366 PHILlPS TECHNICAL REVIEW VOLUME 31

Integrated circuit with Hall device for brushless d.c. motors

Magnetic field strengths are often measured withHall devices made from the semiconducting materialsindium arsenide or indium antimonide. We have nowmade Hall devices from silicon, using the usual technol-ogy for producing integrated circuits with bipolartransistors 11] 121. Although a silicon Hall device has alower sensitivity than devices made with the materialsmentioned above, it offers the great advantage that itcan be manufactured by an existing method of quantityproduction. ln any case the loss of sensitivity can beamply compensated by incorporating the Hall devicein an integrated circuit which amplifies the Hall volt-age. A further advantage of using silicon technologyis that extremely small devices can be made (with asensitive area down to 10 X 10 fLm).

We have developed Hall devices with amplifier foruse as magnetic sensors in a brushless d.c. motor. Insmall d.c. motors of the conventional type the statoris generally a permanent magnet which provides therequired magnetic flux, and the rotor is fitted with coilsto which the current is supplied through the brushesand the rotating commutator. The disadvantages ofthis type of motor are commutator wear, undesirablenoise (particularly undesirable in sound recording andreproduction equipment) and high-frequency inter-

r---- i)s~: L~II

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Fig. I. Controlling a brushless d.c. motor by means of Halldevices. When the north pole of the permanent magnetic rotor Ris close to the Hall device HI, one of the electrodes of the Halldevice supplies a positive voltage which keeps the switch SIclosed (in the actual circuit, switches SI to S4 are transistors).The stator coil Li is then energized. A quarter of a revolutionlater, coil L2 is energized by Hall device H2, and a further quarterof a revolution later coil L3 is energized by Hall device HI, whichis now close to the south pole of the rotor.

1970, No. 11/12 HALL DEVICE FOR BRUSHLESS D.e. MOTORS 367

ference. These disadvantages can be avoided by usinga permanent magnet for the rotor, which is diametric-ally magnetized, and by incorporating the coils in thestator. They can then be supplied with current at theright moments by means of an electronic switchingsystem. A device is then needed, however, for sensingthe position of the rotor. Hall devices are particularlysuitable for this purpose, and have already been usedfor this application [31. A possible basic circuit is showninfig. I.

Usually the Hall devices are mounted in recesses cutinto the stator. We have avoided the necessity for suchrecesses by mounting the devices at the head of therotor.

Fig. 2. Diagram of the Hall circuit, drawn to correspond withthe pattern of the integrated circuit. The value of the resistors isgiven in ohms.

Fig. J. The integrated Hall circuit in a plastic encapsulation. Tapered recesses at both endscontain pole pieces for increasing the magnetic flux density in the device. In the motor thatwe have developed this is about 0.6 T (I T = 104 gauss). The devices are made in strip formand later punched out.

The Hall device which we have developed for thisapplication is shown in the title photograph; thedimensions are about 1.5 X I mm. There are six NPNtransistors and seven resistors in the circuit. The actualHall device in the middle is surrounded by a clearlyvisible P+ isolation diffusion. Two of these chips switchfour discrete transistors which energize the stator coilsof the motor. The diagram of the Hall circuit is givenin fig. 2.

The integrated Hall devices are used in d.c. motorsintended for semi-professional tape recorders. Thedevices are contained in a plastic standard encapsula-tion which in this case, however, has tapered recesseson both sides into which pole pieces are fitted toincrease the flux density (fig. 3). A cut-away photo-graph of the motor is shown in fig. 4; the two Halldevices (see the arrows) are mounted on a printedwiring board together with their output leads.

Another possible application of a Hall device withintegrated amplifier is a cl ip-on probe; other applica-tions might be found in cases where a mechanicaldisplacement has to be converted into an electricalsignal, such as the keyboard of an electric typewriter [41,

or a tachometer.In addition to the Hall circuit shown in the title

photograph, a small Hal! probe made from silicon hasbeen developed (fig. 5) for magnetie-field measure-ments at locations where access is difficult. This Hall

[1] G. Bosch, A Hall device in an integrated circuit, Solid-StateElectronics 11, 712-714, 1968.

[2] A. Schrnitz, Solid circuits, Philips tech. Rev. 27, J92-J 99,1966.

