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New transistor with unsurpassed high frequency performance
CURRENT New Transistor with Unsurpassed High Frequency Performance.-A major achievement that opens up new possibilities in electronics has been reported by Bell Telephone Laboratories. TWO articles in the January issue of the Bell System Technical Journal describe a major breakthrough in transistor technology-new fabricating techniques for an entirely new kind of transistor. These techniques may have far-reaching effects on the use and manufacture of the tiny amplifier, especially for electronic applications in the telephone industry, but in other fields too. The way is now open for the transistor to replace the vacuum tube in many telephone and television jobs. The new device’s performance at very high frequencies surpasses that of any other transistor. Transistor performance has been measured in two principal ways. One criterion has been the number of oscillations or self-generated electrical pulses per second. A second criterion, considered by Bell scientists to be more significant, is the number of voice or communication channels that can be amplified. In this latter category, they report that the new transistor is unequaled. Experimental units of the device made at Bell’s Murray Hill, N. J. lahoratories have amplified by 100 to 1 currents across a 20,000,OOO cycle wide band. Either the amplification or the number of communication channels can be made three times that of any other transistor. The number of communication channels or pathways varies with the degree of amplification. For example, if the frequency band were cut 468
TOPICS in half, thus halving the number of channels, there would be twice as much power amplification. Key to the new fabricating techniques is the development of controls over microscopic chemical layers. The heart of the new transistor is a layer 50 millionths of an inch thick. The new techniques involve the adaptation of the chemical process of “diffusion” used in treating silicon for the Bell Solar Battery, first device to convert sunlight into substantial amounts of electricity. Diffusion is a process by which minute amounts of impurities are introduced in controlled amounts into a material. In making the new transistor, an impurity must be introduced only once into the growing crystal. The fully grown crystal receives two other doses of impurity in the easily controlled diffusion process, which is more precise than the older “double-doping” and alloy processes. Both of these processes require control, at very high temperatures, of the boundary between liquid and solid germanium or silicon, in order to determine the dimensions of the base layer. This is very difficult compared with controlling diffusion, in which the desired foreign atoms move through the solid crystal to the required depths. The transistor consists of a threelayer chemical “sandwich.” The center layer is known as the “base.” The other two are the emitter and collector layers. The narrower the base layer can be made the higher the frequency at which it will operate. Diffusion provides a high degree of control of such microscopic dimensions.
Apr., ws6.1
CURRENT
In considering the practical application of transistors, engineers are concerned with what they call the “frequency cut off.” This is the frequent! point up to which there is straight, full amplification of a signal and after which the signal is amplified with steadil) diminishing strength. Currently available transistors have a frequency cut off of l-10 megacycles, and several recently anounced transistors have had a frequency cut od between 100 and 200 megacycles (lOO-200 million cycles). Thus far, the new transistors have been found to reach a cut off between 500 and 600 megacycles. Even though the effective operation of many military electronic devices is in a much lower megacycle range, the higher frequency cut off would provide a greater number of communication channels or more amplification than previously possible. Because of its very high frequency characteristics the new transistor ap pears to be ideally suited for application in guided missiles and electronic “brains” for military and computer uses. Tradic, an electronic computer designed by Bell Laboratories for military applications, already uses a transistor of a different type, and transistors are being used in other military equipment. While these transistors are well suited for the jobs they do, they cannot be used for a large number of other applications. The new transistor opens up many new possibilities for militarv technology. “Small” Brain Assists “Giant” Brain.-Something new in electronic computing-using a “small brain” to assist a “giant” in solving complex problems quickly-got underway recently at the United Aircraft Computation Laboratory, East Hartford, Conn. United Aircraft engineers be-
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gan using a Burroughs Corporation El01 electronic computer, which is the size of an office desk, to pilot the calcutions of a giant robot, which fills a large room, in designing advanced jet engines. Stuart L. Crossman, head of the Computation Laboratory, explained that the Burroughs “small brain” pilot operations are part of a process kno\l,n in the electronic computer field as “tlebugging the program”-checking the accuracy of instructions fed into thr “giant brain.” Mr. Crossman estimated that the use of Burroughs’ El01 will save hard-tofind computer personnel “from several hours to several weeks” in solving the hundreds of complicated mathematical problems involved in the design of aircraft engines and other aircraft components. One of the ElOl’s major attractions is that it does not require highly trained operator personnel. Because of that, Mr. Crossman said, the small computer is “well suited for departments where design and other engineering problems originate but whose personnel have no computer training. The El01 is about as easy as anything can be and still be an electronic computer. It can fit in a small office and gnyone can run it. Engineering Applied to Human Beings.-The principles which engineers have used to build great bridges are now being applied to the human mechanism in solving orthopedic problems. Plans to study the structural and mechanical functions of the bones, joints, and muscles-and the problem of braces and other mechanical aids for the body-have been announced by the INassachusetts Institute of Technology in cooperation with the Massachusetts General Hospital. A $10,000 grant to M.I.T. by the Donner Foundation, Inc., of Philadelphia will finance a two-
