Fundamentals of Linear Electronics: Integrated & Discrete Circuitry docx

CHAPTER 1 Introduction To Diodes Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com OBJECTIVES Describe and Analyze: • Function of Diodes • Some Physics of Diodes • Diode Models Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Introduction <insert figure 1-2 here> •Diodes let current flow one way, but not the other •Conventional current flows from anode to cathode •Electrons flow from cathode to anode Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Diodes are Important • The humble silicon diode is the simplest of all the semiconductor devices. It is also one of the most important. Without diodes, you could not build electronic equipment • Applications for diodes range from power supplies to cell phones and everything in between. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Diodes are Important • It’s important to understand what a diode is and what makes it work. • Diodes use a PN junction. Later, we will see how PN junctions play a key role in transistors. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Bias: Forward & Reverse • A forward-biased diode conducts. • A diode is forward-biased when the voltage on the anode is positive with respect to the cathode. • A reverse-biased diode does not conduct. • A diode is reverse-biased when the voltage on the anode is negative with respect to the cathode. • A diode acts like a voltage-controlled switch. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Valence Electrons • The outer band of electrons in an atom is called the valence band. • Atoms in a conductor (e.g. copper) have valence electrons that can move freely through the material. • The valence electrons of insulators are bound to the atoms and can not move freely. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Covalent Bonds • A covalent bond is formed when atoms can share valence electrons with adjacent atoms. The result is crystalline material such as silicon. • Covalent bonds are very strong. They are what make diamonds hard. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Doping Adding different atoms to a crystal is called doping. • Donor atoms (e.g. arsenic) add movable electrons to the crystal’s valence band. • Acceptor atoms (e.g. gallium) add movable “holes” : open spaces in the valence band to accept electrons. Holes act like positive charge carriers. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Semiconductors: N & P • Doped silicon becomes a semiconductor. • Current can flow through a semiconductor, but not as easily as through metal conductors. • N-Material is silicon that has been been doped with donor atoms. • P-Material is silicon that has been been doped with acceptor atoms. • When a single crystal has N-material on one side and P-material on the other side, things get interesting. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com [...]... important when the applied forward-bias is a low voltage Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Choosing a Model • The ideal model shows the key feature of a diode: one-way conduction of current • For most purposes, the practical model is sufficient • The detailed model may be needed when low voltages and small currents need to be analyzed Simpo PDF Merge and Split... - http://www.simpopdf.com OBJECTIVES Describe and Analyze: • Rectifier Circuits • Voltage Multiplier • Clippers & Clampers • Switching Circuits • Diode Data Sheet Specs • Troubleshooting Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Intro to Rectifiers • The job of a rectifier circuit is to produce a DC output from an AC input • Rectifiers are in power supplies where they... “raw” DC to usable DC Filtered DC still has a small AC ripple on top of the DC Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Ripple Full-wave ripple frequency is twice AC frequency Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Power Supply System Regulator removes most ripple & keeps DC level fixed Simpo PDF Merge and Split Unregistered Version... make semiconductors • Germanium was used originally back in the 1950s, and is used today in high frequency applications • Germanium has a 0.3 Volt drop (approximately) across a PN junction • Other kinds of semiconductor materials can have PN drops up to 1.5 Volts or even up to 3 Volts Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Ideal Diode Model A perfect diode would behave... a diode Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Reverse-Biased PN Junction The electrons and holes are drawn away from the junction, leaving a depletion region devoid of charge carriers No current can flow across the junction Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Forward-Biased PN Junction • Electron are forced to move across the... high-resistance load • Output voltage usually drops quickly as load current increases Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Clippers Clippers are used to remove portions of an AC signal Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Clampers Clampers are used to add a DC level to an AC signal Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com . Function of Diodes • Some Physics of Diodes • Diode Models Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Introduction <insert figure 1-2 here> . http://www.simpopdf.com Diodes are Important • The humble silicon diode is the simplest of all the semiconductor devices. It is also one of the most important. Without diodes, you could not build electronic. band of electrons in an atom is called the valence band. • Atoms in a conductor (e.g. copper) have valence electrons that can move freely through the material. • The valence electrons of insulators