The
Nuvistor Triode
In
Video
IF-Amplifier Circuits
by
K.
W.
ANGEL
and
J.
GOTE
Reprinted from
Broadcast & Television Receiven
Publication No. ST-2013
IRE
Transactions
July, 1961
RADIO CORPORATION
Electron Tube Division
Harrison
On
OF
AMERICA
New Jersey
Printed in
U.S.A.
•
THE
The
6C14
that
the
systems.
specified
cheaper
On
upacitance,
at
therefore.
neutraliution
uniform
greatly
NEUTRAL IZATlOIl
neutraliution
conditiona
development
Nuvistor
the
Nuviator
and
the
other
high
If
triodea
triode
high-figure-ol-merit
could
The
basic
performance;
more
hand,
triodes
gains
require
characteristics
aimplify
and component
NUVISTOR TRIODE
ABSTRACT
This
paper
discusses
atage
Theoretical
practical
techniques.
are
must
if
amplifiers
designs
of
television
ha.
auggested
.1ao
be used
question
reliable
thsn
neutralization
because
ne
more
tetrodes
more
to
be uaed
be
simple,
variation,
than
stable-gain
characteristics
to
is
triodea
tetrodes
of
high
difficult
snd
careful
However,
of
the
in
stable
are
one
Nuvistor
problema.
an
K•••
Radio
Electron
the
and
places
limits
presented.
tuners
using
the
possibility
advantage
of
cost
are
inherently
and
pentodes.
grid-ta-plate
to
nabilize
pentodes
and
expensive
the
relatively
if
amplifier,
with
snd
inexpensive.
IN
VIDEO IF-AMPLIFIER CIRCUITS
Angel
Corporation
Tube
Harriaon,
use
of
particular
are
the
of
in
if
for
a
snd,
triode
changing
by
and
J.
Gote
of A..
rlca
DI.llion
N.
J.
the
Nuvistor
also
the
it
neceasary
of
both
reaiatance.
therefore, a more
(known
best
csuse
circuit
ficient
spproaches
balance.
practicsl
and
of
an
and
arrangement, which
zation
triode
emphasis
discussed
resiative
the
The
tapped-coil
as
the
baaic
of
ita
sa
of
However,
more
complete
RC
network
An
equivalent
uses
fewer components
of
the
in
two-
on
neutralization.
and
the
component
to
compensate
plate
reaistance
The
grid
satisfactory
Rice System
neutralization
simplicity
the
point
msgnetic
unity,
systems
the
the
is
balsncingmay
in
parallel
system
usea
grid
circuit,
and
three
results
of
the
bridge
for
the
aide
arrangement
of
coupling
uaually
and
is
leas
operating
of
neutralization)
method
and
ita
application.
bridge
coefficient
tapped-capacitor
that
is
removes
approaches
less
require
with
is
shown
of
branches
loading
the
plate
reaiative
shown
for
use
between
of
than
L2.
easier
in
the
effects
dropping
point.
in
triodes
of
the
As
the
Ll and
perfect
coupling
one-half,
the
addition
to
Fig.2.
neutraliinductive
make.
and,
Fig.l
is
the
be-
grid
coef-
L2
apply
Thia
in
•
Fig.1-
aent
(Rice
A
neutralization,
Conaiderable
tion
tion
cinl
output
So-ic
for
.,_tea
number
of
of
a good workable and
ayatell.
All
neutrali~ation
of • bridle
of
the
tapped-coil
triode
of
circuit.
attention
tube
.a
GrrQnge~
could
all
have
ha.
been
inexpenaive
circuit.
either
one
branch.
neotrali%Gtion
neotrali%otion).
but
havinl
be
uaed
aome
given
involve
the
to
drawbscks.
to
the
neutraliza-
the
input
With
tiiode.,
effect
selec-
balan-
or
the
p p
(A)
elements
of
tion
circuit
Usinl a aimilal
plate
introducea
aystem
the
band
and
facilitatea
eau_ea an
circuit
undeairable.
