Quartz crystal characteristics

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Quartz crystal characteristics

A quartz crystal is a piezoelectric device transforming electrical energy to mechanical

energy and vice versa. The transformation occurs at the resonant frequency. It can be

modeled as follows:

Figure 2.

Quartz equivalent circuitry

Where:

electrodes and the parasites of the contacts.

L (motional inductance) represents the vibrating mass of the crystal.

C (motional capacitance) represents the elasticity of the crystal

R represents the circuit losses.

Because R is normally negligible, the impedance of this circuitry is given by the following

equation:

The following figure represents the quartz reactance across its operating frequency:

Figure 3.

Quartz crystal reactance across frequency

R

LC

Z

j

w

----

w

2

LC

1

–

C

0

C

+

() w

2

LCC

0

–

---------------------------------------------------

×

=

Frequency

Impedance

Series Resonance

Anti Resonance

0

Area of usual parallel

resonance