1、EIA TEP137 62 m 3234600 0008337 9 m MAY THE DESIGN- MAXIMUM RATING SYSTEM FOR ELECTRON TUBES FORMULATED BY JEDEC ELECTRON TUBE COUNCIL JEDEC PUBLICATION NO. 37 PRICE $1. 50 c-I3 (9 -._ _ EIA TEP137 62 3234b00 0008338 O FORJ3WORD The purpose of this publication is to present the basic concepts of the
2、 new Design-Maximum Rating System. a brief review of the background which led to the develop- ment of the new system, the principles of the Design- Maximum System as applied to receiving tubes and its application to circuit design will be presented. Finally, specific examples of selected tube applic
3、ation will be included to indicate the proper use of the system. This publication was prepared by JT-5 Committee on Low Power Vacuum Tubes, After Published by ELECTRONIC INDUSTRIES ASSOCIATION Engineering Department 11 WEST and STREET, NEW YORK 36, N.Y. EIA TEP137 62 m 3234600 0008339 2 m THE DESIGN
4、 MAXIMUM RATING SYSTEM POR EL;ECTRON TUEES Table of Contents Page 1 1 5 9 10 13 16 18 21 . Introducbion Definitions of Existing Systems. Principles of the Design-Maximum System* The Application of the Design-Maximum Class A, Small-Signal Amplifiers.o.oaD. *a Class A, Power Amplifiers. Television UHP
5、 Oscillator Power Rectifiers,. Television Horizontal Deflection Circuits.D., . To Circuit Design Evaluation EIA TEP137 62 3234600 0008340 9 INTRODUCTION s - NEED FOR A RATING SYSTEM The conditions under which an electron tube may be operated are limited by fundamental capabilities of the tube itself
6、. Physical limitations exist, for example, in the permissible temperatures at which the various electrodes may be operated, in the amount of current which can be emitted by the cathode, and in the voltage gradients which may be permitted between the various tube elements. Maximum tube ratings have b
7、een established to define these various physical limitations of the tube in terms of readily measurable quantities. The numerical quantities presented as maximum ratings indicate the limiting operating values required to assure satisfactory tube life and performance. Before the value of any rating c
8、an become meaningful, the rating system on which the rating is based must be specfied. The system must define the interpretation required of the numerical values and indicate the procedure necessary to determine whether or not a tube is operating within its rating. Until the present time, two rating
9、 systems have been commonly used in conjunction with receiving tubes, the Design-Center System and the Absolute-Maximum System. The .problems created by their deficiencies have greatly intensified in recenb years primarily as a result of the greatly increased scope of receiving tube applications To
10、overcome the deficiencies encountered with the two rating s stems in current use Maximum System“ has been developed. a new system for rating tubes, designated the x Design- DE3?INLTZONS OF EXISTING SYSTEMS The following definitions have been standardized by the tube industry to describe the two syst
11、ems which have been in common use: Design-Center Rating System Design-Center ratings are limiting valuea of operating and environmental conditions applicable to a bogey electron tube of a specified type as defined by its published data and should no$ be exceeded under normal conditions. The tube man
12、ufacturer chooses these values to provide accept- able serviceability of the tube in average applications mak- ing allowance for normal changes in operating conditions due ta rated supply-voltage variation, equipment component varia- tion, equipment control adJustment, load varlation, gignal - EIA T
13、EP137 b2 W 323Yb00 00083Y1 O W variation, environmental conditions, and variations in the characteristics of the tube under consideration.and of all other electron devices in the equipment. The equipment manufacturer should design so that initially no design-center value for the intended service is
14、exceeded with a bogey tube under normal operating conditions at the stated normal supply voltage. Absolute-Maximum Rating System Absolute-Maximum ratings are limiting values x operating and environmental conditions applicable to any electron tube of a specified type as defined by its published data
15、and should not be exceeded under the worst probable condi- tions. . The tube manufacturer chooses these values to provide acceptable serviceability of the tube making no allowance for equipment variations, environmental variations, and the effects of changes in operating conditions due to variations
16、 in the Characteristics of the tube under consideration and of all other electron devices in the equipment. The equipment manufacturer should design so that initially and thrughout life no absolute-maximum value for the intended service is exceeded with any tube under the worst probable operating co
17、nditions with respect to supply-voltage variation, equipment component variation, equipment control adjustment, load variation, signal. variation, environmental conditions, and variations in the characteristics of the tube under consideration and of all other electron devices in the equipment. I . T
