Summary
Summary Unit 19 Assignment A distinction
- Institution
- PEARSON (PEARSON)
Summary of 23 pages for the course Unit 19 - Electronic Devices and Circuits at PEARSON (Distinction)
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Unit 19 Assignment AApprentice Name: Nicole Senyurt
Company Name: Mac Ltd.
Introduction:
As a young individual, I have been hired by a local company called Mac Ltd. Mac Ltd. specialises in fixing
and modifying domestic electronic equipment. As part of my role at the company, I have been
requested to use a range of different test equipment and software in order to investigate the most often
used analogue electronic devices and the variety of circuits in which they have been used in. I also have
to keep clear and precise records of every action I take on board in order to refer back to them in the
latter as I will build up my skills and knowledge of electronic devices and circuits which is essential to my
role.
Diodes:
What is a diode?
A diode is an electronic device that allows the current to flow only in one direction, whilst restricting the
current from the other direction. The diode becomes reverse biased when it acts as an insulator and
then is forward biased when it allows the current to go along. A diode consists of two terminals-anode
and cathode. Diodes are typically used in switches,rectifiers,voltage regulators and oscillators.
Types of diodes and uses:
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 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.
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 a brake light and even used as backlighting of TV screens.
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 in 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( Zener 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.
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
dependent on voltage.
Half-wave rectifiers:
How do half-wave rectifier circuits work?
A half wave rectifier circuit is a type of rectifier circuit which involves transforming the positive
current of the input signal into a pulsating DC current which results in being the DC output signal. This
simple rectifier circuit consists of using one diode to act as the half wave rectifier, an AC power supply
source, a step-down transformer in order to reduce the voltage to safe levels and a resistor load in
order to improve output stability. Within this circuit, the step down transformer is used instead of a
step up transformer because the step-down transformer reduces the high AC voltage to a low voltage
level for safety purposes whilst the step up transformer does the opposite. It is crucial to have the
step-down transformer within the circuit as in the case where the AC voltage is too high and can cause
permanent damage to the diode since we only require a small amount of voltage to power the diode.
Also, within this circuit we have a standard diode which is a two terminal device which allows the flow
of electrical current to move only in one direction whilst blocking the current entering from the other
direction unlike a Zener diode which allows the current to flow in reverse bias mode. Whilst we have a
resistor load within our half wave rectifier circuit in order to restrict the current to flow up.
, Schematic diagram of diode as a Half-wave rectifier circuit:
Full-wave rectifiers:
How do full wave rectifier circuits work?
A full wave rectifier circuit is a type of rectifier circuit which involves changing the AC voltage into a
pulsating DC voltage using both the half cycles of the applied AC voltage. This circuit consists of an AC
power supply, four diodes of which two of them conducts during the first half cycle whilst the other
remaining two conducts the other half cycle of the applied AC voltage. We also have a load resistor
that is small compared to the reverse-biased diode’s capacitance reactance so that they block out the
negative excursions of the input waveform within the circuit. We also have a capacitor that acts as a
filter in order to lower the ripple voltage. Make sure that when connecting the capacitor across the DC
output terminals of the full wave rectifier in order for the polarities to match. Within full-wave rectifier
circuits, the power supply used should be complete and stabilized through the means of rectifier diodes
which change the power from AC to DC. Also, by having a rectified voltage which is then filtered in order
to reduce the voltage ripple on the rectified waveform. Then we can use the means of having a Zener
diode as a voltage regulator which then leads us to its ideal final value.
Developing the circuit into a full-wave rectifier with capacitor smoothing and Zener diode voltage
regulation:
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