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Патент USA US3084268

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Apnl 2, 1963
A. |_. CLELAND
3,084,265
THRESHOLD TRIGGER HAVING REGENERATIVE FEEDBACK BUT
I
MAINTAINING CONDUCTION ONLY DURING
PRESENCE OF INPUT SIGNAL
Filed June a, 1959
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INVENTOR
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Aaron Zyle C’Zelazzd
BY
W'?vm,’ LAW ¢ATTORN§§
MM
FM (anertil) (-56
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W5 % ‘mag.
3&84255
Patented Apr. 2, 1963
1
2
ground.
3,084,265
THRESHGLD TREGGER HA‘ViNG REGENERATEVE
FEEBBA‘CK BUT MAENTAENHNG ‘CUNBU‘CTHQN
GNLY DURENG PRESENCE 0F INPUT Si-GNAL
Am'on Lyle Cieland, Manvilie, N..i., assignor to Aircraft
Radio Corporation, Boonton, Ni, a corporation oi
New Jersey
Filed June 8, 1959, Ser. No. 818,594
8 (Jlairns. (Cl. EFL-S35)
Resistors l9 and 21 are so selected that base
17 is biased slightly above ground but insufficient to
render the transistor 11 conductive when emitter 12 is
near ground potential and collector 14 has a positive
potential of about 10 volts.
‘
From the output of transistor 11 at collector l4 and
across load resistor 15 a coupling lead 23 is connected
to base 24 of a second transistor 25, of the PNP type,
which is likewise normally biased to cut oh‘ by having
10 its emitter 26 connected through emitter follower resistor
This invention relates to a threshold trigger circuit of
27 to a source 28 of positive potential of about 10 volts
the type which is rendered operative upon receipt of a
signal and continues in operation as long as the signal
persists. More speci?cally, the invention concerns a
threshold trigger circuit utilizing transistors which is
and its collector 29 connected through load resistor 31
to ground. If transistor 11 ‘is rendered conductive, as
by adjusting the potential of its base 17, the potential
rendered operative upon receipt of a signal to actuate a
switch or other load and continues in operative condi
of base 24 is lowered with respect to emitter 26 su?i
ciently to render transistor 25 conductive. When this
occurs, the voltage across emitter follower resistor 27
tion until the signal terminates at which time the trigger
circuit becomes inoperative.
is applied through coupling resistor 33 in a regenera
during the period which the radio signal persists.
sistors 13 and 33 which are connected in series with re
sistor 27 between source 28 and ground.
Should a DC. potential of the desired threshold level
tive ‘feedback circuit to emitter 12 of transistor 11. In
A major object of this invention is to provide a thresh 20 this way, the potential of emitter 12 is lowered to ren
old trigger circuit which draws very little current from a
der the transistor 11 more conductive. However, the re
power supply while in its ready condition awaiting receipt
generative feedback potential applied to emitter 12 is
of a signal to become operative.
insufficient to render transistor 11 conductive in the ab
Another object of the invention is to provide a simple
sence of a signal of a threashold level applied to base
threshold trigger circuit which is light in weight and
17 in addition to the biasing potential from the voltage
particularly adapted for use in aircraft to respond to the
divider of resistors 19 and 21. Emitter 12 is normally
receipt of a radio signal for operating an indicator lamp
biased slightly above ground by its connector between re
In the attainment of these objects an important feature
of the invention resides in the arrangement of a pair of
transistors of opposite conductivity types which are nor
mally biased to cut oil but directly connected together so
when one transistor is rendered conductive it applies po
tentials to the other transistor opposing the biasing poten
tials; and including a regenerative feedback circuit eli’ec~
tive when the other transistor is conducting for applying
potentials to the one transistor in opposition to biasing
potentials. Signals supplied to the base of the ?rst tran
sistor cause the trigger circuit to become conductive so
the output of either transistor may be utilized to operate
be applied to point 18 and base 17, transistor 11 would
become conductive upon the increase of the potential of
base ‘17. When transistor 11 thereby begins to conduct,
the voltage at collector 14 is reduced by reason of the
current drawn through load resistor 15 so the coupling
lead 23 lowers the potential of base 24 thereby render
ing transistor 25 conductive. This causes a flow of cur
rent in emitter follower resistor 27 which lowers the po
tential of emitter 26 and this lowered potential is sup
a switch such as a switching transistor.
