Siekanowicz: Traveling- Wave Tube for Relay Service

Bowman, CBS-Hollywood director of technical opera-tions, and H. W. Pangborn, CBS-Hollywood manager oftelevision operations, for their constructive advice andover-all guidance of the project; to K. S. Tyler, managerof CBS Television building construction for the very im-portant team spirit which was engendered between con-

struction and facilities groups, to our colleagues in theCBS Television Engineering Department, and to J. B.French, CBS-Hollywood manager of technical con-struction and maintenance, without whose vigorous on-the-job direction completion of the installation in recordtime would not have been possible.

A Developmental Medium-Power Traveling-Wave Tubefor Relay Service in the 2,000-Megacycle Region*

WIESLAW W. SIEKANOWICZt, ASSOCIATE, IRE

Summary-This paper describes an experimental 2,000-mega-cycle traveling-wave power amplifier designed for operation at elec-trode voltages below 700 volts. This tube is capable of delivering apower output of 7.6 w at a gain of 20 db and a power output of 3 wat a gain of 28 db at the optimum operating point. Maximum poweroutputs from 4 to 7.6 w at gains ranging from 17 to 21 db have beenmeasured over a bandwidth of 650 mc (1,700 to 2,350 mc). Elec-tronic efficiencies of 20 per cent and collector efficiencies close to 30per cent have been obtained with this amplifier. Results obtainedwith the tube operating as a frequency shifter are discussed. A de-sign including a permanent magnet for electron-beam focusing hasbeen developed.

INTRODUCTIONT HIS PAPER DESCRIBES a developmental

T 2,000-mc, medium-power, low-voltage, traveling-wave tube, illustrated in Figs. 1 and 2, designed

primarily for use in the output stage of microwave relaytransmitters. The development of this traveling-waveamplifier, started at the RCA Laboratories by Kaisel,'was undertaken in an effort to provide better perform-ance in such applications than that obtainable from tri-odes and klystrons. This tube is also useful in frequencyshifter or intermediate-stage-amplifier applications.

In the development of the traveling-wave amplifier,emphasis has been placed not only on electrical charac-teristics but also on achieving a satisfactory mechanical

design. Efforts have been made to produce a tube whichis shorter and more rugged than early experimentaltypes. The following brcad objectives have been takeninto consideration:

Fig. 2-View of traveling-wave power amplifier with permanentmagnet and helix-to-coaxial-line transducers.

Fig. I-Developmental 5-w 20-db traveling-wave tube for relay service in the 2,000-mc. region.

* Decimal classification: R339.2. Original manuscript receivedby the Institute, November 27, 1953.

f Tube Div., RCA, Harrison, N. J.'W. J. Dodds, R. W. Peter and S. F. Kaisel, "New developments

in traveling-wave tubes," Electronics; February, 1953.

(a) Power output of at least 2.5 w.(b) Gain of at least 20 db.(c) Frequency range of 1,750 to 2,250 mc.

1954 1091

1 RPROOCPEDINGS OF, THEPRI-PRJ

(d) Operation at electrode voltages below 70() v.<e) Coaxial input and output connections.'f; A packaged design including a permanent magnet

to focus the electron beam.[tems (d) and (f) of this list are of great importance in

the application of the tube. Considerations of cost, re-liability, and maintenance make it desirable to operatemicrowave relay links at low voltages. The use of apermanent magnet is desirable to eliminate bulky,power-consuming solenoids.A helix-type circuit used in the traveling-wave ampli-

fier satisfies the electrical specifications and lends itself,in this case, to a compact mechanical design. The volt-age, frequency, and gain requirements are such that ahelix about three inches long is necessary. With an airgap of this order, it is possible to use a conventional"U"-type magnet weighing from 10 to 15 pounds.Severe requirements have been imposed on the elec-

tron gun. Because the efficiency of the tube is about 20per cent, a high-current beam has to be generated at alow voltage. In addition, mechanical constructien of thegun must be suitable for use with a permanent magnet.

WMide-band helix-to-coaxial-line transducers havebeen designed to feed energy into and out of the ampli-fier. The optimum dimensions and location of the at-teriuator used to prevent the tube from oscillating havebeen determined by experiment to prevent regenerationanid to obtain maximum power, gain, and efficiency.

