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THE TRANSISTRON TRIODE TYPE P.T.T. 601

BY

R. SUEUR

Chief Engineer P.T.T.

Head of the Department of Service des Recherches et du Contrôle Techniques P.T.T. Translation into English Copyright Mark P D Burgess March 2011

On Wednesday, May 18, 1949, the Minister of

P.T.T. presided over the presentation of the

Transistron triode P.T.T. 601 and some instruments

equipped with this device at the laboratories of

Service des Recherches et du Contrôle Techniques

(S.R.C.T.) of P.T.T.

It was similar to a presentation held in America

at Bell Telephone Laboratories in 1948.

Work on semiconductors conducted in France in

recent years in collaboration between the

Administration des PTT and the Société des Freins

et Signaux Westinghouse has produced similar

results to those of the Americans. Building on

previous work, Doctors Welker and Matare and a

team of researchers prepared germanium of high

resistivity and started manufacturing high back

voltage detectors, a prelude to the development of

the of germanium triode or Transistron triode.

During the same year the first germanium

Transistrons manufactured in France left the

Laboratories. In French we could call this device

“transistance” which is the literal translation of the

American term “transistor.” However transistance

in French would be like resistance, an electrical

quantity. Thus we have the name “Transistron”, or

resistance of transfer, the suffix “tron” indicating

active elements involving electrons or ions.

1o Semiconductors

At room temperature, solids can be divided into

three classes according to their electric

conductivity.

- Conductors

- Insulators

- Semiconductors

The phenomenon of conductivity is related to the

electronic organization of atoms of the material

being considered, the organization of its crystal

lattice and its physical crystalline imperfections and

chemical properties.

We know that the latest theories on the

constitution of matter shows the atom consists of a

central nucleus and electrons with fixed energy

levels. Of these electrons, we distinguish two

kinds: electrons bound to atoms and free electrons.

The energy of a bound electron is insufficient for

it to separate from its atom and its energy is

quantized.

The energy of a free electron is sufficient for it to

be separated from its atom and its energy is not

quantized.

According to the Pauli exclusion principle which

states that “In an atom there cannot be two

electrons defined by the same quantum

coordinates” (1) it is not possible to have several

electrons with the same energy in an atom. We say

that each electron has a defined “energy level” and

that energy level can vary by a quantum jump

under the influence of X-rays, for example.

We know that this quantum energy is equal to dw

dw = h v

where h is Planck's universal constant equal

Fig. 1

Unit cell of Ge. All other

atoms in the network are

inferred from these by

translations ha1 + ka2 + la3

Projection on a horizontal

plane, the atoms num-

bered in the unit cell.

to 6.55 10-27

erg sec. and v is the frequency of the

electromagnetic wave radiated in the quantum

jump of the electron.

Germanium is the 32nd element in the

Mendeleev table normally with 32 electrons around

its nucleus.

The atoms form a solid body in a simple

arrangement known as a three dimensional crystal

lattice. Fig. 1 gives the example of the theoretical

crystal lattice for germanium.

In the crystal lattice of a particular solid there

may be free lattice electrons liberated from atoms

that are chemical impurities or from atoms of the

material itself occupying energy levels. In a

structure without impurities or physical defects

energy levels are grouped into bands and each band

(1) There are four quantum coordinates: n, l, m, s

n: characterizes the position of the electron, between 1 and 7 l: is related to the momentum

m: is the magnetic quantum number

s: is the quantum number that characterizes the spin

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can generally be understood to have a maximum of

twice as many levels as there are atoms in the

crystal lattice according to the Pauli exclusion

principle.

Several bands may exist and they are separated

by regions called "forbidden bands" where there

cannot be any electrons. A full band has all levels

occupied by electrons and an empty band has no

electrons. The higher energy bands are occupied by

electrons of high kinetic energy (Fig. 2).

