Transistors

31 questions

All types31 Multiple choice17 True / False8 Matching6

An electronics technician is analyzing an NPN bipolar junction transistor (BJT) configured as an amplifier in a common-emitter circuit. For the transistor to operate properly in its linear active region, which combination of internal junction biasing conditions must be established?

Forward-biasing both the base-emitter junction and the collector-base junction

Forward-biasing the base-emitter junction and reverse-biasing the collector-base junction

Reverse-biasing the base-emitter junction and forward-biasing the collector-base junction

Reverse-biasing both the base-emitter junction and the collector-base junction

Show answer & explanation

Answer: Forward-biasing the base-emitter junction and reverse-biasing the collector-base junction

Answer

Forward-biasing the base-emitter junction and reverse-biasing the collector-base junction

For any bipolar junction transistor (BJT) to function as a linear amplifier in the active region, the input base-emitter PN junction must be forward-biased to permit carrier injection, and the output collector-base PN junction must be reverse-biased to attract and collect these carriers across the junction.

Step-by-Step Solution

Identify the operational requirement for linear amplification in a BJT

Linear amplification requires the transistor to operate strictly in the active mode.

Operating outside the active region causes either signal clipping in saturation or complete signal cutoff.

Determine the required bias across the base-emitter (input) junction

The base-emitter junction must be forward-biased (positive base relative to emitter in an NPN transistor).

Forward bias reduces the potential barrier across the base-emitter junction, allowing majority carriers (electrons) to be injected from the emitter into the thin base layer.

Determine the required bias across the collector-base (output) junction

The collector-base junction must be reverse-biased (positive collector relative to base in an NPN transistor).

Reverse bias widens the collector-base depletion region and sets up a strong electric field that collects the injected electrons passing through the base into the collector.

Key Concept

BJT Active Region Biasing Conditions

Estimated Time:1m 15s

Question 2Question →

In an electronics schematic, a bipolar junction transistor (BJT) symbol features an arrow on the emitter lead pointing outward, away from the base. Which type of transistor is represented by this symbol?

PNP transistor

NPN transistor

Junction field-effect transistor (JFET)

Zener diode

Show answer & explanation

Answer: NPN transistor

Answer

An NPN transistor is represented by a BJT schematic symbol where the emitter arrow points outward, away from the base.

In electronics schematic diagrams, the arrow on the emitter terminal indicates the direction of conventional current flow. For an NPN transistor, this arrow points outward (away from the base). A common memory aid is 'NPN = Not Pointing iN'.

Step-by-Step Solution

Identify the component family and terminal structure.

The component is a Bipolar Junction Transistor (BJT) with three terminals: Collector, Base, and Emitter.

Recognizing the core three-terminal configuration establishes the category of semiconductor device.

Analyze the direction of the arrow located on the emitter terminal.

The arrow points outward (away from the base terminal).

In standard schematic conventions, the arrow on the emitter indicates the direction of conventional current flow during forward bias.

Match the arrow direction to the correct transistor polarity type.

An outward-pointing arrow corresponds to an NPN transistor ('Not Pointing iN'), whereas an inward-pointing arrow corresponds to a PNP transistor ('Pointing iN Proudly').

Differentiating between NPN and PNP configurations is essential for determining circuit polarity and proper biasing.

Key Concept

BJT schematic symbols use an arrow on the emitter terminal to distinguish between NPN (arrow pointing out) and PNP (arrow pointing in) configurations.

Estimated Time:45s

Question 3Question →

In a bipolar junction transistor (BJT) used in a common-emitter circuit, which terminal receives the small control current required to regulate the larger current flowing between the other two terminals?

Collector

Base

Emitter

Gate

Show answer & explanation

Answer: Base

Answer

The base terminal receives the small control current that regulates current flow between the collector and emitter.

In a bipolar junction transistor (BJT), the base is the central control terminal. A small current entering the base allows a significantly larger current to conduct between the collector and emitter, functioning as an amplifier or an electronic switch.

