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Why is analog electronics so hard to learn?


Model electronics must be very tiring for friends lately.

Describe learning process in one sentence:

"The teacher said I didn't get it first time, and I still didn't get it second time, and I still didn't get it third time."

This is how netizens view analog electronics:

It's as hard to understand as a book from heaven.

Model electricity=magic electricity

Analog electronics for bachelors is painful enough, but high-level analog electronics for graduate students is just ecstasy.

Getting started with diodes, triodes and MOS bands; op amps, oscillator circuits and chopper circuits are amazing.

The teacher knows everything in lesson, but can't after lesson.

Learning analog electronics is easy, passing exam is easy, a little hard to use in the beginning, but gets harder after a long time of use.

Analog circuit itself is a very complex subject, and analog circuit means an electronic circuit that processes analog signals. The vast majority of signals in nature are analog signals that have continuous amplitude values, such as beep of a conversation.

Analog circuits can process such signals directly (of course, they must first be converted to electrical signals). For example, power amplifiers can amplify audio signals, and radio stations can send analog audio and video signals.

You could even think of all circuits as being based on analog circuits (even if it's a digital circuit, its basic principle is also based on analog circuits). Its importance is obvious.

Due to rapid development of digital circuits and programmable devices, it has demonstrated many excellent features. Many electronic devices are gradually being digitized, but analog circuitry is still inseparable. Currently, most important device in analog circuit is semiconductor device. The simplest and most widely used semiconductor devices are diodes, triodes, field-effect transistors, and operational amplifiers.

People generally think that analog electronic technology is not easy to master and not as easy to understand as digital electronic technology. Why do many people feel this way?

There are also many problems in explaining some textbooks and materials. You don't get feeling that reading textbooks is like reading heavenly books! Below are some of reasons why analog electronics is hard to learn. Let's see if you've been fooled.

01 High requirements for abstract abilities

Semiconductor technology is clearly different from basic knowledge of electricity that is taught in high school. Some electrical quantities from basic knowledge of electricity are very clear. Think about it, sometimes you don't need to consider them, For example, capacitance connection of a triode cannot be ignored in high frequency circuits, but it can be ignored in low frequency circuits.

For example, analyzing DC equivalent circuit and AC equivalent circuit commonly used in a triode amplifier circuit, analyzing virtual short and virtual open concepts used in an op amp circuit, etc., all require relatively strong abilities to abstract thinking. .understand.

02 Lack of engineering thinking

It is common in analog electronics that one value is much larger than other, or that current and voltage values ​​are approximately equal, and there are empirical values ​​for resistance values​ in some typical circuits. Friends who are starting to learn analog electronic technology may feel a little dizzy. They do not know which situation can be approximated and which cannot be approximated. As for value of experience, they don't know how to get value.

For example, if you want to use a 12 volt zener diode to stabilize output DC voltage of 12 volts, input voltage can be 15, 18 or 24 volts, but which one is more reasonable?

Due to variation in parameters of semiconductor devices, large deviations exist, and components such as resistors and capacitors often have an error of more than ± 5%, and some even more. Therefore, blind pursuit of strict calculations does not make much sense. Therefore, special attention should be paid to teaching approximate calculations and methods for solving engineering problems. It is necessary to integrate theory with practice, strengthen practical capabilities of electronic technology and experimental research capabilities, and develop engineering thinking.

In this situation, you can really gain experience with analysis software for simulation and analysis of real welding circuit tests. To learn analog electronic circuits well, it is very important to think more and do more.

03 No systematic training

Now it is very convenient for everyone to get information via Internet. There is also a lot of knowledge about analog electronic technology on Internet, but a lot of content is copied and copied, and some questions that beginners really want to ask are avoided, and content that is difficult to understand is explained very little or no explanation at all.

It is inconvenient to accept disparate knowledge in this way, and it is inconvenient to study systematically. It is natural to study and study, not knowing what you have learned and what you have not.

Secondly, many problems are not deeply thought out. Some problems may not be thought of by some engineers who have worked for many years. It's just that everyone uses it that way and just follows it.Actually, a deep understanding of these basic issues just might reflect level of an electronics engineer. When you are well versed in a knowledge point, your understanding of that subject will naturally rise to a new level.

04 The knowledge system is huge

The following is an analysis of some of key knowledge about analog electronics. You can see how well you got used to it. If it’s very clear, then at least start with analog electronics. Otherwise, you need to increase accumulation of basic knowledge.

