EDA is electronic design automation, which is a new technology in the field of modern electronic engineering. It provides a new design method of circuit system for electronic designers. Mastering EDA technology is a basic condition for the employment of electronic college students. Since 1999, we have applied EDA (mainly EWB, MulTIsim, Protel and other software with virtual experiment functions) to classroom teaching, experiment, course design, graduation design, etc. Many links have achieved good results.

1 The necessity and feasibility of introducing EDA

1.1 The necessity of introducing EDA into the teaching of electronic technology courses

"Electronic Technology Fundamentals" is a very important professional basic course, and it is also the main course of electronic majors. The teaching effect of this course directly affects the teaching of post-reading courses. At the same time, the course is both highly theoretical and practical. It is not easy to learn this course, especially analog electronic technology. Only with good teaching methods and means, with a certain number of experiments (including demonstration experiments in classroom teaching) and practical links, can students comprehend, understand, and master the content of the course, so that they can master, apply what they have learned, and receive good teaching effect. However, in the teaching of electronic technology courses, there have always been problems such as single teaching means, rigid teaching methods, and insufficient experimental resources, resulting in unsatisfactory teaching results. After several years of exploration and practice, we realized that introducing EDA into the teaching of electronic technology courses is an effective method to solve the above problems.

1.2 The feasibility of introducing EDA into the teaching of electronic technology courses

First, in recent years, the teaching conditions of colleges and universities have generally improved, and multimedia teaching has been widely used in classroom teaching, and the hardware conditions for using computer simulation to carry out demonstration experiments are available. In classroom teaching, teachers can use EDA software to carry out simulation experiment demonstrations, which solves the problem of difficult demonstration experiments in electronic technology courses in the past. When specific circuits are involved in the teaching process, virtual instruments in the software (such as multimeters, oscilloscopes, Bode plotters, digital displays) can be used, and multimedia synchronous demonstrations are convenient and intuitive, which can greatly improve the quality of classroom teaching.

Second, with the rapid development of computer technology, various laboratories of electronic majors have been equipped with microcomputers, and have the hardware conditions to open EDA simulation experiments. As far as our school is concerned, there are many laboratories equipped with microcomputers in the major of electronic information, such as microcomputer principle, network technology, EDA technology, digital signal processing, and single-chip microcomputer. As long as EWB, MulTIsim, Protel and other EDA software are installed on these microcomputers, the design and simulation of electronic circuits can be carried out.

Third, with the popularization of microcomputers, many students already have personal computers. If EWB, MulTIsim, Protel and other software are installed, it is equivalent to having a personal "multi-functional electronic laboratory. Students can easily verify the theoretical knowledge learned in the classroom through virtual experiments after class! You can also carry out other design tasks at any time." experiment.

2 Application research of EDA in classroom and experimental teaching of electronic technology courses

2.1 Introduce EDA into the classroom, conduct demonstration experiments, and improve the effect of classroom teaching

In the past, there was a disconnect between theoretical classes and experimental classes. Theoretical teaching is all about some boring principle analysis, formula derivation, and it is difficult for students to understand in teaching. In order to improve the teaching effect, it is necessary to cooperate with demonstration experiments. However, in doing so, one is to prepare a demonstration experiment, which requires a special teaching board, which takes a lot of time; the other is to move a variety of instruments to the classroom, which is inconvenient to use; the third is to demonstrate the operation process, which takes up too much time and affects teaching. schedule. Therefore, in actual teaching, there is basically no teacher's use, and it can only be purely theoretical explanation. Obviously, this teaching method will not work very well.

