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Патент USA US2514025

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Patented July 4, 1950
Carl A. Bergfors, Yonkers, N. Y., assignor to‘In
ternational Business Machines Corporation,
New York, N. Y., a corporation of New York
Application October 10, 19517,,Serial?No. 779,031
1 Claim.
(Cl. 178-44)
This invention relates to asquare wavegenera
tor. and has particular relation to a generator em
ploying ,an oscillator and an ampli?er.
In prior arrangements, a. vwell shaped square
wave is customarily generated by apparatus com 5
prising a multivibrator oscillator and electronic
limiter. or clipper ampli?er circuits coupled there
tween “a change in the output voltage of the
oscillator and the corresponding change in grid
voltage of the ampli?er tube which delay pre
cludes a, substantially vertical wave front out
put for the ampli?er.
Accordingly, it is also an object of the inven
tion to provide an improved square wave genera
tor having a wide frequency band coupling be
tween an oscillator and an ampli?er and between
are substantially vertical while the tops and bot 10 successive stages of an ampli?er which coupling
toms ,of the wave Varesubstantially horizontal.
incorporates the advantages of, a direct resistive
While such prior apparatus may be satisfac
coupling at low frequencies and of a capacitive
to. Eye wellshapedsquare .wave is meant one
in which ,theleading and trailing wave fronts
coupling at high frequencies.
torily operated over arange of frequencies, the
frequency band within which a well shaped
Other objects of the invention will be pointed
square wave may be obtained is not as wide 15 out inthe following description‘ and claims and
illustrated in, the accompanying drawing, which
discloses, by way of example, the principle .91.’
as is, many times desirable.
, Theprincipalobjectlof the invention is to pro
vide a new and improved square wave generator
the invention and the best mode, which has been
contemplated; of applying that .principle.
operable over an extremely wide band of fre
In the drawing:
Another object is to provide a novel square
wave generator which is operable over a fre
The single ?gure is a schematic wiring diagram
of,a square wave generator embodying my inven
quency band of'the order of 1 to 800,000. cycles per
.As shownin the drawing, theisquare wave gem
7A further object is to provide. an improved 25 erator‘ is made up of a power supply unit lllha.
square wave generator comprising a multivibrator
oscillator with. clip-per ampli?er circuits coupled ~
thereto which is operable over an extremely wide
multivibrator oscillator. ll. and a three stage
clipper ampli?er I2. Conventional cathode
heater. circuits for, tubes in. the. various units al‘e
frequency. band and providesa well shaped square
omittedfromv the drawing forv clarity.
The power supplyunit is energized from an
alternating current sourcethrough, a transformer
I3. A recti?er tube .Vl ,has its two anodescon
nectedv to,_.opposite ends of .a secondary winding
waveat any frequency in the band.
My invention arises from therealization that
inv prior apparatus, as described above,.the width
of they frequency band is. limited largely by the
nature of the coupling between the multivibrator
Mnofwthe transformerl3. The cathode oftrectie
and ampli?er and between successive stages of the 35 ?er NT! is connected to .arcent?r tap [5 on. the
ampli?er. Usually, a coupling capacitor is em
secondary winding l4 througha choke coil~I6
ployed. However, for, low frequencies the capaci
in serieslwith .a. capacitor 01 whereby a D. C.
tor must have a verylarge capacity and, con
voltage of therpolarityindicated in the drawing
sequently must eithervbe extremely large or be
is providedtacrosscapacitor Cl. Another capaci
of the electrolytic type, the leakage resistance 40 tor~C2.y-and~a semievariable resistor R! - are con
andv instability of whichmakes, itundesiliable as
nected in series across thecapacitor CI’ to provide
a coupling capacitor at such points in the gen
all C. voltage on the capaictOr'CZ which,‘in
erator. Thus, the use of a coupling capacitor for
the particular circuit shown, maybe of the'order
very low frequencies is believed to be impractical.
of- LEG-volts.