[3] W. Dittrich and E. Rainer, Siemens-Zo 40, 690, 1966.Another method of position sensing, using ferrite cores, wasdescribed by W. Radziwill in Philips tech. Rev. 30, 7, 1969.

[4] R. H. Cushman (Ed.), Hall effect put in IC, Electronic DesignNews, 11 Nov. 1968, p. 87.

368 PHILlPS TECHNICAL REVIEW

probe is not combined with an amplifier. Apart fromthe advantages of silicon Hall devices mentioned earlier,such as small dimensions, this probe has the additionaladvantage that for the small thickness required in thiscase (0.1 mm) a silicon single crystal is not so fragile asthe insulating substrate (e.g. of aluminium oxide) whicha Hall device of indium antimonide requires. Moreoverthe silicon device is linear up to higher field strengths.

The dimensions of the silicon chip are 12x 1.5x0.1 mm; the actual Hall device on the chip (dimensions1.5 X I mm) is surrounded by a p+ isolation diffusionin the same way as the "islands" in an integrated

VOLUME 3I

Fig. 4. Cut-away view of our"Hall motor". The Hall devices(white arrows) are mounted on aprinted wiring board, to whichthe lead-out pins are also at-tached. The motor takes about7 watts at a speed of 2000 revfmin. Speed control is effected bya transistor outside the drivingcircuit.

Fig. 5. Hall probe. The rectan-gular Hall device (1.5 x 1 mm)can be seen at the end of thesilicon chip.

circuit. The contacts, like the collector contacts in anintegrated circuit, are N+. The sensitivity at a supplyvoltage of tOY is about O.75VjT (lT (tesla) = t04

gauss).

G. BoschJ. H. H. Janssen

Ir. G. Bosch and Ir. J. H.{H. Janssen are with the Philips Radio,Television and Record-playing Equipment Division, Eindhoven.

1970, No. J 1/12 369

Objects of glassy carbon

Anew solid modification ofcarbon that is verydiffer-ent in some ways from diamond and graphite, theknown modifications, has been prepared by means ofa synthetic method [lJ. This "glassy" carbon is obtainedby decomposition (pyrolysis) of appropriate polymers,such as phenol-formaldehyde resins. In its physicalproperties glassy carbon is completely isotropic. Thenew material combines the useful features of graphite(high thermal and electrical conductivities and abilityto withstand high temperatures and temperature flue-tuations) with very high strength. Its hardness (Mohs6-7) is much greater than that of graphite, and eventhough its density is low (l.4-1.5 g/cmê) it is irnper-meable to gases. The material is exceptionally resistantto corrosion, and many experiments have demoristrat-ed that glassy carbon is a very suitable material forcrucibles for chemical and metallurgical work. Thephotograph shows a number of crucibles, bowls anddiscs of different shapes and sizes made in the PhilipsAachen laboratories.

The piece at the lower right consists of carbon foamstrengthened with glassy carbon. This material differsfrom the commercially available carbon foam in itsvery much greater strength and greater resistance tooxidation (it will not burn in air below 600°C). Thisstrengthened carbon foam is obtai ned by carboniza-tion of a suitably impregnated plastic polymer foam,like the phenol-formaldehyde resins mentioned above.The density can be varied from 0.1 g/cm" to say 1.0g/cm"; the corresponding bulk modulus varying from10 to 25000 NJcm2 but the thermal conductivity onlyfrom 8 X 10-4 to 14 X 10-4 Jre s cm. This is a mostadvantageous feature for heat insulation, which is oneofthe principal applications of this material. Strength-ened carbon foam can also be used as a structuralmaterial. It can be machined either before or after car-bonization, although a diamond tool has to be usedwith the carbonized material.

[1] B. Lersmacher, H. Lydtin and W. F. Knippenberg. Glasar-tiger Kohlenstoff, Chemie-Ing.-Teclmik 42, 659-669, 1970.