At room temperature a solid conductor has its

higher energy bands partially filled with electrons,

thus an electric field applied to the conductor easily

causes a change of electron energy levels in this

band and this explains the high conductivity of con-

ductors. At absolute zero they still have electrons in

the upper band.

On the other hand insulators have no electrons in

their upper bands, their lower bands are filled and

the forbidden bands may be several electron volts.

A very intense electric field can only move the

low-energy electrons from the lower bands with

great difficulty. The electrons would have to move

from one energy band to another and this is very

unlikely. Thus the conductivity of insulators is very

low. At absolute zero, there are no electrons in the

upper band.

Semiconductors are intermediary materials, their

higher energy band is empty and lower band is

filled. Between these the bands are partially filled,

and unlike insulators the energy difference between

the empty band above and the full band below is

quite low. At room temperature, they have very low

conductivity. At absolute zero they are insulators

and their temperature coefficient is negative.

There are two types of semiconductors. The first

is known as "intrinsic" such as pure germanium and

the second is known as "extrinsic" and is the result

of physical defects or chemical impurities in the

crystal structure of intrinsic semiconductors.

According to their type these impurities may

receive or donate electrons in the semiconductor

and they create additional energy levels that

increase the conductivity.

The very low conductivity of intrinsic

semiconductors at room temperature (10 ~ 2 mho /

cm for germanium) make them unsuitable for

practical applications.

We say an extrinsic semiconductor is N or P type

depending on whether the impurities add or donate

electrons in the crystal lattice and it appears to be a

function of the chemical valency of the intrinsic

semiconductor relative to the impurities.

Thus phosphorus and antimony produce an N-

type germanium extrinsic semiconductor and boron

and aluminum make a P-type silicon extrinsic

semiconductor. Copper oxide Cu2O is a P-type

extrinsic semiconductor.

When impurity atoms are inserted in an intrinsic

semiconductor two cases may occur:

-The valency of the impurities is less than that of

the intrinsic semiconductor. In this case, if an

impurity atom takes the place of an atom in the

crystal lattice, one or more electrons in the

semiconductor can simply fill the vacant bond

leaving a hole in the band they leave.

This hole can be treated as a charge of equal and

opposite sign to the electron. It causes the

appearance of an energy level related to the

corresponding band.

-The valency of the impurities is greater than that

of the intrinsic semiconductor. In this case the

impurity atoms promote electrons in the permitted

bands and they are found to have energy levels in

the band gap.

These respective energy levels are located close

to the boundary (0.1 eV.) of the normal bands and

increase the conductivity of the body.

In the first case conduction is caused by pseudo

electrons, as though positive electrons were

involved and in the second case the conduction is

electronic.

The type and quality of a semiconductor is

conveniently determined by the Hall effect.

A strip of material M simultaneously subjected

to the influence of a magnetic field H normal to its

thickness e and a longitudinal electrical current I

causes a transverse emf E (Fig. 3).

For a body at temperature θ the quantities H, e, I,

E are connected by the expression:

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where R is called the “Hall coefficient” named after

the physicist Hall who demonstrated this effect in

1879.

With the direction given to the current I and the

field H, the emf E can appear positively or

negatively oriented.

This sign has a direct impact on the coefficient of

R and depends on the material subjected to the

experiment. Electronic conductive bodies have a

negative Hall coefficient, (N type); those

conductive by holes have a positive coefficient (P-

type).

In general, germanium at room temperature has

electronic conductivity.

The value of R can be between 10-7

and about

10-4

for germanium.

The origin of the Hall Effect can be explained by

the deviation of the trajectories of free electrons

liberated by the electric current by the magnetic

field.

The sign of the Hall coefficient enables the

determination of the type of conductivity of the

material and its magnitude:

- The number of conducting electrons per unit

volume.

- The mean free path of electrons.

- Their mobility.

