INSTRUMENTATION by Ralph H. Mutter
Developments in Electronics THE CLOSE of this year, we wish to ATdiscuss some revolutionary develop ments in electronics which are already beginning to influence instrument de sign. For more than a decade, elec tronic design has been increasingly threatened with what the experts call the "tyranny of numbers." In the early 1950's, an advanced computer contained somewhat over 1000 active devices. By the end of the decade this number had risen to the order of 100,000. Equip ments are now in development with a device count in the many millions. For every active element (tube or transis tor) there are passive devices, inductors, capacitors, resistors, wires, etc. For a long time, we have had microminiaturi zation, in which drastic reductions in size and weight have effected many economies including cost. However, these things cannot be jontinued with out limit and do not evj.de the essential "tyranny of numbers." The inevitable job of assembling, maintaining, and in terconnecting these tiny elements pre sents formidable problems, not the least of which is the matter of reliability. MICROELECTRONICS
As J. A. Morton, Vice President, Bell Telephone Laboratories, Inc., remarked a few years ago: "The aim of elec tronics is not simply to reproduce physi cally the elegance of classical circuit mathematics—rather, it is to perform desired electronic system functions as directly and as simply as possible from the basic structure of matter." In a recent monograph, "Microelec
tronics, Theory, Design and Fabrica tion," (383 + xix pages, McGraw-Hill Book Co., Inc., New York, Ν. Υ., pub lishers, edited by Edward Keonjian), these topics are discussed by fourteen authorities. This book is a remarkable example of a publication devoted to a field, progress in which is so rapid that much of what is described will be ancient history a year from now. Quoting again from the foreword to this book, Morton says: "The func tional device approach exploits our po tential ability to perform electronic cir cuit functions by going directly to the physics of solids without being impeded by classical concepts of circuit elements. Increasingly, we can expect the inven tion and development of physically sim ple single devices which will replace cir cuits having large numbers of classical elements. "A few functional devices have been in use for many years, though not digni fied by that name. The piezoelectric crystal, as a resonator, is equivalent to an assembly of coils, capacitors, resis tors and connections, but nowhere within the crystal can one identify this part as a coil or that part as a capaci tor. In the semiconductor area, newer examples of functional devices are the pnpn and Esaki diodes and the pnpn shift register and counter. With other materials, too, we have demonstrated the feasibility of performing complex logic and memory functions directly in a monolithic wafer of ferrite, cryogenic or ferroelectric material, with corre sponding reductions in individual com ponent—connection count per function."
MOLECULAR ENGINEERING
A closely related discussion, which deals primarily with materials, is to be found in a special report entitled, "Materials for Space-Age Electronics" [Electronics 36, No. 43, 37 (1963)]. Current developments and applications for such materials as gallium arsenide, gallium phosphide, gallium and indium antimonide, indium arsenide, boron ni tride and phosphide, the titanates, and a host of other compounds. These sub stances are not strangers to the chemist but the electronics people have bold plans for their more widespread use in what they call "molecular engineering." The organic chemist is by no means out of this picture. Rare earth chelates such as europium trifluoro thenoyl acetonate have been used as laser materials and made it possible to produce stimu lated emission in liquids and plastics. Pumping energy is absorbed in the or ganic portion of the molecule and trans ferred into the central europium atom to produce the characteristic emission. The current attitude seems to be that one should not look for semiconductive properties per se in organic compounds, but rather to see how they can be used to perform electronic functions. Some of the properties that may be useful are piezoelectric, piezoresistive, photochromatic, electrochromatic, dielectric prop erties, acoustic interactions, and infra red transitions. SEMICONDUCTORS
New tricks are not lacking in the ap plication of semiconductor devices to VOL. 35, NO. 13, DECEMBER 1963 ·
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INSTRUMENTATION
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passive elements. One of the neatest of these is the raising of Q values in a tank circuit (LC) by neutralizing the equiva lent resistance of the tank circuit with a semiconductor negative resistance ele ment. As described by Carl D. Todd [Electronics 36, No. 40, 30 (1963)] such negative resistance elements (NRE) can be paralleled with a tank circuit to neutralize its equivalent resis tance. When the NRE is adjusted for infinite Q, it leads to sinusoidal oscilla tions in the circuit. Editorial comment on this paper suggests that "getting rid of resistance merely by introducing neg ative resistance to cancel it seems so ob vious as to be unreal. It's like a science fiction plot to use negative gravity to hold the space ship aloft, yet for tank circuits it works." As author Todd ex plains, the utility of the scheme resides in the fact that "many resonant circuits require a higher Q than practical LC components can give. This is especially true for the lower frequencies where relatively large inductances are neces sary and where a coil having sufficiently high Q, is often too heavy." Many re finements of the general principle are described among which is the matter of temperature compensation. For one NRE it was possible to obtain stability of the order of 5 parts per million per degree Centigrade over a temperature range o f - 2 0 ° t o + 1 0 0 ° C.
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ANALYTICAL CHEMISTRY
There are constant improvements in precision and size-reduction in electro mechanical devices. A good example is the stepping motor. The device is like a synchronous motor in principle, ex cept that its rotor does not revolve smoothly and continuously when the motor is energized. Instead, on com mand from the input, the rotor travels an incremental step, stops instantly and locks magnetically in position. When a signal of opposite polarity is applied, the rotor advances another precise step, delivering torque in exact proportion to and at the same rate as the input. Sigma Instruments of Braintree 85, Mass., announces an electromagnetic drive of this sort, the Cyclonome, which delivers torque in precise 18° steps at rates up to 1000 steps per second with ρ to 5-inch-ounces of torque with no standby power to maintain high holding torque. It has only one moving part with no catches, ratchets, or escape ments. Sizes are as small as 1 cubic inch and require only the simplest in put circuitry. The device is suitable for chart and tape drives analog-digital converting, impulse counting and, for step servos, in remote positioning and in timing.
