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Hey everyone, I'm Ben for NBitWonder
and i just finished up building
this
prototype class-D audio amplifier
which you can see here.
Now, for the unfamiliar, a class-D audio amplifier
doesn't take a normal linear approach
to amplifying the signal.
In a typical audio amplifier
you would have the output transistors act like big variable resistors and
they send a nice clean signal to the speaker but what happens is they get
very hot in operation so it's very inefficient.
A class-D amplifier, on the other hand is a switching amplifier.
So what happens is the circuitry you see here --
we'll get a little closer
uh... generates
a PWM waveform from the input
and uses that to switch that output transistors either fully on
or fully off
and in doing so
greatly reduces power dissipation
so they don't get hot at all.
Here's one I breadboarded just now
we have a uh...
bipolar plus and minus roughly thirteen volt power supply.
It's not regulated but it's output a pretty clean voltage according to
my voltmeter and previous tests with an oscilloscope.
We have the circuit here and there's some other stuff
on the right-hand side of the breadboard that's not hooked up
but we have a, uh
a preamplifier
that basically just integrates the error
that results from the output stage.
Then, the next chip down the line
is the comparator which generates the square wave.
After that, we have mosfet driver which generates the different voltages to drive
the transistors,
then we have two output devices and a simple filter made up of an inductor and
a capacitor,
and then, we hook up
to the speaker.
So this is a very rough prototype -- like i said i just finished building it -- but we
can play a little bit of a Star Wars theme and can hear what it sounds like.
I'll go ahead and hit play.
It started playing
You can hear the audio
it's okay quality,
it's not the best
It's kind of like listening to a record, I think
But good for a first test. We'll let this play for a little bit and then we'll kill the video.