Patented July 7, 1953 I 2,644,896 UNITED STATESVPAITENT OFFICE ~ Arthur W. Lo, Haddonñeld, N. J., 'assignor to Radio Corporation ofAmerica, a, corporation of Delaware i Application July 29, 1952, serial No. 301,557 9 Claims. 1 ~ (c’l. soi-ss) f This invention relates generally to triggered circuits, and particularly relates to a bistable of the defects of prior art bistable transistor cir cuits. By providing substantially zero impedance transistor circuit employing a single currentmultiplication transistor. ` ' f _ in the external base circuit during the low cur rent conduction state, the emitter current-emitter voltage curve is caused to pass through the origin of the coordinates.A However, this circuit is com ` Various transistor circuits are known which employ a single current-multiplication transis paratively complicated and'may still require ad justment of the circuit parameters to compensate tor to provide, for example, bistable triggered cir cuits. Such a circuit `has been disclosed and claimed in the patent to Eberhard 2,533,001. The for the differences of the characteristics of indi patent to Rack 2,579,336 discloses and claims‘a 10 vidual transistors. ‘ stabilized transistor triggered circuit which’rnay It is accordingly an object of the present inven be operated so as to have two 'stable states of tion to provide a bistable transistor triggered cir cuit employing a. 'single current-multiplication transistor which is highly reliable in operation. The latter `patent indicates that available transistors exhibit considerable diiïerences in 15~ A furth-er object of the invention is to provide their characteristics such, for example, as the a; bistable transistor circuit of the `type referred emitter current vs. emitter voltage characteris to which will operate with ñxed `circuit constants tic. Consequently, many of the prior art transis regardless of differences of the characteristics of tor triggered circuits require adjustment of the individual transistors used therein. ' ‘ ' circuit constants to compensatefor the different 20 Another object of the invention is to provide operation. ' ` - » characteristics of each individual transistor. V`The bistable operation of a single transistor triggered circuit depends on the negative resistance char acteristic which appears looking into the emit ter. The emitter characteristic contains a nega a bistable transistor circuit which is non-critical as to the power supply voltages and which eiîec tively provides a high impedance in the emitter circuit so that trigger pulses may readily be im 25 pressed on the emitter.V tive resistance portion bounded at either end by a positive resistance portion. ' In order to obtain ` The bistable circuit of the present invention in cludes a current-multiplication transistor, that is, a circuit having two stable states of operation, it a transistor where the collector current incre is necessary to provide a resistor load in the ments are larger than corresponding emitter cur emitter circuit which may be represented as a 30 rent increments. An external network intercon load line intersecting the emitter characteristic nects the transistor electrodes with a common junction point such as ground and includes a base Consequently, in order to operate transistors of impedance element and a collector impedance widely varying characteristics so as to provide two element which serves as the output load. The stable states of current conditions thefcircuit 35 base impedance element may be a resistor and provides for regeneration as explained in the parameters must usually be selected so .thatthe individual emitter current vs. emitter voltage Eberhard patent referred to. ’ once in each region, that is, three times. A " ' curves match each other as closely as possible. In accordance with the present invention, the The external emitter resistance must be chosen to emitter is connected to the common junction obtain a load line intersecting the characteristic 40 point through a non-linear resistance device such, at three points. The load line may be shifted for example, as a rectiñer. The rectifier is poled without changing its slope by providing a suit in such a manner that it is biased in the non able emitter bias voltage. :From these consider- ‘ conducting direction when the circuit is infits ations it will be obvious that the external emitter state of low current conduction and is biased in resistance must be smaller than the greatest slope 45 the conducting direction when the circuit is in of the negative portion of the emitter character its state of high current conduction. Conse istic andv that the emitter bias voltage must also quently, a load line, representing an operation be properly selected. Hence, normallythe exter characteristic ina graph, approaches infinity for nal emitter resistance must be small and the value the state of low current conduction and assumes of the emitter bias voltage is critical. Frequent 50 a small positive value for the high current kcon ly, it is desired to impress the'trigger pulse on duction