US2197751A - Push-pull amplifier for relaxation oscillations - Google Patents

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.H. BAHRING PUSH-PULL AMPLIFIER FOR RELAXATION OSCILLATIONS Filed April 1, 1937 Patented Apr. 16, 1940 UNITED STATES PATENT OFFHCE PUSH-PULL AMPLIFIER FOR RELAXATION OSCILLATIONS Herbert Bahring, Berlin-Zehlendorf, Germany,

assignor to the firm of Fernseh Aktiengesellschaft, Zehlendorf, near BerlimrGermany Application April 1, 1937, Serial No. 134,411 In Germany April 2, 1936 Claims. (Cl. 250-27) This invention relates to arrangements for Fig. 1 shows a diagram of the push-pull cirsimultaneous amplification of relaxation cscillacuit independent of the relaxation oscillation cirticns and exciting impulses as are used, for incult to be used. Fig. 2 shows an embodiment in stance, in electrical television transmitting and which one of the two push-pull tubes is used as a 6 receiving systems for analyzing or synthesizing blocking tube of a two-tube relaxation circuit. 5 images. Fig. 3 shows a further embodiment in which the The impulses available to control the relaxarid v l a e f pp ph or a ond e i tion oscillations, for instance, frame or line ta en rom a es or in t en 'gTid ead of synchronizing impulses, do mostly not have the the p fi ube theoretically desired shape, for instance, exact The tubes l and. 2 in Fig. in this Case are 10' rectangular shape, but are more or less distorted. Screen gTid b o the p t Of which They may consist, for instance, of a series of e relttXa-tioh Oscillations are pp in PP short impulses which rise above an irregular in- Site p and 0 the put 5 and of which terference oscillation. Furthermore, they must e x i imp ar pp e i the same be amplified to an amount whjgh makes a, secure phase. The plate circuits 0f the tubes are con 15 control of the relaxation circuit possible. If a cted by a load esistor 3 in such a manner that tube of the oscillating circuit was simultaneously the amplified relaxation oscillation may be taken usedfor impulse amplification, these interferfrom 9 and H and the a p fi e C ences would also be amplified and be noticeable P 5 y e taken m 9 and t3, and Hi and on the image. On the other hand, it is not de- H. r s v The r s 8 is centtit-tapperl-v 2o sirable to provide for an extra amplifier stage for W s g maghetifi deflection, the I'eSiStOI s the exciting impulses because the cost of th substituted by a choke. Aresistor I2 is provided entire set will thereby be increased, in order to compensate for non-uniformity of the Therefore, it is the object of thi in tio t tubes. A resistor is and a condenser M serve to 25. apply the exciting impulses in the arne phase to produce the bias for the tubes, and a resistor two amplifier paths in push-pull, whereas the It makes the adjustment of the re id relaxation oscillation voltage is applied in oppo- VOltage p ss Th condenser H serves as a site phase to these am lifier paths so that comcoupling condenser f the yn niz n impensation of the exciting impulses and their interp se ferences occurs in a load resistance. If both tubes are exactly alike, compensation 30 This arrangement. has the advantage that the 0f t e exciting impulses applied at 6 and I oosame tube may simultaneouslybe used for amcurs also if resistance I2 is not provided. As the plification of the relaxation oscillation and for e n grid currents r of pp i h he amplification of the pulses without allowing inresulting current variation in the resistor l2, and

terferences in the impulses or the impulses proper thereby t e Variation in Screen grid Voltage 35 to influence the amplified relaxation oscillation. caused by the screen grid relaxation current in The amplifier tube, which represents one of the is Thus, there is 110 eaction of the two amplifier paths, may be used at the same screen grid on the control voltage so that a pure time as blocking tube in a two-tube reflex resaw-tooth wave will be amplified. In this case,

