Examen EASA M4

What gives the colour of an LED?. The active element. The plastic it is encased in. The type of gas used inside it.

A germanium diode is used for. rectification. voltage stabilization. modulation.

Why is a diode put in parallel with an LED?. To protect it from AC. So it will work only above a certain voltage. So it will work only below a certain voltage.

When testing the forward bias of a diode with a multimeter. the positive lead of the ohmmeter is placed on the anode. it does not matter which terminal the positive lead of the ohmeter is placed. the positive lead of the ohmmeter is placed on the cathode.

Which of the following describes the characteristics of a Thyristor?. High voltage handling. High power handling. High current handling.

Light Emitting Diodes (LEDs). emit light of only one wavelength dependent on type. have very wide viewing angles. are easily damaged if forward biased b more than 5V.

In a semiconductor junction diode, electrons are the minority carriers. within the P region. within the N region. in both the N and P regions.

A silicon diode, when compared to a germanium diode has. a higher forward bias voltage. the same forward bias voltage. less forward bias voltage.

A zener diode. allows current to flow in one direction. stabilizes voltage at a predetermined level. acts like a switch.

A junction diode. is similar to a vacuum diode but cannot rectify. has one p-n junction. can handle only very small currents.

Reverse bias. raises the potential barrier. lowers the potential barrier. greatly increases the majority carrier current.

A diode connected across a relay coil is used to. dissipate coil spikes on switch off. allow the coil to energize with only one polarity. cause a delay in switching on.

To check the forward resistance of a diode with a multimeter, the lead connected to the positive terminal is put to the. anode. cathode. either anode or cathode.

A thyristor has which of the following?. A positive temperature coefficient. High resistance when switched off. High resistance when switched on.

In an LED, what is used to make the colour?. The plastic lens cover. The electrons. The doping material.

An atom with 5 electrons in its outer shell is part of. a C type material. a P type material. an N type material.

A thyristor is commonly used for. overvolts regulation. voltage regulation. rectification.

A diode which emits photons when conducting is a. light emitting. varactor. zener.

The electrodes of an SCR are. gate, cathode, anode. source, drain, gate. anode, cathode, source.

What gives an LED its colour?. A gas. The cover. Composition and impurity of the compound.

Forward voltage of a silicon diode is. 1.6v. 0.6v. 0.2v.

What is the typical volts drop across an LED. 0.2v. 0.4v. 1.6v.

What diode gives off light photons when forward biased. LED. Gunn diode. Schottky diode.

The anode of a diode is connected to a +4V DC supply and the cathode is connected to a +2V DC supply. The diode is. forward biased not conducting. reverse biased not conducting. forward biased conducting.

Using electron flow in a diode the current flows from. Anode to Cathode. Cathode to Base. Cathode to Anode.

When a hole diffuses from the p region to the n region. raises the potential barrier. it becomes a minority carrier in the n region. lowers the potential barrier.

A junction diode. can handle only small currents. is similar to a vacuum diode but cannot rectify. has one p-n junction.

A germanium diode. has a lower forward bias voltage than a silicon diode. has a higher forward bias voltage than a silicon diode. has the same forward bias voltage as a silicon diode.

What switches off a thyristor?. Reverse bias gate. Remove the gate voltage. Remove supply voltage.

When an SCR is switched on it has. low resistance. no change in resistance. high resistance.

What type of pulse is required to switch on an SCR?. Positive. Negative. Positive or negative.

A piece of pure Germanium. is electrically stable. has a deficit of electrons. has an excess of electrons.

When a diode is forward biased, current flow is mainly due to the. germanium bias junction. majority carriers. minority carriers.

When a diode is forward biased the. positive lead is connected to both N and P type. positive lead is connected to the N type and negative to the P type. positive lead is connected to the P type and negative to the N type.

What are the majority carriers for a forward biased PN junction device?. Electrons and holes. Holes. Electrons.

Germanium in its pure state is. negatively charged. neutral. positively charged.

Which diode has a lower forward bias voltage?. Silicon. Germanium. Both have the same forward bias voltage.

A Zener diode is used for. voltage stabilisation. rectification. voltage regulation.

A thyristor SCR is a. bi-directional device. unidirectional device. multidirectional device.

What component is used to turn AC to DC?. Thyristor. Diode. Transistor.

What is an intrinsic material?. One with added elements. One with removed elements. A pure material.

A diode is parallel to an LED in an AC circuit to. provide correct amount of current for LED when circuit is switched on. prevent back EMF in the circuit when LED is switched off. protect LED from AC current when switched on.

