Feb. 28, 1933.
1,899,758
K. w. JARVIS
AMPL-IFYI‘NG SYSTEM
Filed July 17. 1926
Fig. 2.
INVENTOR
WITNESSES I
Ken/76777 W Jafv/s.
'
ATTORNEY
Patented Feb. 28, 1933
>
' 1,899,758
UNITED STATES PATENT OFFICE
KENNETH W. JARVIS, OF vCINCINNATI, OHIO, ASSIGNOR TO WESTINGHOUSE ELECTRIC &7 > »
MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA
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AMPLIFYING SYSTEM
Application ?led July 17, 1926. Serial No. 123,211.
My invention relates to amplifying sys
10
methods.
15
Fig. 4 is a diagram of the same circuit as
tems, and it has particular reference to sys
of Figure 2, illustrating the application
tems employing thermionic tubes, either as that
of a preferred form of my invention thereto.
audio or as radio-frequency ampli?ers.
In all views, like elements are similarly
One object of'my invention is to provide numbered.
'
means for preventing, in thermionic tubes
Referring
speci?cally
to
Figure
1,,a ther
and the circuits associated therewith, the mionic tube 1 having a ?lament 2, a grid 3
parasitic, ultrahigh-frequency oscillations and a plate 4, is provided with an input cir-v
which tend to occur under certain conditions. cuit comprising a portion 5 of an inductor 6,
Another object of my invention is to pro— located between a connection 7 leading to th
vide means for the prevention of parasitic grid 3, and a connection 8 leading to the ?la
oscillations in ampli?er circuits that have al ment 2. The inductor 6 is shunted by a con
reac y been partially neutralized by known denser 9 for the purpose of tuning.
55
60
7
to the input circuit, is an inductor
A still further object of my invention is to 11,Coupled
which may be a source of signal fre 05,
provide means for the prevention of para quencies,
either radio or audio.
sitic oscillations at frequencies above those
The tube 1 is provided with an output cir
to which the circuits associated with an am cuit connected between the plate 4; and the
pli?er system are normally tuned.
2, comprising an ‘inductor 12 and a
Numerous attempts have been made to de ?lament
source of plate potential 13.
7
70
vise circuits' which would prevent oscilla
An inductor 14 coupled to the output cir
tions from spontaneously starting in circuits cuit inductor 12, enables variations in the
associated with thermionic-tube ampli?ers,
output current to be'impressed on the input
especially when such circuits are being used
of a succeeding ampli?er stage.
251 in the ampli?cation of high-frequency sig circuit
A
source
of potential 15 for the ?lament 75
nals.
,
is provided, as is also a potential source 16
None of the systems known to the prior for the proper biasing of the grid 3. Con
art have proved entirely successful, there be nected between the plate 4: and an end 17 of
ing always a tendency for the tubes to oscil
so late at ultra-high, parasitic frequencies, no’ the input inductor 5 remote from the grid
connection, is a small condenser 18, which, 80
matter how carefully the circuits have been taken
in conjunction with a portion 19 of
neutralized against oscillation at the fre the inductor lying between the ?lament con
quencies lyipg in the normal tuning range nection 7 and the end 17, provides means for
thereof.
35 According to my invention, I provide neutralizing the tube 1 against oscillating at
‘any frequency determined by the setting of 85
means, in the nature of reverse~feed~back the tuning condenser 9.
coils, which are so arranged that all tendency
The circuit thus far described and illus
of an amplifier circuit to oscillate at para trated is the now well known'“Rice” circuit,
sitic frequencies is nulli?ed.
v
shown in the United States patent to Rice,
In order that a complete understanding of No.
1,334,118, to which referenceshould be 90
my invention may be had, the following de—
scription should be read in connection with
In the patent referred to, a-statement is
the accompanying drawing.
made that, in order to obtain perfect neu
in the drawing, Figure 1 is a. diagram of
45 a well-known type of neutralized ampli?er tralization, it is necessary that unity coupling
be had between the two portions of the input 95
made.
circuit,
Fig. 2 is a diagram of the same circuit as
50
'
inductor.
