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Publication numberUS2323966 A
Publication typeGrant
Publication date13 Jul 1943
Filing date7 Oct 1938
Priority date7 Oct 1938
Publication numberUS 2323966 A, US 2323966A, US-A-2323966, US2323966 A, US2323966A
InventorsMaurice Artzt
Original AssigneeRca Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
US 2323966 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

M. ARTZT July 13, 1943.

AMPLIFIER .Filed Oct. '7, 1938 Cl/OPPIR 70/75 INPUT 2.5. ourPuT "w n b v i J H HOPPER 70/1/15 lAPU 7' W Y Ri XJ M m .m W% VM M ma" Patented July 13, 1943 AMPLIFIER Maurice Artzt, Haddoniield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 7, 1938, Serial No. 233,701

1 Claim.

The present invention relates to amplifiers and particularly to amplifiers of the so-called direct current type.

It has been known in the art that the direct current type of amplifier is desirable for many purposes, such, for example, as to amplify relatively weak photoelectric tube outputs and for measurement purposes, but in many instances it has been diflicult to obtain good stability or efficient operation'from such type of amplifier systems. Unstable and inefiicient operation of such amplifiers makes their use undesirable, as a general rule, for the purposes set forth, but where it is possible to provide an amplifier of such character which is substantially absolutely stable in its operation there is wide application for its use in the transmission of facsimile representations as well as for the use for measuring devices and other general applications.

According to the present invention there has been provided an inherently stable direct current amplifier system capable of amplifying small direct current voltages. Such an amplifier has its non-drift characteristics made possible by the use of alternating current couplings throughout and by the provision of a suitable means for chopping the direct current input at a frequency considerably higher than the frequency of any variation in the direct current signal which is to be amplified. With such an arrangement of circuit elements the output of the alternating current amplifier is a tone frequency modulated by the direct current with the amplitude of the modulated tone varying in direct proportion to the direct current I input to the system. Many and various ways may be provided for providing the chopping" action abovementioned but one suitable arrangement which will be particularly described herein is an impedance changing bridge network. When the impedance chan ing bridge network to which the direct current energy is applied causes the development of the modulated tone such tone may later be rectified to obtain thereby the amplified direct current signal.

From the foregoing it can be appreciated that one of the main objects of this invention is that of providing a conveniently operating and emcient means for amplifying direct currents.

Other objects of the invention are those of providing electrical networks for amplification purposes which shall be stable in their characteristic and capable, at the same time, of amplifying small currents Without drift.

Still other objects of the invention are those of providing an electrical network for the above stated purposes which is relatively simple in its arrangement of parts and which may be set up and operated in a minimum amount of time and at a minimum of expense, I

Other objects and advantages of the invention will naturally become apparent-and at once suggest themselves to those skilled in the art to which the invention is directed by reading the following specification and the accompanying claim in connection with the drawing illustrating typical circuit arrangements wherein:

Fig. 1 represents one form of the amplifier system which is particularly adapted to the amplification of photo-electric currents in a facsimile system; and,

Fig. 2 is a somewhat simplified single side system which is particularly suitable and useful for measurement purposes.

Referring now to the accompanying drawing for a further understanding of the invention, and first to Fig. l thereof, the photoelectric tube II which is subjected to light of varying intensities in thetranslation of the light values of a subject into electric current impulses for the production of facsimiles, for example, (all as is well known in the art) is so connected that'its anode element l3 connects to the positive terminal of a source l5 having its negative terminal preferably at ground potential through the indicated connection at IT. The cathode or light sensitive element IQ of the phototube H is connected to the positive end of the resistor element 2|, which has its negative terminal connected to the ground potential point ll.

At the terminal points 23, 23 there is supplied a chopper tone frequency of suitable value which is impressed upon the amplifier through the transformer 25 which has its secondary Winding 26 center tapped to ground I! by the connection 21. In this way the tone impressed on the terminals 23 is supplied to each of the control electrodes 28 and 29 of a pair of sw tching tubes 30 and 3|, in phase opposition. The plate or anode elements 32 and 33 of the tubes 30 and 3i connect with one end of resistor elements 34 and 35 which have'their opposite ends connected to the positive terminal of the resistor 2!.

