Quartz Crystals vs. Ceramic Resonators

On Considering the Benefit of Quartz Crystal Oscillators Over Ceramics In Application

Apply an AC signal to a quartz crystal or a ceramic resonator, and the result is largely the same—they vibrate mechanically. This useful feature has been used for over 100 years to drive our electronics, especially when it comes to timekeeping and frequency measurement.

But there are significant differences in how quartz crystals and ceramic resonators work that can influence your choice in your application. Let’s look at how each of these fantastic tools is used, the differences between them, and how you might decide between them for your next project.

How Do Ceramic Resonators Work?

A ceramic resonator is an electronic component that uses ceramic. Ceramics are typically created by taking inorganic, nonmetallic materials and subjecting them to high temperatures. Basic ceramics are used in porcelain, brick, and earthenware.

In most cases, ceramic resonators are made from lead zirconate titanate (PZT). This material is piezoelectric, meaning that when stress is applied to the material an electric charge is created, and vice-versa. Piezoelectricity has been used since 1880 in applications from inkjet printing and clocks to electric guitar pickups and electronic drums.

In a ceramic resonator, the ceramic is connected via an electronic oscillator circuit. This causes the mechanical vibrations to create a rhythmic oscillating signal at a specific frequency. This rhythmic oscillation is most commonly used to control timing in electric circuits. Computers use many ceramic resonators, and they’re also used in radio transmitters and receivers.

How are Quartz Crystals Used in Crystal Oscillators?

Quartz is a crystalline silicate mineral and the second most abundant material found in the continental crust of the Earth. Like the ceramics used in ceramic resonators, quartz crystals exhibit piezoelectric properties. Apply mechanical stress, and quartz crystals will generate an electric pulse.

Quartz crystals were first used for their piezoelectric properties in phonographs. Today, the most common use of quartz’s piezoelectricity is in a crystal oscillator. Most people will recognize the use of quartz in quartz clocks and wristwatches, where timekeeping can be extremely accurate. And because a quartz crystal oscillator’s resonant frequency can be changed by mechanically loading it, quartz is excellent for detecting very small mass changes in precise instruments. This means high-quality quartz crystal oscillators are used abundantly in laboratory test equipment.

What’s the Difference Between Ceramic Resonators and Quartz Crystals in Application?

Quartz crystals have much higher frequency tolerance than ceramic resonators, which essentially means they are more accurate. Quartz’s tolerance is 0.001%, whereas PZT ceramic resonators are around 0.5%.

Quartz crystal oscillators are better suited for applications that require excellent frequency tolerance. We can think of this as the difference between being able to record the number of seconds between two runners in an Olympic race, and being able to record down to the millisecond. Ceramic resonators are good timekeepers, but quartz crystal oscillators are more precise.

Quartz crystal oscillators have a much higher Q factor than ceramic resonators. In basic terms, Q refers to the quality of the resonant circuit. Excellent ceramic resonators can only achieve a frequency range between 190 kHz and 50 MHz. Crystal oscillators can have a much wider range, from 10 kHz – 100 MHz.

When temperatures change, quartz crystal oscillators maintain their phase noise performance and low jitter.  So, quartz crystals are the preferred option over ceramic resonators for harsh environments or when a wide temperature range is possible.

On the other hand, ceramic resonators have a higher tolerance for shock and vibration. They also have better tolerance for electrostatic discharge than quartz crystal oscillators.

Choosing Crystal Oscillators or Ceramic Resonators

Ceramic resonators, therefore, are best used in applications where exact frequency and timing aren’t too important. In day-to-day electronics, this is quite a lot of devices, including communication equipment, cameras, telephones, TVs, and DVD players. Absolutely perfect timing isn’t required, so manufacturers can use less expensive ceramic resonators instead of quartz crystals.

Ceramic resonators are relatively inexpensive and simple to manufacture. Crystal oscillators are more challenging to make, which drives the price up. They’re also relatively sensitive to shock and vibration.

Yet, overall, quartz crystal resonators are usually the best option. A ceramic resonator in a wall clock, for example, might see a drift in time of a few minutes each year, whereas a quartz clock would remain almost dead-on.

When accuracy in timing is important, which is a significant percentage of applications, it’s best to choose a quartz crystal resonator over a ceramic resonator. For applications where timing and frequency tolerance is mission-critical, crystal resonators are a requirement.