US2159792A - Relaxation oscillation generator - Google Patents

Description

ii .a u y 3 J n J DDLDDI 111111 Filed Jung 2 1937 M GEIGER RELAXATION ,OS C ILLATION GENERATOR INVENTOR M. 2/6512 BY Y ATTORNEY May 23, 1939.

ZEkOl/N t/ Y Emu/v5) PatentedMay 23, .1939

PATENT orrics RELAXATION OSCILLATION GENERATOR Max Geiger, Berlin, Germany, assignor to. we

funken Geoeilschatt tiir Drahtiose Telegraphie m. b. IL, Berlin, Germany, a corporation oiGer- Application June 2. 1937, Serial No. 145,014

In Germany June 8, 1936 i a Claim. (Cl. ate-cs) A multivibrator is known to be a relaxation oscillation generator containing two discharge paths, acting substantially in an alternative fashion, and in which the current passing through each of the two discharge paths is interrupted whenever current appears in the other discharge path. Such relaxation oscillation generators have a resistance-capacity member for each discharge path consisting of a condenser and a resistor connected in series, the one side of said resistance-capacity member being always connected respectively to the other discharge I path. The other side 01' the resistance-capacity member was hitherto connected to the cathode of the respective discharge path. Such relaxation oscillation generators have the disadvantage that the frequency of the relaxation oscillations which they produce is influenced to a comparatively high degree by the so-called disturbance level, i. e.- by the disturbances of nearby circuits inductively, or .capacitively transmitted in the relaxation oscillation circuit.

In order to avoid this disadvantage the resistance-capacity member of each discharge path instead of being connected to the cathode is placed in accordance with the inventioh at a point of a potential that is. pomtive 'relative to the cathode. The sensitivity to disturbances of the relaxation oscillationgenerator can in this way be decreasedto a great extent.

.The features of my invention are shown in the accompanying drawing in which:

Fig. 1 shows a circuit diagram oi my improved multivibrator.

.- Fig. 2 shows a curve of the grid potential of Fig. 6 shows a curve of the grid voltage variation in accordance with my invention. Before elucidating the functioning of the circuit arranged in accordance with the invention,

byway 01 an example of construction, there will now be explained by reference to Figure 1 relating to a multivibrator in the known circuit. the

production of relaxation oscillations under the influence of resistance-capacity members connected to the cathodes oiithe appertaining dis- 1 charge paths, and the sensitivityto disturbance shall be briefly explained.

i m Figure 1, items in ,and u designate a";

common battery. 20.

.rent. Assuming that the dependence of the rec- 'tifier current J. on the voltage U takesthe .amplii ier tubes whose plate circuits contain the resistors i2 and it, while the cathodes thereoi' are connected to each other. A condenser is inserted between the anode of tube II and the grid of tube It, and a resistor is placed between this 5 for the tube H and which consists of a condenser I i6 and a resistor il. Furthermore, it is assumed that between the control gridsot the two tubes and the cathodes a rectifier II and I9 respectively be placed together with'a bias voltage source represented in Figure 1 by a part of the In the circuit shown in Figure 1, assume that the resistances l5 and I] are connected directly between the control electrodes and the cathodes oil tubes iii and II respectively; that is, the conductor ii is connectedto ground potential. Assume further that the tube Ii conducts current, and that the condenser it has a high charge in the sense of the signs indicated. The grid po-' tential oi the tube" lies then far below the lower bend oi the plate current-grid voltage characteristic. In Figure 2, showing the grid potential of tube iii as function of the time, a highly negative grid potential is thus present at this moment as indicated at the point h. The 3 grid potential is traced in Figure 2 in the direction downwards from the zero line. The line K corresponds with the value oi the potential at which current begins to flow inthe tube Ill, 1. e. corresponding to the lower bend of the curve represented in Figure 3 and showing the dependence of the plate' current i. on the grid voltage a The line G correspondsto the grid potential at which the rectiflers II, I! begin to carry curcourse shownin Figure 4, the vertical distance of the line G from the zero line corresponds to the voltage of the tap point P 01' the battery 20 with respect to ground. Beginning with the moment t1 the condenser M will be discharged across the resistor I! in accordance with an e-function, whose time constant is determined by the capacity of the condenser II, and by the value 0! the resistor ll, whereby the grid potential of the tube l0 moves towards the zero value. This e-functi'on is represented in Figure 2 by the curve A whose later part is shown in dotted line.

This curve approaches the zero line as an asymptote. 4 In the intersection point oi the curve A with the straight line Kthe tube Ill begins to conduct current whereby its plate potential decreases owing to the potential drop produced through the resistor 12. Hence, the grid potential of thetube ll decreases and likewise the plate current of this tube, so that the voltage drop through the resistor l3 will be reduced whereupon the plate potential of the tube H increases. This entails a further potential increase at the grid of tube Iii, so that the plate current thereof increases still further, and the plate current of the tube ll drops still further.

