Download Electrical System-Introduction to Microelectronic Circuits-Lecture 02 Slides-Electrical Engineering and more Slides Microelectronic Circuits in PDF only on Docsity! 1 Lecture 2, Slide 1EECS40, Fall 2003 Prof. King Announcements • Lectures will be in 4 LeConte – beginning Friday 8/29 • Additional discussion TA – Dennis Chang (Sections 101, 105) – Office hours: Mo 2-3 PM; Th 5-6 PM • Lab sections begin Tuesday 9/2 – Read Experiment #1 online – Download Pre-Lab #1 and complete it before going to the lab (140 Cory) • Discussion sections begin Tuesday 9/2 Lecture 2, Slide 2EECS40, Fall 2003 Prof. King Lecture #2 OUTLINE • Introduction to circuit analysis • Electrical quantities – Charge – Current – Voltage – Power • The ideal basic circuit element • Sign conventions Reading Chapter 1 2 Lecture 2, Slide 3EECS40, Fall 2003 Prof. King Electrical System Design Process 1. Identify system performance requirements design specifications 2. Conceive of approach design concept 3. Develop an electric circuit model (mathematical model that approximates the behavior of an actual electrical system) … using ideal circuit components (mathematical models of actual electrical components) 4. Build and test a physical prototype Lecture 2, Slide 4EECS40, Fall 2003 Prof. King Circuit Analysis • Circuit analysis is used to predict the behavior of the electric circuit, and plays a key role in the design process. – Comparison between desired behavior (design specifications) and predicted behavior (from circuit analysis) leads to refinements in design • In order to analyze an electric circuit, we need to know the behavior of each ideal circuit element (in terms of its voltage and current) and the constraints imposed by interconnecting the various elements. 5 Lecture 2, Slide 9EECS40, Fall 2003 Prof. King 2 cm 10 cm 1 cm C2 C1 X Example 1: Suppose we force a current of 1 A to flow from C1 to C2: • Electron flow is in -x direction: Current Density sec 1025.6 /106.1 sec/1 18 19 electrons electronC C ×−= ×− − Semiconductor with 1018 “free electrons” per cm3Wire attached to end Definition: rate of positive charge flow per unit area Symbol: J Units: A / cm2 Lecture 2, Slide 10EECS40, Fall 2003 Prof. King Example 2: Typical dimensions of integrated circuit components are in the range of 1 µm. What is the current density in a wire with 1 µm² area carrying 5 mA? The current density in the semiconductor is Current Density Example (cont’d) 6 Lecture 2, Slide 11EECS40, Fall 2003 Prof. King Electric Potential (Voltage) • Definition: energy per unit charge • Symbol: v • Units: Volts (V) v = dw/dq where w = energy (in Joules), q = charge (in Coulombs) Note: Potential is always referenced to some point. Subscript convention: vab means the potential at a minus the potential at b. a b vab ≡ va - vb Lecture 2, Slide 12EECS40, Fall 2003 Prof. King Electric Power • Definition: transfer of energy per unit time • Symbol: p • Units: Joules per second ≡ Watts (W) p = dw/dt = (dw/dq)(dq/dt) = vi • Concept: As a positive charge q moves through a drop in voltage v, it loses energy energy change = qv rate is proportional to # charges/sec 7 Lecture 2, Slide 13EECS40, Fall 2003 Prof. King The Ideal Basic Circuit Element Attributes: • Two terminals (points of connection) • Mathematically described in terms of current and/or voltage • Cannot be subdivided into other elements + v _ i • Polarity reference for voltage can be indicated by plus and minus signs • Reference direction for the current is indicated by an arrow Lecture 2, Slide 14EECS40, Fall 2003 Prof. King - v + A problem like “Find the current” or “Find the voltage” is always accompanied by a definition of the direction: In this case, if the current turns out to be 1 mA flowing to the left, we would say i = -1 mA. In order to perform circuit analysis to determine the voltages and currents in an electric circuit, you need to specify reference directions. There is no need to guess the reference direction so that the answers come out positive, however. A Note about Reference Directions i
