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Gao Jian is completely an educating tone, Liu Chen took a breath, and said in his heart, it's been a long time since anyone dared to give me guidance techniques, then listen to it, if you don't say it well, I'll guide you.

"I ask you, how do you turn the negative half of a sine waveform into a positive half cycle? What is this called a transformation?"

"Well, this is called ......" Huang Kai pretended to think, and in the middle of his head, Zhang Jun said: "It's a reversal, right?"

"Doesn't that turn the original positive signal into negative again? What is the difference between it and the original signal? I don't understand this simplicity, there is this transformation in elementary school mathematics, the absolute value! The circuit that realizes this function is called the absolute value circuit, I ask you, how many ways are there to process the absolute value of the signal?" Gao Jian was very popular.

Now the two of them don't know at all, it's okay to read the book to cope with the exam, theory and practice can't be combined at all, and the two of them belong to the basic electronic components and can't tell the difference.

The two squeaked and whined.

Gao Jian was furious: "Have you learned power electronics technology in vain?"

The two of them still didn't keep up with their thinking, their faces turned a little red, and they were reprimanded quite miserably.

"Heh, Dr. Gao, I can't remember it now, just tell us about it. ”

"yes, I don't remember exactly. ”

Gao Jianzhi asked: "Is there a bridge circuit in the rectifier circuit?"

"There's this. ”

"Yes. ”

The two became echo worms.

"What happens if four diodes are connected in two by two and then connected in parallel, depending on the unidirectional conductivity of the diodes?"

"Hmmm......"

"Forehead ......"

I can't keep up with the train of thought at all.

Gao Jian's tone was even more severe, "If the signal input from both ends is taken out from the middle connection point, is it equivalent to doing absolute value processing?"

You two are really stupid pigs! This sentence was suffocated, and the white face was suffocated.

Hearing him say this, the two nodded yes again and again.

Gao Jian snorted, glanced at Liu Chen and Han Jiaren again, his gaze stayed on Liu Chen, condescending, full of superiority in showing off his skills, "Do you understand?"

Obviously, he was very upset about not asking just now.

Liu Chen nodded and asked: "Understand a little, the signal is a weak signal, and it is different from the rectifier structure commonly used in strong electricity in switching power supplies, and the bridge circuit composed of four diodes does have the effect of absolute value processing." ”

"I don't see you really knowing. ”

Not to understand a little, Liu Chen said with a smile: "But Senior Brother Gao, have you ever thought that the one-way conduction of the diode actually requires a starting current, this starting value is very small, and it can be ignored when dealing with strong electricity, but the signal is weak, so that when crossing the zero point, it will be distorted and the signal will be distorted." ”

Liu Chen was able to say this truth, which surprised Gao Jian, he actually questioned his technology in person, more anger, his temperament was already arrogant, not to mention that today he encountered something that made him extremely frustrated and resentful, his temper could not be controlled at all, and he sneered and said: "Of course I know, it's not simple, didn't I add an operational amplifier circuit in front of the bridge circuit? Do you know what it does?"

"Using the characteristics of the op amp short and broken, the signal strength is enhanced without changing the original signal pattern, and the passive signal becomes an active signal. ”

Gao Jian stared at him with blazing eyes, he didn't expect this kid to be able to answer, and asked, "What do you change to achieve the purpose of enhancing the signal?"

I am afraid that ordinary people will not be able to answer this question, and few people will delve into it.

Liu Chen smiled, this is not difficult for me, said: "In fact, it is equivalent to changing the input impedance of the signal", and asked rhetorically: "This processing method is indeed feasible, but why not directly design an absolute circuit composed of an operational amplifier and diodes? ”

Liu Chen answered it completely, and also raised a new question, Gao Jian said angrily: "This is the most practical and effective circuit, like the method of separating the positive and negative semi-circular signals first, and then using the operational amplifier circuit to reverse one side, and then synthesizing them together, is even more unconcise and impractical, and requires the use of at least three operational amplifiers, and the cost is also high!"

He couldn't bear any technical questioning, and he almost ran out of anger, as if Liu Chen was the disgusting man who hugged the girl he pursued early in the morning and kissed wildly, eager to grab Liu Chen's collar and punch a few fists.

Hey, the undergraduates are busy studying, the master's are busy with scientific research, and I'm going to study for a doctorate, so I feel lonely and lonely, and I coincidentally met a very beautiful girl, and I can talk very well.

The blow is not insignificant.

Liu Chen touched his chin, pretending to be in thought, saying it directly would embarrass him too much, but it was just a frustration of his sharpness, not a blow.

Gao Jian looked at his appearance, and said in his heart, I don't know where I saw this piece of knowledge, what does a new kid know, how many circuit boards have I designed, how many switching power supplies have I debugged? Compared with me, it is still too far behind!

He couldn't stand any technical questioning, and said angrily.

Liu Chen was still thinking.

Gao Jian said aggressively: "Haven't you come up with it yet?

Huang Kai said slowly: "Brother Jian's absolute value circuit is very practical and very good!"

Zhang Jun also said: "That's it, Dr. Gao is a hardware expert, you can't be wrong!"

About five minutes passed.

Liu Chen found a pen and paper, quickly drew three absolute value processing circuits composed of operational amplifiers and diodes, and said calmly: "I can only think of three circuits for a while, and it is not feasible for you to try it." ”

Gao Jian snorted and took it over and looked at it, frowning, and Huang Kai and Zhang Jun also looked at it.

"I still have to leave beforehand, next time I will come to learn more from Senior Brother Gao and ask for more advice. "Liu Chen has been delayed here for a long time, it's time to go to Professor Chang.

In Gao Jian's eyes, this is afraid of being exposed and fleeing, can this casually drawn circuit be used?

It's just funny! Is a stable circuit so easy to design? These three drawings even have the parameters of the components marked.

It's good for a graduate student to be able to understand some complex circuits, but Huang Kai and Zhang Jun can't understand the waste materials.

Gao Jian couldn't see whether it would work or not, the operational amplifier would increase the complexity of the analysis of the circuit, and it was difficult to see the effect at once, seeing that Liu Chen was leaving, he shouted: "Wait a minute!

Liu Chen shook his head slightly and stopped.

Sure enough, he is a technical master, Gao Jian is proficient in various tools, opens the Psim on the computer and quickly makes a simulation model according to the first picture, adding a sine wave signal source in front, adding a detection point to the output, and clicking and dragging his fingers on the mouse rapidly, very skillful, dazzling to see a few people, Han Jia people are admired.

Everyone watched, waiting for the result. (To be continued.) )