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Патент USA US2111702

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March 22, 1938.
‘ M_ J_ O, STRUTT
2,111,792
CIRCUIT ARRANGEMENT FOR AMPLIFYING ELECTRIC OSCILLATIONS
Filed July 15, 1936 v
03
INVENTOR
M-J- 0- STRUTT
ATTORN EY
Patented Mar. 22, 1938
'l‘i“
liiE'
i
2,111,702
CIRCUIT ARRANGEIVIENT‘ FOR ANIPLIIFYING
ELECTRIC‘ OSCILLATIONS
Maximiliaan Julius Otto Strutt, Eindhoven,
Netherlands, assignor to N. V. Philips’ Gloei
lampenfabrieken, Eindhoven, Netherlands, a
corporation of the Netherlands
7 Application July 15,1936, Serial No. 90,790
In the Netherlands July 26, 1935
(01. 1'7 9—-17 1)
grid and the anode within the amplifying valve.
As is well known, there is in amplifying cir
cuits comprising amplifying valves retroaction of The part that depends on the frequency can be
controlled by modifying the coupling between
the anode circuit on the control grid circuit which
under certain conditions results in self oscillation the supply conductors to the electrodes of the
1 Claim.
5 of the circuit. In the case of comparatively low
frequency of the oscillations to be ampli?ed ret
roaction is brought about solely by the anode
grid capacity of the amplifying valve. In the case
of very high frequencies the retroaction of the
10 anode circuit on the control grid circuit is not
only due to the anode-control grid capacity but
also to the mutual induction between the cathode
lead and the conductors to the auxiliary grids and
to the anode.
The total reaction in the case of
15 very high frequencies can, however, be reduced
to an equivalent impedance between the anode
and the control grid which consequently com
prises all of the reactions due to the above-men
tioned causes. Now, measuring operations car
20 ried out on a great number of amplifying valves
revealed that this equivalent impedance. can be
represented by a capacity Cag as is indicated by
the formula:
'
r In this formula Cago designates the static ca
'
The single ?gure of the drawing shows sche
matically a tube arrangement used to explain
in more detail the various features of the present
invention. In said drawing a tube T is shown
provided with an anode, a cathode and a control
electrode. The control electrode is connected
to the cathode of the tube through an external
circuit including the grid impedance Zg and the
anode of the tube is shown connected to the
cathode thereof through the plate impedance Zp. 15
The mutual between the supply conductors is
indicated by M and the capacity existing be
tween the grid and plate is indicated by the label
Cago. In accordance with the invention, it is
evident that the mutual M may be made so as
to be equivalent to the capacity between the grid 20
and plate so as to produce an equivalent ca
pacity which is substantially zero for any par
ticular frequency which it is desired to amplify.
The circuit arrangement according to the in
vention is particularly important in connection 25
pacity between the anode and the control grid,
with ampli?ers that are always tuned to one and
the same frequency, as is the case, for example,
in television receiving sets. In the case of tunable
f designates the frequency of the oscillations to
ampli?ers the frequency at which the equivalent
30 be ampli?ed and A is a constant which is deter
capacity is zero may be chosen so as to be equal
mined by the mutual induction between the sup
to the frequency at which self-oscillation would
ply conductors.
The formula shows that the equivalent capacity
be set up but for the use of the invention.
I claim:
The method of eliminating at a predetermined
is composed of a positive constant part and a
3
valve.
negative part depending on the frequency. Thus,
according to the invention'the constant'part of
the equivalent capacity or that part which de
pends on the frequency is so adjusted that for
40 the frequency of the oscillations to be ampli?ed
the equivalent capacity is substantially zero.
The constant part Cago of the equivalent ca
pacity may be controlled for example by a suit
able choice of the screening between the control
0
desired frequency the coupling between the input
and output circuits that occurs within the tube
structure itself which comprises proportioning
the grid-plate capacity of the tube and the mu
tual inductance between grid and plate leads
within the tube to produce equal and opposite a
coupling effects at said frequency.
MAXIMILIAAN JULIUS OTTO STRUTT.
0
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