DE2060504A1 - Circuit arrangement that can be integrated in a monolithic manner for controlling one or more transistors connected as elements that maintain a constant current - Google Patents

Description

German ITT Industries GmbH. , W. Kreitz et al 4-3-1

78 Freiburg i.B., Hans-Bunte-Str. 19 Pat.Mo/Wi/Th.-Fl

7th December 1970

Fl 658

Wf. --Gwcemplar I

I / ^ not changed Wertitn J

DEUTSCHE ITT INDUSTRIES GESELLSCHAFT LIMITED LIABILITY

FREIBURG I.B.

Monolithically integrable circuit arrangement for controlling one or more transistors that are switched as constant-constant elements

From the journal "IEEE Transactions on Circuit Theory", December 1965, pages 586 to 590, it is known to operate transistors or transistor structures as so-called constant current sources when appropriately controlled. Here, the transistor serving as a constant-current element, as _{indicated in FIG. 1 with the aid of the transistors T 0} and T ₃ , has its emitter connected to the live pole of the operating voltage source U_ and its base connected to a control circuit consisting of the transistor T_ and the Resistance R ₀ exists. The collector of the transistor T «, which maintains a constant current, is connected to a suitable point of any circuit arrangement to which the constant current is to be supplied, which is indicated in the figures by the arrowheads. In the known arrangement, the control circuit consists of one

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Transistor of the same 'conduction type, which is also connected with its emitter to the live pole of the operating voltage coil U _n , while its collector and base are directly connected to each other and are connected via a resistor R _n to the other pole of the operating voltage, which is shown in the figures is identical to the circuit zero point. The transistor T., which maintains a constant current, is controlled by its base being connected to the base of the control transistor T_ in an equal-current manner. As will be shown later, the current which can be drawn from the collector of the transistor T _{1, which maintains a} constant current, can now be adjusted by changing the resistance value R _0.

The use of such switched as current constant elements Transistors is very versatile. It is for example from the magazine "IEEE Journal of Solid-state Circuits ", June 1969, pages 110 to 123, especially page HS ff, known, in monolithically integrated circuits, such current-keeping transistors as decoupling elements use between individual switching stages au. Another Use of such constant current sources is known from the magazine "radio mentor", September 1967, pages 702 and 703? In this case, the transistor connected as a constant-current element serves as the collector resistor of another transistor a monolithic integrated circuit.

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Even with circuit arrangements made up of individual components in the usual way, ie in what is known as a discrete structure is the use of current-holding transistors already known, see the book "Siemens Semiconductor Switching Examples", April 1964, pages 57 and 58; this is a highly sensitive DC neutral amplifier, in which the collector resistance of an amplifier transistor is a transistor connected as a current-constant element serves.

Furthermore, it is known prior art to also operate a plurality of transistors connected as elements that maintain a constant current from a single control circuit. The individual leads of the base current constant retaining transistors are connected to each other, as is indicated in Fig. 1 by means of the transistors T to T_. From the Valvo manual "Integrated Circuits 1968", April 1968, page 171, the principle circuit diagram of a monolithically integrated multi-stage differential amplifier is known in which such a multiple constant current source is used as emitter resistors for the individual differential amplifier stages. Finally, a monolithically integrated multiple constant current source has become known from the Swiss patent specification 484 521, which corresponds to the German laid-open specification 1 911 934 and the French patent application 2 012 426

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Transistors serving as collector resistances of bistable elements Multivibrator circuits are used.

As a control circuit in the multiple constant current source according to the last-mentioned Swiss patent is also a circuit arrangement is provided which corresponds to the control circuit according to Fig. 1 of the drawing, i.e. that with the Circuit of the transistor T and the resistor R essentially is identical.

Based on this prior art, the present invention relates to a monolithically integratable circuit arrangement for controlling one or more transistors or transistor structures connected as elements that maintain a constant current of the one type of conduction and the same or different emitter configuration, which are built up in discrete or integrated Circuits as a substitute for ohmic resistances, preferably as a substitute for high-value resistors, and their base-emitter paths in the case of several current-maintaining elements are connected in parallel in the same direction, which control circuit consists of a control transistor (structure) of one conductivity type, the base-emitter path of which is the Base-emitter path of the transistor that maintains a constant current (Transistor structure) is connected in parallel in the same direction and its collector is connected to its base and via a Collector resistance is connected to one pole of the operating voltage source.

