Tips on Selecting Oscilators
Most electronics use oscillators in them, and in most cases a digital circuitry needs a clock and radio frequency signals require an oscillator or clock and some analog circuitry need a clock or oscillating signal source. Just incase the If the person is using a microcontroller, then they might need to have a built-in clock, and even though it might be inaccurate depending on the application, thus the person may need to utilize an external crystal or a clock module instead of being able to use the internal clock.
The circuitry of a digital oscillator is just an analog OCXO oscillator that has clips and depending on how the person views it and some oscillators produce a 'clipped sine' output since it is hard to decide which particular category to put them in whether they are analog or digital. In truth digital oscillators can become more complicated that just creating a single clock signal and they may even generate several signals with a defined phase shift or have a frequency synthesizer to create one or more alternative frequencies from a frequency input clock.
The most common digital oscillator was built back in the 1920s, and it has been used for a long time for microprocessors clock generation, and when the person has a microcontroller that requires a crystal and two capacitors that are external to create its own clock, then they will have to make a particular a Pierce oscillator. When selecting an oscillator module or clock generator the person may need to understand the choices available and have to specify their requirements.
The output definition is one of these requirements, and it can be square or a clipped sine wave (which is rarely a true sine or digital system) and the person also needs to know that the voltage levels that they require because some oscillators have a low voltage differential signaling outputs and symmetry is also vital, so the high and low phases are equal. Know more about oscillators at https://en.wikipedia.org/wiki/Electronic_oscillator.
The person has to know the accuracy and stability that they require and with a ceramic resonator the person can get an initial tolerance of around 0.2% although at times it can be worse than that and the downside is that it is 2000 parts per million. It is worth noting that a quartz based oscillator has better stability than a ceramic resonator and stability can be defined as the temperature load or supply balance which can affect the frequency.
A temperature Compensated quartz crystal oscillator or Temperature Controlled Crystal Oscillator is an oscillator that can have both tolerance and stability that is better than 1ppm and such accuracies are vital for radio frequency systems where the frequency required has to be very precise.