370 l PHILlPS TECHNICAL REVIEW VOLUME 31

Recent scientific publicationsThese publications are contributed by staff of laboratories and plants which form' partof or co-operate with enterprises of the Philips group of companies, particularly by staffof the following research laboratories:

Philips Research Laboratories, Eindhoven, Netherlands EMullard Research Laboratories, Redhill (Surrey), England MLaboratoires d'Electronique et de Physique Appliquée, Limeil-Brévannes (Val-de-Marne), France L

Philips Forschungslaboratorium Aachen GmbH, Weil3hausstral3e, 51 Aachen,Germany A

Philips Forschungslaboratorium Hamburg GmbH, Vogt-Kölln-Straûe 30,2000 Hamburg 54, Germany H

MBLE Laboratoire de Recherches, 2 avenue Van Becelaere, 1170 Brussels(Boitsfort), Belgium. B

Reprints of most of these publications will be available in the near future. Requests forreprints should be addressed to the respective laboratories (see the code letter) or to PhilipsResearch Laboratories, Eindhoven, Netherlands.

R. P. Adriaanse & P. van der Laan (Philips InformationSystems and Automation Division, Eindhoven): Someremarks on a general class of Markov processes withdiscrete time parameter and dependent increments.Technometrics 12, 851-866, 1970 (No. 4).

C. S. Aitchison & R. Davies : Large-signal varactormeasurements.Electronics Letters 6,780-781, 1970 (No. 24). M

C. S. Aitchison & B. H. Newton: Varactor-tuned Xband Gunn oscillator using lumped thin-film circuits.Electronics Letters 7, 93-94, 197J (No. 4). M

G. A. Allen: The performance of negative electron af-finity photocathodes.J. Physics D 4,308-317, 1971 (No. 2). M

J. A. Appels & M. M. Paffen: Local oxidation of sili-con; new technological aspects.Philips Res. Repts. 26, 157-165, 1971 (No. 3). E

G. Arlt, W. Puschert & P. Quadflieg: Dielectric beha-viour of lithium iodate.Phys. Stat. sol. (a) 3, K 243-246, 1970 (No. 4). A

V. Belevitch: Relationships between design parametersof very selective filters.Electronics Letters 6, 585, 1970 (No. 18). B

F. Berz & C. G. Prior: Test of McWhorter's model oflow-frequency noise in Si m.o.s.t.s.Electronics Letters 6, 595-597, 1970 (No. 19). M

F. Berz & E. Pyrah: Numerical-integration proceduresin transistor-analysis computer programs.Electronics Letters 7,94-97, 1971 (No. 4). M

G. Blasse, A. Bril & J. Á.·de Poorter: Radiationlesstransitions in the Eu3+ center in LaAI03.J. chem. Phys. 53, 4450-4453, 1970 (No. 12). E

G. Blasse & A. D. M. de Pauw: Crystal structure ofsome LiMe5+Me6+06 compounds.J. inorg. nucl. Chem. 32, 3960-3961, 1970 (No. 12). E

J. Bloem (Philips Semiconductor Development labor-atory, Nijmegen): Silicon epitaxy from mixtures ofSiH4 and HCI.J. Electrochem. Soc. 117, 1397-1401, 1970 (No. 11).

P. Á. Boter, M. D. Wijnen & H. t, C. Nuyens (PhilipsElectroplating Laboratories, Eindhoven): Some newrefill cell systems.Power Sources 1968, editor D. H. Collins, PergamonPress, Oxford 1970, pp. 359-371. E

A. Boucher & L. Hollan: Thermodynamic and experi-mental aspects of gallium arsenide vapor growth.J. E1ectrochem. Soc. 117, 932-936, 1970 (No. 7). L

J. Bouma, A. J. J. Franken & J. D. B. Veldkamp: Atensile testing machine for thin filaments of highstrength and stiffness.J. Physics E 3, 1006-1008, 1970 (No. 12). E

J.-P. Boutot &G. Piétri: Ultrahigh-speed microchanne1photomultiplier.IEEE Trans. ED-17, 493-495, 1970 (No. 7). L

M. J. G. Braken: Het lassen van dunne materialen.Lastechniek 36, 243-247, 1970 (No. 11). E

P. C. Brandon: Thiocyanato-indo1es as energy-transferinhibitors in photophosphorylation.Arch. Biochem. Biophys. 138, 566-573, 1970(No. 2). E

P. Branquart & J. Lewi: Structure d'un compilateurALGOL68.Con grès AFCET, Paris 1970,pp. 5.4.138-152. B

P. B. Braun, J. Hornstra & J. J. Leenhouts: The crystalstructure of tricyclo[ 4,3,1, 13.8Jundecane-4,5-dione.Acta cryst. B 26, 1802-1806, 1970 (No. 11). E

