Download May l5, 1951 B. c. FLEMlNG-wlLLsAMs 2,552,949 Brian C. Fleming

May l5, 1951
B. c. FLEMlNG-wlLLsAMs
2,552,949
WAVE-FORM GENERATOR
- Filed Feb. 24, 1948
Brian C. Fleming-Williams
Patented May 15, 1951
2,552,949:
UNITED STATES» PATENT OFFICE
2,552,949
WAVE-FORM GENERATOR
Brian ICliüord Fleming-Williams, London, Eng
land, assignor to A. C. ICossor Limited, London»,
England, a British company
Application February 24, 1948, Serial No. 10,386
In Great Britain April 19, 1944
.
Section 1, Public Law 690, August 8, 1946
Patent expires April 19, 1964
8 Claims. (Cl. 250-27)
l
2
This invention relates to thermionic valve cir
A diode D4, connected between the suppressor
and cathode o1" valve VI, is provided to prevent
cuits serving for the generation of linear poten
tial sweeps and/or abrupt potential steps and
being of the kind comprising a valve amplifier
having a point in its anode circuit connected
through a differentiating network to 4a point of
the suppressor potential from rising appreciably
i)
above that of the cathode.
Alternative arrangements are shown for the `ap
plication of either positive-going or negative
constant potential, and having its input voltage
derived from the output of this differentiating
going firing pulses to the circuit. Terminal Tl,
for the application of positive-going ñring pulses.
network, so that a substantially linear potential
sweep of the valve anode is obtained.
A circuit of this kind according to the inven
tion comprises a rectiñer connected between one
of the valve electrodes and a source of potential
variations for ñring whereby a potential varia
is coupled to the anode of diode D3 through con
denser C3. This anode is normally biassed about
2U volts negative to its cathode so that the am
tion may be applied to this electrode to initiate
a potential sweep of the valve anode, and whereby
this electrode is thereafter isolated from the nr
ing source throughout the course of the anode
potential sweep. _
The accompanying drawing shows a circuit
diagram of an arrangement embodying the in
vention, which, in response to the application of
a ñring pulse of potential, produces at one out
put terminal a single linear potential sweep fol
lowed by automatic return, and at another out
put terminal a single square wave cycle of po
tential.
The valve VI is a pentode which may be of the
Mazda AC/ SP1 type.
plitude of the pulse must exc/eed this value be
fore it becomes effective/on the circuit.
This
bias is given by potentiometer R8, R9, which is
connected between earth and the foot of resistor
R6 and has the voltage across it smoothed by
condenser C4.
The circuit has a stable condition with the
anode approximately at the potential of the slider
of potentiometer Rl Iand `with the suppresser at
the potential of its bias source. The whole of the
cathode current oi valve Vl is then flowing to its
screen. The control grid is held approximately
rat earth potential by the diode D2, and the poten
„» tial between cathode and control grid is therefore
determined by resistor R5.
Suppose that a positive-going firing pulse is
now applied at terminal TI suñicient to overcome
t
the bias applied between the electrodes of diode
The cathode of this pentode Vl is connected 30 D3; then the potentials of the screen and sup
to earth through a biassing resistor R5.
pressor are raised together. Anode current be
The control grid and anode are ’coupled by a ` gins to flow in valve V! at the expense of that
condenser Ci, and the control grid is connected
which has been flowing in diode DI. When this
through a high resistance R3 to the positive line,
becomes sufficient for diode Dl to be cut 01T, the
which may be at 300 volts to earth, preferably 35 potential of the anode of valve Vl begins to fall.
stabilized. A small stopper resistance Rl 0 is con
Owing to the coupling between anode and control
nected in the lead to the control grid to prevent
grid through condenser CI, the control grid is
parasitic oscillations. A diode D2 having its
driven negative, with the results that diode D2
cathode connected to earth prevents the control
is cut off and that the cathode current of valve
grid potential from rising appreciably above that 40 VI is reduced. The screen potential therefore
of earth.
rises further, 'carrying the suppressor with it.
The anode is connected to the positive line
The eiîect is cumulative and proceeds extremely
through 1an anode load resistor R4. It is also
rapidly until a meta-stable state is reached inl
which the `anode current is approximately the
connected through a diode DI to the slider of a
potentiometer Rl , which is connected between the 45 sum of the currents through resistors R3 and R4.
In this meta-stable state the current through re
positive line and earth. This prevents the anode
potential from rising appreciably above the po
sistor R3 is the current flowing to condenser CI.
During the change from the stable to the meta
tential selected by the slider of potentiometer RI.
The screen and suppressor are coupled by a
stable state, the fall of anode `and control grid
condenser C2. The screen current is derived from 50 potentials is not more than about 3 volts. At the
the positive line through resistors R6 and R1, the
same time the rise of screen potential may be
about 60 Volts. The suppressor potential is, how
voltage across resistor R6 being smoothed by con
ever, prevented by diode D4 from rising lappre
denser C4 to earth. The suppressor is biassed
ciably above that of the cathode, and the con
through resistor R2 from a source which may be
about 15 volts negative to earth.