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To explain the problem on which the invention is based and the object of the invention resulting therefrom, the mode of operation of the control circuit on the multiple constant current source will first be briefly explained with reference to FIG. For the sake of simplicity, it is assumed that the individual transistors or transistor structures T _Q to T are of the same emitter configuration, since in this case those in the transistors which maintain a constant current

T to T. flowing collector currents are equal to each other and in. ■

likewise the individual base streams. However, as expressed by the preamble of claim 1, the invention is not restricted to this same emitter configuration. If the emitter configuration is not the same, different currents depending on the configuration flow in the individual collector circuits, so that in this way a multiple constant current source can be produced , in the individual branches of which different currents can be provided as required.

The graphical representation of Fig. 1 is chosen so that the connection point of the base of the control transistor T _Q with the common base terminal of the current-maintaining transistors T- to T is referred to as the connection point A or first connection point _Q and the collector resistance with D or as the second connection point.

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The following simple relationships apply to this circuit in DC operation. A voltage drops across the resistor R which is equal to the operating voltage U "minus the base-emitter voltage U of the control transistor T_. The collector current I flows in the collector circuit of the control transistor T _Q , while the total base current of all transistors T to T flows in the connecting line between the connection points A and D, which, in the assumed case of identical transistors, corresponds to (n + 1) times the value of an individual base current, ie the current (n + 1) I _{13 flows} . The resistance caused by the collector

Ji

When R _Q , the current I flowing is therefore equal to the sum of the currents flowing to the connection point D; and, based on Ohm's law, the following easily understandable equations apply:

j _{= I + (n + 1) I} _ Χ _ ^Ü B - ^U BE R ₀ C ₀ BR ₀ R ₀

For the collector current I of the control transistor T _Q this results in:

U_ - U

I = _ (n + l) I_

^C O ^R O ^B

The collector current of the control transistor T _Q is, however, with its base current via the direct current gain factor B in the emitter circuit according to the equation

I _n β ^C O

O ~ ₇ _

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linked, which incidentally also applies to the link between the base and collector current of the constant-current transi- • disturb T. to T applies in the same way. The equation for the collector current of the control transistor can therefore also be in the following Form to be written:

T ^U B ' ^U BE

'OR ₀ (1 +

However, since on the other hand, under the above-mentioned condition, the collector currents of the individual transistors are also identical to one another, ie, I_ = I = I = I , this equation gives the in each collector circuit of the

η
Transistor flowing on.

As mentioned briefly at the beginning, this current can be adjusted _{by means of the resistance value of the collector resistor R Q.} However, it does not depend solely on this value, but also on the number η of the transistors serving as elements that maintain a constant current and their direct current amplification factor B. W

There are applications in which the task arises, circuits or circuit units with a certain To supply minimum current, which must not be fallen below. Since the parameters individual discrete transistors or with monolithic integration

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Gration that the transistors T _Q to T are subject to manufacturing fluctuations overall, which is particularly noticeable in different values of the direct current _{gain factor B, when dimensioning the resistor R 0} one must proceed in such a way that one assumes a most unfavorable value for the direct current gain factor B and the associated one Resistance R calculated.

In particular, the manufacturing tolerances cause the monolithic Integration of fluctuations in the direct current amplification factor B of the individual production batches, so that when dimensioning according to the lowest DC amplification factor B in circuits with a higher B a larger collector current flows, than is actually necessary. This leads to an unnecessarily high power consumption with the entire (integrated) circuit equipped device, which is particularly important if the charge is limited by means of a dry battery for a longer period of time Devices have a very detrimental effect on the life of the battery.

To solve this problem, according to the Swiss patent 484 521 the current-holding transistors are supplemented by a further transistor each, which ensures that the ratio (n + 1) / B given in the equation mentioned above remains significantly less than 1. However, as in this one Patent specification has already been carried out, this in turn has others

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Disadvantages, especially what the compensation of the temperature. coefficient concerns.

