„Euäy ì, i946.
o. H. SCHADE
2,404,099
AMPLIFYING SYSTEM
Filed Aug. 16, v1941
2 Sheets-Sheet 1 '
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July 16, 1946.
O. H. SCHADE
2,404,099
AMPLIFYING SYSTEM
Filed Aug. 16, 1941-
2 ShfeetsFShee'f,v 2
Patented July 16», A1946
i
„
2,404,099
UNITED STATES >PA'I‘ENTÍ OFFICE
2,404,099'
_
4
AMPLIFYmG SYSTEM Y
Otto H. Schade, West Caldwell, N..I., assigner to
Radio Corporation of America, a corporation of .
Delaware
Application August 16, 1941, Serial No.4077,1370 »
l
7 claims.
My invention relates to high efficiency ampli
(o1. 315-28)
l `
2
power limiting devices to limit the power outputy
fying circuits for uni-directional signals and par
from at least one of the said tubes to a prede
ticularly to amplifiers for amplifying recurrent
termined maximum value. These and other ob
phenomena for portrayal in cathode ray oscillo
jects, features and advantages of my invention
scope equipment.
UY will become apparent when taken in connection
In many applications for the ampliñcation of
with the following description and with the' ac
recurrent phenomena, it is desirable .tol provide a
companying drawings wherein: ’
,
linear amplified output characteristic with mini
Figure 1 is a schematic circuit showing the
mum of equipment and power dissipation. In
portable aircraft position indicators it is neces 10 -prin’cipalieatures of my new „and improved
amplifying system for use in cathode ra'y deñec
sary to provide circuits having a high degree of
tion oscillographs;
‘
.
frequency response as well as high precision so
that the absolute distance between approaching
Figure 2 is a dynamic characteristic curve show
ing operation wave forms of a conventional am
aircraft or from an aircraft to ground station may
plifying system;
be portrayed on a luminescent screen of a cathode 15
Figure 3 is a similar dynamic characteristicV
ray tube with accurate precision. It is also desir
able, especially when such equipment is to be
located on the aircraft, to provide a minimum of
showing my improved method of operation, andA
Figure 4 is a graphical diagram of certain static
anode characteristics of my amplifying system.
weight and power dissipation. While certain of
It will be appreciated that in circuits for- ob
the objects of my invention may be obtained by 20
taining high output voltages of square and asym
other methods and means, such is true only by
metric wave forms, it is necessary to provide very
the use of larger and higher power dissipating
equipment. Thus in circuits for obtaining high
output voltages of square wave form severe limi
high frequency band widths up to and including
a band Width such as 10 megacycles per'second.
Whilel large amplifying output tubes may be ’
tations are incurred by the fact that the ampli 25
utilized `with relatively low -load resistors to
fier tube dissipation becomes excessive. It was
obtain such wide band widths, such-tubes and
therefore found necessary in the past to use rela
circuits are usually characterized by high power
tively large tubes when the required output volt- dissipation and relatively high tube and circuit
age exceeds a certain value by providing tubes
of increased size and larger power dissipating 30 capacitance. The plate dissipation in such tubes
is proportional to the second power ofthe capaci
capability. Such use also increases the amplifier
tance so that for a -given frequency band, tubes
circuit capacitance which in turn necessitates in
having kvery large continuous power dissipation
creased power dissipation.
are necessary even though the useful integrated
It is therefore an object of my invention to . power
output is relatively small. In vso-called
increase the obtainable linear voltage output over
“class
B”
operation the continuous power con»
a relatively high frequency band with low power
sumption may be reduced but only at the sacri
dissipation. It is another object of my invention
lice of nonlinearity. Therefore, in accordance
to provide a system wherein high linear output
with my invention I provide a counterphase
voltage wave forms may be obtained and wherein
amplifying circuit having at least two amplifying
a minimum of power dissipation is required. It is
tubes, each Vhaving at least a cathode, control
a still further object to provide a System wherein
grid, and anode or plate electrode, and I adjust
uni-directional signals may be ampliñed efli
the` grid and anode potentials so that a greater
ciently by the use of conventional low power dissi
negativegrid bias may be applied to the tube
pation tubes, and it is a still further object to
with the higher anode potential, and a lower nega
provide a system of high frequency band width
tive grid bias may vbe applied'to the tube having
wherein the power dissipation may be maintained
the lower anode potential. , In operation the
at low values while retaining the advantages of
first tube operates near cut-off current at zero
low output loads which are required for high fre
signal and hence operates with low orzero plate
quency response.
dissipation.