Step-by-Step Solution

Identify the terminal architecture of a bipolar junction transistor (BJT)

A standard BJT has three functional leads: the Base, the Collector, and the Emitter.

Establishes the available terminal functions specific to current-driven bipolar transistors.

Determine the control mechanism in a common-emitter configuration

Applying a small base current (

I_B

) modulates a larger collector current (

I_C

) according to the transistor gain (

\beta

), yielding

I_C = \beta \times I_B

Identifies the base as the designated input control lead in BJT switching and amplification circuits.

Key Concept

BJT Terminal Roles and Current Control

Estimated Time:45s

Question 4Question →

A transistor can use a small electrical signal at one terminal to control a much larger current flowing through its other terminals.

True

False

Show answer & explanation

Answer: True

Answer

True

The statement is true because the defining characteristic of a transistor is its ability to govern a large current path using a relatively weak electrical control signal, making it effective for both amplification and switching.

Step-by-Step Solution

Identify the primary operational functions of a transistor in electronic circuits.

Transistors are solid-state components designed to act as electronic switches and signal amplifiers.

Recalling the basic definition and purpose of semiconductor devices establishes the core functional criteria.

Evaluate the relationship between the input control signal and the output circuit current.

Applying a relatively small signal to the control terminal modulates and directs a much larger current between the power terminals.

This control mechanism allows small electronic signals to switch heavy loads on or off and amplify weak audio or radio signals.

Key Concept

Transistor amplification and electronic switching principle

Estimated Time:30s

Question 5Question →

When a bipolar junction transistor operates in its cutoff region, the collector-to-emitter path behaves as an open switch, preventing significant current flow through the output circuit.

True

False

Show answer & explanation

Answer: True

Answer

True

In the cutoff region, the control junction receives negligible bias voltage, preventing base current from flowing. Consequently, the output conduction path between the collector and emitter remains non-conductive, functioning electrically like an open switch.

Step-by-Step Solution

Identify the specified operating state of the transistor

The statement specifies operation in the cutoff region.

A transistor's conductivity between its output terminals depends directly on its operating state: cutoff, active, or saturation.

Evaluate the current conduction characteristics in cutoff

Without base drive voltage, base current is zero, which halts collector current and creates an open-circuit condition.

In electronic switching applications, cutoff represents the 'off' or open-switch state where current cannot pass to the load.

Key Concept

Transistor Cutoff Region and Switching Operation

Estimated Time:45s

Question 6Question →

Unlike current-driven bipolar devices, an enhancement-mode metal-oxide-semiconductor field-effect transistor (MOSFET) conducts significant current between its drain and source terminals when its gate-to-source voltage is zero.

True

False

Show answer & explanation

Answer: False

Answer

False. Enhancement-mode MOSFETs are normally-off devices that require a gate-to-source voltage exceeding the threshold voltage to establish a channel and conduct current.

The evaluation 'False' is correct because enhancement-mode MOSFETs are normally-off solid-state devices. Without an applied gate-to-source voltage exceeding the device's threshold voltage (

V_{th}

), the channel between the drain and source remains non-conductive, preventing drain current from flowing.

Step-by-Step Solution

Identify the component classification and operating archetype specified in the statement.

The statement specifies an enhancement-mode metal-oxide-semiconductor field-effect transistor (MOSFET).

Different transistor families (bipolar vs. field-effect) and operational modes (enhancement vs. depletion) exhibit distinct default conduction states.

Analyze the channel status of an enhancement-mode device at zero gate-to-source voltage (

V_{GS} = 0\text{ V}

V_{GS} = 0\text{ V}

, no conductive channel connects the drain and source regions across the substrate, resulting in an open circuit where drain current (

I_D

) is approximately zero.

Enhancement-mode devices are manufactured without a pre-formed channel and operate as normally-off switches.

Determine what electrical condition is required to initiate conduction.

An electric field created by applying a gate-to-source voltage greater than the threshold voltage (

V_{GS} > V_{th}

) is mandatory to enhance/induce a channel.

