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Summary Unit 19 Assignment 1
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Explore the safe operation and applications of analogue devices and circuits that form the building blocks of commercial circuits
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Assignment: Analogue electronicA) Diodedevices andincircuits
and Diodes
circuits
A diode uses a semiconductor that only allows current to flow in one direction. The most
common semiconductor material used is silicon as it has 4 valence electrons and acts as
both conductor and insulator. The silicon is split into two the n-type which is doped with
a Group V like Phosphorus and p-type which is doped with Group 3 metal Aluminium.
The forward bias acts as a conductor and the reverse bias acts as an insulator. An
example of a type of diode are:
Light-emitting diode: LED is a common type of diode as well as PN junction diodes but
produces light. When you forward bias an LED, this allows the current to flow and light is
then generated which forms a variety of different colours. Due to this major part to LED,
it is being vastly used in lighting and display applications such as being used in electronic
devices as indicator lamps, in automobiles like cars and trucks as brake lights.
Photodiode: A photodiode is a type of PN junction device that formulates currents when
exposed to light. This type of diode functions in reverse biased mode and changes light
energy to electrical energy. It is used mainly in counters and switching circuits, optical
communications and majorly within burglar alarm systems as until exposure to radiation
is not cut on, the current still maintains its flow until the point where the light energy
begins to fail to fall on the electronic device then this initiates the burglar alarm.
Zener Diode: Zener Diodes unlike other types of diodes allows the current to flow in
reverse bias mode when the Zener voltage has been reached. This diode is used in
reverse bias in order to provide a stable reference voltage as the Zener diode has a
constant voltage output across its terminals and when the breakdown voltage has been
reached, this can then act as a stable output voltage for a load that is connected to it in
parallel mode
Laser Diode: Laser Diode is a type of diode that also produces light similarly to LED,
however the light that’s produced by laser diodes are coherent. Laser Diodes are
typically used in DVD and CD players and as well as laser pointers.
PN-junction diode: This type of diode is the most common diode, and it is a two
terminal semiconductor device which allows the current to flow through one direction
Diode in a
only whilst restricting the current to flow in reverse. This diode is typically used as a solar
cell, rectifiers in electrical circuits and as a voltage-controlled oscillator in varactors
Half-wave
Varactor(Varicap) diode: Varicap Diodes are a type of semiconductor diodes that have
been designed to expose the voltage-dependent capacitance of a reverse-biased p-n
junction diode. These are typically used in RF tuning to circuits in order to provide
capacitance level that is controlled and dependant on voltage
, Xx`
After the current flows through the diode, it only flows in one direction
therefore it is a direct current. This is shown on the oscilloscope, the load
which is the resistor is experiencing a pulsating waveform which shows the
current is now a direct current. The voltage across the resistor is shown as
12.236 V If the load was a bulb, it will flicker as it is only using half the wave
form.
Diodes in Full-wave
bridge rectifier
The full-wave bridge rectifier converts ac input into a more consistent dc output. This
circuit comprises of an AC power supply and four diodes, two of which conduct during the
first half cycle of the supplied AC voltage and the other two conducting during the second
half cycle. We also have a load resistor that is modest in comparison to the capacitance
reactance of the reverse-biased diode, which blocks the negative excursions of the input
waveform within the circuit. In order to reduce the ripple voltage, we additionally have a
capacitor that functions as a filter. Make that the polarities of the capacitor and the DC
output terminals of the full-wave rectifier match before connecting them. The power
supply utilised in full wave rectifier circuits should be competitive and stable, with rectifier
diodes changing the power from AC to DC. Having a rectified voltage that is subsequently
filtered to lessen the voltage ripple on the rectified waveform is also beneficial. Then we
may utilise a Zener diode as a voltage regulator, which will bring us to the perfect end
value.
, The resistor value can be calculated by voltage supply – votage zener/max
current. The Imax is 0.5 which is the power/3.6 = 138.89mA. 230 –
3.6/138.89*10^-3 = 1.6kΩ
At stage A the voltage is 23.02 so it is safe to use, the oscilloscope shows the
green current is ac as it hasn’t passed through the diode. At stage B the
current passes through the positive cycle where it goes through the diode
and is converted to dc current this can be shown on the oscilloscope where it
is above the axis.
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