Example Presentation Powerpoint 2007

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In an electrical, computer or storage system, active components are those that require electrical power to operate. This could include the power supply, storage device, transistors, diodes and other integrated circuits but would exclude system components such as the resistor, capacitors or inductors that do not require electrical power to operate (called passive components).

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The job of Resistors are to limit current flow through an electrical circuit. Resistance is measured in Ohm's and is given the symbol . Resistor colour codes are used to identify the resistance and tolerance rating of small resistors. Tolerance is the percentage measure of the accuracy of a resistor and the E6 (20%), E12 (10%), E24 (5%) and E96 (1%) Series of tolerance values are available.Resistor Symbol

WIREWOUND RESISTORS CARBON COMPOSITION FILM RESISTORS SMD (Surface mount device)

Presets Rheostat potentiometers

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Variable resistors consist of a resistance track with connections at both ends and a wiper which moves along the track as you turn the spindle.

PRESETSThey are designed to be mounted directly onto the circuit board and adjusted only when the circuit is built. For example to set the frequency of an alarm tone or the sensitivity of a lightsensitive circuit. A small screwdriver or similar tool is required to adjust presets. Presets are much cheaper than standard variable resistors so they are sometimes used in projects where a standard variable resistor would normally be used.

Preset Symbol

RHEOSTATRheostats are often used to vary current, for example to control the brightness of a lamp or the rate at which a capacitor charges.

Rheostat Symbol

POTENTIOMETERSThis arrangement is normally used to vary voltage, for example to set the switching point of a circuit with a sensor, or control the volume (loudness) in an amplifier circuit. If the terminals at the ends of the track are connected across the power supply then the wiper terminal will provide a voltage which can be varied from zero up to the maximum of the supply.

Potentiometer Symbol

WIREWOUNDWirewound Resistor, is made by winding a thin metal alloy wire (Nichrome) or similar wire onto an insulating ceramic former in the form of a spiral helix handle much higher electrical currents than other resistors of the same ohmic value with power ratings in excess of 300 Watts

CARBONCarbon Composite Resistors are low to medium power resistors with low inductance which makes them ideal for high frequency applications but they can also suffer from noise and stability when hot.

FILM RESISTORMetal Film Resistors have much better temperature stability than their carbon equivalents, lower noise and are generally better for high frequency or radio frequency applications.

SMDSMD resistors are rectangular in shape. They have metallised areas at either end of the body of the SMD resistor and this enables them to make contact with the printed circuit board through the solder.

The Capacitor or sometimes referred to as a Condenser is a passive device, and one which stores energy in the form of an electrostatic field which produces a potential (Static Voltage) across its plates.

1. Dielectric 2. Film Capacitors 3. Ceramic Capacitors 4. Electrolytic Capacitors

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DIELECTRICDielectric Capacitors are usually of the variable type such as used for tuning transmitters, receivers and transistor radios.

Symbol

FILM CAPACITORThis allows for higher capacitance values and smaller case sizes for a given capacitance. Film and foil capacitors are generally used for higher power and more precise applications.

CERAMICCeramic Capacitors or Disc Capacitors as they are generally called. Ceramic capacitors have a high dielectric constant (High-K) and are available so that relatively high capacitances can be obtained in a small physical size.

ELECTROLYTICElectrolytic Capacitors are generally used when very large capacitance values are required.

Electrolytic Capacitors are generally used in DC power supply circuits to help reduce the ripple voltage or for coupling and decoupling applications. Electrolytic's generally come in two basic forms; Aluminium Electrolytic and Tantalum Electrolytic capacitors.

ALUMINIUM ELECTROLYTICThe thickness of the aluminiumoxide film and high breakdown voltage give these capacitors very high capacitance values for their size. Also their tolerance range is quite large up to 20%. Etched foil electrolytic's are best used in coupling, DC blocking and by-pass circuits while plain foil types are better suited as smoothing capacitors in power supplies.