The tone frequency supplied to the control electrodes 28 and 29 of the tubes 30 and 3| is fed from the opposite ends of the transformer secondary wind ng 26 by way of the resistor elements 36 and 31 and is thus applied to the tubes 30 and 3i in phase opposition.

Output energy from the tubes 30 and 3| is fed by way of the direct current connection 38 and 39 to energize the control electrodes 40 and I 4| of the tubes 42 and 43. Output energy from the plate or anode'elements 44 and 45 of the tubes 42 and 43 is supplied to the anode circuits of these tubes so as to be fed through the primary winding 46 of transformer 41 to energize the secondary circuit 48 thereof from which the modulated output of the phototube H is supplied to any desired form of utilization circuit or transmitter (not shown).

Suitable operating potentials for the tubes 42 and 43 are supplied from a suitable source of voltage connected between the terminal points 49 and 50 with the positive terminal of the source connected at the terminal 49. Cathode bias for the cathode elements and 52 of tubes 42 and 43 is supplied through the resistor element 53 shunted by the by-pass condenser 54.

In the circuit described above it will be seen that the direct current output of the phototube appears across the resistor 2| which is polarized as indicated by the drawing. The switching tubes 30 and 3| are so connected as to use this voltage across resistor 2| as the source of anode voltage through the series resistors 34 and 35. The chopper tone frequency applied to the control electrodes 28 and 29 of these tubes 30 and 3| serves alternately to drive these tubes to saturation and to cut-oil so that the plate impedance of these tubes is alternately substantially infinite and very low in comparison to the resistors 34 and 35. Thus, when the tube 36 has infinite plate impedance the tube 3| has very low impedance, Under such'circumstances the voltage upon the control electrode 4| of the tube 43 is effectively short circuited by the tube 3! and the full direct current voltage across the resistor 2| appears upon the control electrode 46 of tube 42. On the next half cycle of the chopper tone frequency input upon the terminals 23 the grid or control electrode voltage on the tube-42 will be effectively short circuited so that the full direct current voltage across the resistor 2| will be impressed upon the control electrode 4| of the tube 43.

The input to the tubes 42 and 43 will, therefore, be rectangular shaped waves of direct current on alternate half cycles; the amplitude of the applied voltage being proportional to the direct current input upon the-system and the duration of the pulses determined by the chopper tone frequency.

This output voltage can readily be amplified by an alternating current amplifier system as a modulated wave and later rectified, if desirable.

Under such circumstances the chopper tone frequency may be adjusted by suitable means (not shown) so as to send facsimile signals as an amplitude modulated wave.

By the arrangement of Fig. 2, there is shown a modified circuit of a considerably simplified nature to work as a so-called one side system which is particularly useful for measurement work. In this arrangement of the system, the direct current input, which may be such as the photoelectric tube ll of Fig, 1 or other suitable source, is supplied at the terminal points 5| between which is connected the load resistor 2|, as is the arrangement of Fig. 1.. In this way anode or plate voltage for the tube 30 is provided through the resistor 34 and the tube is caused to become conducting under the control of the chopper tone frequency supplied to the control electrode or grid 3| of the tube 36 by way of the secondary winding 26 of transformer 25 and the resistor 36.

The anode 32 of tube 30 is connected to one side of a coupling condenser 53 whose opposite terminal connects to the control electrode or grid element 55 of the tube 56, across whose input circuit is the leak resistor 51. The cathode 58 of the tube 56 is biased by the cathode resistor 59 which is shunted by the by-pass condenser 60. The output energy is fed by way of the resistance coupling which includes the plate or anode resistor 6|, the coupling condenser 62 and the leak resistor 64 to the rectifier 66. The output energy from the rectifier 66 is supplied across the output or load resistor 68, suitably shunted by the bypass condenser 69, to the output terminals 10, 10.

