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Патент USA US3026464

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March 20, 1962
F. E. GOODWIN
CURRENT DRIVING CIRCUIT
3,026,454
Filed Dec. 1, 1959
2 Sheets-Sheet l
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FRANCIS E. GOODWIN,
INVENTOR
BY
ATTORNEY
March 20, 1962-
F. E. GOODWIN
3,026,454
CURRENT DRIVING CIRCUIT
Filed Dec. 1, 1959
2 Sheets-Sheet 2
12a 5.
VOLTAGE
96
94
VOLTAGE
I02
92
I00
CURENT
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FRANCIS E. cooowm,
‘"0
‘
INVENTOR
‘s6 *54 ‘*sz ‘50
CURRENT AMPERES
ATTORNEY
United States "neat
‘5C6...
3,026,454
Patented Mar. 20, 1962
1
2
3,026,454
Francis E. Goodwin, Los Angeles, Calif, assignor to
loads that includes a driving transistor having‘ its load
current path coupled in series with the inductive load.
A regulating transistor has its load current path coupled
Hughes Aircraft Company, Culver City, Calif., a cor
poration of Delaware
Filed Dec. 1, 1959, Ser. No. 856,894
9 Claims. (Cl. 317--123)
during steady state conditions. The base of the regulat
ing transistor is coupled through a programming signal
I
CURRENT DRIVING CIRCUIT
across a power source through a protective diode for
applying a potential to the base of the driving transistor
generator to a point between a ?rst and a second resistor
This invention relates to current driving circuits and
connected between the power supply and the inductive
load. The programming signal generator responds to a
source of signals to develop switching signals having pre
particularly to a transistor current source for ferrite
phase shifters and other inductive loads.
An inductive element when being driven with a step
determined volta-ge levels corresponding to currents re
source of impedance R has a basic time constant L/R
quired through the inductive load. These voltage levels
for changing current through the inductive element
control the regulating transistor to maintain the desired
current through the inductive load during steady state
conditions and respond to a negative feedback signal
from the inductive load to maintain the regqilating tran
where L is the inductance of the element. For the time
constant of changing current through the inductive ele
ment to be small, either the inductance L must be small
or the effective resistance R must be large, or both.
sistor biased so that a constant current is maintained
The value of the inductance L may be ?xed by other
considerations such as when utilizing a ferrite phase
through the inductive load for each steady state or di
rect current voltage level of the switching signal. To
shifter where the L may be established at a ?xed value.
provide large voltage transients when the switching sig
One prior art means to drive ferrite phase shifters
' nals change voltage level, a transient ampli?er is coupled
in series between the signal generator and the base of
with a small time constant is to use high resistance
vacuum tubes as current drivers. However, this type of
the driving transistor for applying switching transients
driving arrangement requires a very large current and 25 signals to the base of the driving transistor and present
wastes a relatively large amount of power, especially if
ing a high impedance to the inductive load during switch
a large constant current is to be maintained through the
ing transients of a ?rst polarity. A diode is coupled in
inductance of the phase shifter for a long period of time.
series in the load current paths of the driving transistor
In circuit arrangements where a large number of phase
for providing a high impedance to the inductive load
shifters are utilized, the large power loss makes vacuum 30 during switching transients of a second polarity. The
tube drivers impractical.
switching transients of both polarities are applied to the
Another conventional driver for inductive loads such
inductive load to provide rapid changes of current there
through. Thus, the current driving circuit of this inven
as phase shifters is a current source utilizing power tran
sistors which will effectively hold a constant current in
de?nitely. However, the conventional transistor arrange
35
tion maintains a regulated steady state current through
the inductive load and during transient conditions, rapid
ment provides a source impedance of only a few ohms
ly changes the current through the load to a new value.
and the power source has a relatively small potential so
The novel features of this invention, as well as the
that a very large time constant is present when changing
invention itself, both as to its organization and method
the current through a phase shifter, for example. A con
of operation, will best be understood from the following
ventional regulated current source utilizing transistors 40 description, taken in conjunction with the accompany
may include a switching transistor coupled in series with
ing drawings, in which like characters refer to like parts,
the inductance and a transistor utilized as a regulating
ampli?er coupled between a ?rst and a second resistor
that are connected between the current source and the
' and in which:
FIG. 1 is a circuit diagram of the current driving cir
cuit in accordance with this invention;
inductance and the base of'the switching transistor. The 4:5
FIG. 2 is a graph of current versus phase for a phase
voltage rating of the power source and the relative size
shifter that may be utilized as the inductive load in
of the two resistors determines the current passed through
' FIG. 1;
the inductance.