The conductivity, σ, of a semiconductor with

conductivity due to electrons or holes is given by

the expression:

where: e = charge of an electron

l = mean free path of electrons or holes

N = number of liberated electrons or holes

per unit volume

m = electron mass

k = Boltzmann constant

T = absolute temperature.

The mobility, b, of a stream of electrons or holes

is defined as the speed of the electron or

hole in a unit electric field.

where:

The height of the barrier layers of a rectifier is

more pronounced when the mobility is lower.

The theory of solid bodies permits us to write:

Thus measurement the Hall coefficient, R, allows

the calculation of N

In addition the measurement of σ and R allows

the calculation of b:

and consequently that of l.

Knowledge of these different quantities is

essential to define the best properties of

semiconductors, the existing methods of chemical

and spectrographic analysis being insufficient to

make an adequate determination of impurities.

In addition, defects in the crystal structure have a

huge influence on the behavior of semiconductors

and these defects have an impact on their physical

properties, particularly on mobility.

For different kinds of French N type germanium

at room temperature, typical data is given in the

following table:

Figure 4 shows equipment for measuring the Hall

coefficient.

Germanium was discovered in 1886 by the German

chemist Winkler.

It is available from several sources:

a) Naturally, from germanite, pyrite

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comprising 30 to 40% copper and 1 to 4%

germanium, the richest deposits are located in

South-West Africa near Tsumeb. They are in the

form of pockets that seem to accompany deposits

of zircon. It is also found in some argyrodites.

Pyrite containing up to 1% in deposits have been

found near Freiberg (Saxony).

It is also contained in some sulfur coals, such as

those of Durham.

b) As a metallurgical by product from the

processing of zinc and cadmium.

The crude germanium does not generally have a

suitable chemical composition nor a homogeneous

structure.

It still must undergo physical and chemical

treatment to give suitable P or N type

characteristics and resistivity appropriate to the

required end use.

Figure 5 shows a germanium processing facility.

2° Contact between a conductor and a

semiconductor.

It is known that two different materials in contact

with one another create a potential difference in the

vicinity of the point of contact called the "contact

potential difference" related to the difference in the

work function of electrons in each material.

The work function is the work done to remove an

electron from the body and make it free. The work

function xn in a extrinsic semiconductor depends on

the level of impurities found there. The difference

in work function between a metal and a

semiconductor is about 0.2 to 0.5 eV.

Formulas for the difference in work function

were given by Fowler for different cases. For an

extrinsic semiconductor that is:

TYPE N

Weak ionisation (n1 ≤ N1)

Strong ionisation (n2 ≈ N1)

TYPE P Weak ionisation (n2 ≤ N2)

Strong ionisation (n2 ≈ N2)

where:

v = is a function of (h, k, T, n);

e = Electron charge;

ʋ = Contact potential difference;

xs =Work function of the semiconductor;

xm = Work function of metal;

k = Boltzmann constant;

T = Absolute temperature;

N1 = Number of donator energy levels per unit

volume, located a level below the band gap.

n1= number of electrons excited to the empty band

per unit volume.

N2 = number of acceptor energy levels per unit

volume and located at a certain energy level above

the full band.

n2 = number of free holes [in the full band] per unit

volume.

The difference in contact potential causes the

emergence of barrier potentials located in the

vicinity of the surfaces in contact. Between these

barriers there is an area known as insulating barrier

layer with high dielectric constant.

Explanations on the formation and existence of

barrier potentials have been given by many authors

(Schottky, Mott etc). They refer to the difference of

work function that is to say the difference in energy

levels that may exist between the two bodies

involved. Following the conventional

representation, Figure 6 indicates the position of

the bands and energy levels that exist in the vicinity

of the surface of a metal and an N-type

semiconductor before and after contact.

In the semiconductor energy levels of electrons

created by the impurities are located around the

normally empty upper band and they are higher

than the upper band, of the conductor.

When contact is made it is found that the

electrical current flows more easily in the direction

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of "conductor to semiconductor” than in the

opposite direction.

