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INTRODUCTION TO ELECTRONICS
ELECTRONICS
● The Study of Electricity ● Electronics is a branch of physics that deals with the emission, behavior, and effects of electrons (as in electron tubes and transistors) and with electronic devices. It is a much more subtle kind of electricity in which tiny electric currents (and, in theory, single electrons) are carefully directed around much more complex circuits to process signals (such as those that carry radio and television programs) or store and process information.
RESISTOR
● A resistor is a passive two-terminal component that implement electrical resistance as a circuit element. Resistors act to reduce current flow, and at the same time, act to lower voltage levels within circuits. In electronic circuits, resistors are used to limit current flow, to adjust signal level, bias active elements and terminate transmission lines among other uses TYPES OF RESISTORS
● FIXED RESISTOR
○ a resistor having a fixed, defined electrical resistance which is not adjustable. ● VARIABLE RESISTOR ○ a resistor of which the electrical resistance value can be adjusted
CAPACITORS
● Just like the Resistor, the Capacitor, sometimes referred to as a Condenser, is a simple passive device that is used to “store electricity”. The capacitor is a component which has the ability or “capacity” to store energy in the form of an electrical charge producing a potential difference (Static Voltage) across its plates, much like a small rechargeable battery TYPES OF CAPACITORS
● DIELECTRIC CAPACITOR
○ usually of the variable type were a continuous variation of capacitance is required for tuning transmitters, receivers and transistor radios ● CERAMIC CAPACITORS ○ are made by coating two sides of a small porcelain or ceramic disc with silver and are then stacked together to make a capacitor ● FILM CAPACITOR ○ most commonly available of all types of capacitors, consisting of a relatively large family with the difference being in their dielectric properties. ● ELECTROLYTIC CAPACITORS ○ used when very large capacitance values are required.
INDUCTORS
● An inductor is a passive component that is used in most power electronic circuits to store energy in the form of magnetic energy when electricity is applied to it. Faraday invented the inductor while discovering the phenomenon of electromagnetic induction nearly two hundred years ago. ● It uses a conductor that is wound into a coil, and when electricity flows into the coil from the left to the right, this will generate a magnetic field in the clockwise direction. ● Major purposes: Choking, blocking, attenuating, or filtering/smoothing high frequency noise in electrical circuits. Storing and transferring energy in power converters (dc-dc or ac-dc) TYPES OF INDUCTORS
● FIXED CONDUCTOR
○ is a type of inductor which always has the same inductance. ■ AIR-CORE INDUCTOR ■ IRON-CORE INDUCTOR ■ FERRITE-CORE INDUCTOR ● VARIABLE CONDUCTOR ○ Inductance of a variable inductor is varied by increasing or decreasing the number of turns through movable contract on top of the windings. When the contact on top of the turn is moved, the number of effective turns will change. The inductance varies with the number of turns.
BASIC OF SEMICONDUCTOR
WHAT IS
SEMICONDUCTOR
● A semiconductor is a substance that has specific electrical properties that enable it to serve as a foundation for computers and other electronic devices. ● Semiconductors are the materials which have a conductivity between conductors (generally metals) and non- conductors or insulators (such as ceramics). ● Semiconductor are “part-time” conductors whose conductivity can be controlled.
SEMICONDUCTOR
● Semiconductors are employed in the manufacture of various kinds of electronic devices, including diodes, transistors, and integrated Circuits. ● Examples of Semiconductors: ● Gallium arsenide, germanium, and silicon are some of the most commonly used semiconductors. Silicon is used in electronic circuit fabrication and gallium arsenide is used in solar cells, laser diodes, etc
SEMICONDUCTORS
MATERIALS
● Single Crystal ○ Single Crystal semiconductors such as germanium (GE), and silicon (SI) have a repetitive crystal structure. ● Compound ○ Compound semiconductors such as gallium arsenide (GaAs), cadmium sulphide (CdS), gallium nitride (GaN), and gallium arsenide phosphide (GaAsP) are constructed of two or more semiconductor materials of different atomic structure.
What is Energy Band
● The energy band definition is, the number of atoms within a crystal stone can be nearer to each other as well as a number of electrons will interact with each other. The energy levels of electrons within their shell can be caused due to the changes in their energy levels. The main feature of the energy band is that the electron’s energy states of electronics are stable in different ranges. So, the level of energy of an atom will change in conduction bands & valence bands
Energy Band Theory
● The electrons move in the atoms in certain energy levels but the energy of the electrons in the innermost shell is higher than the outermost shell electrons. The electrons that are present in the outermost shell are called as Valance Electrons. These valance electrons, containing a series of energy levels, form an energy band which is called as Valence Band. The valence band is the band having the highest occupied energy.
