Electronics Basics Quiz

1. What is the primary function of a capacitor in an electronic circuit?

To amplify signals

To store electrical energy

To decrease voltage

To control the current flow

A capacitor's primary role in electronic circuits is to store electrical energy temporarily. It functions by accumulating charge on its plates when connected to a power source. The amount of electrical charge a capacitor can store is measured in farads. Capacitors are crucial in various applications within electronic circuits, including smoothing out voltage fluctuations in power supplies, blocking direct current while allowing alternating current to pass, and in timing applications where they charge and discharge at known rates. Options A, C, and D do not accurately describe the fundamental function of capacitors in circuits.

Explanation

A capacitor's primary role in electronic circuits is to store electrical energy temporarily. It functions by accumulating charge on its plates when connected to a power source. The amount of electrical charge a capacitor can store is measured in farads. Capacitors are crucial in various applications within electronic circuits, including smoothing out voltage fluctuations in power supplies, blocking direct current while allowing alternating current to pass, and in timing applications where they charge and discharge at known rates. Options A, C, and D do not accurately describe the fundamental function of capacitors in circuits.

2. MOSFET is _____ device

Voltage controlled

Current controlled

Capacitance controlled

None of the above

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is fundamentally a voltage-controlled device. This means that the operation and behavior of the MOSFET are primarily influenced by the voltage applied at its gate terminal relative to its source terminal. The gate voltage determines the conductivity of the channel between the drain and source terminals, effectively controlling the flow of current through the device. Unlike bipolar junction transistors (BJTs) that are current-controlled, the MOSFET's gate capacitance allows it to be responsive to voltage changes without the need for a significant input current, making it highly efficient for various switching and amplification applications in electronic circuits. This voltage control capability allows MOSFETs to be used effectively in circuits where high input impedance and fast switching characteristics are desirable.

Explanation

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is fundamentally a voltage-controlled device. This means that the operation and behavior of the MOSFET are primarily influenced by the voltage applied at its gate terminal relative to its source terminal. The gate voltage determines the conductivity of the channel between the drain and source terminals, effectively controlling the flow of current through the device. Unlike bipolar junction transistors (BJTs) that are current-controlled, the MOSFET's gate capacitance allows it to be responsive to voltage changes without the need for a significant input current, making it highly efficient for various switching and amplification applications in electronic circuits. This voltage control capability allows MOSFETs to be used effectively in circuits where high input impedance and fast switching characteristics are desirable.

3. What is the value of a six-band resistor, which has band color Blue, Green, Black, Orange, Violet, Brown?

65KΩ, ± 0.10%, Temp co-efficient 100ppm/°C

650KΩ, ± 0.10%, Temp co-efficient 100ppm/°C

560KΩ, ± 0.25%, Temp co-efficient 50ppm/°C

650KΩ, ± 0.50%, Temp co-efficient 250ppm/°C

To determine the value of a six-band resistor with the color bands Blue, Green, Black, Orange, Violet, and Brown, you decode each band in sequence. The first three bands represent significant digits where Blue is 6, Green is 5, and Black is 0, forming the number 650. The fourth band, Orange, indicates a multiplier of 1,000, turning 650 into 650,000 ohms or 650KΩ. The fifth band, Violet, specifies a very precise tolerance of ± 0.10%, and the sixth band, Brown, denotes a temperature coefficient of 100 ppm/°C. Hence, the complete specifications of the resistor are 650KΩ with a tolerance of ± 0.10% and a temperature coefficient of 100 ppm/°C, useful in applications requiring precise resistance control over varying temperatures.

Explanation

To determine the value of a six-band resistor with the color bands Blue, Green, Black, Orange, Violet, and Brown, you decode each band in sequence. The first three bands represent significant digits where Blue is 6, Green is 5, and Black is 0, forming the number 650. The fourth band, Orange, indicates a multiplier of 1,000, turning 650 into 650,000 ohms or 650KΩ. The fifth band, Violet, specifies a very precise tolerance of ± 0.10%, and the sixth band, Brown, denotes a temperature coefficient of 100 ppm/°C. Hence, the complete specifications of the resistor are 650KΩ with a tolerance of ± 0.10% and a temperature coefficient of 100 ppm/°C, useful in applications requiring precise resistance control over varying temperatures.