In the arrangement of Fig. 2, the direct current input is applied to the terminals 5| which connect across the resistor 2|. Such an input may be of the same general type as that disclosed by Fig. 1 or any of the various known types of direct current input and variable intensity as desired and in accordance with varying values of light, current, voltage and the like.

With chopper tone applied at terminals 23 the tube 30 is caused alternately to become conducting and non-conducting. When tube 30 is conducting it derives its plate potential from the potential drop across resistor 2| which represents the input signal. When conducting, tube 30 acts as a low impedance across the network consisting of the capacitor 53 and the resistor 51, effectively short-circuiting the input to this network. When non-conducting, the input to 63 and 51 is raised to the level of the potential drop across resistor 2|. Thus the input to 53 and 61 is alternately equal to the signal across 2| and then zero, and the control grid 55 follows this alternating off-on signal.

The coupling network 6|, 64 and 62 couples this square wave output of tube 56 back to ground level, where it is rectified by diode 66 to obtain the direct current signal envelope. This appears as a potential across resistor 68 and capacitor 69.

Thus, with plate current flowing through the rectifier 66 the condenser 69, which is included in the integrating circuit including resistor 68, becomes charged and the magnitude of the charge acquired to be appreciated will be proportional to the direct current input voltage applied to the terminals 5|. During the inoperative periods of the tubes 66 the condenser will discharge to a predetermined reference value (determined by chosen circuit parameter) after which the charge will, during the next half cycle of the chopper tone input, be built up and applied at 23 to the output terminals 10 as before.

From the foregoing, it is apparent that many modifications and changes may be made provided and, accordingly, various modifications may be made without departing from the spirit and scope of the invention provided such modifications and changes fall fairly within the spirit and scope of the claim hereinafter appended.

What I claim is:

An amplifier system comprising a light translating element serving as a source of variable and direct current, a pair of thermionic tubes each having a cathode, anode and at least one control electrode, a separate load impedance associated with each of the thermionic tubes, each of said load impedances having one terminal connected to the anode element of the associated thermionic tube and the other end connected directly to receive the output energy from the light translating element whereby the voltage instancontrol electrode, a direct current connection bephase relationship, said tone frequency being of such value as to drive the said tubes alternately between cutofi and saturation, a pair of pushpull connected thermionic output tubes each comprising a cathode, anode and at least one tween the anode electrode of each of the first named pair of tubes and a control electrode of each of the second named pair of tubes, whereby the control electrode of each of the second named pair of tubes has its potential influenced by the output voltage from the light translating element and the potential of the control electrodes of the push-pull tubes is caused to vary between relatively wide limits by the applied tone frequency energy, and a load circuit connected to receive the output of said tubes.


Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2456420 *31 Aug 194614 Dec 1948Gen ElectricElectronic direct-current control system
US2510742 *3 Mar 19486 Jun 1950Arthur Nosworthy TElectronic control
US2574690 *12 Mar 194713 Nov 1951Rca CorpAmplifier-rectifier circuit
US2620441 *24 Oct 19462 Dec 1952Sperry CorpElectronic signal mixer
US2651746 *17 Aug 19458 Sep 1953Kearney & Trecker CorpControl device
US2682624 *19 Dec 195229 Jun 1954Tung Sol Electric IncLight-sensitive circuit
US2802106 *14 Nov 19456 Aug 1957Page Robert MSignal converter system
US2846522 *18 Feb 19535 Aug 1958Sun Oil CoDifferential amplifier circuits
US2876725 *6 Sep 195610 Mar 1959Du PontSolder-free cemented body-seamed sheet metal container and method of fabricating the same
US2918583 *4 May 195522 Dec 1959W M Welch Mfg CompanyApparatus for measuring radiant energy at very low levels
US2922051 *5 Apr 195419 Jan 1960Westinghouse Electric CorpLow voltage inverting device
U.S. Classification250/214.00R, 330/10, 327/306
International ClassificationH03F3/38, H03F3/40
Cooperative ClassificationH03F3/40
European ClassificationH03F3/40