Basic Concepts Instructor: Chia-Ming Tsai Electronics Engineering National Chiao Tung University Hsinchu, Taiwan, R.O.C.

Contents Introduction Systems of Units Current and Voltage Power and Energy Circuit Elements Example

Introduction An electric circuit is an interconnection of electrical elements. Basic circuit elements include passive components (resistors, capacitors and inductors) and active components (power sources). Each electronic device can be represented by its equivalent circuit model.

Systems of Units (SI) The six basic SI units. QuantityBasic UnitSymbol Lengthmeterm Masskilogramkg Timeseconds Electric currentampereA Thermodynamic temperaturekelvinK Luminous intensitycandelacd

Systems of Units (SI) The SI prefixes. MultiplierPrefixSymbol teraT 10 9 gigaG 10 6 megaM 10 3 kilok MultiplierPrefixSymbol picop nanon micro  millim

Current and Voltage The relationship between current i, charge q, and time t is The relationship between voltage v, charge q, and energy w is 0 t Direct current (dc) I 0 t Alternating current (ac) i

Power and Energy Power p is the product of current i and voltage v. Conservation of energy must be obeyed in any circuit. +_+_ v i a. Absorbing power b. Supplying power +_+_ v i

Circuit Elements Divided into passive elements and active elements Passive elements include resistors, capacitors, and inductors. Active elements include generators (current and voltage sources), batteries, and operational amplifiers (opamps). R C L

Current and Voltage Sources +_+_ V +_+_ vi +_+_ v(t) DC Time-varying Dependent sources a. voltage-controlled b. current-controlled Independent sources i(t) VCVS CCVS VCCS CCCS Voltage sources Current sources Useful in modeling devices & circuits!

Example i q V0V0 Q: At electrons/second, determine V 0 to achieve 4W electron beam. Sol: