Know about functionality of capacitors Crystal Load Capacitance
If you know how batteries work, then you won’t have any difficulty understanding the functionality of capacitors. Capacitors and batteries both store electrical energy. Inside a battery, chemical reactions generate electrons on one terminal and absorb it on the other. So is the case with a capacitor, as it can’t produce new electrons; it can only store them. Capacitors can be designed to serve any purpose, from the smallest plastic capacitor in your calculator, to an ultra capacitor to be used in electric cars.
The basic difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of second, where a battery would take time to completely discharge. That’s why, capacitors are used to store charge for high-speed use. Like, big lasers use this technique to get very bright and instantaneous flashes. Capacitors are also used to eliminate residual unwanted variations following AC to DC conversion. If a line carrying DC voltage has ripples in it, a big capacitor can even out the voltage by absorbing the peaks. Also, a capacitor can block DC voltage. If you clip a small capacitor to a battery, then no current will flow between the poles of the battery. However, alternating current (AC) signal flows through a capacitor unobstructed.
I hope this brief description can help you form an outline regarding capacitors functionality. However, determining the capacitance required for a crystal oscillator is not easy. Load capacitance is defined as being the total capacitance present in an oscillator circuit as measured or calculated across the pins of the crystal socket. Load capacitance has the effect of increasing the frequency of a crystal unit. As different crystals have different load capacitance requirements, it is essential to find the appropriate capacitor. Different crystal manufacturers design the crystals with different load capacitor requirements. Sometimes, variation in circuit layout complicates the problem and we need to add more capacitors to get required load capacitance.
Selecting an incorrect load capacitance for a crystal can impact the frequency at which it oscillates. When load capacitance for a crystal is too high, the crystal oscillates at a slightly lower frequency. Likewise, when the capacitance is too low the crystal will oscillate slightly faster. These are some of the factors that need to be considered while selecting crystal load capacitance to ensure proper functioning of the application.
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