Crystal, Resonator and Oscillators, what’s the difference ?

Today, We are going to discuss about the basic differences between Crystal, Resonator and Oscillator. Most of the people are confused about the fine line of differences between three of them. Let me tell you these 3 are different things for almost same purpose, that purpose is to generate Clock signal of some fixed frequency.

Its not only me, Digikey also stocks these things under 3 different categories…

This is what Crystals Looks like at Digikey

and Oscillator at Digikey

and Finally Resonators at Digikey

So, Visually also they are very different

Resonator

Oscillator

Crystal

Functionality Wise also they are different, though the purpose is same almost all the time.

1. Both ceramic resonators and quartz crystals work on the same principle: the vibrate mechanically when an AC signal is applied to them. Quartz crystals are more accurate and temperature stable than ceramic resonators. Both Quartz Crystal and Ceramic resonator has two legs with no specific pin orientation that means you can solder/plug it into the circuit either way.
2. Ceramic Resonator and Quartz Crystal are Passive devices, They are meant to generate clock signals but they alone can not generate Stable clock signal, both of them need some external circuitry around them to sustain oscillations. Like you must have seen the two PF capacitors around Quartz Crystals. On the other hand Clock Oscillators are Active devices and can generate clock independently without and external circuitry.
3. Since most of the chips and Micro controllers (which require external clock) have clock stabilization circuitry inside them, So all you need to do is plug in the Quartz Crystal or Resonator of appropriate value in the Two terminal and the Chip itself oscillates the Quartz Crystal or Resonator. The benefit is both Quartz Crystal and Resonator are very Cheap to buy and easily available, While clock oscillators are expensive and not easily available.
4. When using clock Oscillator you need not to use OSC_OUT pin of the Micro controller, You can directly feed the output of Clock Oscillator into the OSC_IN pin of the MCU and you are done. No need to tell that Ground must be common.
5. Clock generated by clock Oscillator is much more stable than either of Quartz Crystal or Ceramic Resonator.