'I’he second tube operates with a
In accordance with my invention I provide an
low negative grid bias and a moderately high
amplifying system utilizing at least two ther
plate current at low plate voltage and hence also
mionic amplifying tubes and control the operation
operates with moderate plate dissipation.Y Eur-_
of the tubes so that the parameters determining
ther in accordance with my invention I_ utilize
the power dissipation are divided unequally be
tween the tubes in combination with additional
voltage measuring control tubes which auto
matically vary the »grid
bias on each ofthe-_
2,404,099
3
counterphase amplifier tubes to limit the maxi
mum plate dissipation of one tube and maintain
a linear summation characteristic. Obviously, my
to maintain the two tubes at different bias values
comprising a manually adjustable potential
divider 20 connected between ground and cathode
l2 and I5 and a source of negative potential.
system is applicable only to the amplification of
The grid I3 of the tube I6 is connected through a
uni-directional wave forms such as square waves,
grid resistor 2| of approximately 250 K. ohms
either of the symmetrical or asymmetrical type,
with low average components such as impulses of
short duration with respect to their repetition
to a point on the potential divider 20 which is
highly negative with respect to the cathode I2,
whereas the grid I5 of the tube II is connected
through a similar resistor 22 to a point on the
time.
The principles embodied in my system will be 10 potential divider 2B which is at a less negative
understood to better advantage by referring to
potential. In this manner the grid bias on the
Figure 1 which shows in schematic form one Inod
tube I0 is maintained at a greater negative value
iflcation of an amplifying circuit employing my
than that of the >grid of the tube l I. Further in
invention and particularly adapted for the am-V
accordance with my invention each of the grid
plification of square wave forms which may be
resistors ZI and 22 are shunted by a peak volt
applied to cathode ray indicating equipment. Re
age reotifying device, such as the diodes 23 and
ferring to Figure 1, the tube I, which may be of
2d. These diodes rectify the peak voltage shown
the single or multiple grid thermionic type, serves
as ein and en on the wave forms I8 and I9 and
modify the grid biases by an equivalent D. C.
as a phase inverter for a square wave form-shown >
at 2 for which ampliiication is desired. The wave
voltage appearing across the resistors 2 l-22. To
form is applied across the grid-cathode input cir
obtain this mode of operation I connect the diode
cuit and appears in unmodified form except for
23 with its cathode to the grid I3 and the plate
phase inversion across the plate cathode circuit.
to the potential divider 2€), and conversely the
Thus a wave form similar to that shown at 2 is
diode 24 is connected with its plate to the grid
developed across the capacitor 3 and a similar
I6 and the cathode to the potential divider 2€).
wave form except for phase inversion across the
In operation any signal I3 applied to the input
capacitor 4. The relative amplitude of these wave
circuit of the tube II! will cause a decrease of the
forms may be varied by a variable resistor 5 con
negative bias applied to this tube, and conversely
nected as shown. In order to preserve the high
any signal I9 will cause an increase in the nega
frequency components comprising the square wave 30 tive bias applied to the tube II. Further details
form shown at 2, the resistors in the input and
of the operation of the voltage measuring devices
output circuits of the tube I are of relatively low
22 and 23 will be more fully described below. The
value. The output from the capacitor 3 may be
anodes of the tubes I0 and II are likewise, in
further amplified by use of a conventional am
accordance with my invention, supplied with def
plifying tube 6, and similarly the output from 35 inite potentials, that of the tube I0 being con
the capacitor 4 may likewise be ampliñed in con
siderably higher than that applied to the tube I I.
