Frequently Asked Questions

  • What is the Piezoelectric effect?

    Quartz crystals rely on the piezoelectric effect for their operation. This involves a quartz resonator connected with electrodes on both faces and mounted in a sealed holder. Applying an external AC voltage to these electrodes generates a mechanical vibration. To know more characteristics of Quartz crystal, refer our App Note  

  • What is the minimum information needed to order a crystal?

    The following specifications are required to be able to quote the correct part:

    1. Frequency of oscillation: (MHz)
    2. Model Name or Package size: (mm)
    3. How many connections (pads) 4 or 2
    4. Tolerance: (±ppm). The maximum acceptable deviation from the required frequency of oscillation, when at 25°C
    5. Stability: (±ppm), The maximum frequency deviation across the temperature range, referenced to the frequency at 25°C (Tolerance)
    6. Temperature Range: (°C). The temperature range over which the stability will be within specification
    7. Load Capacitance: (pF). The combined capacitance presented to the crystal by the PCB. Including any stray capacitance
    8. For MHz frequencies: Overtone Order: The number of physical oscillations within the quartz. In most cases, this will be fundamental.
  • What is load capacitance?

    The capacitance of the oscillator circuit is connected to the quartz crystal, whether in series or parallel configuration. The most common type of crystal is parallel resonant, where the crystal operates at a frequency above its series resonant frequency (the point of lowest impedance). The capacitance value is also crucial for determining the frequency tolerance. To learn more about this topic refer to our blog regarding: The common myths around load capacitance

  • Will the crystal operate outside its specified temperature range?

    Yes! For example, if a crystal is specified over –10 to +60°C it will perform without any issue over –40 to +85°C but it is possible that it will fall outside its specified stability. This may not matter if the application needs just a stable frequency rather than an accurate frequency.

  • Why is it important to specify the operating temperature range?

    If the temperature goes significantly outside the specified temperature range it is possible that damage to the crystal may be caused. Also, refer above.

  • Explain the differences between fundamental crystals and overtone crystals

    A fundamental crystal oscillates at a frequency determined by the dimensions of the quartz blank. Overtone crystals operate at the 3rd, 5th, or 7th multiple of the fundamental frequency. The crystal is specifically designed to operate in overtone mode, and enables higher frequencies to be achieved.

  • Where do I get specifications of the IQD products?

    To review our parts and their respective specifications, you can visit our parametric search page IQD Quartz Crystals (MHz). If you need additional information, please visit our contacts page

  • Who do I call for technical assistance at IQD?

    Our technical team is experienced and can provide you with information regarding our extensive catalogue of frequency products. We also offer additional technical support for your designs, including custom product development, testing and more.

    Discover our dedicated page Engineering Support Services for more details on technical support. 

  • I am thinking of changing an existing design from THT crystals to SMD crystals – what do I need to consider?

    This depends upon the application.  For example, if the crystal is pullable i.e. the frequency can be changed by varying the load capacitance of the crystal by electrical means, then this may be difficult to achieve. For example strip blank SMD crystals have a very much lower pullability than the HC49 style round blank package. 

    This exercise should not be undertaken lightly and if you are in any doubt, contact IQD's Applications Support department for further advice. Get in touch  

  • Is it preferable to design-in a crystal or an oscillator for my application?

    This depends upon the application. If you are designing a discrete circuit and have little or no experience of oscillator design then it may be preferable to use a packaged oscillator since this will remove any tolerance issues. It is "easy" to design a "one off" for lab use but if you have to manufacture large numbers in volume this may give rise to a variety of issues. If you are using a chipset which requires a crystal to drive it then this decision is much simpler since the on- board oscillator circuit should have been optimised. 

  • What are the differences between SPXO, VCXO, TCXO, OCXO, Disciplined Oscillator and Rubidium Oscillator?

