# Solid-state devices and valves

## Introduction

The majority of electronic circuits found in amateur equipment today utilise solid-state devices. These devices are based on 'semiconductor' materials; these can be broadly defined as materials whose resistance lies between that of a conductor and an insulator. The most common materials in this category, silicon and germanium, are the basis of the majority of transistors and diodes. Special high power or low noise devices will also utilise many other materials such as Gallium Arsenide (GaAs), now commonly used in field effect transistors (FETs). New semiconductor materials are being discovered all the time.

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