Because current does not flow at zero bias, the assertion that it conducts significant current at zero gate voltage is incorrect.

Key Concept

Default conduction state and threshold voltage mechanics of enhancement-mode field-effect transistors

Alternative Method

Recall the root word 'enhance': the channel must be actively enhanced (created) by gate voltage, meaning at zero gate voltage, no channel exists and no current flows.

Estimated Time:45s

Question 7Question →

A technician is troubleshooting a solid-state switching circuit that utilizes a silicon PNP bipolar junction transistor. The emitter terminal is connected directly to a +12V DC power source, and the collector is wired in series with a ground-referenced load. In order to drive this transistor into saturation and fully power the load, what specific voltage condition must exist at the base terminal, and what is the direction of conventional current flow through the device?

The base must be at a higher voltage potential than the emitter; conventional current flows from the collector to the emitter.

The base must be at a higher voltage potential than the emitter; conventional current flows from the emitter to the collector.

The base must be at a lower voltage potential than the emitter; conventional current flows from the emitter to the collector.

The base must be at a lower voltage potential than the emitter; conventional current flows from the collector to the emitter.

Show answer & explanation

Answer: The base must be at a lower voltage potential than the emitter; conventional current flows from the emitter to the collector.

Answer

The base must be at a lower voltage potential than the emitter; conventional current flows from the emitter to the collector.

The correct response accurately synthesizes both fundamental rules for a PNP transistor. First, to achieve saturation (full conduction), the base must be at a lower potential than the emitter to forward-bias the emitter-base junction. Second, unlike NPN devices, conventional current in a PNP transistor enters through the emitter and exits through the collector, following the direction of the emitter arrow on its schematic symbol.

Step-by-Step Solution

Identify the type of transistor and its fundamental biasing requirements.

The device is a PNP transistor. To turn it on (saturation), the base must be negative relative to the emitter.

PNP transistors operate with opposite polarities compared to NPN transistors. Forward-biasing the emitter-base junction requires the P-type emitter to be more positive than the N-type base.

Determine the direction of conventional current flow through the component.

Conventional current flows from the emitter to the collector.

The schematic symbol for a PNP transistor has an arrow on the emitter pointing inward (towards the base), which indicates the direction of conventional current flow from emitter to collector.

Synthesize the findings to select the correct operational state.

Base voltage must be lower than emitter voltage, with current flowing emitter-to-collector.

Combining the biasing rule (V_base < V_emitter) and the current path establishes the correct parameters for full conduction.

Key Concept

PNP Transistor Biasing and Current Flow

Question 8Question →

Which of the following correctly identifies the three terminal leads of a standard bipolar junction transistor (BJT)?

Source, gate, and drain

Anode, cathode, and gate

Emitter, base, and collector

Positive, negative, and ground

Show answer & explanation

Answer: Emitter, base, and collector

Answer

Emitter, base, and collector

A standard bipolar junction transistor (BJT) is a three-terminal semiconductor device consisting of the emitter (which emits charge carriers), the base (the thin middle region that controls current), and the collector (which gathers the charge carriers).

Step-by-Step Solution

Identify the component family and type specified in the question.

The component is a bipolar junction transistor (BJT).

Different transistor families utilize different lead naming conventions.

Recall the fundamental three-layer structure of a BJT.

A BJT is formed by two p-n junctions creating three regions: emitter, base, and collector.

The base controls current flow between the emitter and the collector.

Key Concept

Bipolar Junction Transistor (BJT) Terminals

Estimated Time:45s

Question 9Question →

A field-effect transistor (FET) regulates current flow through a semiconductor channel using an electrostatic field. Which terminal receives the controlling input voltage to modulate this current?

Drain

Gate

Source

Cathode

Show answer & explanation

Answer: Gate

Answer

The gate terminal is the input control electrode of a field-effect transistor that receives voltage to regulate channel current.

