5 ms·

I think it's so interesting that the best oscillators we can use in electronic circuits, atomic clocks excluded, all operate in the mechanical domain. If I knew

I think it's so interesting that the best oscillators we can use in electronic circuits, atomic clocks excluded, all operate in the mechanical domain. If I knew nothing, I would assume we could build good RC oscillators, which are purely electrical.

jakeinspace 8y ago
I suppose once you're in the domain of crystal oscillators, the line between "mechanical" versus "purely electrical" is a bit fuzzy. The mechanical/thermal effects of passing a high-frequency signal through passive components (or a transmission line) might be comparable to the mechanical vibrations of a quartz clock, though somebody better at physics could probably correct me.
Gibbon1 8y ago
The big advantage of mechanical oscillators vs RC occilators is mechanical ones have very high Q. Q is related to the ratio of resonant energy vs the amount lost per cycle. High Q oscillators allow you to produce spectacularly pure and or accurate signals. That's important for RF applications. On the other hand RC oscillators can start up very fast. In uS vs milliseconds. Lot of microcontrollers have an internal RC oscillators for that reason. Go to sleep and wake up instantly. TI's announcement is interesting since external crystals for RF transceivers is a pain point in design and manufacturing. You can have inexplicable variation from one batch of crystals to another. Batch's of IC's. Variations in the PCB material, etc.
ajross 8y ago
What does "purely electrical" mean at this scale? Quartz resonators are piezoelectric devices, after all. The same field of solid state physics that explains a MOSFET is required to explain a oscillator.
- SamReidHughes 8y ago
  Quartz resonators still move and are affected by the direction of gravity
  - ajross 8y ago
    So do electrons and nuclei.
  - Gibbon1 8y ago
    Piezoelectric respnators are using mechanical resonance. You can build LC resonators. And also resonant cavity resonators. LC are electrostatic/magnetic. Cavity resonators work off standing waves.
  - gugagore 8y ago
    Yes! Here's a video: https://www.youtube.com/watch?v=zILwgQhjC_Q https://www.youtube.com/watch?v=zILwgQhjC_Q
- xyzzyz 8y ago
  It means that it doesn't literally physically vibrate, like quartz oscillators do. It's only the electric field that vibrates in it, not the physical thing itself.
  - ajross 8y ago
    I know what it means. I was pointing out (charitably) that that's a silly distinction. An electronic oscillator ABSOLUTELY vibrates "physically". Those electrons are "physical things" and have mass. They have momentum. Those things can be measured and have an impact on the circuit. Even your assumption that the transistor body doesn't move is wrong in practice. Those electric fields absolutely produce strains (that is, real physical forces) on the semiconductor junction, and those strains affect electronic properties and are included in fancy circuit models (or at least I saw a paper about it once, anyway). The idea of "solid state" machines having "no moving parts" is a lie told to you by your electronics textbooks. It's a useful abstraction. It's not the truth. And in this regime, it's frankly harmful to your understanding of how things work because it's led you to believe that crystals are doing something fundamentally different than circuits.
    - gugagore 8y ago
      Maybe if you can show me that if you flick an RC oscillator you can detect it, then I'll believe it's a silly distinction. Or if RC oscillators can detect gravity: https://www.youtube.com/watch?v=zILwgQhjC_Q https://www.youtube.com/watch?v=zILwgQhjC_Q I'm also curious what it would mean to you for two things to be doing "fundamentally different" things. Do you believe in the difference between a mechanical oscillator and an electrical oscillator? Mechanical oscillators like a spring/mass exchange energy between kinetic and electrical energy (a moving mass and a strained material). An RC oscillator exchanges energy between elements that store energy in an electric field and a magnetic field. That feels fundamentally different even in a four-fundamental-forces kind of manner.
    - hasmanean 8y ago
      Quartz crystals oscillate like a slab of jello vibrates. It’s not moving like a pendulum or anything...rather the bulk material is expanding and contracting and energy is stored in the deformation of the crystal lattice.
ahartmetz 8y ago
What I find even more mind-blowing is that GHz range frequency filters in cellphones are mechanical. They have excellent selectivity and need very little energy. Check it out: http://www.telecomabc.com/s/saw-filter.html http://www.telecomabc.com/s/saw-filter.html

jakeinspace 8y ago

I suppose once you're in the domain of crystal oscillators, the line between "mechanical" versus "purely electrical" is a bit fuzzy. The mechanical/thermal effects of passing a high-frequency signal through passive components (or a transmission line) might be comparable to the mechanical vibrations of a quartz clock, though somebody better at physics could probably correct me.

