Unit I Electronic Components And Signals - WordPress

Unit – IElectronic Components and Signals

Index1.11.21.31.4Active and passive components.Voltage and Current Source.Symbols of various Semiconductor components.Definitions of: amplitude, Frequency, Phase,Wavelength1.5 Definitions of: Signal, waveform, spectrum, Timeand frequency domain representation1.6 Test Signals: unit step, unit impulse, and unit ramp1.7 Types of Signals: sinusoidal, triangular andsaw tooth, square

IntroductionElectronics can be divided into two parts :(1) Analog electronics and (2) Digital electronicsThe branch of electronics in which processing of analogsignal is done is called the analog electronics.The value of analog signal is continuous with respect totime e.g. sine wave

Analog electronic circuit include signal amplifier ,power amplifier , oscillator etc.Electronic component can be divided into two parts:(1) Active component and (2) Passive component

Basic quantities: current, voltage and powerCurrent: time rate of change of electric chargeI dq / dtNormally we talk about the movement of positivecharges although we know that, in general, in metallicconductors current results from electron motion(conventionally positive flow)The sign of the current indicates the direction of flow

Voltage: electromotive force or potential, V 1 Volt 1Joule/Coulomb 1 N·m/coulombVoltage is the difference in energy level of a unit chargelocated at each of two points in a circuit, and therefore,represents the energy required to move the unit chargefrom one point to the otherPower:P IV1 Watt 1 Volt·Amp 1 Joule/sec

1.1 Active and passive components.Passive component: A passive component can not deliver power orcannot process the electrical signal are known asthe passive component. E.g. resistor ,inductor,capacitorActive component: An Active component is that which is capable ofdelivering power to some external device.E.g. voltage source or current source

Passive component1.) Resistor: The property of material to oppose the flow ofelectric current through it is known as the resistance. Electric current flows due to the flow of electron. Resistance of conductor isR ƍ l /aƍ Specific resistancel length of conductora area of cross section of conductor

Its unit is ohm and it is denoted by Ω. When V volts are applied across a conductor havingresistance of R ohm and current I ampere flows.I V/R Power is wasted in it due to current flow.P VI V.V/R V2/ RORP VI IR .I I2R

2.) Capacitor When an insulating material is placed betweentwo conducting plates a capacitor is formed. The ability of capacitor to store electric charge iscalled the capacitance and the symbol of its is Cand its unit is farad(F)C Q /V

3.) Inductor An inductor is a coil of wire which may have a coreof air, iron or ferrite (a brittle material made fromiron). Its electrical property is called inductance andthe unit for this is the Henry, symbol H.L NΦ / l

Active component:1.) Voltage source: A Voltage source may be a d.c.or an a.c. A d.c. Voltage source is batteryand an a.c. Voltage source isobtained from a.c. supply.2.) Current source: A current source may be a d.ccurrent source or an a.c. currentsource.

1.2 Voltage source and current source.Ideal and Practical Voltage source. Ideal voltage source is not possible in actualpractice.

Ideal voltage source has some internal resistance which isin series with it. So when the current drawn from thevoltage source some voltage drop occurs across theinternal resistance so the terminal voltage of the voltagesource decreases.

Ideal and Practical Current source. Ideal current source does not exists. The ideal currentsource has no resistance or impedance . Ideal current source can supply constant current to anyvalue of the resistance or impedance connected acrossit.

The practical current source has resistance or impedanceand it is in parallel to it. The current supplied by thecurrent source decreases when the value of resistance orimpedance increases.

1.3 Symbols of various Semiconductorcomponents.1. PN junction diode2. Zener diode

3. Tunnel diode4. Varactor diode5. Photo diode

6. Light Emitting Diode(LED)7. Light Dependent Resistor8. PNP Transistor

9. NPN Transistor10. NPN photo Transistor11. PNP photo Transistor

12. N-channel junction field effect transistor13. P-channel junction field effect transistor

14. N-channel enhancement mode IGBT or MOSFETor NMOS15. P-channel enhancement mode IGBT or MOSFETor PMOS

16. Silicon Controlled Rectifier17. Triac18. Diac

1.4 Definitions of: amplitude, Frequency, Phase,WavelengthAmplitude or Maximum value: The maximum value of the alternating quantity iscalled the Amplitude or Maximum value. This value is maximum positive value or maximumnegative value. The maximum value is 50V

Frequency: The number of cycles completed in one second is knownas the Frequency. It is represented by f. Its unit is hertz(Hz). These are in the range of KHz or MHz.

Phase: Phase means the time required to reach to certain value. It can be shown in degrees or in radian.

Wavelength: Wavelength means the length of one wave. The distance between two consecutive positivepeaks a and b is called Wavelength. It is denoted by λ.λ v/f

1.5 Definitions of: Signal, waveform, spectrum,Time and frequency domain representationSignal: The is given as reference to the input when analysis ofthe circuit or device or the system has to be done. There are different type of signal1.) Impulse signal2.) Step signal3.) Ramp signal

Ramp signalStep signalImpulse signal

Waveform: When the signal repeats with respect to time, it is calledthe waveform. There are different types of waveform.1.) Sine wave2.) Square wave3.) Triangular wave4.) Saw tooth wave

Spectrum: In the waveform variation of the magnitude of the signalis shown with respect to time. When the magnitude ofthe signal is plotted against the frequency, it is knownas the spectrum.

Time and frequency domain representation: When the study of thebehavior of the system andthe analysis of the system isdone on the basis of the time,it is known as the analysis inthe time domain.

When the analysis ofthe system is done onthe basis of thefrequency, it is knownas the frequencydomain analysis.

1.6 Test Signals: unit step, unit impulse, and unitrampTest Signals: unit step Step signal means sudden change in the level of thesignal from one value to another value. This change is considered from zero level. This signal is given byr(t) A for t 0r(t) 0 for t 0

The unit step signal , the signal level increasessuddenly from 0 to 1 level. It is given byr(t) 1 for t 0r(t) 0 for t 0

Test Signals: unit impulse The signal which exists for very small periodof time is known as the impulse signal.

Unit impulse signalIn this a pulse of very small width but of unit magnitude. Thisis called the unit impulse.An impulse function is define as the derivative of u(t).δt d/dt u(t)

Test Signals : unit ramp The signal whose value increases linearly, it is called theramp signal. It is the integration of the step signal. This ramp increases from zero value. It is given as below.r(t) At for t 0r(t) 0 for t 0

Unit ramp signal is given as belowr(t) t for t 0r(t) 0 for t 0(i.e. A 1)

1.7 Types of Signals: sinusoidal, triangular andsaw tooth, squareTypes of Signals: Sinusoidal In the sine wave signal themagnitude of the signal varies asthe sine of the angular frequency. It is recurring type signal. It is also called the periodic signal.

Types of Signals: Triangular Triangular wave is shown in fig.

Types of Signals : Saw tooth The shape of this type of wave is like the tooth of saw. In this the magnitude of the signal increases linearlyduring time period T1 and decreases linearly to 0 duringthe time period T2. T2 is very much less than T1.

Types of Signals : Square This signal is of symmetrical type or of asymmetrical type. Fig. (a) is the symmetrical type signal. In this the ON timeT1 and the OFF time T2 are equal. Fig. (b) and (c) is the asymmetrical type signal. In this theON time T1 and the OFF time T2 are not equal.

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1.1 Active and passive components. Passive component: Active component: A passive component can not deliver power or cannot process the electrical signal are known as the passive component. E.g. resistor ,inductor, capacitor An Active component is that which is capable of delivering power to some external device.