Electrnic Devices 2- BJT Flashcards
What is the ratio of IC to IB?
either betaDC or hFE, but bit alphaDC
For normal operation of a pnp BJT, the base must be ________ with respect to the emitter and ________ with respect to the collector.
negative, positive
When a transistor is used as a switch, it is stable in which two distinct regions?
saturation and cutoff
For a silicon transistor, when a base-emitter junction is forward-biased, it has a nominal voltage drop of
0.7 V.
What does betaDC vary with?
both IC and ºC
What are the two types of bipolar junction transistors?
npn and pnp
The value of betaDC
A transistor data sheet usually identifies betaDC as
hFE
What is the ratio of IC to IE?
either betaDC / (betaDC + 1) or alphaDC, but not DC
Which of the following is true for an npn or pnp transistor?
IE = IB + IC
What is the order of doping, from heavily to lightly doped, for each region?
emitter, collector, base
In what range of voltages is the transistor in the linear region of its operation?
0.7 < VCE < VCE(max)
The magnitude of dark current in a phototransistor usually falls in what range?
nA
What is (are) general-purpose/small-signal transistors case type(s)?
TO-18
TO-92
TO-39
TO-52
all of the above
What is (are) common fault(s) in a BJT-based circuit?
opens or shorts internal to the transistor
open bias resistor(s)
external opens and shorts on the circuit board
all of the above
The dc load line on a family of collector characteristic curves of a transistor shows the
saturation region.
cutoff region.
active region.
all of the above
Clipping is the result of
the input signal being too large.
the transistor being driven into saturation.
the transistor being driven into cutoff.
all of the above
Which transistor bias circuit arrangement provides good stability using negative feedback from collector to base?
collector-feedback bias
What is the dc input resistance at the base of a BJT?
betaDCRE
Which transistor bias circuit provides good Q-point stability with a single-polarity supply voltage?
voltage-divider bias
Ideally, for linear operation, a transistor should be biased so that the Q-point is
halfway between cutoff and saturation.
The most stable biasing technique used is the
voltage-divider bias.
Emitter bias requires
both positive and negative supply voltages.
Which transistor bias circuit arrangement has poor stability because its Q-point varies widely with DC?
base bias
What is the most common bias circuit?
voltage-divider
At saturation the value of VCE is nearly ________, and IC = ________.
zero, I(sat)
Voltage-divider bias has a relatively stable Q-point, as does
collector-feedback bias.
The linear (active) operating region of a transistor lies along the load line below ________ and above ________.
saturation, cutoff
The input resistance of the base of a voltage-divider biased transistor can be neglected
only if the base current is much smaller than the current through R2 (the lower bias resistor).
Which transistor bias circuit arrangement provides good Q-point stability, but requires both positive and negative supply voltages?
emitter bias
Changes in betaDC result in changes in
IC.
VCE.
the Q-point.
all of the above
How much is the base-to-emitter voltage of a transistor in the “on” state?
0.7 V
How many layers of material does a transistor have?
3
Which of the following equipment can check the condition of a transistor?
Current tracer
Digital display meter (DDM)
Ohmmeter (VOM)
All of the above
For what kind of amplifications can the active region of the common-emitter configuration be used?
Voltage
Current
Power
All of the above
In the active region, while the collector-base junction is ________-biased, the base-emitter is ________-biased.
reverse, forward
A transistor can be checked using a(n) ________.
curve tracer
digital meter
ohmmeter
Any of the above
What range of resistor values would you get when checking a transistor for forward- and reverse-biased conditions by an ohmmeter?
100 to a few k, exceeding 100 k
What is (are) the component(s) of electrical characteristics on the specification sheets?
On
Off
Small-signal characteristics
All of the above
In which region are both the collector-base and base-emitter junctions forward-biased?
Saturation
Which of the following is (are) the terminal(s) of a transistor?
Emitter
Base
Collector
All of the above
Which of the following configurations can a transistor set up?
Common-base
Common-emitter
Common-collector
All of the above
What does a reading of a large or small resistance in forward- and reverse-biased conditions indicate when checking a transistor using an ohmmeter?