TUBE COMPONENTS

Helix AssemblyThe helix, designed according to the theory described

by J. R. Pierce,2'3 consists of 0.010-inch tungsten wirewound at a pitch of 0.0184 inch; its inner diameter is0.120 inch. With this helix and the beam produced bythe electron gun which will be described later, the gainparameter, C, referred to by Pierce is about 0.15 at acollector current of 50 milliamperes. The main featuresof the tube assembly are shown in Fig. 3. Three ceramicrods used as supports for the helix are held in positionby clamps welded to the matching cylinders. The an-tennas and the matching cylinders are components ofthe input and output coupling circuits. The last twoturns at both ends of the helix are stretched to provide asmoother transition to the straight antenna and thus toimprove the match.The electron gun and the helix assembly comprise a

unit structure centered with respect to the collector.The collectcr fits into the aligning elements located inthe pole pieces, as shown in Fig. 3. In this manner, theelectron gun and the helix are in the right position forbeam focusing when the tube is inserted into the mag-net. The structure is rugged and easy to construct, andpermits a high pumping rate during the exhaust opera-

2J. R. Pierce, "Traveling-Wave Tuibes," D. Van Nostrand Co.,Inc., New York, N. Y., 1950.

3 J. R. Pierce, "Theory of the beam-type traveling-wave tube,"PROC. I.R.E., vol. 35, pp. 111-123, February, 1947.

tion. l)ielectric loading is kept to a minimum, and at-tenuattion can be conveniently applied directly to thehelix.

MATCHING

Fig. 3 Schematic diagram of traveling-wavepower amplifier assembly.

Electron Gun

The magnetically confined, "parallel-flow" electrongun used in this tube is mechanically simple and satis-fies the electrical requirements. Because the gun struc-ture does not provide beam convergence, the mean cur-rent density at the cathode is practically the same asthat of the beam. With this design, it is possible to ob-tain a high perveance [collector current/(positive elec-trode voltage)3/2] and to make the components of thegun small. A perveance of approximately 5 X 10-6 am-peres per (volt)312 is necessary because of the compara-tively low voltage requirement and the fact that theelectronic efficiency of the tube is about 20 per cent.

SECOND ELECTRODE(ANODE)

.100"

/*

"I NSULATOR

Fig. 4 Diagram of the electron gun.

The electron gun, shown in Fig. 4, has been designedaccording to the method described by J. R. Pierce.4 Thecathode used in this gun has a diameter of 0.090 inch.Two electrodes are used to focus the electron beam. Thefirst electrode is usually maintained at the same poten-tial as the cathode. The second electrode, or anode, ispositive with respect to the cathode. In the develop-ment, it was assumed that the space-charge conditionsare the same as those in a parallel-plate diode. The

I J. R. Pierce, "Theory and Design of Electron Tubes," D. VanNostrand Co., Inc., New York, N. Y., 1949.

1092 July

Siekanowicz: Traveling- Wave Tube for Relay Service

electrodes are shaped to cause the potential along thebeam boundary to vary as the 4/3 power of the distancefrom the cathode. This type of potential distributionmaintains the boundaries of the electron-beam parallel.

In this design, the cathode of the electron gun isusually in the magnetic field. Even in the absence of amagnetic field, however, the current intercepted by theelectrodes is negligible provided the potential of thehelix is higher than that of the second electrode.The mechanical construction of the electron gun per-

mits the use of small radial dimensions. This feature isdesirable because the tube has to fit inside the magnetpole pieces. The diameter of the holes in the pole piecesshould be as small as possible so that the necessary fieldstrength and uniformnity can be obtained.

Helix-to- Coaxial-Line Transducers

The construction of the helix-to-coaxial-line trans-ducers is shown in Fig. 3 and in the upper right-handcorner of Fig. 6. In the development of these trans-ducers, it was desired that they should not add to theaxial length of the tube. This objective was achieved by"folding back" such components as the antenna and thematching cylinders over the ends of the helix, as shownin Fig. 6. With this design, other elements, such as theelectron gun and the collector, can be placed close tothe helix assembly without absorbing energy from it.Because the spacing between the collector and the out-put end of the helix is small, it is possible to use a col-lector voltage lower than that of the helix without re-ducing the power output. As a result, collector efficien-cies [(rf power output X 100) /(collector voltage Xcollec-ter current) ] of 30 per cent have been obtained.

