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Патент USA US2137278

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NOV- 22, 1938-
‘ R. H.‘ GEORGE ET AL‘
2.,137,278
AMPLIFIER’ SYSTEM
Filed Sept. 30', 1935
‘
INVENTORS
T ORNEY
2,137,278
Patented Nov. 22, 1938
UNITED STATES PATENT OFFICE
‘ 2.137378"
AMPLIFIER SYSTEM.
Roscoe H. George and Howard J. Helm; West‘ '
Lafayette, Ind., assignorsito-dRadio.Corporation.
of America, a. corporation. of; Delaware‘.
Application September 30,.1935',,'S'eriallN'o. 42,817
4 Claims.
(01; 250-415)
nectedinserieswith abattery I51 and resistor I‘!
particularly to ampli?ers which are useful in so that dueto- varying conditions of light falling
upon the photocelLvarying voltage drops take,
connection with television and picture transmis
sion systems, although the use is in no sense place in, the. resistor l1. Connected across the
terminals. of’ the. resistor element I1.‘ is the ?rst.
limited speci?cally to such types of systems.
stage of, the ‘amplifier system. This ?rst stage of
In television systems it has been found fre
quently to be desirable to resort to the so-called the ampli?er islso connected that‘ the input circuit
D. C. ampli?er type of system where itis desired comprising the‘grid-cathode circuit of the tube
to‘hold the picture level or background at any l9, connectsto. opposite terminals-of the resistor
10‘ particular point. When using a D. C. ampli?er IT‘ and'the. control’grid'is appropriately biased by
in such systems it is possible to transmit in way of. a biasingybattery 2|. The output circuit.
of ‘the tube l9 includes the anode electrode of the
correct relationship to the entire picture‘ con
tube, the resistor 23‘ andthe plate supply source
tinued’ along dark or light portions of the sub
ject, whereas in the so-called A. C. ampli?er type 25. ‘Across opposite terminals of the resistor 23
15.‘ of system it is necessary to provide special ways. through which varyingvoltage drops take place
and meanswhereby the D. C. component of the in accordance with. the current flowing through
picture or subject may be added to the picture. the tube l9v (as determined by the potential of
This is. preferably accomplished at the receiving that. terminal‘ ‘offthe, resistor l1 connected ad
end of the system and the compensation may be jacent the control grid‘ of the. tube, I9), is, con-’
‘ under the. control‘of the synchronizing impulses nected' the inputcircuiti of the secondstage of
the ampli?er which comprise‘s'the tube‘ 21. The
25 or some other portion of the signal.
Another advantage to be obtained through the tube 21., for example, may consist, ‘like the tube
The present. invention relates to amplifiersand
10;
'
15;
N) 5,
use of a direct current ampli?er system is that a _ I9, of" three or‘more, electrodes of which one is
small change in- the direct current or voltage at an electron emitter. and another is an anode.
While we have shown in the accompanying 0
the input terminals of the ampli?er may be rep
resented by a large change in direct current or illustration tubes of the triode ‘type, it is to be
understood that we may also utilize tubes of the
voltage at the output terminals without dis
so-called screen grid, pentode, hexode, and other
tortion.
The above and other objects are those sought types, or we may use any desired multi-purpose
. to be attained by the present invention, although tubes provided other characteristics of the in—
35 we do not in any way limit ourselves to any or all vention remain unchanged.
The tube 21 includes in its output circuit the
of the foregoing objects or advantagesv of such a
tube
anode, the resistor 29 and the source of
system as is disclosed herein.
For the purpose of illustrating our invention, abode voltage 3| similarly to the tube l9. In
contrast to the arrangement by which the con- 40
40 we have shown by diagrammatic sketch embody
ing the single ?gure of the drawing one form .trol electrode of the tube I9 is biased by the
which the said invention may assume and have battery 2|, we have provided an arrangement
con?ned the illustration only to the ?rst two wherein the tube 21 is appropriately biased by
stages of an ampli?er of the character above means of the plate battery of the tube I9 of
which the positive terminal is connected to an 45
>
described.
