Bipolar Junction Transistor

Module 3 Reviewer

NPN , PNP

Name the two types of BJTs according to their structure.

Emitter, Collector, Base

The BJT is a three-terminal device. Name the three terminals.

2 P-N Junctions (Base-Emitter Junction & Base-Collector Junction)

The BJT is a three-terminal device. Name the two junctions.

because of their difference in doping levels

What separates the three regions in a BJT?

BJT (Bipolar Junction Transistor)

It is constructed with three doped semiconductor regions separated by two pn junctions.

NPN

One type of BJT that is consist of two n regions separated by a p region.

PNP

One type of BJT that is consist of two p regions separated by a n region.

Bipolar

Refers to the use of both holes and electrons as current carriers in the transistor structure.

Substrate

It is a physical supporting material for the transistor.

Base-emitter junction

The pn junction joining the base region and the emitter region is called?

Base-collector junction

The pn junction joining the base region and the collector region is called

Lead

What type of wire is connected to each of the three regions?

a.) Lightly Doped

Base region is?

a.) Lightly Doped
b.) Moderately Doped
c.) Heavily Doped

c.) Heavily Doped

Emitter region is?

a.) Lightly Doped
b.) Moderately Doped
c.) Heavily Doped

b.) Moderately Doped

Collector region is?

a.) Lightly Doped
b.) Moderately Doped
c.) Heavily Doped

FALSE

Correct: Because of their difference in doping
levels, the emitter and collector are not interchangeable.

The emitter and collector terminals are in interchangeable.

TRUE or FALSE

NPN

For what type of BJT is this schematic symbol?

PNP

For what type of BJT is this schematic symbol?

c.) forward-biased, reverse-biased

As an amplifier, for the both BJT types, the base-emitter (BE) junction is _________ and the base-collector (BC) junction is ________ .

a.) forward-biased, forward-biased
b.) reverse-biased, reverse-biased
c.) forward-biased, reverse-biased
d.) reverse-biased, forward-biased

forward-reverse bias

As an amplifier, notice that in both cases the base-emitter (BE) junction is forward-biased and the base-collector (BC) junction is reverse-biased. This condition is called ?

d.) lightly doped cathode and very thin

In PNP, the n region is?

a.) heavily doped anode and very thick
b.) heavily doped cathode and very thick
c.) lightly doped anode and very thin
d.) lightly doped cathode and very thin

c.) lightly doped anode and very thin

In NPN, the p region is?

a.) heavily doped anode and very thick
b.) heavily doped cathode and very thick
c.) lightly doped anode and very thin
d.) lightly doped cathode and very thin

FALSE

Correct: The emitter current is slightly greater than the collector current because of the small base current that splits off from the total current injected into the base region from the emitter.

The emitter current is slightly lesser than the collector current because of the small base current that splits off from the total current injected into the base region from the emitter.

TRUE OR FALSE

Base-emitter - Forward-biased
Base-collector - Reverse-biased

What are the bias conditions of the base-emitter and base-collector junctions for a transistor to operate as an amplifier?

Emitter Current (IE)

Which is the largest of the three transistor currents?

smaller

Is the base current smaller or larger than the emitter
current?

thinner

Collector - widest region

Is the base region much thinner or much wider than the collector and emitter regions?

IE = IC + IB
IE = 1mA + 10 microA
IE = 1.001 x 10^-3 A

If the collector current is 1 mA and the base current is 10 microA, what is the emitter current?

DC beta

It is the ratio of the dc collector current (IC) to the dc base current (IB)

DC alpha

It is the ratio of the dc collector current (IC) to the dc emitter current (IE)

a.) small

IB is very ______ compared to IE or IC.

a.) small
b.) large

less than 20 to 200 or higher

Typical values of bDC range from __________.

0.95 to 0.99 or greater,

Typical values of aDC range from

TRUE

aDC (DC alpha) is always less than 1.