TOPICS in half, thus halving the number of channels, there would be twice as much power amplification. Key to the new fabricating techniques is the development of controls over microscopic chemical layers. The heart of the new transistor is a layer 50 millionths of an inch thick. The new techniques involve the adaptation of the chemical process of “diffusion” used in treating silicon for the Bell Solar Battery, first device to convert sunlight into substantial amounts of electricity. Diffusion is a process by which minute amounts of impurities are introduced in controlled amounts into a material. In making the new transistor, an impurity must be introduced only once into the growing crystal. The fully grown crystal receives two other doses of impurity in the easily controlled diffusion process, which is more precise than the older “double-doping” and alloy processes. Both of these processes require control, at very high temperatures, of the boundary between liquid and solid germanium or silicon, in order to determine the dimensions of the base layer. This is very difficult compared with controlling diffusion, in which the desired foreign atoms move through the solid crystal to the required depths. The transistor consists of a threelayer chemical “sandwich.” The center layer is known as the “base.” The other two are the emitter and collector layers. The narrower the base layer can be made the higher the frequency at which it will operate. Diffusion provides a high degree of control of such microscopic dimensions.
Apr., ws6.1
CURRENT
In considering the practical application of transistors, engineers are concerned with what they call the “frequency cut off.” This is the frequent! point up to which there is straight, full amplification of a signal and after which the signal is amplified with steadil) diminishing strength. Currently available transistors have a frequency cut off of l-10 megacycles, and several recently anounced transistors have had a frequency cut od between 100 and 200 megacycles (lOO-200 million cycles). Thus far, the new transistors have been found to reach a cut off between 500 and 600 megacycles. Even though the effective operation of many military electronic devices is in a much lower megacycle range, the higher frequency cut off would provide a greater number of communication channels or more amplification than previously possible. Because of its very high frequency characteristics the new transistor ap pears to be ideally suited for application in guided missiles and electronic “brains” for military and computer uses. Tradic, an electronic computer designed by Bell Laboratories for military applications, already uses a transistor of a different type, and transistors are being used in other military equipment. While these transistors are well suited for the jobs they do, they cannot be used for a large number of other applications. The new transistor opens up many new possibilities for militarv technology. “Small” Brain Assists “Giant” Brain.-Something new in electronic computing-using a “small brain” to assist a “giant” in solving complex problems quickly-got underway recently at the United Aircraft Computation Laboratory, East Hartford, Conn. United Aircraft engineers be-
TOPICS
469
gan using a Burroughs Corporation El01 electronic computer, which is the size of an office desk, to pilot the calcutions of a giant robot, which fills a large room, in designing advanced jet engines. Stuart L. Crossman, head of the Computation Laboratory, explained that the Burroughs “small brain” pilot operations are part of a process kno\l,n in the electronic computer field as “tlebugging the program”-checking the accuracy of instructions fed into thr “giant brain.” Mr. Crossman estimated that the use of Burroughs’ El01 will save hard-tofind computer personnel “from several hours to several weeks” in solving the hundreds of complicated mathematical problems involved in the design of aircraft engines and other aircraft components. One of the ElOl’s major attractions is that it does not require highly trained operator personnel. Because of that, Mr. Crossman said, the small computer is “well suited for departments where design and other engineering problems originate but whose personnel have no computer training. The El01 is about as easy as anything can be and still be an electronic computer. It can fit in a small office and gnyone can run it. Engineering Applied to Human Beings.-The principles which engineers have used to build great bridges are now being applied to the human mechanism in solving orthopedic problems. Plans to study the structural and mechanical functions of the bones, joints, and muscles-and the problem of braces and other mechanical aids for the body-have been announced by the INassachusetts Institute of Technology in cooperation with the Massachusetts General Hospital. A $10,000 grant to M.I.T. by the Donner Foundation, Inc., of Philadelphia will finance a two-