ventional manner by an amplifier tube l. Each
The tubes I0 and I I may be of the 6L6 type with
of these tubes may likewise be of the single or
an isolated anode lead, such as the commercially
multiple grid types. rEhe outputs from each of
available tube Type 807, in which case a poten
the tubes (i and 'I are applied through conven 40 tial of 1500 volts may be applied to the plate I4
tional coupling networks to output capacitors 8
through a load resistor 25 of relatively low value
and 9. Likewise, following current high fre
to maintain proper frequency response in series
quency circuit principles in the design of the load
with a load impedance 26; similarly, a potential
circuit, tubes S and 'I are preferably of the low
of 500 volts may be applied to the anode I'I
power consumption beam type, such as the tube
through a similar load resistor 2'I and load imped
known commercially as Type GLS operating at a
ance 23. The ampliñed outputs of the tubes iii
plate potential supply of approximately 250 volts
as shown. In accordance with my invention the
and II are preferably capacitively coupled
through capacitors 29 aid 39 through suitable
signals to be further amplified and appearing at
nonattenuating circuits and. to one set of deflec
the capacitors ß and 9 which are preferably of 50 tion plates ill-_32 of a conventional high voltage
0.1 microfarad value are applied to the input cir
cathode ray tube 33. These amplified square wave
cuit oi‘ two tubes IIJ and II operating in counter
potentials contain substantially all of the high
phase arrangement. In accordance with my
frequency harmonics originally contained in the
principles of operation I apply a relatively high
signal shown at 2 and appear across the respec
55
negative bias to tube I0 and a relatively low neg
tive plates 3I-32 as shown at Sli-_35. A con
ative bias to the tube II, and likewise apply a
ventional sawtooth voltage wave form may be ap
relatively high plate potential to the tube ID and
relatively low plate potential to the tube II.
plied to the quadrature deñection plates 36-«31
as well known in the art for the portrayal of the
More particularly, the tube Ii) includes a cat-h
combined wave forms Sil-35 on the conventional
ode I2, a control grid I3 and an anode lf3, while 60 luminescent screen of the tube 33, and the por
the tube I I includes a cathode I5, grid I6 and an
trayal of the square wave form may be centered
anode I'I; each of these tubes likewise may be
on the luminescent screen by applying a positive
of multi-grid as shown, including a screen grid
potential to the plate 3| from the potentiom
I3’ and I6', in which case suitable operating po
38.
tentials may be applied to the additional grid elec 65 eter
The principles underlying the operation of my
trode or electrodes. The signal appearing be
system will be more fully appreciated with ref~
tween the capacitor 8 and ground is applied di
erence to Figures 2 and 3 wherein Figure 2 is rep
rectly to the grid I3 of the tube Iû, the wave
resentative of a balanced bias and anode poten
form being such as shown at I3, and similarly the
tial condition between the tubes Ill and II, and
wave form appearing between the capacitor 9
Figure 3 is representative of an unbalanced con
and ground is applied directly to the grid IE of
dition of bias and anode potentials whereby the
the tube II. The average potentials or bias po
objects of my invention are obtained. Refer
tentials of these grid electrodes, however, are
ring to Figure 2, the dynamic load characteris
maintained at definite values, one of which is
tic of the tube I0 is represented by the line AB
75
higher than the other. I therefore provide means
2,404,099
and that of the tube II by the line A’B'. Since
the characteristics of the two tubes I0 and II are
similar, the summation characteristic is substan
tube II). _'I‘he load line AioBio is drawn with a'
slope corresponding to the resistance of resistor
25 throughrth'e assumed Imax value which is lo
cated'on the knee line 50 of the tube I0. This
knee line is the envelope curve of all plate volt
age-plate current characteristics with control
tially linear and represented by the line BB', a
portion of which is shown in dashed line detail.