1. What is joint injection, joint installation and joint base? What is difference between them?

2. Current triode amplification effect

There is a collector c, a base b, an emitter e, and two PN junctions: a collector junction and an emitter junction. The collector area is relatively large, base thickness is thin, and carrier concentration is relatively low. The picture below shows an NPN transistor:

When emitter junction is forward biased, charge distribution will change and width of emitter junction will narrow; this is equivalent to opening gate from e to b for electrons. When collector junction is biased in opposite direction, charge distribution will also change, and width of collector junction will increase. This is equivalent to opening a door that prevents electrons from leaving c-level, as shown in animation below:

Level B will be connected to a large resistor RB to limit amount of current Ib, and extra electrons running to b pole will have to pass through collector junction to form current Ic, as shown in animation below:

If base voltage doubles, charge distribution will continue to change, width of emitter junction will become narrower, gate will become wider, and more electrons will go to b-level. As shown in animation below:

Because RB is a large resistor, even if Ib doubles, it will still be very small, so more electrons will pass through collector junction, so Ic will also double. As shown in animation below:

3. Operational amplifier

The signal transmitted and processed by op-amp includes a DC signal, an AC signal, and a composite signal superimposed by AC and DC. And signal is carried out according to "proportional (signed + or -, for example: single-phase ratio or inverse phase ratio)". Not necessarily all "gain", in some cases there may also be attenuation (eg proportional gain or transfer function K=Vo/Vi=-1/10).

Op-amp DC DC indicators include input bias voltage, input bias voltage temperature drift (called input bias voltage temperature drift), input bias current, input bias current, input bias current temperature drift. , Open-loop Differential Mode DC Voltage Gain, Common Mode Rejection Gain, Supply Voltage Rejection Gain, Output Peak Voltage, Maximum Common Mode Input Voltage, Maximum Differential Mode Input Voltage.

AC indicators include open loop bandwidth, unity gain bandwidth, SR slew rate, full power bandwidth, settling time, equivalent input noise voltage, differential mode input impedance, input impedance in common mode, output impedance .

Modeling electronics is hard, but very practical! It can be said that apart from hardware engineers, no matter what position you hold in electronics industry, studying crystal electrodes can become your main competitiveness and open up more opportunities for your career growth. But now I feel that it is difficult because I have not mastered teaching method. In fact, if I study it down to earth and overcome each knowledge point by knowledge point, I will find that this course is not so difficult. Here are some suggestions for you.

First, overcome psychological factors

Psychological success is first step. If you cannot overcome psychological factors, you will find it difficult to persevere along path of learning and fall back easily when you encounter difficulties. not something that I can decide, so let's give up. But if you think that analog electronics is actually not that difficult. Because engineers around you can learn it, then I think I can do it too, so that learning process will be smoother.From a psychological point of view, this is actually a primacy effect.Influence. So you have to believe that you can learn it, as Carnegie said:If you decide to overcome fear, you can overcome almost any fear. Becauseremember, fear has nowhere to hide, except in mind.

Second, keep spirit of exploration

If knowledge of analog electronics really seems like a bible, then you can review study and ask your friends and teachers if you don't understand. For example, first time to study from textbooks, studying most basic knowledge, main goal is to master some methods of problem analysis and a few important conclusions, know how they are made, and learn to master a few classical circuit diagrams.

You need to learn second time by doing it, and this is real study of analog electronics. With practice, you will find that original circuit diagrams in book are purely for theoretical analysis, but for practical implementation, you will need help of other circuits, so you can learn a number of decouplings, insulation, wiring, signal direction, etc., can only comprehend ineffable knowledge. It's a long process, maybe a few years or even more than a decade, which is why my teacher used to say that analog electricity is like Chinese medicine, and digital electricity is like Western medicine.

Third, learn to use various resources around you.

In real work, you will encounter these and other problems. When problems arise, you should first try to solve them yourself. , classmates, forums, these are all resources that should be used correctly. Manufacturer websites now offer samples and evaluation boards, as well as instructional videos and application notes. Take advantage of it. Especially application guide is an artifact to avoid workarounds for students!

Fourth, start in field first and go deeper

Over time, you will find that there are many similar things and you can learn from them by analogy, so that when you study another field, you will not have feeling that you are starting all over again, and this will make students feel myself much more relaxed. The above is my own summary. I hope everyone will take gist and drop dross, and happily study analog electronics together and design successfully!

Finally, analog circuits are a very complex subject requiring much more knowledge than those mentioned above. Learning from textbooks is far from enough, because books are usually introduced on a working basis, which simplifies many tasks that are difficult to understand but need to be taken into account in practice, so gap between actual diagram and book is very large. For example, a triangular wave oscillator built around an analog book op amp will most likely not work when used in a real circuit.

However, basic principle of actual circuit is as described in book. Therefore, design of analog circuits often requires a lot of experience, and there are many things that are difficult to explain and impossible to calculate. Only if you study theoretical foundations, do more practical work and develop your own engineering thinking, will you be able to overcome analogy.