state, ` Thus, it is made possible that the emitter and to that end, the emitter cir the load line may intersect practically any tran cuit should present a high impedance rather than sistor characteristic at three points, `to assure a low impedance. ‘ ~ The Rack circuit is intended to overcome some 55 bistable operation. » . Preferably, the emitter bias is provided by ap 2,644,896 plying a voltage to the base so that the load line, in the graph referred to, intersects the origin of the coordinates of the emitter' characteristic. The novel features that are considered charac teristic of this invention are set forth, with par ticularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in oon nection with the accompanying drawing in which: - v Figure 1 is a circuit diagram of a bistable transistor triggered circuit embodying the present invention; ' Figure 2 is a graph illustrating the emitter voltage plotted as a function of rthe emitter cur rent; and 4 poled to become conducting upon the arrival of a positive trigger pulse 26. A succeeding negative trigger pulse shown at 30 is applied to input ter minals 3l, one of which is connected to base I4 through crystal rectifier 32. Rectifier 32 is poled to become conducting upon the arrival of a nega tive trigger pulse 30. , The operation of the bistable circuit of Figure l’will now be explained in connection with Figure 2. Curve 35 of Figure 2 illustrates a representa tive characteristic of a transistor and shows the emitter voltage Ve plotted as a function of the emitter current Ie both of which have been in dicated in Figure 1. A study of a number of 15 representative transistors has revealed that their characteristics generally fall into the shaded area contained between curves 35 and 38. Conse quently, in order to obtain bistable operation it is necessary to provide a load line which will inter Figure 3 is a circuit diagram of a modified triggered circuit in accordance with the inven 20 sect either curve 35 or curve 36 at three points. In accordance with the present invention, the tion. v load line is represented by the straight lines 31 Referring now to the drawing in which like ele and 38. Line 31 represents a very high resistance, ments are designated by the same reference which is determined by that of rectifier 25 when characters throughout the figures, and particu larly to Figure l, there is illustrated' a bistable 25 biased in the non-conducting direction. On the other hand, line 38 represents a very low resist triggered circuit including a transistor I0. Tran ance, which is determined by the resistance of sistor I0 should be a current-multiplication tran rectifier 25 when biased in the conducting direc sistor and may, for example, be a point contact tion. It will now be seen that load line 31, 38 in. transistor, that is, a transistor of the type where the emitter and collector electrodes are both in 30 tersects curve 35 at points A and B, which repre sent stable operation as well as at point C repre rectifying contact with the semi-conducting senting an unstable point of operation. The same body II. The body I I may consist of a semi-con load line 31, 38 intersects curve 36 at the stable ducting material such as germanium and pref points D and E and at the unstable point F. erably is of the N type as will be assumed in the Hence, it will be obvious that for any transistor, following discussion. Emitter I2, collector I3 whose characteristic falls between curves 35. and and base I4 are in contact with body II. The 36, bistable operation may be obtained by means details of manufacture and the mode of opera of the load line 31, 3B. tion of a point contact transistor are well known Let it be assumed, for example, that the tran and need not be further described here. Base resistor I5 is connected between base I4 40 sistor circuit of Figure 1 is in its stable state of and a source of voltage such as battery IS having its negative terminal grounded. Battery IB may be bypassed for alternating currents by bypass capacitor I1. Collector resistor I8 is connected between collector I3 and another suitable source of voltage such as battery 20 having its positive terminal grounded. Battery 20 may also be by passed for alternating current by capacitor 2I. Battery 20 is poled to apply a bias voltage in the reverse direction between collector I3 and base low current conduction. Let it further be as sumed that its characteristic is represented by curve 35. The stable low-current operation is determined by point A. In order to trigger the circuit into its other stable state of high current conduction, it is necessary to apply a positive trigger pulse to the emitter, which must be of sufficient amplitude to carry the circuit beyond the point G. Instead of applying a positive pulse to the emitter, it is feasible to apply a negative trigger pulse such as shown at 30 to base I4 or to apply a negative trigger pulse to collector I3. I4, while battery I6 is poled to apply a bias volt age in the forward direction between emitter I2 As soon as the emitter voltage or current