Chapter 3. Capacitors and Inductors

3.0 Introduction

When it comes to digital electronics, capacitors are almost a matter of insurance, providing short-term stores of charge that improve the reliability of circuits. As such their use is often simply a matter of following the recommendations in the IC’s datasheet without the need to do any math.

However, when it comes to analog electronics the use of capacitors becomes much more varied. Their ability to store small amounts of charge for a short period of time can be used to set the frequency of oscillators (see Recipe 16.5). They can be used to smooth the ripples for a power supply (see Recipe 7.2) or to couple two audio circuits without transferring the DC part of the signal (see Recipe 17.9).

In fact, capacitors will be used throughout this book in all sorts of ways, so it’s important to understand how they work, how to select the right capacitor, and how to use it.

Inductors are not as common as capacitors, but they are widely used in certain roles, particularly in power supplies (see Chapter 7).

3.1 Store Energy Temporarily in Your Circuits


You need an electronic component that can store energy for short periods of time, perhaps to create pulses, or to insulate other components from voltage spikes.


Use a capacitor.

In construction, capacitors are just two conductive surfaces separated by an insulating layer (Figure 3-1).

Figure 3-1. A Capacitor

In fact, the insulating layer between the conductive surfaces ...

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