.
'
F
'
.
This statement, according to my experi
that of Fig. 1, in a different form,
ments, is not necessarily true if the fre
Fig. 3 is a diagram of the same circuit, the quencies determined by the setting of the tun- ‘
tuning condenser being omitted,
ing condenser be the only frequencies con
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1,899,758
2
back at parasitic frequencies are approxi—
sidered. For suoh'frequencies, it is not even
neutralized.
necessary that the filament connection be mately
Usually,
in practice, the separate induc
made at the exact center of the input induc tors 5 and 19 form parts of single inductor,
tor, nor is it necessary for the two portions
shown as the inductor 6 in Figure 1., It is
accordingly obvious that the total inductive
at all. in fact, the circui may be arranged effect of the ‘iJ‘WO reverse-feedback inductors
as shown in w
be effectively
of such ind .ctor to be ,
inductive relation
comp .nsatcd
i 1 ingcondenser,
on the tuned circuit cor.=..prisinry inductor 6
-
.
9 is substantially Zero, and. 75
insuch event,
separate portions of and condenser
not decrease the signal intensity. ‘
the input inductor are coupled suf?ciently does
My invention is capable of use in connec»
'
‘ effect of the tuning
through
resonatin
tion with many differ rig types of circuit, and’
condenser.
,
if the circuit of Fig. 2 is nov:r considered
15
is not to be considered restricted to use with
illustrated in
1.
in relation to ultra-high freouencies above theBycircuit
my invention, ll. arn enabled to con
those determined by the tunii g condenser, it truct an ainpliz'i er having either one or a plu
is obvious _. t the tuning condenser 9 offers
80
..
>2)
rality of stages, ivi'a complete assurance‘
substantially Zero impedance to these fre that none oft-he stages Win oscillatespon
quencies. fig. 2 may, accordingly, be re ' ieously ultra-high parasitic frequencies.
drawn as in Figure 3, with. the tuning con
denser elii hated, and the two portions of
the inductor in parallel with respect to the
.y invention is, tlierefoh, of importance in
85
I
,. ‘ion with the present
trend‘ toward
ub'e tuned radio-frequency amplifiers
grid and filament of the tube.
I
in
which
parasitic oscillations practically
lit is obvious teat, under certain condi always tend to be set up.
tions, the circrit saoivn in Figure 3 is cap~
Although I have illustrated and'de'scribed
able of oscillatin
very high frequencies but single speci?c form of my invention,
25
determined by he l
reactance of‘ the it will be obvious to those skilled in the art
~ jne grid-filament that many modi?cations thereof are possi
inductors 5 and 19,
35
capacity of the tube,
necessary feedlbacl: ble. My invention is accordingly not to be
using supplied both by the plate grid ca limited except insofar as is necessitated by
pacity inside the tube,
the neutralizing the prior art or by the appended claims.
condenser itself.
l claim as my invention:
, V
1. In thermionic-tube amplifier, ineans
‘With unit] co iling between the inductors
5 and 19, the induc t ve reactance of the two ‘for preventing self-oscillation including a
1
effective grid induc capacity between certain of the elements of
40
, be reduced to Zero, said tube, and independent nieans providing
preventing potential, changes on the grid additional coupling between said elements,
caused by variations in the output current. said coupling being inductive in character,
in practice, however, such unity coupling is whereby the spontaneous generation of para
substantially impossible ofattaininent, and sitic oscillations at ultra‘ high frequencies is 1.9.5
the circuit will accordingly oscillate at very
high frequencies, as before explained.
prevented.