TRUE or FALSE

NPN transistor, PNP

In BJT, the former is ____ , and the latter is _____.

TRUE

The outer layers have widths much greater
than the sandwiched p - or n -type material.

TRUE or FALSE

unipolar

If only one carrier is employed (electron or hole), it is considered a ________ device.

Schottky Diode

One example of unipolar device.

microamperes, milliamperes

The magnitude of the base current is typically on the order of _________, as compared to _____________ for the emitter and collector currents.

majority and minority carriers

The collector current is consists of two components
namely:

(ICO) leakage current or IC current with emitter terminal open

Other name for the minority carrier component of collector current

Base terminal

In common base configuration, what terminal is closest to, or at, ground potential?

FALSE

Correct:
The arrow in the graphic symbol defines the direction of emitter current (conventional flow) through the device.

The arrow in the graphic symbol defines the direction of collector current (conventional flow) through the device.


TRUE or FALSE

emitter current

The arrow in the graphic symbol defines the direction of _________ current (conventional flow) through the device.

FALSE

Correct:
In the active region the base–emitter junction is forward-biased, whereas the collector– base junction is reverse-biased.

In the cutoff region the base–emitter junction is forward-biased, whereas the collector– base junction is reverse-biased.

TRUE or FALSE

a.) cutoff region

The ________ is defined as that region where the collector current is 0 A.

a.) cutoff region
b.) saturation region
c.) active region

They are both reverse biased.

In cutoff region what are the biasing condition of the base-emitter and base-collector junction?

Base emitter is forward-biased
Base-collector is reverse-biased

In active region what are the biasing condition of the base-emitter and base-collector junction?

Both are forward-biased

In saturation region what are the biasing condition of the base-emitter and base-collector junction?

c.) closed switch

In saturation region, the transistor acts as?

a.) amplifier
b.) open switch
c.) closed switch

b.) open switch

In cutoff region, the transistor acts as?

a.) amplifier
b.) open switch
c.) closed switch

a.) amplifier

In active region, the transistor acts as?

a.) amplifier
b.) open switch
c.) closed switch

Saturation

______ is the state of a BJT in which the collector current has reached a maximum and is independent of the base
current.

active or linear

When the VCE exceeds 0.7 V, the base-collector junction becomes reverse-biased and the transistor goes into the ____________ region of its operation.

b.) breakdown region

A transistor should never be operated in
this region.

a.) cutoff region
b.) breakdown region
c.) saturation region
d.) active region

a.) cutoff region

When IB = 0, the transistor is in the
what region?

a.) cutoff region
b.) breakdown region
c.) saturation region
d.) active region

Cutoff

It is the nonconducting state of a transistor.

FALSE

Correct: Under cutoff region, there is very small amount of collector leakage current, ICEO, due mainly to thermally produced carriers.

Under cutoff region, there is no amount of collector leakage current, ICEO, due mainly to thermally produced carriers.

TRUE or FALSE

FALSE

When the base-emitter junction becomes forward-biased and the base current is increased, the collector current also increases.

When the base-emitter junction becomes forward-biased and the base current is increased, the collector current decreases.

TRUE or FALSE

load line

A ______ is a straight line that represents the voltage and current in the linear portion of the circuit that is connected to a device (a transistor in this case).

Amplification

It is the process of linearly increasing the amplitude of an electrical signal and is one of the major properties of a transistor.

TRUE

The base current in a transistor is very small compared to the collector and emitter currents. Because of this, the collector current is approximately equal to the emitter current.

TRUE or FALSE

Dr. S. William Shockley, Walter H. Brattain, and John Bardeen

___________ demonstrated the amplifying action of the first transistor at the Bell Telephone Laboratories On December 23, 1947.

Bell Telephone Laboratories, December 23, 1947

Dr. S. William Shockley, Walter H. Brattain, and John Bardeen demonstrated the amplifying action of the first transistor at the _________ On ______________.

