Posted on Categories:微电子芯片原理, 物理代写

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## 物理代写|微电子芯片原理代写Microelectronics代考|pn JUNCTION

We begin our study of semiconductor devices with the $p n$ junction for three reasons. (1) The device finds application in many electronic systems, e.g., in adaptors that charge the batteries of cellphones. (2) The $p n$ junction is among the simplest semiconductor devices, thus providing a good entry point into the study of the operation of such complex structures as transistors.

(3) The pn junction also serves as part of transistors. We also use the term “diode” to refer to $p n$ junctions.

We have thus far seen that doping produces free electrons or holes in a semiconductor, and an electric field or a concentration gradient leads to the movement of these charge carriers. An interesting situation arises if we introduce $n$-type and $p$-type dopants into two adjacent sections of a piece of semiconductor. Depicted in Fig. $2.16$ and called a “pn junction,” this structure plays a fundamental role in many semiconductor devices. The $p$ and $n$ sides are called the “anode” and the “cathode,” respectively.

## 物理代写|微电子芯片原理代写Microelectronics代考|pn Junction in Equilibrium

Let us first study the $p n$ junction with no external connections, i.e., the terminals are open and no voltage is applied across the device. We say the junction is in “equilibrium.” While seemingly of no practical value, this condition provides insights that prove useful in understanding the operation under nonequilibrium as well.

We begin by examining the interface between the $n$ and $p$ sections, recognizing that one side contains a large excess of holes and the other, a large excess of electrons. The sharp concentration gradient for both electrons and holes across the junction leads to two large diffusion currents: electrons flow from the $n$ side to the $p$ side, and holes flow in the opposite direction. Since we must deal with both electron and hole concentrations on each side of the junction, we introduce the notations shown in Fig. 2.18.

The diffusion currents transport a great deal of charge from each side to the other, but they must eventually decay to zero. This is because if the terminals are left open (equilibrium condition), the device cannot carry a net current indefinitely.

We must now answer an important question: what stops the diffusion currents? We may postulate that the currents stop after enough free carriers have moved across the junction so as to equalize the concentrations on the two sides. However, another effect dominates the situation and stops the diffusion currents well before this point is reached.

To understand this effect, we recognize that for every electron that departs from the $n$ side, a positive ion is left behind, i.e., the junction evolves with time as conceptually shown in Fig. 2.19. In this illustration, the junction is suddenly formed at $t=0$, and the diffusion currents continue to expose more ions as time progresses. Consequently, the immediate vicinity of the junction is depleted of free carriers and hence called the “depletion region.”

## 物理代写|微电子芯片原理代写Microelectronics代考|pn JUNCTION

.

pn结也是晶体管的一部分。我们也使用术语“二极管”来指代$p n$结

.

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

Posted on Categories:微电子芯片原理, 物理代写

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## 物理代写|微电子芯片原理代写Microelectronics代考|Digital Camera

Another consumer product that, by virtue of “going electronic,” has dramatically changed our habits and routines is the digital camera. With traditional cameras, we received no immediate feedback on the quality of the picture that was taken, we were very careful in selecting and shooting scenes to avoid wasting frames, we needed to carry bulky rolls of film, and we would obtain the final result only in printed form. With digital cameras, on the other hand, we have resolved these issues and enjoy many other features that only electronic processing can provide, e.g., transmission of pictures through cellphones or ability to retouch or alter pictures by computers. In this section, we study the operation of the digital camera.

The “front end” of the camera must convert light to electricity, a task performed by an array (matrix) of “pixels.” Each pixel consists of an electronic device (a “photodiode”) that produces a current proportional to the intensity of the light that it receives. As illustrated in Fig. 1.5(a), this current flows through a capacitance, $C_L$, for a certain period of time, thereby developing a proportional voltage across it. Each pixel thus provides a voltage proportional to the “local” light density.

Now consider a camera with, say, $6.25$ million pixels arranged in a $2500 \times 2500$ array [Fig. 1.5(b)]. How is the output voltage of each pixel sensed and processed? If each pixel contains its own electronic circuitry, the overall array occupies a very large area, raising the cost and the power dissipation considerably. We must therefore “time-share” the signal processing circuits among pixels. To this end, we follow the circuit of Fig. 1.5(a) with a simple, compact amplifier and a switch (within the pixel) [Fig. 1.5(c)]. Now, we connect a wire to the outputs of all 2500 pixels in a “column,” turn on only one switch at a time, and apply the corresponding voltage to the “signal processing” block outside the column.

## 物理代写|微电子芯片原理代写Microelectronics代考|Analog Versus Digital

Amplifiers and ADCs are examples of analog functions, circuits that must process each point on a waveform (e.g., a voice signal) with great care to avoid effects such as noise and “distortion.” By contrast, digital circuits deal with binary levels (ONEs and ZEROs) and, evidently, contain no analog functions. The reader may then say, “I have no intention of working for a cellphone or camera manufacturer and, therefore, need not learn about analog circuits.” In fact, with digital communications, digital signal processors, and every other function becoming digital, is there any future for analog design?

