Other comments. In the opposite direction. The opposite direction is defined as reverse.

其他评论。在相反的方向。相反的方向被定义为反向。

So we can use the diode to do rectification. because it only allows the current flowing from one direction. So we can modify, or we can rectify the current. And it's typically used to convert AC. to DC current. We know alternating current is the current is sometimes positive and sometimes negative. It's defined as alternating current. So we can use the diode to convert alternating current to DC current. It means the current remains constant.

所以，我们可以使用二极管来进行整流。因为它只允许电流从一个方向流动。所以，我们可以改变，或者说是整流电流。它通常用于将交流电转换为直流电。也就是将交流电转换为直流电。我们知道，交流电的电流有时是正的，有时是负的。它被定义为交流电。所以，我们可以用二极管将交流电转换为直流电。这意味着电流保持恒定。

So we can use the diode to convert the negative current.

所以，我们可以用二极管将负电流转换过来。

So we can prevent the negative current in the AC. In the AC, there are sometimes current is positive, sometimes negative. But if you use a diode, the negative current cannot flow through. So you only get positive current.

这样就能防止交流电中的负电流。在交流电中，电流有时为正，有时为负。但是，如果你使用二极管，负电流就无法通过。这样你就只得到正电流了。

And here we show the the current and the voltage. characteristic. So if the current shows on the right side, x-axis is the voltage. y-axis is the current.

这里我们展示了电流和电压。特性曲线。所以，如果电流显示在右侧，那么x轴就是电压。y轴就是电流。

And this figure is the current-voltage characteristic.

这张图就是电流-电压特性曲线。

And here you can see when the voltage is positive, you just apply very small voltage, and you can get very large current. This is the forward current, which means the current can flow through the diode. And when the voltage is negative, which means the current is flowing through the other direction. it prevents the flowing. So the current cannot get through of diode. As a result, you will get very small current. It's nearly zero. But when the voltage is too large, you will get breakdown. which means the diode is broken.

在这里你可以看到，当电压为正时，你只需要施加很小的电压，就会得到非常大的电流。这就是正向电流，意味着电流可以流过二极管。而当电压为负时，这意味着电流无法流过另一个方向。它阻止了电流的流动。所以，电流无法通过二极管。因此，你会得到非常小的电流。几乎为零。但是，当电压过大时，就会发生击穿。这意味着二极管已经损坏了。

If the voltage is too large, you will get breakdown. That means the diode is broken. In this case, it can still get very large. this is a minus reverse voltage.

如果电压过大，就会发生击穿。这意味着二极管坏了。在这种情况下，它仍然会变得非常大。这是一个负的反向电压。

and here, there is an important note here. and the diode began to conduct electricity only if a certain threshold voltage. or turning voltage is present. in a forward direction. That means if the voltage is too small, such as 0.1, it won't.

这里有一个重要的注意事项。二极管只有在电压达到一定阈值时，才会开始导通。也就是存在导通电压。这是指正向导通的情况。也就是说，如果电压太小，比如0.1，就不会导通。

the current cannot flow through. So there is an internal resistance in the diode. So the voltage must be larger enough in order to make sure the current can flow through the internal resistance. And this is defined as the turning voltage or threshold voltage.

电流无法通过。所以，二极管内部存在内阻。因此，电压必须足够大，才能确保电流能够流过内阻。这被称为导通电压或阈值电压。

also defined as forward bias. or bias state.

也称为正向偏置。或者偏置状态。

Because of the internal resistance of the diode, you must apply voltage and make sure the current can flow through the resistance.

由于二极管存在内阻，所以必须施加电压，才能保证电流流过内阻。

And the voltage drop, also the voltage reference across the forward diodes, is the diodes. varies very little with the current. And it is a function of temperature.

而二极管两端的压降，也就是正向导通时的电压参考值，就是二极管的导通电压。它几乎不随电流变化。而且它是温度的函数。

That means we need to apply a small voltage. to the diodes. in order to make the current flow through. And this voltage drop because of the internal resistance,

这意味着我们需要施加一个较小的电压。到二极管上。这样才能让电流通过。而由于内阻造成的电压降，

varies people. but doesn't change too much. And the resistance, the voltage drop is a function of temperature.

因人而异。但变化不会太大。而电阻和电压降是温度的函数。

And here we can see the concrete example. For the silicon diodes, the voltage drop is 0.7. Which means the voltage, the passing voltage should be larger than this value. It's a threshold. Also defined as the parking voltage. Every side, 0.7. It's the parking voltage or defined as threshold voltage. Because of the internal resistance of diode. The voltage must be larger than this small number. In order make sure the current can flow through the diode.

这里我们可以看到一个具体的例子。对于硅二极管来说，其电压降是0.7伏。这意味着，通过它的电压必须大于这个值。这是一个阈值。它也被称为导通电压。两边都是0.7。这就是导通电压，或者说是阈值电压。这是因为二极管存在内阻。所以电压必须大于这个很小的数值。这样才能确保电流能够流过二极管。

And for the I-V, I current, V voltage characteristic, and we have introduced in two directions. One is reverse. reverse bias.

至于电流-电压特性曲线，我们已经从两个方向进行了介绍。一个是反向的。反向偏置。

which means the current cannot flow through the diode.

这意味着电流无法流过二极管。

But if the voltage is larger enough, the diode will be broken.

但是，如果电压足够大，二极管就会被击穿。

in that case, the current can flow through the diode. But generally, if the voltage is not so large,

在这种情况下，电流就可以流过二极管了。但通常情况下，如果电压不够大，

the diode is an insulator. so it can't be reversed.

二极管就相当于一个绝缘体。所以它无法导通。

And for the forward bias, which means the voltage can flow through the diode. but it must be larger than the built-in potential. The built-in potential is the threshold voltage. We have already introduced in the first slide.

而对于正向偏置，这意味着电压可以流过二极管。但必须大于内建电势。内建电势就是阈值电压。我们在第一张幻灯片里已经介绍过了。

And the p-n junction diode allows p is positive, n is negative. allows some potential, and then the current flows. So the current can flow through the diode. This is the forward bias.