In addition to the current gain factor dependency explained in detail the setting of the individual collector currents, the known control circuit has the further disadvantage that the operating voltage Superimposed voltage fluctuations, for example that occurring during the long service life of a dry battery Slow drop in battery voltage, manifested as a change or fluctuation in the individual constant current transistors the flowing collector current noticeable.

It is therefore the object of the invention to reduce the current gain factor dependency and if possible also the voltage dependency of the setting in the collector circuits of the individual Constant current transistors eliminate currents flowing. Which refers to the current gain factor dependency of the setting The related part of the task can also be formulated in such a way that even with a large number (n + 1) the tran? sistors T_ to T and a relatively low DC gain factor B the ratio (n + 1) / B should always be small towards one.

This task is monolithic from the one detailed above integrable control circuit achieved in that the connecting line between the connection point of the base of the

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Control transistor with the base (s) of the (the) constant current Transistors, the first connection point, and the connection point the collector resistance is separated from the collector of the control transistor, the second connection point, da0 a DC control amplifier between the two connection points is switched, via the output of which the common current of the current-maintaining transistors (transistor structures) as well as the control transistor and only a fraction of this common base current flows through its input and that the DC control amplifier the potential at the second connection point with the potential of a reference voltage source with respect to a common reference point compares such that the potential difference between the potential of the second connection point and the potential of the reference voltage source becomes zero with respect to this common reference point.

Developments and embodiments of the invention Circuit arrangements are characterized in the subclaims and are now based on the further illustrated in the drawing Figures 2 to 7 explained in more detail.

Fig. 2 shows an embodiment of the invention in which the reference voltage source with the live Pole of the operating voltage source is connected,

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3 shows an embodiment of the invention in which the reference voltage source is at the circuit zero point connected,

FIG. 4 shows an embodiment of the basic circuit according to FIG. 2 in terms of circuitry.

Fig. 5 shows a circuit embodiment of the Basic circuit according to Fig. 3,

6 shows another embodiment in terms of circuitry the basic circuit of Fig. 3 and

FIG. 7 shows a further development of the circuit arrangement according to FIG. 6.

The circuit arrangement according to FIG. 2 consists of the current-holding one Elements switched transistors T. to T and the control transistor T_, which are in the same way with respect to their base-emitter paths are connected, as was described above in the explanation of FIG. To solve the der The problem underlying the invention is now in the connection line between the connection points A and D of the DC control amplifier V switched, via the output of which the common

Base current (n + l) I_, which gets as a constant-current element

switched transistors T _n to T and the transistor T_ flows

in υ

and via its input connected to the connection point D.

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only a fraction of this common base current flows. This fraction is given by the total DC gain factor ν of the DC control amplifier V. Furthermore, a second input of the DC control amplifier V is connected to the reference voltage source U_, the other pole of which is connected to the live pole of the operating voltage source U. The DC voltage control amplifier V has the property that it makes the potential difference between the connection point B and the potential of the reference _{voltage source U f} with respect to the common reference point, in this case with respect to the live pole of the operating voltage source U, to zero.

By interposing this special DC control amplifier, the influence of the factor (n + l) / B in the above equation is reduced by the total DC gain factor ν of this amplifier, so that fluctuations in the current gain factor B of the individual transistors or the integrated circuits of different production batches no longer have any influence the choice of the resistance value of the collector resistor R _{Q of} the control transistor T_ can have. Rather, the resistance value provided for a minimal power consumption can be selected, since the manufacturing and specimen variations have practically no influence on the voltage U_ dropping across the collector resistance R.

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The circuit of Fig. 3 corresponds in the intermediate circuit of the DC variable-gain amplifier V between the "connection points A and D to that of Fig. 2, however, the reference voltage source U instead of the live pole of the operating voltage source U _SS connected to the circuit zero point. In this case, the DC control amplifier V has the property that it makes the potential difference between the connection point B and the reference voltage U _f with respect to the circuit zero point. In this case, too, the current reduction, which is essential to the invention, by the total current gain factor ν of the DC control amplifier V. is an additional advantage of this embodiment of the invention consider the fact that operating voltage fluctuations or long-term changes in this voltage no longer affect the collector currents of the transistors T to T, which are to be kept constant.