Now we have introduced the virtual experiment functions of circuit design and simulation software such as EWB and Pspice into the classroom, updated the teaching methods and changed the traditional teaching methods. When analyzing circuits, teachers can use virtual instruments in the software as needed, use multimedia synchronous demonstrations, display "experimental" results, and visualize and visualize some abstract concepts, such as teaching the effect of negative feedback on circuit performance in analog circuits. When it is affected, we select the emitter bias circuit, set the emitter resistor with and without bypass capacitor, compare and explain the influence of AC negative feedback on the magnification and distortion, and use an oscilloscope and a Bode plotter to display the waveform distortion and The change of magnification is very simple to operate, and the result is very intuitive. Another example is when teaching the design of a three-bit binary asynchronous counter with a rising edge D flip-flop in a digital circuit, it can be seen from theoretical analysis that the clock terminal of the subsequent stage flip-flop is connected to the Q terminal of the previous stage flip-flop to form a subtraction counter; The clock terminal is changed to be connected to the non-terminal of the previous stage Q, and the circuit becomes an adding counter. After the theoretical analysis, we call out the circuit connected with EWB software from the courseware and verify two different counting situations with the decoding display, the result is clear at a glance. In this way, the "experiment" is brought into the classroom, the teaching mode is lively and lively, the students maintain a high interest in learning from beginning to end, deepen their understanding and memory, and effectively improve the effect of classroom teaching.

2.2 Set up simulation experiments, reform experimental teaching methods, and improve the quality of experimental teaching

The electronic technology course is a highly practical course, and theoretical study must be closely combined with practice. In the past, the practical part was mainly experimental courses, and the experimental content was mostly confirmatory experiments, and there were few designed and comprehensive experiments. As far as the confirmatory experiment is concerned, the experimental box is generally used and the operation is performed step by step according to the experimental instruction book. Design and comprehensive experiments are difficult for students, and there are many errors in the designed circuits. Moreover, because the opening and management of the laboratory cannot keep up with the requirements, students are often required to complete tasks within the limited opening hours of the laboratory. , so the experimental success rate is low. Therefore, teachers usually give reference circuits. Strictly speaking, this practice cannot be regarded as a design or comprehensive experiment, and cannot play a role in cultivating students' innovative ability. Therefore, in order to improve the teaching quality of electronic technology courses, it is necessary to reform the teaching of experimental courses. How to reform? It is a question that needs to be seriously explored and studied.

After several years of exploration and practice, we have received good results in the reform of experimental courses. The method is: using EWB, Pspice and other circuit design and simulation software, in the electronic technology experiment course, select representative topics, set up a certain proportion of virtual experiments, and play the advantages of time-saving, high-efficiency, safety and economy of virtual experiments; It solves the problems that in the past, the experimental class completely relied on the experimental instruments, and the electronic components were damaged and the maintenance of the experimental instruments was not timely. In addition, because the virtual experiment is not limited by hardware conditions, students can propose various design schemes, change circuit parameters at any time during the experiment, study the relationship between circuit performance indicators and parameters, and can quickly obtain simulation results and find problems in time. To solve it, which greatly improves the students' ability to analyze and solve problems, and stimulate their thirst for knowledge and innovation. This is a kind of research study, which cannot be done by traditional physical experiments. In this sense, traditional physical experiments appear mechanical and rigid. Simulation experiment has the characteristics of research study, which is of great help to improve students' electronic circuit design level and cultivate innovation ability. For physical experiments, students can also conduct EDA simulation preview. Before the experiment, through simulation, on the basis of understanding the experimental principle, do physical experiments, so that the virtual and real experiments are combined, which greatly improves the quality of experimental teaching.

3 Application research of EAD in improving experiments, curriculum design, graduation design and other practical links

Due to the limitations of hardware, equipment, funds, venues and other hardware conditions, traditional experimental and practical teaching, the planned class hours and topics are too few, which cannot meet the requirements of talent training. Employers now have higher and higher requirements for students' innovative thinking ability and practical ability. Therefore, we must pay attention to design, comprehensive experiments, curriculum design, graduation design and other practical links, so as to cultivate students' innovative thinking ability and practical ability. Based on the above situation, we have carried out the following exploration and practice:

3.1 The exploration and practice of introducing EDA into improved experiments

In electronic technology experiments, the proportion of confirmatory experiments in the past was high, which was not conducive to cultivating students' innovative thinking ability. Now we have reduced the proportion of confirmatory experiments and increased the content of improved experiments. This is mainly due to the fact that EDA provides a good operating platform for design and comprehensive experiments, because it better solves the problems that were limited due to insufficient components and instruments in the past design and comprehensive experiments. For example, we are in the analog circuit experiment and the digital circuit experiment link. When setting up design experiments such as DC regulated power supply, audio amplifier, digital clock, car taillight control circuit, etc., let students first propose a design plan, design the circuit by themselves and simulate it. Get the simulation results. On this basis, we provide students with components and measuring instruments, so that students' designs can be turned into real objects, so that students take less detours, and the loss of components is also greatly reduced. This move not only improves the students' innovative thinking ability but also enhances the students' hands-on ability. On this basis, we also organized extracurricular electronic production activities in a timely manner, and introduced EWB simulation experiments into the second classroom, so that the electronic design and production capabilities of the students participating in the activities were further improved.

