Basics of Audio Amplifier
Audio is one of the most common media. Here, It refers to the representation of sound which can be perceived by humans. Audio and Video are the essential component of any electronic media. The electronics can be used to receive audio signals (via microphone), record audio in some storage, transmit audio (through wired or wireless communication channels) and reproduce audio signals (via speakers). The audio can be represented and transmitted as either analog signals or digital signals. In this series, analog audio signals are the concern. The audio signals have a frequency range of 20 Hz to 20,000 Hz.
The loudness of an audio signal is signified by the amplitude of the signal. Like the nature of sound, the audio in the form of electrical signals also fade away with the distance. This was a major problem before the telephony engineers in the initial phase of the development of communication technologies. Typically, on a wired channel, if an electrical signal carrying audio is transmitted from one end and received at another end one mile away, it loses 90 percent of its strength. When the signal travels through a wire, the resistance of the wire causes reduction in its power (P = I2/R). The loss of signal over transmission has been a major issue before the electronic engineers. There are losses whether the signal is transmitted from just the microphone to the recording device, computer or audio generator to a speaker or it is transmitted on wire over a long distance. In order to sort out this problem, engineers devised special electronics – ‘Amplifiers’. The amplifiers increases the strength of the signal so it reaches a longer distance before diminishing. By increasing the amplitude of the input signal, basically the output power of the circuit is increased as high power signals can travel more distance than low power signals. By using amplifiers at different stages, the audio signals can then be safely transmitted over a wired connection.
Another major improvement was the representation of audio in the form of digital signals. By the representation of the audio signals in the form of digital signals, the audio data remains secured. In digital encoding, the audio data becomes independent of the amplitude of the signal and so it is not altered or lost due to noise in the cable.
In this series, analog audio signals will remain the area of concern. The digital encoding of the audio signals will not be discussed. The design and use of different kind of amplifiers will be discussed throughout this series. The following amplifier circuits will be designed in the series –
1) 250 mW Power Amplifier
2) 1W Power Amplifier
3) Bass Boost Amplifier
4) Car Audio Amplifier
5) Head Phone Amplifier
6) Stereo Amplifier
7) MAX4468 Pre-Amplifier
8) LM358 Pre-Amplifier
An Amplifier increases the strength of an audio signal by increasing its amplitude. The rise in amplitude is called Amplification. That is why, it is called Amplifier. An audio amplifier needs to be designed based on its application and required specifications. All the amplifiers listed above are designed for different applications and with different specifications as per the requirement.
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