laxation circuit, the short-circuiting condenser !5 may also be 40 It is a further advantage that impulses of eliminated whereby the input impedance of the opposite phase may be obtained between anode impulse circuit will be increased. If, however, and cathode of both push-pull tubes if the load he tube 5 has a p fi on a or Of #1 and is inductive. These impulses are produced by a plate resistance Rii, and the tube 2 has an the saw-tooth shaped voltage at the grid and by mplifi ti n f r f #2 and a p e re istance 45 the voltage produced by the saw-tooth shaped Rig, the value R2 of the resistance I2 for intercurrent accordin to the law ference compensation will be divided by a tap 8 in a part 11 on the side of tube l, and a part r2 L on the side of the tube 2 in such a manner that These impulses may be used as positive or nega- T (Ri tive impulses for the synchronization of further circuits. T1 T2 (Ri The drawing shows embodiments of the inven- 55, tion. 3 I J wherein Ra is the impedance of the resistor 8.

Y I Yi Y Y Y IY In Fig, 2 thepush t-pull circuit is joined with a f I I Y I ;two -tube reflex relaxation circuiti Y I Y I Y I Y I Y i Y I i Y The Y push-pull circuit corresponds to that or I I Y I Y Y IFig; l: exceptthat the synchronizing impulses ing of the Y condensers 28, 3E, 35 and 35 occurs, Y I Y 1 through the Y devices I 21- and 28. Y The charging I I Y I I I I occurs in Y opposite phase Y symmetrically to the Y I Y I Y Y cathode of the tubes landZ, which are grounded- I Y Y Y Y Y Y Y Y Y Y I I I :not applied. :to-the screen igrids of the push+p1n1 through the biasdevice l3 and 14; I Avoltage iris I Y I Y Y Y Y Y i :tubes, buttothecontrol grids in thesame phase, Y ing opposite phase is applied to the grids of Y Y Y Y Y Y Y I by roeansof a resistor Z L- .The grid of a discharge; Y the push-pull tubes at the voltage dividing taps Y I Y I I I tube is connected by: condenser 2 3 with the during the charging :period of: the: condensers; Y I Y I Y Y Y Y I I I I I Y plate circuit f: the tube: The, tuned: serves Y The screen grid: currents and plate currents of Y I Y 1; the periodicaldischarge of the condensers 23, S I I the tubes: l and ,2 also very in O p Phase YSOY Y Y Y 35 and e Ehgfging current t k from a Y that the: voltagevariation on the screengrids; is Y I Y I Y supply source atithe points is and 2e, and flows- Y :nili while the; variation in plate Current will be I Y i Y s m t a v eg ;2a a d gas Ewhichi may, fe r made u sef ul by utilization :of sawtooth current i Y IY instance; be resistors or saturated diodes which Y inthe: resistancefl, or by tak ng a saw-tnothvo Y Y I allow theflgvgrofa ub tantially on ta t m t-'5 age from the resistance 8; I If both halves of the I1 I YIYIY u-The relaxation'periodIis started by apnlying a I I I I I 85; I'llhe'amplitude of theiimpulseson the grid oi the p it d v i a nnthe grid 0f tube t n IY Y Y i T I diSGhaIg2 tube: must :lie approximately i to 2 Y I the sridcf: tube l ,Iand:to cause the samep t m Y I Y i Y IY Y Y Y Y I Y mvoit abov theinoiige level; which is Icamedby Y tial; variationsinthe; plate circuits ofiboth amplii-; i I I I I I I I I variations of