Hardware Hacking Projects for Geeks

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Introduction

Ceramic

A ceramic capacitor has the simplest design structure, consisting of two

metal plates with a chemical coating between them. A ceramic material

coats and protects the metal plates.

Ceramic capacitors can be used for a variety of applications. They are typi-

cally very stable over a wide temperature range, have a tight tolerance, and

retain their capacitance over a wide frequency range. They are available in

values from a few pico-Farads up to a few micro-Farads.

Ceramic capacitors are non-polarized; they can be placed in a circuit with-

out concern for which terminal is connected to the positive signal. They

also have very low leakage; once charged, they will hold that charge for a

relatively long period of time.

Tantalum

Making this type of capacitor involves placing a tiny pellet of tantalum,

a rare element, on a wire, growing an MnO2 layer, and attaching another

wire. The package is covered in plastic or ceramics. The tantalum element

can store a large amount of charge in a small space.

This type of capacitor exhibits low leakage current, a small size for rela-

tively large capacitance, and good temperature stability. However, it has a

low operating voltage (50 volts maximum depending on the part), and it is

polarized. If the plus side is connected to a negative voltage, the capacitor

will likely be permanently damaged and make a nice pop or bang when it

dies.

Which capacitor for which job?

Electrolytic capacitors are typically used as power supply filters where the

capacitance value is not critical but large capacitance is needed, up to the

Farad range. This type of capacitor’s value can vary 20 percent or more from

the value marked on the package.

Ceramic capacitors are typically used for timing circuits where a tight toler-

ance value is required. These capacitors are generally available only in small

values, typically less than 1 uF.

Tantalum capacitors are typically used for power supply filtering where the

size of the capacitor package needs to be small. These capacitors can have

capacitance values close to electrolytics but are much smaller and can cost

more.

Transistor Types

There are two basic types of tran-

sistors: Bipolar and Metal Oxide

Semiconductor Field Effect Transistor

(MOSFET).

Bipolar: The first types of transistors

developed were called bipolar, refer-

ring to the type of semiconductor

used. Bipolar transistors typically

have three connections: a collector

(an input), an emitter (an output),

and a base (a control). Current in a

bipolar transistor flows from the col-

lector to the emitter and is controlled

by the current flowing into the base.

Unlike MOSFET transistors, bipolar

transistors are not sensitive to static

electricity.

MOSFET: Metal Oxide Semiconductor

Field Effect Transistors were invented

after the bipolar transistor. There

are typically three connections in a

MOSFET: a drain (input), a source

(output), and a gate (control). These

transistors work differently from bipo-

lar transistors in that you can control

the current flow between the drain

and the source by a voltage applied

to the gate. MOSFETs are sensitive

to static electricity and should be

handled carefully to avoid damage.

MOSFETs belong to a family of tran-

sistors that include P-channel and

N-channel FETs and JFETs (Junction

Field Effect Transistors).

How to Identify Capacitor Values

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