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Патент USA US2411362

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Nov. 19, 1946.
J. R. BOYKIN
‘
2,411,362
SHAPED AMPL IFI ER
Filed April 1, 1944
15
/4
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7
?mll ll LIIIF
A
13
m
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WITNESSES:
MWM
INVENTOR
John R Boykin.
BY
ATTOR
2,411,362
Patented Nov. 19,‘ 1946
UNITED- STATES PATENT‘ OFFICE _
SHAPED AMPLIFIER
John R. Boykin, Baltimore,‘ Md" assignor to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application April 1, 1944, Serial No. 529,109
4 Claims. -(Cl. 179-171)
2
1
My invention relates to electronic ampli?ers
and, in particular, relates to the reduction in the
ripple produced in the output current of such am
pli?ers by causes such as the effect of alternating
heating current for the cathode, ?uctuations of
cathode emission and the like. It is particularly
applicable to ampli?ers having cathodes directly
heated by alternating or pulsating current of a
frequency greater than that impressed from the
.
put circuit which otherwise would be produced
by the cathode heating current.
Another object of my invention is to provide
a circuit for an electronic ampli?er tube which
shall make it possible to effectively amplify
?uctuating currents impressed upon its input
circuit while at the same time substantially elimi
nating ?uctuations in its output circuit due to
?uctuations f electron emissivity of its cathode.
Still another object of my invention is to pro
10
input circuit of the tube.
vide a circuit for electronic ampli?er tubes hav
For certain purposes in the electronic art, it
ing cathode ?laments directly heated by alter
is desirable to use electron tubes having cathodes
nating current of a frequency greater than the
of what may be termed U-shape which are di
voltage ?uctuations impressed on their input cir
rectly heated by alternating current. It‘ is also
known that such alternating-current heating
tends to produce ?uctuations of the output cir
cuit current which may be referred to as “hum”
which are naturally in undesirable interference
with the action of the tube when it is used, to am
cuits and which shall amplify the last-mentioned
voltage ?uctuations, while at the same time sub
stantially eliminating the hum in their output
currents which would normally be caused by their
cathode heating currents.
Other objects of my invention will become ap
plify a signal input current. In the prior art, 20 parent upon reading the following description,
the magnitude of this hum has been greatly de
taken in connection with the single ?gure of
creased by connecting the common terminal of
drawing which illustrates a three-electrode elec
the control-electrode circuit and the plate cir
tronic ampli?er tube connected up with a circuit
cuit to a point on the heater circuit which is at
the mean value of the potential between the cath
ode terminals. This connection is usually made
by attaching the control electrode and plate cir
cuits to the midpoint of a resistor which spans
the cathode terminals. It is also known that
hum effects are produced by the magnetic ?eld
and the potential drop along the ?lament be
tween the terminals of the cathode; and that by
properly proportioning the magnitude of these
e?ects, their resultant hum in the output circuit
can be nearly eliminated.
'
‘
. However, it is frequently impracticable to make
embodying the principles of my invention.
‘
Referring in detail to the drawing, an elec
tronic ampli?er tube l, which may be of the high
vacuum type and is shown here as embodying an
anode 2, a control electrode 3 and a cathode 4,
comprising‘ a U-shaped electron-emissive ?la
ment 4 is supplied with alternating heating cur
rent‘ from an alternating current source 5. To
take one example, the frequency of the source 5
may be 800 cycles per second. The terminals of
the ?lament 4 immediately ‘outside the tube l are
spanned by a resistor 6 having a tap ‘I positioned
as‘ closely as possible to its electrical midpoint.
An input transformer‘ 8 impresses a ?uctuating:
the point of attachment to the resistor spanning
signal voltage which may, for ‘example, have a
the cathode terminals at its exact electrical mid-*
point, and likewise impracticable in quantity pro 40 frequency of 150 cycles'per second in the control
electrode 3 by means ‘of its secondary winding‘
duction to produce tubes in which the other
sources of hum above mentioned are ideally re
9,‘ one terminal of which is connected to the con
trol electrode 3 and its other terminal connected‘
duced to zero.
through a bias battery I l to the above-mentioned
In accordance with my invention, however, I
have found it possible to substantially eliminate 45 tap 1. The anode 2 is connected through a 're-Q‘
sistor l2 to the positive terminal of a voltage’
the residual hum eifects mentioned in the pre
source l3, of which the negative terminal is con
ceding paragraphs by the circuit connections
nected to‘ the tan 1. A load may be supplied from
shown in the drawing and about to be described.
the voltage drop across the resistor l2, prefer
One object of my invention is, accordingly, to
provide circuit connections for an electronic am- 50 ably through a blocking condenser 14 in a man
ner too well known in the art to require further
pli?er having a cathode ?lament heated with al
ternating current which shall enable the tube to
ei?ciently amplify ?uctuating voltages impressed
description here.
The ?ow of the alternating heating current“
through the cathode 4 will alternately make the
on its input circuit, while at the same time sub
stantially eliminating the hum e?ects in its out- 65 respective end terminals thereof positive and
2,411,362
negative relative to each other.
4
However, the
The arrangement of the capacitor l5 and the
electrical midpoint of the ?laments, being always
secondary winding 9 may be considered to con
half way in potential between those of the re
stitute an inverse feed-back from the plate cir
spective terminals, will remain ?xed throughout
cuit to the grid circuit which tends to increase
the heating cycle at a Value intermediate be (Z the stability and'decrease distortion in the ampli
tween them; If the tap point 1 is exactly at the
?er I. This inverse feed-back will, in fact, tend
electrical midpoint between the terminals of the
to reduce the effect of disturbances in the plate
cathode it, it will likewise remain at the same
circuit of the tube I.