The rf power is fed into the helix from the antenna,which is energized through the gap "G," as shown inFig. 3. The desired impedance match is obtained byadjustment of the front plunger to provide the properwidth of the gap "G" and by suitable location of theantenna with respect to the gap.

FREQUENCY-MC

Fig. 5-Characteristic of voltage standing-wave ratio vsfrequency for helix-to-coaxial-line transducers.

Fig. 5 shows a curve of the voltage standing-waveratio with respect to frequency for the helix-to-coaxial-line transducers. In these measurements, an attemptwas made to obtain a voltage standing-wave ratio of lessthan 2 over as wide a frequency range as possible.Standing-wave ratios of less than 1.8 were measuredover a bandwidth of 1,000 mc, and ratios below 3 over abandwidth of 1,300 mc.

In many applications, very low standing-wave ratiosare required over a narrow bandwidth. Tests have beenmade to determine whether the type of helix-to-coaxial-line transducers described above is suitable for use insuch applications. The results of these tests are shown inFig. 6. For the curves at the bottom of Fig. 6, an at-tempt was made to obtain standing-wave ratios of about

FREQUENCY -Mc

Fig. 6 Characteristic of voltage standing-wave ratio vs frequency for helix-to-coaxial-line trans-ducers. This figure shows the bandwidths over which standing-wave ratios of approximately 1.1or better can be obtained.

1954 1093

PROCEEDINGS OF THE I-R-E

Fig. 7-Demountable exhaust system and testing equipment.

1.1 over as wide a frequency band as possible. Standing-wave ratios of less than 1.12 were obtained over band-widths of 100 and 185 mc for curves "B" and "D," re-

spectively.

The curves at the top of Fig. 6 show the results oftests to obtain standing-wave ratios of less than 1.1. Itcan be seen that standing-wave ratios of less than 1.07have been realized over bandwidths of at least 50 mc.

A ttenuator

Because most traveling-wave tubes of the helix type

show a strong tendency to oscillate, an attenuator isused to prevent this condition. For good results, theattenuator should introduce very small reflections, becapable of dissipating the power, and be thoroughly de-gassed. Aquadag,i deposited on a ceramic rod, is used toprovide the required loss characteristic. A "cold" inser-tion loss of about 40 db is necessary for the traveling-wave amplifier described in this paper. The dimensionsand the location of the attenuator, which were deter-mined by experiment, are shown in the upper right-hand corner of Fig. 8.

5 Trademark registered by Acheson Colloids Co., Port Huron,Michigan.

EXPERIMENTAL RFSULTS

Experimental Techniques

Preliminary evaluation of circuits was carried out ina continuously pumped demountable system,6 shown inthe center of Fig. 7. The use of the demountable systemeffects a considerable reduction in the amount of timerequired for tube development. The tube and associatedcircuits are mounted on plates and sealed in the openingsin the sides of the cubical test chamber. In case of failureof the tube under test, the test chamber can be isolatedfrom the diffusion pump by means of a valve, and theassembly can be removed quickly and easily for repairs.The repaired assembly, or a new assembly, is thenmounted in the test chamber, and the chamber is ex-hausted rapidly by means of a mechanical pump. Thevalve separating the test chamber and the diffusionpump is opened and an adequate vacuum for tube opera-tion is obtained within a few minutes from the time ofmounting the new assembly. In this manner, a largenumber of structures can be evaluated in a much shorter

6 T. M. Shrader, "A demountable vacuum system for electron-tube development," Proc. of the National Conference on Tube 'I'ech-niques sponsored by the Panel on Electron Tubes, October, 1953.

1094 July

Siekanowicz: Traveling- Wave Tube for Relay Service

time than would be possible if each tube had to beexhausted and sealed before test. A solenoid was usedin the demountable system to produce the magneticfield for focusing the electron beam. Results shown inFigs. 8 through 13 were obtained in the demountablesystem.

FREQUENCY (MC) =2000MAGNETIC FIELD STRENGTH

(GAUSSES)n 1100

30r

25

un20lL

coIz

a 151

5

0

MAX. SMALL- ,,SIGNAL GAIN

/o

GAIN AT MAX.POWER OUTPUT

{ 800HELIX VOLTS FORMAX, POWER OUTPUT

'~ 1600,,-- HELIX VOLTS FOR MAX. o

If SMALL-SIGNAL GAIN >

! ~~~~~~400x

I

20020 40 60 80

COLLECTOR MILLIAMPERES

-1 4 3.. ATTENUATOR4 HELIX

123

II.