from
the
pssa
eliminates
bridle-balance
r--------~----,------,
I
,
I
::;::
C
QIl
,
I
I
C
•
N
bridle
haa
little
ali,nment.
unavoidable
tapped-coil
n
(B)
branchea
effect
Unfortunately,
3-db
srrangement
the 10••
problema
K
ao
on
gain
in
that
that
r--
I
lL
-'-
C-;;r
I
I
~--
tuning
neutraiiza-
reduction.
il.
gain,
make
p
this
the
bu~
the
STABILITY
In
over-neutralization
necessarily
condition
practice,
exist
reflects
p
•
I.<
(A) (B)
'ill.2 -Tapped-capacitor
grid
tank
and
is
sufficiently
tapped-capacitor
inetability
no
system
in
can
or
any
a
negative
have
under-neutralization
practical
,
I
I
c
,
::t:::
"
,
,
,
+'~RI
L,
C,
of Q grid
high. A stability
circuit
neutrali.zation
circuit.
results
ahown
perfect
.yatem.
resiatance
p
R,
R
c,
if
the
analysis
in
Fig.2
balance;
into
<:!L
.,.
stage
defines
must
Either
the
r--
,
,
,
,
,
L
__
gain
of
the
the
admittance
equation
The
dicatea
using
of
analyais
at a transconductance
only
decrease
ponents.
in- any
..
to
a
tolerance
in
tion.
capacitsnce
zing
cent.
the
duction
per
well-balanced
the
from
ther
not
application
aystem
various
parsmeter
bridge
bridge
reducing
When
single
parameters
For
ca~acitor,
The same
grid
which makes
cent
tank
one
reduced
necessary
determinant,
of a aingle-loop
of
stability,
ahows
imbalsnce
in
one
An
imbalance
the
this
stage
of
±5
a ±
and s ±
tsnk
of
12,000
is
nl>t
branch),
values
to
of
changea
that
the
of
the
impedance
gain
margin
information
in
which
per
cent,
can be
compensated
S-per-cent
S-per-cent
the
gain
variation
requires
the
micromhos,
circuit.
balanced
the
3600 micromhos.
to
consider
6,
the
feedback
Routh-Hurwitz
snd
x, y, and z show
on
of
is
grid-circuit
of
is
the
another
transconductance
aeveral
the
gain
syatem
usable
If
is
12,000
a 20
per
about
20
approximately
by
that
is
used
components
the
anticipated
variation
must
(that
for
variation
be
in
both
20·per-cent
transconductance
or
7200 micromhos
the
resistive
ia,
the
change
marginally
micromhos
cent
in
reduced
capacitors
removed
In
characteri~tic
amplifier.
criterion
applications
the
margin.
resistive
per
percentage.
the
by
in
grid-to-plate
practice,
effect
This
atable
if
increase
cent
equivalent
have a value
gain
in
element
must be
in
the
com-
or
lesa
design
variation
reduc-
neutrali-
by 20
across
gain
for
entirely
fur-
it
the
input
in-
or
of
per
re-
60
of
is
s
•
Fitc.3 -Tapped-capQc:itor
ization
stability
triode.
pedance
priate
transform
factors
X,
y,
and z are
balanced
and
z,
can
tolerate
circuit
Nuui.tor
requirements
Thi.
value.
acale
factare
variable,
of
the
snd
at
the
degree
may
circuit
typical
sasociated
having
i.pedonce
apecifically
i.
of
are
and
unity,
maximum
of
imbalance
be
determined.
neutral-
typical
value,.
redrawn
the
applied.
.,
y, and z
admittance
the
bridge
gain).
for
in
Fi,.3
Nuviator
S
is
are
is
8y
varying
whick
Fig.3
the
Nuvistor
with
when
the
Laplace-
vsriation
(that
perfectly
the
alao
appro-
is,
x,
circuit
akows
im-
if
y,
p
',.,.---~I-----:,...,=------iIf------"7tN
resistance
reduction
tain
For a television
control
minimized
data
unbypaaaed
mizesloading
of s gain-controlled
in
stability.
shown
transconductance
(agc),
by
uain,
in
Fig.
reaiator
variations
the
receiver
variation
the
4.
