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In the last two labs we were learning and reviewing many of the
fundamentals of electronic circuit analysis. In this lab we'll
try to put these basics together, along with a few new ideas
to have fun building a fairly high-quality audio
amplifier for a compact disc player.
The main goal in making the CD audio amp is to take a
relatively small signal from the CD player ,with relatively high source resistance ,and amplify it sufficiently to drive a speaker, which is usually
described as an load. A good quality amp will be
able to deliver five to ten watts average power to the load,
without distorting the original signal. In other words, the
signal supplied to the speaker (load) should be an exact
replica of the original signal coming from the CD player.
Therefore, the hi-fi will amplify all frequencies
equally over the audio range which is 20Hz to 20kHz.
Any unwanted deviation from the original signal is considered distortion.
To achieve this audio amps usually have two basic stages:
(1) a pre-amp stage which increases the voltage of the
original signal and (2) a current or power amp stage which makes sure
the amp can source enough current so the load does not sag the
voltage at the output.
There are also peripherals
such as tone control circuits, and of course the audio
amp requires a strong enough power supply
to power the circuit.
Next: Design Considerations
Up: Design and Build Your
Previous: Design and Build Your
Neil Goldsman
10/23/1998