Okay, we're looking at a half wave rectifier is my circuit right there? And you should know what this is over here. That's a sine wave. All right. And what do we know from the sine wave? Well, this is my zero line here.

And this portion of my sine wave is plus. And this portion of my sine wave going down this way, is negative. What What did I say about that? That means my current reverses direction. So my current reverses direction. Every time my waveform crosses the zero axis line, which is this black one here that I'm that I'm trying to show.

Alright, so let's let's look at At this portion of the way of our waveform here, all right. So, we have plus and minus, all right. So what do we have? We have electron flow, alright? Because electrons flow against the arrow of the diode, alright. So if we have electron flow, I have a resistor right there, which is one K. I'm going to get a voltage drop across that.

Alright. So let's stop the slide and clear it off. Okay, now, from here to here, I'm negative. All right, and now my current reverses. So, now I have minus and plus right minus and plus what happens my diode is reverse bias, do I have current flow? No and I should say electron flow no electron flow.

So what happens? I have no voltage across the resistor alright. So, if I look, if I look at my waveform, what that diode is a lot as allowing is conduction on the positive swing of that sine wave and I have no conduction, therefore, no voltage across this resistor This portion of the sine wave and we repeat again. Okay, so therefore, I am only getting a half wave rectification or allowing half of that sine wave to make conduction and getting a voltage drop across the resistor. All right, that's a half wave rectifier. Okay.

And I can show it. I can show let me just stop here and put a couple of things up. So as we can see, I only the top part of that waveform, right here, right here and right here is positive, which I'm trying to show you here, which allows conduction through the diode. So it's a half wave rectification, alright. All right. Do you see that?

Now, let me let me ask you. Let me ask another question. All right, if this was my, my house current or, or if this was a sine wave in the US we have a frequency of 60 hertz. All right. So what would still be the frequency of that? Okay?

If I look at my waveform over here I have one cycle, I begin and over here, it's still 60 hertz, isn't it? Okay? Because I would have 60 of these right here to right here in one second. But look at what's going on. I only have conduction on one half of that cycle. Alright, so I'm only I'm only Conducting one quarter Well, I'm sorry, one half of the time, all right.

Okay, what would be if this here, okay? If this was my house current or my house voltage in the US, that is what 120 volts AC at 60 hertz, right. Okay. And we've talked about this in my previous courses. So what would be the value of that? Well, if you look, my zero line is here, right there.

My zero line is there. Wouldn't that be my peak voltage 1.41 Four times 120 volts, so my voltage here would be 120 volts AC times 1.414. And if you, if you look back at my module understanding voltage, current and resistance, I talked about AC voltage, and I give you all the parameters, okay? So that would be the, that's how I find a peak voltage. So, right here 1.414 times 20 is about 170 volts out idea. So right here, I get 170 volts AC peak, and then it goes down to zero.

All right, let me clear the slide off. I'm gonna write this nice here so you can see it, and then we're going to go on to the next slide. All right, I put some more information on this slide. And again, here's what I show you. Peak voltages, 120 volts, AC, RMS, I didn't put the RMS over here, but um, I show you that over here I do the math, and it's 170 volts AC peak. Alright, so that's my peak voltage right there.

Okay. Now, we, what is this circuit? It's a rectifier. Okay, it's a half wave rectifier. Because like we show you over here, it only conducts half of my sine wave. My sine wave is from here to here.

And we only like I showed you in the previous slide. I only conduct on the positive cycle of that sine wave. So it's half wave. But what I've done is I've converted that into direct current. Prior to that we had in my AC wave form right here, my sine wave, what happens? Current alternates back and forth in my circuit.

All right, all right previously without that diode, but with that diode in there, I only have current in one direction, across my load. Therefore it's direct current. All right, that's the point I'm trying to make. It's direct current. Now, if I took a if I took a meter and measured the voltage across that resistor, I would get what we call the average value or the average DC value, voltage or current Ross, my load or r1? Here, that's what I would see.

All right. And with this that the other thing, it's all math, we're not we're not going into it, that number is point 0.637 right here. All right. So the average value DC equals point 637 times the peak voltage. Okay, the average value DC equals value times zero dot 637. Okay.

But what do we have in this circuit here? Well, I'm only conducting one half of the time, right? I mean, I get conduction flow, no conduction, conduction, oh, no conduction and so forth. It keeps going on and on and on. So in This particular circuit when I have a half wave rectification I get zero dot 637 times the peak value, divided that by two. And that will give you my DC value.