Theae
of
having
in
short-circuit
curves
eppro.imately
in
tke
,
stale
is
if
agc-controlled
because
sufficient
automatic
reaponae
input-loading
indicate
47
on..
to
gain
can
tkst
mini-
atage.
the
re-
•
,
be
an
•
EXPERIMENTAL
Because
coupled
experimental
whether
large
enough
use
of
the
140
120
47
-~,
TWD-
stability
Rice
Neutrali~ation
circuits
practical
to
more
expensive
........-:
7':
,/
~.y
./
~
-~
~'
>'
o
.~~
ZOOO
4000
6000
TRANSCONOUCTANCE-,....HOS
'0
AND
THREE-STAGE
analysis
were
coefficients
provide
usable
tapped-capacitor
/
"/
~
,
1000
Fig.4
circuit
built
ij
/
10000
12000
-
Short-circuit
AMPLIFIERS
of
the
mutually
is
difficult,
to
of
gains
determine
coupling
without
circuit.
~
~
?'j
-
14000 16000 IIODD
were
the
input·loadinf{
width.
the
capacitance
similar
identical
detector
first
The
An
three-stage
to
•
~
•
•
•
I
7
.........-:
•
I
i
•
4
o
2000
data
for
unbypassed
stage
to
with
agc
the
two-stage
gain-controlled
load.
....
_A
This
~
of!J:,°
4000
6000
TRAfIiIISCONOUCTMCE-lMClS
Nuvistor
4.7-ohm
minimi~e
control.
amplifier
counterpart
stages
amplifier
J.
f6,
....
,~
.,
1000
triodr:.
resistor
variations
shown
and a 3900-ohm
also
\~
....
18
27
1000O 12000
was
in
and
used
in
Fig.6
has
uses
14000
in
input
is
two
the
NIOOO
r
r
,I
•
The
resulting
is a conventional
fier
using a conventional
of
gain
db
normal
causing
control
first
Nuvistor
The
4700-ohm
is
obtained
input
necessary.
tion
not
severe
coupling.
of
the
was
range
of Nuvis
excessive
provides
stage
uses
triode
100
7 lOOK
_ _ 1
I
IT
--
Fig.S
strip
detector
by
loading
resulting
Bandwidth
because
The
response
two-stage
synchronously
obtained
tors
tilt
more
the
and
the
bE
AB
100 "
'l7oolL·-
~A
t~o-stagr:
has
a
3.5-megacycle
load.
loading
of
the
tube,
from
increased
of
result
with
only a slight
amplifier.
or
than
developmental
output
1000
of
narrowing
the
was s
double-tuned
6EAB
mixer.
with
good
can
be
substituted
oscillations.
40 db
stage
10K
,'000
I
~
125
5,nchronousl,
Because
the
plate
no
addi
with
plate
accompanying
small
shown
Mo-re
stability.
of
control.
remote-cutoff
uses
I
\
V.
bandwidth
proper
resistance
tional
agc
gain
resistance
increase
drop
in
decrease
in
Fig.5.
ampli-
than
56
A
without
The
agc
The
the
6CW4..
AGe
loading
the
0.5-3~~'
doublr:-~unr:d
and a
bandwidth
center
in
and
is
reduc-
is
in
band-
conventional
care
is
the
two-stage
and
capacitive
bridges, a stable
The
agc
may
be
shown
per
stage
1000
a.plifi.r:r
the
output
resultant
81.14
di
vision
stable
amplifier
The
tapping
6EA8
necessary
amplifier.
line
provides
obtained
in
Fig.7.
fer
the
3_3hK'---0-.5-;_;li3~~...J~
usinf{ a convr:ntional
stage
three-stage
db. a 3-db
of
the
gain
for
of
72
design
ratio
of
mixer
shown
with
layout
gain
stable
However,
of
80 db
the
two
balancing
using
A
first
I
f
can
be
gain
loss
tank
the
db.
shown
approximately
per
capaci
Nuvistor
in
Fig.7
in
Fig.
and
of
the
only
68 db
of
control.
more
complete
voltage
stages
1Ift00
6EA8
obtained.
should
stage
tors
resul
triode
uses
1:1
S.