' 55 denser CZ therefore becomes charged. This
2,552,949
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i 3
charge leaks away slowly through resistor R2 dur
ing the subsequent cycle, but may leave the sup
pressor with considerably more negative bias at
the time of arrival of the next ñring pulse than
is providedV by its negative bias source alone. The
suppressor is therefore to some extent automati
cally biassed and so the actual value of negativev
bias voltage applied is not very critical.
Negative-going firing pulses applied at termi
nal T3 reach the anode of pentode VI by pass
ing through coupling condenser C5 and diode D5.
ïn view of the fact that thev tapping of potentiom
eter RI is adjustable, a separate D. C. source B
is employed to provide bias for diode D5, in or
der that negative-going firing pulses applied at
terminal T3 shall be ineffective unless they ex
ceed a predetermined minimum amplitude.
During the meta-stable regime the anode po
tential will make a linear sweep downward while 10 Resistor RII is provided to increase the imped
ance across whichv the firing pulse builds up.
the control grid potential- makes an :approxi
When a negative-going firing pulse is applied
mately linear sweep upward across a small por
to the anode of pentode Vl, the transition from
tion of its grid base. The velocities of theseV po
the stable to the meta-stable condition will pro
tential sweeps are determined by the Values of
ceed as a result of those same cumulative effects
resistor R3 and condenser Cl. The discharging
as have been described as the result of the ap
rate of condenser CI will approximately corre
plication> of a positive-going firing pulse from
spond to the discharging rate which it would have
terminal TI to the screen.
if connected in series with a, resistance of value
As with the network associated with terminal
G times R3 across a direct voltage source 'of value
G times the voltage of the positive line, G being 20 TI, an additional bias will be applied to diode D5
foi‘ a periodi after ñring. This is due to the cur
the gain of the valve Vl asl an ampliñerV inv the
rent which ñows> from condenser C5v through
present circuit. While these sweeps of the anode
diode D5.; and its duration will depend upon the
and control grid potentials proceed, the potential
time-constant C5, RI l, governing the recharging
of the screen will remain >approximately constant,
andV therefore'that of the suppressor also because 25 of condenser C5.
Yet another alternative Afiring circuit is shown
the time constant CZR-Z is long relative to the
in connection with terminal T4, and this again
duration of the sweep.
wil-l not normally be provided if' either of the net
The termination of the meta-stable regime will
works associated with terminal Tl or T3 is
occur automatically when the anode has reached
a very low potential, because the current to the 30 present.
Terminal Tft is used for positive-going firing
screen then increases with the result that screen
pulses and these are applied through diode D6
and suppressor potentials both fall. The anode
tothe suppressorV of pentode VI, which serves as
current is then cut off, and the anode potential
a second control grid, i. e. a grid controlling
proceeds to rise exponentially as condenser CI
is charged through resistor R4 and diode D2. 35 the division of current between anode and-screen.
If bias is desired, resistor-RIZ will be connect
Diode D2 prevents the potential of the control
ed to a point of ñxed potential more »negative than
grid from rising above earth potential. When
that to which resistor 'R2 is connected. A
the anode potential reaches that'of the slider on
temporary increase in bias, after ñring, will-again
established and the circuit is again ready >for op 40 occur as a result of the discharge condenser C5
through diode D6, and-its time of decay willde'
`eration in response to a ñ-ring pulse. It will be
pend'on theStime-constant C5, Rl 2.
evident that the >potentialselected by the slider
If no bias is required for the purpose ofY pre
on potentiometer Rll setsY the amplitude of the
venting small potential variati‘ons from firing-the
ranode potential sweep independently of the veloc
circuit, negative-going ñring» pulses may be ap'
ity thereof.
plied'ïat'the cathode of diode DI. This avoidsthe
The ñring pulse network shown in connection
necessity
of providing any of the additional diodes
with terminal TI has the advantage that, when
D3,'D5, D6. ïf this method is to be'used, it will
one 'îiring has occurred, 'an'interval of time iol"
be preferable that a further resistorY be inserted
lows during which it cannot be caused again ex'
between the tapping on potentiometer Rl and the
cept by a stillV larger pulse than that which is-d'e‘
cathode of this diode to provide an'ad'equate im'-l
termined by the value of the steady bi'as applied
pedance for the nring pulse to build up on.
to diode D3. The cause of this eiîect is the
If it is desired-to obtain linear potential sweeps
temporary increase in bias due to the further
as output from the circuit, these may be taken
charging of condenser C3 by the current which
flows through diode D3 when ñring occurs. The 55 from the anode of ~valve VI. If abrupt potential
steps are desired, these may be taken from the
additional charge leaks away slowly through resis
potentiometer RI, the stable condition is vagain
tor R8.
Diode D3 serves to isolate, during the meta
stable regime, the generator circuit under con
screen.
The form of the wave front of the po
tential step is identical with >that of the upper
part of a positive ñring> pulse applied at terminal
sideration from the source (not shown), con 60 Tl, provided that this pulse rises'rapidly.