On the other hand, a direct resistive coupling
A half ‘wave recti?er V2; shown as a double
is satisfactory for lowfrequencies but is not sat
diode, is-connected in series with two "resistors
isfactory for either the high frequencies within
R2~and¢R3~from thev center tap l5 to one end
the band of oscillations of the square wave gen
erator or the high frequencies represented by the
of'the secondary winding ‘ M. A capacitor C3eis
in parallel with the resistor R2 so that a DC.
steep wave front of each individual pulse of the 60 voltageofiapproximately lOilvolts appears there
square wave. At high frequencies the input
capacitance of‘the ampli?er tube becomes of con
A voltage regulator tube V3 is connected in
siderable importance with a direct resistive cou
series with a resistor R4 across the capacitor 02
pling. This input capacitance in such an ar
so that-a regulated voltage of ‘approximately 150
rangement causes an exponential time delay be
volts appears across the recti?er tube V3. Four
D. C. voltage supply lines, I‘I, I8, I9 and 20 are
then provided from the power unit I II, as illus
trated in the drawing. The ?rst line I‘! is con
nected to the positive terminal of capacitor C2‘
and is grounded. The second line I8 is connected
to the anode of the rectifier tube V3 and is approx
imately 10 volts negative relative to line ll. The
third line I9 is connected to the cathode of the
recti?er V3 and therefore to the positive termi
nal of capacitor C3 and is approximately 150 "10
volts negative relative to line I8. The fourth line
20 is connected to the negative terminal of the
capacitor C3 and is approximately 100 volts nega- >
tive relative to line I9. Of course, any suitable‘
D. C. voltage supply source may be employed al 15
though a regulated voltage supply for the oscil- >
lator is desirable and I have found the speci?c
of the tubes V4 or V5, because of transients or
the absence of exact uniformity in the two tubes
or their circuits, will conduct more current than
the other. As a result a negative signal is passed
from the anode of that one tube, because of the
increased voltage drop across the corresponding
load resistor R5 or R6, through the associated
capacitor C5 or Clia to the grid of the other tube.
The current through that other tube is thus re
duced, which results in the grid of the aforesaid
one tube becoming more positive to increase the
current therethrough still further. It is appar
ent the effect is a cumulative one and the cur
rent through the one tube rapidly reaches a max
imum while the current through the other tube
is out off. This circuit condition remains until
the charge on the capacitor C6 or 05a connected
to the grid of the other tube leaks o? to permit
supply unit described to be highly satisfactory.
current to again ?ow through the other tube.
The multivibrator oscillator II is of the well
known positive bias type. It is supplied with the 20 When this occurs the cumulative eifect again
takes place but in the reverse direction. Thus,
regulated voltage appearing between supply lines
the current flow shifts between tubes V4 and V5.
I8 and I9. The multivibrator comprises a twin
The output of the multivibrator is taken from
triode, the halves of which are designated as V4
the anode of tube V5. This output approaches
and V5. The anodes of tubes V4 and V5 are con
nected to line I8 through load resistors R5 and 25 a square wave but in itself is a very poorly shaped
wave. The frequency of the output of the multi
R6, respectively. These load resistors R5 and R6
vibrator is, of course, determined by the various
are of a relatively low resistance to minimize the
capacitors and resistors in the circuit. The re
effects of tube and circuit capacitance in the
sistor R9 may be varied to provide a rather coarse
the widefrequency band desired. The common 30 frequency adjustment while adjustment of the
tap on resistor RI3 effects a ?ner control of fre
cathode of tubes V4 and V5 is connected to supply
quency. The major frequency control is, of
line I9. The control grid of tube V4 is connected
course, in the setting of the capacitor banks to
through a resistor R1 and a selected capacitor in
-m_ultivibrator at the higher frequencies within
‘the capacitor bank comprising capacitors C4, C5,
permit operation of the multivibrator at a select
C6, C1, C8 and C9 to the anode of tube V5. The
control grid of tube V5 is connected to the anode
ed frequency over a wide frequency band. Vari
able resistors RII and RI Ia may also be adjust
of tube V4 through the resistor R8 and a selected
ed to control the width of the pulse provided by
the multivibrator.