1970, No. 11/12 RECENT SCIENTIFIC PUBLICATIONS 371

C. H. J. van den Brekel: Easy controllable injection ofvapours in carrier gases.J. Physics E 3, 878-880, 1970 (No. 11). E

J. C. Briee: Pulling crystals for optical devices.Opt. Laser Technol. 2, 206-2~8, 1970 (No. 4). M

E. Bruninx: The measurement of fast neutron flux den-sities above 0.5 MeV by a simple moderation method.Int. J. appl. Rad. Isot. 21, 657-666, 1970 (No. 11). E

K. H. J. Busehow: Rare-earthcobalt intermetallic com-pounds.Les éléments des terres rares, ColI. Int. C.N.R.S. No.180, Paris-Grenoble 1969, tome I, pp. 101-112; 1970. E

K. H. J. Buschow: The crystal structure of Th2C07.Acta cryst. B 26, 1389-1392, 1970 (No. 10). E

K. H. J. Buschow, A. M. van Diepen (NatuurkundigLaboratorium der Universiteit van Amsterdam) &H. W. de Wijn (Natuurk. Lab. Univ. Amst.): Magneticproperties and nuclear magnetic resonance of cubicRCU5 intermetallic compounds.J. appl. Phys. 41, 4609-4612, 1970 (No. 11). E

K. H. J. Buschow & A. S. van der Goot: The crystalstructure of rare-earth nickel compounds of the typeR2Ni7.J. less-common Met. 22, 419"428, 1970 (No. 4). E

K. H. J. Buschow & R. P. van Stapele: Magnetic prop-erties of some cubic rare-earth-iron compounds of thetype RFe2 and RxYl-xFe2.J. appl. Phys. 41, 4066-4069, 1970 (No. 10). E

K. H. J. Buschow & J. S. van Wieringen: Crystal struc-ture and magnetic properties of cerium-iron com-pounds.Phys. Stat. sol. 42, 231-239, 1970 (No. I). E

H. B. G. Casirnir: Microwave and optical generationand amplification.Proc. MOGA Conf., Amsterdam 1970, pp. 0.1-0.6. E

Ph. Chevalier, J.-P. Boutot & G. Piétri: A PM of newdesign for high speed physics.IEEE Trans. NS-17, No. 3, 75-78, June 1970. L

T. Chisholrn & A. M. Stark: A technique for the COlT,

putation of charged-particle trajectories in radio-fre-quency quadrupole devices.J. Physics D 3, 1717-1726, 1970 (No. 11). M

R. W. Cooper: Optical communication.Rev. HF 8, 67-72, 1970 (No. 3).

C. D. Corbey & R. Davies: Amplitude stabilisation ofa varactor frequency multiplier using self-bias resistancecompensation.Electronics Letters 7, 151-152, 1971 (No. 7). M

R. Cosier, A. Wise, A. Tressaud (Faculté des Sciences deBordeaux), J. Grannee (Fac. Sci. Bordeaux), R. Olaz-euaga (Fac. Sci. Bordeaux) & J .. Portier (Fac. Sci.Bordeaux): Sur de nouveaux composés fluorés ferri-magnétiques à structure wébérite.C.R. Acad. Sci. Paris 271C, 142-145, 1970 (No. 2). M

J. B. Coughlin & R. W. Lindop: Subnanosecond delaysin circuit complexes measured by slice probing.Solid State Technol. 14, No. 3, pp. 12 & 70, March1971. M

H. J. van Daal & K. H. J. Busehow: Kondo effect insome intermetallic compounds of Ce.Phys. Stat. sol. (a) 3, 853-871, 1970 (No. 4). E

P. A. van Dalen & C. A. A. J. Greebe: Generation ofBleustein-Gulyaev waves in piezoelectric plates.Physics Letters 33A, 93-94, 1970 (No. 2). E

P. Delsarte: BCH bounds for a class of cyclic codes.SIAM J. appl. Math. 19, 420-429, 1970 (No. 2). B

P. Delsarte, J. M. Goethals & F. J. MacWiIIiarns (BellTelephone Laboratories, Murray Hill, N.J.): Ongeneralized Reed-Muller codes and their relatives.Information and Control16, 403-442, 1970 (No. 5). B

