Glossary of Crystal Terms

Glossary of Crystal Terms


Quartz crystal aging applies to the cumulative change in frequency which results in a permanent change in operating frequency of the crystal unit. The rate of change in frequency is fastest during the first 2 - 3 months of operation. Many interrelated factors are involved in aging, some of the most common being: internal contamination , excessive drive level, surface change of the crystal, various thermal effects , etc...
Proper circuit design incorporating low operating ambients, minimum drive level and static pre-aging will greatly reduce all but the most severe aging problems

Calibration or Adjustment Tolerance

The setting tolerance is the maximum allowable deviation from the nominal frequency at 25°C +- 3°C. It is normally specified in parts per million (ppm)

Drive Level

Drive level is the level of power dissipated in the crystal as a result of the operating circuit. Rated or test drive level is the power at which the crystal is specified and any deviation from the rated level will effect the crystal performance; therefor the actual drive level should reasonable duplicate that specified.
AT - cut crystals generally can withstand a considerable overdrive without physical damage, however the electrical parameters are degrated at excessive drive

Equivalent Serie Resistance (ESR)

For crystal units designed to operate at series resonance, ESR is the equivalent ohmic resistance of the unit when operating in the specified crystal impedance meter adjusted for the rated drive level and tuned to the specified crystal frequency

Load Capacity ( CL)

This is an external capacitance which sets a point on the reactance curve at which the crystal will resonate. It is normal to refer to crystals which are operated with a small value of CL as "parallel resonant" and to those which are not as "series resonant"

Nominal Frequency

The nominal frequency of the crystal . This is expressed in Megahertz ( Mhz) for frequencies of 1.0 Mhz and over. Frequencies may be specified up to seven significant figures. If less are specified, then we may assume any digits that follow are zero

Operating Temperature Range

This is the temperature range over wich the quoted temperature stability is specified


The pullabilty of a crystal refers to a crystal operating in the parallel mode and is a measure of the frequency change as a function of load capacitance. Pullability is important to the circuit designer who wishes to achieve several operating frequencies with a single crystal by means of switching various values of load capacitance

Shunt Capacity (Co)

The "static capacity" or shunt capacity of the electrodes, the holder and the leads. It is usually measured with an ungrounded case

Spurious Response

It is also possible for a crystal to vibrate at a frequency that is not related to its fundamental or overtone frequencies. Such undesired frequencies are referred to as spurious responses.Our processes are designed to minimise (not eliminate) the spurious responses and maximise the crystal activity at the desired frequency. The circuit designer should further guard against spurious responses by ensuring that the oscillator feedback circuit achieves its highest gain at the desired operating frequency

Storage Temperature Range

The temperature range in which the crystal can be stored without damage,i.e. it will resume operation as normal once it is restored to within its operable temperature range

Temperature Stability

The stability tolerance is the maximum allowable deviation from the nominal frequency over a specified temperature range and expressed in terms of ppm. This factor is dependent upon the angle of cut