thevoltage supply; rorinstanee,tne I Y fi r t bes by the ynchroni n imsu s a-p l YI IY I:I: II I: rectifier:arrangement-oiby electrostatic 'or rnag I Y t th sr da r s s 4i! and 4|: must have I Y Y Y Y YY Y Y Y f m ,n'eticI interference; Y one charging or the eon- I su hw u s t h mi Y Y Y den'sers 29,35, 35 and Iifiover' 2i and 26 is dis- 131G135? Y Y Y Y Y Y Y Y Y Y Y turbed in suc h a manner that the plate current YY Y Y Y of the tube 5 is still further decreased, and the 2 impulse applied to the grid of the tube 22 be m 5 comes still more positive. The condensers 29, 3!, 1= '2 o 3 Y g g fi g 5 5 522255 5 2 3 23?; 5, 2%: The above relationship represented in the first drop caused by the discharge current in the equation is derived from a consideration of the sistors s2 and s3 aids the back feed. The tube W tubes Operating in h pllsh'pun amplifica' 22 is not blocked and remains in this condition g of the f S E f F such 0501113" through the period of back feed over the resistors g i ig g gf gi g gg g and respectlvely durmg E dlsclfiarge the relaxation oscillator circuit associated with 01. Litre clondensiers 29 gi lm ga fz 2 the tube 22. The derivation of the formula is or 1 en sync as follows. The relaxation oscillation voltage lmplulse p 1s shoQrler than P applied to the grid of tube I is amplified a total charge period. During the discharge period the of 2 times where 2 is the amplification factor grid the tube 22 becomes strongly positive of the tube taken between the control grid and E 1t w gnd current Durmg the dlscnarge screen grids. It follows, that the voltage applied ese electrons flow through the Condenser to the control grid of the tube 2 must equal the After the discharge completed they Cause a screen grid voltage of tube I divided by the am- 60 g charge f of f tube so that plification factor ,u., in order to realize the same thls gnd become g Y blockefi plate voltages in the plate circuits of both tubes. charge of the Pondenser W111 equahze ltself The total effective voltage of screen grid circuit through the resistance the Condenser the of tube I is divided across a circuit of R1 R'z and 5 condenser H and one-half of the resistor 8, ac- Riz in series, f which R32 is the ht nt f cordmg to thelr F Constants- The resulting resistors 4| and 43 in parallel and. constitutes Voltage 011 the and 15 thus not n dependent the portion from which the signal is obtained and on the character of the exterior resistance, but applied t t control grid of the tube 2 Hence also upon the time constants of these elements. I Furthermore, they can be shifted by a constant 70 amount by varying the potentiometer 25. Dur- RI+RI2+RM ing the rise of the curve its instantaneous value, from Whlch however, is of such a magnitude that it prevents 13 312 the tube 22 from drawing plate current. Because Y of the blocking of the discharge tube, the charg- The second formula is derived from a consider-'- 1 'I'he condensers 29 and ti; Y and 35 and gdli; re Y I Y spectively, form a capacitive voltage divider, the Y Y Y Y Y I tape :of which are connected I with the Y grids of I I I I the tubes I l I and 2.: I The resistances 24 and: E5