passes and base I4. beyond the point G, the circuit will snap over to An output signal may be derived across collec tor resistor I8. To this end, a pair of output 55 its other stable point B. It may be noted from Figure 2 that during the terminals 22 is provided, one of which is grounded, state of low current conduction the emitter volt while the other one is coupled through coupling age Ve is positive with respect to ground. How capacitor 23 to collector I3. The transistor circuit described so far is con ventional. In accordance with the present in vention, the emitter I2 is grounded through a non-linear resistance device such as rectiñer 25 which may, for example, be a crystal rectifier as shown. Rectiñer 25 should be poled in such a manner that it is nonconducting when emitter I2 is positive with respect to ground, which oc curs during the low conduction state of the cir cuit. ' ever, on the other hand, due to the small collector current which flows at that time, the base voltage Vb is still more positive with respect to ground so that the emitter voltage is actually negative with respect to that of the base. Consequently, during the state of low current conduction, rectifier 25 is biased in the non-conducting direction. During the state of high current conduction corresponding to point B on curve 35 the emitter voltage Ve becomes negative with respect to ground so that rectifier 25 is biased in the con As will be more fully explained hereinafter, the circuit may, for example, be triggered by apply 70 ducting direction. At the same time, due to the large collector current flow, the base voltage Vb ing trigger pulses of alternately opposite polarity has a larger negative value so that the emitter to the base I4. To this end, a positive trigger has a positive voltage with respect to the base. pulse illustrated at 26 may be applied to input The circuit of Figure l may be triggered back terminals 21, one of which is connected to base I4 through a crystal rectifier 28. Rectifier 28 is 75. into its state of low current conduction by the *2,644,89e 5 application of a negative »pulse> to the emitter. from a high current conduction state toa low current conduction state.- A succeeding trigger Alternatively, a positive pulse such as pulse 26 may be applied to the base or a positive pulse can then be triggered again into its state of high pulse of negative polarity applied to base I4 vor to collector I3 will then- trigger the circuit from low current conduction’to high current conduc tion. Hence, the circuit of the Vinvention may be triggered either by applying trigger pulses of alternately opposite polarity to the same elec trode or by steering pulses of the same 'polarity current conduction either by applying a positive 10 in succession to different electrodes. may be applied to the collector. rIl‘hev trigger pulse must have such an amplitude that it will trigger the circuit past point I-I representing the minimum of curve 35 whereupon the circuit snaps back to its starting point A. tThe circuit pulse to emitter I2 or a negative pulse to the base I4. vThe operation of the circuit is exactly ' ¿bistable circuit which maybe triggered fromone ’state of stable operation` toA the ,other by means of trigger pulses. " The vcircuit is »substantially 15 insensitive to variations of the- supply voltages the same as described herein when the transistor characteristic corresponds to' curve 36 instead of to curve 35. ’ There has thus -been disclosed a-‘transistor ` While it will be understood that the circuit and may be operated with fixed circuit param speciiications of the bistable triggered circuit of the invention may vary according to the design for any particular application, the following cir eters in spite of widely varying characteristics» of individual transistors. The circuit of the invention is extremely simple and reliable in cuit speciñcations for the circuit of Figure 1 are 20 operation. included by way of example only: What isclaimed is: _ 1. A bistable triggered circuit comprising a Base resistor I5 _______________ __ohms__ 18,000 current-multiplication transistor including a Collector resistor I8 ____________ __do____ 5,600 semi-conducting body, a base electrode, an` Battery I6 _____________________ __volts__ +45 Battery 2D _____________________ __do____ -45 25 emitter electrode anda collector electrode in Representative values of the emitter current Ie, collector current Ic, base current Ib, emitter voltage Ve, collector voltage Vc and base voltage Vb (as indicated in Figure 1) are given below for 30 contact with said body, an external circuit net-. Work interconnecting said electrodes with a com mon junction joint and including a ñrst imped-` ance element connected between said base elec trode and said junction point, any output sec high current conduction state. ond impedance element connected between Said collector electrode and said junction point, both the low current conduction state and the ' High Current Con- Low Our~ rent Con duction . duction State State means serially connected with said first and sec ond impedance elements for applying a bias 35 voltage in the reverse direction between said collector and base electrodes, a non-linear re sistance device connected between said-emitter Emitter current L, _________________ _.ma.. +5. 