而p-n结二极管，p区是正极，n区是负极。这样就会产生电势差，电流就能流过。所以电流可以穿过二极管。这就是正向偏置。

And here are the I-V characteristic. I is the current, V is the voltage. So ideally, there's no internal resistance. So when you apply the voltage, when you apply a positive voltage, you will get a current.

这里是I-V特性曲线。I代表电流，V代表电压。理想情况下，没有内阻。所以当你施加电压时，施加正电压，就会有电流。

And when you apply negative voltage, it cannot flow through. so it has zero current. So ideal diodes.

而当你施加负电压时，电流无法通过。所以电流为零。这就是理想二极管。

As the I-V characteristic on the left side. Ideal diode has the I-V characteristic shown on the left figure. But in the real world, there is internal resistance. So the voltage must be larger. must be larger than 0.7.

就像左边的I-V特性曲线一样。理想二极管的I-V特性如左图所示。但在现实世界中，存在内阻。所以，电压必须更大。必须大于0.7。

in order to make the current flow through the internal resistance.

这样才能让电流流过内阻。

And the figures at the right side shows the internal structure. of the p-n junction. or internal structure of the diode.

右边的图展示了内部结构。也就是PN结的结构。或者说是二极管的内部结构。

So here we will apply positive, the figure c, for example, we will apply positive voltage. we apply positive voltage for the p junction. the current can flow through.

比如在这里，我们会施加正向电压，就像图c所示的那样。我们给PN结施加正向电压。这样电流就可以流过。

And here you can see the electron can flow through. negative electron can flow through the p junction from n.

大家可以看到，电子可以流过。负电荷（电子）可以从N区流向P区。

But here in example three, when the voltage is applied from the negative and p, the barrier of the p-n junction

但是在例三这里，当电压从N区和P区施加时，PN结的势垒

and there is a very large resistance area in the middle. So current cannot pass through the pn junction in this case.

中间会有一个非常大的电阻区域。因此，电流无法通过。在这种情况下，PN结就是如此。

And we have introduced the I-V characteristic, right? And I think they are familiar with the I-V characteristic.

我们已经介绍了I-V特性，对吧？我想大家对I-V特性应该都很熟悉了。

And at very large reverse bias,

而在非常大的反向偏置下，

you might have breakdown.

可能会出现击穿现象。

So if you apply reverse voltage,

所以，如果你施加反向电压，

at the beginning there's no current, no it's through the diode. And if the voltage is too much, you will have breakdown. the diode will be broken. And you are damaged the diode. And in this case, you will also get large current going through the diode.

一开始是没有电流的，不会流过二极管。但如果电压过高，就会发生击穿。二极管就会被损坏。这样就会损坏二极管。在这种情况下，还会有大电流流过二极管。

This is the region at back side, breakdown region.

这是背面的区域，即击穿区。

And when the voltage is smaller, smaller than the breakdown voltage, you will get very small. reverse current. The current very small because the diode prevents the flowing of the current.

当电压小于击穿电压时，电流会非常小。也就是反向电流。电流非常小，因为二极管阻止了电流的通过。

In this case, the diode works like an insulator. it's like an open circuit. so there is no current, right? that's the reason in the middle. that's the region in the middle, reverse region. there's no current. And a diode is looks like an insulator. It's open circuit.

在这种情况下，二极管的作用就像一个绝缘体。就像开路一样。所以没有电流，对吧？这就是中间部分的原因。那就是中间的区域，也就是反向区域。这里没有电流。而且二极管看起来就像一个绝缘体，相当于开路。

And there is another region. The other region is more forward. it's more forward bias.

还有另一个区域。那个区域是正向的。也就是正向偏置。

Because of the internal resistance, you have to apply a certain voltage.

由于存在内阻，你必须施加一定的电压。

in order to make the current flowing.

才能让电流流过。

And you know, the current and the voltage curve is exponential.

大家都知道，电流和电压的关系曲线是指数型的。

And it can be given by this equation.

它可以用这个公式来表示。

And here the typical I-V characteristic again. So y-axis is the current, x-axis is the voltage.

这里再次展示了典型的I-V特性曲线。纵轴是电流，横轴是电压。

So here we have a threshold voltage, right? It must be larger than this. Then the current will be increased. It increases exponentially with the voltage.

这里有一个阈值电压，对吧？它必须大于这个值。这样电流才会增加。电流会随着电压呈指数增长。

And here is the reverse current. In this region, the diode is like an insulator. it's open circuit. But there's no current, very small current.

这里是反向电流。在这个区域，二极管就像一个绝缘体。相当于开路。但是没有电流，或者只有非常小的电流。

But when the voltage is large, you will have a breakdown. In this case, you will get large current flow.

但是，当电压很大时，就会发生击穿。在这种情况下，就会有大的电流流过。

And here we also define the threshold voltage as the barrier potential. also known as the knee voltage. So we have different definition for this threshold voltage. or defined as the knee voltage.

这里我们还把阈值电压定义为势垒电位。它也被称为拐点电压。所以，对于这个阈值电压，我们有不同的定义。或者定义为拐点电压。

And as larger voltage, larger voltage, either the current and the ohmic resistance are larger.

而当电压增大时，无论是电流还是欧姆电阻，都会增大。

and the exponential curve becomes a straight line.

而且，指数曲线会变成一条直线。

This is because now it's the bundle resistance.

这是因为现在它变成了串联电阻。

Also, we introduced the when the voltage is larger than the knee voltage, the current will increase exponentially.

另外，我们还提到，当电压大于拐点电压时，电流会呈指数增长。

but if the voltage is too large, in this case, the exponential curve will become a straight line. because the resistance is dominant in this case.

但是，如果电压过大，在这种情况下，指数曲线就会变得是一条直线。因为在这种情况下，电阻起主导作用。

And if come back here, here you can see at the region at the right side,

如果我们回到这里，大家可以看到，在右侧的区域，

the current increase exponentially. but when the voltage is too large, you will get a straight line.

电流是呈指数增长的。但当电压过大时，就会变成一条直线。

because the resistance is dominant here.

因为这里的电阻起主导作用。

okay, LED. LED is light emitting diode.

