DE2018150A1 - Monolithically integrable flip-flop circuit - Google Patents

Description

German ITT Industries GmbH. H. Keller et al 35-2

78 Freiburg i .B., Hans-Bunte-Str. 19 16. ' April 1970

. . Pat.Mo/Th.

DEUTSCHE ITT INDUSTRIES GESELLSCHAFT LIMITED LIABILITY

FREIBURG I.B. -

Monolithically integrable flip-flop circuit

The invention relates to a monolithically integrable bistable Flip-flop circuit with two switching transistors, whose The emitters are at the circuit zero point, the bases and collectors of which are connected to each other via a cross and their collectors each via a resistor to operating voltage are connected.

Such a flip-flop circuit is shown in Fig. 1, wherein the two switching transistors with T1 and T2 and, the two Resistors are labeled R1 and R2. It should be noted that in Fig. 1 only the components necessary for the two switching states are drawn, i.e. those for Control of this flip-flop circuit necessary components are not shown, since such a flip-flop circuit with operated by a number of different control circuits can be.

Let us just refer to a monolithically integrated flip-flop circuit Reference is made to an appropriate control circuit in which the collector-emitter paths of the switching transistors are each the collector-emitter path of a control transistor is connected in parallel. The bases of these control transistors

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then the control voltage for switching the flip-flop circuit supplied via input capacities,

In this type of drive circuit there is also a so-called preparatory component, such as a the base and collector of the control transistor interconnecting resistor according to the French patent 1 548 137.

When designing such a monolithically integrable bistable flip-flop circuit with a view to the possible low power consumption, as is the case with some applications is required, this requirement can only be achieved if the resistors R1 and R2 have as high an impedance as possible be made. However, high-resistance resistances are disproportionate in monolithic integrated circuits a lot of space on the semiconductor wafer, so that one strives to avoid high-ohmic resistances as possible and where it is not possible to reduce their number.

The problem of high resistance is particularly noticeable then of great importance ^ if from such bistable flip-flop circuits a multi-stage frequency divider chain is interconnected, with. for example the one in the kHzöder The frequency of a crystal oscillator in the MHz range can be reduced to frequencies in the range of a few Hz target.

In those formed in a single semiconductor die Frequency dividers, the area of the high-ohmic resistors takes up a very considerable part of the available Place. The object of the invention is therefore daring to specify a flip-flop circuit, its resistance requirements is significantly reduced.

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This task is characterized by the at the beginning monolithically integrable bistable flip-flop circuit achieved in that the two resistors are connected in series a single working resistor connected to the operating voltage and a complementary additional transistor of the

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art replaces 4 «r« a, that - the emxtter of the additional transistor stood with the arbeitswider - the collector of the additional transistor is connected to the collector of one of the two switching transistors and the base of the additional transistor is connected to the collector of the other of the two switching transistors. An advantageous development of the invention is that a second complementary additional transistor is provided in such a way that its emitter with the emitter of the first additional transistor, that ate the base with the collector of one of the two switching transistors and that its collector with the collector of the other of the two switching transistors tied together

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in the latter case, the two mutually complementary transistors are a flip-flop half with their collector-emitter paths connected in series in such a way that the two collectors are connected to one another and the emitters of the supply Set transistors across the common working resistance Operating voltage are connected »

A further reduction in the resistance requirement of the invention Circuit arrangement can be achieved by that in an embodiment of the invention of the industrial resistance is replaced by a transistor connected as a constant current source. The transistor connected as a constant current source is therefore located in the emitter lead of the or the complementary additional transistors. Is purely formal the switching on of a transistor connected as a constant current source in the emitter lead of a transistor or in

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the common emitter lead of two transistors from Differential amplifiers are known per se.

The invention and advantageous refinements and developments will now be described in connection with the others in FIG Drawing shown. Figures explained and described in more detail and are characterized in the subclaims.

Fig. 2 shows the bistable flip-flop circuit according to the invention? ,

Fig. 3 shows the already mentioned development of the invention bistable flip-flop circuit;

FIG. 4 shows the development according to FIG. 3, expanded by one of the control circuits mentioned at the beginning. . : "

The bistable flip-flop circuit according to the invention shown in FIG. 2 consists of the two switching transistors T1 and T2, the emitters of which are connected to the circuit zero point. The bases and the collectors of the two switching transistors are cross-connected with each other, so that the feedback necessary for working as a bistable flip-flop circuit results. Those usually provided in known circuits both resistors R1 and R2 (see. Fig. 1) are now in the inventive way by the series connection of the Working resistance R and the grain to the switching transistors * Plementary additional transistor T3 replaced. Here lies the Resistance R on the one hand at the operating voltage and on the other hand at the emitter of the additional transistor T3, while the collector of the additional transistor T3 to the collector of one Switching transistor Tl and the base of the additional transistor T3 connected to the collector of the other switching transistor T2 is. The output pulse is sent to one of the collectors of the Switching transistors removed.

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The surprising and novelty of the circuit according to the invention. consists in that the · otherwise in bistable flip-flop circuits The usual symmetry of the structure of each flip-flop half is left and the bistable behavior nonetheless is not lost as a result.

The mode of operation of the circuit according to FIG. 2 is as follows briefly explained. In one switching state, the transistors T2 and T3 are turned on, while transistor Tl is blocked is. The collector current of one of the two transistors T2 and T3 thus flows into the base of the other. In the other stable switching state, transistor Tl is turned on and receives its base current via the base and its. Collector current via the collector of the additional transistor T3, while the switching transistor T2 is blocked. In addition to the aforementioned possibility of taking the output pulse on In this circuit, the collector of each switching transistor can also have the output pulse at the emitter of the additional transistor T3 decreased; will.

