2.1 Introduction

2.2 Load-Line Analysis

2.3 Diode Approximations

2.4 Series Diode Configurations with DC Inputs

2.5 Parallel and Series-Parallel Configurations

2.6 AND/OR Gates

2.7 Sinusoidal Inputs; Half-Wave Rectification

2.8 Full-Wave Rectification

2.9 Clippers

2.10 Clampers

2.11 Zener Diodes

2.12 Voltage-Multiplier Circuits

2.13 PSpice Windows

Learning Outcomes

After completing this chapter you will be able to

- Determine the operating characteristics of a device using load-line analysis

- Explain the operation of DC circuits with diodes connected in various configurations

- Explain the operation of half-wave and full-wave rectifier circuits

- Determine the output waveform for a variety of diode clipper and clamper circuits

- Explain how Zener diodes can be used to maintain constant voltage across a load

- Explain the operation of a variety of voltage multiplier circuits

Introduction

In the last chapter you saw the construction of semiconductor diodes along with their characteristics and ways to model them. In this chapter you will see how diodes are used in various configurations with models suited to particular applications. You should gain a clear understanding of the basic behaviour patterns of diodes in dc and ac networks. You will find that the new concepts of this chapter apply beyond simple diode circuits, because diodes are often used to model transistors in a variety of multi-terminal networks-for example in the r_e analysis of Section 7.5.

This chapter intends that you understand the basic principles of electronic devices so you can analyze how they operate in an endless variety of circuit configurations. Although the analysis begins with the actual characteristics of diodes, you will quickly see the advantages of using models that depend on approximating the characteristics. These approximations are chosen to reduce the complexity of the mathematical analysis. For instance, some characteristics of semiconductor devices are represented by equations involving exponential expressions. In the range of operation of a device, you will find that a linear approximation may be quite satisfactory.

How do you determine if a particular approximation is satisfactory? Consider, for example, a simple practical circuit. You want to know the current when 10 V is applied across a 100 resistor. With a 5% resistor and a voltage tolerance of 1%, the current can range from 94 mA to 106 mA. If a precise analysis gave a result of 96.3 mA, then the approximation of 100 mA is quite satisfactory-it is "as accurate" as needed.