     SPXO - Simple Packaged Crystal Oscillator

    An SPXO or a Simple Clock Oscillator is the most basic type of oscillator and consists of a crystal and a basic drive circuit. Since there is no form of compensation the frequency/ temperature stability is essentially that of the crystal itself – typically ±50ppm.To know more on how to specify a SPXOs refer to our App Note

    VCXO - Voltage Controlled Crystal Oscillator

    A VCXO relies on the inherent pullability of the quartz crystal to allow the output frequency of the oscillator to be changed by applying an external voltage. This change is limited to a few tens of ppm, typically ±100ppm. As with SPXO's, the frequency/ temperature stability is that of the crystal itself. To know more about VCXOs refer our App Note

    TCXO - Temperature Compensated Crystal Oscillators

    Where the stability of the crystal is not sufficient it may be necessary to use a TCXO. This type of device is used where the stability of a basic quartz crystal is insufficient. Typically, TCXO's can achieve a stability of less than ±1ppm in preference to a typical crystal of 30ppm. Refer more on TCXOs in our App Note

    OCXO - Oven Controlled Crystal Oscillators

    The "ultimate" piezoelectric product is the OCXO offers performances of typically 3E10-9. Where a very high stability is required then this type of product should be considered.  Refer for more on OCXOs in our App Note

     Disciplined OCXOs

    Disciplined are essentially OCXOs with additional capability for precise timing synchronization down to 1 pulse per second (1pps). This clock module is exceptionally accurate as it is synchronized with GNSS signals. DOCXOs play a crucial role in environments where regular signal outages should not disrupt the intended application. For more refer our leaflet

    Rubidium XOs

    Rubidium oscillators are atomic clock modules that are preferred for their long-term stability. They also have an OCXO along with a physics-package at the centre of their circuitry and the change in the energy levels in the rubidium gas chamber generates the desired o/p frequency. Refer here to know how to specify a Rubidium Oscillator.

  • Can IQD offer solutions for obsolete parts?

    If a product has become obsolete or is reaching its end of life, our Applications Support team will be happy to advise you with a suitable alternative product. Please call

  • Does IQD offer Fast-make oscillators?

    Yes; if the device that you are looking for is not a stock part then a programmable oscillator may be available, these are compatible with the fixed frequency device and can often be supplied in just a few working days. By comparison, a custom fixed frequency part may take up to 6 weeks in production. Programmable oscillators (or Fast-make Oscillators) particularly lend themselves to prototyping where time is critical. Despatch times are dependent on quantity; please contact us for further details.

  • Are IQD's products available through Distribution?

    The answer is yes. Please look under the Distributors page. Find the link here: Distributors 

  • Does IQD offer products which are not on its website?

    Yes; our engineering department is constantly developing our product range and indeed much of its capability is in customisation. If you have a requirement for a custom product or have details of a competitor’s part, our team will be delighted to assist and advise you. You can get in touch by filling this form: Application Support

  • Why are crystal packages getting smaller?

    Miniaturisation is an ongoing trend in the electronics industry. Wearables, smart home devices, mobile devices and electronics in automotive applications are just a few examples demanding progressively smaller components. However, this size reduction can cause issues during the designing process – in general, the smaller the crystal blank, the higher the starting frequency.

    For example, the lowest frequency in a 7x5mm package is approximately 6MHz whereas it is approximately 12MHz in a 2.5x2mm package with lower frequencies being achieved by external frequency division which increases circuit complexity.


  • Can I obtain the test results for my products?

    All sample orders are dispatched with the appropriate test result data. Production order quantities are tested to the Appropriate Quality Level (AQL), and the test result data is retained in our company records. For further information, please CONTACT US

  • What is the most common cut of Quartz Crystal?

    AT-cut quartz accounts for the majority of crystals produced in the 1 to 200MHz range. This term simply refers to the nominal angle with respect to the Z-axis of the quartz bar. The cut angle determines the frequency/temperature performance and is typically chosen by the crystal manufacturer.