plied through the regenerative feedback circuit to the
emitter 12 of the transistor 11 thereby rendering the
Where an alternating current signal is applied to the
base or“ the ?rst transistor, a capacitor is connected to the
coupling circuit and electrodes of the ?rst transistor so it
becomes charged as the ?rst transistor conducts during
reduces the potential on base 23 so continued regenera
alternate half-cycles of the alternating signal and thereby
applies a potential to the second transistor su?icient to
render that transistor conductive whereupon the regenera
tive feedback circuit becomes e?’ected. It is essential that
the regenerative feedback circuit apply potentials to the
?rst transistor which oppose the normal biasing poten
tials and thereby render the ?rst transistor more conduc
tive, but which are insufficient to continue conduction of
the ?rst transistor in the absence of a signal applied to its
base.
These and other objects, advantages and features of the
invention will become more apparent from the following
speci?cation taken in conjunction with the accompany
ing drawing which illustrates a threshold trigger circuit
embodying the invention in its preferred form.
As shown in the drawing the threshold trigger circuit
includes a ?rst transistor 11 connected in circuit with a
potential source so it is normally biased to cut off.
transistor 11 more conductive.
This, in turn, further
tive action increases conduction of transistor 25 to its
saturation point. In this way, as long as the signal ap—
plied at point 18 and base 17 persists, both transistors
continue to conduct and the output which appears across
load resistor 31 in the collector circuit of transistor 25
may be utilized to operate a switching transistor 35
which in turn may control a signal light 36 if desired.
As soon as the signal applied at point 18 is removed
or falls below the threshold level,‘ transistor 11 returns
to its non-conductive state and the potential of base 24
is raised to cut off transistor 25 so the signal light 35
will be extinguished.
Since in the usual case an alternating current signal is
available in a radio receiver for purposes of indicating
the presence of such a signal, the drawing shows such a
signal source at 36 coupled through a condenser 37 to
the point 13 and the base 17. When an alternating cur
rent signal is thus applied to base 17, transistor ll. acts
as a recti?er and is rendered conductive on alternate halt
cycles of the signal from source 36 which raise the po
Toward that end, this transistor 11, which is of the NPN 65 tential of base 17. This conduction of transistor 11 on
alternate half-cycles develops a direct current potential
type has its emitter 12 connected through resistor 13 to
across capacitor 38 connected between emitter 12 and
ground and its collector 14 connected through a load re
collector M. A charge on capacitor 33 lowers the poten
sistor 15 to a source 16 of positive potential which in
tial of collector l4 and coupling lead 23 to lower the
this case may be about 10 volts. Base 17 of the tran
potential of base 24. This charge on the capacitor 33 is
sistor 11 is connected to an intermediate point 18 of a 70 also effective through resistor 33 to raise the potential
voltage divider formed by resistors 19 and 21 extend
on emitter 26. Changes in potentials applied to the elec
ing between potential source 22, of about 10 volts, and
trodes of transistor 25 as a result of charging condenser
dosages
4
3
said other transistor, and regenerative feedback means be
38; render transistor 25 conductive to cause current to
?ow through resistor 27 and, accordingly, a drop in po
tween said third electrodes eitective on conduction of
said other transistor for applying potentials overcoming
tential at the emitter connection of resistor 27. This po
tential at emitter 26 is fed back to emitter 12 of transis
tor 11 to cause this transistor to conduct and thus initiate
the cut-off bias potentials on the electrodes of said one
transistor to render said one transistor conductive.
3. A threshold trigger circuit comprising a pair of
transistors of opposite conductivity types, each of said
transistors having an input electrode, an output electrode,
regenerative action to render transistor 2'5 heavily con-V
ductive. Through this regenerative feedback transistor '25,
will remain conductive as long as an adequate signal is
applied to base 17 of transistor 11. When transistor 11
is fully conductive, capacitor 38 is discharged through
and a third electrode, respectively, means for applying
cut-off biasing potentials to the electrodes of said transis
emitter 12 and collector 14 and the regenerative feedback
tors, means connecting the output electrode of one of
said transistors to the input electrode of the other of said
transistors, means for applying a signal to'the input elec
trodes of said one transistor for initiating conduction of
falls below the threshold level.
'
By way of example, the following is a tabulation of 15 said other transistor, and a regenerative feedback circuit
including a resistive element between said third electrodes
values which may be used for the components of the cir
effective on conduction of said other transistor for apply
cuit although it will be apparent that many variations
ing potentials overcoming the cutoff bias potentials on
are possible without departing from the invention:
the electrodes of said one transistor to render said one
connection will maintain conduction of both transistors
until the signal applied to the base 17 of transistor 11
Transistor ‘11 _______ -Q __________ __ 2N647(TA1620A)
Transistor 25
,
I
_
'
___p
transistor conductive.
