DIODES Flashcards
What is a Diode?
A two terminal electronic component that conducts primarily in one direction.
/What is the main function of a diode?
To allow current to flow through in only one direction (forward bias) and to block current in the opposite direction (reverse bias).
What is the mechanical analogous of a diode?
It is similar to a mechanical check valve, this will only let liquid through in one direction while blocking the flow of fluid in the other.
What is a thermionic Diode?
It is an evacuated vacuum tube that contains a filament (the cathode) and a metal plate (the anode).
How does a thermionic Diode work?
Current passes through the cathode, heating it up. Electrons will flow from the cathode to the anode. This allows current to flow in one direction but not the other.
What is the emission of electrons called?
The edison effect of thermionic emission.
What is a LED?
A two lead semiconductor containing a P-N junction that emits light upon activation. When a suitable voltage is applied, then electrons are able to recombine with electron holes. This will release energy in the form of photons.
What is the P-N junction?
It is the boundary between the P type and N type semiconductor material. The P side contains excess of holes, and the N side will contain an excess of electrons.. This will allow electrical current to pass through only in one direction.
What is a photodiode?
A semiconductor device that absorbs photons and converts it into electrical energy, we use them in solar pannels.
What is the Zener Diode?
It is a normal diode, except it is able to allow current to flow in the reverse direction when its Zener Voltage is reached.
What is useful about the Zener Diode?
It can be made to breakdown at a specified voltage and can be used to provide a regulated voltage output.
What is one function of the Diode?
It can convert AC to DC, and can also be used to detect AM signals.
What is the second function of the Diode?
The voltage drop across a forward biased diode is temperature based, therefore we can use it as a temperature sensor or as a voltage reference.
What are the characteristics of an Ideal diode?
In the forward direction, the diode is a conductor and has zero resistance. This means that in a current voltage graph, the increase in voltage will be vertical.
In the reverse direction, the diode will behave like an open circuit and so no current will flow.
What are the characteristics of a real Diode?
It will conduct slightly until its threshold voltage has been reached, for silicon this is around 0.7V. At this point, the voltage will increase but the slope is not infinite as there is some resistance.
In the reverse direction, a non zero leakage current will be conducted until a large reverse voltage below the breakdown voltage is reached and then the current will increase very rapidly.
