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PN JUNCTION DIODE AS A RECTIFIER  A PN junction diode can act as a rectifier that is it can convert A.C. supply into  D.C. supply. The reason is that it acts as a switch.  When a diode is forward biased (during positive cycle) it conducts and behaves as a closed switch. When it is reversed biased (during negative cycle) it does not conduct and behaves as an open switch. A diode, therefore, is a unidirectional device i.e., it conducts only in one direction, this property of the diode makes it suitable as rectifier. TYPES OF SEMICONDUCTOR DIODE RECTIFIERS  We know that the generation, transmission and distribution of A.C. is economical but at few places, we need D.C. supply, e.g. in electronic devices and circuits. Here, we convert the available A.C. supply into D.C. supply. The process is called 'rectification' and the devices used for rectification are called 'rectifiers'.  The diode rectifiers can be classified as:  (1) Half wave rectifiers  (2) Full-...

MOSFET (OR MOS) OR IGFET The 'Metal oxide semiconductor field effect transistor (MOSFET or simply MOS) is another important category of field effect transistors. In many applications, JFET is being replaced by MOSFET due to favourable characteristics of the latter. The MOS may be of two types: 1. n-channel MOS or n-mos 2. p-channel MOS or p-mos According to the mode of operation, they can be depletion and enhancement types. 1. Construction of n-channel MOS: The n-MOS consists of a lightly doped p-type 'substrate' over which two highly doped n regions are diffused. These n regions act as source and drain and are separated by about 10-20µm. A thin layer of an insulating material (silicon dioxide, SiO 2 ) is grown over surface of the structure and holes are cut into the oxide layer to make contact with source and drain. After this the 'gate (of aluminium) is overlaid on silicon oxide layer. Covering the entire channel region, simultaneously similar metal contacts are m...

So far we have studied ordinary transistors which are also called Bipolar Junction Trans istors (BJT). But a BJT is noisy in operation and has low input impedance. Due to these  two factors BJTs are replaced by the new type of transistors called field effect transistors  (FETS), which have been proved to be very efficient device especially in I.C.  form. A FET is a three-terminal, unipolar semiconductor device in which current conduction takes place due to an electric field applied at its input. CLASSIFICATION OF FET FETs may be put into two major categories. 1. Junction field effect transistors. JFET or simply FET) The FETs may be an N-type or a P-type. 2. Insulated gate field effect transistors ( IGFET ) The IGFET are also called 'metal oxide semiconductor field effect transistors' (MOSFET or simply MOS). The MOSFETS are again of two types: (a) Enhancement MOSFET (b) Depletion MOSFET The ordinary FET is sometimes also known as JFET (Junction Field Effect Transisto...

The P and N-type semiconducting materials, when kept touching together, it gives  a PN Junction or a semiconductor diode. Popularly, it is known as "Rec tifier diode", as it is used for rectification purposes. The other semiconductor diodes used for other than rectification are Power diodes, Zener diodes and Varactor diodes. PN JUNCTION The P and N type materials taken separately are of no practical use, but PN Junction has vital importance in the field of electronics, as all semiconductors have one or more PN Junctions. When a piece of P-type material is kept with a piece of N-type material their contact surface is called a P-N junction. It is important that the crystal structure should remain continuous at the boundary, i.e., it should have a simple crystal structure. The P-N junctions are the control elements of all solid semi- conductor devices. The P-N junction is commercially known as a 'semiconductor diode' and has replaced the vacuum diode in many application...

ZENER DIODE A Specially designed silicon diode which is optimised to operate in the breakdown region is known as zener diode. The ordinary rectifier and small-signal diodes are never intentionally operated in the breakdown region because this may damage them. On the other hand, zener diodes are only operated in the breakdown region. Therefore, zener diodes are cryptically designed to have a sharp breakdown voltage. By varying the doping level of silicon diode, a manufacturer can produce zener diodes with breakdown voltages from about 2 to 200 V. It is similar to the symbol of an ordinary crystal diode except that its bar is just turned into Z-shape. CHARACTERISTICS OF A ZENER DIODE The V-I characteristics of a zener diode have the following points : (i) Its characteristics are similar to an ordinary rectifier diode with the exception that it has a sharp (or distinct) breakdown voltage called zener voltage (V z ).  (ii) It can be operated in any of the three regions i.e. forward, ...