Much
wiring
without
neutrali~ing
gain
and
from
ts
three-stage
the
because
greater
thsn
resistive
is
possible.
More
balancing
of
30.5
12.3
aixr:r.
Although
be
11,400
the
voltage
in a maxi'mum
capacitor-
this
db
with
gain
db
for
the
or
if
con-
dit.ion
addition,
equivalent
unity
improvement
ratio
Unfortunately.
input
The
mately
I:
beyond a
1:1
coefficient
that
and
optimum
1
case.
case.
minImizes
produces a slightly
output
l:1.5
ratio
the
ideal
in
tap
provides
Greater
4700
input
stage
Rice
of
gain
can
the
improvement
capacitances
ratio
of
1:3
',:+:
and
output
gain
neutralized
magnetic
be
for
this
0.4-db
ratIOS
the
gain
capacitances.
is 3 db
coupling.
effected
higher
is
small
are
circuit
improvement
result
is
less
system
by
grid
also
in
less
having
A
slight.
voltage.
approxi-
over
gain;
in
In
the
the
the
the
than
using a tap
because
increased.
of
less
than
has
been
set
aligned,
at
± 5
be
CONCLUSION
Two-
and
if
amplifiers
is
used
no
additional
possible a gain
load
for
ohm
load
of
tubes
three-stage
with
the
for
the
within
the
per
cent
are
feasible
simple
bridge
two~stage
Rice
balancing.
of
56 db
three-stage
the
Nuvistor
neutralizing
values.
synchronously
when
the
neutralization
with a 4700-ohm
strip
This
and
strip.
specification
'000
1
capacitors
double-tuned
Nuvistor
system
68
db
Substi
can
triode
and
with
makes
detector
with a 3900-
tution
limits
I
r
ALIGNMENT
In
set
of
minimum
ted
in
the
for
minimulII
the
gain-controlled
feedthrough,
for
minimum
the
normal
alignment
gain.
tilt.
.ay:
procedure,
The
and
Band-pass
the
gain
'--------;::::=----'------------'-
Fig.6
-
gain-controlled
the
neutraliting
stages
the
is
(No.
4100
are
output
increased
TURNS
34
9;16
10K
1
Three-Hoge
gain
control
capacitors
adjusted
stage
adjustment
WIRE)
AGe
is
by a
l:
stages
adjus-
is
small
27
10
GlllplifLer
and a 3900.ohlll
does
practical
is
three-stage
for
made
tolerance
imbalance
lization
and
0.5-3
47
4700
having
not
stray
two
identical
dett!:c!or
cause
oscillator
maximum
ampli
components
in
the
bridge
capacitances
9:16
!
IC
4700
125
v.
125
load.
are
1000
or
possible
is
72
used
component
are
assumed.
gain
fier
resistive
and ± 15-per-cent
:r
v.
excessive
from
db
when ±
and a 20-per-cent
spread
tilt.
the
5·per-cent-
of
the
in
•
The
Nuvlstor
neutra-
Nuvistor
•
amount
tralited
tne
This
can
from maximum
and
and
output·stage
process
be
applied
the
gain-controlled
then
neutralitation
is
continued
without
to
minimum
fig.?-
cut
Nt!:utralizatton
off
to
permit
until
causing
gain.
circuit
stages
tilt
When ~ given
for
full
or
are
adjustment
minimum
agc
oscillation
re-neu-
tilt.
control
layout
using a 1:1
BI
of
BLI
Bode,
D.
F,
Amalgamated
capadtor-tapptng
OGRAPNY
NETWlIIK
Van
Nostrand
ANALYSIS
Co.,
Langford-5.ith,
Wireless
ratlo.
AND
FEEOOACK
New
York,
RADIOTRON
Valve
DESIGNER'S
CO.
AMPLIFIER
1945.
Pty.
Ltd.,
DESIGN,
HANDROOK,
1953.
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