Electronic Diode Questions with Answers
In electronics, what is a diode?
A: A diode is a two-terminal electronic component that allows current to flow in
only one direction.
A diode has low (ideally zero)
resistance to current in one
direction, and what in the other?
A: High (ideally infinite) resistance.
Today, what is the most common type of diode?
A: A semiconductor diode.
A semiconductor diode, is a crystalline piece of
semiconductor material with what type of junction, connected to two electrical
terminals?
A: A p–n junction.
What are the main components of a vacuum tube diode?
A: Two electrodes, a plate (anode) and a heated cathode.
Diodes were the first what?
A: Semiconductor electronic devices.
The discovery of crystals' rectifying abilities was made by
whom?
A: German physicist Ferdinand Braun in 1874.
What were the first semiconductor diodes called?
A: Cat's whisker diodes.
What material were they made of?
A: Mineral crystals such as galena.
Today, most diodes are made of what?
A: Silicon.
Sometimes other semiconductors materials are used, such as
selenium or what?
A: Germanium.
What is the most common function of a diode?
A: To allow an electric current to pass in one direction while blocking current
in the opposite.
A diode can therefore be thought about as an electronic
version of a what?
A: Check valve.
This unidirectional behavior is called what?
A: Rectification.
What is it used for?
A: To convert alternating current to direct current.
This also includes extraction of modulation from what?
A: Radio signals in radio receivers.
Diodes have more complicated behavior than this simple
on–off action, due to their what?
A: Nonlinear current-voltage characteristics.
Semiconductor diodes begin conducting electricity only if
what?
A: A certain threshold voltage is present in the diode's forward direction.
When a diode is in a state where that threshold voltage
requirement is met, it is said to be what?
A: Forward-biased.
The voltage drop across a forward-biased diode varies only
a little with the what?
A: Current, and is a function of temperature.
This means a diode in effect can be used as a what?
A: Temperature sensor or voltage reference.
How can a semiconductor diodes' current–voltage
characteristic be tailored?
A: By varying the semiconductor materials and doping (introducing impurities
into the materials).
These techniques are used to create many types of what?
A: Special-purpose diodes that perform a variety of functions.
Zener diodes are used to do what?
A: Regulate voltage.
What function do avalanche diodes perform?
A: Protect circuits from high voltage surges.
What are varactor diodes used for?
A: To electronically tune radio and TV receivers.
Tunnel diodes are used to generate what?
A: Radio-frequency oscillations.
Diodes that produce light are called what?
A: Light-emitting diodes (LEDs).
Tunnel, Gunn and IMPATT diodes exhibit what electrical
characteristic?
A: Negative resistance, which is useful in
microwave and switching circuits.
When were vacuum tube diodes and semiconductor diodes
developed separately?
A: At approximately the same time, in the early 1900s.
In 1873, Frederick Guthrie discovered the basic principle
of operation of what?
A: Thermionic diodes.
He discovered that a positively charged electroscope could
be discharged by doing what?
A: Bringing a grounded piece of white-hot metal close to it (but not actually
touching it).
The same did not apply to a "what", indicating that the
current flow was only possible in one direction?
A: Negatively charged electroscope.
Thomas Edison independently rediscovered the principle on
what date?
A: February 13, 1880.