Faulty device
Determine the value of alpha when beta= 100.
Alpha = Beta/(1+Beta).
Alpha = 100.
Alpha = 100/1+100.
Alpha = 100/101.
Alpha = 0.99.
Transistors are ________-terminal devices.
3
Which of the following can be obtained from the last scale factor of a curve tracer?
BetaAC
betaDC
IC / IB
How many carriers participate in the injection process of a unipolar device?
1
What are the ranges of the ac input and output resistance for a common-base configuration?
10 –100 , 50 k –1 M
What is the most frequently encountered transistor configuration?
Common-emitter
Which of the following regions is (are) part of the output characteristics of a transistor?
Active
Cutoff
Saturation
All of the above
How many individual pnp silicon transistors can be housed in a 14-pin plastic dual-in-line package?
4
In what decade was the first transistor created?
1940s
Most specification sheets are broken down into
maximum ratings
thermal characteristics
electrical characteristics
All of the above
What is (are) the component(s) of most specification sheets provided by the manufacturer?
Maximum ratings
Thermal characteristics
Electrical characteristics
All of the above
What is the ratio of the total width to that of the center layer for a transistor?
150:1
Which component of the collector current IC is called the leakage current?
Minority
For the BJT to operate in the active (linear) region, the base-emitter junction must be ________-biased and the base-collector junction must be ________-biased.
forward, reverse
The cutoff region is defined by IB ________ 0 A.
S(beta)
Which of the following is (are) related to an emitter-follower configuration?
The input and output signals are in phase.
The voltage gain is slightly less than 1.
Output is drawn from the emitter terminal.
All of the above
At what region of operation is the base-emitter junction forward biased and the base-collector junction reverse biased?
Linear or active
In a voltage-divider circuit, which one of the stability factors has the least effect on the device at very high temperature?
S(beta)
Which of the following is (are) a stability factor?
S(ICO)
S(VBE)
S(beta)
All of the above
Which of the following currents is nearly equal to each other?
IE and IC
Which of the following voltages must have a negative level (value) in any npn bias circuit?
VBC
For the typical transistor amplifier in the active region, VCE is usually about ________ % to ________ % of VCC.
25, 75
For the BJT to operate in the saturation region, the base-emitter junction must be ________-biased and the base-collector junction must be ________-biased
forward, forward
The ratio of which two currents is represented by beta?
IC and IB
Which of the following is assumed in the approximate analysis of a voltage divider circuit?
IB is essentially zero amperes.
R1 and R2 are considered to be series elements.
betaRE >_10R2
All of the above
The saturation region is defined by VCE ________ VCEsat.
<_
Which of the following is (are) the application(s) of a transistor?
Amplification of signal
Switching and control
Computer logic circuitry
All of the above
The current gain for the Darlington connection i
beta1(beta2)
Which of the following configurations has the lowest output impedance?
Emitter-follower
Which of the h-parameters corresponds to re in a common-base configuration?
hib
Which of the following is referred to as the reverse transfer voltage ratio?
hr
Which of the following conditions must be met to allow the use of the approximate approach in a voltage-divider bias configuration?
beta re<10R2
For a common-emitter amplifier, the purpose of swamping is
to reduce the effects of r’e
What is the typical value of the current gain of a common-base configuration?
Less than 1
What is the most important r parameter for amplifier analysis?
re′
An emitter-follower is also known as a
common-collector amplifier.
The ________ model fails to account for the output impedance level of the device and the feedback effect from output to input.
re
You have a need to apply an amplifier with a very high power gain. Which of the following would you choose?
common-emitter
What is the voltage gain of a feedback pair connection?
1
A common-emitter amplifier has ________ voltage gain, ________ current gain, ________ power gain, and ________ input impedance.
high, high, high, low
What is the range of the input impedance of a common-base configuration?
A few ohms to a maximum of 50
The advantage that a Sziklai pair has over a Darlington pair is
less input voltage is needed to turn it on.
What is the typical range of the output impedance of a common-emitter configuration?
40 k to 50 k
What is the unit of the parameter ho?
