US2680159A

US2680159A - Amplifier employing semiconductors

Info

Publication number: US2680159A
Application number: US215227A
Authority: US
Inventors: Grover Eric Houghton
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1950-03-21
Filing date: 1951-03-13
Publication date: 1954-06-01
Anticipated expiration: 1971-06-01
Also published as: FR1034265A; DE968666C; GB695019A; NL90299C; GB682206A

Description

June 1-, 1954 E. H. GROVER 2,680,159

AMPLIFIER EMPLOYING SEMICONDUCTORS Filed March v13, 1951 In venlor flP/C H. move-R generally supposed to Patented June I, 1954 Eric Houghton'Grover, London,

England, assignor to International Standard'Electric Corporation,

New York,

N. Y., a corporation of Delaware Application March 13, 1951, Serial.No. 215,227

Claims priority, application Great'Britain- March 21, 1950 6 Claims; (CL 17 9171 The present invention relates toelectric amplifying devices employing semi-conducting materials, which have been called: for convenience crystal triodes.

It is alreadyv known that certain crystalline semi-conducting materials are suitable for use as point-contact rectifiers (generally known as crystal detectors) and that such material maybe made'to act as an amplifier byv mounting a body of the material on, or in, a suitable metal base or holder which makes electrical contact'with the body over-an extended area, and by providing it With two fine Wire electrodes or catwhisker arranged very close together incontact with the surface of the body. Bysuitably polarising the electrodes with respect-to the base the device can be made to operate as an amplifier similarly'to a thermionic valve, and for this reason the device has been called a crystal triode by analogy. However, the word triode is not intended to be restricted to a device having just three electrodes, for as in the case of thermionicvalves,"there may 'be additional electrodes employed for control purposes.

In' such crystal triodes known hitherto, two

cat whisker electrodes are provided, andione of them, called the emitter electrode, is polarised with respect to the' ducting material at present'k'nown for this purpose is germanium, and a suitable materialior the cat whisker is Phosphor "bronze.

The amplifying action in a crystal triodeis result from interaction between the collector-and emitter currents, and thecontrol of the collector current bythe emitter current can therefore beimodified if the amount of inter-action can be modified;

The amount of interaction'between the collector-and emitter currents may be increased by reducing the-cross-section of the semi-conductor at the point where the electrodes make contact, and by constraining the collector and emitter currents so that'they both "flow mainly through the reduced portion of the semi-conductor. This is accomplished according to the present invention by-providing an electric amplifying device comprising a body of semi-conducting"material consisting of two main portions connected by an intermediate portion of smaller cross-sectional area than either of the main portions, a collector electrode-and an emitter electrode, each making rectifier contact with thesurface of the intermediate-portion of the material, two base electrodes in contact respectively with the two main portions; and means for separately biassing the collector and emitter electrodes each with respect to a corresponding one-of the base'electrodes in such manner that both the emitter and the collector currents are constrained to-flow in the same part of the said intermediate portion.'

One way of carrying out-the invention is to mount thesemi-conductor on a base electrode or holder in the usual way and then to make-21 saw-cut through the holder and semi-conductor so that the latter is nearly, but not quite, divided into two separate portions. The twocat whiskers manner described in the specification of British Patent No; 682,206 dated February 25, 1953 of K.-A.' Matthews'for Crystal. Triode-divided Base Electrode with, however, the further requirement that a cross-blessing should be used, that cut," are constrainedto'flow largely in the same direction' in the 'reducedcross section of the semiconductor.

The conditions of the invention may be fulfilled in various other ways. For example, if thesawout be" made suf'nciently Wide; the two cat whiskers could be placed in contact with the semi-conductorat the bottom of the slot instead in a metal holder, and cutting a slot through the holder and semi-conductor to form the crevasse 4. The emitter and collector electrodes 6 and i consist of cat whisker, shown as arrow heads. making point-contact with the surface of the semi-conducting body i at the narrow portion 5 just above the top of the crevasse i. The cat whisker should preferably be made from Phosphor bronze wire.

The emitter electrode 6 is biassed positively with respect to the base electrode 3 on the opposite side of the crevasse t by a source 3, having a potential not more than about 1 volt. The source 8 is connected to the emitter electrode 6 through the secondary winding of an input transformer 9, the primary winding of which is connected to a pair of input terminals iii, which the signals to be amplified are supplied.

The collector electrode 1 is biassed negatively with respect to the other base electrode 2 by a source 12 having a potential which may be anything from 5 to so volts. The source 52 is connected to the collector electrode 3 through the primary winding of an output transformer [3, the secondary winding of which is connected to a pair of output terminals is, it which may be connected to a load circuit (not shown) to which the amplified signals are to be delivered.