At the moment of contact we can say that

because of the difference in the energy of the

electrons from each material involved, the electrons

of the semiconductor migrate to the conductor

allowing a positive surface layer to form on the

surface of the semiconductor while a negative layer

forms in the conductor; a double potential barrier is

thus formed, and between them appears the barrier

layer.

An electric potential difference moves the high-

energy electrons more easily from the

semiconductor to the conductor and direct current

flow in the easy direction is observed.

This overview of the probable mechanism of

formation of potential barriers and barrier layers

does not give an accurate view and the theory is

incomplete. But note that the difference in

conductivity caused by the direction of flow of an

electric current in a contact between a conductor

and a semiconductor is exploited in detectors and is

one of physical phenomena seen in the Transistron.

The most recent solid state theories and

experimental results indicate that the barrier layer

has a thickness of about 10-4

mm.

In a P-type extrinsic semiconductor equilibrium

is established differently. (Fig. 7).

Upon contact, the holes arising from the partially

filled band flow from the semiconductor to the

conductor, creating a positive barrier and allowing

a negative barrier to form in the semiconductor.

The overall conductivity is not electronic and it can

be seen that the easy flow of electric current is from

semiconductor to conductor. [See translator’s

notes]

3° Operation of the Transistron (Fig. 8)

N-type high resistivity germanium was polished

and then etched with acid to expose a suitable

crystalline surface structure which was then

chemically treated to make (or enhance) a P type

semiconductor layer. Wire point contacts of bronze,

tungsten or molybdenum were then positioned on

this surface.

It is found that the forward direction of current

flow is observed for N-type semiconductors.

Then apply an electric current (I) of 1-2

milliamps in the forward direction that is in the

direction "from the contacts towards the

semiconductor." It appears that the electrical

conductivity around the point contact depends on

the value of I (current). This is the second

phenomenon called transistance used in the

Transistron.

If we then place a second contact on this surface

at a distance d from 20 to 50 microns from the first,

we see that the resistance R measured between the

two points depends on I according to a law given

qualitatively in Figure 9.

We also know that an amplifier is essentially an

energy valve where the energy ratio Ws/Wc between

energy output Ws released by a valve and the input

and control energy, Wc, is larger than unity.

Now arrange the assembly of Figure 10 where

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the direct current IE is of the order of a milliampere,

the variable resistor r a few hundred ohms, a

battery p of voltage e of 1-2 volts. Point “a” is the

control point and the resistance of the layer is

around a few tens of thousands of ohms.

A very high voltage E (50 to 100 volts) is applied

through a resistance R (20,000 to 30,000 ohms) to

the point “c” in the reverse direction so the

resistance of the semiconductor is very large. We

note that the current Is depends on IE and the

current Is must certainly flow in the layer between

the points "a" and "c". The valve is then

represented by the resistance of the layer, it is

controlled by the current IE and it is found that the

control power required is much less than that which

appears in the output resistance, Rs.

The magnitude of the input to output power ratio

given by

can now reach 100 to 200 and output power Ws is

of the order of several tens of milliwatts.

Explanations or physical phenomenon of

variation of surface conductivity attributed to the P

layer and the bulk N semiconductor as a function of

the polarization of the control electrode are

provided by Bardeen and Brattain (see

bibliography) and we refer the reader to articles of

these authors. The calculations and tests conducted

in France so far seem to confirm the role of a layer

where the conductivity occurs by pseudo electrons

[holes]. Their verification require the

implementation of very difficult procedures,

particularly the precise measurements of inter-

electrode capacity.

An electrical equivalent circuit most convenient

in our opinion for the Transistron follows (Fig. 11).

It results from the mathematical analysis of the

operation of the Transistron.

One can propose the following equations where

the parameters correspond to the four elements of

the equivalent circuit.