2 -0. 0l Collector current Ic ________________ __ma.. Base current Ib ____________________ ._ma__ _7. 8 +2. 4 _2.1 Y +2. 0 Emitter Voltage VB .............. __volts._ Collector Voltage Vo ._ _._do___ -l. 0 _2. 8 +3. 6 -33. 0 Base Voltage Vb __________ __ do-.__ -1. 5 +5. 5 Collector-to Base Dissipation Einitter-to-Base Dissipation. _mw._ _mw_- 14 1 70 0 electrode and said junction point, and means connected between said emitter and collector 40 electrodes for applying a bias voltage in the vfor- j ward direction between said emitter and» base electrodes, said circuit thereby having a stable ' state of low current conduction and another Collector Power Supply_ _ __ _ __ _mw_ _ 350 90 stable state of high current conduction, and said Base Power Supply ________________ ._mw__ 110 90 device being connected so as to have a relatively 45 high resistance while said circuit is in said state Instead of: applying alternately positive and of low current conduction and to have a rela negative pulses to one of the electrodes of the tively low resistance while said circuit is in said transistor, it is also feasible to apply pulses of state of high current conduction. ` the same polarity alternately to different elec 2. A triggered circuit as defined in trodes. This will now be explained in connection 50 wherein said ñrst impedance element with Figure 3. To this end, input terminals 40 may be provided, one of which is grounded, while 3. A triggered circuit as deñned in the other one is coupled to emitter I2 through" wherein said output second impedance sistor. coupling capacitor 4I. Another pair of input is a resistor. ` , ` ` claim .1 is a. re ' claim 1 element l terminals 42 may be provided, one of which is 55 4. A triggered circuit as de?ned in claim 1 grounded, while the other one is coupled through wherein means is provided for applying trigger capacitor 43 to base I4. Finally, input terminals pulses to at least one of said electrodes. 44 may be provided, one of which is grounded, 5. A triggered circuit as deñned in claim 1 while the other one is coupled to collector I3 wherein said non-linear vresistance device isa 60 rectifier. through coupling capacitor 45. ' As explained hereinbefore, a »positive pulse 6. A bistable triggered circuit comprising a applied through terminals 40 tofemitter I2 will current-multiplication transistor including a trigger the circuit of the invention from .the state semi-conducting body, a base electrode, an emit of low current conduction to the state of high ' ter electrode and a collector electrode in contact If a succeeding trigger 65 with said body, an external network intercon current conduction. pulse of positive polarity is applied to input ter minals 42, a positive pulse is applied to base I4 which will trigger the circuit from a state of high necting said electrodes with a junction point and including a resistor connected between said base electrode and said junction point, an output impedance element connected between said col` current conduction to a state of low current con duction. The same result is obtained ii“ a posi-- 70 lector electrode and said junction" point, a first y _ tive trigger pulse is applied through input termi source ofv voltage'serially connected with said impedance element between said collector elec trode and said junction point for applying a bias voltage in the reverse direction between said viously explained, this will trigger the circuit 75 collector and base electrodes, a second source of nals 44 to collector I3. _ On the other hand, it is also feasible to apply a negative trigger pulse to emitter I2. As pre 2,644,896 7 voltage serially connected with said resistor be tween said base electrode and said junction point for applying a bias voltage in the forward direc tion between said emitter and base electrodes, a rectifier connected between said emitter elec trode and said junction point, said circuit there by having a stable state 0f low current conduc tion and another stable state of high current conduction, said rectifier being poled so as to 7. A triggered circuit as defined in claim 6 wherein said rectifier is a crystal rectiñer. 8. A triggered circuit as defined in claim 6 wherein means are provided to apply trigger pulses of alternately opposite polarity to one of said electrodes. 9. A triggered circuit as deñned in claim 6 wherein means are provided to apply trigger pulses of the same polarity alternately to two be non-conducting when said circuit is in said 10 different ones of said electrodes. stable state of low current conduction and so as to be conducting when said circuit is in said stable state of high current conduction, and a pair of output terminals coupled across said im 15 Dedance element. >ARTHUR W. Lo. No references cited.
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