Siemen
What is the range of the current gain for BJT transistor amplifiers?
less than 1
1 to 100
above 100
All of the above
For the common-emitter fixed-bias configuration, there is a ________ phase shift between the input and output signals.
180
What does the negative sign in the voltage gain of the common-emitter fixed-bias configuration indicate?
The output and input voltages are 180º out of phase.
Which one of the following configurations has the lowest input impedance
Common-base
Which of the following represent(s) the advantage(s) of the system approach over the r-model approach?
Thevenin’s theorem can be used.
The effect of changing the load can be determined by a simple equation.
There is no need to go back to the ac equivalent model and analyze the entire network.
All of the above
The differential amplifier has
two inputs and one output.
The emitter-follower configuration has a ________ impedance at the input and a ________ impedance at the output.
high, low
The differential amplifier produces outputs that are
the difference of the two input voltages.
The ________ model suffers from being limited to a particular set of operating conditions if it is to be considered accurate.
hybrid equivalent
Under which of the following condition(s) is the current gain Av=beta?
ro >_10RC and RB >_10re
The ________ configuration is frequently used for impedance matching.
emitter-follower
When the bypass capacitor is removed from a common-emitter amplifier, the voltage gain
decreases.
In a common-base amplifier, the input signal is connected to the
emitter.
Which of the following is (are) true to achieve a good overall voltage gain for the circuit?
The effect of Rs and RL must be considered as a product and evaluated individually.
To analyze the common-emitter amplifier, what must be done to determine the dc equivalent circuit?
replace coupling and bypass capacitors with opens
For the common-emitter amplifier ac equivalent circuit, all capacitors are
effectively shorts.
Under which of the following conditions is the output impedance of the network approximately equal to RC for a common-emitter fixed-bias configuration?
ro >_10RC
Which of the following gains is less than 1 for a common-base configuration?
Ai
Which of the following define(s) the conversion efficiency?
Ac power to the load/dc power supplied
Which of the following should be done to obtain the ac equivalent of a network?
In an unbypassed emitter bias configuration hie replaces ________ in the re model.
beta re
Which of the following is (are) true regarding the input impedance for frequencies in the midrange<_100 kHz of a BJT transistor amplifier?
The input impedance is purely resistive.
It varies from a few ohms to megohms.
An ohmmeter cannot be used to measure the small-signal ac input impedance.
All of the above
For the collector dc feedback configuration, there is a ________ phase shift between the input and output signals.
180
A common-collector amplifier has ________ input resistance, ________ current gain, and ________ voltage gain.
high, high, low
The total gain of a multistage amplifier is the __
sum of dB voltage gains
Which of the following configurations has an output impedance Zo equal to RC?
Fixed-bias common-emitter
Common-emitter voltage-divider with bypass capacitor
Common-emitter voltage-divider without bypass capacitor
All of the above
For a common-emitter amplifier, the purpose of the emitter bypass capacitor is
to maximize amplifier gain.
For BJT amplifiers, the ________ gain typically ranges from a level just less than 1 to a level that may exceed 1000.
current
Which of the following configurations has a voltage gain of –RC /re?
Fixed-bias common-emitter and voltage-divider with bypass capacitor
Which of the following is (are) true regarding the output impedance for frequencies in the midrange<_100 kHz of a BJT transistor amplifier?
The output impedance is purely resistive.
It varies from a few ohms to more than 2 M.
An ohmmeter cannot be used to measure the small-signal ac output impedance.
All of the above
What is the limit of the efficiency defined by = Po / Pi?
Less than 1
What is re equal to in terms of h parameters?
hre / hoe
What is the controlling current in a common-base configuration?
Ie
Which of the following techniques can be used in the sinusoidal ac analysis of transistor networks?
Small- or large-signal
The input impedance of a BJT amplifier is purely ________ in nature and can vary from a few ________ to ________.
resistive, ohms, megohms
The ________ the source resistance and/or ________ the load resistance, the less the overall gain of an amplifier.
larger, smaller
A Darlington pair provides beta ________ for ________ input resistance.
multiplication, increased
A Darlington pair amplifier has
a low voltage gain and a high input impedance