The two

base electrodes

2 and 3. are connected by a large blocking capacitor it to bring them substantially to the same potential at signal irequencies.

For the above description it has been assumed that the semi-conducting material is of the N- type, such as germanium, for example. If P- type material is used, each of the bias sources 8, i2 should be reversed. A brief explanation of the difference between l and P- type semiconducting material will be found in U. S. Patent No. 2,653,374 dated thews-C. de B. White for Electric Semiconductor, and assigned to the same assignee as the present application.

It will be seen that with the arrangement shown the emitter and collector currents are both constrained to flow in the portion 5 of reduced cross-sectional area, and as each electrode is biassed with respect to the base electrode on the opposite side of the crevasse 4, the two currents are forced to mix, and the degree of interaction is thereby increased.

Fig. 2 illustrates the second type of arrangement alluded to in the earlier part of this specification. Corresponding elements are given the same designations as in Fig. l.

The crevasse or slot G is made wide enough to enable the electrodes 5 and 1 to make contact with the semiconductor inside the crevasse 4 instead of outside; otherwise the arrangement is essentially the same as shown in Fig. 1.

While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a .7

limitation on the scope of the invention.

What is claimed is:

1. An electric amplifying device comprising a body of semi-conducting material having two main portions and an intermediate portion interconnecting said two main portions, said intermediate portion being of a lesser thickness than either of said main portions to define a channel therebetween a collector electrode' and an emitter electrode, rectifier contact means for September 29, 1953, of K. A. Mateach of said electrodes each contacting the surface of said intermediate portion of the material, two base electrodes in contact respectively with the two main portions, and means separately biassing the collector and emitter electrodes each with respect to a corresponding one of the base electrodes in such manner that both the emitter and the collector currents to the base electrodes are constrained to flow in the same part of the said intermediate portion, said contact means for the electrodes being spaced apart and so located that each engages the intermediate portion between the other contact means and that main portion to the base electrode of which said other contact means is connected through its bias means.

2. An electric amplifying device comprising a body of semi-conducting material having a slot therein dividing it nearly but not quite into two separate portions, two base electrodes in contact respectively with the said two portions, a collector electrode and an emitter electrode, rectifier contact means for each of said electrodes, each of said contact means making rectifier contact with the surface of semi-conducting material on the narrow portion formed by said slot, and means for separately biassing the collector and emitter electrodes each with respect to one of the base electrodes, in such manner that the collector and emitter currents to the base electrodes are constrained to flow in the same part of the said narrow portion, said contact means for the electrodes being spaced apart and so located that each engages the intermediate portion between the other contact means and that main portion to the base electrode or" which said other Contact means is connected through its bias means.

3. An amplifying device according to claim 2 in which the collector and emitter electrodes and contact means comprise cat whisker making point-contact with the surface of the said narrow portion on the face remote from the end of the slot.

4. An amplifying device according to claim 2 in which the collector and emitter electrodes and contact means comprise cat whisker arranged in the slot and making point-contact with th said narrow portion at the blind end of the slot.

5. An electric amplifying device comprising a body of semi-conducting material provided with a transverse slot to divide said material into a pair of main portions interconnected by arelatively thin bridge-like portion, a base electrode maintained in contact with each of said two main portions, a pair of cat whisker type electrodes maintained in engagement with the surface of said bridge-like portion in closely spaced relation one to the other, and means for separately biassing said collector and said emitter electrode each with respect to one of the base electrodes, whereby collector and emitter currents to the base electrodes are constrained to flow in substantially the same direction through the same part of said bridge-like portion, said cat whisker electrodes being spaced apart and so located that each engages the intermediate portion between the other cat whisker electrode and that main portion to the base electrode of which said other cat whisker electrode is connected through its bias means.

6. An electrical amplifyin device comprising a body of semi-conducting material provided with a transverse slot to divide said material into a pair of main portions interconnected by a relatively thin bridge-like portion, a base electrode maintained in contact with each of said two main portions, a pair of cat Whisker type electrodes maintained in engagement with the surface of said bridge-like portion in closely spaced relation one to the other, the engagement point of each cat whisker with the surface of the bridgelike portion being closerto one of the base electrodes than the engagement point of the other cat Whisker electrode, means for biasing the emitter electrode with respect to the base electrode fuithest removed therefrom to produce a current flow across the bridge-like portion in a given direction, and means for biasing the collector electrode with respect to the base electrode furthest removed therefrom to produce a current flow across the bridge-like portion in the same direction as said given direction.

References Cited in the file of this patent UNITED STATES PATENTS