FIG. 3 is a graph of voltage versus time showing a
A current source utilizing transistors that would pro
vide high voltages without destroying the transistors and
high impedances to reduce the time constant so as to
50
FIG. 4 is a graph of voltage versus time showing the
rapidly change from one current level through the in
transient and steady state volt-ages developed by the
ductance to another would be very valuable to the art.
It is thus an object of this invention to provide a cur
' rent source for inductive loads utilizing transistors ele
ments that is highly e?icient because of requiring a mini
mum amount of power.
representative sequence of voltages developed by the pro
gramming signal generator of FIG. 1.
transient ampli?er of FIG. 1 in response to the voltages
of FIG. 3;
55
FIG. 5 is a graph of current versus time for illustrat
ing the rapid change of current through the phase shifter
of FIG. 1.
It is a further object of this invention to provide an
Referring ?rst to FIG. 1 which shows a schematic
ef?cient current source for switching the current from
one level to another through an inductive load with a 60 diagram of the current driving circuit of this invention,
the arrangements of the elements therein will be described.
minimum of time delay.
A battery 10 having one end coupled to a ground lead
It is a still further object of this invention to provide
12 as a voltage reference and the other end coupled to
a source of driving current for shifting the phase of a
phase shifter element by rapidly changing the current to
a lead 14 is provided as a power source and may, for
example, develop +6 volts. The lead 14 applies power
a plurality of predetermined levels.
65 through a series connected ?rst resistor16 ‘and second
It is another object of this invention to provide an
resistor 18 and through a lead 19 to one end of an in
ef?cient current source for a phase shifter that utilizes
transistors and that utilizes switching transients for
changing current through the inductive load of the phase
ductive load or coil 20 of a phase shifter 22 that may
be utilized with the circuit of this invention. The phase
shifter 22 may include the coil 20 wound about a rec
shifter with a minimum of delay.
70 tangular waveguide (not shown) with an axially disposed
Brie?y, this invention is a current source for inductive
ferrite rod and an axial magnetic ?eld provided by the
3,026,454
3
4
sistor 86, thus passing only transient signals of short
solenoid. Suitable means are provided to prevent eddy
current losses in the Waveguide itself. A phase shifter
duration.
Referring now to FIG. 2 showing a graph of phase
versus current for the phase shifter 22, the operation of
November 195.7 issue of the IRE proceedings in an article
the circuit will be explained in further detail. A curve
by F.. Reggia and E. G. Spencer entitled “A New Tech
88, which may be determined experimentally vfor any se
niq-ue. in Ferrite Phase Shifting for Beam Scanning’ of
lected phase shifter 22 or any inductive load shows the
Microwave Antennas.”
~ .
required current through the inductance coil 20 for four
The other end of ‘the inductive load 2%} passes current
phase conditions of a microwave signal applied through ~
through the emitter to collector current path of a driver
transistor 24 which is of the p-n-p type. The collector IO a waveguide (not shown) of the phase shifter 22. Cur
rents i56, 1'54, 1'52 and im indicate the current required to be
of the transistor 24 isv coupled through the anode to
passed through, the phase shifter 22 to develop a phase
cathode path of a blocking diode 26 to the ground lead
shift of 0 degree, 120 degrees, 240 degrees and 360' de
12.
‘
I of ‘this general type is described on page 1510 of the
grees.
For steady state regulation of current through the in
Referring now to FIG. 1 and to FIG. 3, the latter of
ductive load 20, a regulating transistor 28 of the p-n-p 15
which shows the step voltage developed by the signal
type is provided. The emitter of the transistor 23 receives
generator 44,, to FIG. 4 which shows the transient sig
current from the lead 14 through the anode to cathode
nals developed by the transient ‘ampli?er 74 and to FIG.
path of a zener diode 3,0 for providing a constant voltage
5 which shows waveforms of the currents passed through
drop so that the regulating transistor 28 operates in a
the phase shifter 22, the operation of the circuit will be
desired ampli?cation range. The collector of the tran
further explained. The sequence of step or switching
sistor 28 is arranged to apply current to the ground lead
voltages of a waveform 90 in FIG. 3 is determined by the
12 through the anode to cathode path of a protective
amount of phase shift desired of the phase shifter 22.
diode 34 and‘ through a lead 36 and a signal developing
The voltages e50, e52, e54 and e56 of the waveform 90 are
resistor 38, The potential developed by the resistor 38 is
applied through a lead ‘40 to the base of the driving tran
25
developed. at. respective times tothrough A, by the contact
sistor 24 for controlling the current through the inductive
arm 48, respectively, moving in response to the scan
load 2.0..
motor 68 to contacts 50, 52, 54 and 56.