好的，LED就是发光二极管。

It's a typical use case of diode. This diode can produce the light. And we typically use these two kind of symbols. to represent LED.

这是二极管的一个典型应用。这种二极管可以发光。我们通常使用这两种符号来表示它。用来代表LED。

And these figures show how they look like in the real world. I think some people has already used LED.

这些图展示了它们在现实世界中的样子。我想有些人已经用过LED了。

When you play with the PCB, it's often has some LED.

当你玩电路板的时候，上面通常会有LED灯。

The light emitting diodes has also had a very short history.

发光二极管的历史其实也很短。

And the first diode was made in 1907.

第一个二极管是在1907年制造的。

And it's about

到现在大约有

100 years of life and improvement from the diodes. When you apply voltage to the diodes,

100年的历史和改进。当你给二极管施加电压时，

but that was the first function. 100 years ago.

但那是它的第一个功能。那是100年前的事了。

In 2006, a Japanese researcher demonstrated the first high-brightness blue LED.

2006年，一位日本研究人员展示了第一个高亮度蓝色LED。

so the light of the diodes can be nearly can be very thin.

所以，二极管发出的光几乎可以非常微弱。

So after 2006, every LED can produce very clear light.

所以，从2006年以后，所有的LED都能产生非常清晰的光。

And it produce a light of a single color.

而且，它发出的光是单一颜色的。

By combining holes and electrons.

这是通过空穴和电子的结合产生的。

in a semiconductor. So there are so many, you can see there are so some holes and electrons, right? And here you apply the voltage.

发生在半导体中。所以，你可以看到，这里有很多空穴和电子，对吧？然后，在这里施加电压。

Apply a voltage across the diodes. The diode will produce light.

在二极管两端施加电压。二极管就会发光。

You can produce different colors of light. blue, yellow, orange, etc.

你可以产生不同颜色的光。比如蓝色、黄色、橙色、等等。

depends on how you combine.

这取决于你如何组合它们。

For example, here you apply the voltage source. The positive voltage is applied to the n-type of layer. And the negative voltage is applied to the p-type layer. And the LED can produce light. But one LED just produce one color of light. If you just want to get different colors, you have to combine them together.

例如，在这里你施加了一个电压源。正电压施加在n型层上。负电压则施加在p型层上。这样，LED就能发光了。但是，一个LED只能发出一种颜色的光。如果你想得到不同的颜色，就必须把它们组合在一起。

For example, the LED produces only blue, and another LED produces yellow. when you combine them together, you can get white.

比如，一个LED只发出蓝光，另一个LED只发出黄光。当你把它们组合在一起时，就能得到白光。

There are different ways to get white. And here, if you apply blue LED and green LED and red LED, you can also get white.

获得白光的方法有很多种。在这里，如果你使用蓝光、绿光和红光LED，也能得到白光。

And after two seconds, because the LED is fading, the LED. it's out.

不过，两秒钟后，因为LED会衰减，就熄灭了。

And people find many different applications like this. And also, that research also get Nobel Prize for this achievement.

人们发现了这种技术的许多不同应用。而且，这项成果还获得了诺贝尔奖。

So LED is actually a p-n junction diode.

所以，LED实际上是一种PN结二极管。

It's a kind of diode.

它是一种二极管。

And when carriers are injected across a forward biased junction, it emits a photon. incoherent light.

当载流子注入正向偏置的PN结时，就会发出光子。这是一种非相干光。

The two materials are the p-n junction.

这两种材料构成了PN结。

It's forward biased, right? Forward biased junction. So the current can flow through the diode. It can emit incoherent light.

它是正向偏置的，对吧？正向偏置的PN结。这样电流就可以流过二极管，并发出非相干光。

And LED are made of a thin layer, very thin layer of heavily doped semiconductor.

而LED是由一层非常薄的、重掺杂的半导体材料制成的。

And when forward biased, the LED is emitting light. at a particular wavelength.

当正向偏置时，LED就会发光。而且是在特定的波长下。

That's the reason you can just see one color, right? One color produced by the LED.

这就是为什么你只能看到一种颜色，对吧？LED发出的光只有一种颜色。

And the color depends on the material. You can produce different lights. Some LED produce blue. And the other produce a yellow.

而颜色取决于材料。你可以发出不同的光。有些LED发出蓝光。而另一些发出黄光。

Here we have many LEDs produce different colors, right? And here shows the ID. characteristic. The y-axis is the voltage, y-axis is the current.

这里有很多LED可以发出不同的颜色，对吧？这里显示的是ID。特性。横轴是电压，纵轴是电流。

and in order to produce light.

这是为了产生光。

The LED requires current. and it flows through it. So you must apply a voltage. in order to produce current, in order to produce light. In order to produce light, you must apply voltage to the LED.

LED需要电流。电流会流过它。所以，你必须施加电压。这样才能产生电流，进而产生光。为了发光，你必须给LED施加电压。

and the light intensity is dependent on the current. If you apply larger current to a LED,

而光的强度取决于电流。如果你给LED施加更大的电流，

you will get a brighter If you apply larger current, you will get a brighter light. The light intensity is dependent on the current. So it's kind of a current-dependent device.

它就会变得更亮。如果电流更大，光线就更亮。光的强度取决于电流。所以，它是一种电流依赖型器件。

And you must protect the LED. So you should use a resistor in series with the LED. to protect.

而且，你必须保护LED。所以，你应该在LED串联一个电阻。起到保护作用。

So the current must be limited. if the current is too high.

因此，电流必须受到限制。如果电流过高。

If the current exceeds the limit of the LED, it breaks the LED.

一旦电流超过LED的极限，LED就会被损坏。

So you must use a resistor to protect the LED.

所以，你必须使用电阻来保护LED。

And the current is usually limited from 5 microampere to 30 microampere.

通常，电流限制在5微安到30微安之间。

depending on the brightness. if you want to brighter, then you increase the current limitation. but not larger than 30 microampere.

具体取决于所需的亮度。如果你想让它更亮，就需要增大电流限制。但不能超过30微安。

A typical current range is from 5 microampere to 30. So you must limit the current to protect the LED.

