Which of the following must be done to insure that a crystal oscillator provides the frequency specified by the crystal manufacturer? A. Provide the crystal with a specified parallel inductance…

Amateur Extra: Crystal Oscillator Frequency

Amateur Extra: Crystal Oscillator Frequency

Which of the following must be done to insure that a crystal oscillator provides the frequency specified by the crystal manufacturer?

A. Provide the crystal with a specified parallel inductance
B. Provide the crystal with a specified parallel capacitance
C. Bias the crystal at a specified voltage
D. Bias the crystal at a specified current

Hm.

A crystal oscillator is a high-stability device used to provide, well, oscillations in a circuit.  It is, basically by definition, a type of RLC tank circuit (we talked about that some here.)  Since the internal components of the oscillator are fixed, you need a way to provide the proper “load” to the circuit to complete it and “tune” it to provide the necessary impedance.  That’s where a “load capacitor” comes in.

You might have then guessed that the answer is B. Provide the crystal with a specified parallel capacitance.

There are a lot of complex things going on, and I recommend reading the following to maybe try and get a better handle on it:

Also note that the question is basically very generalized, there are a lot of other factors that can come into play, as there are many different types of oscillators and ways to properly tune them.

[E7H12]

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