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Why put resistor across crystal?
Some crystals are unhappy with “high drive power” circuits and some crystals are “high activity”. It is possible to physically damage some crystals in some circuits from the mechanical energy involved. In such cases, adding a damping resistor can reduce cct Q and reduce the chance of crystal damage.
What is a crystal oscillator circuit?
A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a constant frequency. Quartz crystals are manufactured for frequencies from a few tens of kilohertz to hundreds of megahertz.
What is crystal in circuit?
What does a load resistor on an Arduino do?
From here, https://rheingoldheavy.com/arduino-from-scratch-part-9-16mhz-crystal-oscillator/ , similar to @Spehro’s answer above, This resistor is actually acting as a feedback resistor for the micro’s internal inverter to which the crystal is connected, and biases the inverter’s input into the linear region.
Is it possible to damage a crystal with a damping resistor?
Some crystals are unhappy with “high drive power” circuits and some crystals are “high activity”. It is possible to physically damage some crystals in some circuits from the mechanical energy involved. In such cases, adding a damping resistor can reduce cct Q and reduce the chance of crystal damage.
Why do you need a bias resistor in an IC?
The bias resistor (internal or external) is required for the oscillator to reliably start up- it biases the amplifier into the linear region where noise can be amplified to get the crystal oscillator going. IF an IC manufacturer specifies that a resistor is needed then it probably is.
What does a crystal oscillator on an Arduino do?
This resistor is actually acting as a feedback resistor for the micro’s internal inverter to which the crystal is connected, and biases the inverter’s input into the linear region. “Biasing into the linear region”, means that it is amplifying the crystal’s oscillation without ever fully saturating at one of the voltage rails.