# Key Points of Electronics

KEY POINT OF ELECTRONICS

• Electronics: Electronics engineering is the branch of engineering which deals with current conduction through vacuum or gas semiconductor.
The basic electronics device is the PN junction diode. The diode is a two terminal device, and the current voltage (I-V) relation is non-linear.
The electron will start to move from one point to another point inside the conductor if a voltage source is connected across it. This flow of electron through a conductive path is called current.

• Direct Current (D.C): Direct current is a unidirectional current whose magnitude does not change with respect to time. This unidirectional current is denoted by the capital letter I. The current with small variation in magnitude with respect to time is also known as unidirectional.

• Alternating Current (A.C): Alternating current is the most common that is found everywhere. In the household, it is used to run washing machines, fridges, electric irons and many other electrical appliances.
In order to move any object from one place to another place some energy is expended. Voltage is the amount of driving force or energy that is required to move the charge from one terminal to another terminal in the conductor.

• Potential Difference: The difference between any two object can be determined in terms of their height, weight and energy. The difference in energy of two objects. A1 and A2 can be determined either by the energy of the object A1 is higher or lower than the object A2.

• Independent Source: A source is said to be independent when it does not depend on any other quantity in the circuit.
Output characteristics of an independent source are not dependent on any network variable such as current or voltage. However, may be time-varying. There are two types of independent source:
1) Independent voltage source
2)Independent current source

• Dependent Source: A dependent source is one which depends on some other quantity in the circuit which may be either a voltage or a current.
If the voltage or current of source depends on some in turn upon some other voltage or current, it is called as dependent or controlled source.

• Energy: The power utility companies are mainly responsible for handling electric energy among difference types of consumers. Energy is also an important parameter in the power utility companies. The expression for energy is ,
Energy= Power*time

• VI Characteristics:  The VI characteristics of a diode is the combination of its forward as well as reverse characteristics.
In forward characteristics, it is seen initially forward current is small as long as the bias voltage is less than the barrier potential. At certain voltage aloes to barrier potential increase rapidly.
In reverse it is important note that breakdown voltage is much higher and practically diodes are not operated the breakdown (VBR).
• Conductance: The term conductance was introduced by the German Scientist Werner Von Siemens. Conductance is the reciprocal of the resistance. It is denoted by the capital letter G.
A capacitor stores energy in the form of electric field. A capacitor consists of two conducting plates separates by the insulating material called dielectric.

• Inductor: Inductor store energy in the form of magnetic field. It has a winding of a conducting wire over a core which can be made of iron or just itself. The current flowing through the coil establishes a magnetic field through the core.

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• Resistor: Resistor is a passive component, which generate equally voltage drop for AC and DC voltage. Resistor is a dissipative element.
Resistance is defined as an electronics component which is manufactured with a specified amount of resistance. A resistor conducts current in both directions.

• Grounding: All electrical devices need to be grounded for safety purposes. During lighting and switching activities, a high magnitude current appears in the electrical device.
This high magnitude of current normally passes to a grounded if the devices are connected with the proper grounding system.

• Voltage and Current Source: Voltage source are power supplies such as batteries, alternators, dynamos, etc. Metaldyne generators, photoelectric cells, collector circuits of transistors are current sources. All these are known as independent voltage and current source respectively.

• Active Components: Active components are those which are capable to deliver or absorb energy continuously.
Active components are those which are capable to amplify the voltage or power of the circuit.
The main active components are: - Junction diode, Transistor, FET, LED, SCR, Zener diode, Tunnel diode, etc.

• Passive Components: Passive components are those which are not capable of processing or amplifying an electrical signal.
But these components are an important part of an electronics circuit because without the aid of these components. Passive have three types:
1)Resistor
2)Capacitors
3)Inductors

• Shielding: When a magnetic material is subjected to alternating flux, then along with change in flux, the physical dimension of the magnetic material also change. Due to this continuous reversal flux, the continuous change in the physical dimension occurs, which causes a humming noise. The controlling of this humming noise is called shielding.

• Electrostatic: Electrostatic capacitor is manufactured by two metal conductors or plates which are separated by a dielectric. These have very low leakage current and high leakage resistance. There are different types of this capacitor are: Paper capacitors, Mica capacitors, Glass capacitors, plastic capacitors, ceramic capacitors.

