Power-Introduction to Microelectronic Circuits-Lecture 03 Slides-Electrical Engineering, Slides of Microelectronic Circuits

Download Power-Introduction to Microelectronic Circuits-Lecture 03 Slides-Electrical Engineering and more Slides Microelectronic Circuits in PDF only on Docsity! 1 Lecture 3, Slide 1EECS40, Fall 2003 Prof. King Lecture #3 OUTLINE • Power calculations • Circuit elements – Voltage and current sources – Electrical resistance (Ohm’s law) • Kirchhoff’s laws Reading Chapter 2 Lecture 3, Slide 2EECS40, Fall 2003 Prof. King If an element is absorbing power (i.e. if p > 0), positive charge is flowing from higher potential to lower potential. p = vi if the “passive sign convention” is used: How can a circuit element absorb power? By converting electrical energy into heat (resistors in toasters), light (light bulbs), or acoustic energy (speakers); by storing energy (charging a battery). Review: Power + v _ i _ v + i or 2 Lecture 3, Slide 3EECS40, Fall 2003 Prof. King Find the power absorbed by each element: Power Calculation Example vi (W) 918 - 810 - 12 - 400 - 224 1116 p (W) Conservation of energy total power delivered equals total power absorbed Lecture 3, Slide 4EECS40, Fall 2003 Prof. King Circuit Elements • There are 5 ideal basic circuit elements: – voltage source – current source – resistor – inductor – capacitor • Many practical systems can be modeled with just sources and resistors • The basic analytical techniques for solving circuits with inductors and capacitors are the same as those for resistive circuits active elements, capable of generating electric energy passive elements, incapable of generating electric energy 5 Lecture 3, Slide 9EECS40, Fall 2003 Prof. King Electrical Conductance • Conductance is the reciprocal of resistance. Symbol: G Units: siemens (S) or mhos ( ) Example: Consider an 8 Ω resistor. What is its conductance? Ω Lecture 3, Slide 10EECS40, Fall 2003 Prof. King Short Circuit and Open Circuit Wire (“short circuit”): • R = 0 no voltage difference exists (all points on the wire are at the same potential) • Current can flow, as determined by the circuit Air (“open circuit”): • R = ∞ no current flows • Voltage difference can exist, as determined by the circuit 6 Lecture 3, Slide 11EECS40, Fall 2003 Prof. King Circuit Nodes and Loops • A node is a point where two or more circuit elements are connected. • A loop is formed by tracing a closed path in a circuit through selected basic circuit elements without passing through any intermediate node more than once Example: Lecture 3, Slide 12EECS40, Fall 2003 Prof. King Kirchhoff’s Laws • Kirchhoff’s Current Law (KCL): – The algebraic sum of all the currents at any node in a circuit equals zero. • Kirchhoff’s Voltage Law (KVL): – The algebraic sum of all the voltages around any loop in a circuit equals zero. 7 Lecture 3, Slide 13EECS40, Fall 2003 Prof. King Example: Power Absorbed by a Resistor p = vi = ( iR )i = i2R p = vi = v ( v/R ) = v2/R Note that p > 0 always, for a resistor. Example: a) Calculate the voltage vg and current ia. b) Determine the power dissipated in the 80Ω resistor. Lecture 3, Slide 14EECS40, Fall 2003 Prof. King More Examples • Are these interconnections permissible?