In a field-effect transistor (FET), the gate terminal functions as the control element. An applied input voltage at the gate generates an electrostatic field that modulates the resistance and carrier flow through the channel connecting the source and drain.

Step-by-Step Solution

Identify the standard three terminals of a field-effect transistor (FET).

A field-effect transistor consists of the source, drain, and gate terminals.

Identifying the terminal designations is the first step in determining their functional roles.

Differentiate between the current-carrying terminals and the control terminal.

Current travels through the channel between the source and drain terminals, while voltage applied to the gate terminal establishes an electric field that widens or restricts the channel.

The gate provides voltage-based control over current conduction without requiring significant input current.

Key Concept

Field-Effect Transistor (FET) Terminal Roles and Electrostatic Control

Estimated Time:45s

Question 10Question →

An NPN bipolar junction transistor circuit is configured with voltage-divider biasing from a single $15\text{ V}$ DC power supply. The voltage divider consists of an upper resistor $R_1 = 20\text{ k}\Omega$ connected to the positive supply and a lower resistor $R_2 = 10\text{ k}\Omega$ connected to ground. The emitter terminal is connected to ground through an emitter resistor $R_E = 1\text{ k}\Omega$ . Assuming a standard silicon base-to-emitter forward voltage drop of $V_{BE} = 0.7\text{ V}$ and negligible base current, what is the approximate DC emitter current ( $I_E$ ) flowing through the transistor?

5.0\text{ mA}

4.3\text{ mA}

5.7\text{ mA}

10.0\text{ mA}

Show answer & explanation

Answer: $4.3\text{ mA}$

Answer

4.3\text{ mA}

In an NPN voltage-divider biased circuit, the base voltage relative to ground is determined by the divider ratio:

V_B = 15\text{ V} \times (10\text{ k}\Omega / 30\text{ k}\Omega) = 5.0\text{ V}

. Because the base-emitter junction is forward-biased, it drops

0.7\text{ V}

, establishing an emitter voltage of

V_E = 5.0\text{ V} - 0.7\text{ V} = 4.3\text{ V}

. Dividing this emitter voltage by the

1\text{ k}\Omega

emitter resistor yields an emitter current of

4.3\text{ mA}

Step-by-Step Solution

Calculate the DC voltage at the base terminal (

V_B

) using the voltage divider rule

V_B = 15\text{ V} \times \frac{10\text{ k}\Omega}{20\text{ k}\Omega + 10\text{ k}\Omega} = 15\text{ V} \times \frac{1}{3} = 5.0\text{ V}

The base voltage is established by the ratio of the lower resistor to the total resistance across the supply when base current loading is negligible.

Determine the DC voltage at the emitter terminal (

V_E

) by accounting for the base-emitter forward voltage drop

V_E = V_B - V_{BE} = 5.0\text{ V} - 0.7\text{ V} = 4.3\text{ V}

In an active NPN transistor, the base-emitter junction is forward-biased, dropping approximately 0.7 V from base to emitter.

Apply Ohm's law across the emitter resistor (

R_E

) to calculate the emitter current (

I_E

)

I_E = \frac{V_E}{R_E} = \frac{4.3\text{ V}}{1\text{ k}\Omega} = 4.3\text{ mA}

The emitter current equals the voltage developed across the emitter resistor divided by its resistance.

Key Concept

Transistor Voltage-Divider DC Biasing and Emitter Current Calculation

Estimated Time:1m 30s

Question 11Question →

In electronics, bipolar junction transistors (BJTs) rely on three specialized terminals to control and route current. Match each BJT terminal to its primary functional role in a circuit.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Base matches with serving as the thin control layer that regulates carrier flow; Emitter matches with introducing and supplying majority charge carriers; Collector matches with gathering charge carriers to deliver output current.

Each terminal of a BJT has a designated task: the emitter supplies majority carriers, the base controls the rate of carrier flow via a small control signal, and the collector gathers these carriers to route current to the load circuit.

