[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:03.21,Default,,0000,0000,0000,,>> Okay. Now, let's talk\Nabout the amplifier block.
Dialogue: 0,0:00:03.21,0:00:07.44,Default,,0000,0000,0000,,The amplifier block right here is\Nused to make the signal bigger
Dialogue: 0,0:00:07.44,0:00:09.21,Default,,0000,0000,0000,,because it wasn't big enough when it
Dialogue: 0,0:00:09.21,0:00:11.50,Default,,0000,0000,0000,,came through the antenna.\NThis is the antenna.
Dialogue: 0,0:00:11.50,0:00:13.30,Default,,0000,0000,0000,,This impedance is matched to the line,
Dialogue: 0,0:00:13.30,0:00:17.31,Default,,0000,0000,0000,,and the amplifier, when you purchase it\Nis already impedance matched as well.
Dialogue: 0,0:00:17.31,0:00:19.02,Default,,0000,0000,0000,,But the amplifier right here,
Dialogue: 0,0:00:19.02,0:00:23.18,Default,,0000,0000,0000,,you'd expect that only the two terminal\Ndevice like the signal comes in,
Dialogue: 0,0:00:23.18,0:00:26.38,Default,,0000,0000,0000,,goes to the amplifier and comes\Nout bigger than it was before.
Dialogue: 0,0:00:26.38,0:00:29.84,Default,,0000,0000,0000,,But Amplifiers at high frequency\Nneeds to be well-grounded.
Dialogue: 0,0:00:29.84,0:00:32.79,Default,,0000,0000,0000,,These two little wings right\Nhere are used for grounding.
Dialogue: 0,0:00:32.79,0:00:36.60,Default,,0000,0000,0000,,You see that there are a lot of\Nholes where pieces of wire had been
Dialogue: 0,0:00:36.60,0:00:40.54,Default,,0000,0000,0000,,soldered down to create a really good\Nground for this amplifier.
Dialogue: 0,0:00:40.54,0:00:42.88,Default,,0000,0000,0000,,If you don't ground\Nthe amplifier really well,
Dialogue: 0,0:00:42.88,0:00:46.34,Default,,0000,0000,0000,,could it oscillates instead of\Namplifies, of course that's no good.
Dialogue: 0,0:00:46.34,0:00:49.01,Default,,0000,0000,0000,,Now, the reason that happens like
Dialogue: 0,0:00:49.01,0:00:53.68,Default,,0000,0000,0000,,one little wire connected down\Nto the copper on the bottom.
Dialogue: 0,0:00:53.68,0:00:56.30,Default,,0000,0000,0000,,That's not enough for a\Nground at high frequency.
Dialogue: 0,0:00:56.30,0:00:57.83,Default,,0000,0000,0000,,That's because when I do that,
Dialogue: 0,0:00:57.83,0:00:59.60,Default,,0000,0000,0000,,it acts like an inductor,
Dialogue: 0,0:00:59.60,0:01:01.62,Default,,0000,0000,0000,,instead of acting like a ground.
Dialogue: 0,0:01:01.62,0:01:04.68,Default,,0000,0000,0000,,So we have to put lots of holes
Dialogue: 0,0:01:04.68,0:01:08.06,Default,,0000,0000,0000,,and ground lines down in order\Nto fully ground this amplifier.
Dialogue: 0,0:01:08.06,0:01:09.94,Default,,0000,0000,0000,,Otherwise it acts like\Nan inductor to ground
Dialogue: 0,0:01:09.94,0:01:13.46,Default,,0000,0000,0000,,instead of a short circuit to ground.
Dialogue: 0,0:01:13.46,0:01:16.43,Default,,0000,0000,0000,,Now, an amplifier needs\Nto have external powers.
Dialogue: 0,0:01:16.43,0:01:18.62,Default,,0000,0000,0000,,So right here is where the external power
Dialogue: 0,0:01:18.62,0:01:21.39,Default,,0000,0000,0000,,is going to be plugged in\Nfor this particular device.
Dialogue: 0,0:01:21.39,0:01:24.47,Default,,0000,0000,0000,,Now, the external power is going to be DC,
Dialogue: 0,0:01:24.47,0:01:28.54,Default,,0000,0000,0000,,whereas this is obviously an AC sinusoidal\Nsignal going through this line.
Dialogue: 0,0:01:28.54,0:01:30.86,Default,,0000,0000,0000,,We need to be able to separate them.
Dialogue: 0,0:01:30.86,0:01:37.19,Default,,0000,0000,0000,,So we don't want the DC getting out\Nhere to go along with our AC signal.
Dialogue: 0,0:01:37.19,0:01:38.93,Default,,0000,0000,0000,,We put a capacitor right here,
Dialogue: 0,0:01:38.93,0:01:42.74,Default,,0000,0000,0000,,and another capacitor right\Nthere to block the DC signal
Dialogue: 0,0:01:42.74,0:01:47.09,Default,,0000,0000,0000,,so that it won't be mixed up with our\NAC signal that we want along this line.
Dialogue: 0,0:01:47.09,0:01:50.14,Default,,0000,0000,0000,,We also put an inductor right\Nthere. You see that inductor?
Dialogue: 0,0:01:50.14,0:01:53.98,Default,,0000,0000,0000,,That's used to keep the AC\Nsignal out of our DC circuit.
Dialogue: 0,0:01:53.98,0:01:55.55,Default,,0000,0000,0000,,So here's the inductor block,
Dialogue: 0,0:01:55.55,0:01:57.14,Default,,0000,0000,0000,,here is the capacity blocks.
Dialogue: 0,0:01:57.14,0:01:59.53,Default,,0000,0000,0000,,This is a DC block,
Dialogue: 0,0:01:59.53,0:02:00.90,Default,,0000,0000,0000,,that's an AC block.
Dialogue: 0,0:02:00.90,0:02:03.26,Default,,0000,0000,0000,,This piece right here is a little resistor,
Dialogue: 0,0:02:03.26,0:02:04.62,Default,,0000,0000,0000,,a little surface mount resistor.
Dialogue: 0,0:02:04.62,0:02:06.36,Default,,0000,0000,0000,,These are called surface mount parts.
Dialogue: 0,0:02:06.36,0:02:11.24,Default,,0000,0000,0000,,That's a little resistor that's used\Nto help to create this amplification.
Dialogue: 0,0:02:11.24,0:02:13.30,Default,,0000,0000,0000,,So there's a amplifier block.
Dialogue: 0,0:02:13.30,0:02:15.12,Default,,0000,0000,0000,,The amplifier comes pre-match to
Dialogue: 0,0:02:15.12,0:02:18.40,Default,,0000,0000,0000,,this 50 ohm line so I don't have\Nto do any impedance matching.
Dialogue: 0,0:02:18.40,0:02:20.66,Default,,0000,0000,0000,,I just have to be sure that the AC and
Dialogue: 0,0:02:20.66,0:02:23.92,Default,,0000,0000,0000,,DC are kept separate for\Nthis amplifier block.