Are you ready to power up your knowledge with the Ultimate Bipolar Transistor Quiz? This free bipolar transistor quiz is your chance to tackle challenging bipolar transistor questions, sharpen your understanding of transistor amplifiers in our transistor amplifier quiz segment, and conquer a comprehensive semiconductor transistor test that covers fundamental device physics and biasing techniques. Whether you're curious about common-emitter configurations, beta calculations, or base-emitter junction behavior, each electronics transistor quiz question challenges you with real-world scenarios to strengthen your practical skills. Looking for a warm-up? Try our electric circuits quiz or flex your skills with some digital electronics trivia. Dive in now, test your smarts, get immediate feedback on each answer, and elevate your circuit design confidence!
What are the three terminals of an NPN bipolar junction transistor called?
Gate, Drain, Source
Anode, Cathode, Gate
Collector, Emitter, Base
Source, Body, Gate
A bipolar junction transistor has three terminals: the collector, emitter, and base. The collector collects charge carriers, the emitter emits them, and the base controls the flow. This naming convention applies to both NPN and PNP BJTs. See more details at Wikipedia.
In an NPN transistor operating in the forward active region, which junction is forward biased?
BaseCollector junction
CollectorSubstrate junction
BaseEmitter junction
CollectorEmitter junction
In the forward active region, the baseemitter junction of an NPN transistor is forward biased while the basecollector junction is reverse biased. Forward biasing the baseemitter junction lowers the barrier for electron injection from the emitter to the base. This is essential for normal amplifier operation. More information at Electronics-Tutorials.
Which region of a bipolar junction transistor is intentionally lightly doped to enhance control over the device's behavior?
Emitter
Collector
Base
Substrate
The base region of a bipolar transistor is lightly doped and thin to enable efficient control of carrier injection between emitter and collector. The emitter is heavily doped for high injection efficiency, and the collector is moderately doped to handle voltage. The substrate is part of the device structure, not one of the active BJT terminals. See Wikipedia.
What bias condition defines the forward active mode of a bipolar junction transistor?
Both base-emitter and base-collector junctions are forward biased
Base-emitter junction is forward biased and base-collector junction is reverse biased
Base-emitter junction is reverse biased and base-collector junction is forward biased
Both base-emitter and base-collector junctions are reverse biased
Forward active mode occurs when the base-emitter junction is forward biased, allowing carrier injection, and the base-collector junction is reverse biased, enabling the collector to collect carriers. This biasing yields amplification action. Other junction bias combinations correspond to saturation, cutoff, or reverse active modes. More details at Electronics-Tutorials.
What symbol represents the current gain (ratio of collector current to base current) in a bipolar transistor?
Alpha (?)
Beta (?)
Gamma (?)
Delta (?)
? (beta) represents the current gain in a bipolar transistor and is defined as the ratio of collector current (Ic) to base current (Ib). ? (alpha) is the ratio of collector current to emitter current. Beta is commonly used to describe amplification capability. See Wikipedia.
If a bipolar transistor has a current gain (?) of 100 and a base current (Ib) of 20 A, what is the collector current (Ic)?
0.2 mA
2 mA
20 mA
200 mA
The collector current Ic in a BJT is given by Ic = ? Ib. With ? = 100 and Ib = 20 A, Ic = 100 20 A = 2000 A = 2 mA. This relationship is fundamental to transistor amplification. More at Wikipedia.
Which operating region of a bipolar transistor occurs when both the base-emitter and base-collector junctions are forward biased?
Cutoff
Active
Saturation
Reverse active
Saturation occurs when both the base-emitter and base-collector junctions of a BJT are forward biased, causing the transistor to conduct maximum current with minimal voltage drop across collector-emitter. This region is used for switching applications in the 'on' state. For amplification, the active region is used. Read more at Electronics-Tutorials.
In the schematic symbol of an NPN transistor, which way does the arrow on the emitter leg point?
Into the base
Out of the base
Towards the collector
Parallel to the collector
For an NPN transistor symbol, the arrow on the emitter leg points out of the base, indicating the direction of conventional current flow (from base to emitter). In a PNP transistor, the arrow points into the base. This convention helps differentiate transistor types. More info at Wikipedia.
Which bipolar transistor configuration is known for having the highest input impedance?
Common base
Common emitter
Common collector (emitter follower)
Darlington pair
The common-collector or emitter-follower configuration presents a high input impedance because the base sees the emitter-driven impedance multiplied by ? plus the base-emitter junction impedance. This makes it ideal for impedance matching. The Darlington pair has an even higher gain but the basic highest input impedance among single-transistor configs is the emitter follower. Details at Wikipedia.
What is the approximate small-signal emitter resistance (re) in a bipolar transistor at room temperature?
