Structure of capacitor Capacitor conductor metal plate insulator

Structure of capacitor �Capacitor = conductor (metal plate) + insulator (dielectric) + conductor (metal plate)

Type of capacitor �Non-polar �Polarized capacitors

Capacitors Types of capacitors � The dielectric material determines the type of capacitor � Common types of capacitors are: ◦ ◦ Paper Mica Ceramic Plastic film

paper capacitor �A paper capacitor is constructed of two thin tinfoil sheets which are separated by thin waxed & oiled paper or plastic, the sandwich of thin foils and paper or plastic is then rolled into a cylindrical shape which is then enclosed in plastic capsule. The two tin foils of the capacitors are attached to two external leads.

The capacitance of paper capacitor can range in between 0. 001 to 2. 000 Micro farad and the voltage rating can be as high as 2000 Voltage.

Capacitor types Mica capacitors are small with high working voltage. The working voltage is the voltage limit that cannot be exceeded.

Mica capacitors have small capacitance in the range of 50 -500 picofarads, but have relatively high working voltage of up to 500 voltage.

Capacitor types Ceramic disks are small nonpolarized capacitors They have relatively high capacitance due to high er.

Ceramic capacitors have very high capacitance of up to 0. 01 micro farad as compared to their size

Polarized capacitors �Some capacitors are polarised, they can only be connected one way around �Electrolytic capacitors are polarised

�A positive plate made up of Aluminium �An extremely thin insulating film of Aluminium oxide as dielectric which is electrochemically deposited in the surface of positive Aluminium plate itself. �An electrolyte of borax or carbon salt which is absorbed by a absorbent gauze which is placed in contact with the dielectric and connected to an external Aluminium lead acting as negative lead.

�electrolytic capacitors have very large capacitance compared to their size which can range from 1 – 10000 micro-Farads.

Capacitors � Variable capacitors are used in communication equipment, radios, televisions and VCRs � They can be adjusted by consumers by tuning controls � Trimmers are internal adjusted capacitors that a consumer cannot adjust

Capacitors � The capacitance in a varactor is created when a purpose diode is reversed biased � Adjusting the reverse bias alters the capacitance value � A simple radio receiver using varactor http: //www. microst. it

Inductors Values specified in henries (H), millihenries (m. H) and microhenries (μH) A coil of wire that may be wound on a core of air or other non -magnetic material, or on a magnetic core such as iron powder or ferrite. Two coils magnetically coupled form a transformer. LSU 06/04/2007 Electronics 2 17

Inductor types Molded inductor & air-wound inductor Ferrite core toroidal transformer LSU 06/04/2007 Adjustable air-wound inductor Air wound inductor Electronics 2 Iron powder toroidal inductor 18

Circuit Symbols 19