• Electrolytic: Electrolytic capacitors are manufactured by metal plates having a definite polarity and are separated by a thin metal oxide dielectric. This metal oxide film is deposited on one of the metal plates. This capacitor of are classified into two types: Aluminium Electrolytic capacitor, Tantalum Electrolytic capacitor.

• Ohm-Meter: The circuit arrangement for measuring the resistance using ohm-meter. The unknown resistance Rx is connected between AB Rx with one of R1, R2, R3 and Rfrom potentiometer. The meter deflects with potentiometer output voltage.

• Voltage: The circuit arrangement for measuring the resistance using voltmeter method. The switch S is kept in position A and voltage E is measured. Next the switch is thrown in position B and the voltage is measured.

• D.C Source: D.C Sources are those sources which supplies a direct current to the load.

• A.C Source: A.C Sources are those sources which supplies alternating current to the load.

• Insulator: Insulator is material that offers large resistance to the flow of current through them. Typically resistivity level of an insulator is of the order 10­­10 to 1012 Ω-cm. Valence electron are tightly bound to the atom so there are no free electron that can move through the materials. Some of popular insulator can be put as Mica, Glass and Quartz. The forbidden band gap is greater than 5ev.

• Conductor: Conductor offer very little resistance to the flow of current through them. Resistivity level of conductors is of the order of 10-4 to 10-6 Ω-cm. Generally, conductor have three or less than three valence electron. When we apply an external field across the conductors, there flows a large current through the conductor. Lead (Pb) has zero energy gap (= 0 eV).

• Semiconductor: Semiconductor has conductivity levels between extremes of a conductor and an insulator. The resistivity level of semiconductor is of the order of 10 to 104 Ω-cm. They have mostly four electrons in the valence shell. Also materials having three or five valence electrons combine with each other to form semiconductors.

• P-N Junction Diode: A junction is formed by a placing p-type and n-type intimate to each other on a atomic scale. A p-n junction is a two terminal device and hence it is also known as diode. Diode represents two electrodes-cathode and anode. Anode refers top-type side of p-n junction while cathode refers to p-type side of p-n junction.
Holes are represented by plus (+) sign in p-type region while electrons are represented by minus (-) signs.

• LED (Light Emitting Diode): Light emitting diode is a photoelectric device which converts electrical energy into light energy. It is a heavily doped p-n junction diode which under forward bias emits spontaneous radiation. The diode is covered with transparent cover so that the emits light may come out.

• Photo diode: A silicon photodiode is a solid-state device which converts light into an electric current. This is a diode optimized to produce an electron current flow in response to irradiation by ultraviolent, visible, or infrared light.

• Transistor: A transistor consist of two p-n junction formed by sand witching either p-type or n-type semiconductor between a pair of opposite types. There are two PN junctions. Therefore a transistor may be regarded as a combination of two diodes connected back to back. The middle section is very thin. This is the most important factor in the function of a transistor.
There are two types of transistor are possible namely
1) n-p-n transistor
2) p-n-p transistor.

• Biasing: Biasing of a transistor is needed to restrict the operation of a transistor in the active region. The biasing circuit provides a DC current and voltage so that they correspond to a point in the linear region of the output characteristics.

• FET (Field Effect Transistor): In field effect transistor, the flow of current through the device is controlled by an applied electric field across the same conducting region. Since the current is carried by majority carrier only, the FET is said to be a unipolar device.

• CMOS (Complementary Metal Oxide Semiconductor): With active –load switching, the current drain with a low output is approx. equal to ID(sat). This may create problem with battery-operated equipment. One way to reduce the current drain of the digital circuit is with complementary MOS.

• PMOS (P-Channel Enhancement MOSFET): The construction of P-channel enhancement type MOSFET. The construction of p-channel enhancement type MOSFET is exactly reverse of the N-channel enhancement type MOSFET. In this construction, N-type substrate and P-doped regions under the source and drain terminals.

• MOSFET (Metal Oxide Semiconductor Field Effect Transistor): The MOS Field Effect Transistor is the fundamental building block of MOS digital integrated circuits. The technological advantages, together with relative simplicity of MOSFET operation, have helped make the MOS transistor the most widely used switching device in VLSI circuits.

• IC (Integrated Circuit): An integrated circuit is an electronics circuit in which all the active and passive components are fabricated on a single crystal chip.

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