-type MOSFET, caled D-MOSFET, Enhancement-type MOSFET called E-MOSFET

D-MOSFET can be operated in _ where E-MOSFET can operate in _

depletion mode and enhancement mode, only enhancemenet mode

D-MOSFET has a _ between source and drain

physical channel

E-MOSFET depends on the _ between the source and drain terminals

gate voltage to form a channel

when the mosfet gate-source junction is reversed biased (vgs is negative) the channel is effectively reduced its

width, while increasing its resistance (same as jfet)

in mosfet initial mode, Id will be less than Idss because resistance of the MOSFET channel is

higher when Vgs is negative

when mosfet enhancement mode of operation, vgs is _ and when vgs is _

positive, positive then the channel is widened 

you reduce the size in the enhancement mode of the channel and Id will be 

greater than Idss

silicon controlled rectifier (SCR) 

a four layer device contraining two n-type regions and two p-type regions

SCR is considered what type of component

a diode

SCR contains another input called

a gate

the gate in a SCR provides an additional means of _

triggering the device into the on-state

since the gate of an SCR is a approximally equivalent to a diode, 

takes .7v to trigger the SCR

IH

holding current, minimum forward current required to maintain conduction

Itsm

non repetitive surge current, absolute limit on surge current through device

Vgd

gate nontrigger voltage, maximum gate voltage that can be applied without triggering the SCR into conduction

Dv/Dt

critical rise rating, maximum rate of increse in anode to cathode voltage that the SCR can handle without false triggering occuring 

change in T

rise time of the increase in Vak

change in V

amount of change in VAK

DIAC can have _ in either direction

latch current

DIAC has _and behave essentially like a _

two-terminal bidrectional device, triac without a gate

DIAC are frequency used to trigger

traics in full-wave AC application

TRIACS acts like _

two SCR in parallel, equivalent to two latches

a TRIAC is a

3 terminal device, similar to the SCR

current in TRIAC

flows in both directions

TRIAC primary use is to 

control power to AC loads such as AC motors, heating systems etc