4. What does RTL stands for in logic circuit?

Register transistor logic

Resister transistor logic

Register transformer logic

Resister transmitter logic

RTL stands for "Resistor Transistor Logic." It is a class of digital circuits built using resistors as the input network and bipolar junction transistors (BJTs) as switching devices. RTL is one of the earliest transistorized logic families and was used extensively in the design of early digital circuits. In these circuits, resistors are used to combine signals and control input currents to transistors, which function as switches. The logic family operates primarily on the principles of how these resistors and transistors interact to perform logical operations such as AND, OR, NOT, etc. The design is known for its simplicity and cost-effectiveness, although it is generally slower and consumes more power compared to more modern logic families such as TTL (Transistor-Transistor Logic) and CMOS. The other options provided, such as "Register transistor logic" and "Register transformer logic," do not represent commonly recognized logic circuit terminologies.

Explanation

RTL stands for "Resistor Transistor Logic." It is a class of digital circuits built using resistors as the input network and bipolar junction transistors (BJTs) as switching devices. RTL is one of the earliest transistorized logic families and was used extensively in the design of early digital circuits. In these circuits, resistors are used to combine signals and control input currents to transistors, which function as switches. The logic family operates primarily on the principles of how these resistors and transistors interact to perform logical operations such as AND, OR, NOT, etc. The design is known for its simplicity and cost-effectiveness, although it is generally slower and consumes more power compared to more modern logic families such as TTL (Transistor-Transistor Logic) and CMOS. The other options provided, such as "Register transistor logic" and "Register transformer logic," do not represent commonly recognized logic circuit terminologies.

5. Which of the following is true about the resistance of a Zener diode?

It has an incremental resistance

It has dynamic resistance

The value of the resistance is the inverse of the slope of the i-v characteristics of the Zener diode

All of the above

The resistance of a Zener diode is characterized by several interrelated properties: it has incremental resistance, dynamic resistance, and its value can be defined as the inverse of the slope of its current-voltage (I-V) characteristics in the Zener or reverse breakdown region. Incremental resistance refers to how the voltage across the diode changes with a change in current, and dynamic resistance describes the resistance at a specific operating point, considering small variations around this point. The mathematical expression of the diode's resistance as the inverse of the slope of the I-V curve provides a precise quantitative measure. These characteristics are essential for understanding how the Zener diode behaves under varying electrical conditions, particularly for applications in voltage regulation where stability and response to changes are critical.

Explanation

The resistance of a Zener diode is characterized by several interrelated properties: it has incremental resistance, dynamic resistance, and its value can be defined as the inverse of the slope of its current-voltage (I-V) characteristics in the Zener or reverse breakdown region. Incremental resistance refers to how the voltage across the diode changes with a change in current, and dynamic resistance describes the resistance at a specific operating point, considering small variations around this point. The mathematical expression of the diode's resistance as the inverse of the slope of the I-V curve provides a precise quantitative measure. These characteristics are essential for understanding how the Zener diode behaves under varying electrical conditions, particularly for applications in voltage regulation where stability and response to changes are critical.

6. If input frequency is 50Hz for a full wave rectifier, the ripple frequency of it would be

100Hz

50Hz

25Hz

500Hz

In a full-wave rectifier, the input AC frequency is effectively doubled in terms of the ripple frequency observed at the output. This happens because the full-wave rectifier converts both the positive and the negative halves of the AC waveform into positive voltage. For instance, if the input AC frequency is 50Hz, then each half-cycle lasts for 10 milliseconds, and since the full-wave rectifier inverts every negative half-cycle to positive, you get two cycles of output for every cycle of input. This doubling effect changes the frequency of the ripple at the output to 100Hz. Therefore, for an input frequency of 50Hz, the ripple frequency in a full-wave rectifier will be 100Hz, effectively making the output smoother compared to half-wave rectification and reducing the effort needed for further filtration.

Explanation

In a full-wave rectifier, the input AC frequency is effectively doubled in terms of the ripple frequency observed at the output. This happens because the full-wave rectifier converts both the positive and the negative halves of the AC waveform into positive voltage. For instance, if the input AC frequency is 50Hz, then each half-cycle lasts for 10 milliseconds, and since the full-wave rectifier inverts every negative half-cycle to positive, you get two cycles of output for every cycle of input. This doubling effect changes the frequency of the ripple at the output to 100Hz. Therefore, for an input frequency of 50Hz, the ripple frequency in a full-wave rectifier will be 100Hz, effectively making the output smoother compared to half-wave rectification and reducing the effort needed for further filtration.

7. MOSFET can be used as a

Current controlled capacitor

Voltage controlled capacitor

Current controlled inductor

Voltage controlled inductor

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) can be used as a voltage controlled capacitor. This is because the capacitance of a MOSFET can be controlled by varying the voltage applied to the gate terminal. By adjusting the gate voltage, the depletion region in the MOSFET can be modified, thereby changing the effective capacitance. This property makes MOSFETs suitable for applications where variable capacitance is required, such as in voltage-controlled oscillators or frequency synthesizers.

