US2560576A - Stabilized multivibrator - Google Patents

Description

y 1951 c. H. HOEPPNER 2,560,576

STABILIZED MULTIVIBRATOR Filed April 16. 1946 5 Sheets-Sheet l ma i l 'JRIGGER PULSE y 1951 c. H. HOEPPNER 2,560,576

STABILIZED MULTIVIBRATOR Filed April 16, 1946 y 5 Sheets-Sheet 2 awe/whoa CONRAD H. HOE PPNER July 17, 1951 c. H. HOEPPNER 2,560,575

STABILIZED MULTIVIBRATOR Filed April 16, 1945 5 Sheets-Sheet 5 I IITRIGGER PUL'SE IN VEN TOR.

CONRAD H. HOEPPNER Attmznley 5 Sheets-Sheet 4 C. H. HOEPPNER STABILIZED MULTIVIBRATOR mwuam mww j July 17, 1951 Filed April 16, 1946 Elma/whoa P fl H M R E N P P E O H H D A R N o C July 17, 1951 c. H. HOEPPN'ER 2,560,576

I STABILIZED MULTIVIBRATOR Filed April 16, 1946 5 Sheets-Sheet 5 LISzJQ INVENTOR. CONRAD H. HOEPPNER Afton/my Patented July 17, 1951 UNITED STATES ATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 6 Claims.

This invention relates to improvements in regenerative types of electronic trigger circuits.

The type of electronic trigger circuit to which the invention relates comprises in general a pair of vacuum tubes the control electrodes of which are so cross-connected to the anodes of the other tubes as to produce one stable state wherein one of the tubes is held normally conducting and the other non-conducting. This state remains or persists until a signal from an external source is impressed upon the circuit whereupon the con-. ducting conditions of the tubes are reversed and in which condition the circuit will remain for a time depending upon the time constants incorporated in the circuit. An alternate arrangement exists where the tubes are so interconnected that the conducting conditions of the two tubes automatically reverse or oscillate back and forth, that arrangement depending upon the time-constant incorporated in the circuit.

The present invention is designed to improve the control of the time duration of one of these states of the regenerative type of trigger circuit by the use of an inductor-capacitor network, located so that it is sensitive to changes in voltages thereupon and acts upon the controlling electrodes of the regenerative type of electronic trigger circuit.

An object of this invention is to provide a control for accurately timing the duration of one of the states in a regenerative type trigger circuit.

Another obiect of the invention is to provide a control which can accurately limit the time duration of one of the states in a regenerative type of trigger circuit to any desired value less than the value depending on the time-constants of the circuit.

Fig. 1 is a detailed circuit diagram of one exem lary embodiment of mv invention.

Fig. 2 shows representative voltage plots pertaining to the circuit diagram of Fig. 1.

Fig. 3 is a detailed circuit dia ram of another exemplary embodiment of my invention.

Fig. 4 shows representative voltage plots pertaining to the circuit diagram of Fig. 3.

Fig. 5 is a detailed circuit diagram of still another exemplary embodiment of my invention.

Fig. 6 shows representative voltage plots pertaining to the circuit diagram of Fig. 5.

Fig. 7 is a detailed circuit diagram of another exemplary embodiment of my invention.

Fig. 8 shows representative voltage plots pertaining to the circuit diagram of Fig. '7.

Fig. 9 is a detailed circuit diagram of another exemplary embodiment of my invention.

' state.

Fig. 10 shows representative voltage plots pertaining to the circuit diagram of Fig. 9.

The operation of an electronic trigger circuit constructed in accordance with the teachings of the invention can be better understood upon reference to Fig. 1, where one typical embodiment of the invention is illustrated. As herein exemplified the circuit comprises a pair of vacuum tubes 9 and I0, arranged so as to sustain one stable state wherein tube 9 is conducting and tube H1 is non-conducting. The active state is when tube 9 is cut-off and tube 10 is conducting. During the active state output pulses may be obtained from the plates of tube 9 and tube l 6. These output pulses will be essentially square, the one from the plate of tube 9 being positive and the one from the plate of tube I!) being negative. In considering the stable state of the circuit it is apparent that, as long as no voltage from an external source is being applied to it, the grid of tube 9 will be conducting and will have a potential very slightly above the cathode potential. This is due to the fact that the grid is connected through inductor H and resistors l2 and 25 to 3+ while the cathode is at ground potential. The voltage On the plate of tube 9 is therefore low because of the voltage drop across the resistor l3. The grid of tube It, being connected between the plate of tube 9 and C- is held below cut-off by means of resistors l4 and I5. Hence the voltage on the plate of tube [0 is B-land the voltage across capacitor I6 is almost 13+.