ZOLA

Lit

Fig. 8-Gain, power output, efficiency, and optimum helix voltagesvs collector current. Solid lines indicate large-signal character-istics; dashed lines indicate small-signal characteristics.

Tube CharacteristicsFig. 8 shows the power output, the gain, and the opti-

mum helix voltages as functions of the collector currentfor the traveling-wave amplifier. These measurementswere taken at a frequency of 2,000 mc. The maximumpower output shown in Fig. 8(b) can be obtained at a

given collector current by optimum adjustment of thedriving power and the helix voltage. The tube can de-liver a power of several watts at a gain of about 20 db,depending on the current. The maximum obtainablepower, P, can be expressed empirically as follows:

P = 0.037 (collector current in milliamperes)131.

The electronic efficiency of the tube given in Fig. 8(b)[(rf power X 100)/collector current Xhelix voltage)] isapproximately 18 per cent at collector currents rangingfrom about 20 to 50 ma, and increases to 20 per cent at65 ma.

The maximum small-signal gain at 54 ma is 29 db, as

shown by the upper dashed curve in Fig. 8(a). The helixvoltage for maximum low-level gain is less than thevoltage for maximum obtainable power output. Opera-tion below 700 v has been achieved at both levels ofoperation.The rf power output of the traveling-wave amplifier

is shown as a function of the rf power input in Fig. 9.The bottom curve, A, in this figure was obtained withhelix voltage and the driving power adjusted for maxi-mum obtainable power output at a constant collectorcurrent. A maximum power output of 7.6 w was ob-tained at a gain of 20 db. The gain at the helix voltagecorresponding to the maximum obtainable power outputwas found to increase as the input power was reduced,reaching 24 db at small signals and remaining practically

constant for power outputs to about 4 w. Operation ofthe tube under the conditions used for these curves issuitable in applications where sufficient driving power isavailable and a high power output, achieved at some

loss in gain, is desired.When a high gain is preferable to maximum power

output, operation before the saturation point is recom-mended. The dashed curves in Fig. 9 were obtained byreducing the driving power and adjusting the helixvoltage, shown in the center curve, for maximum power

output. It can be seen that the tube delivered 5 w ofpower at a gain of 26 db, 3w at 28 db, and lw at 29 db.

U,

13n

a8I30

w

00.

4

FREQUENCY (Mc)=1900_ COLLECTOR MILLIAMPERES-54(POWER OUTPUT -%.AS SHOWN IN _ _CURVE B) _.

I

GAIN(POWER OUTPUTAS SHOWN INCURVE A)

en - -700FHELIX VOLTS FOR

O MAX. POWER OUTPUT600>

500-ai

XI

-POWER OUTPUT(HELIX VOLTAGEADJUSTED FORMAX. OUTPUT )el,)

.t 7

oL0.0 0.01

RF POWER INPUT-WATTS0.1

24

C)

-Jw

16

zIZi(D

Fig. 9 Rf power output and gain vs rf power input. Helixdimensions and attenuator position as in Fig. 8.

2000FREQUENCY-MC

Fig. 10-Rf power output and gain as functions of frequency.Helix dimensions and attenuator position as in Fig. 8.

Fig. ro shows the gain and power output of the tubeas functions of frequency. The top curve in Fig. 10shows the gain when the power output is adjusted to 2.3w at each frequency. The maximum gain in the center ofthe frequency band was 28 db; the gain dropped to21 db at 2,360 mc and to 25 db at 1,670 mc.

The maximum obtainable power output and the cor-

responding gain are shown in the lower curves in Fig. 10.Maximum obtainable power outputs ranging from 4 to7.6 w at gains from 17 to 21 db were measured over a

WER OUTPUT(HELIX VOLTS=670)

1954 1095

lb l l -A |i?

z i 1 ---ldl-

l. l4

- 'I i1

I

_

DiIC

PROCEEDINGS OF THE I-R-E

frequency band from 1,700 to 2,350 mc. These resultswere obtained at a constant collector current.A collector efficiency higher than the electronic effi-

ciency can be obtained by the use of a collector voltagelower than that of the helix. The use of as low a collectorvoltage as possible is desirable to keep the power dis-sipated on the collector low. Fig. 11 shows the variationin power output and collector efficiency, with collector