Resistor 13 ____,.,.., _____ __v____,____,______ohms__
P150
Resistor 15 ______ ...'..___.: ____ __'_______ __do____ 2200
Resistor 19 ____ __,___ ________________ _'_,_.do;___ 6800 25
Resistor 21 ___ ____________ ___ _____ __,____do____
470
'Resistor 27 ____.,-_____ _________ ______,___do__.,__
Resistor 31 ____
_____ __,_____..________do_____
680
100
'10
Inasmuch as during normal standby operation trans
sistors' 11 and 25 are both non-conductive, the current
drain on the system supplying the circuit‘is at, a minimum,
Whenever a signal is applied to base 17 of the threshold
level, both transistors become conductive and continue
in a state of conduction as long as the signal on base 17
persists at threshold level. Immediately following the
termination of the signal at base 17 both transistors re
turn to their non-conductive state. It is unnecessary that
the currents in the two transistors be equal and in fact
whatever load is placed on transistor 25 has no, material
effect on the operation of transistor 11.
As the circuit shown in the accompanying drawing and
described in the foregoing speci?cation is but one pre—
ferred embodiment of the invention, it is intended that
it be construed in an illustrative sense as many modi?ca
tions will become apparent without departing
the
scope of the invention as de?ned in the appended claims.
‘In the claims:
‘
1. A threshold trigger circuit comprising a'pair of
transistors of opposite conductivity types connected in
circuit with a potential source to, normally apply cut off
bias potentials to electrodes of both transistors, coupling,
means from the collector of said one transistor to the
base of said other transistor effective upon conduction of
said one transistor for applying a potential to the base of
Resistor 33 _____ "p ____ __,.._____________'___do_,___ 1200
Capacitor 37 __-_____ _,____ _____ __microfarads___
1,0 30
Capacitor 38 ___., ___________ __,_, _______ “do-..
_
4. A threshold trigger circuit comprising a pair of
transistors of opposite conductivity types connected in
circuit with a potential source to normally apply cut off
bias potentials to electrodes of both transistors, coupling
,_ 2N2l7
Transistor 35 ______ -f ______________ _p-_,____ TA_1724
the other transistor opposing the cut oil bias potentials
applied to electrodes of said other'transistor, means for
applying a signal to the base of said one transistor, and
a regenerative feedback circuit between the emitters of
said transistors effective upon conduction of said other
transistor for applying a potential to the emitter of said
one transistor in opposition to the cut oif bias potentials
applied toelectrodes of said one transistor but insu?i
cient to render said one transistor conductive, in the ab
sence of a signal applied to its base.
5. A threshold trigger circuit comprising a pair 05 tran
sistors of opposite conductivity types connected in circuit
with a potential source to normally apply cut of? bias po
tentials to both transistors, coupling means from one tran
sistor to the other transistor effective upon conduction of
said one ‘transistor for applying a potential opposing the
bias potentials on the electrodes of said other transistor,
means for applying an alternating current signal to the
base of said one transistor for rendering said one transistor
conductive on alternate half-cycles of the signal, a capaci
tor connected between an electrode of said one transistor
and said coupling means to be charged by said conduction
50 of said, one transistor on alternate half-cycles of said signal
for applying the potential of the charge to said other
transistor in opposition to the bias potentials applied to
electrodes of said other transistor, and a regenerative
feedback circuit’ between electrodes of said transistors
means from one transistor to the other transistor effective 55 et‘r'ective'upon conduction of said other transistor for ap
plying a potential opposing the biaspotentials on the
upon conduction of said one transistor for applying po~
electrodes of said one transistor but insut?cient to. render
tentials opposing the bias, potentials on the electrodes of
said one transistor conductive in the absence of a signal.
said other transistor, means for applying a signal to die
6. A threshold trigger circuit comprising a, ?rst tran
base of said one transistor for initiating conduction of
said other transistor, and a regenerative feedback circuit 60 sistor of the NPN type having its electrodes connected
to a potential source to normally apply cut elf bias poten
between corresponding electrodes of said transistors e?ec
tials to electrodes of said ?rst transistor and including
tive upon conduction of, said other transistor for apply
a load resistor in the collector circuit, means for applying
ing potentials opposing the bias potentials on the elec
a_ signal to the base of said ?rst transistor, a second tran
trodes of said one transistor but insufficient to render
said one transistor conductive in the absence of a signal 65 sistor of the PNP type having its electrodes connected in
circuit with a potential source to normally apply cut off
applied to the base thereof.