典型的电流范围是5微安到30微安。所以，你必须限制电流来保护LED。

So you don't never connect LED directly with the power supply. you must always use a resistor. to limit the current.

因此，千万不要将LED直接连接到电源上。一定要使用电阻。用来限制电流。

And here is the range, from 5 to 30. But a typical forward current is 20.

这里是电流范围，从5到30。但典型的前向电流是20。

And the LED are usually operated from a low DC direct current voltage. And 25 mA is very low, right? It's a low value.

而且，LED通常是在低直流电压下工作的。25毫安非常低，对吧？这是一个很小的数值。

So operate from very low DC voltage.

所以，它是在非常低的直流电压下运行的。

And here is the example to illustrate. how the LED should be connected in series. The resistor is used to limit current.

这里有一个例子来说明。就是LED应该如何串联连接。电阻的作用是限制电流。

So if you know the current, right? and you know the voltage, so you can calculate the something. you can compute the corresponding resistance. to protect the LED.

所以，如果你知道电流，对吧？也知道电压，那么你就可以计算出一些东西。你可以计算出相应的电阻值。以此来保护LED。

And resistance is defined as it's used to limit current.

电阻的定义就是用来限制电流的。

And here's an example.

这里有一个例子。

An RTI2080 or 180 is a forward voltage drop. 3.2 volts. It's connected to a 5 volt. stabilizer. This is the power supply. Power supply has 5 volts. And the internal voltage drop is 2 volt. So you must 5 volt minus 2. It's a 3 volt. The resistor. And if you want to limit current,

RTI2080或180的正向压降是3.2伏。它连接到一个5伏的电源。稳压器。这是电源。电源提供5伏电压。而它的内部压降是2伏。所以，你必须用5伏减去2伏。结果是3伏。这就是电阻。如果你想限制电流，

how much larger or less than 10?

应该比10大多少还是小多少？

3 for ampere.

3安培。

so the resistor must be larger than 300. in order to limit the current.

所以，电阻必须大于300。这样才能限制电流。

And if you connect the diodes in series, it's a 100 ohms resistor. Then you can compute the current currently flowing through the diodes.

如果你把二极管串联起来，就相当于一个100欧姆的电阻。这样你就能计算出流过二极管的电流。

Great, can you explain?

很好，你能解释一下吗？

Thank you, Gary. If a diode is connected in series with a 100 ohms resistor, you can compute the current flowing through the diodes. And this resistor protect the LEDs.

谢谢，加里。如果二极管与一个100欧姆的电阻串联，你就可以计算出流过二极管的电流。而这个电阻是为了保护LED。

LEDs have the same power requirements.

LED的功率要求是一样的。

And you can connect them together. Increase the voltage.

你可以把它们串联起来。这样会增加电压。

If you have many LEDs,

如果你有多个LED，

the light intensity will also be increased.

光的强度也会随之增加。

And it will be brighter. A brighter light. If you just have one LED, it might be a little bit dark. But if you have many LEDs connected in series, it will be very bright.

这样就会更亮。光线更亮。如果你只有一个LED，可能会有点暗。但如果你把多个LED串联起来，就会非常亮。

And it's better to connect the same color LEDs. If one LED produces blue, another produces yellow. you cannot connect them together. All these LEDs produce the same color, the light will be more brighter.

最好连接相同颜色的LED。如果一个LED发蓝光，另一个发黄光，就不能把它们连在一起。如果所有这些LED都发出相同颜色的光，光线就会更亮。

And in this case, you have to compute the total voltage drop.

在这种情况下，你必须计算总电压降。

The voltage drop for these three LEDs.

就是这三个LED的电压降。

And here, if one LED is 2.5 volt,

这里，如果一个LED是2.5伏，

then the total voltage is

那么总电压就是

three LEDs. it's 3.6.

三个LED的总和。也就是3.6伏。

And the voltage for the resistor is the total voltage minus the voltage of the LEDs. you will get 1 volt.

电阻上的电压等于总电压减去LED的电压。这样就能得到1伏。

And in order to limit the current to 10 microamperes, so you get the resistor.

为了将电流限制在10微安，就需要计算电阻值。

and for the three LEDs,

对于这三个LED，

there are some typical use case of LED. you can see some traffic light, right? and also the rear light, the rear light of a car. It's also use LED. All the headlight, I think many parts, many parts of headlight also use LED.

这里有一些LED的典型应用场景。大家可以看到交通信号灯，对吧？还有汽车的尾灯。也是用LED的。我觉得车灯里的很多部件，也都使用了LED。

And finally, there are also some advantages and disadvantages of using LED.

最后，使用LED也有一些优点和缺点。

it can produce light, but it requires very little energy. so it's energy saving. It's an energy-saving devices. Produce light but requires very little energy.

它能发光，但所需的能量非常少。所以它很节能。它是一种节能设备。能发光，却只需要很少的能量。

And it can produce light.

而且它能发光。

It's very popular.

它非常受欢迎。

This means you don't need a color filter.

这意味着你不需要彩色滤镜。

It produce very pure light. And coherent light. And we don't have to use a filter.

它发出的光非常纯净。而且是相干光。我们不需要使用滤镜。

And also, for example, it has very long life. And it's efficient, it's great for energy.

另外，比如，它的使用寿命非常长。而且效率高，非常节能。

If your application is not so large.

如果你的应用规模不是很大。

It worth the cost.

那么它是值得投入成本的。

And they were failed down slowly, very slowly.

而且它们会缓慢地、非常缓慢地失效。

All of them suddenly went out.

但突然间，它们全都熄灭了。

And it light up very quickly. I don't check, maybe it was a light. And very small, the size is very small. You can produce it in any way easily.

而且它们亮起来非常快。我没仔细看，也许那只是灯光。而且体积非常小。你可以很容易地以任何方式生产它。

And for sure, and also some people want to. There are some people who have this.

而且肯定的是，有些人确实想要它。已经有人拥有了。

The first line is package. Nobody is anything about the package for now.

第一行是包装。目前还没有人提到包装的事。

And the performance depends on the environment.

而且性能取决于环境。

like the temperature.

比如温度。

And must be sometimes with the correct current.