If a negative pulse of sufiicient value is now applied to the grid of tube 9 the tube can be cutoff. The plate potential will start to rise almost immediately and very rapidly. This rise in potential will be transmitted to the grid of tube Ill through capacitor I! and will cause tube in to start to conduct. Hence the plate potential of tube II] will lower because of the voltage drop across the resistor l8 and, through capacitor is will lower the grid potential of tube 9 even more. Thus it can be seen that a regenerative action occurs to drive the trigger circuit to the active Owing to the potential on the plate of tube Ill and the charge on the capacitor is the grid of tube 9 will be held below cut-off. It will, however, gradually rise as the capacitor It discharges through resistors l2 and I8 and inductor l I.

During this active state, i. e., while the grid of tube 9 is below cut-off, the potential on the plate of tube 9 will remain high and thereby provide the positive output pulse as shown in wave-.

3 form D of Fig. 2. The potential on the plate of tube III will remain low and provide the negative output pulse as shown in waveform E of Fi 2.

When the grid potential of tube 9 reaches cutoff the tube will again start to conduct thereby lowering the plate potential. The grid of tube ID, being connected to the plate of tube 9 through capacitor I! will likewise drop thus reducing the current through tube In and thereby raising the plate voltage. This raise is coupled back to the grid of tube 9 by capacitor Hi to raise it and produce a regenerative action which rapidly drives the trigger circuit back to the stable state.

An observation of Fig. 1 will disclose that an inductor-capacitor ringing circuit has been..incorporated between resistor l2 and capacitor I6. The effect of this circuit will be to'modify the grid potentials exponential rise as capacitor l6 attempts to discharge and then charge with reversed polarity. As was seen, the grid of. tube 9 was conducting current before the negative trigger pulse was applied to it. Abruptly it became non-conducting and tube it] started to conduct. This reversal of conditions causes a surge of discharge current through capacitor 16 which also passes through the inductor capacitor circuit. The. inductor-capacitor circuit' is, thereby, shocked into voltage oscillation, shown in waveform B of Fig. 2 as the voltage at point U with respect to point T. These oscillations are superimposed in the exponential dischargecharge' curve of capacitor l5 thus causing .the grid signal of tube 9 to appear as shown in waveform C ofFig'. 2, where dotted line CO represents the cut-off potential of tube 9.

A further examination of waveform C of Fig. 2 will reveal how' my invention acts to limit the time duration of the pulse. The normal, gradual rise of the grid to cut-off is shown'by. the dashed line Q. With my invention the rise to cut-off is much more abrupt and therefore more accurate. Furthermore, by choosing the proper values for inductor I I and capacitor 19 the. amplitude of the oscillations can be varied. Hence the cut-ofi potential can be reached on any desired one Of several oscillations. This, of course, provides an accurate and stable control onthe time duration of the output pulse.

Upon the return of tube 9 to the conducting state the oscillatory component of the grid signal is swinging positive. The accompanying change in capacitor l6 from a discharging to a charging state causes a reduction of current through inductor I! which, in turn, kicks the oscillations in the inductor-capacitor network in an additive direction. Unless a tubewithextremely low grid impedance is used, one-half cycle later, the oscillations will drive the grid below cut-ofi so that the trigger circuit will be free running, stabilized in both directions by the resonant circuit. To obviate this repeating phenomena resistor 25 is inserted between the grid of tube 9 and a point between capacitor 16 and the inductor capacitor network. This resistor is selected so that the steady state voltage at point U will be above the peak value ofthe oscillatory voltage.

In the second embodiment of the invention, which is shown in Fig. 3, two inductor capacitor ringing circuits, 2D and 2|, arranged in series, are used instead of one circuit as in Fig. 1. The operation of the trigger circuit is the same as described before but the voltage oscillations at point W with respect to point V are'cyclic m .4 amplitude as shown by waveform G of Fig. 4. This is accomplished by tuning 20 and 2| to different frequencies to establish a beat frequency having the desired half period. With this cyclic oscillatory voltage superimposed on the normal grid otential rise Q the actual grid voltage of tube" 9 is as shown in waveform H of Fig. 4. By the use of voltage oscillations which are cyclic in amplitude any danger there might be of the grid potential reaching cut-off on the wrong oscillation may be obviated.