The grids of the tubes I0 and I I for the assumed
balanced condition have applied thereto a sig
grid; or screen grid voltage or voltages as pa
nal, such as shown at 40 in Figure 2, the line CC’
rameters. ‘ This ' will determine the necessary
being representative of the average grid signal.
anodepotential Eb'for the tube Iû. To determine
It is here also assumed that the diodes and their 10 theïcorresponding anodev potential for tubeV .II
circuits are not used in the balanced condition.
theîload'lineÍis-lextended so as to be 1/4 as long
For this balanced condition the grid bias on 'each
as ' A101310/- which .determines the point Bn
of the tubes I0 and II would be of the same
through which the perveance characteristic 5I of
amount and the average grid signal represented
theïtube'll is drawn. The values Enf, I’max and
by the line CC’ remains stationary, always pass 15 Ep'f'mina're thus “derivedì
` - ¿
’
'
ing through the point O. Consequently, even in
~
The
dynamic
characteristics
for
.the
tubes
I0
the absence of signals applied to the tubes Ill
and YII -shown vin' Figure 3 are then drawn using
and II, the plate dissipation of both tubes will
these
assumed and derived parameters, adjust
be high because both of the tubes operate with
ingftheirv position to give the linear summationV
a plate current represented by the intersection 20 characteristicl ' 'If the tubes' I0 and II are of the
multi-grid Vtype as shown, the screen potential
at a high anode potential applied to both tubes.
required _for tube II will be found to- have a
Figure 3, which shows the dynamic character
lower Value lthan tube Ill'becaus’e of' the'lower
istic under unbalanced conditions, portrays the
current requirements’. The line EE’ of Figure 3
of line CC" with the characteristic AB and A'B’
operation of the system when operated in ac
cordance with my invention. The line EE’ may
be made to coincide always with one of the peak
values of the grid signals by means of the di
is now drawn through the current value of I’max
intersecting the characteristic AB of tube I0 a't
the zero signal current value.
The zero signal
power dissipation is given for tube- Ill by this zero
odes 'i3-24. The average value of the grid sig
signal current IQ multiplied by the anode voltage
nals DD' is eifectively shifted to the right by the 30 of the tube I0: `
rectiñed peak voltages ein, en adding to the ñxed
grid bias of the two tubes I0 and I I. By increas
ing the bias on one tube by an amount en and
The power dissipation for tube I I is similarly ob- .
at the same time decreasing the bias‘on the other
tube by the amount ein, the linearity of summa 35
tion characteristic is not altered but the grid
voltage axis is shifted to DD' as shown in Figure
If these dissipations do not exceed the tube rating,
the derived values represent one possible operat
3. Thus with the tubes 23 and 24 in operation
the average moves according to the signal leav
ing condition. yIf the dissipation ’of tube VIl) eX
ing EE’ in a predetermined position. A ñxed 40 ceeds the tube rating, the line EE’` must be moved
toward cut-offY until a dissipation conforming to
maximum current cannot, therefore, be exceed
ed in tube II regardless of signal. It is there
the rating is not exceeded. ' The required current
fore obvious from Figure 3 that a square wave
I’max for tube I Iv is thus increased as seen from
Figure 3 and can be determined from Figure 3 as
form, such as the signal shown at 40, will cause a
high current and low plate voltage lon tube II, L the intersection. of line EE' with a linear sum
and a low or Zero current with corresponding
mation characteristic. Consequently, the inter
high plate voltage on tube I0 for the long inter
val between the signal pulses. Both of these
conditions represent low plate dissipation in the
section of the load line AnBn in Figure 4 with
the perveance characteristic 5I must be corrected
respective tubes.
Therefore, for zero signal con- '
ditions the tube I0 has the same low dissipation
as between signal impulses.
The tube I I, when operated with low negative
bias and relatively low anode potential, operates
with a moderate anode current at zero signal, .
and since the signal is uni-directional toward its
cut-off voltage and beyond, the required anode
supply voltage for the tube II is considerably
less than that required for the tube I0. The
necessary anode supply voltage on each tube is 60
given by the expression:
solving for the required higher plate potential Eb'
of tube I I. The zero power dissipation of tube I I
is redetermined' with these new values. If the
resultant dissipation of tube II exceeds the rat
ing, it is not possible to obtain the assumed sig
nal output for the tubes chosen and the process
must beV repeated for a signal output lower than
the desired output referred to above. In this
manner the maximum signal output may be de
termined for the chosen type oftubes Il) and II.