而且有时必须使用正确的电流。

In order to produce the correct current, you must use a series resistors. or a constant regulator.

为了产生正确的电流，你必须使用串联电阻。或者一个稳压器。

That's all. That's all for lecture nine. This is the second last lecture. And here is a brief summary.

就这些。这就是第九讲的全部内容。这是倒数第二讲。这里有一个简要的总结。

Capacitance is used for storing

电容用于存储

electric charge, right? And it can be expressed, C is the capacitance, can be expressed by the charge divided by the voltage applied.

电荷，对吧？它可以表示为：C是电容，等于电荷除以外加电压。

at the terminals.

在两端之间。

And for the capacitors, they are in parallel. You can add them together to get the equivalent capacitance. But if they are connected in series, you use this equation.

至于电容器，它们是并联的。你可以把它们加在一起，得到等效电容。但如果它们是串联的，就要用这个公式。

and the energy stored in a capacitor is half of the capacitance times the voltage squared.

电容器中储存的能量是电容的一半。乘以电压的平方。

And the energy can be expressed as E.

能量也可以表示为E。

of the capacitor equals the voltage applied to the capacitor.

它等于施加在电容器上的电压。

when you find a distance, when the distance is in the two case.

当你计算距离时，有两种情况。

Let's move to lecture one. and we only have one lecture left. Let's do the tutorial first. for this lecture.

让我们进入第一讲。我们只剩下一节课了。我们先来做一下练习题。针对这一讲的内容。

And this question is kind of simple. Just how we use this.

这个问题很简单。就是看我们如何使用它。

The current flows in the opposite direction. The opposite direction is defined as the reverse direction. We can use a diode to do rectification, because it only allows the current to flow in one direction. So we can rectify the current, and it is typically used to convert AC, alternating current, to DC current. Alternating current is the current that is sometimes positive and sometimes negative. That is defined as alternating current.

电流沿相反方向流动。相反方向定义为反向。我们可以使用二极管进行整流，因为它只允许电流沿一个方向流动。因此我们可以对电流进行整流，它通常用于将交流电（AC）转换为直流电（DC）。交流电是指有时为正、有时为负的电流，这就是交流电的定义。

A diode converts negative current to positive current. This is called rectification—the current remains constant in one direction. In AC, current is sometimes positive and sometimes negative. If you use a diode, negative current cannot flow through, so you only get positive current.

二极管将负电流转换为正电流，这称为整流——电流保持单方向恒定。在交流电中，电流有时为正，有时为负。如果使用二极管，负电流无法通过，因此你只能得到正电流。

And here we show the current-voltage characteristic. The X-axis is voltage, and the Y-axis is current. This figure shows the current-voltage characteristic.

这里我们展示电流-电压特性曲线。横轴为电压，纵轴为电流。该图即为电流-电压特性曲线。

When the voltage is positive, you just apply a very small voltage and you can get very large current. This is the forward current, which means the current can flow through the diode. And when the voltage is negative, this means the current is flowing in the other direction. It prevents the flow of current, so the current cannot get through the diode. That is the reason you get very small current — nearly zero. But when the voltage is too large, you get breakdown, which means the diode is broken.

当电压为正时，只需施加一个很小的电压，就能得到非常大的电流。这就是正向电流，意味着电流可以通过二极管。而当电压为负时，意味着电流沿相反方向流动，它阻止了电流的通过，因此电流无法穿过二极管。这就是为什么你得到的电流非常小——几乎为零。但是当电压过大时，就会发生击穿，这意味着二极管被损坏了。

If the voltage is too large, it will get breakdown. In this case, you can still get very large reverse voltage. Here, there is an important note: a diode begins to conduct electricity only if a certain threshold voltage, or turning voltage, is present in the forward direction. That means if the voltage is too small, such as 0.1 V, see here—

如果电压过大，就会发生击穿。在这种情况下，你仍然可以获得很大的反向电压。这里有一个重要的注意事项：二极管只有在正向方向上存在某个阈值电压（即开启电压）时才会开始导电。也就是说，如果电压太小，比如0.1伏，看这里——

The current passes through the diode. There is an internal resistance in the diode, so the voltage must not be very large in order to make sure the current can flow through the internal resistance. This is defined as the cutoff voltage or threshold voltage. It is also defined for the forward bias state.

电流通过二极管。二极管内部存在内阻，因此电压不能太大，以确保电流能够流过该内阻。这被定义为截止电压或阈值电压。它也适用于正向偏置状态。

Because of the internal resistance of the diode, you must apply a voltage across the diode to ensure that current passes through the resistance. The voltage drop across the forward-biased diode varies very little with the current; it is a function of temperature.

由于二极管存在内阻，必须在二极管两端施加电压，以确保电流通过该电阻。正向偏置二极管两端的压降随电流变化很小，它是温度的函数。

That means we need to apply small voltages. However, we must connect the current source. These voltages drop because of internal resistance. As current flows through the chemical junction, the current changes. The voltage drop is a function of temperature.

这意味着我们需要施加小电压。但与此同时，我们必须连接电流源。由于内阻的存在，这些电压会产生压降。当电流流过化学结点时，电流会发生变化。电压降是温度的函数。

And here we can see the example for the silicon diode. The voltage drop is 0.7, which means the positive voltage should be larger than this value. It is a threshold voltage, also defined as cut-in voltage. Because of the internal resistance of the diode, the voltage must be larger than this small number in order to make sure the current can flow through the diode.

这里我们可以看硅二极管的例子。其压降为0.7伏，这意味着正向电压必须大于该值。这是一个阈值电压，也称为导通电压。由于二极管存在内阻，电压必须大于这个较小的数值，才能确保电流流过二极管。

For the current in the voltage characteristic, you have introduced two directions. One is reverse bias, which means the current cannot flow through the diode. If the voltage is large enough, the diode will be broken. In that case, the current can…

对于电压特性中的电流，你们已经介绍了两个方向。一个是反向偏置，这意味着电流无法通过二极管。如果电压足够大，二极管将会被击穿。在这种情况下，电流可以……

Water can flow through the nanotube. Generally, if the voltage is not so large, the nanotube is an insulator, so you can prevent the flowing of the current. For a bias, this means the water can flow through the nanotube, but it must be larger than the built-in potential. The built-in potential is the threshold voltage you have in the forward bias on the p-n side.