In Fig. 5 the inductor-capacitor network is in the form of a short-circuited artificial transmission line 22. The action of the trigger circuit is the same as described before. In this case, however; the ability of the line to reflect the original trigger signal is used. By using a short circuited line the trigger pulse is reflected with the reverse polarity as shown in waveform J of Fig. 6. This reflected pulse is superimposed on the voltage curve of the grid of tube 9 as shown dotted in waveform K of Fig. 6. This method results in a very accurate control of the time of the pulse duration. It is necessary however, in this method, to use a triggering pulse of such an amplitude that the amplitude of the pulse when reflected will be suflicient to raise the grid voltage to cutoff. Since it takes 2N /LC (where N is the number of sections in the delay line, L is the individual value of the inductors and C is the individual value of the capacitors used), seconds for the triggering pulse to travel down the delay line and be reflected back this will be the time duration of the output pulse.

In Fig. 7 an artificial transmission line 22 is again employed. One end is shorted and the other or sending end is terminated in an impedance which is greater than the characteristic impedance of the line. This line will oscillate in square'waves when a voltage is impressed across the sending end. Waveform L in Fig. 8 shows a negative pulse from a high impedance source which is impressed on the grid of tube 9. As tube 9 cuts off and tube It] commences to conduct a portion of the voltage drop in resistor I8 is coupled to the grid of tube 9 through capacitor l6 and is also impressed across the artificial transmission line 22. Waveform M shows the voltage oscillations appearing across the sending end of the transmission line. Waveform N shows the signal on the grid of tube 9 which is waveform M superimposed on the exponential discharge curve Q of capacitor iii. As shown by the waveforms the; grid is raised rapidly to cut-off potential by a wavefront which has traveled down the line and back three complete times. The pulse put out by this circuit can be terminated by anyone of the positive excursions of the wavefront which appears across the sending end of the line. These positive excursions occur at times Y 2N /LC, where Y'is any odd number and 2N /LC is'the time required for a wavefront to travel down the transmission line and back as explained in'the previous example.

Fig. 9 is an embodiment of my invention in a regenerative type trigger circuit in which the conducting conditions of the two tubes automatically reverse. To understand this circuit assume first that tube 9 is conducting and that tube I9 is non-conducting owing to a charge on capacitor l1. Since tube 9 is conducting a direct current will be flowing through inductor H. Capacitor I! will discharge throughresistor 23 and tube 9, however, until the grid potential of tube l0 reaches C ll-Off. At this point tube 10 will begin gas-ca to conduct and, because of the potential drop acrossresistor IS, the voltage on the anode of tube ID will decrease. A portion of this decrease Will be transmitted directly to the grid of tube 3 through capacitor it so that tube 9 will be cutoif. By the same type of regenerative action described in detail before, the grid potential of tube 9 will be driven considerably below cut-01f and will then tend to rise gradually as capacitor l6 discharges through-resistor 24 and tube I In the meantime, however, the cessation of our-- rent-flow through tube 9 will have resulted in current and voltage oscillations in the inductorcapacitor network H and I9, shown in waveform O of Fig. 10 as the cathode signal taken with respect to ground. The production of such oscillations has likewise been described previously in the discussion of Fig. 1. (More than one inductor-capacitor ringing circuit can be used, as before.) Due to these oscillations the relative approach of the grid voltage to the cathode voltage will not be merely gradual but will be modifled to be also oscillatory as shown in waveform P of Fig. 10. This waveform is the exponential discharge curve of capacitor l6 minus waveform 0.

Hence the net result will be identical with the condition which prevailed in the discussion of Fig. 1, i. e., the voltage difference between the grid and the cathode voltages will suddenly, on one of the oscillations, become less than the difference needed to maintain the tube non-conducting. The tube will begin to conduct and the aforementioned type of regenerative action will cause the trigger circuit to revert to the condition first assumed.

