US2536822A - Saw-tooth multivibrator circuit - Google Patents

Description

Jan. 2, 1951 F. H. SLAYMAKER ETAL 2,536,822

SAW-TOOTH MULTIVIBRATOR CIRCUIT Filed April 15, 1946 UOUJP w-{III I L /|o LOAD l 3 g INVENTORS 4 WILLARD F. MEEKER BY FR-ANK H. SLAYMAKER ji zzzz TORNEYS Patented Jan. 2, 1 951 Frank H. Slaymaker and Willard F. Meeker,

Rochester, N. Y., assignors to Stromberg-Carlson Company, Rochester, N. Y., a corporation of New York Application. April15, 1946, Serial No. 662,144

5 claims; (01. 250-36) l This invention relates to wave generators and more particularly to means for generating sawtooth waves.

Circuits have heretofore been devised for producing or generating waves having a saw-tooth configuration. For example, blocking oscillators have been used frequently for this purpose but relatively high voltage plate or anode supplies are required. i

It is an object of this invention'to provide a new and improved. means for producing a sawtooth wave i using a minimum numberof parts, having a low cost, which is light in weight and which enables use of electron discharge devices utilizing low current filamentsand relatively low anode voltages. r l

It is another object of this invention to employ a multivibrator circuit to produce saw-tooth Waves. This object is achieved by making .the values of resistance and capacitance associated with the anodes of the multivibrator. tubes. of such values that the time constant thereof is relatively long.-

Other objects and advantages of this. invention will become apparent as the following description proceeds when read with reference to the accompanying drawing in which Fig. 1 is a circuit diagram illustrating an embodiment of. the invention, Fig. 2 comprises a series of diagrams useful to a complete understanding of the operation, of the circuit of Fig. 1, and Fig. 3 is a modification of the circuit shown in Fig. 1.

Referring to Fig. 1, there is shown a multivibrator comprising a pair of electron discharge devices I and 2 including anodes 3 and 4, respectively, filaments 5 and 6 respectively; and control electrodes 1 and 8 respectively. The operating current supply includes a suitable source ofpotential 9 whose negative terminal is grounded and whose positive terminal is connectedto anodes 3 and 4 through suitable resistances 1 and il as shown. .The filaments 5 and 6 are grounded in this embodiment of our invention. The control electrodes 1 and 8 are positively biased by means of a connection to the source of potential 9 throughresistors l2, .l3 and M as shown, the resistor [2 being common to both biasing circuits and preferably being variable to enable easy adjustmentof the bias and hence of-the frequency of oscillation. In order to cause the discharge devices to operate in multivibratoiigfashion, a condenser L5 :is connected betweenco'ntrol electrode 1 and anode 4 and a condenser is connected between control. electrode a'and anode 3.

As :iswellunderstood. in customary -multiyi--zbrator circuits, there are periodically produced at .the anodes substantially square pulses. This condition is illustrated in Fig. 2 wherein at A is depicted the potentials appearing at one of the anodes (let us assume anode 3) and at B is illustrated the potentials existing at the other anode (anode 4) at the same instants of time.

In accordance with our invention the capacitance of capacitors I5 and I6, and the resistance of resistor H are so chosen that the anode and control-electrode potentials change so slowly that the control electrode increases in the positive sense to cut-oil? while the anode potential is still increasing linearly. In Fig. 2, at C and D are represented possible potentials at control-electrodes 1 and 8 respectively varying with time. Cut-off is represented by the dashed line. At E and F of Fig. 2, possible potentials of anodes 3 and 4 are shown. The dotted lines represent the potential relationship if the multivibrator period is long enough to permit the potential to reach its maximum. In accordance with the conditions set jorth above, however, at time 131 for example, the control electrode of discharge device I reaches ,cut-off and device I conducts. During the rise ,of potential at control-electrode I (Fig. 20), the anode potential is increasing as shown at Fig. 2E. The potential at control-electrode 8 now begins to rise toward cut-off (Fig. 2D) and at time its the multivibrator again switches. Figs. 2E and .21 therefore show that saw-tooth pulses of voltage appear alternately at the anodes. In other words, the R-C, or time constants, of the anode .circuits are so chosen that the anode potential rises linearly throughout the non-conducting or .ofi period of each discharge device. The anodes :may be connected through suitable resistance .means which may be a single tapped resistor, a potentiometer, or two separate resistors, one end of each being connected to an anode and the other ends connected to load resistor III. In Fig. -1 there is illustrated a potentiometer ll. .3 shows the use of two resistances l8 and I9. A ,load I! connected across resistor ill will have Fig.

supplied to it a saw-tooth wave of form illus- ,trated by Fig. 2G.