While I havedisclosed my invention with par
ticular reference to the amplification of square
wave forms, it will be obvious that-it is also of
particular advantage in the ampliñcation of any
pulse-type wave forms wherein the average value .
These voltages and currents may be shown
between reoccurrence of the pulses is relatively ï
graphically on the static anode potential-anode 65 long with respect to the pulse time. It will like
current characteristics as in Figure 4. This
wise be obvious that my system possesses consid
static characteristic may be used to determine
erable merit inthe ampliñcation of wave forms
the operating parameters for the tubes I0 and
of the pulse type having a smaller and larger '
II. The load resistors 25 and 21 are chosen in
amplitude of opposite polarities. Therefore,
accordance with the tube characteristics to give 70 while I have described my invention with refer
the desired band width, these resistors being
ence to the amplification of vsignals of particular
identical for similar tubes. The output signal
wavev form and have likewise disclosed only one
of tube Ill may be assumed as 4/5 of the total de
particular modification of which my invention is
sired output signal swing and hence furnishes
susceptible, _it will be obviousthat my invention
the maximum current (Imax) to be supplied by 75 is ' suitable’for 'use' in amplifying other Íwavef
2,404,099
7
immediately occur to those skilled in the art, and
I am therefore not to be limited to the particular
use or modification set forth above except as set
forth in the following claims.
I claim:
appearing between said anodes is applied to said
deñection plates for portrayal of said combined
wave form.
1. A counterphase amplifying system for am
plifying signals of square wave form comprising a
5. A system for portraying a square wave form
on a cathode ray tube comprising a counterphase
pair of thermionic amplifying tubes of the multi
grid type, each having a cathode, grid and anode,
means to apply dilîerent negative biasing poten
amplifying circuit including a pair of amplifying
tubes having a cathode, input grid, screen grid
and anode, a source of bias potential of different
tials with respect to the cathode between the
cathode and grid of said two tubes, means to ap
ply different positive potentials between the an
ode and cathode of each of said tubes, the positive
potential applied to the tube having the most neg
ative biasing potential being higher than that ap
plied to the other tube, means to apply the square
magnitude connected between the cathode and
input grid of each of said tubes, a positive po
tential source of diiîerent magnitude connected
to each of said screen grids, a positive potential
source of different magnitude connected to each
of said anodes through a load resistor to form
an output circuit for each of said tubes, the screen
wave form between the cathode and grid of one
tube and means to simultaneously apply a similar
wave form to be amplified, but of opposite polar
ity thereto, to the other of said tubes, whereby
the ouput wave form from each of said tubes is
an amplified signal component of the said square
wave form.
2. A system for amplifying a square wave volt
8.
other, a cathode ray tube having a pair of op
positely disposed deflection plates and means con
necting each of said deflection plates to one of
said anodes whereby the combined wave form
forms and that other modiications thereof will
grid and anode sources of the tube having the
lower negative bias being of lower magnitude than
those connected to the screen grid and anode of
the tube having the greater negative bias, means
to apply to each of said input grids mutually in
25 verted components of a square wave form, each
age impulse comprising a pair of amplifier tubes
having input and output electrodes, means to
apply the square wave form to be amplified to the
of said components having two different ampli
tudes, to develop signals having different ampli
tudes in the output circuits of said tubes, means
to modify the bias of each of said tubes in pro
input electrode of one of said tubes, means to 30 portion to the smaller amplitude of the signals
applied to each of said tubes, a cathode ray tube
apply an inverted wave form of the wave form
having a pair of oppositely disposed deflection
to be amplified to the other of said tubes, means
plates and means connecting said anodes respec
to maintain the input electrodes of said tubes at
tively to said plates whereby the ampliñed in
a predetermined average potential, means to ap
ply a bias potential more negative than the said 35 verted components of said square wave form are
applied between said deflection plates for por
predetermined potential on the input electrode
trayal of said wave form.
of said one tube to the input electrode of the other
6, A counterphase amplifying system for por
tube, and means to apply a positive potential to
traying a square wave form on a cathode ray tube
each of the output electrodes of said tubes, the
potential applied to said one tube being lower 40 comprising an amplifying circuit including a pair
of similar amplifying tubes, each having a cath
than that applied to the said other tube.
