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Патент USA US3029405

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April 10, 1962
A. M. SKELLETT
3,029,395‘
REGENERATIVE CIRCUIT FOR COLD CATHODE VACUUM TUBES
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United States atent thee
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3,029,395
Patented Apr. 10, 1962
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cuit of FIG. 1 is connected through a capacitor 36 to a
source of control signals and is connected through a re
sistor 38 to a point on the source 30 of above ground po
tential. The outer grid 12 which serves as a screen grid
in the circuit of FIG. 1, is connected to the source 30 at
3,029,395
REGENERATIVE CIRCUIT FOR COLD CATHODE
VACUUM TUBES
Albert M. Skellett, Madison, N.J., assignor to Tung-Sol
Electric Inc., a corporation of Delaware
Filed June 22, 1959, Ser. No. 822,102
a point of potential intermediate that of the control grid
and of the anode.
In accordance with the invention the network 34 in the
The present invention relates to cold cathode vacuum
sustaining grid circuit is a frequency responsive element
tube devices, more particularly to circuits incorporating 10 comprising a parallel arrangement of an inductor 40 and
such devices and comprises a novel regenerative circuit
capacitor 42 tuned for parallel resonance at a preselected
that includes an ampli?er having a cold cathode. Cold
frequency. The function of the network 34 will become
cathodes employed in vacuum tube ampli?ers and the like
apparent from the following discussion.
7 Claims. (Cl. 330-112)
comprise a metal base or sleeve of nickel or the like
When the tube 26 is drawing current some electrons
coated with a porous sponge-like layer containing mag—
nesium oxide. Such coating has the characteristic of
copious and self-sustaining electron emission once the
emission is initiated and provided there is present an
electrode at a higher potential for collection of the emitted
are collected by the sustaining grid and other electrons
pass through that grid to the other electrodes of the tube.
Thus a small current flows in the circuit including the
electrons.
The new regenerative circuit includes ‘an am
pli?er or oscillator tube provided with such type cathode
and includes circuit elements connected to the sustaining
resistor 32 and network 34. When the control grid is
made more positive more of the electrons from the cath
20
ode pass through the sustaining grid to the electrodes of
the tube and accordingly the current to the sustaining grid
is reduced. This results-in a higher sustaining grid po
tential. The higher potential on the sustaining grid at
grid for augmenting the voltage swing of such grid when
an alternating signal is impressed upon the control grid
tracts more electrons from the cathode and hence tends
of the tube at'a predetermined frequency or frequency 25 to cause some regeneration‘. Thus the higher the imped
range
ance in the sustaining grid'circuit the greater will be the
Brie?y the new c-ircuit-corn-prises‘a frequency respon- ‘
regeneration of the tube. By making the network 34
sive network connected in series with a resistor between
frequency responsive so as to have maximum impedance
the sustaining grid of a cold cathode vacuum tube and
at a selected frequency the voltage swing on the sustain
30
the source of positive bias potential for the sustaining
ing grid will be enhanced at such frequency making the
grid. The frequency responsive network may be a circuit
circuit a truly regenerative circuit suitable for use in am
resonant at a preselected frequency to give maximum
pli?ers, oscillators, and the like.
impedance at such frequency or may be a ?lter type not
.Other frequency responsive networks could be sub
work having wider frequency response.
stltuted
for the speci?c circuit 34 shown in FIG. 1. When
For a better understanding of the invention and of cir 35 a response at high frequencies is desired, for example, the
cuits embodying the same reference may be had to the
frequency responsive network could be a simple inductor
accompanying drawing of which:
as in the speci?c circuit illustrated in FIG. 2 to which
FIG. 1 is a circuit diagram representing one embodi
reference may now be had.
ment of the invention;
In FIG. 2 the cold cathode vacuum tube of the circuit
FIGS. 2 and 3 are similar circuit diagrams representing 40 is indicated at 44. Constructionally it may be the same
other embodiments of the invention; and
as that of FIG. 4 and is shown like tube 26 of FIG. 1
FIG. 4 is a diagrammatic sectional view through the
except for a difference in the grid connections. In FIG.
cold cathode tube of the circuits of FIGS. 1 to 3 illus
2 the ?rst grid 8 and the third grid 12‘ are connected to~
trative of the construction thereof.
ge'ther to serve as the control grid of the circuit. For
Referring ?rst to FIG. 4, the cold cathode vacuum
this purpose they are connected through the capacitor
tube of the circuit may comprise an outer envelope 2 of
36 to the input terminal for the control signal and through
glass or the like having mounted therein an electrode
resistor 38 to a point on the source 30 of above ground
structure comprising an anode 4, a cathode indicated gen
potential. In this embodiment of the invention the sec
erally at 6, an inner grid 8, a second grid 10 encompassing
ond grid 10 serves as the sustaining grid and that grid
the grid 8, and a third grid 12 encompassing the grid 10.
is connected through an adjustable resistor 46 and induc
The grids 8, 10 and 12 are mounted on suitably aligned
tor 48 to a point on the source 30 intermediate the po
posts 14 and aligned with the posts 14 is a ?lament 16
tential of the control grid and of the anode, which latter
supported from a rod 18 and adapted for use in initiating
is connected as in FIG. 1, through the primary winding
emission from the coating of the cathode. The cathode 55 of output transformer 28 to the positive terminal of the
source 39. With the inductor 48 in the sustaining grid
comprises a sleeve 20 of nickel having an outer coating 22
circuit regeneration will occur at high frequencies, the
thereon of magnesium oxide in porous sponge-like form.
higher the frequency the greater the regeneration. The
Within the sleeve 20 is a ?lament 24 used only for process
principle of operation of the circuit of FIG. 2. is substan
ing the tube when initially constructed and not used there
after.