Step-by-Step Solution

Identify the primary role of the emitter terminal

The emitter is heavily doped to emit (inject) electrons or holes into the transistor body.

This establishes the supply of charge carriers needed for current flow.

Identify the primary role of the base terminal

The base controls the current flow through a small biasing voltage and current.

Because it is narrow and lightly doped, small variations at the base gate the bulk of current flowing across the device.

Identify the primary role of the collector terminal

The collector collects charge carriers swept across the base-collector junction.

It handles the bulk of power dissipation and passes the resulting amplified or switched current to the load.

Key Concept

Bipolar Junction Transistor (BJT) terminal roles and charge carrier dynamics

Estimated Time:45s

Question 12Question →

An electronics technician is analyzing solid-state switching and amplification circuits. Match each transistor operating region to its corresponding junction biasing condition and functional circuit behavior.

Click a left item, then click its matching right item

Show answer & explanation

Answer

BJT Cutoff matches both junctions reverse-biased (open switch); BJT Saturation matches both junctions forward-biased (closed switch); BJT Forward-Active matches forward-biased base-emitter and reverse-biased base-collector (linear amplification); JFET Ohmic Region matches unpinched channel at low drain voltage (voltage-controlled resistor).

Transistor states are governed by internal PN junction bias levels and gate field controls: Cutoff has both BJT junctions reverse-biased (acting as an open switch), Saturation has both BJT junctions forward-biased (acting as a closed switch), Forward-Active utilizes a forward-biased base-emitter and reverse-biased base-collector junction for linear amplification, and the JFET Ohmic region operates prior to pinch-off as a voltage-controlled variable resistor.

Step-by-Step Solution

Determine the junction bias conditions for digital BJT switching states.

Cutoff requires reverse-biasing both the base-emitter and base-collector junctions (open switch), while saturation requires forward-biasing both junctions (closed switch).

Biasing conditions control whether carrier flow is completely blocked or fully saturated across the semiconductor junctions.

Determine the junction bias conditions for BJT linear amplification.

Forward-active operation requires the base-emitter junction to be forward-biased (

V_{BE} \approx 0.7\text{ V}

) and the base-collector junction to be reverse-biased.

This asymmetric bias configuration allows a small base current to modulate a substantially larger collector current proportionally.

Analyze the operational characteristics of a field-effect transistor below pinch-off.

In the ohmic (triode) region, the drain voltage is lower than the pinch-off threshold, so the channel acts as an electric-field-controlled resistor.

The gate-to-source voltage alters depletion layer width, varying the cross-sectional conductive area and resistance of the channel.

Key Concept

Transistor Operating States, Biasing Rules, and Terminal Relationships

Estimated Time:1m 30s

Question 13Question →

Match each transistor terminal lead with its primary operational function in solid-state circuits.

Click a left item, then click its matching right item

Show answer & explanation

Answer

BJT Base pairs with 'Supplies the small input control current that regulates the main current flow'; BJT Emitter pairs with 'Injects the primary charge carriers into the middle semiconductor region'; BJT Collector pairs with 'Gathers majority charge carriers to route output current through the load'; FET Gate pairs with 'Applies an electrostatic field to modulate channel conductivity without drawing steady DC input current'.

In bipolar junction transistors, the base regulates the conduction pathway through a small input current, the emitter emits/injects majority charge carriers, and the collector gathers those carriers to deliver current to the load. In field-effect transistors, the gate acts as an electrostatic control terminal that modulates channel conduction via voltage without drawing significant steady-state current.

Step-by-Step Solution

Determine the control and injection roles of BJT leads

The base acts as the control terminal requiring current, and the emitter supplies the charge carriers.

Bipolar junction transistors are current-driven devices where a small base current forward-biases the base-emitter junction to release carriers from the emitter.

Determine the output gathering role of the BJT collector

The collector collects carriers that successfully pass through the thin base layer.

The collector is physically designed with a larger area and reverse bias to capture carriers and handle heat dissipation from load current.