18、o illustrate the meaning of these definitions, let us consider an electronic circuit in which it is desired to determine whether the tube employed is operated within the maximum ratings specified for the tube. If these rtings are presented as design-center ratings, the circuit must be arranged so th
19、at it is operating under normal conditions. That is, the supply voltage is adjusted to its normal value., all components employed are selected as average,values, the equipment controls are adjusted for normal settings, and the tube employed is selected as a bogey tube. Under these average or most ty
20、pical conditions, the circuit voltages, currents, and dissipations are measured in turn under the worst signal condition for each particular rating and compared to the specified design-center ratings. measured value is less than the corresponding rating and if the equipment is not subjected to suppl
21、y voltages in excess of the stated variations, the operation of the tube satisfies the conditions of the design-center system. If each EIA TEP137 b2 = 3234600 0008342 2 W On the other hand, if the ratings are presented as absolute-maximum values, the worst probable operating conditionsmust be establ
22、ished in turn for each item rated. The measurements made with the com- bination of extreme supply voltage, limit components, extreme-control settings, extreme signal, extreme environmental condikions, and any tube which produces tihe worst probable value for the particular rat- ing under considerati
23、an, is compared to the specified absolute-maximum rating, Under these adverse conditions, if each measured value is. less . than the corresponding rating, the operation of the tube satisfies the conditions of the absolute-maximum system. . . O These two rating systems differ significantly in the fou
24、r following aspects: 1, The operating conditions employed in determining whether the tube is operated within maximum ratings 2, .The characteristics of the tube employed in determining-whether the tube is operated within maximum ratings 3. The permissible exccss of the specified values of the maximu
25、m ratings (Under the absolute-maximum system no excess of the rated value is permitted, while under the design-center system the rated value may be exceeded with adverse operating condit3.ons. ) The assignment of basic responsibility for proper tube usage. (With the design-center system, the tube ma
26、nufacturer effect- ively assumes the responsibility for the effect that both variations in tube characteristics and circuit operating con- ditions will have on tube performance. On the-other hand, under the conditions imposed by the absolute-maximum system, the complete responsibility for varialxlon
27、s in tube character- istics and operating conditions is assigned to the circuit designer. ) 4. e DIFFICULTIXS WITH EXISTING SYSTEMS Although the design-center system provides the cirouit designer with an extremely convenient and usable system, it has the rather severe . disadvantage that the degree
28、of protection afforded the tube is variable and depends on $he circuit and environmeiital operating con- ditions Historically this limitation was not par$icularly significant, The great majority of tubes produced were used in radio receivers which involved essentially standard circuits. Hence the tu
29、be manufacturer could be reasonably certain of the effects that a specified line voltage variation would have on the currents, voltages, and dissipa- tions associated with the various tubes employed, . EIA TEP137 62 m 323Yb00 0008343 4 W In recent years, however, electronic circuits have become more
30、 complex and more diversified. The circuits employed operate under widely different degrees of feedback and supply voltage regulation. As a result a fixed relationship no longer .exists between the variations in supply voltage and variations to which the tube is subjected. Two extreme examples in th
31、is consideration would be the computer applica- tion and the television high-voltage rectifier application. o fn the computer, particular attention is paid to the regulation of heater and plate voltages. Hence normal fluctuation in the supply have little if any effect on tube operating conditions. I
32、n the case of the TV flyback fiigh-voltage rectifier, the entire input power including the filament requirements is derived from the horizontal deflection amplifier. All variations in the horizontal zontal- amplifier circuit which can result from variations in sweep tube characteristics, damper tube
33、 characteristics, output transformer and other components, and supply voltage, are imposed as variations in the filament power and inverse voltage of the high-voltage rectifier tube, Furthermore the output current required is established by settings of the brightness and contrast controls which in t