.
The base of the transistor 28.. is arranged to respond
'to the voltage developed by a programming signal gen
orator. 4.4 which includes a stepping switch ‘46 having an 30
arm 48 movable to form a closed circuit with contacts
59, 52, 54 and 56. A precision resistor 58 is provided
with tapped points, connected to the contacts 50, 52, 54
and 56 to provide different potential levels. ‘One end
of the resistor 5,8 isv coupled to the positive terminal of 35
a battery 62. through a lead 64. and the other end of
theresistor 5,8 is biased from the other end of the battery
62. The battery 62 may be selected to develop +2 volts.
‘
Before explaining the transient signals. developed when
the switching voltages of FIG. 3 change voltage level,
the steady state regulating operation of the, circuit will be
explained. Each, switching voltage ‘level of the wave
form 90 such as the voltage 650 is applied to the base of
the transistor 28 to ‘bias the transistor 28 to pass a pre
determined current from its emitter- to collector and
through the diode, 34 and the signal forming resistor 38.
In response to each, voltage level of the: waveform 90, a
predetermined voltage is developed on the lead 40 to
establish‘ a desired current through the emitter to the col
lectoIT of the driver transistor 24. Thus,v in. response to
The lead. 64 is biased from a point ‘between the resistors
16-, and 18 so that a change of current through the load 40 each higher Voltage level e50, e52, e54 or 656 of the wave
effectively provides a negative feedback signal from the
form 90,, the impedance through the'driver transistor 24
inductive load 20.
is increased. and the, current through theinductive load 20
is decreased to the respective currents 1'50, i52, 1'54 or 1'56
as indicated by the waveform 88 of FIG. 2.
The, arm 48 of the stepping. switch 46, is responsive
through a mechanical connection 66 to the- state of rota
In order to maintain a desired current level such as
tion of a scan motor 63 for example. Thus, the arm 45
[50 through the inductivev load 20‘, to overcome variations
48 may sequentially move, for example, from the con
tacts 50, 52, 54, 56v and back to the contact 50‘.
The
of the Source. of potential such as the battery 10, and
variations of. the characteristics. of the elements in the
scan motor 68, may include an intermittent gear arrange
circuit such as. by, temperature changes, a negative feed:
ment such as a‘ rocket drive that allows. the movement
to occur, rapidly from one contact to another after a 50 back, arrangement is also. provided. The size of the re
sistors 16 and 18v is designed so that for each voltage level
of thewaveform 90 a predeterminedvoltage is developed
on the lead 64, soithat the desired current is supplied to
the inductive load 20. In order to maintain this current,
provided by the signal generator 64.. By connecting the 55 a change, of current through the resistors 16 and 18 is
reflected as a change of. voltage. through the resistor 58
contacts such as 50 to different tapping points of the
and‘ on the base, of the transistor 28-. Thus, the poten
resistor 58, any desired sequence may be developed.
tial" on the lead 40-is changed to correct the impedance
The signal applied to the arm 48. is. in turn applied
of the transistor 24 so as to maintain the: desired cur
through a lead/70 to the base of the transistor 28 and to
an ampli?er 72 of a transient ampli?er 74. The ampli?er. 60 rent through the inductive load 20. For example, a
decrease of current through the inductive loadv 20' causes
predetermined amount of rotation of the motor. It is
to be noted that the continuous ‘sequence; from a higher
voltage to decreasing voltage levels then back to the
higher voltage level is only one sequence that may be
72 may be either an A.C. (alternating current) or a DC.
an increase of potential onthe lead 64 and a resultant
(direct current) ampli?er. The D.C. ampli?er 72v ap
increase of potential on the base of the. transistor 28.
pliesan ampli?ed signal through a lead 76 to a high pass
Thus, the current through the resistor 38. decreases with
?lter 78 also included in the transient ampli?er 74. The 65 a consequent potential drop on the lead 40. The driver
high pass ?lter 78 applies only a transient signal to the
transistor 24 decreases its e?ective. impedance and in
lead 40 in response to. a change of voltage level of the
creases the current ?ow through the inductive load 29
switching signal developed by the signal generator 44, as
to correct the original decrease of current. The circuit
will be explained subsequently.