M

F. Desvignes, V. Duchenois & R. Polaert: Equipementpour la mesure continue du diamètre de fibres.Techniques Philips 1970, No. 5, 2-10. L

F. Dintelrnann (11. Physikalisches Institut der Techni-schen Hochschule Darmstadt), E. Dorrnann (11. Phys.Inst. T.H. Darmstadt) & K. H. J. Busehow: NMR-investigation on ferromagnetic, yttrium-diluted GdAh.Solid State Comm. 8, 1911-19l3, 1970 (No. 22). E

J. A. W. van der Does de Bye, A. T. Vink, A. J. Bosman& R. C. Peters: Kinetics of green and red-orange pairluminescence in GaP.J. Luminescence 3, 185-197, 1970 (No. 3). E

F. Doittau, H. Bourcier, G. Verschoore, M. Hébert (allwith SODERN, Paris) & J. C. Pauwels: Camérasultra-rapides. Problèmes relatifs au dispositif d'ouver-ture du tube obturateur (générateur d'impulsions trèshaute tension).Techniques Philips 1970, No. 5, 11-22. L

H. Duifhuis (Institute for Perception Research, Eind-hoven): Audibility of high harmonics in a periodicpulse.J. Acoust. Soc. Amer. 48, 888-893,1970 (No. 4, Part 2).

A -. J. Fox & P. W. Whipps: Longitudinal quadraticelectro-optical effect in KTN.Electronics Letters 7, l39-140, 1971 (No. 5/6). M

K. G. Freeman: The physics of colour television.Physics Education 5, 326-331, 1970 (No. 6). M

K. G. Freeman & R. E. Ford (University of Surrey,Guildford): Variable gamma corrector improves tele-vision video signals.Electronic Engng. 42, No. 511,90-93, Sept. 1970. M

K. L. Fuller: AVOID - short-range high-definitionradar.Wireless World 77, 110-113, 1971 (No. 1425). M

S. Garbe & G. Frank: Photo-emission from silicon~doped p-type gallium arsenide.Gallium Arsenide, Proc. 3rd Symp., 1970, pp. 208-211;1971. , A

372 PHILlPS TECHNICAL REVIEW VOLUME 31

R. Genève: Some complementary observations as con-clusion (to the series of papers on medical thermographyin Acta Electronica).Acta Electronica 13, 179-183 (in French), 185-189 (inEnglish), 1970 (No. 2). L

\

. T; G.Gijsbers & W. J.Hoogenboezem (Philips Mechan-ical Engineering Works, Eindhoven).: Een numeriekbestuurde coördinatograaf biedt 'vele mogelijkheden.Metaalbewerking 36, 347-352, 1970 (No. 13). E

J. J. Goedbloed: On the up-converted noise ofIMPATTdiode oscillators.Proc. MOGA Conf., Amsterdam 1970,pp. 12.36-12.40.

EJ. M. Goethals & J. J. Seidel (Technical University ofEindhoven): Strongly regular graphs derived fromcombinatorial designs.Canad. J. Math. 22, 597-614, 1970 (No. 3). B

H. C. de Graaft":A modified charge-control theory forsaturated transistors.Philips Res. Repts. 26, 191-215, 1971 (No. 3). E

G. Groh: Holographische Methoden in der IC-Techno-logie. .Mikroelektronik 4 (Vortr. KongreB INEA, München1970), 162-179,1971. H

J. de Groot &M. T. Vlaardingerbroek: Some numericalresults on modes of oscillation in a transferred-electrondevice.Proc. MOGA Conf., Amsterdam 1970,pp. 20.34-20.39:

ES. H. Hagen: Leitungsmechanismus in spannungsab-hängigen SiC-Widerständen.Ber. Dtsch. Keram. Ges. 47, 630-634,1970 (No. 10). E

P. Hansen: Contribution of some 4d and 5d transition-metal ions on octahedral sites to the anisotropy offerrites and garnets.Phys. Rev. B 3, 862-870, 1971 (No. 3). H

P. A. H. Hart, J. A. PaIs, J. Prins & C. A. G. Strieker:Noise-measuring set-up for devices under. low-gainconditions.Philips .Res. Repts. 26, 216-228, 1971 (No. 3). E

