Dr. Gao Kai is completely instructive.

"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 Jin pretended to think, and in the middle of his head, Liang Shen said: "It's the opposite, right?" ”

"Doesn't that turn the original positive signal into negative again? What is the difference from the original signal? I don't understand it so simple, there is this transformation in elementary school mathematics, absolutely worth! The circuit that implements this function is called an absolute value circuit, and I ask you, how many ways are there to process the absolute value of the signal? "Dr. Gao is very hot.

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 Bo 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.

Especially Liang Shen, in front of Liu Ze, it was very embarrassing.

"Heh, Dr. Gao, I can't remember it for a while, you can tell us about it."

"yes, I don't remember exactly."

Dr. Gao 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 Kai's tone was even more severe, "The signal input from both ends and then taken out from the middle connection point, is it equivalent to doing absolute value processing?" ”

You two are stupid pigs! This sentence was suffocated, and her fair face was flushed.

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

Gao Kai snorted, glanced at Liu Ze and Lu Jiaren again, his eyes stayed on Liu Ze, condescending, full of superiority in showing off skills, "Do you understand?" ”

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

Liu Ze nodded and asked: "Understand a little, the signal is a weak signal, which 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 that you really know a little bit as a sophomore."

Don't just understand a little, Liu Ze said: "But Senior Brother Gao, have you ever thought that the one-way conduction of the diode actually requires a starting current, which is very small and negligible when dealing with strong electricity, but the signal is weak, so that it will be distorted and the signal will be distorted when crossing the zero point." ”

Liu Ze was able to say this truth, which surprised Gao Kai, and even questioned his technology in person, more angry, his temperament was already arrogant, not to mention that today he encountered something that made him extremely frustrated and resentful, his temper was not controllable 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 vanity and disconnection to enhance the signal strength without changing the original signal pattern, the passive signal becomes an active signal."

Gao Kai stared at him with blazing eyes, he didn't expect this kid to be able to answer, and asked, "By changing what 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 Zedao: "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 value circuit composed of an operational amplifier and a diode?" Using four diodes to make a bridge is a bit too bulky. ”

Liu Ze answered completely, and also raised a new question, Gao Kai said angrily: "This is the most practical and effective circuit, like the kind of method that separates the positive and negative semi-circular signals first, and then uses the operational amplifier circuit to reverse one side, and then synthesizes them together, which 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 away in anger, as if Liu Ze was the disgusting man who hugged the girl he pursued early in the morning and kissed wildly, eager to grab Liu Ze'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 Ze touched his chin, in thought.

Gao Kai looked at his appearance and said in his heart, I don't know where I saw this piece of knowledge, what does a sophomore know, how many circuit boards have I designed? How many switching power supplies have you debugged? It's still too far from me!

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

Liu Ze was still thinking.

Gao Kai was aggressive: "Haven't you figured it out yet?" Or is there no idea at all? ”

Huang Jin said softly: "Brother Kai's absolute value circuit is very practical and very good!" ”

Liang Shen also said: "That's right, Dr. Gao is a hardware expert, you can't be wrong!" ”

About five minutes passed.

Liu Ze 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, you can try it or not." ”

Gao Kai snorted and took it over and looked at it, frowning, and Huang Jin and Liang Shen 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 Ze made an appointment for a physics experiment.

In Gao Kai's eyes, this is afraid of being exposed and fleeing, can this casually drawn circuit work?

It's hilarious! Is a stable structure circuit so well designed? All 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 Jin and Liang Shen can't understand these two waste materials.

Gao Kai 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 Ze was leaving, he shouted: "Wait a minute!" Whether it can be used or not, take Psim to do a simulation to find out! ”

Liu Ze shook his head slightly and stopped.

Sure enough, he is a technical master, Gao Kai 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, Lu Jiaren is admired.

Everyone watched, waiting for the result.

Dou Bi also stretched out his head to look, and couldn't see what these three circuits were for, two operational amplifiers with resistors, capacitors, and diodes, and he was dizzy when he looked at it, and couldn't help but say: "Is this circuit useful?" It looks like that. ”

Huang Jin smiled and said: "Senior sister, you also said that 'looking' is okay, this structure is so simple, it looks good enough!" ”

Liu Ze didn't argue either, since Gao Kai would use PSIM, he would soon tell.

Lu Jiaren was next to him, quietly gave a thumbs up, and said with a smile: "Dude, it's pretty good!" I think you can. ”

It was done, in less than ten minutes.

Huang Jin admired: "Dr. Gao, you are too good, you can do anything." ”

Gao Kai ignored him, his hand holding the mouse was a little nervous, this kid just got to the point in a few questions, shouldn't this circuit really be able to deal with absolute value, it is indeed much better than an operational amplifier plus bridge circuit!

Senior Sister Doudou also came over to see the excitement and said, "What's the matter, is it okay?" ”

Gao Kai clicked the mouse very hard, the simulation runs, there is no error information, and there is no error in the circuit, so what about the function? Tremblingly, he double-clicked on the observation point, and his face suddenly changed.

It clearly shows that the negative half cycle of the sine wave is all flipped up, and the absolute value is successfully processed!

Liang Shen exclaimed: "I'm grass, this circuit can really be used." ”

Gao Kai touched his chin and didn't speak, staring closely at the circuit on the simulation interface, his face a little tight and hot.

This kid designed a circuit that was even smarter than he did! I also drew 3 of them at once! He has always boasted of being a master of analog circuit technology, and it is difficult for him to accept.

Immediately, the other two graphs were also simulated, and the results were clearly displayed, and the absolute value processing was indeed realized!

Sister Doudou didn't understand it at all after watching it for a long time, and said hurriedly: "What's wrong, what's wrong, what does it mean, how can it be used?" ”

The other three didn't pay attention to her, and they all knew that it was useless to explain to her, this sister's hardware level is the lowest, I'm afraid that the operational amplifier circuit will not be analyzed, and I don't know what the operational amplifier is!

Gao Kai said angrily with some shame: "A simple analog circuit design is not a big deal. ”

As he spoke, he threw away his sleeves, he felt a fire in his heart, and if he stayed any longer, he had to break out and smash things.

Liu Ze rushed to the experimental class, and Lu Jiaren followed, admiring Liu Ze along the way, "Senior brother, you have only learned circuits, analog and digital electricity, power electronics, and electricity drag in your sophomore year, then you must have been in the laboratory all day long, and your freshman year has become your senior year of high school." ”

He chattered non-stop, "Actually, I also thought before, if I can maintain the efficiency of high school in college, how awesome it should be, but unfortunately, there are too many distractions in college, everyone participates in clubs, in order to avoid high scores and low ability, we have to participate too, everyone is in love, we have to try to talk about it, and we have to delay a lot of time for everything......"

"Senior brother, I still have something to do, I really have to go first, let's talk later."

Liu Ze left quickly, Lu Jiaren looked at his distant back, a little dazed, sighed for a while, and said: "Hey, why is it getting harder and harder to focus on one thing, now I finally know why those guys who once dreamed of the sky have become mediocre step by step, life, step by step has consumed you, buddy, I hope you can keep it all the time." ”