Chapter 6

Active Filter Design Techniques

6.1 Introduction

What is a filter? According to Webster, it is “a device that passes electric signals at certain frequencies or frequency ranges while preventing the passage of others”.

Filter circuits are used in a wide variety of applications. In the field of telecommunications, bandpass filters are used in the audio frequency range (20 Hz to 20 kHz) for modems and speech processing. High-frequency bandpass filters (several hundred megahertz) are used for channel selection in telephone central offices. Data acquisition systems usually require antialiasing low-pass filters as well as low-pass noise filters in their preceding signal conditioning stages. System power supplies often use band-rejection filters ...

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