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NAVEDTRA 14179A
ET2 BIBS MAR 2017 EXAM
| Question | Answer |
|---|---|
| Which year was the first transistor discovered? | 1948 |
| What are semiconductor devices called that have three or more elements? | transistors |
| What were the very first transistors known as? | point-contact |
| Which type of transistor generates less noise, handles more power, provides higher current and voltage gains, and can be mass-produced more cheaply that the point-contact transistor? | junction |
| What is the process called of increasing the strength of a signal? | amplification |
| Which device provides amplification without appreciably altering the original signal? | amplifier |
| What is returning a part of the output back to its input known as? | degeneration |
| How many classes of amplifier operation are there? | four |
| Which class of amplifiers are biased so that variations in input signal polarities occur within the limits of cutoff and saturation? | class A |
| What occurs when the base becomes so negative with respect to the emitter that changes in the signal are not reflected in collector-current flow? | saturation |
| Amplifiers designed for what class of operation are biased so that collector current is zero (cutoff) for a portion of one alternation of the input signal? | class AB |
| Amplifiers biased so that collector current is cutoff during one half of the input signal are classified as what class? | class B |
| What is the faithful reproduction of a signal called? | fidelity |
| Which amplifier property refers to the ratio of output signal power compared to the total input power? | efficiency |
| Which amplifier class has the highest efficiency of the four classes of amplifier operations? | class C |
| How many basic configurations may a transistor be connected in? | three |
| What is the most frequently used arrangement in practical amplifier circuits? | common-emitter configuration (CE) |
| Which term is used to describe the amplification capabilities of the amplifier? | gain |
| What is the relationship of collector current (output current) to base current (input current)? | Beta |
| What is the relationship of collector current (output current) to emitter current (input current)? | Alpha |
| Which transistor properties are the direct voltage and current values that if exceeded in operation may result in transistor failure? | Absolute maximum ratings |
| What is one of the greatest dangers to the transistor which will cause excessive current flow and eventual destruction of the transistor? | heat |
| Gain, leakage, breakdown, along with what else are the four basic tests required for transistors in practical troubleshooting? | switching time |
| Printed circuit boards are stacked and connected together to form a module using what technique? | modular circuitry |
| Which device integrates both active components (transistors, diodes, etc.) and passive components (resistors, capacitors, etc.) of a complete electronic circuit in a single chip? | integrated circuit |
| What are the two general classifications of integrated circuits? | hybrid and monolithic |
| In which type of integrated circuits do all elements associated with the circuit fabricated inseparably within a continuous piece of material which is usually silicon? | monolithic |
| What are two terminal semiconductors of various types that are used in seemingly endless applications? | diodes |
| What is a PN junction that is designed to operate in reverse-bias breakdown region? | Zener diode |
| Which year was the zener effect first proposed by Dr. Carl Zener? | 1934 |
| What is a band in which the energy level of the electrons is high enough that the electrons will move easily under the influence of an external field? | conduction |
| What are solid materials called that have many electrons in the conduction band? | conductors |
| What is a band in which the energy level is the same as the valence electrons of the atoms? | valence band |
| What is a material in which the forbidden gap is so narrow that it can be considered non existent? | conductor |
| What is a solid that contains a forbidden gap? | semiconductor |
| What are materials in which the forbidden gap is so large that practically no electrons can be given enough energy to cross the gap? | insulators |
| What is the most widespread use of Zener diodes? | voltage regulators |
| What is the most important and widely used characteristic of the tunnel diode | negative resistance region |
| Which type of diode behaves like a variable capacitor, with the PN junction functioning like the dielectric and plates of a common capacitor? | varactor diode |
| How high can the ratio of varactor capacitance to reverse-bias voltage change be? | 10 to 1 |
| What can be used to check a varactor diode in a circuit? | ohmmeter |
| What functions as a switch that can turn on or off small or large amounts of power? | SCR |
| Some SCRs can be switched how many times a second? | 25,000 |
| The input resistance of the SCR is relatively low (appx. how many ohms) and requires a current for triggering? | 100 ohms |
| Which type of devices either produce light or use light in their operation? | optoelectronic |
| LED operating voltage is small, about 1.6v forward bias and generally about how many milliamperes? | 10 |
| What is the life expectancy of the LED? | 100,000+ hours |
| What is a light controlled variable resistor? | photodiode |
| What is a typical light-to-dark resistance ratio for a photocell? | 1:1000 |
| Which type of device converts light energy into electrical energy? | photovoltaic cell |
| What is often used when it is necessary to block the voltage between one electronic circuit and another, and transfer the signal at the same time? | amplifier coupling capacitor |
| Transistors are semiconductor devices with how many or more terminals? | three |
| How many distinct types of UJTs are presently in use? | 40+ |
| What uses voltage to control an electrostatic field within the transistor? | FET |
| The MOSFET is normally constructed so that it operates in one of what two basic modes? | depletion and enhancement |
| The MOSFET has a higher input impedance than the JFET, how many megohms? | 10 to 100 million |
| Most power supplies are made up of the following four basic sections: transformer, rectifier, filter, and what else? | regulator |
| What steps up or steps down the input line voltage and isolate the power supply from the power line? | transformer |
| What converts the alternating current input signal to a pulsating direct current? | rectifier |
| What maintains the output of the power supply at a constant level in spite of large changes in load current or input line voltages? | regulator |
| What provides two equal voltages to the conventional full-wave rectifier? | center-tapped transformer |
| What is the conversion of an alternating current to a pulsating direct current? | rectification |
| What is current called that flows in pulses in the same direction? | pulsating DC |
| Which terms are AC voltages normally specified in? | RMS values |
| Which type of device has two or more diodes arranged so that load current flows in the same direction during each half cycle of the AC supply? | full-wave rectifier |
| How many basic types of filter circuits are there? | four |
| What is defined as the time it takes a capacitor to charge 63.2% of the applied voltage or to discharge to 36.8% of its total charge? | one time constant |
| What is the most basic type of power supply filter? | capacitor filter |
| Which type of filter is primarily used in power supplies where voltage regulation is important and where the output current is relatively high and subject to varying load conditions? | LC choke-input |
| What percent of a half-wave rectifier is the ripple frequency of a full-wave rectifier? | 200% |
| What is one of the most commonly used filters primarily used in radio receivers, small audio amplifier power supplies, and in any type of power supply where the output current is low and the load current is relatively constant? | LC capacitor-input filter |
| What gives an indication of how much the output voltage changes over a range of load resistance values? | figure of merit |
| Basic voltage regulators are classified as one of what two ways? | series or shunt |
| Which type of diode blocks current until a specified voltage is applied? | Zener diode |
| Which circuitry provides a constant current output? | current regulator |
| What are used primarily to develop high voltages where low current is required? | voltage multipliers |
| The DC output of the voltage multiplier ranges from 1000 to how many volts? | 30,000v |
| In order for a silicon NPN transistor to conduct, the base must be between how many volts more positive that the emitter? | 0.6 to 0.7 |
| What are the two widely used checks in testing electronic equipment? | signal tracing and visual inspection |
| What is a short-circuit protection device that automatically limits the current to a safe value? | current limiter |
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nng7294
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