To improve the operational safety of this circuit is it is particularly useful if the current gain of the additional transistor T3 is smaller than that of the switching transistor Tl. This; Requirement can be with monolithic realization the flip-flop circuit according to the invention can easily be achieved by using npn transistor structures as switching transistors and a lateral pnp transistor structure can be used for the additional transistor T3.

While the bistable flip-flop circuit according to the invention 2 has an asymmetrical structure in its entirety and thus the voltage drop across the load resistor R is dependent on the switching state of the flip-flop, shows the

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Fig. 3 shows a symmetrically constructed flip-flop circuit below Application of the underlying knowledge of the invention. Here, the circuit according to FIG. 2 is supplemented by a further complementary additional transistor T4, with its Emitter with the emitter of the first · additional transistor T3 and with the. Working resistance R-connected, furthermore its base with the collector of a Sctialttransistor Tl and its collector with the collector of the other switching transistor T2 is connected. With this circuit are either the transistors T1 and T4 or the transistors T2 ■ t and T3 controlled or »blocked, via the working resistance In every stable switching state, R is the sum of the collector and base currents of one of the two switching transistors T1 or T2. The voltage drop across the load resistor R is therefore approximately constant, so that this circuit variant has a somewhat lower operating voltage gets by as the circuit according to FIG. 2.

The knowledge on which the invention is based, each flip-flop = Only to provide the level with a single work banner, can also be used advantageously · if there are several to form a frequency divider chain use interconnected flip-flop stages. • In the case of a circuit with two additional transistors, leave it In particular, several flip-flop stages operate on a single working resistor, which in terms of the space utilization of the semiconductor wafer is even more favorable Relationships result.

In FIG. 4, the circuit of FIG \ 3 with all shown for switching from a convenient in the other stable state switching elements. As already mentioned at the beginning, the collector-emitter path of a control transistor T21 and T22 of the same conductivity type is associated with the collector-emitter path of the switching transistors T1 and T2

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connected in parallel. Each base of the control transistors lies via a capacity Dl, D2 at the control input S. These capacities with monolithic integration usually consist of the capacitance of a pn junction.

The additional transistors are labeled T41 and T42 in FIG. 4. Furthermore, the auxiliary transistors T31 and T32 are drawn in, which ensure that during the switchover the information about the previous switching status remains stored in the input capacitors. The auxiliary transistors are complementary to the control and switching transistors, i.e. they have the same conductivity type as the additional transistors T41 and T42.

The collector-emitter path of each auxiliary transistor T31, T32 is. the base-collector path of the control transistor connected in parallel in such a way that the emitter of the Auxiliary transistor connected to the collector of the control transistor is ,, while the collector of the auxiliary transistor is at the base of the control transistor.

The base of the auxiliary transistor is with the base of the same Switching transistor belonging to the flip-flop half, \ · possibly with the interposition of a resistor.

The advantage of the bistable flip-flop circuit according to the invention can be seen in the fact that with otherwise the same properties, the working resistance R is increased by a factor of 2 to 4 can be smaller than the sum of the resistances at previous-v known flip-flop circuits. With monolithic integration therefore, significantly less crystal area is required. If only the active components of the Flip-flop circuit needs to be integrated, the integrated Circuit no additional connection for the

Claims (6)

Η. Keller et al 35-2 CLAIMS. 1. Monolithically integrable bistable flip-flop circuit with two switching transformers, the emitters of which are at the circuit zero point, their bases and collectors in each case are cross-connected and their collectors are each connected to the operating voltage via a resistor are, characterized in that the two resistors (Rl, R2) by the series connection of a single working resistor (R) connected to the operating voltage and a complementary additional transistor (T3) are replaced in such a way that the emitter of the additional transistor with the working resistor, the collector of the additional transistor with the collector of one (Tl) of the two switching transistors and the base of the additional transistor is connected to the collector of the other (T2) of the two switching transformers. 2. Flip-flop circuit according to claim 1, characterized in that the current gain of the additional transistor (T3) is smaller than that of the one switching transistor. (Tl). 3. flip-flop circuit according to claim 2, characterized in that the additional transistor (T3) in monolithic Integration consists of a lateral pnp transistor structure. 4. flip-flop circuit according to one of claims 1 to 3, characterized in that a second complementary additional transistor (T4) is provided in such a way that its Emitter with the emitter of the first additional transistor (T3), - 11 - 846/14 '- ** »- H, Keller et al 35-2 - ■ '■■ ■ '. * '-' that its base is connected to the collector of one (Tl) of the two switching transistors and that its collector is connected to the collector of the other (TZ) of the two switching transistors. 5 .. flip "flop" * attitude according to one of claims l; to 4, characterized in that the work resistance (R), as in another context with differentiators known / formed by a constant current source replaced transistor. 6. FliprFlop ^ circuit according to one ■ of claims 1 to 5, characterized dadureh / that the collector-emitter path of each switching transistor, the collector ~ emitter ~ path of a control transistor (T2i _r T22) of the same conduction type is connected in parallel / that each base of the control 'transistors via a capacitance (Di, D2) is connected to a control input (S) that each base-collector-imitter-path of the control transistors has the -collector-imitter-path of an auxiliary transistor (T31 / T32) in such a way that the emitter of the auxiliary transformer is connected to the collector of the control transistor, and that the base of each auxiliary transistor is connected to the base of the switching transistor of the same flip-flop aid. 7, frequency divider using bistable. Flip * Flop levels according to one of Claims 4 to 6, dadureh characterized / that several flip flop stages have a common Have work resistance.