Explanation

A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) can be used as a voltage controlled capacitor. This is because the capacitance of a MOSFET can be controlled by varying the voltage applied to the gate terminal. By adjusting the gate voltage, the depletion region in the MOSFET can be modified, thereby changing the effective capacitance. This property makes MOSFETs suitable for applications where variable capacitance is required, such as in voltage-controlled oscillators or frequency synthesizers.

8. In a 6 band color code the, what does the 6th band represent?

Multiplier

Tolerance

Temperature Coefficient

None of these

In the context of a resistor with a 6-band color code, the sixth band represents the temperature coefficient. This coefficient indicates how much the resistance of the component is expected to change with temperature variations. The temperature coefficient is usually expressed in parts per million per degree Celsius (ppm/°C). This specific information is crucial for applications where resistors must perform accurately under varying thermal conditions, as it allows engineers to understand and predict the behavior of the resistor with changes in temperature. Unlike the other bands which might indicate the resistor's value (multiplier), tolerance, and in some cases reliability or failure rate, the sixth band specifically addresses how temperature impacts the resistor's performance, thereby assisting in achieving more precise and reliable circuit designs, especially in temperature-sensitive applications.0

Explanation

In the context of a resistor with a 6-band color code, the sixth band represents the temperature coefficient. This coefficient indicates how much the resistance of the component is expected to change with temperature variations. The temperature coefficient is usually expressed in parts per million per degree Celsius (ppm/°C). This specific information is crucial for applications where resistors must perform accurately under varying thermal conditions, as it allows engineers to understand and predict the behavior of the resistor with changes in temperature. Unlike the other bands which might indicate the resistor's value (multiplier), tolerance, and in some cases reliability or failure rate, the sixth band specifically addresses how temperature impacts the resistor's performance, thereby assisting in achieving more precise and reliable circuit designs, especially in temperature-sensitive applications.0

9.

Consider a 4 bit binary no. 1010. A,B,C are the decimal integers representation of 4 bit binary no.1010 where A=signed magnitude, B=1’s compliment and C=2’s compliment of binary no. What is the 1’s complement of (A+B+C)

0110

1100

0111

1110

The 1's complement of a binary number is obtained by flipping all the bits in the number. In this case, we have A=1010 (signed magnitude), B=1100 (1's complement), and C=1110 (2's complement) of the binary number 1010. To find the 1's complement of (A+B+C), we need to add A, B, and C together and then flip all the bits. Adding A, B, and C gives us 1010 + 1100 + 1110 = 0100. Flipping all the bits in 0100 gives us 0110, which is the 1's complement of (A+B+C).

Explanation

The 1's complement of a binary number is obtained by flipping all the bits in the number. In this case, we have A=1010 (signed magnitude), B=1100 (1's complement), and C=1110 (2's complement) of the binary number 1010. To find the 1's complement of (A+B+C), we need to add A, B, and C together and then flip all the bits. Adding A, B, and C gives us 1010 + 1100 + 1110 = 0100. Flipping all the bits in 0100 gives us 0110, which is the 1's complement of (A+B+C).

10. Which power management device is considered to be uncontrolled device?

MOSFET

IGBT

Diode

BJT

A diode is considered an uncontrolled device because it does not have the capability to control its conduction state through an external control signal. Unlike MOSFETs, IGBTs, and BJTs, which are all controlled devices featuring gate or base terminals where a voltage or current can be applied to control the flow of electricity through them, a diode conducts electricity in one direction automatically when the voltage across it exceeds a certain threshold (forward-biased condition) and blocks current in the opposite direction (reverse-biased condition). The action of a diode is thus inherently determined by its intrinsic properties and the external voltage applied across it, without any additional external control input influencing its operation. This makes the diode a fundamental component for simple rectification tasks, acting purely based on the electrical characteristics of the circuit in which it is placed, thereby categorizing it as an uncontrolled device in power management contexts.

Explanation

A diode is considered an uncontrolled device because it does not have the capability to control its conduction state through an external control signal. Unlike MOSFETs, IGBTs, and BJTs, which are all controlled devices featuring gate or base terminals where a voltage or current can be applied to control the flow of electricity through them, a diode conducts electricity in one direction automatically when the voltage across it exceeds a certain threshold (forward-biased condition) and blocks current in the opposite direction (reverse-biased condition). The action of a diode is thus inherently determined by its intrinsic properties and the external voltage applied across it, without any additional external control input influencing its operation. This makes the diode a fundamental component for simple rectification tasks, acting purely based on the electrical characteristics of the circuit in which it is placed, thereby categorizing it as an uncontrolled device in power management contexts.