Although I have shown and described only limited and specific embodiments of the present invention it is to be understood that I am fully aware of the many modifications possible thereof. Therefore this invention is not to be restricted except insofar as is necessitated by the spirit of the prior art and the scope of the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

l. A circuit of the regenerative electronic trigger type comprising at least two vacuum tubes each of which has an anode, a grid, and a cathode, an impedance connection from the grid of each tube to the anode of the other tube operative to form an electronic trigger circuit in which only one vacuum tube will conduct at a time, an inductor-capacitor network incorporated in the grid circuit of one of said tubes operative responsive to the establishment of non-conduction in said one of said tubes to produce non-self-sustaining voltage oscillations, said connections including means operative in response to an input triggering impulse to temporarily produce an unstable state wherein said one tube is held nonconducting and the other conducting for the duration of several of said voltage oscillations, said oscillations being eifective to stabilize the time interval said one of said tubes remains nonconducting.

2. A circuit of the regenerative electronic trigger type comprising at least two vacuum tubes each of which has an anode, a grid, and a cathode, an impedance connection from the grid of each tube to the anode of the other tube operative to form an electronic trigger circuit in which only one vacuum tube will conduct at a time, two or more inductor-capacitor circuits serially connected together and incorporated in the grid circuit of one of said tubes operative responsive to the establishment of non-conduction in said one of said tubes to produce non-self-sustaining voltage oscillations, said connections including means operative in response to an input triggering impulse to temporarily produce an unstable state wherein said one tube is held non-conducting and the other conducting for the duration of several of said voltage oscillations, said oscillations being effective to stabilize the time interval said one of said tubes remains nonconducting.

3. A circuit of the regenerative electronicjtrig ger type comprising at least two vacuum tubes each of which has an anode, a grid, and a cathode, an impedance connection from the grid of each tube to the anode of the other tube operative to form an electronic trigger circuit in which only one vacuum tube will conduct at a time, a short circuited artificial transmission line incorporated in the grid circuit of one of said tubes operative responsive to the establishment of non-conduction in said one of said tubes to produce non-selfsustaining voltage oscillations, said connections including means operative in response to an input triggering impulse to temporaril produce an unstable state wherein said one tube is held nonconducting and the other conducting for the duration of several of said voltage oscillations, said oscillations being eifective to stabilize the time interval said one of said tubes remains non-conducting.

4. A circuit of the regenerative electronic trigger type comprisin at least two vacuum tubes each of which has an anode, a grid, and a cathode, an impedance connection from the grid of each tube to the anode of the other tube operative to form an electronic trigger circuit in which only one vacuum tube will conduct at a time, an inductor-capacitor network incorporated in the grid circuit of one of said tubes operative responsive to the establishment of non-conduction in said one of said tubes to produce non-self-sustaining voltage oscillations, said connections including means operative to produce in said trigger circuit a stable state wherein one of said tubes is held conducting and the other non-conducting and further operative in response to an input triggering impulse to temporarily produce an unstable state wherein said one tube is held non-conducting and the other conductin for the dtuation of several of said voltage oscillations, said oscillations being effective to stabilize the time interval said one of said tubes remains non-conducting.

5. A circuit of the regenerative electronic trigger type comprising at least two vacuum tubes each of which has an anode, a grid, and a cathode, an impedance connection from the grid of each tube to the anode of the other tube operative to form an electronic trigger circuit in which only one vacuum tube will conduct at a time, two or more inductor-capacitor circuits serially connected together and incorporated in the grid circuit of one of said tubes operative responsive to the establishment of non-conduction in said one of said tubes to produce non-self-sustaining voltage oscillations, said connections including means operative in response to an input triggering impulse to temporarily produce an unstable state wherein said one tube is held non-conducting and the other conducting for the duration of everal of said voltage oscillations, said oscillations being said tubes remains non-conducting.

6. A circuit of the regenerative electronic trigger type comprising at least two vacuum tubes each of which has an anode, a grid, and a cathode, an impedance connection from the grid of each tube to the anode of the other tube operative to form an electronic trigger circuit. in which only one vacuum tube will conduct at a time, a short circuited artificial transmission line incorporated in the grid circuit of one of said tubes operative responsive to the establishment of non-conduction in said one of said tubes to produce non-selfsustaining voltage oscillations, said connections including means operative in response to an input triggering impulse to temporarily produce an unstable state wherein said one tube is held nonconducting and the other conducting for the duration of several of said voltage oscillations, said oscillations being effective to stabilize the time interval said one of said tubes remains non-conducting.

CONRAD H. HOEPPNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,419,772 Gottier Apr. 29, 1947 2,426,996 Goodall Sept. 9, 1947 2,436,808 Jacobsen et a1. Mar. 2, 1948 2,442,770 Kenyon June 8, 1948 2,445,448 Miller July 20, 1948

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