Fundamentals of Electronic Circuit Design

[Pages:59]Fundamentals of Electronic Circuit Design

By Hongshen Ma

Preface ? Why Study Electronics?

Purely mechanical problems are often only a subset of larger multi-domain problems faced by the designer. Particularly, the solutions of many of today's interesting problems require expertise in both mechanical engineering and electrical engineering. DVD players, digital projectors, modern cars, machine tools, and digital cameras are just a few examples of the results of such combined innovation. In these hybrid systems, design trade-offs often span the knowledge space of both mechanical and electrical engineering. For example, in a car engine, is it more cost-effective to design a precise mechanical timing mechanism to trigger the firing of each cylinder, or is it better to use electronic sensors to measure the positions of each piston and then use a microprocessor to trigger the firing? For every problem, designers with combined expertise in mechanical and electrical engineering will be able to devise more ideas of possible solutions and be able to better evaluate the feasibility of each idea.

A basic understanding of electronic circuits is important even if the designer does not intend to become a proficient electrical engineer. In many real-life engineering projects, it is often necessary to communicate, and also negotiate, specifications between engineering teams having different areas of expertise. Therefore, a basic understanding of electronic circuits will allow the mechanical engineer to evaluate whether or not a given electrical specification is reasonable and feasible.

The following text is designed to provide an efficient introduction to electronic circuit design. The text is divided into two parts. Part I is a barebones introduction to basic electronic theory while Part II is designed to be a practical manual for designing and building working electronic circuits.

? 2005 Hongshen Ma

2

Part I

Fundamentals Principles

By Hongshen Ma

? 2005 Hongshen Ma

3

Important note:

This document is a rough draft of the proposed textbook. Many of the sections and figures need to be revised and/or are missing. Please check future releases for more complete versions of this text.

? 2005 Hongshen Ma

4

Fundamentals of Electronic Circuit Design

Outline

Part I ? Fundamental Principles

1 The Basics 1.1 Voltage and Current 1.2 Resistance and Power 1.3 Sources of Electrical Energy 1.4 Ground 1.5 Electrical Signals 1.6 Electronic Circuits as Linear Systems

2 Fundamental Components: Resistors, capacitors, and Inductors 2.1 Resistor 2.2 Capacitors 2.3 Inductors

3 Impedance and s-Domain Circuits 3.1 The Notion of Impedance 3.2 The Impedance of a Capacitor 3.3 Simple RC filters 3.4 The Impedance of an Inductor 3.5 Simple RL Filters 3.6 s-Domain Analysis 3.7 s-Domain Analysis Example 3.8 Simplification Techniques for Determining the Transfer Function 3.8.1 Superposition 3.8.2 Dominant Impedance Approximation 3.8.3 Redrawing Circuits in Different Frequency Ranges

4 Source and Load 4.1 Practical Voltage and Current Sources 4.2 Thevenin and Norton Equivalent Circuits 4.3 Source and Load Model of Electronic Circuits

5 Critical Terminology 5.1 Buffer 5.2 Bias 5.3 Couple

6 Diodes 6.1 Diode Basics 6.2 Diode circuits

? 2005 Hongshen Ma

5

6.2.1 Peak Detector 6.2.2 LED Circuit 6.2.3 Voltage Reference

7 Transistors 7.1 Bipolar Junction Transistors 7.2 Field-effect Transistors

8 Operational Amplifiers 8.1 Op amp Basics 8.2 Op amp circuits 8.2.1 non-inverting amplifier 8.2.2 inverting amplifier 8.2.3 signal offset

9 Filters 9.1 The Decibel Scale 9.2 Single-pole Passive Filters 9.3 Metrics for Filter Design 9.4 Two-pole Passive Filters 9.5 Active Filters 9.5.1 First order low pass 9.5.2 First order high pass 9.5.3 Second order low pass 9.5.4 Second order high pass 9.5.5 Bandpass

10 Feedback 10.1 Feedback basics 10.2 Feedback analysis ? Block diagrams 10.3 Non-inverting amplifier 10.4 Inverting amplifier 10.5 Precision peak detector 10.6 Opamp frequency response 10.7 Stability analysis

? 2005 Hongshen Ma

6

1 The Basics

1.1 Voltage and Current

Voltage is the difference in electrical potential between two points in space. It is a measure of the amount of energy gained or lost by moving a unit of positive charge from one point to another, as shown in Figure 1.1. Voltage is measured in units of Joules per Coulomb, known as a Volt (V). It is important to remember that voltage is not an absolute quantity; rather, it is always considered as a relative value between two points. In an electronic circuit, the electromagnetic problem of voltages at arbitrary points in space is typically simplified to voltages between nodes of circuit components such as resistors, capacitors, and transistors.

Figure 1.1: Voltage V1 is the electrical potential gained by moving charge Q1 in an electric field.

When multiple components are connected in parallel, the voltage drop is the same across all components. When multiple components are connected in series, the total voltage is the sum of the voltages across each component. These two statements can be generalized as Kirchoff's Voltage Law (KVL), which states that the sum of voltages around any closed loop (e.g. starting at one node, and ending at the same node) is zero, as shown in Figure 1.2.

V1 + V2 + V3 + V4 + V5 + V6 = 0

V3

V1 = V2 = V3 = V4

R3

V2 R2

R4 V4

V5

V1 R1

V2 R2

V3 R3

V4 R4

R5

V1 R1

R6 V6

Figure 1.2: Kirchoff's Voltage Law: The sum of the voltages around any loop is zero.

Electric current is the rate at which electric charge flows through a given area. Current is measured in the unit of Coulombs per second, which is known as an ampere

? 2005 Hongshen Ma

7

(A). In an electronic circuit, the electromagnetic problem of currents is typically simplified as a current flowing through particular circuit components.

+

+

+

+

+

+

+

+

+++

+

++ +

+

+

+

+

+

+

+

+

+

++ +

+ +

+

+

+

I1

+

+

+ +

+ +

+ +

++

+ + +

+

+

+ +

++

+ +

+

+

+

+

+

+ +

+

+

+

Figure 1.3: Current I1 is the rate of flow of electric charge

When multiple components are connected in series, each component must carry the same current. When multiple components are connected in parallel, the total current is the sum of the currents flowing through each individual component. These statements are generalized as Kirchoff's Current Law (KCL), which states that the sum of currents entering and exiting a node must be zero, as shown in Figure 1.4.

I1 + I2 + I3 + I4 = 0

I1

R1

I2

R2

I3

R3

I4

R4

Figure 1.4: Kirchoff's Current Law ? the sum of the currents going into a node is zero.

An intuitive way to understand the behavior of voltage and current in electronic circuits is to use hydrodynamic systems as an analogue. In this system, voltage is represented by gravitational potential or height of the fluid column, and current is represented by the fluid flow rate. Diagrams of these concepts are show in Figure 1.5 through 1.7. As the following sections will explain, electrical components such as resistors, capacitors, inductors, and transistors can all be represented by equivalent mechanical devices that support this analogy.

? 2005 Hongshen Ma

8

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download