2_diode_slide_achar

2_diode_slide_achar - 2 March 2009 R Achar ELEC 2507...

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Unformatted text preview: 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 1 ELEC 2507 Analog Electronics – 1 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 2 ELEC 2507 Diodes 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 3 Diodes • Most fundamental Analog Device • Two terminal device • Acts like a switch (Allows current in one direction and blocks in the other direction) • Symbol: • Applications: Rectifiers, Voltage Regulators, Filters, Logic Switches…… ANODE D1 DIODE CATHODE 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 4 Diodes Diodes are made from a large variety of materials including silicon, germanium, gallium arsenide, silicon carbide … ANODE D1 DIODE CATHODE 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 5 Semiconductor Physics Materials can be classified into three categories based on their electrical properties: • Conductors – offer very low resistance for current flow (e.g. aluminum, copper, iron). • Insulators – offer very high resistance for current flow (e.g. Fibreglass, wood, plastics, cotton). • Semiconductors – offer medium resistance for current flow (e.g. silicon, germanium). Their conductivity (and thus resistivity) can be varied significantly based on external parameters such as temperature, impurities, etc . This makes them highly attractive for deployment in electronic devices. 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 6 Charge carrier types in semiconductors Two types: • Free electrons : Electrons that are not confined to their atoms in chemical bonds are able to move in the lattice. These electrons act as negative charge carriers. • Free holes : A hole is defined as a ’lack’ of an electron, which acts as a positive charge with respect to the sea of electrons surrounding it; since free electrons move in the lattice, the holes (i.e., the positions where electrons lack) also move. Therefore holes can be viewed as positive charge carriers. 2 March 2009; R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University R. Achar, ELEC 2507, Carleton University 7 Types of charge carriers & currents in semiconductors Charge Carriers: •Electrons (-ve charge) •Holes (+ve charge barb4right...
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2_diode_slide_achar - 2 March 2009 R Achar ELEC 2507...

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