US2752487A

US2752487A - Pulse generating circuits

Info

Publication number: US2752487A
Application number: US183581A
Authority: US
Inventors: Vore Henry B De
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-09-07
Filing date: 1950-09-07
Publication date: 1956-06-26
Anticipated expiration: 1973-06-26

Description

June 26, 1956 H. B. DE VORE 2,752,487

PULSE GENERATING CIRCUITS Filed Sept. 7, 1950 9 Val 7:465 PUWFRJUPPZY 22 2.5K- V.

a! was Pew/914:2 10/?) I Hunk/v7 I ATTORNEY United States Patent" 2 ,7'5i,48'7 PULSE GENERATING emeulrs Henfy B, De Vere, flare Meade, assignor to lt adio Corporation of America, a corporation of'Dlaware Ap'plifiafidn September 7,195'0', Serial N62"'1 83,'5 8 1 means; (of; i56 27 sifi i v va'ls betweenpiilses1 n I I It is comparatively si -le to" generate negative voltage- P i i. l e a v t afik i -a. 'wrtimr tlanq load. convenient method, employs a vacuum discharge th three or more elements. Thejload is placed ode circuit; the? cathode is effectively grounded; H .control" 'ler'nent is' biased negatively to or beyond on v if thequie'sjcen'tsta'te, Then comparatively small positive voltage pulse drives'the co rftrol elementsulficiently to cause the tube' t6 conduct, whereuponthe-anode current, flowing through the anode load-impedance, develo'ps ai'l'a'r'ge' negat ve voltageipulse, I I

when a positive voltage pulse is required, there are two V f d L I n one case, a ga iye voltage pulse is deye opedin a manner suchas" describedhereinbefore,- and.this pulse is-fed through ap'olarity r ers'ing pulse transformer ofappropriatedesign. This line transformer that permit of both rapid'voltage riseat the sartof the pulse and a sustained voltage amplitude: sinillfdroop) duringthe pplsetirne, The second method is similar to that described for negativepulse generation, In this case, however, the controlrelerne nt is maintainedsubstantially at cathode potential during the quiescent state between pulses. The pulse is'-then gener ate'd applying a' comparatively small =11egative pulsef to the control element, cutting off the current flow armeload, since the rise-occurswith a time: constant'that is" the product of this resistance" and the: associated circuit 'gu r ed thijs smallload resistor will necessarily coil"- sunie a large amount of power during thequiesceiit period; this power being; given-by the equation P= V lR where I voltage drop acrossthe? load resistor iii" the quiescentstate, This voltage (V) will beat leasta's' great as the pulse voltage.

Briefly, the present invention consists-of two vacuuni k fi t st s ts is, Se es; ith: ac t andl with a resistor therebetween, the two tubes being connectedacrbss terminals of voltage po wensupply; The; re=- sis tor between the two tubes furnishes a negative bias potential to e gridjof the, pqwei tube. (the t ube nearer tuhe (thethbb nearer 'th gr voltage' p ower supply) is oif by' 'a a N 7 pulse; the current th'r'oii'ghthe resistor'betwen th tiibes" v d issat isfactory for very short-pulses butif a long' pulse is desired, it becomesimpossible to designa acitaiices. However, when a large: voltage: pulse: is"

" ice 2-v stopsand the potential of; the grid of the power tub'e rapidly rises to the potential of its cathode and the pedah'ce of thepower tube rapidly decreasesto every small value. The potential of the cathode of the'po'wer tube thereby rapidly rises and approaches the potential of the positive side of the voltage power supply. This voltage of the cathode of the power tube is coupled to a: load circuit by a capacitor;

Two embodimentsof the invention are disclosed. In one embodiment; the resistor is of the conventional re sistance type and in the other embodiment the resistorbetween the control and the power tube isthe combination of a conventional resistor and a vacuum' tube referred to as a biastube, The control tube end of ther sistbr is connected to the grid of the bias tube and the other end of the'resis tor is connected to the cathode of the" bias tube and to the grid ofthe power tube;

There is thus provided a very high impedance through the power tube during the quiescent stateof the circuit;- that is, between pulses,an'd'avery low impedance-through the power tube during pulses.- The circuit, therefore, operates with high economy of power. I

F.urther-more,- astheimpedance through the power tube during pulses-is of very low value, the'time constant at the circuit is very' low andthe voltagerise rate is high Inprac'tice, a rate of voltage rise as high as 5X 10 volts per second has been obtained with a loa'd of LOOOohms.