16 50bFREQUENCY (Mc)=2000POWER INPUT (MILLIWATTS) =38 z

wCURVE COLLECTOR HELIX MAGNETIC FIELD U

14 _ MILLIAMPERES VOLTS STRENGTH (GAUSSES) 4IO50 640 870

2 44 630 870 w12 ~~~334 600 840>

12 3)0 U a-,z>

4 28 590 840 1O

H 4 X L

U) _ ,2300 400 500 600 700 800 900 iOOO0

a. 8.H0 U0L0 -J

~~~~~~~~~~~~~00~~~~~~~~~~~~~~~~~~

2-

300 400 500 600 700 800 900 1000COLLECTOR VOLTS

Fig. t1 Rf power output and collector efficiency as functions ofcollector voltage. Helix dimensions anid attenuator position as inFig. 8.

voltage. The data for the curves of Fig. 11 were ob-tained with constant collector currents, magnetic fieldstrengths, and helix voltages. At each value of collectorcurrent, the helix voltage and the driving power wereadjusted for maximum power output with the collectorabout 200 v positive with respect to the helix. The

POWER INPUT (MILLIWATTS)=50FREQUENCY(Mc)=2000

5

U)

<4

1--

F-

0

3i2 0 : / -

0T

400 450 50u 550 600HELIX VOLTS

Fig. 12 Rf power output as functconstant collector ct

curves indicate that the power

tially constant until some mininvoltage, depending on the collectat that point, a rapid drop in powCurves 1 and 3 in Fig. 11 show th

of 50 and 34 ma reductions in collector voltage of 120and 160 v, respectively, do not reduce the power output.At power-output levels from 3 to 6.5 w, maximum col-lector efficiencies from 23 to 29 per cent were realized.These results were obtained at magnetic field strengthsfrom 840 to 870 gausses.

Fig. 12 shows the power output as a function of thehelix voltage for three values of collector current. It can

be seen that the "3-db voltage bandwidth" at the cur-

rent of 44 ma was 230 v.

Results shown in Figs. 8 through 12 were obtained bymaintaining the first electrode at the cathode potentialand by drawing the current with the positive potentialon the second electrode.An appreciable improvement in gain and efficiency

can be achieved by an increase in the current density inthe region where the axial component of the rf electric

t) --- X --- X - - 3 232HELIX VOLTS-680 lCOLLECTOR MILLIAMPERES=30 v

u

5 [ 28 a-a.

<4 24 U2

U-

H Ur0

0

cc-(ui2 -G~~~~~~~AIN 16_i:3

0

0 20 40 60 80 100 120 140FIRST-ELECTRODE VOLTS

Fig. 13-Rf power output, gain, efficiency, and helix voltage as func-tions of first-electrode voltage. Collector current held constant at30 ma by adjusting the second-electrode (anode) voltage. Helixdimensions and attenuator position as in Fig. 8. This test wasperformed on a different assembly than the one used to obtainresults shown in Figs. 8 throtugh 12.

field is of high amplitude. Because the field inside the

\____ helix increases with the radius,2'4 the interaction be-tween the ele,ctron beam and the field can be improved

-< as_ by the application of a positive voltage to the firstelectrode to produce a current-density distributionalong the cross section of the electron beam which also

increases with the radius. The results obtained by opera-

\ \ _> _ tion of the electron gun in this manner are shown inFig. 13 With a collector current of 30 ma and the first

electrode at cathode potential, the output was adjusted650 700 750

800 initially to 3.1 w. The curve of power output vs the first-

Lion of helix voltage at electrode voltage, with the collector current maintainedurrents. at a constant value by adjustment of the second-

electrode (anode) voltage, shows that the power in-output remains essen- creases with the first-electrode voltage. The output was

num value of collector 40 per cent higher with a first-electrode voltage of 110

tor current, is reached; v than with voltage of zero.

rer output is noticeable. A summary of the performance data obtained in theiat at collector currents demountable system in Fig. 7 is given in Table I.

1096 July

[[11111 :1"

Siekanowicz: Traveling- Wave Tube for Relay Service

below 700 v54 ma800 to 900 gausses4 to 7.6 w at 17 to 21 db gain

measured from 1,700 to 2,350mc

7.6 w at 20 db gain at 1,900 mc

28 db29 db

Frequency-Shifter Application