The ampli?er I2 comprises three stages rep
capacitor of the capacitor bank comprising ca
pacitors 04a, 05a, 06a, 01a, 08a, and 09a. The
, resented by tubes V6, V1 and V8 respectively.
selectors 2|, of the capacitor banks may be oper
Tube V6 isconnected as a pentode with its anode
ated ‘simultaneously to determine Which of the
connected through resistor RN to supply‘line I1
capacitors are connected in their respective cir
and its cathode connected to line I9. The screen
cuits at any selected setting and that correspond
grid 22 of tube V6 is connected to line I‘! through
ing capacitors in the two banks are simultaneous
a resistor RIB whereby a desired voltage is ob
ly so connected.
tained on the screen grid. This screen grid volt
The grids of tubes V4 and V5 are also connect
ed together in a circuit which can be traced from
age is stabilized by a capacitor CI3 connected be
the grid of tube V4 through the resistor R1, the
tween the screen grid and the cathode.
parallel circuit comprising a variable resistor R9
The ampli?er I2 is coupled to the multivibrator
on one side and a resistor RIO, a pair of variable 50 oscillator II by a novel coupling arrangement.
resistors RI I and RI Ia and a resistor RI 2 on the,
Three resistors RI9, R20 and R2I are connected
other, side._ The connection between the grids.
in series between the anode of tube V5 of the
continues through resistor R8 to the grid of tube‘
oscillator and line 20 to form a voltage divider.
V5. A voltage divider comprising a pair of series
An adjustable tap on the resistor R20 is connected
‘connected resistors R I 3 and Rl3a is connected be- '5 to the control grid of tube V6 through a grid re
tween supply lines I8 and I9. The junction be 55 sistor R22. A capacitor CI4 is connected di-.
tween variable resistors RII and Rlla is con
rectly between the anode of tube V5 and the ad
nected through another resistor RI4 to an ad
justable tap on resistor R29.
justable tap on resistor RI3. A capacitor CID is
The tap on resistor R29 is adjusted so that
also connected from the junction between resis- ' " the voltage across the divider formed by resistors
tors RI I and RI Ia to the supply line I9. To en 60 RI9, R20 and R2I, which voltage is derived from
able stabilization of the multivibrator by a syn
chronizing pulse, a terminal SI is provided over
the anode of tube V5 of the multivibrator II,
tends to cause the voltage of the grid of tube V6
which a synchronous input pulse may be sup-‘ 7 .\ to alternate between a ?rst voltage more nega
A capacitor C II and a resistor RI5 are
thanthe cuto? voltage of the tube and a
connected in series from the terminal SI to the 65 tive
second voltage more positive than the voltage to
supply line I9. An adjustable tap on the resis
which the grid is limited by the grid current.
tor RI 5 is connected through a capacitor CI 2 and
Thus, when tube V5 is conductive, the voltage of
another resistor RIS to the grid of tube V4.
The operation of a positive bias multivibrator iii; the grid tube V5 goes below cutoff and negative
of this type is well known an consequently only 70 clipping of the wave produced by the multivi
brator results. When tube V5 is non-conductive,
a brief description thereof is needed here. If it
the grid voltage of tube V6 tends to become
is assumed that the capacitor banks are set as il
highly positive but is limited to a value slightly
lustrated in the drawing and the tubes have al
ready been warmed, then when voltage is applied - above the cathode voltage and positive clipping
to the multivibrator through lines I8 and I9, one
tortion inthe wave’ at ‘high frequencies. ‘ At low
the resistor R21 to provide a polarizing .potene.
tial to the capacitorto maintain it in goodJcon---~
7 The vcapacitor'C I 4
i provided-‘- to prevent disa
an —-eflicient ‘ direct ~ * coupling-yv - rela-~~ >
To obtain another square wave output ,'l80° out;-_
of phase with that appearing between terminals“
A and G, the third stage is provided in the am.--'
pli?er l2. Tube V8 is illustrated-as a pentode'
ti'vely/ ¥free~ vof distortion, ‘is afforded ~ by‘ the’ are».