Classification of Energy Band
● Valance Band ○ The electrons move in the atoms in certain energy levels but the energy of the electrons in the innermost shell is higher than the outermost shell electrons. The electrons that are present in the outermost shell are called as Valance Electrons. These valance electrons, containing a series of energy levels, form an energy band which is called as Valence Band. The valence band is the band having the highest occupied energy. ● Conduction Band ○ The valence electrons are so loosely attached to the nucleus that even at room temperature, few of the valence electrons leave the band to be free. These are called as free electrons as they tend to move towards the neighboring atoms. These free electrons are the ones which conduct the current in a conductor and hence called Conduction Electrons. The band which contains conduction electrons is called the Conduction Band. The conduction band is the band having the lowest occupied energy. ● Forbidden Gap ○ The gap between valence band and conduction band is called as forbidden energy gap. As the name implies, this band is the forbidden one without energy. Hence no electron stays in this band. The valence electrons, while going to the conduction band, pass through this. The forbidden energy gap, if greater, means that the valence band electrons are tightly bound to the nucleus. Now, in order to push the electrons out of the valence band, some external energy is required, which would be equal to the forbidden energy gap. The following figure shows the valence band, conduction band, and the forbidden gap. Depending upon the size of the forbidden gap, the Insulators, the Semiconductors and the Conductors are formed.
TYPES OF ENERGY BAND ●^ INSULATORS
○ Insulators are such materials in which the conduction cannot take place, due to the large forbidden gap. ○ Examples: Wood, Rubber. The structure of energy bands in Insulators is as shown in the following figure. ○ The following are the characteristics of Insulators. ■ The Forbidden energy gap is very large. ■ Valance band electrons are bound tightly to atoms. ■ The value of forbidden energy gap for an insulator will be of 10eV. ■ For some insulators, as the temperature increases, they might show some conduction. ■ The resistivity of an insulator will be in the order of 107 ohmmeter. ○ ● SEMICONDUCTORS ○ Semiconductors are such materials in which the forbidden energy gap is small and the conduction takes place if some external energy is applied. ○ Examples: Silicon, Germanium. The following figure shows the structure of energy bands in semiconductors. ○ The following are the characteristics of Semiconductors. ■ The Forbidden energy gap is very small. ■ The forbidden gap for Ge is 0.7eV whereas for Si is 1.1eV. ■ A Semiconductor actually is neither an insulator, nor a good conductor. ■ As the temperature increases, the conductivity of a semiconductor increases. ■ The conductivity of a semiconductor will be in the order of 102 mhometer. ● CONDUCTORS ○ Conductors are such materials in which the forbidden energy gap disappears as the valence band and conduction band become very close that they overlap. ○ Examples: Copper, Aluminum. The following figure shows the structure of energy bands in conductor ○ The following are the characteristics of Conductors. ■ There exists no forbidden gap in a conductor.
Breakdown in Junction Diode
● Avalanche breakdown ○ is a phenomenon that can occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwise good insulators. It is a type of electron avalanche. ● Zener breakdown ○ occurs in heavily doped junctions in which the transition from the p side to the n side is very abrupt. Under these conditions, the potential barrier separating carriers on the two sides of the junction is very narrow, and a quantum mechanical process called tunneling can take place.
Zener Diode
A specially designed silicon diode which is optimized to operate in the breakdown region is known as zener diode. Characteristics of Zener Diode
- Its characteristics are similar to an ordinary diode with the exception that it has a sharp (or distinct) breakdown voltage called zener voltage 𝑣𝑧
- It can be operated in any of the three region i.e. forward, leakage or breakdown. But usually it is operated in the breakdown region.
- The voltage is almost constant (𝑣𝑧) over the operating region.
- Usually, the value of (𝑣𝑧) at particular test current 𝐼𝑧𝑟 is specified in the data sheet.
- During operation it will not burn as long as the external circuit limits the current flowing through it below the burn out value i.e 𝐼𝑧𝑚 (the maximum rated zener current). Application
- Meter Protection
- Voltage Regulator
- Wave Shaping Circuit
Photo Diode ●^ A diode that is optimized for its sensitivity to light is known as photodiode.
LED (Light Emitting Diode)
● A light-emitting diode (LED) is a semiconductor device that emits light when an electric current flows through it. When current passes through an LED, the electrons recombine with holes emitting light in the process. LEDs allow the current to flow in the forward direction and blocks the current in the reverse direction. ● Light-emitting diodes are heavily doped p-n junctions. Based on the semiconductor material used and the amount of doping, an LED will emit coloured light at a particular spectral wavelength when forward biased.