In a forward biased diode, current is carried by. majority carriers. both. minority carriers.

When checking a diode for reverse bias resistance the positive lead goes to. anode and negative lead to earth. cathode and negative lead to anode. anode and negative lead to cathode.

Zener diodes are used for. Current control. Voltage control. Temperature control.

Once started conducting an SCR switches off. only when the anode goes negative to the cathode. automatically after a specific time. only when the anode goes positive to the cathode.

In a forward biased diode, electrons leave the. the anode. the cathode. the doped area.

Diodes are. conductors. semi-conductors. Insulators.

To function, i.e. conduct, a junction diode made of silicon requires a forward bias of at least. 0.2v. 1.41v. 1v.

What is the average gain of an Op Amp?. 20. 200,000. 200.

Tunnel diodes have the following characteristics: Heavily doped P-N junction with an extremely narrow depletion region. Lightly doped P and N regions and a high reverse breakdown voltage. Lightly doped P region, heavily doped N region and has a fast response time.

The capacitance of a varactor diode is. inversely proportional with reverse bias voltage. a linear function of applied reverse bias voltage. directly related to the forward bias voltage.

A semiconductor doped with an element having a valency of 5 will produce. an N type material. either an N type or a P type depending on what type of semiconductor material is used. a P type material.

In a diode clamper, if the resistor is removed making the time constant equal to C x r where r is the reverse resistance of the diode, this will ensure a. long time constant. short time constant. Very Long Time Constant.

PIN diodes are used mainly for. linear rectifiers. fast switching devices. voltage operated rectifiers.

To enable an IMPATT diode to operate correctly, it must be. connected to a resonant circuit. used in its reverse bias mode. operated in its negative resistance range.

What type of diode would be used to stop voltage spikes across a coil of a relay?. Schottky diode. Zener diode. Gunn diode.

What is a schottky diode used for?. Rectification. Stabilization. Very high frequency applications.

When a hole diffuses from a p-region to the n-region it. becomes a minority carrier in the n-region. lowers the potential barrier. raises the potential barrier.

The junction barrier offers opposition to only. holes in the p-region. free electrons in the n-region. majority carriers in both regions.

Avalanche breakdown occurs when. reverse bias exceeds a certain value. forward bias exceeds a certain value. forward current becomes excessive.

If forward bias is increased from zero on a p-n junction, a rapid increase in current flow for a relatively small increase in voltage occurs. when the flow of minority carriers is sufficient to cause an avalanche breakdown. when the depletion layer becomes larger than the space charge area. only after the forward bias exceeds the potential barrier.

A band pass filter excludes frequencies. below the frequency required only. above and below the frequency required. above the frequency required only.

In an unbiased p-n junction, current flow is. below the frequency required only. above and below the frequency required. above the frequency required only.

What diode is used to stop power spikes in a coil?. Gunn diode. Schottky diode. Two directional zener diode.

What type of diode when forward biased holes and electrons recombine producing photons?. LED. Photodiode. Gunn.

A zener diode is designed to operate. below its breakdown voltage. either above or below its breakdown voltage. above its breakdown voltage.

A triac is a type of. thermistor. transistor. thyristor.

If a junction diode is reverse biased too far, the output current would. reverse direction. cease to flow. increase.

When a PN junction is forward biased, it conducts via. intrinsic carrier. majority carrier. minority carrier.

If the reverse bias voltage across a diode is too high. load current reduces to zero. load current increases rapidly. load current reverses.

An LED which emits green light uses. gallium phosphide. gallium arsenide. gallium arsenide phosphide.

An LED which emits red light uses. gallium phosphide. gallium arsenide phosphide. gallium arsenide.

A photodiode is operated under. reverse bias conditions. forward bias conditions. reverse or forward bias conditions.

To increase capacitance of a varactor diode. reverse bias voltage is increased. reverse bias voltage is decreased. forward bias voltage is decreased.

A bi-directional TRIAC has two SCRs connected in. series parallel. inverse parallel. parallel series.

A thyristor can be forward biased by a. positive or negative pulse. negative pulse. positive pulse.

In an electronic circuit, if the anode of a diode is clamped to ground. What is this called?. A negative clamping circuit. A negative limiting circuit. A positive clamping circuit.

To decrease the capacitance of a varactor. reverse bias should be decreased. forward bias should be increased. reverse bias should be increased.

A Zener diode is used across the output for a power supply circuit to. give a full wave rectification. prevent thermal runway. provide a steady DC voltage output without fallin.

If a diode has gone open circuit in a full wave bridge rectifier, the output frequency ripple is. the same as the input frequency. twice the input frequency. half the input frequency.