rangement' of~resistorsRl 9;‘ R2 0~and~1R211 How~
ever,~,when the multivibrator-operates at aihigh
frequency; the input capacitance-ofthe tube V15v
becomes appreciable and ‘with’ the impedance‘
connected as a triode with its anode connected
through resistor R3itc line I‘! and its cathode.
connected to line l9. Tube V8'is coupledlto the
output of tube V‘! by coupling similar to that be-"
tween tubes V1 and V6. This coupling comprises»
offered by resistors R19 "and ‘Rue-‘between the
anOdeof-tube V5" and the grid~of ‘tube V6; this ‘
input capacitance would~,in the absence'of capaci
tor C I‘4,‘-prevent the grid oftube- V6‘ fromfollow
ing-instantaneousvoltage changes at t‘heanodev
resistors R28 and R29 connected between. the 1
anodeof tube .V‘l and. line 20 and capacitor C18
of ‘tube V5? The capacitor Cl4= is of 'a'size-o?‘er
ing a relatively "low impedance at high ~frequen=
cies- and so provides a';low impedance path “from
the anode‘of-tube-VE to-the grid of tube V6‘. The:
capacitor C14 thus servessto- balanceout the ef-fect of the input capacitance-of the tube "and
. connectedin shuntacross resistor R28 with the.
fér's' ell-relatively’ high impedance. However, the
a terminal B and the ground terminal G. Thev
terminal B is connected to the junction point be,
junctionbetween resistors R28 and R. 25 con-v
nected to the control grid of tube V8 through re
sistor R30.
The. action of. tube. V8 is the same asthat;
thereby eliminates the'distortion in the wave 20 described fortube Vl, but of course, the output.
which otherwise would appear at: high frequen
willbe ‘18.0;o out of phase with the output ofv tube _
V1. The output fortube V3 is obtained between...
cies. ‘At low frequencies, thecapacitor CH of
input capacitance of the tube V6 is not suffi
ciently great tocauseappreciable‘.‘distortion at
these lowv frequencies.
25 tween a resistor R32 connected .in series with a
pairof parallelcapacitors C19 and C20; between
Thus,: this coupling: are. .
rangement. provides efficient coupling at both the
an adjustable tap. on resistor R3l and the line
highzand .low frequencies over a very wide fre
quency: band.
I ‘l. "Capacitors C19 and C20 are similar in struc:
ture and function to vc'apacitorsCHi and 0H,.
The second stage of they ampli?er I2,,1corn~ 30
prising :tube V1, is connected to, the ?rststage- by
respectively. .
A synchronizing. outputimpulse of ?xedv ampli-.,,
a coupling arrangement similar to that between
the oscillator and the ?rst stage of the ampli?er.
tude may be obtained from a terminal S2 con
nected through a capacitor C2l to the junction
between a pair of resistors R33 and R34 con
triode with its anode connected to line I‘! through 35 nected between the anode of tube V8 and line
a resistor R26 and its cathode connected to line
IT. This synchronous output may be used for
Tube V1 is shown as a pentode connected as a
l9. Resistors R23 and R24 are connected be
many purposes which are well known to those
tween the anode of tube V6 and the supply line
familiar with the use of square Wave generators.
20. The junction between resistors R23 and R24
In a typical square wave generator constructed
is connected to the control grid of tube V'I 40 and operated satisfactorily and connected as
through a resistor R25 and a capacitor Cl5 is
shown in the drawings, the components have the
connected in shunt across the resistor R23.
following values or types:
As previously explained, the tube V6 of the ?rst
ampli?er stage has a clipping action. Tube V6
also provides sui?cient amplitude in its output
voltage to permit further positive and negative 4.5
clipping by the tube V‘! of the second stage.
A pair of parallel connected capacitors Cl 6 and
CI‘! are connected in series with a resistor R2‘!
between the adjustable tap on the resistor R26 50
and the line H. An output terminal A is con
nected so that between terminal A and a grounded
terminal G on line I‘! there appears a square
wave as produced across the resistor R21. The
capacitor-resistor circuit CIG, CH, and R21 pro
vides a coupling whereby the output of the gen
erator may be coupled to various other apparatus
without affecting the generation of the square
CI, C2—40 mfd. 350 wv.