11. What is necessary to use in order to prevent a DC return between source and load?

Resistor between source and load

Inductor between source and load

Capacitor between source and load

Both 1 and 2

To prevent a DC return, or DC leakage, between a source and a load in electronic circuits, a capacitor is typically employed, known as a coupling or DC blocking capacitor. This component is crucial for blocking direct current while permitting alternating current signals to pass, thus maintaining the integrity of AC signals without the interference of any DC components. Capacitors achieve this by charging up to the DC voltage and then acting as an open circuit to any further DC flow, effectively isolating the DC component from the circuit while allowing AC signals to transmit. This is particularly vital in applications like audio and radio frequency circuits, where pure signal transmission is necessary. In contrast, resistors do not block DC, and inductors, while blocking high-frequency AC, allow DC to pass, making capacitors the optimal choice for preventing DC return in these scenarios.

Explanation

To prevent a DC return, or DC leakage, between a source and a load in electronic circuits, a capacitor is typically employed, known as a coupling or DC blocking capacitor. This component is crucial for blocking direct current while permitting alternating current signals to pass, thus maintaining the integrity of AC signals without the interference of any DC components. Capacitors achieve this by charging up to the DC voltage and then acting as an open circuit to any further DC flow, effectively isolating the DC component from the circuit while allowing AC signals to transmit. This is particularly vital in applications like audio and radio frequency circuits, where pure signal transmission is necessary. In contrast, resistors do not block DC, and inductors, while blocking high-frequency AC, allow DC to pass, making capacitors the optimal choice for preventing DC return in these scenarios.

12. Leakage current in a transistor mainly depends on

Doping of base

Size of emitter

Rating of the transistor

Temperature

Leakage current in a transistor, particularly in bipolar junction transistors (BJTs) and field-effect transistors (FETs), is influenced significantly by temperature. As temperature increases, so does the energy of the charge carriers (electrons and holes) within the semiconductor material. This increase in energy enhances their ability to cross the potential barriers within the transistor structure, such as the emitter-base junction in a BJT or the gate in an FET.

In simpler terms, at higher temperatures, more electrons have enough energy to move where they usually wouldn't at lower temperatures, leading to an increase in leakage current. This leakage is the small amount of current that flows from the collector to the emitter in a BJT, or from drain to source in an FET, even when the transistor is supposed to be off. This unwanted current is a key factor in power dissipation and can affect the performance and reliability of electronic devices, particularly as devices are miniaturized and their operating temperatures vary. The doping of the base, size of the emitter, and the rating of the transistor do influence other characteristics such as gain, threshold voltage, and maximum current capacity, but when specifically talking about leakage current, temperature is the predominant factor.

Explanation

Leakage current in a transistor, particularly in bipolar junction transistors (BJTs) and field-effect transistors (FETs), is influenced significantly by temperature. As temperature increases, so does the energy of the charge carriers (electrons and holes) within the semiconductor material. This increase in energy enhances their ability to cross the potential barriers within the transistor structure, such as the emitter-base junction in a BJT or the gate in an FET.

In simpler terms, at higher temperatures, more electrons have enough energy to move where they usually wouldn't at lower temperatures, leading to an increase in leakage current. This leakage is the small amount of current that flows from the collector to the emitter in a BJT, or from drain to source in an FET, even when the transistor is supposed to be off. This unwanted current is a key factor in power dissipation and can affect the performance and reliability of electronic devices, particularly as devices are miniaturized and their operating temperatures vary. The doping of the base, size of the emitter, and the rating of the transistor do influence other characteristics such as gain, threshold voltage, and maximum current capacity, but when specifically talking about leakage current, temperature is the predominant factor.

13. In the making of an amplifier if a MOSFET is to be used, then it must work in

Cut-off region

Saturation region

Triode region

Both cut-off and triode region can be used

In the context of using a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) in an amplifier circuit, it is essential for the MOSFET to operate within the saturation region to function effectively as an amplifier. This region, often called the active region, allows the MOSFET to act as a controlled current source, which is crucial for achieving stable and linear amplification with a constant amplification factor or gain. Operating in the saturation region ensures that the device maintains the required conditions for V_DS (voltage between drain and source) and V_GS (voltage between gate and source) so that it can amplify the input signal accurately without distortion. In contrast, other regions like the triode or cut-off regions would lead to non-ideal behavior such as resistive behavior or no current flow, respectively, which are not conducive to reliable signal amplification in standard amplifier designs.