水可以流经纳米管。通常，如果电压不够大，纳米管就是绝缘体，因此可以阻止电流的流动。对于偏置电压而言，这意味着水可以流经纳米管，但偏置电压必须大于内建电势。内建电势就是p-n端正向偏压中的阈值电压。

A diode has two terminals: anode and cathode. It allows positive current entering the anode and exiting the cathode. It allows current to flow in the forward direction only. This is forward bias. Here on the I-V characteristic, I is the current, V is the voltage. Ideally, there is no internal resistance. So when you apply a positive voltage, you get current.

二极管有两个端子：阳极和阴极。它允许正向电流从阳极流入、从阴极流出。它只允许电流沿正向流动，这就是正向偏置。在I-V特性曲线上，I代表电流，V代表电压。理想情况下，不存在内阻。因此，当施加正向电压时，就会产生电流。

When you apply negative voltage, another voltage source, it has zero current. The ideal diode IV characteristic is shown on the left figure. But in the real world, there is internal resistance of the diode. So the voltage must be larger than 0.7 to make the current flow.

当你施加负电压时，即另一个电压源，电流为零。理想二极管的伏安特性曲线如左图所示。但在实际中，二极管存在内阻，因此电压必须大于0.7伏才能使电流通过。

Internal resistance. The figures on the right side show the internal structure of the junction, or the internal structure of the diode. Here we have a time of…

内阻。右侧的图展示了结的内部结构，或者说二极管的内部结构。这里我们有一个……时间

When positive voltage is applied to the p-n junction of a diode, current can flow through. Here you can see the electrons at the cathode flow through; positive ions at the anode, negative electrons at the cathode, and negative ions at the anode.

当正向电压施加到二极管的 p-n 结上时，电流可以通过。这里可以看到阴极的电子流过；阳极有正离子，阴极有负电子，阳极有负离子。

The topological property is that there is a negative parity of the Green's function. There is a very large resistance in the middle, which prevents us from getting a current across the Green's function in this case. Here we use the I-V characteristic, specifically the correlation for the I-V characteristic.

拓扑性质是格林函数具有负宇称。中间存在非常大的电阻，这使得在这种情况下我们无法获得穿过格林函数的电流。这里我们使用I-V特性曲线，具体来说是I-V特性曲线的关联。

After that, we discuss reverse bias. If you apply reverse voltage, no current flows through the diode. However, if the voltage is too high, breakdown occurs and the diode is damaged. In this case, a large current flows through the diode.

接下来我们讨论反向偏置。如果施加反向电压，则没有电流流过二极管。然而，如果电压过高，就会发生击穿，二极管将被损坏。在这种情况下，会有大电流流过二极管。

The Eastern region and the Great Lakes region—the voltage is smaller than the Great Lakes voltage. The current is very small, on the order of nanoseconds, following the current.

东部地区与五大湖地区相比，电压低于五大湖地区的电压。电流非常小，在纳秒量级，跟随电流变化。

In reverse bias, the diode works like an insulator — it is an open circuit, so there is no current flowing. That is why we call this the reverse region. In forward bias, current is allowed to flow.

在反向偏置下，二极管相当于一个绝缘体——它是一个开路，因此没有电流流过。这就是为什么我们称之为反偏区。而在正向偏置下，电流可以流通。

You have to apply a certain voltage in order to make the current flow through the internal resistance. And the current–voltage curve is exponential. It can be given by this equation. And here the typical IV characteristic again: so y-axis is the current, x-axis is the voltage. Here we have...

你必须施加一定的电压，才能使电流流过内阻。电流–电压曲线是指数型的，可以用这个方程来表示。这里是典型的IV特性曲线：y轴是电流，x轴是电压。这里我们有……

Stress on the voltage. If I have a positive voltage, it must be larger than this stress on the voltage. Then the current will be increased exponentially with voltage. On the other hand, reverse current in this region, the diode is acting as an insulator. It is open circuit. There is no current, or very small current. But when the voltage is too large, you will have breakdown.

电压应力。如果我施加正向电压，它必须大于这个电压应力阈值。此时电流将随电压呈指数增长。另一方面，在这个区域的反向电流下，二极管充当绝缘体，相当于开路，没有电流或只有极小的电流。但是当电压过大时，就会发生击穿。

We define the threshold voltage in two ways. First, it is the barrier potential. Second, it is also known as the knee voltage. So we have two different definitions for this threshold voltage.

我们对阈值电压有两种定义方式。第一，它是势垒电位。第二，它也被称为膝电压。因此，阈值电压有两个不同的定义。

Antoine Lavoisier, either the government and the opposition of the times.

安托万·拉瓦锡，无论是政府还是当时的反对派。

An exponential curve becomes a straight line because the slope is constant—the resistance is constant. When the voltage is larger, the current is more likely to increase exponentially with voltage. If the voltage is too large, the exponential curve becomes a straight line because the resistance dominates.

指数曲线会变成一条直线，因为斜率是恒定的——电阻是恒定的。当电压较大时，电流更可能随电压呈指数增长。如果电压过大，指数曲线会变成一条直线，因为电阻起主导作用。

Here you can see at the region on the right side, the current increases because Ohm's law is V equals IR, right? But when the voltage is too large, it will get a straight line—saturation—because the resistance becomes infinite here. And the LED is like a forward-biased diode.

在这里你可以看到右侧区域，电流增大，因为欧姆定律是V等于IR，对吧？但是当电压过大时，它会变成一条直线——饱和——因为这里的电阻变为无穷大。而LED就像一个正向偏置的二极管。

A typical use case of a diode is the LED. This diode can produce light. We typically use these two kinds of symbols to represent LED, which stands for Light Emitting Diode. And this picture shows how they look in the real world. Some people have already used LEDs when you play these...

