While most applications will use a crystal
oscillator, two options may be a better
fit for your design: ceramic resonators and
surface-acoustic-wave (SAW) resonators.
Ceramic resonators are piezoelectric
components made from materials other
than quartz, like lead zirconium titanate
(PZT). These devices are smaller than
crystals and have a tolerance of about
0.5%, compared to the 0.001% or better
tolerance of a quartz crystal. Where
precision is only marginally important,
a ceramic resonator will work nicely at
much lower cost. A common application
is the clock in an embedded controller.
A SAW resonator uses an inter-digital
transducer on a quartz substrate. SAW
devices are used mostly for UHF/microwave
filters, but they can also work as
the frequency-determining component
in a oscillator. These oscillators usually
operate at frequencies in the 300-MHz to
1-GHz range, beyond the range of most
crystal oscillators. They can produce
good precision (±100 ppm) and low
phase noise.