Explanation

In the context of using a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) in an amplifier circuit, it is essential for the MOSFET to operate within the saturation region to function effectively as an amplifier. This region, often called the active region, allows the MOSFET to act as a controlled current source, which is crucial for achieving stable and linear amplification with a constant amplification factor or gain. Operating in the saturation region ensures that the device maintains the required conditions for V_DS (voltage between drain and source) and V_GS (voltage between gate and source) so that it can amplify the input signal accurately without distortion. In contrast, other regions like the triode or cut-off regions would lead to non-ideal behavior such as resistive behavior or no current flow, respectively, which are not conducive to reliable signal amplification in standard amplifier designs.

14. Which one in the following image will block voltage of either polarity when device is OFF

(ii),(iii) and (iv)

(ii) and (iii)

(i) and (iv)

(i),(ii) and (iii)

The correct answer is (ii) and (iii).

Diodes act like one-way streets for electricity. They allow current in one direction (forward bias) but block it in the other (reverse bias).

In options (ii) and (iii), when the device is OFF, the diodes are in reverse bias. This means electricity can't flow through them in either direction, blocking voltage regardless of its polarity (positive or negative).

Options (i) and (iv) have diodes in forward bias when OFF, allowing current to flow and not blocking voltage

Explanation

The correct answer is (ii) and (iii).

Diodes act like one-way streets for electricity. They allow current in one direction (forward bias) but block it in the other (reverse bias).

In options (ii) and (iii), when the device is OFF, the diodes are in reverse bias. This means electricity can't flow through them in either direction, blocking voltage regardless of its polarity (positive or negative).

Options (i) and (iv) have diodes in forward bias when OFF, allowing current to flow and not blocking voltage

15. DC DC conversion can be achieved using: (i) Rectifier (ii) Inverter (iii) Chopper (iv) Cyclo converter

Combination of (i) and (iv)

Combination of (ii) and (iv)

Combination of (ii) and (iii)

Combination of (ii) and (i)

DC-DC conversion, which involves changing one DC voltage level to another, can be efficiently achieved using inverters and choppers. Inverters can convert DC to AC, adjust the voltage level through transformation, and then revert it back to DC at a different voltage, whereas choppers directly alter DC voltage levels by rapidly switching the current on and off. This combination provides a versatile and efficient means for managing DC-DC conversion, suitable for a variety of applications such as motor speed control, power supply systems, and electric vehicles. Other options like rectifiers and cycloconverters do not typically facilitate DC-DC conversion, as they are used for converting AC to DC and changing AC frequencies, respectively.

Explanation

DC-DC conversion, which involves changing one DC voltage level to another, can be efficiently achieved using inverters and choppers. Inverters can convert DC to AC, adjust the voltage level through transformation, and then revert it back to DC at a different voltage, whereas choppers directly alter DC voltage levels by rapidly switching the current on and off. This combination provides a versatile and efficient means for managing DC-DC conversion, suitable for a variety of applications such as motor speed control, power supply systems, and electric vehicles. Other options like rectifiers and cycloconverters do not typically facilitate DC-DC conversion, as they are used for converting AC to DC and changing AC frequencies, respectively.

16. For a pnp transistor in the active region the value of Vce (potential difference between the collector and the base) is

Less than 0.3V

Less than 3V

Greater than 0.3V

Greater than 3V

For a PNP transistor to operate effectively in its active region, where it functions as an amplifier, the voltage VCE (voltage between the collector and emitter) should typically be greater than 0.3V. This ensures that the base-collector junction remains reverse-biased and the base-emitter junction forward-biased, maintaining the transistor's ability to control the flow of charge carriers based on the input at the base. Maintaining VCE above 0.3V prevents the transistor from entering saturation, a state where it would act more like a switch than an amplifier, allowing maximum current flow regardless of base input. This configuration allows for effective signal amplification with linearity, crucial for various electronic applications where precise control over signal output is needed.

Explanation

For a PNP transistor to operate effectively in its active region, where it functions as an amplifier, the voltage VCE (voltage between the collector and emitter) should typically be greater than 0.3V. This ensures that the base-collector junction remains reverse-biased and the base-emitter junction forward-biased, maintaining the transistor's ability to control the flow of charge carriers based on the input at the base. Maintaining VCE above 0.3V prevents the transistor from entering saturation, a state where it would act more like a switch than an amplifier, allowing maximum current flow regardless of base input. This configuration allows for effective signal amplification with linearity, crucial for various electronic applications where precise control over signal output is needed.