3.2 The exploration and practice of introducing EDA into curriculum design and graduation design

Due to the application of EDA simulation software in many previous links, in course design and graduation design, most students can use EWB, which has an intuitive interface, easy to learn and use, as a circuit design method. When relevant circuits appear, they can all be designed using EWB software. After passing the virtual experiment, the actual production is carried out. This method of combining virtual and real not only brings into play the advantages of efficient and economical virtual experiments, but also cultivates students' ability to analyze and solve problems, which greatly improves the quality of design. According to preliminary statistics, 50% of the 2001 students applied EDA simulation software to assist their graduation design, and 60% of the 2002 students used EDA simulation software to assist their graduation design. It can be believed that through our unremitting efforts, EDA simulation software will be popularized and popularized in the teaching of electronic technology courses, and more and more students will use EDA simulation software to assist course design and graduation design, thereby greatly improving students' application of electronic technology. technical capabilities.

4 Several issues that should be paid attention to in virtual experiments

4.1 Recognize the inadequacies of virtual experiments

Like many things, virtual experimentation has its upsides and its downsides. If physical experiments are completely replaced by virtual experiments, then:

1. Weakening students' cognition of real components. Because in the simulation experiment, the components they contact are only some circuit symbols, and the actual electronic components have great differences in packaging form, manufacturing materials, size and appearance, and these differences are in the simulation. It is difficult to show in experiments.

2. Weakening students' proficiency in mastering the operation of instruments. Because real experimental instruments need to be used repeatedly before they can be mastered. If you simply use computers for simulation, it will inevitably weaken the training of actual instrument operation skills, resulting in students ignoring the operating specifications, affecting the formation of good scientific practice habits, reducing the Students' ability to solve practical problems.

3. Weakens students' layout ability for actual electronic product design. The performance of an actual electronic product is related to many factors such as the layout of components and the skills of wiring. What you see in the simulation experiment is only the circuit schematic diagram, and the students have no access to the training of component layout, wiring skills, etc., let alone the accumulation of experience in this area.

In addition, the types of components in the simulation software are limited, and not all components can be found in the simulation library, which also restricts its application range. Therefore, it is impossible and impossible to completely replace physical experiments with simulation experiments.

4.2 Combining the virtual and the real to complement each other

On the one hand, we should emphasize the auxiliary role of simulation experiments in teaching, and at the same time, we should also recognize the importance of practical ability. The two must be complementary and organically combined, and simulation cannot replace all practical training. How to use the simulation experiment reasonably is a topic we need to explore and study continuously. Our approach is:

1. Reasonable arrangement of simulation experiment class hours. Simulation experiments only account for less than 1/3 of the total experimental class hours. The application of 789 to conduct virtual experiments is mainly based on students' own computer experiments after class.

2. Open electronic design and simulation experiment elective courses, cooperate with analog circuit, digital circuit, high-frequency circuit textbooks, carefully write simulation experiment topics, and provide students with scientific and reasonable simulation experiment topics. Since 2001, we have opened the elective course of electronic design and simulation experiment by taking the opportunity of training the contestants to participate in the National Undergraduate Electronic Design Competition. In the past few years, the students who participated in the elective courses have obviously enhanced their electronic technology application ability.

3. For the exploratory and research experiments designed by the students, first let the students conduct virtual experiments to verify them, and then use the form of the second classroom as much as possible to make their virtual experiments into tangible objects.

In short, through several years of exploration, we have applied EDA to the whole process of electronic technology course teaching, and have received good teaching results, which has comprehensively improved the teaching quality of electronic technology courses.
Responsible editor: tzh

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