The high pass ?lter 78 may be any conventional type
of ?lter and may include a capacitor 80 having one end
coupled to the lead 76 and the other end coupled to
ground through a resistor 82 and to one end of a second
operates in a ‘similar but opposite manner in response to
an increase of current through the inductive load 20 from
any selected current level such as the current i5o. Thus,
a negative feedback arrangement is provided to continu
ally regulate the current through the phase shifter 22 to
any selected value.
capacitor 84, The other end of the second capacitor
Referring now primarily to FIGS. 1, 3 and 5,‘ the
34 is coupled to thelead 40>and> to groundthrough a re 75
3,026,454
6
transient operation of the circuit in accordance with
this invention will be explained. When the voltage level
of the switching signal of the waveform 90 changes such
to the emitter of the driver transistor 24. Thus, cur
rent is rapidly increased through the inductive load 20
from the current level i56 to the new current level i5o. The
high impedance of the diode 26 and the negative transient
signal applied to the inductive load 20‘ develops a large
effective impedance so that the time constant is very
small for the required current change. Similar to the
as at times to to L, as a result of the contact arm 48 mov
ing to a di?erent contact 50 through 56, a transient sig
nal is applied through the lead 70 to the ampli?er 72 of
the transient ampli?er circuit 74. This transient signal
is ampli?ed in the ampli?er 72 to form signals similar
positive transient signal, the negative transient signal has
to transient signals 92, 94, 9'6, 98 and 100' of a waveform
a short time duration so that the current is only changed
102 of FIG. 4. The ampli?er transient signals similar 10 to the desired. higher current level is‘).
to the signal 94 are applied to the high pass ?lter 78 and
The negative switching transient appears equally on
passed therethrough as current signals to the lead 40.
the emitter, base and collector of the driver transistor 24
The high pass ?lter 78 only passes current signals there
so that the voltage rating is not exceeded. Also, because
through during the time of occurrence of the transient sig
the diode 26 is biased out of conduction current is pre
nals such as 94, acting to block all signalsduring steady 15 vented from passing through the driver transistor 24 to
state conditions. The current associated with the transient
exceed its power rating. Although the negative transient
signals such as 94 passes through the lead 4%)‘ and the
signal such as 100 causes a relatively large current flow
resistor 38 to develop the transient voltage signals 92, M,
through the transistor 2% for a short period of time, the
96, 98 or 100 on the lead v40. It is to be again noted
current is limited by the resistor 38‘ so that the power
that the transient signals such as 94 have a relatively 20 rating of the transistor 28 is not exceeded. Thus, the
short time of duration.
transistor elements in the circuit are protected from over
The elfect of a positive transient signal such as 94,
load and damage.
96 or 98 resulting from an increase in voltage level of the
It is to be noted that regardless of the sequence of
switching voltage of the waveform 947 of FIG. will now
voltages developed by the signal generator 44, the tran
be explained. The positive transient signal such as 94 25 sients act to rapidly change the current through the induc
applied to the lead 40 rapidly biases the transistor 24 into
tive load 2!’) to different current levels and the regulating
a nonconductive state to uncouple the inductive load 29
portion ‘of the circuit maintains the steady state current
from the ground lead 12. Further, the positive potential
therethroug-h further corrected by the negative feedback
of the switching transient such as 94 is applied to- the
emitter of the transistor 24 and to the end of the induc
arrangement.
changes may he made in large inductive loads at a very
rapid rate. It has been found that the circuit in accord
ance with this invention has reduced the rise time of phase
shifter current from 300 microseconds to 10 microseconds
utilizing a maximum transient voltage of 60 volts. If the
transistors are able to withstand higher voltage and power
ratings or if means are utilized to protect the transistors,
transient voltages as high as 500 volts may be utilized,
thereto so that the current level £50 decreases in a short
period of time to a current level of i52. Because of the
short time interval of the transient signal such as 94, the
current only decreases to the level in rather than to a low
er current level and then the transient signal is terminated
allowing the normal regulating action of the circuit to
maintain the current level i52. Thus, only transient sig
nals of short duration are effectively passed through the
high pass ?lter 78.