25? / IE
25mV / IE
Thermal voltage IE
IE / 25mV
The small-signal emitter resistance re is approximately equal to the thermal voltage (?25 mV at room temperature) divided by the emitter current IE (re = 25mV/IE). This parameter is critical in AC analysis and gain calculations. For more, see Electronics-Tutorials.
What does the output characteristic curve of a bipolar transistor plot?
Ic versus Ib at constant Vce
Ib versus Vce at constant Ic
Ic versus VCE at various Ib values
Vbe versus Ib at constant Ic
The output characteristic of a BJT plots collector current (Ic) against collector-emitter voltage (VCE) for different fixed base current (Ib) values. These curves show active, saturation, and cutoff behavior. They are fundamental for designing bias and amplifier operation. Reference: Electronics-Tutorials.
Which biasing method uses two resistors to establish a stable base voltage for a bipolar transistor?
Fixed bias
Collector feedback bias
Voltage-divider bias
Emitter bias
Voltage-divider bias employs two resistors connected as a divider between supply and ground to provide a stable base voltage. It offers good thermal stability and reduces variation in operating point due to ? variations. It's widely used in amplifier circuits. Learn more at Electronics-Tutorials.
What is the name of the effect in bipolar transistors where increasing collector-emitter voltage reduces the effective base width and increases collector current?
Avalanche breakdown
Early effect
Saturation effect
Thermal runaway
The Early effect, or base-width modulation, occurs when raising the collector-base voltage widens the depletion region and narrows the base, leading to increased collector current. It leads to a finite output resistance in the active region. This effect is characterized by the Early voltage. More at Wikipedia.
What term describes the condition where rising temperature in a transistor leads to increased collector current, causing more heating and potential device failure?
Thermal runaway
Saturation
Reverse bias breakdown
Hysteresis
Thermal runaway is a positive feedback condition where higher temperatures increase carrier activity and collector current, which generates more heat. Without adequate thermal stabilization, a transistor can be destroyed. Proper biasing and heat sinking mitigate this. See Wikipedia.
In the cutoff region of a BJT, what is the bias state of the base-emitter and base-collector junctions?
Both junctions forward biased
Both junctions reverse biased
Base-emitter forward, base-collector reverse
Base-emitter reverse, base-collector forward
In cutoff, both the base-emitter and base-collector junctions are reverse biased. This stops carrier injection and the transistor behaves as an open switch with negligible collector current. It's used for the 'off' state in switching applications. More at Electronics-Tutorials.
Which coupling technique uses a resistor and a capacitor to isolate DC bias between amplifier stages while allowing AC signals to pass?
Direct coupling
Transformer coupling
RC coupling
LC coupling
RC coupling employs a coupling capacitor in series with a resistor to block DC components and pass AC signals between stages. It is simple, cost-effective, and widely used in audio and RF circuits. Alternative methods include transformer and LC coupling. Details at Wikipedia.
What phenomenon describes the apparent increase in input capacitance of an inverting amplifier stage due to feedback through the collector-base capacitance?
Beta enhancement
Miller effect
Early effect
Thermal feedback
The Miller effect is the multiplication of the transistors collectorbase capacitance by (1 + |Av|), appearing between input and ground. It significantly reduces amplifier bandwidth by increasing effective input capacitance. This is critical in high-frequency amplifier design. See Wikipedia.
Approximately, how do you calculate the voltage gain (Av) of a common-emitter amplifier with an unbypassed emitter resistor Re?
-Rc/re
-Rc/(re + Re)
-Rc/(re + (?+1)Re)
-?Rc/re
When the emitter resistor Re is unbypassed, the gain is reduced by emitter degeneration and approximated by Av = -Rc/(re + (?+1)Re). The (?+1) factor comes from feedback through the emitter. This formula shows how degeneration stabilizes gain. More at Electronics-Tutorials.
Which internal capacitances of a bipolar transistor predominantly determine its high-frequency bandwidth?
Ccs and Coss
Cbe and Cbc
Cgd and Cgs
Cje and Cjc
The base-emitter capacitance (Cbe) and base-collector capacitance (Cbc) are key in limiting the high-frequency performance of BJTs. Cbe affects the input pole and Cbc contributes via the Miller effect. Understanding these parasitics is essential for RF design. Reference: Electronics-Tutorials.
In a bipolar differential pair biased with emitter current IE, what is the approximate differential input resistance (Rid)?
re
2re
4re
IE/2re
For a BJT differential pair, the differential input resistance is roughly 2 re, where re ? 25mV/IE. This arises because each transistor sees half the tail current when driven differentially. Accurate modelling refines this value but 2re is a good first estimate. Details at Electronics-Tutorials.