The following table gives a set of Values forthe
nected to the terminal Tl which provides the
various components of the circuit, suitable for use
firing pulses.
for generating linear potential sweeps and square
This isolation prevents the >possibilities that
waves of. potential havingv durations ofthe order
further potential variations in the ñring source
might either stop the anode potential sweep or 65 of 100'microseconds.
at least spoil its linearity. It also prevents the
generator circuit from reacting upon the 'firing
'
SOllI‘Ce.
Terminal T3 and the network associated there
with, including diode D5, provide an arrange
Rl=25 kilohms
VRI l :50 kilohms
R [2:150 kilohms
R221 meg'ohm
R3=500 kilohms
70 R4L-:300 kilohms
C i =’100 lp-ico'farads
`C2=0.001 Inicrofarad
ment for applying negative-going >firing pulses
R5=2`00 ohms
to the circuit. This network will normally be
provided only as an alternative to, and not in
RôzRL-¿IO kilohms
C3.:'U.O1> microfarad
04:10.25.' micrcfarad
addition to the network‘com’prising lterminal TI _
R9'-_-'100 kilohms
'0620,01 micrófarad
and diode D3.
RWI-500 ohms
¿Cäzûß-lmicroíarad
’
`
'
'
2,552,949
5
6
to said first control electrode, a further con
denser connected between said second and third
ponents, the duration of the generated potential
control electrodes, a source of firing potential, a
sweep and square-wave may be lengthened to the
rectifier device connecting said source of ñring
order of several seconds.
The circuit described may be converted into a Ul potential to one of the electrodes of said tube,
and a source of potential biasing said rectiñer de
free-running time-base or square-wave generator
vice to be normally non-conducting in the absence
by reducing the bias on the suppressor grid, and
of iiring potential from the said ñring source.
the firing arrangements described may then be
4. An electron discharge tube circuit accord
used for synchronising,
lO ing to claim 3, for use when the source of iiring
I claim:
potential provides a negative-going firing pulse,
l. A thermionic valve circuit for the generation
wherein said rectifier device is connected to said
of linear potential sweeps and abrupt potential
anode and is arranged to conduct away from
steps comprising an electron discharge tube hav
said anode.
ing a cathode, an anode, a first control electrode,
5. An electron discharge tube circuit accord
a screen grid between said control grid and anode
ing to claim 3, for use when the source of ñring
and a second control electrode between said
By appropriate alteration of the values of com
screen grid and anode, a source of potential, con
nections between said tube and said source for
applying to said anode and screen grid potentials
positive relative to said cathode, a resistor in
cluded in said anode connection, a second resistor
and a condenser, a connection from said anode,
through said second resistor and said condenser
in series to the positive terminal of said source, a
connection from the junction of said second re-sistor and said condenser to said ñrst control
electrode, a iiring terminal to receive a potential
variation for firing said tube and a rectifier hav
ing its anode connected to said terminal and its
cathode connected to said second control
electrode.
2. A circuit according to claim 1, including a
time-constant circuit comprising a second re
sistor and a second condenser, said second con
denser being connected between the anode of said
rectifier and said terminal and the time constant
of said time-constant circuit being not less than
the period of said potential sweeps.
3. An electron discharge tube circuit for thek
generation of linear potential sweeps and abrupt -
potential steps, comprising an electron discharge
potential provides a positive-going ñring pulse,
wherein said rectifier device is connected to said
third control electrode and is arranged to con
duct towards said third control electrode.
6. An electron discharge tube circuit according
to claim 3, for use when the source of ñring po
tential provides a positive-going firing pulse,
wherein said rectifier device is connected to said
f' second control electrode and is arranged to con
duct towards said second control electrode.
7. An electron discharge tube circuit according
to claim 3, and including a third condenser con
nected between said source of firing potential and
said rectiñer device, and a leak resistor for said
third condenser providing a time constant of
discharge of said third condenser of not less than
the duration of each of said potential sweeps. `
8. Circuit according to claim 3 and including
a biasing resistor connected between said cathode
and said source of space current, and a rectifier
having its anode connected to said other terminal
of said condenser and its cathode connected to
the negative terminal of said source of space cur
rent.
BRIAN CLIFFORD FLEMING-WILLIAMS.
tube having at least rive electrodes including a
REFERENCES CITED
cathode, an anode and at least three control elec
The following references are of record in the
trodes, a first of said control electrodes being
nearest said cathode, a second being nearest said 45 ñle of this patent:
UNITED STATES PATENTS
anode, and a third being intermediate said i'lrst
and second control electrodes, a source of space
Number
Name
Date
current, a connection from the negative terminal
2,164,968
Urtel et al. __________ July 4, 1939
of said source to the cathode of said tube, a con
2,172,746
Young ___________ __ Sept. 12, 1939
denser having one terminal connected to said 50 2,199,278
Black ___________ __ Apr. 30, 1940
anode, a resistor, a connection from the other
2,270,405
Black ____________ __ Jan. 20, 1942
terminal of said condenser through said resistor
to the positive terminal of said source, a connec
tion from said other terminal of said condenser
2,418,538
2,457,974
Yetter ___________ __ Apr. 8, 1947
Bliss _____________ __ Jan. 4, 1949