17. Which of the following is true for a pnp transistor in saturation region?

CB junction is reversed bias and the EB junction is forward bias

CB junction is forward bias and the EB junction is forward bias

CB junction is forward bias and the EB junction is reverse bias

CB junction is reversed bias and the EB junction is reverse bias

In a PNP transistor operating in the saturation region, both the collector-base (CB) junction and the emitter-base (EB) junction are forward-biased. This configuration allows for maximum current flow through the transistor, akin to a closed switch, facilitating charge carriers (holes for PNP) to move freely across both junctions. This saturation mode contrasts with the active region where the CB junction is typically reverse-biased to control the transistor's operations for signal amplification. Saturation is particularly useful in switching applications where low on-state voltage is crucial, even though it is not ideal for tasks requiring control over the current flow, such as amplification.

Explanation

In a PNP transistor operating in the saturation region, both the collector-base (CB) junction and the emitter-base (EB) junction are forward-biased. This configuration allows for maximum current flow through the transistor, akin to a closed switch, facilitating charge carriers (holes for PNP) to move freely across both junctions. This saturation mode contrasts with the active region where the CB junction is typically reverse-biased to control the transistor's operations for signal amplification. Saturation is particularly useful in switching applications where low on-state voltage is crucial, even though it is not ideal for tasks requiring control over the current flow, such as amplification.

18. In which mode MOSFET/BJT used as a switch (i) Saturation (ii) Cut off (iii) Active (iv) Reverse active

(i) and (iii)

(ii) and (iii)

(i) and (ii)

(i), (ii) and (iii)

MOSFETs and BJTs are effectively used as switches in electronic circuits, operating primarily in two modes: saturation and cut-off. In the saturation mode, the device is fully 'on,' allowing maximum current to flow, which is true for both BJTs (where both junctions are forward-biased) and MOSFETs (where the gate-source voltage is above a threshold). In cut-off mode, the device is 'off,' with no current flowing due to insufficient biasing in BJTs and a gate-source voltage below the threshold in MOSFETs. These modes enable the device to switch between fully 'on' and 'off' states, crucial for binary operations in digital circuits. Active and reverse active modes, while important for other applications like amplification, are not suited for switching as they do not provide definitive on or off states. Thus, the saturation and cut-off modes are essential for the efficient and clear operation of transistors as switches.

Explanation

MOSFETs and BJTs are effectively used as switches in electronic circuits, operating primarily in two modes: saturation and cut-off. In the saturation mode, the device is fully 'on,' allowing maximum current to flow, which is true for both BJTs (where both junctions are forward-biased) and MOSFETs (where the gate-source voltage is above a threshold). In cut-off mode, the device is 'off,' with no current flowing due to insufficient biasing in BJTs and a gate-source voltage below the threshold in MOSFETs. These modes enable the device to switch between fully 'on' and 'off' states, crucial for binary operations in digital circuits. Active and reverse active modes, while important for other applications like amplification, are not suited for switching as they do not provide definitive on or off states. Thus, the saturation and cut-off modes are essential for the efficient and clear operation of transistors as switches.

19. The point C is stuck at '1'. The output at O will be

AMB

AM

M

M(bar)

When a point in a digital circuit, such as point C, is "stuck at ‘1’," it affects the overall logic of the circuit by always outputting a high signal. This fault changes how other logic gates process outputs, particularly when C is part of an operation. For instance, in an AND operation like A AND B AND C, the outcome now only depends on A and B, since C's constant high makes its intended state irrelevant. In scenarios where C is part of an OR operation (e.g., A OR C), the output becomes perpetually high, nullifying other input effects. Given the answer choices that involve C's interaction with other signals (AMB, AM), and those that suggest independence from it (M, M(bar)), the answer M indicates that the output O relies solely on M, independent of the stuck-at condition at C. This highlights how such faults can drastically shift a circuit’s functionality and underscores the importance of meticulous design and testing to manage and detect such faults efficiently.

Explanation

When a point in a digital circuit, such as point C, is "stuck at ‘1’," it affects the overall logic of the circuit by always outputting a high signal. This fault changes how other logic gates process outputs, particularly when C is part of an operation. For instance, in an AND operation like A AND B AND C, the outcome now only depends on A and B, since C's constant high makes its intended state irrelevant. In scenarios where C is part of an OR operation (e.g., A OR C), the output becomes perpetually high, nullifying other input effects. Given the answer choices that involve C's interaction with other signals (AMB, AM), and those that suggest independence from it (M, M(bar)), the answer M indicates that the output O relies solely on M, independent of the stuck-at condition at C. This highlights how such faults can drastically shift a circuit’s functionality and underscores the importance of meticulous design and testing to manage and detect such faults efficiently.

