Posted on 04/15/2005 2:06:56 PM PDT by LaserLock
A pair of physicists in the US has built the fastest ever transistor: one that can operate at a frequency of over 600 gigahertz. Developed by Walid Hafez and Milton Feng at the University of Illinois at Urbana-Champaign, the device is made from the semiconductors indium phosphide and indium gallium arsenide (Appl. Phys. Lett. 86 152101). The work demonstrates the feasibility of making transistors that can operate at frequencies of several terahertz, which could be used in ultrafast communications, high-speed computing, medical imaging and sensors.
The new device is a so-called bipolar transistor, which is very different from the more well-known field-effect transistor. In it, electrons are injected from the "emitter" terminal, travel towards the "base" and are then received by the "collector", an arrangement that allows the device to work faster than a field-effect transistor.
Hafez and Feng have previously built a high-frequency bipolar transistor, but this earlier work focused on reducing the time it takes electrons to pass through the device by minimizing the device's vertical thickness. Their new research further increases electron speeds through the device by slightly varying, or "grading", the composition of the semiconductor layers. This, say the researchers, lowers the band gap in selected areas of the transistor and makes it easier for electrons to travel across the device.
The two physicists have shown their transistor can operate at a frequency of 604 gigahertz, a new record. However, according to Hafez, what is more important is that they have developed a technology that could be used to build transistors operating in the terahertz range. "Projections from our earlier high-frequency devices indicated that in order to create a transistor with a cutoff frequency of 1 terahertz, the devices would have to operate above 10,000 degrees C," he says. "By introducing the grading into the layer structure of the device, we have been able to lower the potential operating temperature for a terahertz transistor to within an acceptable range."
Devices operating at terahertz frequencies (the far infrared) could be used in communications applications or as sensors to detect toxic gases. They could also be used for medical imaging, since the radiation is long enough to penetrate skin and image what lies underneath.
The researchers' next step is to show that their devices can be assembled into circuits.
White with a color stripe depending if it was TTL, linear or CMOS etc.
Dunno....
I've always used the ICMaster series. :)
I still have my white with blue TTL and the 1982 TTL. The TI TTL book is the venerable hard bound one ... still got it.
"Extra credit ... what is the color is the cover of the old Signetics TTL book"
LOL. I worked at Signetics from 1970-73 and I retired from TI.
I have built billions and billions of bipolar transistors.
In 1968-70 this gentleman was one of my drinking buddies. (BTW, I worked for Talbert mentioned in the article)
Hmmmm .... I wonder if they'll make this in a Schottky version, or maybe even in a "LS" version? Ha! My brain's smoking trying to recall all this ancient stuff!
a general purpose counter timer!
Isn't the 556 a dual timer chip and the 555 a single?
Don't remember whether I used the IC master series or not. When I was designing using the old TTL I was designing to the mil spec. Where one uses the 54 instead of the 74 designator 7400 = 5400 ... 7474 flop = 5474 . I spent some time with National Semi ... so I have all their blue with gold trim books.
I went from National Semi under Gil Amelio to Motorola to Intel
Ti made me a recent offer to work in Schlumberg north of Chicago ... and Ti San Diego made an offer too. I wound up at Intel
Specifically a "TTL" or "T2L" quad dual input positive NAND gate...
Don't forget that the "SN" means it was made by Signetics
Great.
I was the 57th employee of National and I did make a two year excursion to Harris in Florida...great area, lousy company.
IIRC, it was a brownish yellow -- at least in the 70's...
We have a winner !!!!
Good ol' Harris Semi ... I used some of their stuff in my designs
>>> TI TTL book. <<<<
A tanish yellow in hard cover
Still have it
Signetics
White
I recently left Intel and am now working for a small start up populated by a bunch of ol building "D" National guys
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