In a full wave bridge rectifier. the output is pure DC. Frequency is 0 Hz. the output frequency is twice the input frequency. the output voltage is twice the input voltage.

After passing through a rectifier, alternating current becomes. smooth direct current. pulsating direct current. square wave form current.

A Zener diode usually works. only in reverse bias. at variable voltages. only in forward bias.

P type materials require. acceptors. conductors. donors.

Which of the following explains how the photodiode works?. Photodiodes are forward biased to conduct when light falls upon them. Photodiodes are back biased not to conduct when light falls upon them. Photodiodes are back biased to conduct when light falls upon them.

In an NPN transistor the P is the. collector. emitter. base.

When compared to a photo diode, a photo transistor. is less sensitive to light levels. responds faster to changes of light. is slower to respond to changes of light.

For correct operation of a transistor, the following conditions must apply. The base-emitter junction must be forward biased and the base-collector junction must be greater than 0.7 volts. For an NPN transistor the base-emitter junction must be forward biased and for a PNP transistor the base emitter junction must be reverse biased. The base-collector junction must be reverse biased and the base-emitter junction must be forward biased.

When a positive voltage is applied to the base of a normally biased n-p-n common emitter amplifier. the collector voltage goes less positive. the emitter current decreases. the base current decreases. the base current decreases.

Which way does conventional current flow in a PNP junction?. Emitter to base. Collector to base. Collector to emitter.

For conduction of a transistor, the emitter junction is. forward or reverse as appropriate to the input signal. reverse biased. forward biased. forward biased.

In a PNP transistor, which way does conventional current flow?. Base to emitter. Collector to emitter. Emitter to collector.

In a PNP transistor, conventional current will flow when. the emitter is more positive than the base. the base is more positive than the emitter. the collector is more positive than the emitter.

In a common collector circuit the output and input are. in phase. out of phase by 60°. out of phase by 90°.

For an NPN transistor to conduct the collector circuit has to be. more positive than the base. less positive than the emitter. more positive than the emitter.

The resistance measured using an AVO between the Collector and Emitter of a transistor is. smaller Collector to Emitter. same both ways. higher Collector to Emitter.

A transistor is used in. current amplifiers. both current amplifiers and voltage amplifiers. voltage amplifiers.

In which direction does the current flow on a PNP transistor when forward biased?. Emitter to base. Emitter to collector. Collector to emitter.

With an NPN transistor electrons leave the. Base. Collector. Emitter.

In a transistor, the arrow always points in the direction of. electron flow. conventional current. emitter.

In an NPN transistor the. collector is more positive than the base. collector is the same as the base. emitter is more positive than the base.

If light entering a photo transistor decreases, the current to the collector. decreases. remains the same. increases.

A silicon bi-polar transistor with two depletion zones. operates by varying electric fields. is a voltage operated device. consists of 3 slices of semiconductor material.

To decrease the voltage gain of a common emitter amplifier you would increase the resistance in the. base circuit. emitter circuit. collector circuit.

The current I/P and O/P waveforms in a common emitter amplifier are. out of phase. in phase. 90° out of phase.

Which mode of operation provides the best high frequency response? Common. emitter. base. collector.

A FET when compared to a junction transistor is. low impedance. current operated. high impedance.

One characteristic of the emitter follower is. low resistance output. low current amplification. high voltage amplification.

An amplifier current gain will be slightly less than 1, but its voltage gain will be high, if it is connected in the. common base configuration. common emitter configuration. common collector configuration.

The common collector amplifier is sometimes called the emitter follower circuit because. the emitter voltage follows the collector voltage. the emitter current follows the collector current. the emitter voltage follows the base voltage.

Amplifiers may be classified as. voltage amplifiers or power amplifiers. voltage amplifiers or impedance amplifiers. common emitter or common collector amplifiers.

An amplifier can provide both voltage gain and current gain when it is connected in th. common collector configuration. common emitter configuration. common base configuration.

How do you increase voltage gain of an amplifier?. decrease base circuit bias. decrease input resistance. decrease output resistance.

The input and output signals of a common emitter amplifier are. in phase. equal. out of phase.

A transistor is said to be in the quiescent state when. no currents are flowing. it is unbiased. no signal is applied to the input.

A common base transistor circuit is so called because. the base is common to the emitter and collector circuits. the base region is located between the emitter and collector region. the base is n-type material.

In a FET, the junction connections are called. drain, source and gate. drain, collector and junctions. base, collector and emitter.

How is a push-pull transistor arrangement connected?. Collector to collector. Emitter to emitter. Base to base.