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Hello everyone, in this lesson we will talk about the types and characteristics of crystal oscillators

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Crystal oscillators can be divided into active crystal oscillators and passive crystal oscillators.

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Most of the crystal oscillators used in the motherboard are passive crystal oscillators

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The passive crystal oscillator cannot start up by itself,

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and needs the cooperation of an external circuit to output the clock frequency

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Passive crystal oscillators are generally divided into two-legged and four-legged

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Among them, two pins of the four-legged crystal oscillator are grounded,

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and the other two pins can send out waveforms.

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For example, in the picture on the right, pins 1 and 3 emit waveforms,

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and pins 2 and 4 are grounded.

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Another feature of the passive crystal oscillator is that

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the two clock output pins will each be connected to a resonant capacitor for resonance

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For example, the following two figures

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They both have two white resonant capacitors

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If there is a problem with the resonant capacitor of the passive crystal oscillator,

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it will not output the clock normally

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Next, let's look at the active crystal oscillator

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Active crystal oscillators are rarely used in circuits

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The active crystal oscillator can start to vibrate as long as there is power supply,

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no external circuit is needed, and there is no resonant capacitor

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Active crystal oscillators generally have 4 pins, power supply pins,

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ground pins, clock output pins and an empty pin

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The active crystal oscillator has only one pin that can output the clock

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The passive crystal oscillator has two pins that can output the clock