INTEGRATED  CIRCUIT   The circuit in which various active and passive components such as transistors, diodes, capacitors, resistors etc. are the part of a small piece of semiconductor (silicon) chip is called integrated circuit.  An integrated circuit comprises of various components like resistors, diodes, transistors, capacitors  etc., and their inter-connections. All the components  and their inter connections are formed on a very small   piece of semiconductor wafer called chip. On the surface of this small chip, it is possible to produce circuits containing many transistors, diodes, resistors and capacitors. Thus, the components of ICs are very small and one needs a microscope to see the interconnections of these components. The following points are worth noting about integrated circuits : (i) No component of an integrated circuit can be removed or replaced since all the components are the integral part of a small semiconductor chip. (ii) No...

Transistor was first invented in 1948 by J. Bardeen and W.H. Brattain of Bell Telephone Laboratories U.S.A. Though transistor is only slightly more than 40 years old, yet it is fast replacing old electronic equipment (vaccum tubes like triode and pentode) in almost all applications because of its innumerable merits viz longer life, higher efficiency, more mechanical strength, light in weight, smaller in size, smaller power consumption etc. It is also known as Bipolar Junction Transistor (BJT) since its operation depends upon the interaction of both the majority and minority carriers. This device has now become more or less heart of most of the electronic applications.  TRANSISTOR  A semiconductor device consisting of two pn junctions formed by sandwitching either p-type or n-type semiconductor between a pair of opposite types is known as a transistor. Accordingly, there are two types of transistors, namely:  (ⅰ) npn transistor (ⅱ) pnp transistor (ⅰ) npn Transistor : A tr...

 INDUCTORS The electronic component (mostly a coil) which opposes the change of current in circuit is named an inductor. the power of the coil or inductor thanks to which it opposes the change of current flowing through it's referred to as its inductance. The inductance of an inductor can also be defined because the ability of an inductor (coil) to supply induced voltage when the present varies through it. The unit of inductance is henry which is known as after Henry . The schematic symbol of fixed and variable inductor. An inductor may be a component which offers high impedance to a.c. but very low impedance (opposition) to d.c. the standard function of an inductor, within the electronic circuit, is to dam a.c. signal but to pass d.c. signal (or voltage). The variable inductors are utilized in tuning circuits (for changing the resonant frequency) for radio frequencies. These also are used for impedance matching. TYPES OF INDUCTORS The inductors, like resistors and capacitors, can...

 CAPACITORS The two conducting plates separated by an insulant (called dielectric) forms a capacitor. The essential purpose of a capacitor is to store the charge. The capacity of a capacitor to store charge per unit electric potential is named its capacitance. The unit of capacitance is farads (F). However, the unit farad being overlarge , the capacitors are specified. practically in microfarads (µF) or picofarads (pF). A capacitor may be a component which offers low impedance to a.c. but very high impedance (resistance) to d.c. In most of the electronic circuits, a capacitor has d.c. voltage applied, combined with a way smaller ac. signal voltage. the standard function of the capacitor is to dam the d.c. voltage but pass the a.c. signal voltage, by means of charging and discharging. These applications include coupling, bypassing and filtering for a.c. signal. The schematic symbol of fixed and variable capacitor (C) is shown in figure. Types of Capacitors All the capacitors have t...

RESISTORS What is Resistor? Resistor is a component, used to limit the amount of current or divide the voltage in an electronic circuit. The ability of a resistor to oppose the current is called resistance. The unit of resistance R is ohm for which the symbol is 𝛀 (omega). Types of Resistors Each resistor has two main characteristics i.e. its resistance (R) in ohms and its power rating in watts (W). The resistors having wide range of resistance (from a fraction of an ohm to many mega ohms) are available.  The power rating may be as lower 1/10 W to as high as several hundred watts. The value of R is selected to obtain a desired current I or voltage drop IR in the circuit. At the same time wattage of the resistor is selected so that it can dissipate the heat losses without overheating itself. Too much heat may burn the resistor. From the operating conditions point of view, the resistors may be classified as fixed resistors and variable resistors. 1. Fixed Resistors The resistors w...

Electronic Circuits are designed to obtain a particular function. For this, a number of electronic components are suitably connected. Although we shall study the function of various components in detail, however, we shall study in general about these components. Electronic Components All the electronic circuits (simple to complex) contain a few basic components such as resistors, capacitors, inductors, tube devices and semiconductor devices. The first three components resistors, capacitors and inductors are called the passive components, whereas, the remaining two components tube devices (such as vaccum diode, vaccum triode, vaccum pentode, gas diode, thyratron etc.) and semiconductor devices (such as junction diode, zener diode, transistor, field-effect transistor, unijunction transistor, silicon control rectifier, tunnel diode etc.) are called the active components. Passive Components The electronic components which are not capable of amplifying or processing an electrical signal are...