H. Haug & K. Weiss: A new derivation of the equa-tions of motion for the complex order parameter ofhelium 11.Physics Letters 33A, 263-264, 1970 (No. 4). E

E. E. Havinga, H. Damsma & M. H. van Maaren:Oscillatory dependence of superconductive criticaltemperature on number of valency electrons in CU3Au-type alloys. .J. Phys. Chem. Solids 31,2653-2662, 1970(No. 12). E

D. Hennings &K. H. HärdtI: The distribution of vacan-cies in lanthana-doped lead titanate.Phys. Stat. sol. (a) 3, 465-474, 1970 (No. 2). A

B. Hill: Spatial noise in optical data-storage systemsusing amplitude Fourier-transform holograms.J. Opt. Soc. Amer. 61, 386-398, 1971 (No. 3). H

F. N. Hooge: l/f noise in the conductance of ions inaqueous solutions. .Physics Letters 33A, 169-170, 1970 (No. 3). E

B. B. van Iperen & H. Tjassens : Measurement of large-signal impedance, optimum ac voltage and efficiencyof Si pnn+, Ge npp+ and GaAs Schottky-barrier ava-lanche transit time diodes.Proc. MOGA Conf., Amsterdam 1970,pp. 7.27-7.32. E

R. E: Jesse & H. F. J. J. Giller: Cellular growth: therelation between growth velocity and cell size of somealloys of cadmium and zinc.J. Crystal Growth 7, 348-352, 1970 (No. 3). E

H. Kalter, J. J. H. Sehatorjé & E. Kooi: Electric doublelayers in MIS structures with multilayered dielectrics.Philips Res. Repts. 26, 181-190, 1971 (No. 3). E

M. A. Karsmakers: Het verbinden van glas aan metaal.Glastechn. Meded. 8, 116-125, 1970 (No. 4). E

D. Kasperkovitz & J. G. van Santen: Integration den-sity and power dissipation of MOS and bipolar shiftregisters - A comparison.Microelectronics and Reliability 9, 497-501, 1970(No.6). E

J. T. Klomp: Festkörperbindung zwischen Metall undKeramik.Ber. Dtsch. Keram. Ges. 47, 627-629, 1970(No. 10). E

A. Klopfer: Wasserstoffdesorption von Wolfram durchElektronenstoB.Vakuum-Technik 19, 167-170, 1970 (No. 7). A

J. E. KnowIes& P. Rankin: Disaccommodation ofper-meability in manganese-zinc-titanium ferrites.J. Physique 32, Cl/845--846, 1971 (Colloque No. 1,Vol. 1I). M

H. G. Koek & D. de Nobel: Technology of siliconSchottky barrier IMPATT diodes.Proc. MOGA Conf., Amsterdam 1970, pp. 7.1-7.3. E

H. Koeman (Philips Research Labs. Amsterdam): Acontrolled analogue pulse height store.Nucl. Instr. Meth. 86, 301-309, 1970 (No. 2).

E. Kooi, J. G. van Lierop, W. H. C. G. Verkuijlen &R. de Werdt: LOCOS devices.Philips Res. Repts. 26, 166-180, 1971 (No. 3). E

L. J. Koppens: Beziehung zwischen magnetischenEigenschaften und Mikrostruktur von Speicherkernen,die mit einer neuen Technik hergestellt wurden.Ber. Dtsch. Keram. Ges. 47, 654-657, 1970 (No. 10). E

E. Kraetzig: Investigation of superconducting proxim-ity effects with acoustic surface waves.Physics Letters 33A, 343-344, 1970 (No. 6). H

D. E. Lacklison, J. Chadwick & J. L. Page: Photo-magnetic effect in ferric borate.J. appl. Phys. 42, 1445-1446, 1971 (No. 4). M

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\ 1970, No. 11/12 RECENT SCIENTIFIC PUBLICATIONS 373

P. R. Locher & R. P. van Stapele: Supertransferredhyperfine fields on tetrahedral sites in some chromiumsulpho- and selenospinels. .J. Phys. Chem. Solids 31, 2643-2652, 1970 (No. 12). E

:/i

J. Loeckx: The parsing for general phrase-structuregrammars.Information and Control16, 443-464, 1970 (No. 5). B

M. H. van Maaren, H. B. HarIand & E. E. Havinga:Critical carrier concentration for superconductivity inmixed metal-semiconductor systems.Solid State Comm. 8, 1933-1935, 1970 (No. 22). E