C3—16 mfd. 350 wv.
wave itself.
The capacitors CIS and C1‘! are
C5, C5a--0.2 mfd.
thus coupling capacitors. One of these capaci 60 C6, CHIP-0.015 mfd.
tors CNS is quite large and is preferably an elec
C1, Ola-0.00115 mfd.
trolytic capacitor, while the other capacitor C"
C8, C8a-—0.000075 mfd.
is quite small and is preferably a paper ca
C9, C9a-—0.000025 mfd.
pacitor. Thus, the capacitor Cl‘! can efficiently
[email protected]—-0.25 mfd.
pass the high frequency while capacitor CIB ef 65 CH, CH, 020-01 mfd.
?ciently passes the low frequency. An elec
Cl2-~0.01 mfd.
trolytic capacitor C16 may be satisfactorily em
Cl3, C16, CIB, C2 l--50 mfd.
ployed in this position in as much as the square
wave has now been provided at a sufficiently am
CH, CH‘), Cl8-25 mfd.
pli?ed strength that any inaccuracies arising 70
therefrom are negligible.
Consequently, a leak
age through the electrolytic capacitor will not
have any material effect. It is also to be noted
that the more positive terminal of the electrolytic
capacitor C l 6 is connected to the ground through 75
RI—1500 ohms 25 W.
R2-16000 ohms
R3, RI 4-15000 ohms
R4-—400 ohms 10 W.
R5, R6, R1, R8-5000 ohms
2,6 1 4,028
R9-—2 megohms
RI 0, RIM, RI5, RIB, R33--5000 ohms
RI I, RI Ia, RIB, R21, R32—100,000 ohms
RI2—200,000 ohms
RI3-25,000 ohms
RI'I--2500 ohms
RI 9, R2 I—360,000 ohms
R20--250,000 ohms
R22, R25, R30, R34-—10,000 ohms
R23—510,000 ohms
R24—390,000 ohms
R26, R3 I—3,000 ohms
R28, R29—ll70,000 ohms
said means being adjustable to provide said
oscillating voltage at any selected frequency with
in a predetermined Wide frequency band, an
electronic ampli?er tube having an anode and a
cathode connected in an output circuit with the
cathode connected to a source of voltage to be
substantially maintained at a second voltage level
more positive than said ?rst level, said tube also
having a control grid, a grid resistor connecting
10 said grid to an intermediate point on said divider
having a voltage below cut-oil voltage of the grid
during the more negative portion of the oscillat- >
ing voltage and above said second level during
the more positive portion of the oscillating volt
While there have been shown and described
age, and a shunting capacitor connected from the
and pointed out the fundamental novel features 15 end of said divider opposite said one end to said
of the invention as applied to a preferred embodi—
ment, it will be understood that various omissions
and substitutions and changes in the form and
details of the device illustrated and in its opera-.
tion may be made by those skilled in the art
without departing from the spirit of the inven
tion. It is the intention, therefore, to be limited
only as indicated by the scope of the following
What is claimed is:
‘A square wave generator comprising a resistive
voltage divider having one end thereof connected
to a source of voltage to be maintained at a
point and‘ offering relatively high impedance at
low frequencies and relatively low impedance at
high frequencies with said band.
The following references are of record in the
?le of this patent:
Number _
Smith ___________ __ May 24, 1938
White ___________ __ June 14, 1938
?rst voltage level, means connected to said divider
for impressing thereacross an oscillating voltage
Lindenblad _____ __'_ Sept. 27, 1938
Bedford __________ __ May 7, 1940
having a Wave form approaching a square wave,
Clark ___________ __ July 13, 1943
Certi?cate of Correction
Patent No. 2,514,023
July 4, 1950
It is hereby certi?ed that error appears in the printed speci?cation of the above
patent requiring correction as follows:
Column 8, line 19, for the Word “with” read within;
and that the said Letters Patent should be read as corrected above, so that the same
may conform to the record of the case in the Patent O?ce.
Signed and sealed this 3rd day of October, A. D. 1950.
Assistant (Jammz'ssz'oner of Patents.
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