What is the approximate expression for the overall current gain of a Darlington pair in terms of individual gains ?1 and ?2?
?1 + ?2
?1 ?2
?1?2 + ?1 + ?2
(?1 + 1)(?2 + 1)
The total gain of a Darlington configuration is roughly ?1?2 + ?1 + ?2, which is equivalent to (?1+1)(?2+1) - 1. This high gain is one advantage of the Darlington pair, though it has greater VBE. More at Wikipedia.
Avalanche breakdown in a BJT typically occurs at which junction when subjected to high reverse-bias voltage?
Emitter-base junction under forward bias
Base-collector junction under reverse bias
Collector-emitter junction under forward bias
Base-emitter junction under reverse bias
Avalanche breakdown occurs when the basecollector junction is driven into high reverse bias, causing ionization of carriers and a sudden increase in current. This can damage the transistor if uncontrolled. Designers use breakdown voltages (BVcbo, BVceo) to specify safe operating limits. See Wikipedia.
What is the typical temperature coefficient of the base-emitter voltage (VBE) drop in a silicon BJT?
+2 mV/C
-2 mV/C
-0.1 mV/C
+0.1 mV/C
The base-emitter voltage of a silicon BJT decreases by about 2 mV per C rise in temperature, reflecting increased carrier activity. This negative temperature coefficient is important for bias stabilization and compensation techniques. More at Electronics StackExchange.
What does the transition frequency (fT) of a bipolar transistor signify?
Frequency at which power gain peaks
Frequency at which current gain falls to unity
Frequency at which voltage gain doubles
Frequency at which noise figure is minimum
The transition frequency fT is defined as the frequency at which the short-circuit current gain of the transistor becomes unity. It reflects the devices high-frequency capability. Higher fT indicates suitability for RF applications. See Wikipedia.
A transistor has Cbe = 10 pF, Cbc = 2 pF, and a voltage gain of -100. What is the effective input capacitance due to the Miller effect?
112 pF
212 pF
20 pF
202 pF
The effective input capacitance is given by C_in = Cbe + Cbc (1 + |Av|). Substituting Cbe = 10 pF, Cbc = 2 pF, Av = -100 yields 10 pF + 2 pF 101 = 212 pF. This demonstrates how the Miller effect can dominate input capacitance and limit bandwidth. More at Electronics-Tutorials.
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Study Outcomes
Identify BJT Fundamentals -
Understand the structure, operation, and charge flow in bipolar junction transistors to solidify your semiconductor foundations.
Analyze Amplifier Configurations -
Distinguish between common-emitter, common-base, and common-collector setups to choose the right transistor amplifier for each application.
Apply Biasing Techniques -
Use proper biasing methods to stabilize transistor amplifier performance under varying signal and temperature conditions.
Interpret Characteristic Curves -
Read and evaluate input/output curves to predict transistor behavior in real-world circuits.
Solve Practical Scenarios -
Tackle real-world bipolar transistor questions to reinforce theory through hands-on problem-solving.
Assess Your Electronics Skills -
Measure your knowledge with targeted quiz challenges, tracking your progress in the bipolar transistor quiz.
Cheat Sheet
Transistor Structure and Operation -
Review the layered p - n - p or n - p - n structure where minority carriers diffuse across junctions. Remember that in active mode, the base - emitter junction is forward-biased (~0.7 V) while the base - collector is reverse-biased, a core concept in any bipolar transistor quiz.
Current Gain and Ebers - Moll Relation -
Know that IC ≈ β·IB and IE ≈ (β+1)·IB (where β is the DC current gain). The Ebers - Moll equation links junction currents via exp(VBE/VT), so practice the formula IC = IS·(e^(VBE/VT) −1) to ace your semiconductor transistor test.
DC Biasing and Q”Point Stability -
Master voltage-divider biasing from sources like MIT OpenCourseWare to maintain a stable Q-point against temperature drift. Use the rule-of-thumb R1: R2 ≈ 10:1 and check that IB ≈ (VCC·R2/(R1+R2) - 0.7 V)/((β+1)·RE) for consistent transistor amplifier quiz designs.
Small”Signal Hybrid”π Model -
Learn the hybrid-π equivalent: rπ = β/gm and gm = IC/VT (VT≈25 mV at room temperature). A quick mnemonic is "gm grows with IC," helping you solve electronics transistor quiz problems on input/output impedance and voltage gain.
Common Amplifier Configurations -
Differentiate common-emitter (high gain, moderate input impedance), common-base (low input impedance, wide bandwidth) and common-collector (emitter follower, unity gain, high input impedance). Practicing these in a bipolar transistor questions set prepares you for real-world amplifier design challenges.