bias potentials to electrodes of said second transistor and
2. A threshold trigger circuit comprising a pair of
including a resistor connected between said potential
transistors of opposite conductivity types, veach of said
source and the emitter of said second transistor, a cou
transistors having an input electrode, an output electrode
pling circuit between the collector of said ?rst transistor
and a third‘ electrode, respectively, means for applying
and the base of said second transistor for applying a po-v
cut-oil biasing potentials to the electrodes of said transis
tors, means connecting the output electrode of one of
tential to the base of said second transistor effective upon
conduction of said ?rst transistor for opposing the cut off
said transistors to the input electrode of the other of said
bias potentials applied to electrodes of said second tran
transistors, means for applying a signal to the input elec
trode of said one transistor for» initiating conduction of 75 sistor, and a regenerative feedback circuit connected be—
3,084,265
5
tween the emitter of said second transistor and the emitter
of said ?rst transistor elfective upon conduction 05 said
second transistor for applying a potential to the emitter
of the ?rst transistor opposing the cut ot‘I’ bias potentials
applied to electrodes of said ?rst transistor but insu?icient
to render said ?rst transistor conductive in the absence of
a signal applied to its base.
7. A threshold trigger circuit comprising a ?rst tran
sistor of the NPN type having its electrodes connected in
circuit with a potential source to normally apply cut o?
bias potentials to electrodes of said first transistor, means
for applying an alternating current signal to the base of
said ?rst transistor for rendering said ?rst transistor con
ductive on alternate half-cycles of said signal, a second
transistor of the PNP type connected in circuit with a
potential source to normally apply cut otf bias potentials
to electrodes of said second transistor, coupling means
between the collector of said ?rst transistor and the base
of said second transistor re?ective upon conduction of said
?rst transistor for applying a potential to the base of said
second transistor in opposition to the cut o? bias poten
tials applied to electrodes of said second transistor, a
regenerative feedback circuit between the emitter of said
second transistor and the emitter of said ?rst transistor
etfective upon conduction of said second transistor for
applying a potential to the emitter of said ?rst transistor
in opposition to the cut off bias potentials applied to elec
trodes of said ?rst transistor and condenser means pro
6
sisters 01'} opposite conductivity types, biasing means nor
mally rendering each of said transistors non-conductive
including a ?rst voltage divider having intermediate points
respectively connected to the emitter electrodes of the
transistors and a second voltage divider having an inter
mediate point connected to the base electrode of one of
said transistors, said biasing means establishing a thresh
old level for said one transistor, a direct connection be
tween the output electrode of said one transistor and the
input electrode of said other transistor, means ‘for apply
ing a signal to the base electrode of said one transistor,
and a regenerative feedback circuit between the emitter
electrodes of said transistors including a part of said ?rst
voltage divider between said intermediate points effective
15 to render both said transistors conductive when the signal
10
applied to the base electrode of said one transistor is above
the threshold level.
20
25
viding a low impedance alternating current path between
the collector and emitter of said ?rst transistor to be 30
charged by conduction of said ?rst transistor during alter
nate half-cycles of said signal for applying through said
coupling means a potential to the base of said second
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,759,104
2,798,160
2,840,727
2,843,743
2,843,762
2,853,633
2,858,456
2,905,815
2,971,134
Shellett _____________ _- Aug. 14,
Bruck ________________ __ July 2,
Guggi _______________ __ June 24,
Hamilton ____________ __ July 15,
Trent _______________ __ July 15,
McVey _____________ __ Sept. 23,
Royer _______________ __ Oct. 28,
Goodrich ____________ __ Sept. 22,
Cockrell ______________ __ Feb. 7,
1956
1957
1958
1958
1958
1958
1958
1959
1961
FOREIGN PATENTS
789,478
Great Britain _________ __ Jan. 22, 1958
OTHER REFERENCES
transistor for rendering said second transistor conductive
in opposition to bias potentials applied to electrodes of 35
Transistor Circuit Handbook, Garner, 1957 edition,
said second transistor.
published by Educational Book Co. Publishing Division
8. A threshold trigger circuit comprising a pair of tran
Coyne Electrical School.
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