It is known inthe art that two vacuum tubes may be connected in' series with a' resistor therebetwee'n, the re: sis tor providing a control voltage for one of the tubes.- Eor examples, seeArtzt Patent No. 2,310,342 and Blifz Patent No. 2,438,960 This arrangement" of tubes was used inbalancedamplifiersandreqiiired, for their (spare tion, two equalresistors in series across-the voltage power supply in order toestablish areference riiid volta'ge' foint between the) terminalsof a fluctuating voltage power supply. 'Ihisreference midvoltage point served as one terminal of the output circuit; Also, fo'r operation, a

resistance is used between one'tube and the positive side;

o f the-voltage power supply'which'bears a functional relation tothe resistance of the two equal resistors across' the' voltage'power supply. The pr'seritinvention is devoid of these interrelated resistors and their relation to the niiilvoltage point in the voltage power supply.

The principal object ofthe invention is to" provide an: improved circuit for generating? high positive voltage: pulses in which a vacunmtube; functioning'as a-plateloadi for a second vacuum tube, presents a high impedance be tween pulses antl alow impedance during pulses.

Another object of the invention is to" provide such a;

circuitthat produces a high rate of voltage rise. Another object of theinvention isto" provide such a' circuit in which the high-positive voltage'may be sustained over apulse of long duration&

Further objects and advantages of the invention will be apparent from the following description" made with" reference to the accompanying drawings in which:

Figure l is ascheniati'c diagram'of one embodiment-er;

the inventionin Whicha conventionalresistor is connected between the control tube and the powertiibe;

Eigure 2' is -a-s'chematic diagram of ahbthe'rehibodihient of the invention in which a conventional resistor and a: bias" Referring'to Figured; 1 is a vacuum mue-fia'viaganode may be noted that the cathode of tube 1 is connected substantially to ground because of the small impedance of resistor 6. This resistor is only for the purpose of providing bias to reduce anode current flow between applied pulses and for some tube type preferably is omitted. Grid 3 is grounded through resistor 7. Capacitor 8 provides the coupling of tube 1 to a driving source, applied at terminals 9, furnishing a negative voltage pulse of the desired width. Tube 1 is designated a control tube.

Vacuum tube 10, having an anode 11, grid 12 and cathode 13, is connected in series with tube 1 through resistor 14, that is, cathode 13 of tube 10 is connected to one end of resistor 14 and anode 2 of tube 1 is connected to the other end of resistor 14. The anode 11 of tube 10 is connected to the positive side of the voltage power supply at 15. The end of resistor 14 nearer tube 1 is connected to grid 12 of tube 10.

The voltage of the generated pulse is available at cathode 13 of tube 10 and is applied to a load circuit, repre sented by resistor 16, through coupling capacitor 17. Tube 10 is designated a power tube.

In the quiescent state, tube 1 is conducting. The current through tube 1 passes through tube 11 and resistor 14 and develops a difierence in potential across resistor 14. This difference of potential is applied between grid 12 and cathode 13 of tube 10 by connecting the end of the resistor nearer tube 1 to grid 12. The potential thus applied to grid 12 limits the flow of current through tube 10 to a very small value and causes most of the voltage drop between the anode supply connection 15 and ground to occur within tube 10. Cathode 13 in tube 10 is, therefore, maintained at a low potential.

