Post subject: Cryotron circuits? Posted: Mon Nov 17, 2008
Joined: Tue Dec 26, 2006 5:39 pm
Anyone here ever use a Cryotron? Ever seen one? I am curious
when (if) they fell out of use.
When did "the transistor" become
faster than a cryotron?
When did "the transistor" become cheaper
than a cryotron?
Do you know of any interesting applications
of these things other than as logic / memory devices?
were not ever RF circuits (were they?). However, I thought I would check
here to see if anyone has any experience or stories about these things.
Post subject: Posted: Tue Nov 18, 2008
Joined: Thu Sep 25, 2003 1:19 am
The following information is just
off of the top of my head. I did not find this is on Wikipedea.
The cryotron is a switch that operates using superconductivity.
The cryotron works on the principle that magnetic fields destroy superconductivity.
This simple device consists of two superconducting wires ( e.g. tantalum
and niobium) with different critical temperature (Tc). A straight wire
of tantalum ( having lower Tc) is wrapped around with a wire of niobium
in a single layer coil. Both wires are electrically isolated from each
other. When this device is immersed in a liquid helium bath both wires
become superconducting and hence offer no resistance to the passage
of electric current. Tantalum in superconducting state can carry large
amount of current as compare to its normal state. Now when current is
passed through the niobium coil (wrapped around tantalum) it produces
a magnetic field, which in turn reduces (kills) the superconductivity
of the tantalum wire and hence reduces the amount of the current that
can flow through the tantalum wire. Hence one can control the amount
of the current that can flow in the straight wire with the help of small
current in the coiled wire. We can think tantalum straight wire as a
"Gate" and coiled niobium as a "control".
A planar cryotron
was invented in 1957, made of thin films of lead and tin. This was one
of the first integrated circuits, although using superconductivity rather
than semiconductivity. In the next few years a demonstration computer
was made and and arrays with 2000 devices operated. A short history
of this work is in the newsletter of the IEEE History Center, number
75, November 2007.