Use of a potentiometer facilitates balancing of the circuit to insure likeness of successive saw-teeth.

In Fig. 3 there is shown a modification elimiv nating the potentiometer H. In this arrangement anodes 3 and 4 are connected to the endsof resistors 18 and [9 respectively, and the common connection between the resistors is connected to the positive terminal of source 9 through resistor I0.

To illustrate suitable parameters for the practice of our invention, referring to Fig. 3, satisfactory results have been obtained using type CKEOQAX discharge devices, resistances I3 and 14 of one megohm each, resistances l8 and I9 of 0.47 megohm each, resistance In of 0.1 megohm and capacitors l and i6 of 0.3 microfarad each.

The frequenc of the generated wave is controlled by adjusting the control-electrode potentials by means of resistance E2. The minimum frequency while maintaining linearit is determined by the time during which the anode potential rises linearly.

While we have shown and described a particular embodiment of our invention, it, will be. obvious to those skilled in the art that changes and modifications may be made without departing from our invention in its broader aspects. For example, heater tubes may be substituted for filament devices l and 2. We, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim is: y 1. A saw-tooth wave generator including a multivibrator comprising a pair of electron discharge devices each having a cathode, an anode and a control electrode, a connection joining said cathodes, continuously conductive means for biasing said control electrodes, cross-couplings between the anode of one of said devices and the control electrode of the other of said devices and l riods.

2. A saw-tooth wave generator including a" 'multivibrator comprising a pair of electron discharge devices each havin a cathode, an anode and a control electrode, a connection joining said cathodes, continuously conductive means for biasing said control electrodes comprising resistive elements connected to a source of positive potential, the negative terminal of said source being jconnected to said connected cathodes, crosscouplings between the anode of oneof said devices and the control electrode of the other of said devices and between the control electrode of said one device and the anode of said other device, tapp-ed resistance means connected between said anodes, a resistance element connected in series between said source of positive potential and the tap on said resistance means, and a load element connected across a portion of said resistance element, said cross-couplings and resistance ;means being chosen to provide a time constant 'sufliciently great to cause the anode potential of each discharge device to rise substantially linear- "ly throughout its own non-conducting periods.

3. A saw-tooth wave generator includin a multivibra tor comprising a pair of electron disj charge devices each having a cathode, an anode and a control electrode, a connection joining said 4 cathodes, continuously conductive means for biasing said control electrodes, cross-couplings between the anode of one of said devices and the control electrode of the other of said devices and between the control electrode of said one device and the anode of said other device, tapped resistance means connected,- between said anodes, a source of direct-current potential and a resistance element connected in series between said connected cathodes and the tap on said resistance means, the negative terminal of said source being connected to said connected cathodes, and a load element connected across a portion of said resistance element, said cross-couplings and resistance means being chosen to provide a time constant sufiiciently great to cause the anode potential of each discharge device to rise substantially linearly throughout its own non-conducting periods.

4. A saw-tooth wave generator including a multivibrator comprisin a pair of electron discharge devices each having a cathode, an anode and a control electrode, a connection joining said cathodes, individual resistive means for biasing each of said control electrodes, cross-couplings between the anode of one of said devices and the control electrode of the other of said devices and between the control electrode of said one device and the anode of said other device, tapped resistance means connected between said anodes, a source of potentialand a resistance: element connected in series between 'said:connected cathodes and the tap on said resistance means, and a load element connected across a portion of said re* sistance element, said cross-couplings and resistance means being chosen to provide a time constant sufiiciently great to cause the anode poten- 'tial of each discharge device to rise substantially linearly throughout its own non-conducting periods.

5. A saw-tooth wave generator including a multivibr'ator' comprising a pair-of electron discharge devices, each having a cathode, an anode, and a control electrode, a'connection joining said cathodes, cross couplings-between the anode of one of said devices and the control electrode of the other of said devices and between the control electrode of said one device and the anode of said other device, each of said cross couplings including a capacitorya source of anode potential, a

connection between the positive terminal of said source of potential and each of said anodes including resistance means common to both anode circuits, and an output circuit connected across a portionofisaid common resistor, the capacitance of eachof said capacitors and the resistance of said resistance means being chosen to provide a time constant sufficiently great to cause the anode'potential'of each discharge device to rise substantially linearly throughout its own nonconducti'ng periods. I FRANK H. 'SLAYMAKER.

' WILLARD F. MEEKER;

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

UNITED STATES PATENTS Morton et al.v Oct. 22, 1946

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