The maximum output current is IP=VP/RL=62,5mA. If the transistor beta is B=150 then the maximum base current is about 400µA. This is quite much for an amplifier input so a preceding stage is very useful. IC designers normally would even build a 3 or 4 stage amplifier (and e.g. a 20 transistor bias circuit), but our PA should be as simple as possible. For maximum power gain in a direct coupled (best for low component count) amplifier the common emitter configuration is best suited, and a CB or CC stage is much worse. At low voltages a CC also has the disadvantage that the output voltage smaller than the input voltage by VBE. If you want to drive a CE stage from a CC stage you need an input voltage of 2·VBE»1,4V, which is nearly impossible form a single cell supply. Two CE stages are much easier to connect, but this makes feedback more difficult because the total amplifier will be noninverting. A solution will be a differential pair which has nearly the same characteristics like a single CE stage but features an inverting and a noninerting input. A further advantage is that the inherent temparature compensation makes the biasing more stable.
more explanation, visit: http://www.weberconnect.de/nfpa2.htm
About Audio Amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.
While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at wikipedia.org
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.
The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.
While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at wikipedia.org
This is a video tutorial about how to a very simple audio amplifier based on the LM386 amplifier chip. It can be built for less than $20 (or might be less than $8 in some countries) and used to amplify any low level audio signal including a guitar, bass or mp3 player.
Watch the video:
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