Capacitor Types and Values PDF

Module 4 Introduction to Semiconductor devices: ⮚ Evolution of electronics – Vacuum tubes to nano electronics. ⮚ Resistors, Capacitors and Inductors: types, specifications. Standard values, color coding. ⮚ PN Junction diode: Principle of operation, V-I c...

Module 4 Introduction to Semiconductor devices: ⮚ Evolution of electronics – Vacuum tubes to nano electronics. ⮚ Resistors, Capacitors and Inductors: types, specifications. Standard values, color coding. ⮚ PN Junction diode: Principle of operation, V-I characteristics, principle of avalanche breakdown. ⮚ Bipolar Junction Transistors: PNP and NPN structures, Principle of operation, relation between current gains in CE, CB and CC, input and output characteristics of common emitter configuration.  Capacitor Used to store electric charge It consist of two metal plates separated by a dielectric medium. Capacitance is a measure of amount of charge which can be stored within a capacitor. The SI unit of capacitance is the farad (F). Units: μF, nF, pF  Capacitor When a battery is connected across the capacitor, capacitor gets charged. If the battery is removed ,it discharges through the available path Capacitor passes AC signal and blocks DC signal If a capacitor is connected in series between two circuits, it will pass ac signal and block DC signal from first circuit to next If a capacitor is connected in shunt between two circuits, it will bypass ac signal without letting the AC signal from first circuit to next Capacitors are widely used in signal generation, tuning , timing ,filtering etc The ratio of the charge Q to the voltage V will give the capacitance value of the capacitor and is therefore given as: C = Q/V Q=CxV Another equation is: A – area of plate d – distance between plates - permittivity of dielectric  Capacitor Types Fixed Capacitor Variable Capacitor  Types of fixed capacitors Electrolytic Capacitor – used when large capacitor values are required. – The thin metal film layer is used for one electrode and for the second electrode (cathode) a paper saturated with a semi- liquid electrolyte solution which is in jelly form is used. The dielectric plate is a thin layer of oxide. – electrolytic capacitors are polarized(If DC voltage is applied to the capacitor terminal and they must be in correct polarity) Capacitor Range:1µF to 47000µF Voltage Range: 1V to 500 V Use in filter circuits and for coupling and decoupling  Ceramic Capacitor – a type of non-polar capacitor in which the dielectric used is a ceramic material like titanium and barium – Manufactured by coating a ceramic disc with silver and leads are attached on both sides. The entire unit is coated with plastic. – No polarity – Capacitor range:1pF to 0.22µF – Used in high frequency applications  Mica Capacitors – Mica capacitor is a non- polar capacitor – Dielectric is Mica – Constructed using plates of Aluminium foils, separated by sheets of mica. Aluminium plates are connected to two electrodes at the ends. – Used in resonance circuits, filtering of ripples in power supply circuits Capacitor Range: 5 to 10,000pF Voltage Range:up to 500V  Paper Capacitors – It is a film capacitor – An oil-impregnated paper was used as a dielectric between Aluminum foils. – No polarity – Disadvantage :large size Capacitor Range: 300pF to 4µF Voltage range within 600V Variable Capacitor A capacitor whose capacitance can be varied based on the requirement to a certain range of values is defined as a Variable Capacitor. Gang Capacitor It is a group of capacitors ganged together Consists of two sets of metal plates, one is fixed and other is movable and is connected together on a shaft. Capacitance is varied by rotating the shaft Used in Radio receivers for tuning  Trimmer When it is not necessary to change the value of a capacitor very often, a trimmer can be used. It consists of two plates, mounted on a ceramic base and separated by a sheet of plastic, mica, or some other solid dielectric. The plates are flexible, and can be squashed together more or less by means of a screw.  Numbering of capacitors 1) If the number written on the capacitor is greater than one, the value will be in pF. Otherwise, it will be in μF. Eg: 10 means 10pF, 0.1 means 0.1μF 2)If there are three digits in the number, the third number indicates the number of zeros to be put after first two digits and value will be in pF. Eg: 103 means 10,000 pF or 0.01μF. Que: For the given numbering system, find the capacitance values. 1) 221 2)102 3)101  Capacitance Values Codes in numbers and letters 14 3)If the letter k follows the digits, the value will be in kpF. Eg: 10k means 10kpF 4)If the letter is n or M the value will be that much nano farads or micro farads respectively. Eg: 47n means 47nF and 47M means 47μF. 5) If 2M2 ----- 2.2μF 2k7 ----- 2.7 kpF Que: For the given numbering system, find the capacitance values. 1) 7M2 2)n46 3)10k Ans: 1) 7M2 7.2 μF. 2)n46 0.46 nF. 3)10k 10kpF. Codes in numbers and letters 17  Capacitance Colour Coding Capacitors manufactured in small size are identified by their colour bands provided on their surfaces. To identify the capacitance value following steps are adopted: Hold the capacitor so that colour bands should start from the left-hand side Read the colour bands from left to right. The first band indicates the first digit, the second band indicates the second digit, the third band indicates the multiplier or number of zeroes to be added after the second digit, the fourth band indicates the tolerance in percentage, fifth indicates temperature co-efficient and sixth band indicates working voltage. Thank you