So I showed you the formula I kind of did it out for you right there. It's peak voltage times 637. I do the math 170 times that divided by two is 31.45 volts, DC. Okay, DC, because current flow, and that's probably more important than you understanding how to get those numbers. current flow is only in one direction now. So with that diode, I turned an AC wave form into a DC waveform and that's what I want you to get.

And now we know how to measure that. voltage across the resistor. And what we should get our load, I should say, our load. Even though we show a resistor, it's actually some type of load. And again, I don't want to go off on a tangent, because I kind of do that without trying too much. But I'm just trying to show you that.

And when we get into more complicated circuits, you know that that r1 or that load could be an amplifier or an oscillator or or some type of monitoring circuit of some sorts. Okay, anyways, enough set on this. I'm going to clear the slide. We're going off to the next one. All right, let's look at this circuit again. And what we've done in this slide is we've added a capacitor.

All right, and what do we know about capacitors, they're an energy storage device. And if you remember, all if you've taken my RC or RL course we talked about RC time constants. So one RC time constant is our time C. Okay? discharge is C times R. So just hang on to that. It may not be obvious right now, but I'm going to go through this. So we know from the previous slide that we only conduct on this cycle here.

All right, right here. Alright, and this part of the cycle input sine wave is right here we don't conduct okay, because of what my diode my diode only allows current flow in one direction. So when I'm conducting remember what I told you, current or electrons flow against the arrow head this way All right, and they want to go into the positive side of my source All right. And what happens to this capacitor and this resistor All right, well, the capacitor will have a shortage of electrons. And therefore, this terminal here would be plus, we have current flow or electronic should say electron flow up through the resistor and we have minus and plus, remember way back when when we saw that diode, that diode shape. In fact, let me stop here and, and show it to you.

I'm going to stop the slide here and get it for you. Remember, if you remember this slide, it was this one right there. Notice the plus sign. All right, even though that's The cathode, the cathode will point to the most positive point of the circuit. So if I go back there, and I'm going to stop it here and go back, if you look here is in my cathode right here. There's the plus side of the capacitor, and the plus side of the resistor.

So it's in the most positive point of the circuit. That's, that's the point I'm trying to make. That's why they put the plus there. Okay? So again, we know that the keypad that the right here might peak voltage we showed you on the last slide, that that's going to charge up to 170 volts AC. Alright, so now what happens since we put the capacitor in there, we have no conduction right?

So What's gonna happen? The voltage across this capacitor is going to discharge through my resistor. In other words, the voltage is going to decay. So what's going to happen is at this point because think about it, when I charge this capacity, let's go over here. Now, when I charge this capacitor up, right? Ideally, I'm gonna charge that capacitor up instantaneously on this portion of the waveform, okay?

Bingo, it's charged. I stopped conduction here. All right, what's going to happen? That voltage is going to decay, or discharged through the load. And this is where I get this discharge line. And then what happens is This swings up and I charge my capacitor back up to my peak.

All right. All right. Let's clear the slide off stop clear the slide off I want to I want to tell you one more thing here all right. So, this discharge rate right how flat that would be ideally, we want that to be as we want that to be pure d a pure DC voltage, all right. So to achieve that, right, since my load on my resistance is constant, in this case, one K. I want RC which is my time constant. To be large.

So what do I do? If this is constant? Right? I need to increase the value of my capacitor. So when I increased the value of the capacitor, my RC time constant gets longer. And therefore my curve here gets flatter.

All right. That's all here. I'm after we do this with another module, then I'm going to do is how to design linear power supplies. We'll go into how to pick these components again, and then we'll put voltage regulators in there and different different different voltage values that are fixed and so forth. All right. But just what I want you to gather out here on this section, okay is in a in this this circuit, when I go to charge my capacitor because of this diode, I charge my capacitor instantaneously.

All right, in this portion here are the curve where I have no conduction, my capacitor, which is an energy storage device discharges through the resistor and this slope will depend upon my RC time constant. Since my load is constant, I can't change it. The only thing I can change is the value of my capacitor. The larger this capacitor, the larger my time RC time constant. The flatter my curve, the smaller the value of my capacity It's discharges quicker, the more of a slope, I'm going to get on my discharge. All right, that's it.

Enough said. I think you get the idea. We're going on to the next slide.