From the equivalent circuit of quartz crystal resonator, it can be known that it has two resonant frequencies, that is, when a, L, C and R branches occur in series resonance, its equivalent impedance is the minimum (equal to R). The series resonant frequency is represented by FS, to which the quartz crystal shows pure resistance. B. When the frequency is higher than FS, the L, C and R branches show sensibility and can resonate with capacitor C in parallel. The parallel frequency is expressed by FD.
Based on the equivalent circuit of the quartz crystal, its frequency characteristics can be qualitatively plotted as shown in the graph. It can be seen that when the frequency is lower than the series resonant frequency FS or higher than the parallel resonant frequency FD, the quartz crystal is capacitive. Quartz crystals are electrically sensitive only within the very narrow range of FS < f < FD.
Based on the equivalent circuit of the quartz crystal, its frequency characteristics can be qualitatively plotted as shown in the graph. It can be seen that when the frequency is lower than the series resonant frequency FS or higher than the parallel resonant frequency FD, the quartz crystal is capacitive. Quartz crystals are electrically sensitive only within the very narrow range of FS < f < FD.
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