Diode as Rectifier
● The electrical power is generated transmitted and distributed as d.c. for economical reasons. As an alternating voltage is available at the mains. But most of the electronic circuit need d.c. voltage for their operation. Therefore the rectifier is the heart of power supply. The rectifier can be of two types: ○ Half Wave Rectifier ○ Full Wave Rectifier
Half Wave Rectifier
● In half wave rectifier when a.c. supply is applied at the input only positive half cycle appears across the load, whereas the negative half cycle is suppressed.
Full Wave Rectifier
● In this case aan ordinary transformer is used in place of a centre taped transformer. The circuit contains four diodes D1, D2, D3 and D4 connected to form a bridge.
Voltage multiplier
● A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage Types of Voltage multiplier
- Half-wave voltage doubler is a voltage multiplier circuit whose output voltage amplitude is twice that of the input voltage amplitude.
- Full-wave voltage doubler is a voltage multiplier with a multiplication factor of two.
- Voltage tripler is the circuit where we get the thrice of the peak input voltage
- Voltage quadrupler is a circuit in which the output voltage is quadruple, or 4 times, the amplitude of the input voltage.
Zener diode regulator
● helps to regulate voltage across small loads. A Zener diode is a semiconductor device with a p-n junction causing the current to flow in a forward or backward direction.
FILTER
● What Is a Filter? A filter is a circuit capable of passing (or amplifying) certain frequencies while attenuating other frequencies. Thus, a filter can extract important frequencies from signals that also contain undesirable or irrelevant frequencies. ● Electronic filters remove unwanted frequency components from the applied signal, enhance wanted ones, or both. They can be: passive or active. analog or digital.
CLIPPER CIRCUITS
● In electronics, a clipper is a circuit designed to prevent a signal from exceeding a predetermined reference voltage level. A clipper does not distort the remaining part of the applied waveform. ● Clipper Circuits are used to clip off a portion of wave from an input signal. Main element is diode and it is used in two ways series and parallel.
CLAMPER CIRCUITS
● A clamper (or clamping circuit or clamp) is an electronic circuit that fixes either the positive or the negative peak excursions of a signal to a defined voltage by adding a variable positive or negative DC voltage to it
● Clipper and clamper circuits are electronic circuits used for the modification of AC signals. ● The clipper circuit can clip a portion of the AC waveform while the clamper shifts the DC level of the AC signal. They are quite different yet have almost similar circuit designs.
● The value of input resistancep1 is very low. Its value further decrease with the increase in collector base voltage Vcb since the curve tends to become more vertical. The typical value of input resistance varies from a few ohms to 100 ohms.
OUT CHARACTERISTICS
● In CB configuration, the curve plotted between collector current Ic and collector base voltage Vcb at constant emitter current Ig is called output characteristics. Number of characteristics curves can be plotted for different settings of Vcb. Fig.7 shows the input characteristics of a typical pnp transistor in common base configuration.
OUTPUT RESISTANCE
● The ratio of change in collector base voltage (delta Vcb) to the resulting change in collector current (delta Ic) at constant emitter current (Ie) is known as output resistance, i.e ● output resistance, r0 = delta Vcb/delta Ic at constant Ie.
CHARACTERISTICS OF
COMMON EMITTER
CONFIGURATION (CE)
● To determine the characteristics of a transistor in CE Configuration, the circuit is arranged to this.
INPUT
CHARACTERISTICS
● In CE configuration the curve plotted between base current Ib and the emitter base voltage Vbe at constant collector emitter voltage Vce is called input characteristics. ● ●
INPUT RESISTANCE
● The ratio of change in emitter base voltage (delta Veb) to the resulting change in base current (delta Ib) at constant collector emitter voltage (Vce) is known as input resistance, i.e Ri = delta Vbe/delta Ib at constant Vcb ● In CE configuration, the typical value of input resistance is of the order of a few hundred ohms.
OUTPUT
CHARACTERISTICS
● In CE configuration, the curve plotted between collector current Ic and collector emitter voltage Vce at constant base current Ib is called output characteristics. A number of characteristics curves can be plotted for different settings of Ib.
OUTPUT RESISTANCE
● The ratio of change in collector emitter voltage (delta Vce) to the resulting change in collector current (delta Ic) at constant base current (Ib) is known as output resistance, i.e Ro=delta Vce/delta Ic at constant Ib ● The output resistance of CE configuration is less than the CB configuration as the slope of output characteristics is more in this case. Its value is of the order of 50 kilo ohm.
CMOS
● A complementary metal-oxide semiconductor (CMOS) is the semiconductor technology used in most of today’s integrated circuits (ICs), also known as chips or microchips. CMOS transistors are based on metal-oxide semiconductor field-effect transistor (MOSFET) technology. It has extensive application in computer logic design the relatively high input impedance, fast switching speeds, and lower operating power levels of the CMOS configuration have resulted in a whole new discipline referred to as CMOS logic design.