BJT and FET

Two types of transistors.

linear amplifier, electronic switch

BJT is used in two broad areas: ______ and ______

Common Emitter Configuration

The most frequently transistor configuration.

Common Emitter Configuration

In this configuration, the emitter is common to both input and output terminals.

Common Base Configuration

In this configuration, the base is common to both input and output terminals.

Common Base Configuration

In this configuration, the base is at the closest or at the ground potential.

Common Collector Configuration

This configuration is impedance matching purposes since it has a high input impedance and low output impedance.

Stability of System

It defines how sensitive the system to temperature variations.

a.) increase in AC voltage, power , current

It is the result of a transfer of energy from the applied DC supplies.

a.) increase in AC voltage, power , current
b.) decrease in AC voltage, power , current
c.) increase in DC voltage, power , current
d.) decrease in DC voltage, power , current

Operating point or Quiescent Point (Q-point)

It is the fixed point in characteristics that define the region that will be employed for amplification of the applied signal.

Quiescent Point (Q-point)

Operating point is also called as?

FALSE

Correct:
In DC bias and analysis, all the AC sources must be open.

In DC bias and analysis, all the AC sources must be shorted.

TRUE or FALSE

Saturation

It is the term applied to any system where levels have reached their maximum values.

- the base-collector junction is no longer reverse-biased
-output amplified signal will be distorted

Give reasons why saturation is avoided.

TRUE

The more stable a configuration, the less its response will change due to undesirable changes in temperature and parameter variations.

TRUE or FALSE

Superposition theorem

It is applicable for the analysis and design of the dc and ac components of a BJT network, permitting the separation of the analysis of the dc and ac responses of the system.

model

A _____ is a combination of circuit elements, properly chosen, that best approximates the actual behavior of a semiconductor device under specific operating conditions.

base to ground

In AC analysis, the input impedance is defined from?

base current of transistor

In AC analysis, the input current is defined as?

the voltage from collector to ground

In AC analysis, the output voltage is defined as?

the current through the load resistor RC.

In AC analysis, the output current is defined as?

TRUE

In AC analysis, the input current Ii and output current Io are, by definition, defined to enter the system.

TRUE or FALSE

b.) fixed-bias circuit

The ______ is the simplest transistor dc bias configuration.

a.) voltage divider bias circuit
b.) fixed-bias circuit
c.) emitter follower circuit
d.) common base circuit

- by adding an emitter resistor
- by adding a feedback path from collector to base

How can we improve stability in a BJT transistor? Give atleast two.

Transistors

_________ are three-terminal devices of three semiconductor layers having a base or center layer a great deal thinner than the other two layers. The outer two layers are both of either n - or p -type materials, with the sandwiched layer the opposite type.

dc emitter current

It is the largest current of the dc transistor.

base current

It is the smallest current of the dc transistor.

Majority carrier and minority carrier (leakage current)

The collector current is made up of two components. What are those?

emitter

The arrow in the transistor symbol defines the direction of conventional current flow for the ______ current and thereby defines the direction for the other currents of the device.

a.) 2

A three-terminal device needs ___ sets of characteristics to completely define its characteristics.

a.) 2
b.) 3
c.) 4
d.) 5

0.7

On an average basis, as a first approximation, the base-to-emitter voltage of an operating transistor can be assumed to be ____ V .

a.) alpha

The quantity ____ relates the collector and emitter currents and is always close to one .

a.) alpha
b.) beta
c.) delta
d.) gamma

FALSE

Correct:
The impedance between terminals of a forward-biased junction is always relatively small.

The impedance between terminals of a forward-biased junction is always relatively large.

TRUE or FALSE

FALSE

Correct:
The impedance between terminals of a reverse-biased junction is usually quite large.

The impedance between terminals of a reverse-biased junction is usually quite small.

TRUE or FALSE

npn

The arrow in the symbol of an ____ transistor points out of the device.

pnp

The arrow points in to the center of the symbol for a ___ transistor