‘ If reference is now made to the drawing, it intermediate point 33 on the source of plate po
will be seen that light representing di?erent suc
tential 3! for the tube 21. All succeeding stages
cessive elemental areas of the subject I is caused (not shown) of the ampli?er are preferably
to fall upon a photoelectric cell or other suitable biased in the same manner as that provided for
50 light translating element 3 by scanning the i1
luminated subject, for example, by means of a
rotary scanning disk or other equivalent element
5 such as a cathode ray tube, oscillating mirror or
the like. The subject I, for example, may be
55 illuminated from a source ‘I by way of an optical
system 9 and the light from the subject, in turn,
is directed by way of a second optical system 13,
the light passing beyond the scanning element is
caused to fall upon the light sensitive photo
50 electric cell 3. The photoelectric cell 3 is con
the second stage.
‘
0
In order to shield different sections of the am
pli?er with respect to each other, there are pro
vided separate shielding boxes 35 for each stage
and the positive terminal of the plate voltage 55
supply for each of the tubes l9 and 2?, as shown,
is connected to one of the shielding boxes 35.
An outside shield box 31 is also provided for
housing each of the initial shield boxes in order
to provide full and complete shielding for all 60
2
2,137,278
stages of the ampli?er. The outer shield box 31
is preferably grounded at 39.
With the arrangement hereinabove shown,
there results an ampli?er which is of extreme
stability in operation. All succeeding stages of
the ampli?er are connected to the output ter
minals 4| 0]: the terminals 41 may connect di
rectly to the modulator and thence to the trans
mitter.
10
.
.
Having now described the invention, what is
claimed and desired to secure by Letters Patent
is the following:
1. A multi-stage ampli?er system comprising a
plurality of cascaded thermionic tubes, a source
15 of anode voltage for each of said tubes, means
for controlling the output current from the ?rst
of said tubes in accordance with a variable quan
tity so as to control thereby‘ the current ?owing
through subsequent tubes, means for biasing the
20 second tube of the series from the source of anode
voltage for said tube, separate electrostatic shield
ing means surrounding each of said tubes, a con—'
nection from the positive terminal, of the anode
voltage source for each tube to said shielding
25 means, and a second shielding means surrounding
all of said tubes and the individual shields there
for and insulated from the ?rst named shielding
means.
'
2. A multi-stage ampli?er comprising a plu
30 rality of directly connected thermionic tubes,
means for controlling the output current from
3. In a multi-stage ampli?er comprising a plu
rality of directly connected thermionic tubes,
means for controlling the output current from
the ?rst thermionic tube in accordance with light
modulations, means for controlling the output
of the following tubes in the system in accord
ance with the output of the ?rst tube of the
series, means for biasing each tube of the series
from the source of anode voltage for the selected
tube of the series, separate electrostatic shield 10
ing means enclosing each stage of the ampli?er
and joined to the positive terminal of the anode
voltage source for said stage, thereby placing said
shields at a potential relative to the cathode
of at least one of the tubes which is progres
15
sively higher from the ?rst tube, and a second
shielding means surrounding the entire ampli?er
and insulated from each of the individual shields,
said second shielding means being maintained at
ground potential.
20
' 4. In a multi-stage ampli?er comprising a plu
rality of directly connected thermionic tubes,
means for controlling the output current from the
?rst thermionic tube in accordance with light
modulations, means for controlling the output of 25
the following tubes in the system in accordance
with the output of the ?rst tube of the series,
means for biasing each tube of the series from
the source of anode voltage for the selected tube
of the series, separate electrostatic shielding 30
means enclosing each stage of the ampli?er and '
the ?rst thermionic tube in accordance with light 1 joined to the positive terminal of the anode volt
modulations, means for controlling the output
of the following tubes in the system in accord
ance with the output of the ?rst tube of the
series, means for biasing each tube of the series
from the source of anode voltage for the selected
tube of the series, separate'electrostatic shield~
ing means enclosing each stage of the ampli?er
40 and joinedvto the positive terminal‘ of the anode‘
voltage source for said stage, and a ‘second shield
ing means surrounding the entire‘ ampli?er and
insulated from each of the individual shields, said
second shielding means being maintained at
45 ground potential.
age source for said stage, thereby placing said
shields at a potential relative to the cathode of
at least one of the tubes which is progressively 35
higher from the ?rst tube, a second shielding
means surrounding the entire ampli?er and in
sulated from each of the individual shields, said
second shielding means being maintained at
ground potential, and shielding means separat
ing each of the separate electrostatic shielding
means’ enclosing each stage of the ampli?er and
' insulated therefrom.
ROSCOE H. GEORGE.
HOWARD J. HEIM.
45
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