Without the transient ampli?er arrangement in ac
cordance with this invention, the characteristic de
lay in changing current through an inductive element
Because of the short time duration and
large amplitude of the transient signals, large current
tive load 20 coupled thereto. This positive transient sig
nal 94 rapidly decreases the current through the induc
tive load 20 by effectively presenting a high impedance
thus providing current changes in a period as short as 2
40
microseconds.
Although the programming signal generator 44 respond
ing to the scan motor 68 has been shown as providing the
switching signals, it is to be understood that other means
may be utilized for developing the switching signals of the
waveform 90. For example, digital techniques may be
would cause the current to change to the new level as 45 utilized with a rotating memory drum containing binary
indicated by a dotted waveform 1016.
Thus, the cur
rent driver of this invention allows the phase developed
by the phase shifter 22 to be rapidly changed without an
numbers stored thereon in a sequence indicative of the de
sired sequence of voltage levels of the waveform 90.
Read heads and ampli?ers may develop digital signals as
extensive time delay. It is to be noted that without the
the memory drum rotates that are then passed through a
transient ampli?er circuit 74 or" this invention, a current 50 digital to analogue converter to convert the binary nun driver is limited to a voltage for effectively causing the
hers to volt-age levels such as indicated by the waveform
change of current no greater than the power source or
90 of FIG. 3. Binary storage arrangements of this type
battery ‘10. The driver transistor 24 is not damaged by
are well known in the computer art and will not be ex~
exceeding its power limitations because it is biased out
plained in further detail.
of conduction during the presence of the positive transient
Thus, there has been described a current driving circuit
signal. It is to be noted that the driver transistor 24
that includes a regulating means having a negative feed
must be selected so that the voltage of the transient signal
back arrangement for providing a preselected steady state
does not exceed its characteristic voltage limit. At the
current to a load. During the presence of switching
same time, the positive transient signal such ‘as 94 is im
transients when changing the current through the induct
pressed on the cathode of the diode 34 biasing it out of 60 ance, a transient ampli?er arrangement is provided to
conduction. Thus, the regulating transistor 28 is pro
develop transient signals for ef?ciently increasing the re
tected from current passing in a direction opposite to its
sistance in the circuit during a very short period. Thus,
emitter to collector path and exceeding the power rating
current is rapidly changed through the inductance. This
of the transistor 28.
circuit is very useful, for example, for driving one or a
The operation of the circuit in response to a negative 65 plurality of ferrite phase shifters such as may be utilized
switching transient signal such as 100 will now be ex
plained. A negative transient signal such as 100 biases
the driver transistor 24 in a conductive state so as to act
in radar scanning.
What is claimed is:
1. A circuit for driving current through an inductive
load comprising a power source, driver means coupled in
as a closed circuit. However, the negative transient sig
nal is impressed on the anode of the diode 26 biasing it 70 series with said inductive load, regulating means coupled
across said power source and to said driver means for
out of conduction and de-coupling the inductive load 20
controlling the current therethrough, a source of switch
from the ground lead 12. At the same time, the negative
ing signals of changing voltage levels coupled to said regu
transient signal such as 100 is impressed through the
lating means for maintaining a selected steady state cur
transistor 24 to the end of the inductive load 20 connected
75 rent through said inductive'load, and transient ampli?er
3,026,454
7
means coupled between said source of switching signals
and said driver means for responding to the changes of
voltagelevels of said switching signals to develop transient
signals to control said driver means, said transient signals
8
5. A. circuit for supplying‘ steady state current through
an inductive load at selected current levels and for -
rapidly changing the‘ current. levels from one to another
through the load comprising. a source of potential coupled
across said load, variable impedance means coupled in
series with said load and having a control terminal, a
diode coupled between said variable impedance means
and said source of potential, regulating means and signal
2. A current driving circuit for a load comprising a
forming means coupled in series across said source of
power source coupled across the load, ?rst variable im
pedance means and a unilateral conductive device cou 10 potential, said regulating means having a control ter
minal, said signal forming means coupled to the control
' pled in series with said load and said power supply, said
terminal of said variable impedance means for maintain
?rst variable impedance means having a control terminal,
ing said selected current levels through said load, pro
second variable impedance means coupled across said
gramming means for developing switching signals having '
power supply and having a control terminal, a signal forming resistor coupled in series with said second variable 15 a sequence of voltages at selected levels indicative of
said selected current levels and coupled to the control
‘ impedance means and to the control terminal of said ?rst
terminal of said signal forming means, and transient am
variable impedance means for developing signals to con
pli?er means coupled between said programming means
trol‘ the current through said load, programming means
and said signal forming means for developing and apply
for developing switching signals having desired voltage
ing transient signals to said load at the time when the
levels indicative of desired current levels through said
selected voltage levels of said switching signals change so
I load and coupled to the control terminal of said second
as to change the current» levels through said- load in a
variable impedance means, and transient ampli?er means
being applied through said driver means to» said inductive
load to rapidly change the current through said inductive
load.
