Do crystal resonator circuits have positive and negative poles
Crystal oscillators are mainly divided into two categories: passive crystal oscillators and active crystal oscillators. Active crystal oscillator, also known as quartz crystal oscillator, has directionality. If the crystal oscillator is reversed, it will be damaged by current. Passive crystal oscillator, also known as quartz crystal resonator, does not affect the circuit because the crystal itself has no directionality, so it does not matter whether it is directly attached or not.
Passive crystal oscillator is called Crystal in English, and its full Chinese name is quartz crystal resonator. Some people often refer to passive crystal oscillator as crystal. There are two types of crystal resonators: plug-in and surface mount. Whether it is plug-in or surface mount, or has two, three, or four legs, there is no positive or negative polarity or directionality during surface mount or soldering, so there is no need to worry about reverse mounting.
Application principle of passive crystal oscillator circuit: The characteristic of passive crystal oscillator is that it needs to be driven by peripheral circuits to generate oscillating clock signals and cannot start oscillating on its own. In passive crystal oscillator circuits, it is generally necessary to select a suitable external capacitor value for optimal matching, in order to fine tune the frequency of the passive crystal oscillator and make its output frequency as close as possible to the nominal frequency center point.
Two pin passive crystal oscillator: one pin is the frequency output pin, and the other pin is the frequency input pin. Even if reversed, the crystal oscillator still works normally.
Three pin passive crystal oscillator: The two pins are frequency output pin and frequency input pin, and the middle pin is grounded. Except for paying attention to grounding this grounding pin, the usage of the pins on both sides is no different from that of a two pin crystal oscillator, regardless of whether it is positive or negative.
Four pin patch passive crystal oscillator: Pin 1 and Pin 3 are frequency input pins and frequency output pins, while the other two pins are grounding pins. Even if it is rotated 180 degrees, only Pin 1 and Pin 3 exchange positions, that is, the input pin becomes the output pin, and the output pin becomes the input pin. The crystal oscillator can still work normally without any performance or functional differences.
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