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May l5, 1951 B. c. FLEMlNG-wlLLsAMs 2,552,949 WAVE-FORM GENERATOR - Filed Feb. 24, 1948 Brian C. Fleming-Williams Patented May 15, 1951 2,552,949: UNITED STATES» PATENT OFFICE 2,552,949 WAVE-FORM GENERATOR Brian ICliüord Fleming-Williams, London, Eng land, assignor to A. C. ICossor Limited, London», England, a British company Application February 24, 1948, Serial No. 10,386 In Great Britain April 19, 1944 . Section 1, Public Law 690, August 8, 1946 Patent expires April 19, 1964 8 Claims. (Cl. 250-27) l 2 This invention relates to thermionic valve cir A diode D4, connected between the suppressor and cathode o1" valve VI, is provided to prevent cuits serving for the generation of linear poten tial sweeps and/or abrupt potential steps and being of the kind comprising a valve amplifier having a point in its anode circuit connected through a differentiating network to 4a point of the suppressor potential from rising appreciably i) above that of the cathode. Alternative arrangements are shown for the `ap plication of either positive-going or negative constant potential, and having its input voltage derived from the output of this differentiating going firing pulses to the circuit. Terminal Tl, for the application of positive-going ñring pulses. network, so that a substantially linear potential sweep of the valve anode is obtained. A circuit of this kind according to the inven tion comprises a rectiñer connected between one of the valve electrodes and a source of potential variations for ñring whereby a potential varia is coupled to the anode of diode D3 through con denser C3. This anode is normally biassed about 2U volts negative to its cathode so that the am tion may be applied to this electrode to initiate a potential sweep of the valve anode, and whereby this electrode is thereafter isolated from the nr ing source throughout the course of the anode potential sweep. _ The accompanying drawing shows a circuit diagram of an arrangement embodying the in vention, which, in response to the application of a ñring pulse of potential, produces at one out put terminal a single linear potential sweep fol lowed by automatic return, and at another out put terminal a single square wave cycle of po tential. The valve VI is a pentode which may be of the Mazda AC/ SP1 type. plitude of the pulse must exc/eed this value be fore it becomes effective/on the circuit. This bias is given by potentiometer R8, R9, which is connected between earth and the foot of resistor R6 and has the voltage across it smoothed by condenser C4. The circuit has a stable condition with the anode approximately at the potential of the slider of potentiometer Rl Iand `with the suppresser at the potential of its bias source. The whole of the cathode current oi valve Vl is then flowing to its screen. The control grid is held approximately rat earth potential by the diode D2, and the poten „» tial between cathode and control grid is therefore determined by resistor R5. Suppose that a positive-going firing pulse is now applied at terminal TI suñicient to overcome t the bias applied between the electrodes of diode The cathode of this pentode Vl is connected 30 D3; then the potentials of the screen and sup to earth through a biassing resistor R5. pressor are raised together. Anode current be The control grid and anode are ’coupled by a ` gins to flow in valve V! at the expense of that condenser Ci, and the control grid is connected which has been flowing in diode DI. When this through a high resistance R3 to the positive line, becomes sufficient for diode Dl to be cut 01T, the which may be at 300 volts to earth, preferably 35 potential of the anode of valve Vl begins to fall. stabilized. A small stopper resistance Rl 0 is con Owing to the coupling between anode and control nected in the lead to the control grid to prevent grid through condenser CI, the control grid is parasitic oscillations. A diode D2 having its driven negative, with the results that diode D2 cathode connected to earth prevents the control is cut off and that the cathode current of valve grid potential from rising appreciably above that 40 VI is reduced. The screen potential therefore of earth. rises further, 'carrying the suppressor with it. The anode is connected to the positive line The eiîect is cumulative and proceeds extremely through 1an anode load resistor R4. It is also rapidly until a meta-stable state is reached inl which the `anode current is approximately the connected through a diode DI to the slider of a potentiometer Rl , which is connected between the 45 sum of the currents through resistors R3 and R4. In this meta-stable state the current through re positive line and earth. This prevents the anode potential from rising appreciably above the po sistor R3 is the current flowing to condenser CI. During the change from the stable to the meta tential selected by the slider of potentiometer RI. The screen and suppressor are coupled by a stable state, the fall of anode `and control grid condenser C2. The screen current is derived from 50 potentials is not more than about 3 volts. At the the positive line through resistors R6 and R1, the same time the rise of screen potential may be about 60 Volts. The suppressor potential is, how voltage across resistor R6 being smoothed by con ever, prevented by diode D4 from rising lappre denser C4 to earth. The suppressor is biassed ciably above that of the cathode, and the con through resistor R2 from a source which may be about 15 volts negative to earth. ' 55 denser CZ therefore becomes charged. This 2,552,949 4 i 3 charge leaks away slowly through resistor R2 dur ing the subsequent cycle, but may leave