Bipolar Junction Transistor Quiz! Trivia

A transistor is a semiconductor device that consists of three or more elements. It is used for amplifying or switching electronic signals and electrical power. Transistors are fundamental building blocks of modern electronic devices and are widely used in various applications such as computers, televisions, radios, and smartphones.

The majority current carriers in an NPN transistor are electrons. In an NPN transistor, the base region is doped with a material that has an excess of electrons, making it an n-type semiconductor. When a small current is applied to the base, it allows electrons to flow from the emitter to the base region. These electrons then combine with holes (absence of electrons) in the base region and continue to flow to the collector, resulting in the amplification of current. Therefore, electrons are the majority current carriers in an NPN transistor.

The term used to describe the condition in a transistor when the emitter-base junction has zero bias or is reverse biased and there is no collector current is "cutoff". In this state, the transistor is effectively turned off and does not allow any current flow through it. This is a crucial state for controlling the operation of the transistor in electronic circuits. The other options, "active" and "saturation", refer to different operating modes of a transistor where current flow is present.

The transistor became famous for its ability to amplify electrical signals. It is a key electronic function that allows the transistor to increase the strength of a weak input signal to a higher level, making it suitable for various applications such as amplifiers, radios, and computers. This amplification capability revolutionized the field of electronics and paved the way for smaller, more efficient devices.

In a PNP transistor, the majority current carriers are holes. A PNP transistor is a type of bipolar junction transistor (BJT) where the majority charge carriers are holes, which are positively charged. When a small current is applied to the base terminal, it allows the flow of holes from the emitter to the base, and then from the base to the collector. This movement of holes controls the overall current flow in the transistor. Therefore, the correct answer is "holes".

The explanation for the correct answer is that the polarity of the voltage applied to the PNP transistor is opposite to that applied to the NPN transistor. This means that if the PNP transistor is being supplied with positive voltage, the NPN transistor will be supplied with negative voltage, and vice versa. This is due to the difference in the transistor's internal structure and the way they operate.

The correct answer is "both a and b". In a transistor, there are two current loops: the base current loop and the collector current loop. The base current loop consists of the current flowing from the power supply through the base-emitter junction and returning to the power supply. The collector current loop consists of the current flowing from the power supply through the collector-emitter junction and returning to the power supply. Both these loops are essential for the proper functioning of a transistor.

In an NPN transistor, the collector current is the majority of the current that enters the base terminal. This is because the base current is very small compared to the collector current. Therefore, most of the current (approximately 98%) that flows into the transistor reaches the collector.

An amplifier is a device that increases the current, voltage, or power of a signal without significantly altering the original signal. It takes the input signal and amplifies it, allowing for a stronger output signal. Amplifiers are commonly used in audio systems, telecommunications, and many other applications where a signal needs to be boosted for better performance or transmission.

The correct answer is "point contact." The question asks for the name of the very first transistor, and the term "point contact" refers to the early type of transistor that was developed by John Bardeen and Walter Brattain at Bell Laboratories in 1947. This type of transistor used a fine wire or point to make contact with a semiconductor material, allowing for the amplification and control of electrical signals.

The arrow on an NPN transistor typically points outward. This arrow represents the direction of conventional current flow, indicating the direction in which current is expected to flow through the transistor. It serves as a reference for circuit designers and technicians to correctly connect the transistor in a circuit.

The base current or fixed bias method is the most unstable biasing method because it relies on the base current to provide the necessary biasing voltage. Any variation in the base current can cause significant changes in the operating point of the transistor, leading to instability in the circuit. In contrast, the voltage divider and emitter stabilized circuit provide more stable biasing methods as they are less dependent on the base current. Therefore, the base current or fixed bias method is the most unstable among the options provided.

In an NPN transistor, the base section is made very thin compared to the other two sections. This is because the base region is responsible for controlling the flow of current between the emitter and collector regions. By making the base section thin, it allows for better control of the current flow, making the transistor more efficient in amplifying signals.