Determine the voltage-control role of the FET gate lead

The gate regulates current through an electrostatic field without drawing steady current.

Field-effect transistors have extremely high input impedance at the gate, relying on voltage rather than current to modulate channel resistance.

Key Concept

Transistor Terminal Functions and Operating Mechanisms

Estimated Time:1m 0s

Question 14Question →

For a silicon PNP bipolar junction transistor to operate correctly in the active region as a linear amplifier, the DC biasing circuit must ensure that the collector terminal is maintained at a higher positive voltage relative to the emitter terminal.

True

False

Show answer & explanation

Answer: False

Answer

False

The statement is false because in a PNP transistor, the emitter must be at a higher positive potential than the collector to ensure current flows correctly (from emitter to collector) and the junctions are properly biased for the active region.

Step-by-Step Solution

Identify the specific transistor type and its intended operating state.

The device is a PNP bipolar junction transistor operating in the active region (as a linear amplifier).

Different transistor types (NPN vs. PNP) require completely opposite voltage polarities for the same operating state.

Recall the structural composition of a PNP transistor.

A PNP transistor consists of a P-type emitter, an N-type base, and a P-type collector.

Understanding the semiconductor materials (P or N) dictates how junctions must be biased.

Determine the required junction biasing for the active region.

For any BJT to act as a linear amplifier (active region), its emitter-base junction must be forward-biased, and its collector-base junction must be reverse-biased.

This specific biasing arrangement allows a small base current to control a larger collector current without entering saturation or cutoff.

Apply the biasing rules to the PNP terminal voltages.

To forward-bias the P-N emitter-base junction, the P-type emitter must be more positive than the N-type base. To reverse-bias the P-N collector-base junction, the P-type collector must be more negative than the N-type base.

Forward biasing requires connecting positive potential to P-type material; reverse biasing requires connecting negative potential to P-type material.

Evaluate the statement based on the deduced voltage potentials.

The emitter is the most positive terminal in a properly biased PNP amplifier circuit. Therefore, the collector is at a lower voltage relative to the emitter, making the original statement false.

The statement claims the collector is at a higher positive voltage, which incorrectly describes an NPN transistor's biasing.

Key Concept

Transistor Biasing and Polarity Configuration

Estimated Time:1m 30s

Question 15Question →

Solid-state electronic systems rely heavily on transistors for signal processing and power control. What are the two primary functions that a transistor performs in an electronic circuit?

Converting alternating current to direct current through rectification

Amplifying electrical signals and acting as an electronic switch

Storing electrical energy within an electrostatic field

Stepping up or down alternating voltages using electromagnetic induction

Show answer & explanation

Answer: Amplifying electrical signals and acting as an electronic switch

Answer

Amplifying electrical signals and acting as an electronic switch

Transistors are three-terminal active semiconductor devices designed to amplify weak electrical signals (such as audio or radio frequencies) and to serve as high-speed solid-state switches in digital logic circuits and power controllers.

Step-by-Step Solution

Identify the fundamental operational modes of a transistor in electronic circuits.

Transistors operate linearly in the active region to boost signal strength and non-linearly in cutoff/saturation regions to turn currents on and off.

Recognizing the functional scope of active semiconductor devices distinguishes them from passive components.

Match the identified operational modes with the standard electronic roles.

The two primary roles are amplification (signal gain) and switching (binary on/off control).

Alternative functions like rectification belong to diodes, charge storage belongs to capacitors, and inductive transformation belongs to transformers.

Key Concept

Primary functions of transistors (amplification and switching)

Estimated Time:45s

Question 16Question →

An electronics technician is troubleshooting an NPN bipolar junction transistor (BJT) configured as a solid-state switch. To transition the transistor from the cutoff state into saturation to energize an attached load, which electrical condition must be established at the base-emitter junction?