the sup pressor with considerably more negative bias at the time of arrival of the next ñring pulse than is providedV by its negative bias source alone. The suppressor is therefore to some extent automati cally biassed and so the actual value of negativev bias voltage applied is not very critical. Negative-going firing pulses applied at termi nal T3 reach the anode of pentode VI by pass ing through coupling condenser C5 and diode D5. ïn view of the fact that thev tapping of potentiom eter RI is adjustable, a separate D. C. source B is employed to provide bias for diode D5, in or der that negative-going firing pulses applied at terminal T3 shall be ineffective unless they ex ceed a predetermined minimum amplitude. During the meta-stable regime the anode po tential will make a linear sweep downward while 10 Resistor RII is provided to increase the imped ance across whichv the firing pulse builds up. the control grid potential- makes an :approxi When a negative-going firing pulse is applied mately linear sweep upward across a small por to the anode of pentode Vl, the transition from tion of its grid base. The velocities of theseV po the stable to the meta-stable condition will pro tential sweeps are determined by the Values of ceed as a result of those same cumulative effects resistor R3 and condenser Cl. The discharging as have been described as the result of the ap rate of condenser CI will approximately corre plication> of a positive-going firing pulse from spond to the discharging rate which it would have terminal TI to the screen. if connected in series with a, resistance of value As with the network associated with terminal G times R3 across a direct voltage source 'of value G times the voltage of the positive line, G being 20 TI, an additional bias will be applied to diode D5 foi‘ a periodi after ñring. This is due to the cur the gain of the valve Vl asl an ampliñerV inv the rent which ñows> from condenser C5v through present circuit. While these sweeps of the anode diode D5.; and its duration will depend upon the and control grid potentials proceed, the potential time-constant C5, RI l, governing the recharging of the screen will remain >approximately constant, andV therefore'that of the suppressor also because 25 of condenser C5. Yet another alternative Afiring circuit is shown the time constant CZR-Z is long relative to the in connection with terminal T4, and this again duration of the sweep. wil-l not normally be provided if' either of the net The termination of the meta-stable regime will works associated with terminal Tl or T3 is occur automatically when the anode has reached a very low potential, because the current to the 30 present. Terminal Tft is used for positive-going firing screen then increases with the result that screen pulses and these are applied through diode D6 and suppressor potentials both fall. The anode tothe suppressorV of pentode VI, which serves as current is then cut off, and the anode potential a second control grid, i. e. a grid controlling proceeds to rise exponentially as condenser CI is charged through resistor R4 and diode D2. 35 the division of current between anode and-screen. If bias is desired, resistor-RIZ will be connect Diode D2 prevents the potential of the control ed to a point of ñxed potential more »negative than grid from rising above earth potential. When that to which resistor 'R2 is connected. A the anode potential reaches that'of the slider on temporary increase in bias, after ñring, will-again established and the circuit is again ready >for op 40 occur as a result of the discharge condenser C5 through diode D6, and-its time of decay willde' `eration in response to a ñ-ring pulse. It will be pend'on theStime-constant C5, Rl 2. evident that the >potentialselected by the slider If no bias is required for the purpose ofY pre on potentiometer Rll setsY the amplitude of the venting small potential variati‘ons from firing-the ranode potential sweep independently of the veloc circuit, negative-going ñring» pulses may be ap' ity thereof. plied'ïat'the cathode of diode DI. This avoidsthe The ñring pulse network shown in connection necessity of providing any of the additional diodes with terminal TI has the advantage that, when D3,'D5, D6. ïf this method is to be'used, it will one 'îiring has occurred, 'an'interval of time iol" be preferable that a further resistorY be inserted lows during which it cannot be caused again ex' between the tapping on potentiometer Rl and the cept by a stillV larger pulse than that which is-d'e‘ cathode of this diode to provide an'ad'equate im'-l termined by the value of the steady bi'as applied pedance for the nring pulse to build up on. to diode D3. The cause of this eiîect is the If it is desired-to obtain linear potential sweeps temporary increase in bias due to the further as output from the circuit, these may be taken charging of condenser C3 by the current which flows through diode D3 when ñring occurs. The 55 from the anode of ~valve VI. If abrupt potential steps are desired, these may be taken from the additional charge leaks away slowly through resis potentiometer RI, the stable condition is vagain tor R8. Diode D3 serves to isolate, during the meta stable regime, the generator circuit under con screen. The form of the wave front of the po tential step is identical with >that of the upper part of a positive ñring> pulse applied at terminal sideration from the source (not shown), con 60 Tl, provided that this pulse rises'rapidly. The following table gives a set of Values forthe nected to the terminal Tl which provides the various components of the circuit, suitable for use firing pulses. for generating linear potential sweeps and