IBM Creates Ring Oscillator on a Single Nanotube

deeptrace writes "IBM has combined CMOS circuitry and a single carbon nanotube to implement a 5 stage ring oscillator. Even though the oscillator runs at just 52 MHz, they expect that it could reach the GHz range with improvements. The frequency of the current oscillator was higher than previous circuits using multiple nanotubes. IBM describes the achievement in the paper "Integrated Logic Circuit Assembled on a Single Carbon Nanotube" to be published this week in the journal Science."

Comments

So...

[Anonymous Coward]

I was misled to believe that the entire circuit was literally on the surface of the nanotub but from the picture in the article it looks like the nanotube is touching a couple of pads.

Anyway, what is the significance of the low frequency? Is the ring oscillator circuit supposed to be limited in frequency only by process parasitics, so that researchers can determine the maximum frequency the process can sustain?

Nanotubes..

[William Robinson]

A nanotube turns on for both negative and positive voltage, and turns off somewhere in the middle

What exactly this means?

Cool!

[Mister Transistor]

Right in the middle of the 6-meter Amateur Radio band! Sounds like a nice local oscillator for an ultra-tiny nano "rig". Now, to figure out how to directly modulate it for direct FM or FSK.

Here's why a ring oscillator

[sidney]

A number of posts have asked about the significance of a 5 stage ring oscillator.

That's the same circuit mentioned in the recent transparent IC story where TFA said

OSU says the near-invisible integrated circuit (IC) implements a five-stage ring oscillator, a function often used for testing and demonstrating new technologies. This is analogous to when software developers write programs that simply say "hello world," as an early step in testing and debugging new computer languages.

Re:A what?

[ncc74656]

What the hell is a ring oscillator, you ask?

After reading that WP article, I think I'm still asking ;)

After reading it, it sounds like a project from one of the Radio Shack electronics kits I had back in the day. One of the components in this kit was a 7400, a quad 2-input NAND gate. By tying the two inputs of a NAND gate together, it's the equivalent of an inverter. By using one or three of the gates wired in a loop, you could make a one- or three-stage ring oscillator.

I don't recall if the documentation identified the circuit as a ring oscillator, but I think some projects used it (maybe with a capacitor somewhere in the loop to slow it down) as a clock source.

drain?

[Hawkxor]

From the article: "Circuit designers understand that n-type transistors can be turned on with positive voltage applied to the drain; p-types are exactly the opposite."

Surely they mean 'applied to the gate' (the input voltage is gate to source, the output voltage is drain to source)

            D
            |
          _|
  G ||_
            |
            |
            S

Re:Odd... just did this in class today...

[CTho9305]

I actually put together this earlier this month to show someone that even in a simulation environment, with every node starting at the same voltage (which should be a "stable" state, as long as it's not disturbed by outside influences), the floating point inaccuracies in the simulator are sufficient for oscillation to start spontaneously.

Trinary systems?

[Quince alPillan]

I was going to make a smartass remark about being able to use "new and improved" trinary computers, with positive, negative, and neutral voltages on these transistors, but then I found out they already exist!

D'oh!

Well, at least I can welcome our ternary computing overlords!