Well, some of the assumptions in the above statements are incorrect. First, not every function can be realized digitally. The architectures of Figs. $1.3$ and $1.4$ must employ lownoise and low-power amplifiers, oscillators, and multipliers regardless of whether the actual communication is in analog or digital form. For example, a 20- $\mu \mathrm{V}$ signal (analog or digital) received by the antenna cannot be directly applied to a digital gate. Similarly, the video signal collectively captured by the pixels in a digital camera must be processed with low noise and distortion before it appears in the digital domain.

Second, digital circuits require analog expertise as the speed increases. Figure $1.8$ exemplifies this point by illustrating two binary data waveforms, one at $100 \mathrm{Mb} / \mathrm{s}$ and another at $1 \mathrm{~Gb} / \mathrm{s}$. The finite risetime and falltime of the latter raises many issues in the operation of gates, flipflops, and other digital circuits, necessitating great attention to each point on the waveform.

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

Posted on Categories:微电子芯片原理, 物理代写

## avatest™帮您通过考试

avatest™的各个学科专家已帮了学生顺利通过达上千场考试。我们保证您快速准时完成各时长和类型的考试，包括in class、take home、online、proctor。写手整理各样的资源来或按照您学校的资料教您，创造模拟试题，提供所有的问题例子，以保证您在真实考试中取得的通过率是85%以上。如果您有即将到来的每周、季考、期中或期末考试，我们都能帮助您！

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## 物理代写|微电子芯片原理代写Microelectronics代考|Analysis versus Synthesis

Analysis versus Synthesis Let us consider the background of the students entering a microelectronics course. They can write KVLs and KCLs efficiently. They have also seen numerous “random” RLC circuits; i.e., to these students, all RLC circuits look the same, and it is unclear how they came about. On the other hand, an essential objective in teaching microelectronics is to develop specific circuit topologies that provide certain characteristics. We must therefore change the students’ mentality from “Here’s a circuit that you may never see again in your life. Analyze it!” to “We face the following problem and we must create (synthesize) a circuit that solves the problem.” We can then begin with the simplest topology, identify its shortcomings, and continue to modify it until we arrive at an acceptable solution. This step-by-step synthesis approach (a) illustrates the role of each device in the circuit, (b) establishes a “design-oriented” mentality, and (c) engages the students’ intellect and interest.

Analysis by Inspection In their journey through microelectronics, students face increasingly more complex circuits, eventually reaching a point where blindly writing KVLs and KCLs becomes extremely inefficient and even prohibitive. In one of my first few lectures, I show the internal circuit of a complex op amp and ask, “Can we analyze the behavior of this circuit by simply writing node or mesh equations?” It is therefore important to instill in them the concept of “analysis by inspection.” My approach consists of two steps. (1) For each simple circuit, formulate the properties in an intuitive language; e.g., “the voltage gain of a common-source stage is given by the load resistance divided by $1 / g_m$ plus the resistance tied from the source to ground.” (2) Map complex circuits to one or more topologies studied in step (1).

In addition to efficiency, analysis by inspection also provides great intuition. As we cover various examples, I emphasize to the students that the results thus obtained reveal the circuit’s dependencies much more clearly than if we simply write KVLs and KCLs without mapping.

NWhat If?” Adventures An interesting method of reinforcing a circuit’s properties is to ask a question like, “What if we tie this device between nodes $C$ and $D$ rather than between nodes $A$ and $B$ ?” In fact, students themselves often raise similar questions. My answer to them is “Don’t be afraid! The circuit doesn’t bite if you change it like this. So go ahead and analyze it in its new form.”

For simple circuits, the students can be encouraged to consider several possible modifications and determine the resulting behavior. Consequently, the students feel much more comfortable with the original topology and understand why it is the only acceptable solution (if that is the case).

Numeric versus Symbolic Calculations In the design of examples, homeworks, and exams, the instructor must decide between numeric and symbolic calculations. The students may, of course, prefer the former type as it simply requires finding the corresponding equation and plugging in the numbers.

What is the value in numeric calculations? In my opinion, they may serve one of two purposes: (1) make the students comfortable with the results recently obtained, or (2) give the students a feel for the typical values encountered in practice. As such, numeric calculations play a limited role in teaching and reinforcing concepts.

Symbolic calculations, on the other hand, can offer insight into the behavior of the circuit by revealing dependencies, trends, and limits. Also, the results thus obtained can be utilized in more complex examples.

## 物理代写|微电子芯片原理代写Microelectronics代考|“如果?”冒险

nif ?”强化电路特性的一个有趣方法是问这样一个问题:“如果我们把这个设备连接在节点$C$和$D$之间，而不是节点$A$和$B$之间会怎样?”我对他们的回答是:“不要害怕!如果你像这样改变电路就不会咬人了。所以继续分析它的新形式。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。