Reverse-biasing the base-emitter junction by making the base negative with respect to the emitter

Forward-biasing the base-emitter junction by applying a positive voltage to the base relative to the emitter

Maintaining zero volts across the base-emitter junction while reverse-biasing the collector-base junction

Applying a negative voltage to the collector while drawing conventional current out of the base terminal

Show answer & explanation

Answer: Forward-biasing the base-emitter junction by applying a positive voltage to the base relative to the emitter

Answer

Forward-biasing the base-emitter junction by applying a positive voltage to the base relative to the emitter causes the NPN transistor to transition into saturation.

In an NPN bipolar junction transistor, the base is composed of P-type semiconductor material while the emitter is N-type. To turn the transistor ON and enter saturation, the base-emitter junction must be forward-biased with a positive base voltage that exceeds the silicon barrier potential (

\approx 0.7\text{ V}

). This introduces base current, which allows heavy electron flow from emitter to collector, effectively closing the circuit across the load.

Step-by-Step Solution

Identify the semiconductor structure and terminal polarities for an NPN transistor.

An NPN bipolar junction transistor consists of an N-type emitter, a thin P-type base, and an N-type collector.

Understanding component internal structure determines the required polarity for current control.

Determine the required junction biasing to turn the transistor ON.

The base-emitter (P-N) junction must be forward-biased by establishing a base potential approximately

0.7\text{ V}

higher than the emitter.

Forward bias reduces the depletion region barrier, allowing majority carriers to flow across the junction.

Analyze the conditions necessary to reach the saturation operating state.

Supplying sufficient forward base current drives the collector-emitter voltage (

V_{CE}

) to its minimum near

0.2\text{ V}

, acting as a closed switch.

Saturation occurs when maximum collector current flows, turning the solid-state switch fully ON to power the load.

Key Concept

Transistor Biasing and Solid-State Switching States

Estimated Time:1m 0s

Question 17Question →

A technician is testing an unlabeled three-terminal semiconductor component using a digital multimeter in diode-check mode. The meter indicates a forward voltage drop of approximately $0.7\text{ V}$ when the positive (red) meter lead is placed on Terminal 1 and the negative (black) lead is placed on either Terminal 2 or Terminal 3. All reverse probe combinations, as well as direct measurements between Terminal 2 and Terminal 3, show an open-circuit (over-limit) reading. Which device type and lead configuration does this component represent?

PNP bipolar junction transistor with Terminal 1 as the base

NPN bipolar junction transistor with Terminal 1 as the base

NPN bipolar junction transistor with Terminal 1 as the collector

PNP bipolar junction transistor with Terminal 1 as the emitter

Show answer & explanation

Answer: NPN bipolar junction transistor with Terminal 1 as the base

Answer

An NPN bipolar junction transistor with Terminal 1 as the base.

In a bipolar junction transistor (BJT), the base-emitter and base-collector regions behave as two separate PN junction diodes sharing a common base material. For an NPN transistor, the base is composed of P-type semiconductor material, while the collector and emitter are N-type. Applying a positive test lead to the P-type base (Terminal 1) and a negative lead to either N-type terminal (Terminals 2 and 3) forward-biases each junction, yielding the standard silicon forward drop of approximately

0.7\text{ V}

Step-by-Step Solution

Analyze the multimeter diode test behavior

Conduction occurs only when Terminal 1 is connected to the positive meter lead and Terminals 2 or 3 are connected to the negative lead.

A digital multimeter diode test applies a small forward voltage from the red (+) probe to the black (-) probe to measure the junction threshold drop.

Identify the semiconductor layer structure

Terminal 1 acts as a common P-type anode, while Terminals 2 and 3 act as separate N-type cathodes.

Silicon PN junctions drop approximately

0.7\text{ V}

when forward-biased (anode positive relative to cathode).

Determine the transistor type and lead identity

The component is an NPN transistor where Terminal 1 is the Base (P-region), Terminal 2 is the Collector/Emitter (N-region), and Terminal 3 is the Emitter/Collector (N-region).

An NPN transistor electrically models as two back-to-back diodes with anodes joined at the base.