ode, input grid, screen grid and anode, a direct
3. A system for amplifying a square wave form
electrical connection between the cathodes of each
for portrayal on a cathode ray tube comprising
of said tubes, a source of bias potential of differ
a pair of similar amplifying tubes, each having a
cathode, grid and anode, means to apply differ 45 ent magnitude connected between the cathode
and input grid of each of said tubes, a positive
ent grid bias and anode potentials to each of said
potential source of different magnitude connected
tubes, means to adjust the bias on each of said
to each of said screen grids, a positive potential
tubes such that the tube having the higher anode
source of different magnitude connected to each
potential has applied thereto the more negative
bias potential to displace the operating point on ç of said anodes through a load impedance to form
an output circuit, the screen grid and anode
the dynamic summation characteristics of said
sources of the tube having the lower negative
tubes in opposite directions, means to apply the
bias being of lower magnitude than those con
square wave form to be amplified between the
nected to the screen grid and anode of the tube
cathode and grid of each tube in inverted form,
one with respect to the other, a cathode ray tube
having a pair of oppositely disposed deflection
plates and means capacitively connecting each
of said deflection plates to one of said anodes
whereby the combined wave form appearing be
tween said anodes is applied to said deñection
plates for portrayal of said combined Wave form.
4. A counterphase amplifying system for am
plifying pulse wave forms for portrayal on a cath
ode ray tube comprising a pair of amplifying
tubes, each having a cathode, grid and anode,
means to maintain the anodes of each ofv said
tubes at different positive potentials with respect
to the respective cathodes, means to displace the
operating point on the dynamic summation char
acteristic towards cut-off on the tube with the
higher anode potential and towards higher anode
current on the tube with the lower anode poten
tial, means to apply the pulse wave form to be
having the greater negative bias, means to apply
to each of said input grids a mutually inverted
component of a square wave having a smaller and
larger amplitude of opposite polaritiës, a diode
having a cathode and grid connected between
each of said input grids and the cathode of said
tubes in series with the said sources of bias po
tential of different magnitude to modify the bias
of each of said tubes in accordance with the
smaller amplitude of the square wave form ap
plied to each of said tubes, a cathode ray tube
having a pair of oppositely disposed deflection
plates and means connecting said anodes respec
tively to said plates whereby the ampliñed in
verted components of said square wave form are
applied between said deflection plates for por
trayal of said wave form.
7. A system for portraying a square wave form
on a cathode ray tube comprising a counterphase
amplifying circuit including a pair of lamplifying
amplified between the cathode and grid of each
tubes,
each having a cathode, input grid, screen
75
tube in inverted form, one with respect to the
,
Y
9
2,404,099
10
,
grid and anode, a source of bias potential of dif
wave form, means to modify the bias of each of
ferent magnitude connected between the cathode
said tubes in accordance with the smaller ampli
and input grid of each of said tubes, a positive
tude of the square wave forms applied to said tubes
potential source of different magnitude connected
comprising a diode connected with its anode to
to each of said screen grids, a positive potential 5 the source of higher grid bias and its cathode to
source of dilîerent magnitude connected to each
the input grid cf the tube with higher anode po
of said anodes. the screen grid and anode sources
tential and a second diode inversely connected
of the tube having the lower negative bias being
with respect to the lower bias source and the in
of lower magnitude than those connected to the
put grid of the tube with lower anode potential,
screen grid and anode of the tube having the 10 a cathode ray tube having a pair of oppositelydis
greater negative bias, means to apply to the input
posed deñection plates and means connecting said
grid of the tube having the lower anode and screen
anodes respectively to said plates whereby the
grid potentials an input square wave form to be
amplified inverted components of said square
portrayed with such polarity that the higher am
wave form are applied between said deflection
plitude of said square wave decreases the current
of said tube, means to apply to the other of said
tubes a counterphase component of said input
plates for portrayal of said wave form.
`
O'I'I'O H. SCHADE.