Where we define:

RE = input resistance,

Rr = feedback resistance between the output and

input

Rc= coupling resistance which loads the voltage

gain of the circuit

Rs = output resistance.

These two equations allow us to establish the

following equivalent circuit (Fig. 12).

Where:

where by applying the Thevenin Theorem we

readily obtain from the schematic in Figure 11:

R1 = RE - Rr

R2 = Rr

R3= Rs - Rr

Es = (Rc- Rr) dIE

The family of curves in Figure 13 found for a

type 601 Transistron shows, as might be expected,

(see fig. 9) that Is increases with IE.

Furthermore the voltage

Er = Rr dIs

is the load voltage.

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We can now establish a convenient method for

calculating the various characteristics of an

amplifier in terms of the previously defined

variables.

Place the Transistron between an EMF generator

where e = E(sinωt) for example and input

impedance RG and output impedance equal to RR.

Figure14 shows the equivalent circuit in this case

excluding the bias circuits.

For convenience of calculation we put:

And then we find:

a) Input impedance ZE

ZE = RE (1- μβ)

b) Ouput impedance Zs

Zs = Rs + Rr (1- μoβ) ≈ Rs

c) The voltage gain in Nepers

If RR is very large

d) The overall gain in Nepers

For RG ≠ ZE the first term is negative and the

second for RE ≠ Rs, they are equal to zero for:

RG = ZE

RE = Rs

For good power gain the source and output

impedance should be matched to ZE and Rs.

respectively and the gain will be:

Around an operating point identified in Figure 13

and defined by

UE ≈ + 0.35 volt

Us ≈ -45 volts

We find for the Transistron 601 the following key

characteristics:

RE ≈ 170 ohms

Rr ≈ 70 ohms

Rc ≈ 30,000 ohms

Rs ≈ 20,000 ohms

Which gives the equivalent circuit in figure 15.

We find for RR = Rs and RG = ZE

μo = 30,000/170 = 176

μ = 176/2 = 88

β = 3.5 10-3

μβ = 0.308

ZE = 170 (1 – 0.308) ≈ 188 ohms

Zs = 20,000 ohms

Gt ≈ 5.5 Nepers

GoM ≈ 5.15 – 2.38 – 0.1 ≈ 2.7 Nepers ≈ 24.5 dB

We note in passing that Transistron is a very

good voltage amplifier.

Circuits for measuring Transistron gain are

easily deduced from the definitions.

The overall stage gain of the Transistron is

related to the input and output transformers.

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4° Making Transistrons.

The key to the production Transistrons lies in the

preparation of germanium, in the selection of bars

where pellets should be cut, in the search for points

of contact and optimal adjustment of the spacing of

the point contacts. These last two operations are

carried out moreover under the microscope and are

made easier in the type 601 by the mechanical

arrangements that are used (Fig. 16).

Legend Fig 16 Ceramic body ... ... ..Soldered bronze caps with

the ceramic

The two bronze rods a and c are connected to a

point contact P of tungsten wire. The rod b supports

the Ge pellet. Each rod slides in a bronze cap and

its position can be fixed by a screw. The set of

three rods can be adjusted while checking the

electrical characteristics on the surface of the pellet:

a and c can slide laterally and b can be adjusted by

translation and rotation. The translation of b allows

such precise control of the spacing of the point

contacts.

A pilot production run has already been

completed enabling the study of methods of

manufacturing and control. From November the

Westinghouse Company will manufacture

sufficient quantities for the state agencies that

sponsored the research at the company.

Figure 17 shows a photograph of Transistron

type 601.

5° Transistron Applications.

Of test equipment currently operating in the

laboratories of S.R.C.T. there is:

-A broadcast receiver (Fig. 18);

-A transmitter for 300 metres longwave.

-A 4 Transistron television video amplifier

bandwidth. 40-10000 p/s, gain of 5.2 Neper and

20 milliwatts of output power.

-A medium range telephone line repeater (Fig.