Key Concept

BJT internal PN junction polarity and diode-test verification

Estimated Time:1m 15s

Question 18Question →

On a standard electronic schematic diagram, the arrow on the emitter terminal of an NPN bipolar junction transistor points outward, away from the base.

True

False

Show answer & explanation

Answer: True

Answer

True: The emitter arrow on an NPN transistor schematic symbol points outward, away from the base.

In standard schematic diagrams, all bipolar junction transistors place a directional arrow on the emitter lead. For an NPN transistor, this arrow points outward, away from the base terminal, representing conventional current leaving the device. A widely used technician mnemonic is 'NPN = Not Pointing iN'.

Step-by-Step Solution

Identify the component type and schematic lead conventions.

The component is an NPN bipolar junction transistor (BJT) consisting of Base, Collector, and Emitter leads.

Determining the transistor family and terminal configuration is required to verify the symbol markings.

Determine the arrow placement and orientation for the NPN configuration.

The arrow is always positioned on the emitter lead and points outward (away from the base line).

Schematic symbols use the emitter arrow to indicate the direction of conventional current flow, which flows out of the emitter in an NPN transistor (commonly recalled with the mnemonic 'Not Pointing iN').

Evaluate the accuracy of the provided statement.

The statement matches standard schematic conventions exactly.

An outward-pointing emitter arrow uniquely defines the NPN transistor symbol.

Key Concept

BJT Schematic Symbols and Emitter Arrow Orientation

Estimated Time:40s

Question 19Question →

In standard electronic schematic symbols for bipolar junction transistors (BJTs), the directional arrow indicating current flow is positioned on the emitter terminal.

True

False

Show answer & explanation

Answer: True

Answer

True. The directional arrow in a BJT schematic symbol is always located on the emitter terminal.

The statement is true because electronic drafting standards universally position the current direction arrow on the emitter terminal of a BJT. This arrow serves two primary purposes: it distinguishes the emitter lead from the collector lead, and its direction (pointing out for NPN, pointing in for PNP) identifies the polarity type of the transistor.

Step-by-Step Solution

Identify the standard terminals of a bipolar junction transistor (BJT).

A BJT has three terminals: base, collector, and emitter.

Recognizing the physical and schematic lead names is necessary to evaluate the statement.

Recall the schematic drawing conventions used to represent BJTs.

The base is drawn as a vertical bar, the collector is an un-arrowed diagonal branch, and the emitter is a diagonal branch with an arrow.

Standard electronics symbology uses the arrow to indicate the direction of conventional current flow through the device.

Verify the terminal location of the identifying arrow.

The arrow is placed exclusively on the emitter terminal for both NPN and PNP configurations.

The arrow differentiates the emitter from the collector and establishes the transistor type (pointing outward for NPN, inward for PNP).

Key Concept

BJT Schematic Symbol Conventions

Estimated Time:45s

Question 20Question →

In a standard bipolar junction transistor (BJT), which terminal receives the small input control current that regulates the larger current flow between the remaining two terminals?

Collector

Base

Emitter

Gate

Show answer & explanation

Answer: Base

Answer

The base terminal is the control electrode that receives the small input current in a bipolar junction transistor.

In a bipolar junction transistor (BJT), the base terminal is the thin middle semiconductor layer that controls the flow of charge carriers. Injecting a small base current allows a much larger current to flow from the collector to the emitter (or vice versa in PNP transistors), making the base the primary control terminal.

Step-by-Step Solution

Identify the three terminals of a bipolar junction transistor (BJT) and their basic functions.

A BJT consists of an emitter, a base, and a collector.

Recognizing the standard terminal configuration is essential for analyzing transistor operation.

Determine which terminal acts as the input control mechanism for current regulation.

The base is the thin, lightly doped central region where a small base current (

I_B

) directly controls a substantially larger collector current (

I_C

In current-controlled bipolar devices, variation in base current governs overall device conduction.

Key Concept

BJT Terminal Roles and Current Control Mechanism

Estimated Time:45s

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