:serve to adjust the discharge period of; the Y con- I "denser Y I Y i Y Y Y I'he operation of: this circuit is as followsz I Y I Y i Y I Y I I Y i Y I Y I Y Y i Y I Y I change is greater than theirsulse on. the grid; Y i Y Y i i 1 1 Y I Y i Y Y I i I applied to the gi'idi Of the discharge? tube: 22 Z I Y I Y I Y Y Y by: means of a coupling condenser 23; -The d I I charge: tube: 22$ begins I to; draw plate current, I Y

:pull tubes 2 l I and 2 at'the points ii and 3; :This' Y I I I Y I causes aniincrease in platepotential by the same I I Y I amount or both tubes I E and 2 so that the d e Y i I I 1 Y 1 I Y Y fleeting system connected ;atis and it remains Y Y I 1 I ;uninfluenced. Y 'Ihe change in plate potential in I Y the tube 1 ini respect to its Y cathode, i which i i Y Y Y :negativeinipulse to the grids of the two push-J lead; of: the tube i.

load resistance 3; are dynamically: coupled; it; is I possible to: swing: both amplifier, tubes in the Y Y Y I non;-linea;r i'ange of, the characteristic in I order, I f Y to obtain a resulting saw-tooth curve Y Y Y I Y If the synchronizing impulse comes to its i end I after the condenser has started to charge, the Y Y Y Y I alnode; potentials: of both tubes -I: and 2; will be i Y Y come more negative b yIthe same amount, so that I Y I :no Iinterferencein the image Iwiil Ybe noticeable; I The increased negative bias; on: the grid of: the Y blocked: tube 22 has only: the effect of blocking Y I thistabe stillmohe; Y :The iength of: duration of I Y I Y the synchronizing impulse is, therefore; of Y no I Y I Y I impo tancefor theicircuitl i Y i Y I Y Y Y I Y I I Fig 3 shows a circuit in which-the tubes;i and I I Y I 2 are not arranged symmetrically; but in: which i Y I Y I Y Y the grid gvoltage of opposite; phase for the Ituhe 2 I Y I I Y is taken from a resistance in I the screen, grid Y Y Y Y Y Y In, order to obtain the same Y Y so I impulses to obtain a balanced output therefrom,

ation of the two tubes l and 2 operating as amplifiers for the synchronizing impulses applied to the screen grid of the tube I. Since both tubes are presumed to be identical, the amplification factor 1 of tube 2 taken between the control grid and plate will be the same as the amplification factor of tube I. However, the synchronizing impulses are not applied to the control grid of tube I, but to the screen grid of tube I, and consequently the amplification factor of tube I with respect to signals applied to the screen grid, will be different and equal to s. Of the signals applied to the screen grid of tube I, a portion thereof will be applied to the control grid of tube 2, this portion being equal to the ratio of the equivalent resistance 41-1-43 over the sum of this equivalent resistance the resistance 40 which may be expressed as R? 2+R1 where R2=the equivalent resistance of 4:14-43 in parallel and R1=resistance 40. To obtain the same effect in the plate circuits of both tubes, the values of R'z and R1 must be such that Simplifying this equation to obtain a value for R1, one obtains The condenser 42 is a coupling condenser; the condensers 45 and 46 serve as by-pass. The operation of the relaxation device formed by the tubes i and 22 is exactly the same as that of the tubes 1 and 22 and the circuit according to Fig. 2. The circuit does not require a supplementary plate suppLv source for generation of the saw-tooth voltage of oposite phase.

I claim:

1. In combination, a source of relaxation oscillations, a source of control impulses, and common means for simultaneously amplifying said relaxation oscillations and said control impulses and applying said amplified control impulses to said source of relaxation oscillations to control the frequency thereof.

2. In combination, a source of relaxation oscillations, a source of control impulses, a pair of electron discharge devices, means including said discharge devices for amplifying said control means also including said discharge devices for amplifying said relaxation oscillations to obtain an unbalanced output therefrom, and means connecting one half of said balanced output to said source of relaxation oscillations to control the same. I

3. In combination, a source of relaxation oscillations, a source of control impulses, a pair of electron discharge devices, means including said discharge devices for amplifying said control impulses in push-pull relationship to obtain a balanced output therefrom, means also including said discharge devices for amplifying said relaxation oscillations in push-pull relationship to obtain an unbalanced output therefrom, and means connecting one half of said balanced output to said source of relaxation oscillations to control the frequency of the same.

4. In combination, a pair of electron discharge devices connected in push-pull, a condenser charging circuit apportioned equally between the input circuits of said electron discharge devices, a separate electron discharge device connected across said input circuits, and having a control grid, means for applying impulses to said input circuits in phase to provide amplified impulses in balanced output in the output circuits of said push-pull connected discharge devices, and means for connecting the control grid of said separate device to the output circuit of only one of said push-pull connected devices.

5. In combination, a pair of electron discharge devices having output circuits connected in pushpull arrangement, a condenser charging circuit, means for applying potentials from said charging circuit out of phase to the input circuits of said electron discharge devices to provide amplified potentials across the push-pull connected output circuits, a separate electron discharge device connected across said condenser charging circuit, and having a control grid, means for applying synchronizing'impulses in phase tosaid input circuits of said pair of electron discharge devices to provide amplified impulses in balanced output in the push-pull output circuits of said discharge devices, and means for connecting the control grid of said separate device to only one of said push-pull connected output circuits.

HERBERT BAHRING.

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