34、urn depend on the ambient light level of the room in which the receiver operates. Al1 of these various sources contribute to the extreme variations associated with high-voltage rectifier operation. These two examples illustrate the fact that the variations in operating conditions to which a tube can
35、 be subjected cannot necessarily be controlled by specifying a permissible variation in supply voltage. o Figure 1 illustrates qualitatively the variation of plate dissipation to which a bogey tube could be subjected in three different circuits, each of which is designed for operation at 100 percent
36、 of the maximum- design-center dissipation rating, In each case, the circuit is subjected to + 10 percent line voltage variations, The figure illustrates that the degFee by which a design-center rating can be exceeded is a function of the circuitand equipment in which the tube is operated, These con
37、siderations indicate that there are at least two disadvantages to the deaign-center system: 1. The tube manufacturer is not adequately protected. His tubes can be operated within the conditions of the design-center system and yet be subjected to severe operating conditions as typified by Condition C
38、 of Figure 1, The design-center system could adequately protect the tube only if standard circuits were used in which known operating .variations are encountered. 2. lhe conservative circuit designer is penalized under the conditions of the design-center system, The system requires only considera- t
39、ion of average operating conditions; no requirements are placed on permissible variation under adverse operating conditions, Con- sequently, no incentive is provided for circuit design which tends he must accept full responsi- . bility for the effects of variations in tube characteristics and varia-
40、 tions in any possible circuit operating conditions. The absolute- maximum system assigns this entire responsibility to the circuit designer, A more logical division of these basic responsibilities would be to assign the effect of the variations in tube characteristics to the tube manu- facturer and
41、 to assign the effects of variations in circuit operating conditions to the equipment manufacturer. This philosophy is incorporated in the Design-Maximum System. The design-maximum system requires that the maximum ratings be checked with bogey tubes rather than limit tubes. In this way, the responsi
42、- bility for variations in tube characteristics is effectively assigned to the tube manufacturer. The task of the circuit designer in determin- ing conformance to the maximum ratings is greatly simplified, and the tube manufacturer is relieved of the almost impossible responsibility for supplying li
43、mit tubes to the circuit designer for his maximum rating evaluation, This system also requires that the specified maximum ratings not be exceeded when the circuit is so arranged that the bogey tube is operated undep.the worst probable conditions. In this way the responsibility for variations In oper
44、ating conditions is effectively assigned to the circuit designer. He must realistically anticipate the worst probable operating conditions likely to be encountered for each tube in his equipment. In a television receiver, for example, it.is possible - partlcularly at high line - to exceed some of th
45、e ratings in certain stages by very great amounts when the controls are completely maladjusted. However, if the maladjustment of controls makes the picture unusable, the probability of this condition occurring for a prolonged period is remote as the receiver would normally be turned off. The w0rs.i;
46、 probable operating conditions resulting from control setting would occur when the controls were maladjusted only to the extent that a minimum usable picture could still be obtained. Another example of worst probable conditions occurs in the case of rectifier output current. In this case, particular
47、ly if the load consists of an appreciable number of tubes, tha difference in output current required between the probable high load and the theoretical maximum load is very large. Again the significant value from the standpoint of proper usage of the rectifier tube is the worst probable Load current
48、, Therefore, under the design-maximum sys tern, the tube manufacturer in effect suppliea the circuit designer with maximum limiting values based on bogey tubes, Because some variation in circuit operating conditions is present in any practical circuit, the equipment manufacturer muat design his equi
49、pment below the design-maximum values so that no one of these ratings will be exceeded under the worst probable operating conditlons which will. be encountered, The degree.to which the circuit EIA TEP137 b2 = 3234b00 0008346 T must be designed below the design-maximum ratings depends on the extent to which the variables are controlled in the equipment. Inherently, the proposed design-maximum system requires that the circuit designer anticipate the adverse conditions to which his equipment will be subjected. The circuit designer is the person to whom this res- .p