‘
~
'
?xed potential‘a's the midpoint of the cathode
' In accordancewith the provisions of the patent
itself, and under such circumstances, no voltage
statutes, I have described a particular embodi
having the frequency of the supply 5 is effectively 7 .I ment
of the principles of my invention, but these
impressed between either the control electrode 3 .
principles are obviously of broader application
or the anode 2 and the cathode 4. However, ifv ' in ways which will be evident to those skilled in
the tap point ‘I is displaced from the electrical
the art.
7
midpoint of the resistor 6, a-voltage having. the
frequency of the supply 5 can be shown to be ‘ ~
impressed between both the control electrode 3
and the anode 2 and cathode 4. " This will result
- . I claim as .my invention:
1. In combination‘ with an electron tube having
an anode, at least one control electrode and an
electron-emissive cathode, an inductive winding
in the production in the output resistor '12 of a
connectédbetween said control electrode and said
current having the frequency of the source 5.
20 cathode, and a capacitor connected between said
.In accordance. with my invention, I connect. a
capacitor 15 between the. epntrpl. electrode 3. and.
the enede 2- This. effect! makes the. tube, 1
act‘lilse 2,» reactance tube. and interpeses between
the. 'qqntrql. .81? trade 3 and the cathode. 4 an
efie tire capacitance. which is. equal to ILC, where
C is the. capacitance. of the capacitor i5, and P!
is the. voltage ampli?cation of the. electron. tube. I .
The i duetance of the secondary windingt. is
preierably tuned. with this effective capacitance
#0
Control electltqde. andsaid. cattle, the inductance.
of said winding being made such as to resonate
at the frequency of input voltages impressed on’ ‘
said winding with n times the capacitance of said
capacitor, where n is the voltage ampli?cation
of said tube.
"
2. In combination with an electron tubehaving
an anode, at least one control electrode and an
electron-emissive cathode, a circuit for heating
said cathode from a source of periodic current,
resonate. at the frequency impressed by the 30 an inductive winding cojnlilectedv between .said
trensiormer 8.; .i, e.-
the. present example, is
tuned. to. resonate at 1.50 cycles.
Under such circumstances, the. secondary Wind-
control electrode and a, point on said circuit, an
output circuit connected between said anode.‘ and
the last-mentioned point, and a capacitor con
111%; 5t and the. capacitor i5. can beshown to. con. 35 nected between said,‘ control electrode and said
Stitutea low-pass. ?lter of theL type. for currents.
havinethe frequency of the supply source. 5,, and
3. In combination with an electron tube having
wraps’ higher harmonics thereof. Because Of
an'anode, at least one control electrode and a
the resonance to the frequency supplied through
cathode heated by periodic current of a, prede
that
the. trensiormer
frequency of 8,thethe
control
voltage.
electrode
?uctuations
3 relative 40 termined frequency, an inductive winding con
nected between said controlv electrode and said
tQtIClQ. cathode 4.- approximate a maximum. The
cathode,.means for impressing on said‘ winding
impedance of. theseeondary winding e to currents
aperiodic voltage which has a frequency lower
of the frequency of the. supply source. 5. is, how.
than said predetermined’ frequency, an output
ever, much larger than the'e?ectiveimpedance 4 in circuit connecting said- anode to said; cathode,’
of; the capacitor [5, so that thesecondarv wind
and a capacitor connected between said- control’
anode.
inn?iatts, in. effect, to. choke the flow. of heating,
fresipency. currents. thrqueh the capacitor lined
the.
"acts, like. a IQWrimDBQ?IICB shunt. by-.
'
‘
electrode and said anode‘;
-
:
4. In- combination with an‘ electron tu-be'having‘
an. anode, at least one control electrode and a
' Resting .vqltaeespf. that frequency from. the path 50 cathode heated, by periodic current of a prede
between theeoptrplelettrqde 3 end/the cathodet.
termined: frequency, an- inductive winding con
It is; ed dent, under. Such circumstances, that nected
between. said. control. electrode and-said
the. eepeclter '5 and; inductance, of: winding, 9;,
cathode, means for impressing on said winding,
will; atteeaa even mere e?ettire lent-pass ?lter
ferany frequepeieelereer thenthpseqttheheet- .
me some. 5, 814th, for. example, as... the seed
e'ifécts of. the cathode‘ heating current and‘ to.
harmonic thereof, which may be due to magnetic
voltage drop." along the cathode 4,v between its‘
terminals? Théeeherelr statement may;
feet.)
be". madethat‘th‘ewindIngQQand the capacitor l5
wiutenu. tjoi’choke out. from the‘ output‘ circuit of '
.
,
centre;termite
tube , I, such, for example, 'asjthose due to. random;
?uctuations " in“ electron emission? from" the
emcee; 4.,
a periodic voltage which has‘ a frequency lower '
than. said predetermined frequency, an output
circuit connecting said anode. todsaid cathode,
and: a. capacitor. connected between said‘ control
electrode. and: said anode, the inductance. of said:
winding being of. such; magnitude. that it. will.
resonate at; saidlower frequency with.“ timesthe ,
capacitance of;- said capacitor, where. ,c .is. the‘
voltage. amplification. of, saidv tube.
65..
JOHN-‘Rt BdSYKIN:
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