./

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F. E. Maranzana: Kondo sidebands.Phys. Rev. Letters25, 239-242, 1970 (No. 4). E

R. J.Meijer: De Philips stirlingmotor (edited by H. vanGinkei).Chem. Weekblad 66, No. 44, 58-62, 30 okt. 1970. E

I

R. Memming & H. Tributsch (Physikalisch ChemisehesInstitut, Technische Hochschule, Munich): Electro-chemical investigations on the spectral sensitization ofgallium phosphide electrodes.J. phys. Chem. 75, 562-570, 1971 (No. 4). H

R. Metselaar: Een nieuwe wisselwerking: het foto-magnetisch effect.Chem. Weekblad 66, No. 41, 31-34, 9 okt. 1970. E

R. Metselaar, P. J. Rijnierse & U. Enz: LichtinduzierteÄnderungen der magnetischen Eigenschaften von poly-kristallinem Yttrium-Eisen-Granat.Ber. Dtsch. Keram. Ges. 47,663-665,1970 (No. 10). E

D. Meyer-Ebrecht: Entwurfsprinzipien für Präzisions-Relaxationsoszillatoren.Mikroelektronik 4 (Vortr. KongreB INEA, München1970),391-403, 1971. H

M. Monneraye: Le scellement métal céramique. Unrenouveau du scellement non métallique.Techniques Philips 1970, No. 5, 23-35. L

B. J.Mulder: Preparation of BaTiOa and other ceramicpowders by coprecipitation of citrates in an alcohol.Amer. Ceramic Soc. Bull: 49,990-993, 1970 (No. 11). E

G. T. M. Neelen: Vacuum brazing of complex heat eX-changers for the Stirling engine.Welding J. 49, 381-386, 1970 (No. 5). E

D. de Nobel & R. P. Tijburg: Improved method for thefabrication of GaAs microwave devices.Proc. MOGA Conf., Amsterdam 1970, pp. 9.1-9.3. E

R. C. Oldfield: Stratification in evaporated nickel-ironfilms.J. Physics D 3, 1495-1496, 1970 (No. 10).

Ph. Piret: Les codes de convolution utilisés pour lacorrection d'erreurs en paquets ..Rev. HF 8, 49-59, 1970 (No. 2). B

R. J. van de Plassche: A new high speed operationalamplifier.Mikroelektronik 4 (Vortr. KongreB INEA, München1970), 336-350, 1971. E

E. Roeder: Extrusion of glass.J. non-cryst. Solids 5, 377-388, 1971 (No. 5). A

F. L. J. Sangster: Integrated MOS and bipolar analogdelay lines using bucket-brigade capacitor storage.1970 IEEE Int. Solid-State Circuits Conf. Digest tech.Papers, pp. 74-75 & 185. E

P. Schagen: Electronic aids to night vision.Phil. Trans. Roy. Soc. London A 269, 233-263, 1971(No. 1196). M

C. Schiller: Interface analysis by X-ray diffraction topo-graphy. - '.Solid-State Electronics 13, 1163-1166, 1970 (No. 8). L

U. J. Schmidt & W. Thust: Korrektur der Ablenkfehlerdoppelbrechender Prismen in digitalen Laserstrahl-ablenkern und Bildvervielfachern.Optik 32, 570-584, 1971 (No. 6). H

J. F. Schouten (Institute for Perception Research,Eindhoven): Technologische en maatschappelijke evo-lutie.Natuurk. Voordr. Diligentia Nieuwe Reeks No. 48,51-60, 1970.