When a negative voltage pulse is applied to grid 3 in tube 1, tube 1 is cut oil and no current will flow through resistor 14. The potential on grid 12 in tube 10 thereupon rises quickly to the potential of cathode 13 of tube 10. Tube 10 then can pass large currents and hence the potential of cathode 13 and also grid 12 rapidly rise toward the supply voltage at anode 11 of tube 10.

The pulse voltage rise rate is very rapid as this rate is determined by the capacitance of the load circuit and the very low internal impedance of tube 11 It is apparent that the power consumed between pulses is comparatively low as the internal impedance of tube 10 is very high when its grid 12 is biased negatively with respect to its cathode 13.

In testing the circuit in Figure 1, it was found that the rate of voltage rise at the start of the pulse is determined by the magnitude of the resistance in resistor 14 and the internal capacitance between grid 12 and anode 11 and cathode 13. The effect of resistor 14 and the internal capacitance of the tube could not be decreased indefinitely, except by reducing the value of the resistance of re sistor 14. However, with this decrease in resistance of resistor 14, the currents flowing during the quiescent state became larger. Accordingly, there is substituted for resistor 14 the combination of a resistor and a bias tube, the circuits of which are set forth in Figure 2.

Referring to Figure 2, the circuits of the control tube 1 are the same as in Figure 1. In Figure 2, one end of resistor 14 is connected to the anode 2 of tube 1 and to the grid 18 of a bias vacuum tube 19. The other end of resistor 14 is connected to cathode 20 of tube 19 and to the grid 12 of tube 10. Anode 21 of tube 19 is connected to the cathode 13 of tube 10. Anode 11 of tube 10 is connected at 15 to the positive side of a voltage power supply.

The voltage of the generated pulse is available at the cathode 13 of tube 10 and is applied to a load circuit, represented by resistor 16, through coupling capacitor 17.

The operation of the circuits in Figure 2 is substantially the same as the circuits in Figure 1, except that the currents flowing in resistor 14, when the control tube 1 is conducting, create a diiference of potential across the grid 18 and cathode 20 of the bias tube 19 and the tube i 19 becomes a high impedance cathode resistance for tube 10. As the cathode 13 of tube 10 is connected to the anode 21 of tube 19, and as the cathode 20 of tube 19 is connected to grid 12 of tube 19, the potential between grid 12 and cathode 13 of tube 10 is proportional to the internal impedance of tube 19. Hence the internal impedance of tube 10 is correspondingly high.

The rate of voltage rise at the start of a pulse in the circuits in Figure 2 is greater than that in the circuits in Figure l as the potential across the bias tube 19 is never very large and hence its cut-off bias is correspondingly low, which permits a small value of cathode resistance 14. The limitation to the rate of voltage rise in the circuit in Figure 2 is determined by a time constant which is the product of the resistance 14 by the capacitance between grid 1$ and the other elements of tube 19. Since resistor 14 can be much smaller than in the case of the circuit in Figure 1, this time constant can be made much smaller and hence the rate of voltage rise much greater.

In some cases, such as when increased voltage sensitivity is desired, tetrodes or pentodes may be used rather than the triodes in Figures 1 and 2. In Figure 3 are the circuits using two 4E27 tubes in parallel, a 829B tube both sections in parallel, and a 807 tube. Suitable values of the resistances and capacitances in ohms and microfarads are given in Figure 3 for such a combination of tubes, merely by way of example. With the given values of the various elements of the circuit and the operations described hereinbefore of the circuits in Figures 1 and 2, the operation of the circuits in Figure 3 will be obvious to those skilled in the art.

What I claim as my invention is:

l. A circuit for producing positive voltage pulses comprising a power tube having a cathode, an anode and a control grid, a control tube having a cathode, an anode and a control grid, the cathode of the power tube being connected to the anode of the control tube through an impedance device, the control grid of the power tube being connected through a direct current connection to the anode end of said device, the cathode of the control tube being connected substantially directly to ground, in operation a direct current voltage being connected between the anode of the power tube and the cathode of the control tube in the direction to put positive voltage on the anode of the power tube and in operation the only current flowing through said impedance device being current flowing through said power tube, said current acting to provide the sole biasing voltage applied to the control grid of said power tube, and means provided to capacitively connect a load between the cathode of the power tube and ground whereby a positive voltage pulse is supplied from the power tube cathode to said load in response to the application of a negative voltage pulse to the control grid of said control tube.