square This isolation prevents the >possibilities that waves of. potential havingv durations ofthe order further potential variations in the ñring source might either stop the anode potential sweep or 65 of 100'microseconds. at least spoil its linearity. It also prevents the generator circuit from reacting upon the 'firing ' SOllI‘Ce. Terminal T3 and the network associated there with, including diode D5, provide an arrange Rl=25 kilohms VRI l :50 kilohms R [2:150 kilohms R221 meg'ohm R3=500 kilohms 70 R4L-:300 kilohms C i =’100 lp-ico'farads `C2=0.001 Inicrofarad ment for applying negative-going >firing pulses R5=2`00 ohms to the circuit. This network will normally be provided only as an alternative to, and not in RôzRL-¿IO kilohms C3.:'U.O1> microfarad 04:10.25.' micrcfarad addition to the network‘com’prising lterminal TI _ R9'-_-'100 kilohms '0620,01 micrófarad and diode D3. RWI-500 ohms ¿Cäzûß-lmicroíarad ’ ` ' ' 2,552,949 5 6 to said first control electrode, a further con denser connected between said second and third ponents, the duration of the generated potential control electrodes, a source of firing potential, a sweep and square-wave may be lengthened to the rectifier device connecting said source of ñring order of several seconds. The circuit described may be converted into a Ul potential to one of the electrodes of said tube, and a source of potential biasing said rectiñer de free-running time-base or square-wave generator vice to be normally non-conducting in the absence by reducing the bias on the suppressor grid, and of iiring potential from the said ñring source. the firing arrangements described may then be 4. An electron discharge tube circuit accord used for synchronising, lO ing to claim 3, for use when the source of iiring I claim: potential provides a negative-going firing pulse, l. A thermionic valve circuit for the generation wherein said rectifier device is connected to said of linear potential sweeps and abrupt potential anode and is arranged to conduct away from steps comprising an electron discharge tube hav said anode. ing a cathode, an anode, a first control electrode, 5. An electron discharge tube circuit accord a screen grid between said control grid and anode ing to claim 3, for use when the source of ñring and a second control electrode between said By appropriate alteration of the values of com screen grid and anode, a source of potential, con nections between said tube and said source for applying to said anode and screen grid potentials positive relative to said cathode, a resistor in cluded in said anode connection, a second resistor and a condenser, a connection from said anode, through said second resistor and said condenser in series to the positive terminal of said source, a connection from the junction of said second re-sistor and said condenser to said ñrst control electrode, a iiring terminal to receive a potential variation for firing said tube and a rectifier hav ing its anode connected to said terminal and its cathode connected to said second control electrode. 2. A circuit according to claim 1, including a time-constant circuit comprising a second re sistor and a second condenser, said second con denser being connected between the anode of said rectifier and said terminal and the time constant of said time-constant circuit being not less than the period of said potential sweeps. 3. An electron discharge tube circuit for thek generation of linear potential sweeps and abrupt - potential steps, comprising an electron discharge potential provides a positive-going ñring pulse, wherein said rectifier device is connected to said third control electrode and is arranged to con duct towards said third control electrode. 6. An electron discharge tube circuit according to claim 3, for use when the source of ñring po tential provides a positive-going firing pulse, wherein said rectifier device is connected to said f' second control electrode and is arranged to con duct towards said second control electrode. 7. An electron discharge tube circuit according to claim 3, and including a third condenser con nected between said source of firing potential and said rectiñer device, and a leak resistor for said third condenser providing a time constant of discharge of said third condenser of not less than the duration of each of said potential sweeps. ` 8. Circuit according to claim 3 and including a biasing resistor connected between said cathode and said source of space current, and a rectifier having its anode connected to said other terminal of said condenser and its cathode connected to the negative terminal of said source of space cur rent. BRIAN CLIFFORD FLEMING-WILLIAMS. tube having at least rive electrodes including a REFERENCES CITED cathode, an anode and at least three control elec The following references are of record in the trodes, a first of said control electrodes being nearest said cathode, a second being nearest said 45 ñle of this patent: UNITED STATES PATENTS anode, and a third being intermediate said i'lrst and second control electrodes, a source of space Number Name Date current, a connection from the negative terminal 2,164,968 Urtel et al. __________ July 4, 1939 of said source to the cathode of said tube, a con 2,172,746 Young ___________ __ Sept. 12, 1939 denser having one terminal connected to said 50 2,199,278 Black ___________ __ Apr. 30, 1940 anode, a resistor, a connection from the other 2,270,405 Black ____________ __ Jan. 20, 1942 terminal of said condenser through said resistor to the positive terminal of said source, a connec tion from said other terminal of said condenser 2,418,538 2,457,974 Yetter ___________ __ Apr. 8, 1947 Bliss _____________ __ Jan. 4, 1949