20. To obtain 2μF capacity from three capacitors of 2μF each, they will be arranged

All the three in series

All the three in parallel

Two capacitors in series and the third in parallel with the combination of first two

Two capacitors in parallel and the third in series with the combination of first two

To achieve a total capacitance of 2μF using three 2μF capacitors, the question suggests connecting them in different configurations. However, due to an apparent oversight in the question, achieving exactly 2μF is not possible with three 2μF capacitors without reducing the effective capacitance through series configurations, which wasn't correctly reflected in the options. The correct method to combine them for maximum capacitance is to connect all three capacitors in parallel. This setup would actually result in a total capacitance of 6μF (2μF + 2μF + 2μF), not 2μF, indicating either a typo in the desired capacitance value or an error in the setup options provided. Connecting capacitors in parallel adds their capacitances, ideal for increasing capacitance in a circuit, while series connections reduce it, which was not an option aligned to achieve the stated goal correctly.

Explanation

To achieve a total capacitance of 2μF using three 2μF capacitors, the question suggests connecting them in different configurations. However, due to an apparent oversight in the question, achieving exactly 2μF is not possible with three 2μF capacitors without reducing the effective capacitance through series configurations, which wasn't correctly reflected in the options. The correct method to combine them for maximum capacitance is to connect all three capacitors in parallel. This setup would actually result in a total capacitance of 6μF (2μF + 2μF + 2μF), not 2μF, indicating either a typo in the desired capacitance value or an error in the setup options provided. Connecting capacitors in parallel adds their capacitances, ideal for increasing capacitance in a circuit, while series connections reduce it, which was not an option aligned to achieve the stated goal correctly.

21. In nodal analysis, if there are N nodes in the circuit then how many equations will be written to solve the network?

N - 1

N

N + 1

N – 2

In nodal analysis, which is a systematic method used to determine the voltages at various points or nodes in an electrical circuit, the number of independent equations that need to be formulated corresponds to the number of nodes minus one, which is N−1. This count excludes the reference node (often called the ground node) which is used to define the zero potential level in the circuit.

The rationale behind this is based on Kirchhoff’s Current Law (KCL), which states that the total current entering a node (excluding the ground node) must equal the total current leaving the node. As the voltage at the reference node is zero by definition, it does not require an equation. Therefore, only N−1 nodes actually require analysis for their voltages relative to the reference node. This technique efficiently simplifies the process of analyzing complex circuits by reducing the number of equations needed to solve for all unknown node voltages, thereby making the problem manageable and more straightforward to solve.

Explanation

In nodal analysis, which is a systematic method used to determine the voltages at various points or nodes in an electrical circuit, the number of independent equations that need to be formulated corresponds to the number of nodes minus one, which is N−1. This count excludes the reference node (often called the ground node) which is used to define the zero potential level in the circuit.

The rationale behind this is based on Kirchhoff’s Current Law (KCL), which states that the total current entering a node (excluding the ground node) must equal the total current leaving the node. As the voltage at the reference node is zero by definition, it does not require an equation. Therefore, only N−1 nodes actually require analysis for their voltages relative to the reference node. This technique efficiently simplifies the process of analyzing complex circuits by reducing the number of equations needed to solve for all unknown node voltages, thereby making the problem manageable and more straightforward to solve.

22.

The Output will always be '1' when

Two or more of the inputs A,B,C are ‘0’

Two or more of the inputs A,B,C are ‘1’

Any odd no. of the inputs A, B, C are ‘0’

Any odd no. of the inputs A, B, C are ‘1’

The scenario where the output is always ‘1’ when any odd number of the inputs A, B, C are '1' describes the behavior of a three-input XOR gate. This gate, known for implementing odd parity checks, outputs a '1' if the total number of '1's among the inputs is odd. Here’s a breakdown for clarity:

If one input is '1', the others being '0', the output is '1' because there's an odd count of '1's.

Similarly, if all three inputs are '1', the output remains '1', fitting the condition of having an odd number of '1's.

For any even number of '1's among the inputs (zero, two), the output is '0'.

This logic confirms that the output behavior aligns specifically with the XOR operation. XOR gates are used extensively in digital electronics to perform functions such as parity checking and arithmetic operations, where distinguishing between odd and even numbers of '1's is crucial. Thus, the condition "any odd number of the inputs A, B, C are ‘1’" directly matches the fundamental XOR logic operation for three inputs.

Explanation

The scenario where the output is always ‘1’ when any odd number of the inputs A, B, C are '1' describes the behavior of a three-input XOR gate. This gate, known for implementing odd parity checks, outputs a '1' if the total number of '1's among the inputs is odd. Here’s a breakdown for clarity:

If one input is '1', the others being '0', the output is '1' because there's an odd count of '1's.

Similarly, if all three inputs are '1', the output remains '1', fitting the condition of having an odd number of '1's.

For any even number of '1's among the inputs (zero, two), the output is '0'.

