Malvino EP 01 introduction

MALVINO Electronic PRINCIPLES SIXTH EDITION Introduction Chapter Three kinds of formulas The definition: Invented for a new concept Q C= V The law: {does not require verification} Summarizes a relationship that exists in nature f=K The derivation: {defines what capacitance is} Q1Q2 d {verified by experiment} Obtained by manipulating other formulas using mathematics Q = CV An ideal voltage source maintains a constant output voltage, regardless of the value of RL 10 V RL The ideal model can be called the first approximation VR = 10 Volts L A real voltage source has a series resistance RS 10 V RL VR < 10 Volts L This model is called the the second approximation When RL is equal to or greater than 100 times RS, a real voltage source is stiff and the first approximation can be used An ideal current source maintains a constant output current, regardless of the value of RL 1A RL The ideal model can be called the first approximation IR = Ampere L A real current source has a shunt resistance 1A RS RL IR < Ampere L This model is called the the second approximation When RS is equal to or greater than 100 times RL, a real current source is stiff and the first approximation can be used Thevenin’s theorem can be used to replace any linear circuit with an equivalent voltage source called VTH and an equivalent resistance called RTH k 72 V k k RR LV THTH Remove the load R open Remove the measure source terminals Calculate or Calculate measure Vor TH across the TH When working with actual circuits, please remember this guideline: The input impedance of a voltmeter should be at least 100 times greater than the Thevenin resistance to avoid loading error DMMs are usually not a problem since they typically have an impedance of 10 M k The original circuit The Thevenin equivalent circuit 72 V k k RL k (RTH) 24 V (VTH) RL Norton’s theorem can be used to replace any linear circuit with an equivalent current source called IN and an equivalent resistance called RN k 72 V k k RL IR NN R N is the TH I Short thesame load as to R find N k The original circuit The Norton equivalent circuit 72 V mA (IN) k k RL k (RN) RL k (RTH) A Thevenin equivalent circuit RN = RTH The Norton dual RL 24 V (VTH) mA (IN) IN = VTH RTH k (RN) RL Troubleshooting • A solder bridge between two lines effectively shorts them together • A cold solder joint is effectively an open circuit • An intermittent trouble is one that appears and disappears (could be a cold solder joint or a loose connection) An open device • The current through it is zero • The voltage across it is unknown • V = zero x infinity {indeterminate} A shorted device • The voltage across it is zero • The current through it is unknown • I = 0/0 {indeterminate} A troubleshooting example: Do the two 10 resistors form a stiff voltage divider? 10  12 V 100 k 10  Why? 100 k A troubleshooting example: What are the expected voltages in this circuit? 10  12 V 100 k 10  100 k A troubleshooting example: What are some causes for this voltage being too high? 10  12 V 100 k 10  100 k V A troubleshooting example: What are some causes for this voltage being too low? 10  12 V 100 k 10  100 k V .. .Introduction Chapter Three kinds of formulas The definition: Invented for a new concept Q C= V The law: {does not require verification} Summarizes... current source is stiff and the first approximation can be used Thevenin’s theorem can be used to replace any linear circuit with an equivalent voltage source called VTH and an equivalent resistance... Thevenin equivalent circuit 72 V k k RL k (RTH) 24 V (VTH) RL Norton’s theorem can be used to replace any linear circuit with an equivalent current source called IN and an equivalent resistance