Preamble: I have been pushing the “I believe” button for way to long when it comes to crystal oscillators and their supporting components. The concept is simple, as they generally consist of proper loading and some kind of (pre)amplifier. “Small thing shake fast and you amplify”. However, the full concept has never “clicked” in my brain and it feels like a huge knowledge gap that I should have filled years ago.

Asking these questions is horrendously embarrassing since I am a licensed ham and I should intuitively understand how all resonant circuits work by this point in my life. (Hopefully, y’all have a better way for me to visualize resonant circuits in general.)

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From this schematic, all I see is a DC source, an amplifier, and maybe a super-simple RC tank circuit (of sorts) and the wave should never drop below 0v:

Some of the most basic crystal schematics (concept diagrams?) show a crystal connected directly to an AC source.

The concept of a crystal is simple: Apply a voltage and it moves, remove that voltage and it returns to its original shape. That kind of explains why kick-starting oscillation is needed, but that is not really where I am confused.

My questions are:

Is the crystal more closely related to an inductor in a basic RLC circuit? Is L being an approximate relationship to X a good way to visualize this?

Does the crystal “force” an RC resonant circuit to operate at a specific frequency because of its tendency to only operate efficiently at a given frequency in wildly different environments? (This question is a result of the first: Does an inductor act like a crystal in some ways?)

Since basic BJT amplifiers are generally shown with super-basic crystal schematics, is that amplification a functional part of generating a wave form? So, if the BJT was removed, the circuit would still function but it would be at a much lower current? (TBH, I am getting a gut feeling that the BJT is functionally related to an opamp with feedback in the above schematic, maybe?)

Thanks in advance for any education. Cheers!

(Oh, I do understand we are mixing AC and DC circuit concepts here, so that isn’t an issue for me either. I also could just “look at the formulas” for building crystal circuits, but I need a better understanding of the core concepts first.)