①Passive crystal oscillator
The passive crystal oscillator is a crystal, generally a 2-pin non-polar device (some passive crystal oscillators have non-polar fixed pins).
Passive crystal oscillators generally GPRS Module require the help of a clock circuit formed by a load capacitor to generate an oscillating signal (sine wave signal).
②Active crystal oscillator
Active crystal oscillators are oscillators, usually 4 pins. The active crystal oscillator does not require the CPU’s internal oscillator and generates a square wave signal. Active crystal oscillator power supply can generate a clock signal.
The signal of active crystal oscillator is stable, the quality is better, Single serial port server and the connection method is relatively simple, the accuracy error is smaller than that of passive crystal oscillator, and the price is more expensive than passive crystal oscillator.
three. Equivalent Circuit of Crystal Oscillator
In fact, the crystal acts like a series connected RLC circuit.
The equivalent circuit of a crystal oscillator shows a series RLC circuit representing the mechanical vibration of the crystal, with a capacitor in parallel representing the electrical connection to the crystal, and the crystal oscillator operates towards series resonant operation.
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