TFUM 发表于 2024-7-19 16:40
有可能是示波器或者探头带宽不够

" U, q1 {/ [& o2 ~不会吧，25M的频率，示波器带宽是200MHz的

612星球 发表于 2024-7-19 09:26

: [3 e" A6 ~& U; p+ y1 o師夷之長以制夷！
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The frequency of oscillations is defined by a sharp slope of the electromechanical resonator (crystal), while the gain control is based on dependence of the input on the DC bias voltage - if the DC bias (at C1) is too low to ground or too close to Vcc, the gain is low. The linear gain is highest somewhere in between the ground and power rail.
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The (usually internal) bias resistor R1 plays a crucially important role in the oscillator. Typical value of it in CMOS implementations is about 1 MOhm. Together with C1 it forms a low-pass filter, which integrates the output and provides a variable DC offset depending on slight asymmetry of the output signal, even if the output gets to saturation (rail limiting).
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0 ]2 c: Y. g4 d$ \$ x, p/ ^As result, there could be a variety of signal shapes with more or less non-linear distortion on Xout and Xin, depending on the inverter's raw gain and parameters of the crystal resonator and loading capacitors. With a very low gain and at the verge of self-oscillations, the signals will be nearly sinusoidal, while at higher gain the output will hit the voltage rail and can be nearly rectangular. The art of making Pierce oscillators is to provide some golden trade-off between rectangular output and sinusoidal one, with good stability of the entire circuit to temperature and voltage variations.

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这也有可能和芯片内部的晶振增益、晶振的驱动电流有关系，看看datasheet对这一方面的要求，配置合适的参数

有可能是示波器或者探头带宽不够

612星球 发表于 2024-7-19 09:26

7 O% Q# h' G6 t( R+ Z7 nXIN 引脚的
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