The oscillation frequency of the two quartz crystal oscillator circuits is not the frequency of the crystal. Why?

唯美阿德

The oscillation frequency of the two quartz crystal oscillator circuits is not the frequency of the crystal. Why? [Copy link]

 

As shown in the figure: There are two quartz crystal oscillator circuits. The simulation results show that no matter how high the frequency of the crystal is set, the output signal period is about 40us.

According to the online information in the book, this circuit can output signals from several megabytes to tens of megabytes, which is only related to the resonant frequency of the quartz crystal. 255, 255)]Why is this happening? ? Is there something wrong with the circuit, or is there another reason?

philipchiu

Don't do this kind of boring thing again. If you want to do it, just solder a board to test it. Don't believe in such empty things. I've already said something about you in the previous post. It's a waste of resources to open multiple posts.

maychang

Open another thread on this question? "Is there something wrong with the circuit, or is there another reason?" The circuit itself has a problem, although it cannot be said to be a wrong circuit.

maychang

"According to the online information in the book: this circuit can..." I don't know where you found the circuit. Many books nowadays are copied from other places, such as copying a paragraph here and there from classic textbooks to make an article or even a book. However, any circuit has its purpose and its scope of application. If it exceeds the scope of application, problems may occur. If the circuit is seriously wrong and it can be seen at a glance that it cannot work, such as a power short circuit, then it is fine. Everyone knows that it is wrong and it will not cause much impact. What is feared is that it is specious. It is said that it cannot work, but it can produce oscillation. It is said that it can work normally, but it does not oscillate at the resonant frequency of the quartz crystal. This kind of specious circuit is harmful to people.

maychang

In fact, if the quartz crystal oscillator circuit uses digital circuit chips, it can be very simple, as shown in the following figure , where chip U is one-sixth of a 74HC04, R can be about 1MΩ, C1 and C2 are 20~30pF.

maychang

The circuit on the 5th floor is often seen in the clock circuits of various single-chip microcomputers. If the quartz crystal is replaced with a small capacitor in this circuit, it will never oscillate on its own, but if the quartz crystal is replaced with an inductor, it can oscillate. It can be seen that the quartz crystal is equivalent to an inductor in this circuit. This circuit is often called a Pierce oscillator circuit. If the quartz crystal in this circuit is replaced with an inductor, it is a Pierce oscillator circuit (also often called a three-point capacitor oscillator circuit in textbooks).

唯美阿德

maychang posted on 2018-3-24 15:59 In fact, if the quartz crystal oscillation circuit uses digital circuit chips, it can be very simple, as shown in the following figure, where chip U is one-sixth of a 74HC04, and R can be used...

What does one-sixth of a 74HC04 mean?

唯美阿德

philipchiu posted on 2018-3-24 14:20 Don't do this kind of boring thing anymore. If you want to do it, just solder a board to test it. Don't believe in that kind of empty stuff. I'm already thinking about you in the previous post, and you've opened multiple threads...

The problem must be clarified. Is there no one on the forum who can give a good solution?

唯美阿德

maychang posted on 2018-3-24 15:23 This question, another thread? "Is there a problem with the circuit, or is there another reason?" The circuit itself has a problem, although it cannot be said to be wrong...

The problem has never been solved, then I can only keep asking until someone enlightens me

maychang

Weimei Ade posted on 2018-3-24 19:47 What does one-sixth of a 74HC04 mean?

There are six identical inverters inside the 74HC04 chip, but only one is used now, so it is called one-sixth of a 74HC04.

philipchiu

Weimei Ade posted on 2018-3-24 19:48 The problem must be clarified. Is there no one on the forum who can give a good solution?

Here is a link for your reference https://www.zhihu.com/question/30930577

PowerAnts

I am posting repeatedly. I am sober and going to have a look. . .