'
I
t
short period of time.
'
coupled between said programming means and said sig
6. A circuit for supplying current through‘ an inductive
nal forming resistor to‘ develop. transient signals to rapidly
25 load at a plurality of selected current levels and for
change the current levels through said load.
3. A current driving circuit for an inductance compris
ing a power source coupled across said inductance, a
driver transistor having a control electrode and a load
path- coupled in series with said inductance, a regulating
transistor having a control electrode and a load path
acoupled across said power source, a signal forming re
sistor coupled in Series with the load current path of
said regulating transistor, said load current path coupled
rapidly changing from one current level to another com
prising a power source having ?rst and second terminals,
variable impedance means having a control terminal and
having a load path coupled between said load and- the
?rst terminal of said power source, unilateral means
coupled in said load path between said- variable im--'
pedance means and the ?rst terminal of said power‘source,
current regulating means having a control terminal and
having a load path coupled between the ?rst and second
to the control electrode of said driver transistor, signal
‘generator means for developing switching signals of pre 35 terminals of said power source, signal forming means
coupled in the load path of said regulating means and to
determined different‘ voltage levels, said generator means
the control terminal of- said variable impedance means,
coupled to the control electrode of said regulating tran
programming means for developing switching signals hav
si'stor for maintaining a current through said inductance
ing a, plurality of predetermined levels of voltages and
in response to the steady state portions of the switching
signals, and transient ampli?er means coupled to said 40 coupled to said control terminal of said regulating means,
‘said regulating means controlling the current through said
generator means and to the control electrode of said
load in response to steady state portion of said' switching
driver transistor for rapidly changing current through said
signals, and transient ampli?er means coupled between
inductance in response‘ to‘ the transient portions of said
said programming’ means and said signal form-ing means
‘
4. A current driving circuit comprising a ?rst source 45 for applying transient signals to‘ said‘ lead for‘ rapidly
changing the current levels therethrough in response to
of potential having a positive and a negative terminal, an
the changes in voltage levels of said switching signals.
inductive load, a ?rst and a second resistor coupled in
switching signals.
7. A circuit for driving current through an inductance
seriesv between the positive terminal of said ?rst source
comprising a power source having‘ a positive and nega-'
of potential and said inductive load, a driver transistor
having‘ a control electrode and having a load path coupled 50 tive terminal, a ?rst transistor having base, an emitter
and collector with the emitter coupled to a ?rst end? of
between said inductive load and said negative terminal of
said inductance, a ?rst diode having ‘an anode coupled‘
said ?rst source of potential, a diode coupled in the load
to the collector of said ?rst transistor and‘ a cathode
current path of said driver transistorbetween said driver
coupled to the negative terminal of said power source, a
transistor and the negative terminal of said ?rst source
of potential, a regulating transistor having a control ter 55 ?rst resistor having a ?rst" end coupled to a second end
of said inductance, a second resistor having a ?rst end‘
minal and having a load path coupled between the posi
coupled to a second'end of said ?rst resistor and having a
tive and, negative terminals of said ?rst source of potential,
second end coupled to the positive terminal of said- power ,
asignal forming resistor coupled in the load path of said
regulating transistor between said regulating transistor
source, a second transistor having a base, an emitter and
and the negative terminal of said ?rst source of potential, 60 a collector, a zener diode‘ coupled‘ between the emitter
of said second transistor and said positive terminal of
said signal forming resistor also coupled to the control
terminal of said‘ driver transistor, a second source of
said power source, a second diode having an anode and a
cathode with the anode coupled to the collector of said
second transistor, a third resistor having a; ?rst end
coupled to the cathode of said second‘ diode and. to the
minal of said second source of potential and with the
base of said ?rst transistor, and having‘ a second end
positive'terminal of said second source of potential cou
coupled to the negative terminal of‘ said power source, a,
pled to a point between said ?rst and second resistors, a
source of biasing potential having a positive and a nega
stepping switch including a plurality of contacts coupled
tive terminal, a vfourth resistor having one end, coupled
to said tapped resistor and a movable arm for contacting
said contacts‘ coupled to the control electrode of said 70 to said negative terminal of said source of biasing po
tential and having the other end coupled to the positive
reguilating transistor, means for moving said contact arm
terminal of said source of biasing’ potential and to‘ the
of. said stepping switch, an ampli?er coupled to said
second
end of said ?rst resistor, a plurality of tapping’
movable arm of'said stepping switch, and a high pass ?lter
terminals coupled to said. fourth resistor, a movable arm
coupled between said ampli?er and said signal forming
75 vfor contacting; only one: of said tappingv terminals at a
resistor..