2. A circuit for producing positive voltage pulses comprising a power tube having a cathode, an anode and a control grid, a control tube having a cathode, an anode and a control grid, the cathode of the power tube being connected to the anode of the control tube through a resistor, the control grid of the power tube being connected through a direct current connection to the anode end of said resistor, the cathode of the control tube being connected substantially directly to ground, in operation a direct current voltage being connected between the anode of the power tube and the cathode of the control tube in the direction to put positive voltage on the anode of the power tube and in operation the only current flowing through said impedance device being current flowing through said power tube, said current acting to provide the sole biasing voltage applied to the control grid of said power tube, and means provided to capacitively connect a load between the cathode of the power tube and ground whereby a positive voltage pulse is supplied from the power tube cathode to said load in response to: the application of a negative voltage pulse toithe. control grid. of said. control tube;

3". A circuit for producing. positive: electrical pulses comprising: a power tube having a cathode, as time and a control grid, a. control. tube havirig' a catlibdaan anode and a control grid,:a-. bias tube having a cathode, an anode and aco a 'g'rid, s a id tub'es being connected together" incathode to aiibde r latioiiwliereby lth rhea;- cathode impedances of said tubes are'ifi s'eiiesrelation; an impedance device of comparatively small impedance connecting the cathode of said bias tube to the anode of said control tube, the control grid of said bias tube being connected to the anode end of said impedance device, the control grid of said power tube being connected to the cathode end of said impedance device, in operation a direct current operating voltage being applied between the anode of said power tube and the cathode of said control tube in the direction to put positive voltage on the anode of the power tube and means for taking a positive voltage pulse from the cathode of said power tube in response to the application of a negative voltage pulse to the control grid of said control tube.

4. A circuit for producing positive electrical pulses comprising a power tube having a cathode, an anode and a control grid, a control tube having a cathode, an anode and a control grid, a bias tube having a cathode, an anode and a control grid, said tubes being connected together in cathode to anode relation whereby the anodecathode impedances of said tubes are in series relation, a resistor of comparatively small impedance connecting the cathode of said bias tube to the anode of said control tube, the control grid of said bias tube being connected to the anode end of said resistor, the control grid of said power tube being connected to the cathode end of said resistor, in operation a direct current operating voltage being applied between the anode of said power tube and the cathode of said control tube in the direction to put positive voltage on the anode of the power tube and means for taking a positive voltage pulse from the cathode of said power tube in response to the application of a negative voltage pulse to the control grid of said control tube.

5. In combination: a control tube, a power tube and a bias tube, each of said tubes having, respectively, an anode, a cathode and a grid; a source of negative voltage pulses connected to said control tube; a voltage power supply, the positive side of which is connected to the anode of said power tube and the negative side of which is connected to the cathode of said control tube; an output pulse load connected to said power tube, and a resistor connected at one of its ends to the anode of said control tube and to the grid of said bias tube and at the other of its ends to the grid of the said power tube and the cathode of the said bias tube.

6. In combination: a control tube, a power tube and a bias tube, each of said tubes having, respectively, an anode, a cathode and a grid; a source of negative voltage pulses connected to said control tube; a voltage power supply the positive side of which is connected to said power tube and the negative side of which is connected to the cathode of said control tube; and output pulse load; means for connecting said load to said power tube; and a resistor connected at one of its ends to the anode of said control tube and to the grid of the said bias tube and at the other of its ends to the grid of the said power tube and the cathode of the said bias tube.

