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Similaire à EST 130 Passive components capacitors
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EST 130 Passive components capacitors
- 2. 2 Contents • Introduction. • Capacitor Classifications. • Fixed Capacitors. • Variable Capacitors. • Capacitor Coding. • Super Capacitors. • Applications.
- 3. 3 Capacitors • Passive electronic component. • Capacitance expressed in Farads. • Metal plates separated by dielectric. • Impedance has reactive components. • Frequency dependent reactance. • Can store and release energy. • Blocks dc and passes ac. • Opposes change in voltage. • With or without polarity. 1 2 Xc fC
- 4. 4 Breakdown Voltage • Voltage above which the dielectric will breakdown and start conducting. • Depends on the type of the capacitor. 0 r A C d
- 5. 5 Capacitor Types Capacitors Fixed Capacitors Variable Capacitors Ceramic Disc Ceramic Tubular Paper Polyester Gang Condensor Padder Electrolytic Tantalum Mica Trimmer +
- 7. 7 Electrolytic Capacitors • Polarised, has positive and negative electrodes. • Aluminium foil electrodes with aluminium oxide film covering on one side. • Oxide as dielectric, aluminium plates as electrodes. • Oxide in contact with paper saturated with an electrolyte. • Electrolyte as the second plate.
- 8. 8 Electrolytic Capacitors • Layer of aluminium without oxide for electrical contacts. • 1μF to a few thousand μF, 1V to 500 V. • Size depends on voltage rating. • As filters in power supplies, coupling capacitors.
- 10. 10 Tantalum Capacitors • Electrolytic, tantalum electrodes. • Polarised. • Superior to electrolytic capacitors in temperature and frequency characteristics. • Expensive. • Stable capacitance values. • Used in analog signal systems.
- 12. 12 Mica Capacitors • Mica as dielectric, flat strips of metal foil separated by mica. • Metal plates connected to two electrodes. • Relative costly. • 5 to 10,000 pf, up to 500 V, no polarity. • Excellent frequency characteristics. • Used in resonance circuits and high frequency filters. • Good insulation, in high voltage circuits.
- 14. 14 Ceramic Capacitors • Titanium and barium as dielectric. • Ceramic disc with silver or copper plating on opposite faces. • Leads attached to the plates. • In high frequency applications. • In both ac and dc circuits. • As byepass capacitors. • 3 pF to 2 μF, no polarity.
- 16. 16 Paper Capacitors • Two metal foils separated by strips of paper. • Paper impregnated with wax, plastic or oil (dielectric). • 0.0005 μF to several μF. • No polarity. • 100 Volts to several thousand Volts. • More bulky.
- 18. 18 Variable Capacitors • Capacitors for coarse and fine adjustments. • Used for frequency adjustments. • In radio tuners, tuning to a radio station.
- 19. 19 Gang Capacitors • Group of capacitors ganged together. • Air Gang and PVC Gang. • Rotor-Stator type variable capacitor with two sets of metal plates. • Fixed plates connected together to form stator. • Movable plates connected together on a rotating shaft. • In radio receivers to tune to stations.
- 20. 20 Gang Capacitors Air Gang PVC Gang
- 21. 21 Trimmers • Mica or Ceramic as dielectric. • Capacitance varied by turning adjustment screw. • Normally initial setting undisturbed. • Low values of the order of pF. • Use when frequent adjustment is not required. • Use in TV, broadcast receivers.
- 23. 23 Padders • Higher capacitance values. • Two concentrically mounted tiny aluminium cups. • Air as dielectric. • Gap between two caps varied by turning a screw, capacitance varies. • 5 pF to 600 pF.
- 24. 24 Padders
- 25. 25
- 26. 26 Super Capacitors • High capacitance values. • Uses electrostatic double-layer capacitance and electrochemical pseudocapacitance*. • 10 to 100 times more energy per unit volume than electrolytic capacitors. • Bridges the gap between electrolytic capacitors and rechargeable batteries. • Used in applications requiring many rapid charge/discharge cycles.
- 27. 27
- 29. 29 Indicating Capacitance Values • Alphanumeric and colour coding schemes. • Value written in coded form on small capacitors. • Similar to resistor colour coding scheme. • Five colour bands - value (first two bands), multiplier (third band) and tolerance (fourth band). • Fifth band indicates voltage rating.
- 30. 30 Alphanumeric Coding Code 0.1 10 104 10k Value 0.1μF 10 pF 10 x 104 pF (0.1 μF) 10 kpF (0.01 μF) Code 10n 1M 2M2 4k7 Value 10 nF 1 μF 2.2 μF 4.7 kpF (0.0047 μF)
- 31. 31 Alphanumeric Coding • If the number written is greater than 1, value in pF, else in μF. • For 3 digits, 3rd digit indicates multiplier. • If letter ‘k’ follows digits, value in kpF. • If ‘n’ or ‘M’, value in nF or μF. • ‘k’ or ‘M’ follow a 3 digit number implies 10% and 20% tolerance. • If ‘n’, ‘M’ or ‘k’ between numbers, put decimal point in place, value in nF, μF or kpF respectively.
- 34. 34 5 band system
- 36. 36 Capacitor Colour Coding Identify the above capacitors
- 37. 37 Capacitor Applications • As timing elements in oscillator circuits. • Coupling - to block dc and pass ac signals. • Byepass – to byepass high frequencies. • Surge suppression. • In filter circuits. • In clampers and voltage multipliers. • In differentiating and integrating circuits.
- 38. 38 Thank You