Class A amplifiers allow collector current to flow during the complete cycle of the input. In class A operation, the transistor is biased such that it conducts current even when there is no input signal. This results in a continuous flow of current through the collector, allowing the amplifier to accurately reproduce the entire waveform of the input signal. Class A amplifiers are known for their low distortion and high linearity, but they are less efficient compared to other classes of amplifiers.

To properly bias an NPN transistor, a positive voltage is applied to the collector. This is because the collector-base junction is reverse-biased, and a positive voltage helps in maintaining this bias. Additionally, the collector voltage is required to be more positive than the base voltage. This ensures that the transistor operates in the active region, allowing for proper amplification and control of the current flowing through it.

Class B amplifiers allow collector current to flow during only half of the input cycle. In this class of operation, the input signal is split into positive and negative half-cycles, each handled by a separate transistor. One transistor conducts during the positive half-cycle, while the other conducts during the negative half-cycle. This configuration helps to improve efficiency compared to Class A amplifiers, where current flows through the transistor continuously. Class B amplifiers are commonly used in audio applications where high power efficiency is desired.

To properly bias a PNP transistor, a negative voltage is applied to the collector, and it is more negative than the base voltage. This is because PNP transistors require a reverse bias between the collector and the base to function correctly. By applying a negative voltage to the collector, it creates a potential difference with the base voltage, allowing the transistor to amplify and control the flow of current. The more negative the collector voltage is compared to the base voltage, the stronger the biasing effect and the better the transistor will operate.

The primary difference between NPN and PNP amplifiers lies in the polarity of the source voltage. In an NPN amplifier, the source voltage is positive with respect to the base, whereas in a PNP amplifier, the source voltage is negative with respect to the base. This difference in polarity affects the flow of current and the behavior of the transistors in the amplifiers.

The class of operation of an amplifier is determined by both the amount of bias and the amplitude of the input signal. The amount of bias refers to the DC voltage or current applied to the amplifier, which sets the operating point and affects the linearity and efficiency of the amplifier. The amplitude of the input signal determines the level of amplification or distortion that the amplifier will produce. Therefore, both factors play a crucial role in determining the class of operation of an amplifier.

The voltage divider or beta independent biasing method is the most stable because it provides a stable bias voltage regardless of variations in the transistor's beta value. This method uses resistors to create a voltage divider network, ensuring a constant bias voltage is applied to the base of the transistor. As a result, any changes in the transistor's beta value do not significantly affect the biasing conditions, making this method more stable compared to others.

Self bias is the type of bias used where only moderate changes in ambient temperature are expected. In self bias, a resistor is connected in series with the base-emitter junction of the transistor, which provides a stable bias voltage. This helps to maintain a consistent operating point for the transistor, even with slight variations in temperature. Therefore, self bias is suitable for applications where only moderate temperature changes are anticipated.

The direction in which the arrow points on a PNP transistor cannot be determined based solely on the given information. The arrow is used to indicate the direction of conventional current flow, which is from the emitter to the base and then to the collector in a PNP transistor. However, without additional information or a diagram, it is not possible to determine the specific direction of the arrow.

The most widely used combination-bias system is either a voltage divider type or a beta independent type. These two types of bias systems are commonly used in electronic circuits to establish the desired operating point for transistors. The voltage divider type uses a resistive network to divide the supply voltage and provide the required bias voltage, while the beta independent type uses a diode or a constant current source to establish the bias current independent of the transistor's beta value. Both of these bias systems are widely employed due to their simplicity and effectiveness in maintaining stable operating conditions for transistors.

The relationship between the polarity of the input and output signals in the basic common emitter transistor amplifier can be either opposite (a) or 180 degrees out of phase (b) with each other. This means that when the input signal is positive, the output signal will be negative, and vice versa. Alternatively, when the input signal is at its peak, the output signal will be at its lowest point, and vice versa. Therefore, the correct answer is either a or b.

In a PNP transistor, the emitter section is made very thin compared to the other two sections. This is because the emitter is responsible for injecting majority charge carriers (electrons in this case) into the base region. By making the emitter section thin, it allows for easier and more efficient injection of electrons into the base region, thereby enhancing the transistor's performance.