Gibbon1 8y ago

The big advantage of mechanical oscillators vs RC occilators is mechanical ones have very high Q. Q is related to the ratio of resonant energy vs the amount lost per cycle. High Q oscillators allow you to produce spectacularly pure and or accurate signals. That's important for RF applications. On the other hand RC oscillators can start up very fast. In uS vs milliseconds. Lot of microcontrollers have an internal RC oscillators for that reason. Go to sleep and wake up instantly. TI's announcement is interesting since external crystals for RF transceivers is a pain point in design and manufacturing. You can have inexplicable variation from one batch of crystals to another. Batch's of IC's. Variations in the PCB material, etc.

ajross 8y ago

What does "purely electrical" mean at this scale? Quartz resonators are piezoelectric devices, after all. The same field of solid state physics that explains a MOSFET is required to explain a oscillator.

SamReidHughes 8y ago
Quartz resonators still move and are affected by the direction of gravity
- ajross 8y ago
  So do electrons and nuclei.
- Gibbon1 8y ago
  Piezoelectric respnators are using mechanical resonance. You can build LC resonators. And also resonant cavity resonators. LC are electrostatic/magnetic. Cavity resonators work off standing waves.
- gugagore 8y ago
  Yes! Here's a video: https://www.youtube.com/watch?v=zILwgQhjC_Q https://www.youtube.com/watch?v=zILwgQhjC_Q
xyzzyz 8y ago
It means that it doesn't literally physically vibrate, like quartz oscillators do. It's only the electric field that vibrates in it, not the physical thing itself.
- ajross 8y ago
  I know what it means. I was pointing out (charitably) that that's a silly distinction. An electronic oscillator ABSOLUTELY vibrates "physically". Those electrons are "physical things" and have mass. They have momentum. Those things can be measured and have an impact on the circuit. Even your assumption that the transistor body doesn't move is wrong in practice. Those electric fields absolutely produce strains (that is, real physical forces) on the semiconductor junction, and those strains affect electronic properties and are included in fancy circuit models (or at least I saw a paper about it once, anyway). The idea of "solid state" machines having "no moving parts" is a lie told to you by your electronics textbooks. It's a useful abstraction. It's not the truth. And in this regime, it's frankly harmful to your understanding of how things work because it's led you to believe that crystals are doing something fundamentally different than circuits.
  - gugagore 8y ago
    Maybe if you can show me that if you flick an RC oscillator you can detect it, then I'll believe it's a silly distinction. Or if RC oscillators can detect gravity: https://www.youtube.com/watch?v=zILwgQhjC_Q https://www.youtube.com/watch?v=zILwgQhjC_Q I'm also curious what it would mean to you for two things to be doing "fundamentally different" things. Do you believe in the difference between a mechanical oscillator and an electrical oscillator? Mechanical oscillators like a spring/mass exchange energy between kinetic and electrical energy (a moving mass and a strained material). An RC oscillator exchanges energy between elements that store energy in an electric field and a magnetic field. That feels fundamentally different even in a four-fundamental-forces kind of manner.
  - hasmanean 8y ago
    Quartz crystals oscillate like a slab of jello vibrates. It’s not moving like a pendulum or anything...rather the bulk material is expanding and contracting and energy is stored in the deformation of the crystal lattice.

ahartmetz 8y ago

What I find even more mind-blowing is that GHz range frequency filters in cellphones are mechanical. They have excellent selectivity and need very little energy. Check it out: http://www.telecomabc.com/s/saw-filter.html http://www.telecomabc.com/s/saw-filter.html