VMOS TRANSISTOR
● Is a type of MOSFET (metal–oxide–semiconductor field-effect transistor). VMOS is also used for describing the V-groove shape vertically cut into the substrate material. VMOS is an acronym for “vertical metal oxide semiconductor”, or “V-groove MOS”. Vertical metal oxide silicon FET(VMOS). The term vertical is due primarily to the fact that the Channel is now formed in the vertical direction rather than the horizontal direction as for the Planar device.
JFET
● Stands for junction field effect transistor. The JFET is a three terminal semiconductor device and the terminals are: Source (S), Drain (D) and Gate (G). JFET has a channel between source and drain. The channel is the path between the source and drain for current to flow. ● The junction field effect transistor (JFET) can only be operated in the depletion mode. It is used in various applications like voltage variable resistor, digital switch, amplifier, etc.
MOSFET
● Stands for metal oxide semiconductor field effect transistor. The MOSFET is a four terminal semiconductor device where the terminals are: source (S), drain (D), gate (G) and body (or substrate). MOSFET is a field effect transistor with a MOS structure. MOSFETs are high speed and low-loss operation transistors.
CHARACTERISTICS OF
VARIOUS TRANSISTORS
● Input Characteristics ○ The curve describes the changes in the values of input current with respect to the values of input voltage, keeping the output voltage constant. ● Output Characteristics ○ The curve is obtained by plotting the output current against output voltage, keeping the input current constant. ● Current Transfer Characteristics ○ This characteristic curve describes the variation of output current in accordance with the input current, keeping the output voltage constant.
TRANSISTORS AMPLIFIER AND APPLICATION
INTRODUCTION TO
AMPLIFIERS
● No electronics system can work without an amplifier. ● Can the voice of a singer reach everybody in the audience in a hall if the PA system (Public Address system) fails? It is just because of the enlargement or the amplification of the signal picked up by the microphone that we can enjoy a music orchestra. ● Amplification means enlargement of a weak signal by an electronic circuit without any distortion in the signal. The electronic circuit or device which amplifies the signal is known as Amplifier.
Single - stage Amplifier
● An electronic circuit which uses only a single transistor with a proper bias and additional components based on the requirements that will provide an output. COMPONENTS OF SINGLE-STAGE AMPLIFIER ● Biasing Circuit ● Coupling Capacitor ● Bypass capacitor
MULTI-STAGE
AMPLIFIER
● A multistage amplifier is a type of electronic amplifier that is made up of two or more single-stage amplifiers that are linked together.
AMPLIFIER
CHARACTERISTICS
● Gain ○ the ratio between the magnitude of output and input signals ● Bandwidth ○ the width of the useful frequency range ● Efficiency ○ the ratio between the power of the output and total power consumption ● Linearity ○ the extent to which the proportion between input and output amplitude is the same for high amplitude and low amplitude input ● Noise ○ a measure of undesired noise mixed into the output ● Output Dynamic Range ○ the ratio of the largest and the smallest useful output levels ● Slew Rate ○ the maximum rate of change of the output ● Rise Time ○ the time taken for the output to change from 10% to 90% of its final level when driven by a step input. ● Settling Time ○ the time taken for the output to settle to within a certain percentage of the final value ● Ringing ○ to an output variation that cycles above and below an amplifier's final value and leads to a delay in reaching a stable output. ○ the result of overshoot caused by an underdamped circuit. ● Overshot ○ the amount the output exceeds its final, steady-state value ● Stability ○ the ability to avoid self-oscillation
FEEDBACK AMPLIFIER
● It can be defined as an amplifier which has feedback lane that exists between o/p to input. In this type of amplifier, feedback is the limitation which calculates the sum of feedback given in the following amplifier.
TYPES OF FEEDBACK
AMPLIFIERS
● Positive Feedback ○ It is a type of amplifier in which the source signal and the feedback signal are in the same phase. Thus, the feedback signal applied increases the strength of the input signal. ● Negative Feedback ○ In this type of amplifier source signal and the feedback signal are out of phase with each other. Thus, the feedback signal is applied to decrease the strength of the input signal.
MULTIVIBRATORS (MVS)
● These devices are very useful as pulse generating, storing and counting circuits. They are basically two-stage amplifiers with positive feedback from the output of one amplifier to the input of the other. Feedback is supplied in such a manner that one transistor is driven to saturation and the other to cut-off. There are three basic types of AMVs:
- Astable multivibrator (AMV)
- Monostable multivibrator (MMV)
- Bistable multivibrator (BMV) Uses of Multivibrators
- As frequency divider.
- As sawtooth generators.
- As square wave and pulse generators.
- As a standard frequency source.
- Specialized uses in radar and TV circuits.
- As memory elements in computers.
