Basic Electronics

Topics: Diode, Capacitor, Resistor Pages: 14 (3192 words) Published: February 9, 2013
An electronic circuit is composed of various types of components. Some of these components are termed as active components because they take part in the transformation of the energy while other components, which only dissipate or store energy, are called as passive elements. The vacuum tubes, rectifier, transistors are some of-the common active while the resistances, which dissipate the power and energy storing elements such as capacitances and inductances are known as passive elements. The transformers may be regarded as a matching device. The success of any electronic circuit depends not only on proper selection of the active elements but on the passive and matching elements too. The proper function, of an active device is decided by the proper values of these passive elements. Hence the selection of these elements such as resistances, inductances, capacitance, and transformers not only require the proper attention, but also decide the proper function of the active devices as well as the circuit as a whole. Here we shall discuss about some important electronic components and their characteristics, particularly used in Biomedical instruments. 1.1.0 ELECTRONIC COMPONENTS :

These can be classified into
1.1.1 Passive Components : Components like resistance, capacitance inductance, and fall in this class.
1.1.2 Active Components : They can be further classified as
Semiconductor Devices : Semiconductor diode, zener diode, and varactor diode etc. Uni-junction transistor, Bipolar junction transistor (BJT), FET, silicon, Controlled rectifier etc.
Vacuum Tube Devices : Vacuum tube diode, triode, Tetrode, Pentode, Hexode, Heptode etc.
Gas Tube Devices : Gas diodes, Thyratons etc.
Photo Sensitivity Devices : Gas photodiodes, photo multiplier tubes, photodiodes, light emitting diode, photosensitive transistor etc.
Though there are devices, which are specific to particular frequency range and applications like microwave devices etc.
1.1.4 RESISTANCES: Resistors can be made to control the flow of current, to work as Voltage dividers, to dissipate power and it can shape electrical waves when used in combination of other components. Basic unit is ohms, ()

Metal alloys, carbon and graphite used with binders etc. are the, usual resistive materials. The alloys used as resistance wire usually have higher specific resistances than the base metals and have lower temperature coefficient of resistance. The three most common types of resistance wire used are nickel-copper, nickel. Chromium-aluminum and nickel-chromium. Carbon and graphite are used as the basic resistance materials when they are mixed and heated with proper variety of resin binders. These types of resistances are generally known as composition carbon type’s resistors. The resistive element may be either in the form of a film or a solid slug, which consists of a number of conducting particles held together by resin. In the film type the base materials may be glass, ceramic and plastics. Resistors can be (i) fixed resistors with two ends, (ii) variable resistor or potentiometers. Resistors are specified by the value of resistance, in ohms maximum power dissipation in watts, and precision in %.

Types: Resistors can be designed in many ways by usage, shape, physical construction tolerances, resistances are of the following three types i.e. 1.1.6 FIXED RESISTORS:
The fixed resistances are those whose values cannot be changed. In case of semi variable types of resistances their values can be changed with help of a screwdriver. Semi variable types resistances are known as preset. In case of the variable resistances their values can be changed from zero to maximum with the help of a movable arm.

Types include : Metal oxide, non inductive, carbon composition, carbon...
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