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3.7: Audio Amplifiers
By Cotter W. Sayre
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From Complete Wireless Design
3.7 Audio Amplifiers3.7.1 IntroductionMany nonpower audio amplifier stages need not be matched to their source nor to their load. Since matching is used to maximize power transfer between stages and to reduce standing waves, audio amplifiers are much more concerned with reducing distortions and isolating each stage from the effects of the next. However, matching with low-frequency transformers is quite common with discrete audio power stages in order to obtain high efficiencies, while RC matching is also employed in audio voltage amplifiers. An acceptable single-stage audio voltage amplifier can be designed by using the low frequency bias design formulas as presented in Sec. 3.3, Amplifier Biasing. Operational amplifiers are far more common for voice-frequency amplification for both low-level voltage signals and high-level power signals. They can be acquired from many manufacturers, and are obtainable in an optimized single-voltage supply package for ease of biasing. 3.7.2 Design of an IC audio amplifierThe National LM386 is a low-voltage audio amplifier that is perfect for low-frequency amplification. In voiceband radios this IC can amplify the audio signal all the way from the detector stage to the 8-ohm speaker or headphones. The National device has very low quiescent current drain (4 mA), accepts a wide range of V cc (4 to 12 V), has adjustable voltage gain (20 to 200), decent distortion levels [<10 percent total harmonic distortion (THD)], and has an output driving power of 700 mW with a 9-V supply into 8 ohms. To design an audio...
Copyright The McGraw-Hill Companies, Inc. 2001 under license agreement with Books24x7
Products & Services
Audio amplifiers and audio preamplifiers are units that amplify a sound signal, which is then sent to a speaker or another amplifier.
Learn more about Audio Amplifiers and Preamplifiers
Audio amplifiers are used in circuits and systems to process audio signals.
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Learn more about Audio Amplifier Chips
Power operational amplifiers (POA) are used to increase the power of low-level signals in applications that drive low impedances or reactive loads. They dissipate excess energy as heat, deliver extensive current, and can sustain relatively high supply voltages.
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Learn more about Power Operational Amplifiers
Logarithmic amplifier chips produce an output voltage that is directly proportional to the logarithm of the input voltage.
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Power amplifiers deliver a specific amount of AC power to a load. They are used in audio frequency and radio frequency applications.
Learn more about Power Amplifiers
Product Announcements
Topics of Interest
3.8 VGA Amplifiers
3.8.1 Introduction
Variable gain amplifiers (VGAs) can be designed in one of two ways: either by varying the active device s bias voltage to its base, which controls its...
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3.9 Coupling/Decoupling of Amplifiers
3.9.1 Introduction
Amplifier coupling. To prevent DC biasing of consecutive amplifier stages from adversely affecting other stages, a method of coupling...
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Overview
An amplifier is an active device that has the ability to amplify voltage, current, or both, at zero frequency (a DC amplifier), low frequencies (an audio amplifier), or high frequencies (an...
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Walt Jung Walt Kester
Section 6-1: Audio Amplifiers
Walt Jung
Audio Preamplifiers
Audio signal preamplifiers (preamps) represent the low-level end of the dynamic range of practical audio...
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3.1 Small-Signal Amplifiers
3.1.1 Introduction
Small-signal amplifiers are needed to increase the tiny signal levels found at the input of a receiver into usable levels for the receiver s...
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