Early Effect MCQ Quiz - Objective Question with Answer for Early Effect - Download Free PDF

Explanation:

A common-base (CB) configuration of a Bipolar Junction Transistor (BJT) is one of the three basic transistor configurations, where the base terminal is common to both the input and output circuits. It is often used in high-frequency applications due to its low input impedance and high output impedance.

Output Characteristics: The output characteristics of a CB configuration are typically plotted between the output current (collector current, I_C) and the output voltage (voltage across the collector and base terminals, V_CB) for different levels of input current (emitter current, I_E). These characteristics provide important insights into the transistor's behavior and operational regions.

Characteristics:

• The graph typically consists of three regions: the cutoff region, the active region, and the saturation region.
• In the active region, I_C remains approximately constant for a given I_E, even as V_CB increases. This is because the transistor is operating as an amplifier in this region.
• However, due to the Early effect, there is a slight increase in I_C with increasing V_CB, as the effective base width decreases, leading to a higher collector current.

Correct Option Analysis:

The correct option is:

Option 3: In a CB configuration, the current gain is slightly greater than one.

This option is incorrect. In a common-base configuration, the current gain (denoted as α) is defined as the ratio of the collector current (I_C) to the emitter current (I_E). Since a small portion of the emitter current is lost as base current (I_B), the current gain is always slightly less than 1. Mathematically: α = IC / IE, where α < 1.

Typical values of α range from 0.95 to 0.99 for most BJTs, depending on their design and manufacturing process. Therefore, the statement that the current gain is slightly greater than one is factually incorrect

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width (base narrowing) and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.
• Due to this the slope of the output characteristics of a transistor in CE configuration is higher than that in CB configuration.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the Input capacitance of the Common – Emitter Amplifier.

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the input capacitance of the Common – Emitter Amplifier.

Thermal runaway: Thermal runaway is a self-destruction process in which an increase in temperature creates such a condition which in turn increases the temperature again.

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the Input capacitance of the Common – Emitter Amplifier.

Concept:

The increase in collector current with an increase in collector-emitter voltage is called as ‘Early Effect’.

The characteristic curve of Ic vs. VCE will no longer be constant and will be as shown:

When we have to consider the small-signal output resistance associated with the collector current, it is given as:

\({r_0} = \frac{{\partial {V_C}}}{{\partial {I_C}}} = \frac{{{V_A}}}{{{I_C}}}\)

V_A = early voltage

I_C = DC collector current

Calculation:

Given, r₀ = 50 kΩ

|V_A| = 50 V

We can write:

\(50k = \frac{{50}}{{{I_C}}}\)

I_C = 1 mA

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the Input capacitance of the Common – Emitter Amplifier.

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width (base narrowing) and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.
• Due to this the slope of the output characteristics of a transistor in CE configuration is higher than that in CB configuration.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the Input capacitance of the Common – Emitter Amplifier.

Concept:

The increase in collector current with an increase in collector-emitter voltage is called as ‘Early Effect’.

The characteristic curve of Ic vs. VCE will no longer be constant and will be as shown:

When we have to consider the small-signal output resistance associated with the collector current, it is given as:

\({r_0} = \frac{{\partial {V_C}}}{{\partial {I_C}}} = \frac{{{V_A}}}{{{I_C}}}\)

V_A = early voltage

I_C = DC collector current

Calculation:

Given, r₀ = 50 kΩ

|V_A| = 50 V

We can write:

\(50k = \frac{{50}}{{{I_C}}}\)

I_C = 1 mA

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the Input capacitance of the Common – Emitter Amplifier.

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width (base narrowing) and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.
• Due to this the slope of the output characteristics of a transistor in CE configuration is higher than that in CB configuration.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the Input capacitance of the Common – Emitter Amplifier.

Early Effect:

• A large collector base reverse bias is the reason behind the early effect manifested by BJTs.
• As reverse biasing of the collector to base junction increases, the depletion region penetrates more into the base, as the base is lightly doped.
• This reduces the effective base width and hence the concentration gradient in the base increases.
• This reduction in the effective base width causes less recombination of carriers in the base region which results in an increase in collector current. This is known as the Early effect.
• The decrease in base width causes ß to increase and hence collector current increases with collector voltage rather than staying constant.
• The slope introduced by the Early effect is almost linear with IC and the common-emitter characteristics extrapolate to an intersection with the voltage axis VA, called the Early voltage.

This is explained with the help of the following VCE (Reverse voltage) vs IC (Collector current) curve:

Hall Effect:

Hall Effect is a production of voltage (known as hall voltage) across conductor transverse to an electric current and to an applied magnetic field perpendicular to the current.

Applications of Hall Effect:

• To determine the type of semiconductor
• To calculate the carrier concentration
• To determine mobility (hall mobility)
• To Measure magnetic flux density

Zener Effect: Zener effect occurs in a reversed biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band.

Miller Effect: The miller effect causes an increase in the input capacitance of the Common – Emitter Amplifier.

Thermal runaway: Thermal runaway is a self-destruction process in which an increase in temperature creates such a condition which in turn increases the temperature again.

Explanation:

A common-base (CB) configuration of a Bipolar Junction Transistor (BJT) is one of the three basic transistor configurations, where the base terminal is common to both the input and output circuits. It is often used in high-frequency applications due to its low input impedance and high output impedance.

Output Characteristics: The output characteristics of a CB configuration are typically plotted between the output current (collector current, I_C) and the output voltage (voltage across the collector and base terminals, V_CB) for different levels of input current (emitter current, I_E). These characteristics provide important insights into the transistor's behavior and operational regions.

Characteristics:

• The graph typically consists of three regions: the cutoff region, the active region, and the saturation region.
• In the active region, I_C remains approximately constant for a given I_E, even as V_CB increases. This is because the transistor is operating as an amplifier in this region.
• However, due to the Early effect, there is a slight increase in I_C with increasing V_CB, as the effective base width decreases, leading to a higher collector current.

Correct Option Analysis:

The correct option is:

Option 3: In a CB configuration, the current gain is slightly greater than one.

This option is incorrect. In a common-base configuration, the current gain (denoted as α) is defined as the ratio of the collector current (I_C) to the emitter current (I_E). Since a small portion of the emitter current is lost as base current (I_B), the current gain is always slightly less than 1. Mathematically: α = IC / IE, where α < 1.

Typical values of α range from 0.95 to 0.99 for most BJTs, depending on their design and manufacturing process. Therefore, the statement that the current gain is slightly greater than one is factually incorrect