1
00:00:00,012 --> 00:00:08,777
Welcome back. 
So far we have finished Modules 1, 2, and 

2
00:00:08,777 --> 00:00:11,922
3, and we're starting Module 4 on 
Frequency Analysis. 

3
00:00:11,922 --> 00:00:18,780
Previously, I've tried to show you the 
difference between Resistive and Reactive 

4
00:00:18,780 --> 00:00:22,580
Circuits, so you, to motivate you why we 
would want to study both of those 

5
00:00:22,580 --> 00:00:27,049
circuits. 
Last time, I showed this plot. 

6
00:00:27,049 --> 00:00:32,110
I showed the response of the resisted 
circuit to a square wave. 

7
00:00:32,110 --> 00:00:37,940
Now, this shows a physical circuit. 
This is a screenshot from an oscilloscope 

8
00:00:38,980 --> 00:00:45,680
and this is a resistive network. 
The voltage source is a sign wave and the 

9
00:00:45,680 --> 00:00:50,360
response across any of the resistors is 
also a sign wave. 

10
00:00:50,360 --> 00:00:52,845
Now, both of these measure voltage versus 
time. 

11
00:00:52,845 --> 00:01:03,100
Notice that the zero crossings, right 
here, the zero crossings all line up and 

12
00:01:03,100 --> 00:01:09,780
that's typical with resistant circuits. 
If I bring up a reactive circuit, so the 

13
00:01:09,780 --> 00:01:15,420
voltage source is in green and the 
response across any of the elements in 

14
00:01:15,420 --> 00:01:19,260
that circuit is in blue. 
Notice how there is a lag in this. 

15
00:01:19,260 --> 00:01:23,840
The response does not exactly line up 
with the input and that's typical of a 

16
00:01:23,840 --> 00:01:26,940
reactive circuit. 
And it also makes it a lot more 

17
00:01:26,940 --> 00:01:32,040
interesting and useful when we want to do 
practical applications like filtering. 

18
00:01:32,040 --> 00:01:35,925
So the basic concept I want you to 
understand in here is that if I put in a 

19
00:01:35,925 --> 00:01:40,410
sign wave to a circuit, whether a linear, 
whether a resistant circuit or reactive 

20
00:01:40,410 --> 00:01:43,980
circuit, I'm going to get a sign wave 
out. 

21
00:01:43,980 --> 00:01:47,180
With the reactive circuits, there's going 
to be a time delay, or lag in the 

22
00:01:47,180 --> 00:01:51,370
circuit. 
In both cases, the output might change 

23
00:01:51,370 --> 00:01:54,670
the amplitude, so there might be a git 
different in the amplitude from the input 

24
00:01:54,670 --> 00:01:57,880
to the output of this circuit. 
And then again in the reactive circuit, 

25
00:01:57,880 --> 00:02:04,700
there's also a time delay. 
Going back to our concept map on 

26
00:02:04,700 --> 00:02:10,530
frequency analysis. 
We will be pulling forward, the ideas and 

27
00:02:10,530 --> 00:02:16,710
analysis that we've already performed for 
RC and RLC circuits from the reactive 

28
00:02:16,710 --> 00:02:19,750
circuit module from the resistive circuit 
module. 

29
00:02:19,750 --> 00:02:25,610
We're going back to those methods to 
obtain circuit equations, so those same 

30
00:02:25,610 --> 00:02:31,826
tools, those strategies. 
The KCL, the KVL, the mesh, node, and 

31
00:02:31,826 --> 00:02:35,130
Thevenin equivalents, we will again use 
in frequency analysis. 

32
00:02:36,570 --> 00:02:40,900
The particular topics that will cover are 
going to include an introduction to 

33
00:02:40,900 --> 00:02:47,510
frequency domain, impedances, which are 
simply complex resistances, AC circuit 

34
00:02:47,510 --> 00:02:53,220
analysis Transfer functions, frequency 
response with the application to 

35
00:02:53,220 --> 00:02:53,790
filtering.