二极管的一个典型应用是LED。这种二极管可以发光。我们通常使用这两种符号来表示LED，即发光二极管（Light Emitting Diode）。这张图展示了它们在现实中的样子。有些人在玩这些……时已经用过LED了。

LEDs are also known as Light Emitting Diodes. LED lights emit light through diodes, and this technology has a very short history. The first diode was made in 1907, about one hundred years ago. It was introduced from the diode — at that time it was not yet called a diode; it was only later given that name.

LED也称为发光二极管。LED灯通过二极管发光，这项技术历史非常短暂。第一个二极管于1907年制造，距今约一百年。它源自二极管——当时尚未被称为二极管，只是后来才被赋予这一名称。

Ban Gu was the first to compile the Book of Han. A 2006 Chinese researcher demonstrated that the first time the Book of Han was published was in 181 AD. The last line can be very thin.

班固是第一个编纂《汉书》的人。一位2006年的中国研究者证明，《汉书》首次刊行是在公元181年。最后一行可能非常细。

After 2006, energy has to produce very clear lines. Actually, it produces a line of single color by combining holes and electrons in a semiconductor. So there are so many…

2006年之后，能量必须产生非常清晰的谱线。实际上，它通过在半导体中组合空穴和电子来产生单色谱线。所以有非常多……

In a semiconductor, it depends on the force acting on electrons. Here, you apply voltage across the diode, and the diode will produce light. You can produce different colors of light—blue, yellow, orange, and so on—depending on how you combine the colors.

在半导体中，这取决于作用在电子上的力。在这里，你在二极管两端施加电压，二极管就会发光。你可以产生不同颜色的光——蓝色、黄色、橙色等等——这取决于你如何组合这些颜色。

For example, here you apply a voltage. The positive voltage is applied to the p-type junction, the p-type material, and the negative voltage is applied to the n-type junction, the n-type material. And it causes the LED to increase in size. One LED corresponds to one color of light. If you put two LEDs, you get two different colors combined together.

例如，这里施加一个电压。正电压加在P型结上，即P型材料上；负电压加在N型结上，即N型材料上。这会导致LED的尺寸增大。一个LED对应一种颜色的光。如果使用两个LED，就会得到两种不同颜色组合在一起的光。

An LED produces blue, and another LED produces yellow. When you combine them together, you can get white. There are different ways to get white. You can combine a blue LED, a green LED, and a red LED to also get white when you combine them. After 2006, because of LEDs, the spread of LEDs is very important. People find many...

一种LED产生蓝光，另一种LED产生黄光。将它们组合在一起，就可以得到白光。获得白光有不同的方式。你也可以将蓝色LED、绿色LED和红色LED组合起来得到白光。2006年之后，由于LED的出现，LED的普及变得非常重要。人们发现许多……

Different classifications correspond to different achievement levels. Energy is actually a function of value—a functional value.

不同的分类对应不同的成就等级。能量实际上是价值的函数——一个功能值。

Once one carrier is identified for both polarized states of light, polarized light can be used in coherent light. However, when you apply voltage, the two channels are PM—polarized channels—so current can flow through the channel and it can emit incoherent light.

一旦为光的两个偏振态确定了一个载波，偏振光就可以用于相干光。然而，当施加电压时，两个通道是PM——即偏振通道——因此电流可以通过该通道，并发射非相干光。

E_g equals hc over lambda. And when the forward bias of the LED is limited by the particular wavelength, it is limited by the particular wavelength that is basically lambda_c, 1 point 1 point produced by the wavelength that is one.

E_g等于hc除以λ。当LED的正向偏压受到特定波长的限制时，它实际上是由截止波长λ_c决定的，约为1点1点，由该波长产生。

In order to produce light, the LED requires current. Current flows through it. So you must apply voltage to the LED in order to produce light. And the light intensity is dependent on the current. If you apply larger current, you will get brighter light.

为了产生光，LED需要电流。电流流过它。因此，你必须向LED施加电压才能产生光。而光的强度取决于电流大小。如果你施加更大的电流，就会得到更亮的光。

Different alleles produce different colors. For example, one allele produces blue, and another allele produces yellow. Many alleles produce different colors. Here it shows the allele characteristic. The X-axis is for proportions, while the Y-axis is for colors.

不同的等位基因产生不同的颜色。例如，一个等位基因产生蓝色，另一个等位基因产生黄色。许多等位基因产生不同的颜色。这里展示的是等位基因的特征。X轴表示比例，Y轴表示颜色。

If you apply a larger current, you will get a brighter light. The light intensity is dependent on the current of the LED, so it is a current-dependent device. You must protect the LED by using a resistor connected in series with the LED.

如果施加更大的电流，就会得到更亮的光。LED的光强度取决于通过它的电流，因此它是一种电流依赖型器件。必须使用与LED串联的电阻来保护LED。

The current must be limited. If the current is too high, it exceeds the limit of the LED and can break the LED. So you must use a resistor to protect the LED. The current is usually limited to 5 milliamps or 30 milliamps.

电流必须加以限制。如果电流过高，就会超出LED的额定极限，从而损坏LED。因此必须使用电阻来保护LED。电流通常限制在5毫安或30毫安。

If you want a brighter light, you increase the current, but not larger than 30 milliamperes. The typical current range is from 5 milliamperes to 30 milliamperes. You must limit the current to protect the LED. Never connect the LED directly to the power supply; you must always use a resistor to limit the current.

如果你想要更亮的光，就增大电流，但不要超过30毫安。典型电流范围是5毫安到30毫安。你必须限制电流以保护LED。切勿将LED直接连接到电源上；必须始终使用电阻来限制电流。

The range is from 25 to 30, but typically for now it is 30 degrees. The operating range of the AER is from 120 DC voltage to 200 current voltage. At 2900 K, the value is very low, so there is no current. Therefore, the AER operates from 120 DC voltage to 200 current voltage.

范围是25到30，但目前典型值为30度。AER的工作范围是从120直流电压到200电流电压。在2900 K时，数值非常低，因此没有电流。所以AER的工作范围是从120直流电压到200电流电压。

Here is the example we previously explained of how an AEP should be implemented in a system. When a system is used to target flows to an AEP...

这里是我们之前解释过的一个示例，说明AEP应如何在系统中实现。当系统用于将流定向到AEP时……

If you know the current in the parallel circuit, you can calculate the equivalent resistance. This equivalent resistance is used to replace the parallel circuit. Here is an example.

