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In a reverse biased PN-junction, which current carriers cause leakage current?
The minority carriers.
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The action of a PN-junction during breakdown can be explained by what two theories?
Zener effect and avalanche effect.
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Which breakdown theory explains the action that takes place in a heavily doped PN-junction with a reverse bias of less than 5 volts?
Zener effect.
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What is the doping level of an avalanche effect diode when compared to the doping level of a Zener-effect diode?
The doping level of an avalanche effect diode is lower.
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During avalanche effect breakdown, what limits current flow through the diode?
An external current-limiting resistor.
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Why is electron flow with the arrow in the symbol of a Zener diode instead of against the arrow as it is in a normal diode?
Because Zener diodes are operated in the reverse bias mode.
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What is the main difference in construction between normal PN junction diodes and tunnel diodes?
The amount of doping.
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What resistance property is found in tunnel diodes but not in normal diodes?
Negative resistance.
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When compared to the ordinary diode, the tunnel diode has what type of depletion region?
The tunnel diode has a very narrow depletion region.
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In the tunnel diode, the tunneling current is at what level when the forbidden gap of the N-type material is at the same energy level as the empty states of the P-type material?
Minimum.
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The varactor displays what useful electrical property?
Variable capacitance.
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When a PN junction is forward biased, what happens to the depletion region?
The depletion region decreases.
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When the reverse bias on a varactor is increased, what happens to the effective capacitance?
Capacitance decreases.
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The SCR is primarily used for what function?
The SCR is primarily used for switching power on or off.
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When an SCR is forward biased, what is needed to cause it to conduct?
A gate signal.
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What is the only way to cause an SCR to stop conducting?
The forward bias must be reduced below the minimum conduction level.
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The TRIAC is similar in operation to what device?
SCR.
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When used for ac current control, during which alternation of the ac cycle does the TRIAC control current flow?
During both alternations.
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What type of bias is required to cause an LED to produce light?
Forward bias.
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When compared to incandescent lamps, what is the power requirement of an LED?
Very low.
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In a common anode, seven-segment LED display, an individual LED will light if a negative voltage is applied to what element?
The cathode.
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What is the resistance level of a photodiode in total darkness?
Very high.
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What type of bias is required for proper operation of a photodiode?
Reverse bias.
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What is a typical light-to-dark resistance ratio for a photocell?
1:1000.
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What semiconductor device produces electrical energy when exposed to light?
Photovoltaic cell.
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The UJT has how many PN junctions?
One.
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The area between base 1 and base 2 in a UJT acts as what type of common circuit component?
Variable resistor.
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The sequential rise in voltage between the two bases of the UJT is called what?
A voltage gradient.
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What is the normal current path for a UJT?
From base 1 to the emitter.
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What is one of the primary advantages of the FET when compared to the bipolar transistor?
High input impedance.
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The FET and the vacuum tube have what in common?
Voltage controls conduction.
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The base of a transistor serves a purpose similar to what element of the FET?
Gate.
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What are the two types of JFET?
N-channel and P-channel.
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The source and drain of an N-channel JFET are made of what type of material?
N-type material.
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What is the key to FET operation?
Effective cross-sectional area of the channel.
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What is the normal current path in an N-channel JFET?
From source to drain.
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Applying a reverse bias to the gate of an FET has what effect?
Source-to-drain resistance increases.
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The input and output signals of a JFET amplifier have what phase relationship?
They are 180 degrees out of phase.
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When compared to the JFET, what is the input impedance of the MOSFET?
The MOSFET has a higher input impedance.
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What are the four elements of the MOSFET?
Gate, source, drain, and substrate.
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The substrate of an N-channel MOSFET is made of what material?
P-type material.
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In a MOSFET, which element is insulated from the channel material?
The gate terminal.
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What type of MOSFET can be independently controlled by two separate signals?
The dual-gate MOSFET.
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What is the purpose of the spring or wire around the leads of a new MOSFET?
To prevent damage from static electricity.
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