This relationship of the plate current of each tube to the plate potential of the other respective tube as determined by the circuit, leads to a complete interruption of the plate current in tube ,il while that of tube Ill increases until the grid of tube it! has only such a low negative po tential relative to the cathode of this tube that the rectifier it permits the passage of current. From this moment, as indicated at the point is in Figure 2, the grid potential of the tube it, and also its plate current, remain at first constant. The condenser it which was charged during the time t1, s will now be discharged beginning at themoment represented at point t: in accordance with an e-function whose course likewise approaches the zero line as an asymptote as in the case of the curve A in Figure 2. This is shown in Figure 5 in which the grid potential of the tube II is traced from the zero line downwards as function of the time. Durin the time t1, if: this grid potential is constant since during this time the rectifier i9 permitted the passing of current. At the moment in the grid potential becomes negative quickly because of the rapid current increase in the tube It), and, from the moment is on, the said discharge of the condenser l6 takes place in accordance with the e-function B. At the moment that the curve B passes through the line K, which has the same significance as that in Figure 2, current begins to flow in the tube ll causing an interruption of the plate current in the tube Ill for the same reason as explained in connection with Figure 2. The grid potential of the tube II is then again constant from the moment is on, because-0f the passage of current through the rectifier l9, and the grid potential of the tube Ill again takes its course in accordance with an e-function.

The influence of disturbance potentials at the grids of the tubes can be easily recognized by an inspection'of the Figures 2 and 5. Assuming that this disturbance potential consists of short, irregularly appearing voltage impulses oi i'or instance 0.1 volt,'the setting in of a discharge current in one of the two tubes, and hence the interruption of theplate current in the other tube, can take place when'the curve A or B is still apart from the line K by 0.1 volt. Therefore, in Figures 2 and 5, there'is shown at a distance of 0.1 volt above the curves A and B, second curves A, B, whose intersection points with the lines K determine the earliest moment in which the relaxation oi the multivibrator can occur under the influence of the disturbance potentials. The disturbance potential. can thus have the effect that the time period t1, ta or t is a transmitter.

4 In; accordance with the invention therefore, the resistors I, I1 are not to be connected to the cathode of the tubes I0, H, but to a point of the voltage source 20 that is positive relative to the cathodes of the tubes. This is indicated in Figure 1 by the line 2|.

This modification of the circuit has the effect that the curves A and B no longer approach the zero line in Figures 2 and 5 as asymptote, but instead approach a horizontal line Z lying above this zero line.v This is shown in Figure 6 for the tube I Ii. The zero line in Figure 6 corresponds to the cathodepotential of the tube l0, and the. asymptote of the grid voltage course A", designated by Z, lies above the zero line to the extent in which the connection point of the line 21 which is dotted in Figure 1 is apart from the cathode potential. Figure 6 shows that the curve A" intersects the line K at a steeper angle than in the case of the curve A in Figure 2. Accordingly, when assuming a disturbance potential having the same value as was presupposed the time t tz-and t2, t2 is to be the same, is to be chosen .difierently from the casein which the resistance-capacity members have cathode potential.

Various modifications may be made in my invention without departing from the spirit and scope thereof and I desire, therefore, that any such limitations shall be placed thereon as are imposed by the prior art and are set forth in the appended claims.

I claim as my invention:

x 1. An oscillator for producing a saw-tooth wave -form comprising a pair of electron discharge devices each of which'includes a cathode, a controlelectrode, and an anode, means including anode resistances for maintaining said anodes positive with respect to said cathodes, means including electron storage devices for connecting the anode of each discharge device to the control electrode of the other discharge device, a pair of resistances, means 'for connecting one end or each resistance to said control electrodes, and means for maintaining the other ends of said pair 01 resistances positive with respect to said cathodes and negative with respect to said anodes.

2. An oscillator for producing a saw-tooth wave form, comprising awpair of electron 'discharge devices each of which includes a cathode, a control electrode, and an anode, means including anode resistances for maintaining said anodes positive with respect to said cathodes, means including electron storage devices for connecting the anode of each discharge device to the control electrodes of the other discharge device, a pair oi resistances, means for connecting one end of each resistance to said control electrodes, means for maintaining the other ends of said pair of resistances positive with respect to said cathodes and negative with respect to said anodes, a pairoi asymmetric units, and means I for connecting saidunits to said control electrodes and to a source of potential negative with respect to said cathodes.

3. An oscillator for producing a saw-tooth wave form comprising a pair or electron dischargedeviceseach of which includes a cathode, a] control electrode, and an anode, means infcluding anode resistances for maintaining said anodes positive with respect to said cathodes. means including electron storage devices for connecting the anode of each discharge device to the control electrode of the other discharge device, and means including a pair of resistances of potential positive with respect" to said cathodes. I

4; An oscillator for producing a saw-tooth wave form comprising a pair of electron dis- 1 charge devices each of 'which includes a cathode, a control electrode, and an anode, means including anode resistances for maintaining said of potential positive with respect to said cathodes, and means including a pair of asymmetric units for connecting said control electrodes to a source of potential negative with respect to ma cathodes.

5.An. oscillating circuit for producing a sawm connecting said control electrodes to a source anodes positive with respect to said cathodes,

tooth wave form comprising a pair of electron discharge tubes each including an anode, a control electrode, and a cathode, means including apair ofresistances for connecting said anodes to a source of potential positive with respect to said cathode, a condenser connected between the anode of each tube and the control electrode of the other tube, a resistance connected to the control electrode of each tube, and means for connecting the other end of the control electrode resistances to a potential positive with respect to said cathodes.

, 6. An oscillating circuit for producing a sawtooth wave form comprising a pair of electron discharge tubes each including an anode, a control electrode, and a cathode, means including apair of resistances for connecting said anodes to a source of potential positive with respect to said cathode, a condenser connected between the anode of each tube and the control electrode of the other tube, a resistance'connected to the control electrode oteach tube, means for connecting the

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