19);

-A long distance telephone repeater for a 4 wire

loaded circuit.

This latter unit will be inaugurated in Paris on a

Paris-Nancy circuit and its schematic is given in

figure 20.

Its maximum gain is equal to 3.5 Neper and

available output power is 15 milliwatts. Total

energy consumption is about 0.9 watt per direction

of amplification. A pentode repeater of guaranteed

10,000 hours life consumes 4 watts per direction.

Due to the simplicity of the possible source of

polarization of its electrodes and low consumption,

Transistrons are conveniently powered remotely

via the telephone line they are installed on. To the

extent that the life-time projections of this

equipment are borne out they will reduce the cost

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of telephone lines by using more amplifiers on

thinner lines reducing raw materials usage.

Figure 21 shows the diagram of the amplifier

remotely powered with two push-pull Transistrons

shown in Figure 19.

The S.R.C.T. Laboratories current applications

research is particularly directed to applying the

Transistron for telephone circuit electronics

targeting the simplification of equipment, reducing

the hardware footprint, increasing the security of

service and reducing the annual costs of the

circuits.

The team conducting applications research on

semiconductors include:

For the Administration of P.T.T.:

MM. JOB, Ingénieur des P. T. T.

MOLL, Ingénieur Contractuel

CHALHOUB, Ingénieur Contractuel

PERINET, Inspecteur des I. E. M.

GANET, Inspecteur des I. E. M.

LE FLOCH, Contrôleur des I E. M.

VALIÉNET, Contrôleur des I. E. M.

COULON, Contrôleur des I. E. M.

POTET, Contrôleur des I. E. M.

For the Westinghouse Company:

MM. WELKER, Docteur Physicien

MATARE, Docteur Physicien.

PETIT-LEDU, Physicien

BETHGE, Ingénieur.

POILLEAUX, Technologiste.

CALON, Technologiste.

PHILIPPOTEAUX, Technologiste.

The authors particularly thank M ENGEL,

Technical Director of the Westinghouse Company,

for the valuable assistance he gave in all

circumstances during the work on the Transistron.

Refer Translator’s Notes overleaf

REFERENCES Atomistique et Chimie Générale, by R RENAULT. Dunod,

Paris.

Modern Theory of Solids by SEITZ - McGraw Hill, N. Y.

and London.

Electronic Processes in Ionic Crystals by N. F. MOTT and

RW. GURNEY - Oxford University, London.

Crystal Rectifiers, by TORREY and WHITMER - M.I.T.,

McGraw Hill N.Y. and London.

Microwave Mixers by POUND - M.I.T. Mc. Graw Hill N.Y.

and London.

Die Elektronenleitung des Kupferoxyduls by W.

SCHOTTKY and F. WAIBEL, Physikalische Zeitschrift N °

23, 1933, (Translation CNET N° 38).

Uber die Elektriche leit fahrigkeit des kupfer oxyduls im

gleichgewicht mit weinen nachbarphalen by F. WAIBEL.

Zeitchrift für technische Physik N° 11, 1935 (Translation

CNET No 428).

Détecteurs à Pyrite pour ondes décimétriques by H.

WELKER - (Translation N° 5441 du Ministère de

l'armement S.E.F.T.).

Schottky's Theories of dry solid Rectifiers by JOFFE

Electrical Communications Vol. 22, N° 3, 1945.

Electrical resistance of the contact between a semiconductor

and a metal, by JOFFE,- J. Phys. U. R. S. S., Vol. 10, N° 1,

1946 (Translation CNET, N° 622).

Sur l’intérêt et les possibilités d'application des semi-

conducteurs électroniques dans la technique des hautes

fréquences by M. TEZNER - Note Technique CNET, N°

1047.

Note relative aux redresseurs à contact ponctuel sur semi-

conducteur - Note S.R.C.T. - Département Transmission 10-

10-48.