7. In combination: a control tube, a power tube and a bias tube, each of said tubes having, respectively, an anode, a cathode and a grid; a source of negative voltage pulses connected to said control tube; a voltage power supply the positive side of which is connected to said power tube and the negative side of which is connected to the cathode of said control tube; an output pulse load connected to the cathode of said power tube and to the negative side of said power supply, and a resistor conneeted at one or ends to the anode or said control tube and to the grid 'of the": said bia's tube" and" at are other of its ends to the gridof the said power tube and the catfiede of s" d bia s t ub i 8. A pulse? generating circuit? comprising, in combination, first, second and third discharge devices connected 1n the ordffiafirea; in a'riodelto-cathoderelation, of said'fir'stidifscli rge device defining. one end x sci'r'ciii'tandtlie anode o frsaid third discharge device defining 'tli'eot h'er e'ridof said series circuit; means for, connecting said'c'atliod eifd to a.so;urce of' reference vbltagei niea'ri's forco'rinectiifgsaid anode end to a source of voltage which is positive with respect to said reference voltage and of suflicient amplitude to cause current flow through said series circuit; connection means for the cathode of said third discharge device for capacitively coupling said cathode through a load to said source of reference voltage; and means responsive to the current flow through said series circuit, when in operation, for biasing said second and third discharge devices to thereby limit said current flow to a quiescent value, said biasing means including an impedance means located in said series circuit between said first and third discharge devices, said impedance means being of relatively low value compared to the internal impedance of said second discharge device when the latter conducts said quiescent current, whereby, when said first discharge device is cut off, the quiescent current through said series circuit is interrupted, the bias on said second and third discharge devices thereby removed, and a relatively heavy amount of current, compared to said quiescent current, passes through said load and third tube, said impedance means of relatively low value permitting the bias on said second and third discharge devices rapidly to be overcome.

9. A pulse generating circuit comprising, in combination, first, second and third discharge devices connected in series, in the order named, in anode-to-cathode relation, the cathode of said first discharge device defining one end of said series circuit and the anode of said third discharge device defining the other end of said series circuit; means for connecting said cathode end to a point of reference voltage; means for connecting said anode end to a point of voltage which is positive with respect to said reference voltage and of sufficient amplitude to cause current flow through said series circuit; connection means for the cathode of said third discharge device for capacitively coupling said cathode through a load to said point of reference voltage; and biasing means responsive to the current flow through said series circuit, when in operation, for biasing said second and third discharge devices to thereby limit said current flow to a quiescent value, said biasing means including impedance means located in said series circuit between said first and second discharge devices, said impedance means being of relatively low value compared to the internal impedance of said second discharge device, when the latter conducts said quiescent current, whereby, when said first discharge device is cut oif, the quiescent current through said series circuit is interrupted, the bias on said second and third discharge devices thereby removed, and a relatively heavy amount of current, compared to said quiescent current, passes through said load and third tube, said impedance means of relatively low value permitting the bias on said second and third tubes rapidly to be overcome.

10. A pulse generating circuit as set forth in claim 9, said impedance means comprising a resistor having a value of resistance which is relatively low compared to the internal resistance of said second discharge device when the latter conducts said quiescent current.

11. A pulse generating circuit as set forth in claim 10, said second and third discharge devices comprising triodes, said biasing means being connected to apply bias to the control grids of said triodes.

12. A pulse generating circuit as set forth in claim 9, said second and third discharge devices comprising pen- 7 8 codes, said biasing means being connected to apply bias 2,488,567 Stodola Nov. 22, 1949 to the control grids of said pentodes. 2,516,135 Moore July 25, 1950 2,520,174 Slattery Aug. 29, 1950 References Cited in the file of this patent 2,525,632 Anderson Oct. 10, 1950 UNITED STATES PATENTS 5 2,633,528 Hutson Mar. 31, 1953 2,210,995 White Aug. 13, 1940 OTHER REFERENCES 2,269,001 Blumlem 1942 Radiation Laboratory Series, pub. October 1, 1948, pp. 2,282,340 Pleplow May 12, 1942 55 5 f VOL 2,310,342 Artzt Feb. 9, 1943 2,446,802 Bell Aug. 10, 1948 10 2,449,998 Hansen Sept. 28, 1948