3 FSK WLAN amplifier

>> Okay. Now, let's talk
about the amplifier block.

The amplifier block right here is
used to make the signal bigger

because it wasn't big enough when it

came through the antenna.
This is the antenna.

This impedance is matched to the line,

and the amplifier, when you purchase it
is already impedance matched as well.

But the amplifier right here,

you'd expect that only the two terminal
device like the signal comes in,

goes to the amplifier and comes
out bigger than it was before.

But Amplifiers at high frequency
needs to be well-grounded.

These two little wings right
here are used for grounding.

You see that there are a lot of
holes where pieces of wire had been

soldered down to create a really good
ground for this amplifier.

If you don't ground
the amplifier really well,

could it oscillates instead of
amplifies, of course that's no good.

Now, the reason that happens like

one little wire connected down
to the copper on the bottom.

That's not enough for a
ground at high frequency.

That's because when I do that,

it acts like an inductor,

instead of acting like a ground.

So we have to put lots of holes

and ground lines down in order
to fully ground this amplifier.

Otherwise it acts like
an inductor to ground

instead of a short circuit to ground.

Now, an amplifier needs
to have external powers.

So right here is where the external power

is going to be plugged in
for this particular device.

Now, the external power is going to be DC,

whereas this is obviously an AC sinusoidal
signal going through this line.

We need to be able to separate them.

So we don't want the DC getting out
here to go along with our AC signal.

We put a capacitor right here,

and another capacitor right
there to block the DC signal

so that it won't be mixed up with our
AC signal that we want along this line.

We also put an inductor right
there. You see that inductor?

That's used to keep the AC
signal out of our DC circuit.

So here's the inductor block,

here is the capacity blocks.

This is a DC block,

that's an AC block.

This piece right here is a little resistor,

a little surface mount resistor.

These are called surface mount parts.

That's a little resistor that's used
to help to create this amplification.

So there's a amplifier block.

The amplifier comes pre-match to

this 50 ohm line so I don't have
to do any impedance matching.

I just have to be sure that the AC and

DC are kept separate for
this amplifier block.