potential having a positive and negative terminal, a tapped
resistor coupled between the positive and negative ter
3,026,454
time and coupled to the base of said second transistor,
means coupled to said movable arm for controlling said
arm to contact a desired sequence of said tapping ter
minals, an ampli?er coupled to said movable arm, and a
high pass ?lter coupled to said ampli?er and to the ?rst
end of said third resistor.
10
ing a power source, a ?rst transistor having a load path
and a control terminal with said load path coupled be
tween a ?rst end of said load and the negative terminal
of said power source, a ?rst diode coupled in series in the
load current path of said ?rst transistor between said
?rst transistor and the negative terminal of said power
8. A current driving circuit for an inductance com
prising a power source having a positive and negative
source, current sensitive means coupled between a second
to the negative terminal of said power source, a ?rst
resistor having a ?rst end coupled to a second end of said
said second transistor, impedance means coupled between
end of said load and the positive terminal of said power
terminal, a ?rst transistor having base, an emitter and
source,
a second transistor having a control terminal and
collector with the emitter coupled to a ?rst end of said 10
a ?rst and a second load terminal, a potential source
inductance, a ?rst diode having an anode coupled to the
coupled to the ?rst load terminal of said second transistor,
collector of said ?rst transistor and a cathode coupled
a second diode coupled to the second load terminal of
inductance, a second resistor having a ?rst end coupled 15 said second diode and the negative terminal of said power
source to form ‘a current path, said base of said ?rst
to a second end of said ?rst resistor and having a second
transistor
coupled in said current path between said second
end coupled to the positive terminal of said power source,
diode and said impedance means, programming means
a second transistor having a base, an emitter and a col
coupled to said current sensitive means for responding to
lector, a zener diode coupled between the emitter of said
current changes therethrough, said programming means
second transistor and said positive terminal of said power
developing a switching signal having a plurality of desired
source, a second diode having an anode and a cathode
voltage levels each indicative of a desired current level
with the anode coupled-t0 the collector of said second
through said load, said switching signals having steady
transistor, a third resistor having a ?rst end coupled to
state
and transient portions, said programming means
the cathode of said second diode and to the base of said
?rst transistor, and having a second end coupled to the 25 coupled to the control terminal of said second transistor
negative terminal of said power source, a source of bias
ing potential having a positiveland a negative terminal,
programming means coupled to the second end of said
?rst resistor and to the base of said second transistor for
developing switching signals having selected voltage levels
for controlling current therethrough for applying signals
to said control terminal of said ?rst transistor to maintain
said desired current levels through said load as deter
mined by the steady state portions of said switching sig~
nal, an ampli?er coupled to said programming means,
30 and a high pass ?lter coupled to said ampli?er and to said
indicative of a desired current level through said load,
current path between said impedance means and said
said switching signals including direct current and tran
second diode for passing current therethrough in response
sient portions and a transient ampli?er coupled between
to the transient portions of said switching signal to develop
said programming means and said third resistor, whereby
said second transistor is controlled to develop signals to 35 transient signals for changing the current level through
said load in a short period of time.
control said ?rst transistor during the direct current por
tions of said switching signals and said transient ampli?er
References Cited in the ?le of this patent
is controlled to develop signals to control said ?rst tran
sistor and to apply potentials to said inductance so that
UNITED STATES PATENTS
said current levels through said inductance change from 40
one to another in a short period of time.
9. A circuit for driving current through a load compris
2,931,952
2,941,125
Vinding _______________ __ Apr. 5, 1960
Lippincott ____________ __ June 14, 1960
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