Le courant électrique, le photon et l'électron par M. G.

POCHOLLE, Ingénieur en Chef des P,T.T. - Bulletin de

Documentation du Secrétariat aux Forces armées

«Guerre ».

The Transistor a crystal triode, by D. G. F. and F. H. R.,

Electronics, September 1948.

The Transistor A semi-Conductor Triode, by J BARDEEN

and W. H. BRATTAIN, the Physical Review, July 15, 1948.

Nature of the Forward Current in Germanium point

Contacts, by W. H. BRATTAIN and J. BARDEEN, The

Physical Review, July 15, 1948.

Modulation of Conductance of Thin Films of Semi-

Conductors by Surface Charges, by W. SHOCKLEY and

G.L. PEARSON, The Physical Review, July 15, 1948.

Les détecteurs à Germanium by R. SUEUR, Information

Technique - janvier-février 1949.

Germanium, important new Semiconductor, by Dr. W.

Crawford DUNLAP VR, General Electric Review,

February 1949.

Temperature Dependence of the Work Fuction. of Semicon-

ductors by A. H. SMITH, Physical Review, 15 March 1949.

The Effect of Surface States on the Temperature Variation,

of the Work Function of Semiconductors by Jordan, J.

MARKHAM and PH MILLER Jr.

The Type-A Transistor by RM. RYDER, Bell Laboratories

Record. March 1949.

Some Novel Circuits for the Three 'Terminals

Semiconductor amplifier by W. M. WEBSTER, E.

EBERHARD and L.E. BARTON, R.C.A. Review, March

1949.

Physical Principles Involved in Transistor Action by J.

BARDEEN and W. H. BRATTAIN, Physical Review 15

April 1949.

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Translators’ Notes

The available copies of the original publication

are only available in relatively low resolution and

in particular the originals of Figures 18 and 19 are

poorly reproduced. In this facsimile Figure 18 has

been copied from an identical picture in Aberdam

1949 (courtesy Christian Adam) and Figure 19 has

been copied from Aisberg 1949.

Early Versions of the Transistron 601

There are three versions of the Transistron 601:

1. Three adjustable stems

2. One adjustable stem and a window cap

3. One adjustable stem and no window cap

(1) In his text Sueur describes what we presume

to be an early version in which the stems that hold

the emitter and collector point-contacts can slide

and rotate in their end-caps for the purposes of

adjustment and then fixed in place with a grub

screw. The crystal holder is equipped with the same

facility.

The pictures of the Transistron clearly show this

arrangement for the crystal holder but not for the

emitter and collector indicating that early in 1949

the method of production was simplified.

Contemporary pictures also show two versions of

this Transistron.

(2) In figure 17 a Transistron is shown with a cap

placed over the window used to adjust the point

contacts on the crystal. This version of the

Transistron is used in the broadcast receiver and the

telephone circuit repeater (figs 18 and 19) and other

equipment such as the long wave transmitter shown

in Aberdam 1949:

(3) But these contemporary sources show

Transistrons without a cap:

Pictures above from Aberdam 1949 courtesy

Christian Adam.

Above: Publicity picture of the Transistron on its

official release. [Aisberg 1949]

Forward and Reverse Bias

The treatment by Sueur is somewhat confusing in

relation to point contacts on N or P germanium.

The following provides a consistent explanation

from Pfann 1950.

Conductivity

Type of the

Semiconductor

Polarity of Point

Forward

Direction

Reverse

Direction

N-Type + -

P-Type - +

Thus the bias arrangements for each case is given

as follows where the emitter is forward biased and

the collector is reverse biased:

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References

Aberdam H 1949 Transistor et

Transistron Ingénieurs et Techniciens 12 213-18

Aisberg E 1949 Transistron = Transistor+ ? Toute

la Radio 137 218-20

Pfann W Scaff J 1950 The P-Germanium

Transistor Proc IRE 38 1151-54