The theoretical considerations and actual operation ofthe traveling-wave amplifier as a frequency shifter havebeen descrjbed by W. J. Bray.7 A suitable circuit for thistype of operation is shown in Fig. 14. Results obtainedwith a sealed-off tube operating in this circuit are

900-McCARRIER INPUT

CARRIER PLUSSiDEBAND

COMPONENTS

Fig. 14 Circuit diagram for operating the traveling-waveamplifier as a frequency shifter.

1800 TlCOLLECTOR MILLIAMPERES=35HELIX VOLTS=660CARRIER FREQUENCY (Mc)=1900

1600 CARRIER POWER INPUT

(MILLiWATTS) =30MODULATING FREQUENY (Mc)=70

1400lTO 2800 MILLIWATTS AT

0 ZERO MODULATING VOLTS

$1200

2,>1000 AT1830-Mc FIRST-

800 ORDER SIDEBAND0

1970-MC FIRST-cc 600 t tkORDER SIDEBAND

~:600-a. \ l 1760-Mc SECOND-

ORDER SIDEBAND

400

2040-Mc SECONID-ODRSIDEBAND

2000

0 20 40 60 80 100 120

RMS MODULATING VOLTS

Fig. 15 Power output of carrier and sideband components as

functions of sinusoidal modulating voltage.

7W. J. Bray, "The traveling wave value as a microwave phase-modulator and frequency-shifter," Proc. Inst. Elec. Eng., vol. 99,part 3; January, 1952.

shown in Fig. 15. In this type of application, the cathodeand the focusing electrodes of the electron gun are effec-tively grounded at the modulating frequency of 70 mcand the modulating voltage is applied to the helix.The operating conditions used to obtain the results

shown in Fig. 15 are given at the top of the figure. Itcan be seen that the first-order lower sidebands reacheda maximum at the modulating voltage of about 27 v(rms). The conversion gain (sideband power output/car-rier power input) for the first-order sidebands is ap-proximately 11.7 as compared to a gain of 19.6 db whenthe tube is operated as an amplifier. The first-orderlower sideband is thus 7.9 db lower than the amplitudeof the unmodulated carrier. Complete suppression ofcarrier occurred at modulating voltage of 44v (rms).

"PACKAGED" DESIGN

An important feature of the traveling-wave amplifier,shown in Fig. 1, is the uniform diameter of the glassenvelope. This design was possible because of the smalldiameter of the electron gun and the "folded back" de-sign of the helix-to-coaxial-line transducers. This con-struction adds greatly to the mechanical strength of thetube, and eliminates the use of long and fragile glasstubing such as that used to support the helix in earliertraveling-wave tubes. Outside diameter of the envelopeis 0.700 inch, and total length of tube 8' inches.The "packaged" design is shown in Figs. 2 and 3. The

supports for the matching circuits are omitted in thesefigures for the sake of clarity. The tube is self-aligningin the permanent magnet, as described previously inconnection with the helix assembly. The magnet illus-trated weighs 13.5 pounds and produces a field of 850gausses on the axis of the tube. Circular discs are at-tached to the pole pieces of the magnet to improve theuniformity of the field.The performance of sealed-off tubes has been similar

to that obtained in the demountable vacuum system.Results with the permanent magnet, however, havethus far been somewhat inferior to those realized withthe solenoid. The power output has been about 30 percent less and the gain approximately 2 db lower. Thedifference in performance is believed to be due to thefact that the field in the permanent magnet is not as uni-form as that in the solenoid. It is expected that suitableshaping of the pole pieces and discs will make it possibleto obtain a more uniform field.

ACKNOWLEDGMENT

The author wishes to give credit to the RCA Labora-tories in Princeton, N. J., and in particular to S. F.Kaisel, former member of the RCA Laboratories, fororiginal development work on the traveling-wave ampli-fier, to the Advanced Development Group of the RCAEngineering Products Division in Camden, N. J., forevaluation of the tube as a frequency shifter, and toB. B. Brown, H. K. Jenny, and other members of theRCA Tube Department, for their contributions to thedevelopment of the tube described in this paper.

TABLE I

VoltagesCollector CurrentMagnetic FieldMax. Obtainable Power Output

At Optimum Operating Point:Max. Power OutputGain at Power Output of

3 wSmall-Signal Gain

1954 1097