TANTALUM ELECTROLYTICThe dielectric properties of tantalum oxide is also much better than those of aluminium oxide giving a lower leakage currents and better capacitance stability which makes them suitable for timing applications. Also tantalum capacitors although polarized, can tolerate being connected to a reverse voltage much more easily than the Aluminium types but are rated at much lower working voltages.

Inductance is the property in an electrical circuit where a change in the electric current through that circuit induces an electromotive force (EMF) that opposes the change in current

Summary of capacitor types

Table of capacitor uses and applications

This magnetic flux, due to Lenz's law, tends to act to oppose changes in the flux by generating a voltage (a back EMF) in the circuit that counters or tends to reduce the rate of change in the current.

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In electronics, a diode is a twoterminal electronic component that conducts electric current in only one direction. Diodes were the first semiconductor electronic devices. The discovery of crystals' rectifying abilities was made by German physicist Ferdinand Braun in 1897.

Although the crystal semiconductor diode was popular before the thermionic diode, thermionic and solid state diodes were developed in parallel. The principle was independently rediscovered by Thomas Edison on February 13, 1880. Thermionic diodes are thermionic-valve devices (also known as vacuum tubes, tubes, or valves)

Zener diodes Light-emitting diodes (LEDs) Photodiodes Laser diodes

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ENER DIODEDiodes that can be made to conduct backwards.This effect, called Zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. In practical voltage reference circuits Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient to near zero. Some devices labeled as high-voltage Zener diodes are actually avalanche diodes (see above). Two (equivalent) Zeners in series and in reverse order, in the same package.

LEDDepending on the material, wavelengths (or colors) from the infrared to the near ultraviolet may be produced. The first LEDs were red and yellow, and higher-frequency diodes have been developed over time.All LEDs produce incoherent, narrow-spectrum light; white LEDs are actually combinations of three LEDs of a different color, or a blue LED with a yellow scintillator coating. LEDs can also be used as low-efficiency photodiodes in signal applications.

PHOTODIODEPhotodiodes are intended to sense light(photodetector), so they are packaged in materials that allow light to pass, and are usually PIN (the kind of diode most sensitive to light). A photodiode can be used in solar cells, in photometry, or in optical communications.

LASER DIODEWhen an LED-like structure is contained in a resonant cavity formed by polishing the parallel end faces, a laser can be formed. Laser diodes are commonly used in optical storage devices and for high speed optical communication.

A transistor is a semiconductor device used to amplify or switch electronic signals.

A replica of the first working transistor.

BJT (Bipolar junction transistor) JFET (Field-effect transistor),MOSFET

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BJT"The [BJT] is useful in amplifiers because the currents at the emitter and collector are controllable by the relatively small base current."

JFETIn FETs, the drain-to-source current flows via a conducting channel that connects the source region to the drain region. The conductivity is varied by the electric field that is produced when a voltage is applied between the gate and source terminals; hence the current flowing between the drain and source is controlled by the voltage applied between the gate and source. The field-effect transistor (FET), sometimes called a unipolar transistor

Integrated circuits can be classified into analog, digital and mixed signal (both analog and digital on the same chip). Digital integrated circuits can contain anything from one to millions of logic gates, flip-flops, multiplexers, and other circuits in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. These digital ICs, typically microprocessors, DSPs, and micro controllers work using binary mathematics to process "one" and "zero" signals.

MICROPROCESSORS (P)

MICRO CONTROLLERS (PIC)

First Integrated Circuit (IC)

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WHAT IS MICCROPROCESSOR?

Microprocessor (P) is a:Multipurpose, programmable, clockdriven, register-based, electronic device. Reads binary instructions from a storage device called memory. Accepts binary data as input and processes data according to those instructions and provides results as output Basic functions Data transfer, arithmetic and logic, decision making

MICROPROSSER1971 Nov Intel 4004 microprocessor 4-bit