This logic confirms that the output behavior aligns specifically with the XOR operation. XOR gates are used extensively in digital electronics to perform functions such as parity checking and arithmetic operations, where distinguishing between odd and even numbers of '1's is crucial. Thus, the condition "any odd number of the inputs A, B, C are ‘1’" directly matches the fundamental XOR logic operation for three inputs.

23. Inverter gates can be developed using

Two diodes

A capacitor and inductor

A transistor

A capacitor and resistor

Inverter gates, also known as NOT gates, are primarily developed using a single transistor, either a MOSFET or a BJT, due to their ability to function as switches. The transistor in an inverter configuration inverts the input signal, producing an output that is the logical opposite of the input. This is achieved by the transistor switching on or off in response to the input voltage, controlling the current flow from the power supply to the ground. When the input is high, the transistor conducts and pulls the output low, and when the input is low, the transistor does not conduct, allowing the output to be pulled high through a connected pull-up resistor. This simple yet effective mechanism underscores the practical use of transistors in digital logic circuits over other components like diodes or combinations of capacitors and resistors, which lack the necessary switching capability for such operations.

Explanation

Inverter gates, also known as NOT gates, are primarily developed using a single transistor, either a MOSFET or a BJT, due to their ability to function as switches. The transistor in an inverter configuration inverts the input signal, producing an output that is the logical opposite of the input. This is achieved by the transistor switching on or off in response to the input voltage, controlling the current flow from the power supply to the ground. When the input is high, the transistor conducts and pulls the output low, and when the input is low, the transistor does not conduct, allowing the output to be pulled high through a connected pull-up resistor. This simple yet effective mechanism underscores the practical use of transistors in digital logic circuits over other components like diodes or combinations of capacitors and resistors, which lack the necessary switching capability for such operations.

24. What is hysteresis?

Lead between cause and effect

Lag between cause and effect

Lead between voltage and current

Lag between voltage and current

Hysteresis refers to the phenomenon where there is a lag between the cause and its effect. This concept is commonly observed in various physical and engineering systems, such as magnetic materials, mechanical systems, and electronic circuits. In the context of magnetic materials, hysteresis describes how the magnetic flux density (B) lags behind changes in the magnetizing force (H). This lag creates a hysteresis loop in the B-H curve when the material is subjected to a cyclic magnetic field. Similarly, in thermostats and electronic circuits, hysteresis is employed to prevent rapid switching or oscillation around a trigger point, ensuring that once a certain condition is met, the state does not change again until the initiating factor reverses by a significant amount. This property helps in stabilizing systems and preventing unwanted frequent changes that could be caused by minor fluctuations around the threshold. Thus, hysteresis essentially embodies a lag between the input or cause and the output or effect, stabilizing the system's response to changes.

Explanation

Hysteresis refers to the phenomenon where there is a lag between the cause and its effect. This concept is commonly observed in various physical and engineering systems, such as magnetic materials, mechanical systems, and electronic circuits. In the context of magnetic materials, hysteresis describes how the magnetic flux density (B) lags behind changes in the magnetizing force (H). This lag creates a hysteresis loop in the B-H curve when the material is subjected to a cyclic magnetic field. Similarly, in thermostats and electronic circuits, hysteresis is employed to prevent rapid switching or oscillation around a trigger point, ensuring that once a certain condition is met, the state does not change again until the initiating factor reverses by a significant amount. This property helps in stabilizing systems and preventing unwanted frequent changes that could be caused by minor fluctuations around the threshold. Thus, hysteresis essentially embodies a lag between the input or cause and the output or effect, stabilizing the system's response to changes.

25. The output of LM7905 voltage regulator IC is

-9V

5V

12V

None of the above

The LM7905 is a type of voltage regulator IC specifically designed to provide a fixed negative output voltage. This particular model, the LM7905, outputs -5 volts. The "79" in the model number typically signifies a negative voltage regulator, and the last two digits "05" indicate the output voltage it regulates to, which is -5 volts in this case. It’s used in various electronic applications where a stable negative voltage is required. The options listed do not correctly specify the output of the LM7905, as they suggest other voltage values that are not applicable for this specific regulator model.

Explanation

The LM7905 is a type of voltage regulator IC specifically designed to provide a fixed negative output voltage. This particular model, the LM7905, outputs -5 volts. The "79" in the model number typically signifies a negative voltage regulator, and the last two digits "05" indicate the output voltage it regulates to, which is -5 volts in this case. It’s used in various electronic applications where a stable negative voltage is required. The options listed do not correctly specify the output of the LM7905, as they suggest other voltage values that are not applicable for this specific regulator model.