J. F. Schouten (Institute for Perception Research,Eindhoven): Tijd voor toonhoogte.Versl. gew. Verg. Afd. Natuurk. Kon. Ned. Akad.Wetensch. 79, 150-153, 1970 (No. 9).:

E. Schwartz: Obere Grenzen für die Empfindlichkeitder Resonanzfrequenzen von Reaktanzzweipolen.Nachrichtentechn. Z. 23, 553-558, 1970 (No. 11.). A

P. J. Severin: On the infrared thickness measurementof epitaxially grown silicon layers.Appl. Optics 9, 2381-2387, 1970 (No. 10). E

A. M. Stark & B. Singer (Philips Laboratories Briar-cliff Manor, N.Y., U.S.A.): Beam discharge lag.in thesilicon diode array camera tube.1971 IEEE Int. Solid-State Circuits Conf. Digest tech.Papers, pp. 136-137. M

A. Thayse: Boolean differential calculus.Philips Res. Repts. 26, 229-246, 1971 (No.3). B

J. P. Thiran, Ph. van Bastelaer & C. Wellekens: Des-cription of a filter synthesis and analysis progra~ witha special study of the numerical accuracy.Rev. MBLE 13, 39-58, 1970 (No. 2). B

MD. R. Tilley: Superradiance in arrays of superconduct-

W. J. Oosterkamp: Die Entwicklung der Röntgenröhre. . ing weak links.Röntgenpraxis 23, 252-260, 1970 (No. 11). E Physics Letters 33~, 205-206, 1970 (No. 4). E

374 PHlLIPS TECHNICAL REVIEW VOLUME 31

R. J;.::I;'ree, M. J. Josh & C. T. Foxon: On a failuremechanism in indium phosphide microwave oscilla-tors. . ,Solid-State Electronics 14, 519-520, 1971 (No. 6). M

J. Ubbink: Optimization ofthe rotor surface resistanceof the asynchronous electrostatic motor.Appl. sci. Res. 22, 442-448, 1970 (No. 6).. E

.J. Ungelenk: Herstellung dünner epitaktischer Gal-liumarsenidschichten durch Ionenzerstäubung.Vakuum-Teëhnik 19, 231-234, 1970 (No. 9). A

J. G. Verhagen, G. den Ouden, A. Liefkens & G. W.Tichélaar: Nitrogen absorption by ferritic weld metalduring arcwelding.'Metal Constr. Brit. Welding J. 2,135-143, 1970 (No. 4).

E

A. G. van Vijfeijken: Technological forecasting: eenbruikbaar instrument voor wetenschapsbeleid?Ned. T. Natuurk. 37, 5-11, 1971 (No. I). E

A. T. Vink & R. C. Peters:' Absorption and lumines-cence due to excitons bound to neutral, acceptors inGaP.J. Luminescence 3, 209-229, 1970 (No. 3). E

J

J. Vlietstra: FOURBAR, een interactief systeem voorhet samenstellen van vierstangenmechanismes.Informatie 12, 508-516, 1,970 (No. 12). E

K. Weiss: Untersuchungen an kubischem Kupferéljsul-fid (Digenit), Ill. Zum elastischen Entmischungseffektin Digenit.Berichte Bunsen-Ges. phys.· Chemie 74, 1257-1261,. v •

1970 (No. 12). E

F. F. Westendorp & A. G. Rijnbeek: A transducer tomeasure forces under high pressure.Rev. sci. Instr. 41, 1881-1882, 1970 (No. 12). E \,

H. J. de Wit & C. Crevecoéur: Deviation from Ohm'slaw in As2Se3 glass.Physics Letters 33A, 25-26, 1970 (No. I). E

J. P. Woerdman: Formation of a transient free carrierhologram in Si.Optics Comm. 2, 212-214, 1970 (No. 5). E

H. Zijlstra: Domain-wall processes in SmC05 powders.J. appl. Phys. 41, 4881-4885, 1'970 (No. 12). E

Contents of Electronic Applications 30, No. 3, 1970:

Channel electron multipliers: single channels and channel plates (pp. 89-97).M. J. Köppen: P-I-N diode aerial switches for the 160 MHz communication band (pp. 98-103).H. W. Evers & J. Peerlings: Rules for the design of short series-heater chains in hybrid television receivers(pp. 104-108).B. A. Bland: High-voltage silicon rectifier stacks (pp. 109-116).J. G. Versteeg: Line oscillator using a silicon controlled switch (pp. 117-119).J. M. Rosa Bunge: Addendum to the article "Instrument for measuring incremental inductance" in Vof. 29,No. 4 (p. 120).

.Contents ofValvo Berichte 16, No. 4, 1971:

V. Dubravec: Permanentmagnetische Wechselfeldfokussierung bei Klystrons (pp. 95-126).

~.a.,

Volume 31, 1970, No. 11/12 Published 27th October 1971pages 335-374