如果你知道并联电路中的电流，就可以计算等效电阻。这个等效电阻用于替代并联电路。这里有一个例子。

An I2C interface has a voltage drop of two volts. It connects to a five-volt stabilized PC power supply. Since the internal voltage drop is two volts, you must subtract: five minus two gives three volts across the resistor. That three volts is used to limit the current.

I2C接口存在两伏的压降。它连接到一个五伏稳压的PC电源上。由于内部压降为两伏，所以需要用五减去二，得到电阻上的三伏电压。这三伏用于限制电流。

The resistor must be larger than 300 ohms in order to limit the current in the circuit. If you connect the diodes in series with a 1000-ohm resistor, then you can calculate the current flowing through the diodes.

电阻必须大于300欧姆，以限制电路中的电流。如果将二极管与一个1000欧姆的电阻串联，就可以计算流过二极管的电流。

These resistors are connected in series. One of these resistors is used to compute the current flowing through the diodes. There is a break. These LEDs are connected in series, and we use a resistor to protect the LEDs.

这些电阻串联连接。其中一个电阻用于计算流过二极管的电流。此处有一个断路。这些LED串联连接，我们使用一个电阻来保护LED。

LEDs can have different power requirements. If you connect them together, the voltage increases. The last leg increases. If you have many LEDs, the last leg will also increase. That is the reason why...

LED可以有不同的功率需求。如果将它们连接在一起，电压会升高，最后一条支路的电压也会升高。如果你有很多LED，最后一条支路同样会升高。这就是为什么……

A single atom produces very dim light—much darker. However, when many atoms are connected together, the scattered light becomes less dim and the overall brightness increases. If these atoms emit photons of the same color, one atom may produce one photon while another produces zero, yet together they still contribute to the output. When many such atoms of the same color emit simultaneously, the resulting light is much brighter.

单个原子产生的光非常微弱，要暗得多。然而，当许多原子连接在一起时，散射光不再那么暗淡，整体亮度增加。如果这些原子发射相同颜色的光子，一个原子可能产生一个光子而另一个产生零个，但它们共同贡献于输出。当许多相同颜色的原子同时发射时，产生的光要亮得多。

In this case, we have to calculate the total body drop for the water stream A. Here, if 1A needs 2.5 water, but for the total body for stream A is 3.6.

在这种情况下，我们需要计算水流A的总体降。这里，如果1A需要2.5的水，但水流A的总体降为3.6。

The voltage of the resistor is equal to minus the voltage of A; you take one hundred volts. In order to limit the current, you add a resistor to protect the three agents. The patient's device is grounded.

电阻上的电压等于A点电压的负值，取一百伏。为了限制电流，需要串联一个电阻来保护三个元件。患者设备是接地的。

ATP synthase consists of two main components: F1 and Fo. F1 contains three alpha subunits and three beta subunits. Fo is embedded in the membrane and contains a ring of c subunits, known as the c-ring. Protons flow through Fo, driving the rotation of the c-ring. The gamma subunit serves as a central stalk connecting the c-ring to F1. As the c-ring rotates, the gamma subunit rotates within F1, inducing conformational changes in the beta subunits that drive ATP synthesis.

ATP合酶由两个主要组分构成：F1和Fo。F1含有三个α亚基和三个β亚基。Fo嵌入膜中，含有一圈c亚基，称为c环。质子通过Fo流动，驱动c环旋转。γ亚基作为中央柄，将c环与F1连接起来。当c环旋转时，γ亚基在F1内部旋转，诱导β亚基发生构象变化，从而驱动ATP的合成。

A laser requires very little energy; it is an energy-saving device. It produces light that is very coherent. This means you do not need a corner reflector—you produce very pure and coherent light without having to use a reflector.

激光器所需的能量非常少，它是一种节能装置。它产生的光具有高度相干性。这意味着你不需要使用角反射器——你可以直接产生非常纯净且相干的光，而无需借助反射器。

A house takes a very long time. The reversal is initially not so large—it slowly reverses, then suddenly collapses.

一栋房子需要很长时间才能建成。其逆转起初并不显著——先是缓慢逆转，然后突然崩塌。

It is not very difficult. I can do it in a second. It is very small—the size is very small. It can be integrated easily on a PCB. Of course, there are also some difficulties. As for cost, it used to be always expensive, but now it is not expensive anymore.

这并不难，我几秒钟就能完成。它的尺寸非常小，可以很容易地集成在PCB上。当然，也存在一些困难。至于成本，过去它总是很昂贵，但现在已经不贵了。

And the performance depends on the environmental temperature. It must be operated with the correct current. In order to produce the correct current, we must use series resistors or current regulators to protect the LEDs.

其性能取决于环境温度。必须以正确的电流进行驱动。为了产生正确的电流，我们必须使用串联电阻或恒流调节器来保护LED。

That's all for Lecture 9. This is the second last lecture. A brief summary: capacitance is used for storing electrical charge. C is the capacitance, which can be expressed as the charge divided by the voltage applied to the terminals.

以上就是第9讲的全部内容。这是倒数第二讲。简要总结：电容用于储存电荷。C为电容，可表示为电荷除以施加在端子上的电压。

For capacitors connected in parallel, you can add them together to get the equivalent capacitance. If they are connected in series, you use this equation to compute the equivalent capacitance. The energy stored in a capacitor is half of the capacitance times the voltage squared.

对于并联的电容器，可以将它们相加得到等效电容。如果它们是串联的，则使用这个公式来计算等效电容。电容器中储存的能量等于电容的一半乘以电压的平方。

We discussed that the electric field E of a capacitor equals the voltage applied to the capacitor divided by the distance between the two plates. Given S or S₁, we only have one unknown left. That is the formula for this equation. The value of the remaining unknown is one. This question has two parts; I am just asking about the electric field.

我们讨论过，电容器的电场E等于施加在电容器上的电压除以两极板之间的距离。已知S或S₁，我们只剩下一个未知量。这就是该方程的公式。剩余未知量的值为一。这道题有两部分，我这里只问电场。