‘
v
_
2. In a circuit comprising a thermionic
In order to 1; ‘ever vparasitic‘ oscillations, l tube, means for preventing self-oscillations
in said circuit, such means comprising; ca
I.
have discovered that it is necessary to com
45
pensate the lacl: of unity coupling; int-he cir pacitive coupling between certain of the ele 1.19
means, including
cuit under consid zion by introducing into ments of the said tube,
each portionor '
gut'inductor a ?n}: ap~ a plurality of inverse-feedback inductors,
proximately equal
opposite to
set up for increasing the range of frequencies over
by the feed-back oupsng ins-Thfrequencies. which the circuit is prevented from oscillat» 1.1.5
lieferr rig spec-i
.
1g. 4, this is a
diagrammatic view _. a pr'ferrel form of
my invention as aoplied to
lent to that ill at
‘
'
circuit equiva
' *. 2.
~
inc‘.
7
.
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3. in a circuit comprising a thermionic
tube having an input circuit and an output
circuit, capacitive coupling means between
ilate circuit of said circuits for preventing self oscillation, al c;
the therinionic
.e a plurality of and, independent inductive coupling means ‘
reverse-f ed-bac;
., 2
23, the also between said circuits for the prevention
inductor 12 being; 1
I. to the grid-lila of parasitic oscillation at ultra-high fre
nient portion 5 of '
motor 6, and the quencies.
In combination, a thermionic tube hav
other inductr .:
coitipled to the plate
.c-* r
The di~ ing a ?lanient a plate and grid, an input 1.5-‘
ircuit comprising an inductor associated
' luctors,
with
said
and filament, incans capaci
‘
of
each
inductor
and 1e amount of coupl" ,,
coupling said plate to said input cir
to the corresponding portion of the inductor tively
cuit for too prevention of oscillations over
c
ial s set up
6 are so chosen tha; the potent
the tuning range, and additional independ- 129
across each portion of theinductor 6
serially
1
to-
111?
/.
60
rectiono
‘
i
p
1
1,899,768
ent means comprising a plurality of induc
tors connected to said plate and coupled to
said input inductor for the prevention of
parasitic oscillations.
5. In combination, a thermionic tube hav
ing a ?lament, a grid and a plate, an input
circuit comprising an inductor associated
with said tube, means comprising a con
10
denser and a portion of said inductor for
neutralizing the effect on said input circuit
of variations in potential of said plate, and
additional means connected {to said plate
and inductively coupled to said input cir
15
cuit, for preventing the tube and associated
circuits from oscillating spontaneously at
parasitic frequencies.
6. In combination, a thermionic tube
having a ?lament, a grid and a plate, an in
ductor connected between said grid and ?la
ment, a second inductor connected between
said plate and ?lament for the prevention
of self-oscillations over a given tuning
range, said connection including a con
25
30
denser, and additional inductors connected
to said plate and coupled to said ?rst men
tioned inductors for the prevention of para
sitic oscillations outside of the tuning range.
7. In combination, a thermionic tube hav
ing a plate and a grid, an input circuit for
said tube comprising an inductor, one end
of said inductor being connected to said grid
and the other end of said inductor being con
nected to said plate through a condenser,
means for inductively coupling said plate
35
to said input circuit, said means being so
arranged that the total inductive effect on
said input circuit is zero at frequencies cor
responding to desired signals, but is not zero
40
nals.
at frequencies above those of desired sig
8. In combination, a thermionic tube,
having a ?lament, a grid and a plate, a
45
thermionic tube provided with an input in
ductor having a plurality of sections which
are effectively in parallel at very high fre-'
quencies, and means comprising a plurality
of inductors connected to said plate and so
coupled to said input inductor that parasitic
oscillations are prevented from being spon
taneously generated.
a
9. In an inherently oscillatory thermionic
tube ampli?er, feed-back means for prevent
ing self oscillation over the range of fre
quencies for which said ampli?er is designed
' and additional feed-back means for prevent
ing self-oscillation at frequencies above said
range, one of said feedback means being ca
pacitive and the other inductive in character.
In testimony whereof, I have hereunto sub
60
scribed my name this 28th day of June, 1926.
KENNETH W. JARVIS.
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