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Subelement E6
CIRCUIT COMPONENTS
Section E6B
Diodes
What is the most useful characteristic of a Zener diode?
  • A constant current drop under conditions of varying voltage
  • A constant voltage drop under conditions of varying current
  • A negative resistance region
  • An internal capacitance that varies with the applied voltage

A Zener Diode is a diode that acts like a regular diode under normal conditions, however allows current to flow the opposite direction if the voltage is sufficient enough.

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What is an important characteristic of a Schottky diode as compared to an ordinary silicon diode when used as a power supply rectifier?
  • Much higher reverse voltage breakdown
  • Controlled reverse avalanche voltage
  • Enhanced carrier retention time
  • Less forward voltage drop

The Schottky diode also known as hot carrier diode, is a semiconductor diode with a low forward voltage drop and a very fast switching action. The cat's-whisker detectors used in the early days of wireless and metal rectifiers used in early power applications can be considered primitive Schottky diodes.

When forward current flows through a solid-state diode, there is a small voltage drop across its terminals. A silicon diode has a typical voltage drop of 0.6–0.7 V, while a Schottky diode has a voltage drop of 0.15–0.45 V. This lower voltage drop can be used to give higher switching speeds and better system efficiency.

The Schottky diode is often used as a voltage limiter (aka clamp or bypass diode), in reverse bias.

-devdev

/wiki/Schottky_diode

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What special type of diode is capable of both amplification and oscillation?
  • Point contact
  • Zener
  • Tunnel
  • Junction

Tunnel Diodes are used in frequency converters and detectors. They have negative differential resistance in part of their operating range, and therefore are also used as oscillators, amplifiers, and in switching circuits using hysteresis.

http://en.wikipedia.org/wiki/Tunnel_diode

Hint think of shouting down a long underground tunnel, your voice will be amplified and echo(oscillate) W9ECO

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What type of semiconductor device is designed for use as a voltage-controlled capacitor?
  • Varactor diode
  • Tunnel diode
  • Silicon-controlled rectifier
  • Zener diode

In electronics, the following:

  • a varicap diode
  • varactor diode
  • variable capacitance diode
  • variable reactance diode
  • tuning diode

are types of diode whose capacitance varies as a function of the voltage applied across its terminals.

http://en.wikipedia.org/wiki/Varicap

Hint: "V" in voltage, "V" in varactor diode.

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What characteristic of a PIN diode makes it useful as an RF switch or attenuator?
  • Extremely high reverse breakdown voltage
  • Ability to dissipate large amounts of power
  • Reverse bias controls its forward voltage drop
  • A large region of intrinsic material

The I in PIN means intrinsic!

Wikipedia: A PIN diode is a diode with a wide, undoped intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts.

The wide intrinsic region is in contrast to an ordinary PN diode. The wide intrinsic region makes the PIN diode an inferior rectifier (one typical function of a diode), but it makes the PIN diode suitable for attenuators, fast switches, photodetectors, and high voltage power electronics applications.

-ke7kto

Test Hint: The "I" in PIN would indicate the "I" in Intrinsic.

-KE0IPR

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Which of the following is a common use of a hot-carrier diode?
  • As balanced mixers in FM generation
  • As a variable capacitance in an automatic frequency control circuit
  • As a constant voltage reference in a power supply
  • As a VHF/UHF mixer or detector

A hot carrier diode is also known as a Schottky Diode. It's a fast switching diode (due to low capacitance) with a low forward voltage drop. Their fast switching makes them effective as a mixer or detector at VHF/UHF frequencies.

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What is the failure mechanism when a junction diode fails due to excessive current?
  • Excessive inverse voltage
  • Excessive junction temperature
  • Insufficient forward voltage
  • Charge carrier depletion

Some of the power that flows through a junction diode is dissipated in the form of heat. If a diode becomes too hot it will be damaged or destroyed.

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Which of the following describes a type of semiconductor diode?
  • Metal-semiconductor junction
  • Electrolytic rectifier
  • CMOS-field effect
  • Thermionic emission diode

Hint: "Semiconductor" is in the answer.

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What is a common use for point contact diodes?
  • As a constant current source
  • As a constant voltage source
  • As an RF detector
  • As a high voltage rectifier

Here's the wikipedia page on Point-contact diodes

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In Figure E6-3, what is the schematic symbol for a light-emitting diode?
  • 1
  • 5
  • 6
  • 7

The arrows coming off the diode represent the emission of photons. So symbol 5 is a diode that emits photons-- also known as a light emitting diode.

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What is used to control the attenuation of RF signals by a PIN diode?
  • Forward DC bias current
  • A sub-harmonic pump signal
  • Reverse voltage larger than the RF signal
  • Capacitance of an RF coupling capacitor

A PIN diode is a semiconductor device that operates as a variable resistor at RF and microwave frequencies. One common use for PIN diodes is as an RF switch. (E6B12)The characteristic of a PIN diode that makes it useful as an RF switch or attenuator is a large region of intrinsic material. (E6B05) The forward DC bias current is used to control the attenuation of RF signals by a PIN diode. (E6B11)

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What is one common use for PIN diodes?
  • As a constant current source
  • As a constant voltage source
  • As an RF switch
  • As a high voltage rectifier

Under zero or reverse bias, a PIN diode has a low capacitance. The low capacitance will not pass much of an RF signal. Under a forward bias of 1 mA, a typical PIN diode will have an RF resistance of about 1 ohm, making it a good RF conductor. Consequently, the PIN diode makes a good RF switch.

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What type of bias is required for an LED to emit light?
  • Reverse bias
  • Forward bias
  • Zero bias
  • Inductive bias

Before a light emitting diode can “emit” any form of light it needs a current to flow through it, as it is a current dependent device with their light output intensity being directly proportional to the forward current flowing through the LED.

See ElectronicsTutorials

In electronics, bias is a steady voltage, magnetic field, or other factor applied to an electronic system or device to cause it to operate over a predetermined range.*

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