60 tially like that of PEG. 1 in that, with increase in potential
on the control grid the current to the sustaining grid is
In FIGS. 1, 2 and 3 the cold cathode vacuum tube has
reduced with consequent increase in potential on that grid
been shown conventionally but the elements thereof are
and such increase in potential further augments cathode
identi?ed by the reference numerals used in FIG. 4.
emission. The inductor 48 in the sustaining grid circuit
In FIG. 1 the cold cathode vacuum tube 26 is shown
the voltage swing of the sustaining grid with
with its anode 4 connected through the primary winding 65 enhances
increase in frequency.
of an output transformer 28 to the positive terminal of
In the circuit of FIG. 3, to which reference may be
had, the frequency responsive network in the circuit of
6 connected to ground and to the negative terminal of
the sustaining grid comprises two tunable circuits 50 and
source 30. The inner grid 8, which in the circuit of FIG.
52 inductively coupled together. Circuit 50 comprises a
1 is the sustaining grid, is connected through a resistor 32 70 capacitor 54 and variable resistor 56 connected in series
a source 30 of direct current energy, and with its cathode
and network 34 to the positive terminal of the source 30.
across an inductor 58 and circuit 52 comprises an in
The second grid 10, which is the control grid in the cir
ductor 60 coupled to inductor 53 and connected in series
aoaaaes
A
and capacitor tuned for maximum impedance within the
selected frequency range.
3
with a variable resistor 62 and capacitor 64. The remain
der of the circuit of FIG. 3, being the same as that of
FIG. 2 needs no description. With the circuits 5t} and
52 tuned to the same frequency, high impedance over
a relatively wide band of frequencies may be obtained
by adjustment of resistors 56 and 62 to give the proper
circuit Q’s. Thus regeneration can be obtained with the
4. A regenerative circuit comprising a source of direct
current potential, :1 cold cathode vacuum tube ampli?er
having a cathode of the type comprising a metal base
having a porous sponge-like oxide coating thereon adapted
to emit a self-sustaining stream of electrons once emis
circuit of FIG. 3 over a Wider range than with the cir
sion is initiated, a sustaining grid, at least one control
cuit of FIG. 1.
Obviously the network 3-4 of FIG. 1 could be sub
10 being connected to said cathode, connections between
grid and an anode, the negative terminal of said source
stituted for the inductor 48 in the particular circuit of
FIG. 2 and for the coupled circuits 50 and 52 of FIG. 3.
Conversely the inductor 48 of FIG. 2 could be sub
stituted for the network 34 in the circuit of FIG. 1. Also
frequency responsive networks other than those illustrated 15
could be employed. '
The invention has now been described in connection
with the two embodiments thereof. Other circuit ar
said source and said sustaining grid and between said
source and said anode to maintain said sustaining grid
and anode at above cathode potential and a frequency
responsive network in the connection between said sus
taining grid and said source.
5. The circuit according to claim 4 including a stabi
lizing resistor in series with said network in said last
mentioned connection.
6. The circuit according to claim 4 wherein said net
20 work comprises a resonant circuit tuned for maximum
those skilled in the art.
impedance at a preselected frequency.
The following is claimed:
7. The circuit according to claim 4 wherein said net
1. The combination with a cold cathode vacuum tube
work comprises a pair of coupled circuits tuned for
having a cathode of the type comprising a metal base hav
maximum impedance over a preselected band of fre
ing a porous sponge-like oxide coating thereon adapted
rangement embodying the invention will be apparent to
to emit a self-sustaining stream of electrons once emis
25
quencies.
‘ .
sion is initiated, a sustaining grid biased positively with
respect to the cathode, at least one control grid and an
References Cited in the ?le of this patent
anode, of means for enhancing the voltage swing of the
sustaining grid at a preselected frequency range, said
UNITED STATES PATENTS
means comprising a frequency responsive network con 30
nected to the sustaining grid and through which the posi
tive bias is impressed upon such grid.
2. The combination according to claim 1 including
a stabilizing resistor connected in series with said net
35
work.
3. The combination according to claim 1 wherein said
network comprises a parallel arrangement of inductor
2,426,681
2,513,727
2,577,461
2,621,264
2,675,432
2,802,127
2,842,706
Adler _______________ __ Sept. 2,
Koch ________________ __ July 4,
Greefkes _____________ .._ Dec. 4,
Hultberg _____________ __ Dec. 9,
Pan _________________ __ Apr. 13,
Dobischek ___________ .. Aug. 6,
Dobischek ____________ __ July 8,
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