1 η

rivers.

FIG. 4 shows a circuit arrangement which represents an embodiment of the basic circuit according to FIG. 2. The DC control amplifier consists of the two transistors T and T. The transistor T _x . is of the same line type

^v l ^V 2 ^V l

like the control transistor T_ and the transistors T ₁ to T, which maintain constant a current, while the transistor T "is complementary to these transistors. In an embodiment of the invention, the base-emitter path of the transistor T _{v is used} at the same time

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as reference voltage source U _f , which results in a considerable simplification of the circuit. The emitter of this transistor is connected to the live pole of the operating voltage _{source U n} , while its base is connected to the connection point D of the collector resistor R and the collector of the control transistor T ₀ . The collector of the transistor T "is with the

^v l base of transistor T galvanically directly connected, its

^V 2
The emitter is connected to the circuit neutral point and its collector is connected to the connection point A, that is to say the common base connection of the transistors T-, to T. The overall

u η

is the current gain factor ν of this DC control amplifier equal to the product of the current amplification factors B and B of the transistors T-. and T. In the base line of the trans-

^V l ^V 2
sistor T _v therefore flows the base current (n + 1) I / BB.

FIG. 5 shows a circuit arrangement which corresponds to the basic circuit according to FIG. 3. The DC control amplifier V consists of the transistors T _v and T., the transistor

^V 3 ^V 4

T "of the same conductivity type as the control transistor T _n and the ^V 4 ^u

constant current holding transistors T to T and the transistor

ι η

T .. is complementary to these transistors. In this execution

The base-emitter path of the transistor T " as a reference voltage source, the emitter of this transistor being connected to the circuit zero point, while its base is connected to the collector of the control transistor T and the collector resistor

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stood R _Q , i.e. connected to the connection point D. The collector of the transistor T is connected to the base of the transistor

3
T .. galvanically directly connected, whose emitter is connected to the voltage

^V 4
the leading pole of the operating voltage _{source U e is} connected,

while its collector is galvanically connected directly to the common base terminal of the transistors T ^ to T and on the other hand via

O η

a resistor R ^ is connected to the circuit neutral point. The total current amplification factor ν of this DC control amplifier is, if the current flowing through the resistor B ^ is neglected, equal to the product of the current amplification factors B and B. of the transistors T *. and T _v . Only the portion of the common base current of the transistors, reduced by this factor, therefore flows through the collector _{resistance R Q}

T_ to T.
On

The circuit arrangement shown in FIG. 6 is another variant of the basic circuit according to FIG. 3 _r in which the reference voltage U _{f is} connected to the circuit zero point. In this case, too, the base-emitter path of a transistor is used as a reference voltage source. In this variant, the DC control amplifier again consists of the transistor T _v , which is complementary to the transistors T _Q to T, and of a further transistor T _{x which is} complementary to these transistors. f ie the transistors T and T are of the same line

^V 5 ^V 3 ^V 5

type, but complementary to the transistors T _Q to T.

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The base-emitter line of the transistor T is the same

^V 3 manner connected as connected in the embodiment of Fig. 5, the collector leads electrically directly to the base of the transistor T, the collector is, however, via a resistor R ^ to the live pole of the operating voltage U _R. The emitter of the transistor T is at the circuit zero point, while

its collector directly galvanically with the common base connection of the transistors T_ to T is connected.

0 η

The resistor R ^ can still be the collector-emitter path of the

2
Transistor T are connected in parallel, the emitter of the

6th
Connect the transistor T to the live pole of the operating voltage.

6th
closed is. In the exemplary embodiments according to FIGS. 6 and 7, approximately the total base current (n + 1) I / BB, reduced by the product BB, flows in the base lead of the transistor T. B_ and B are the current gain factors of the transistors T and T.

The individual circuit arrangements according to the present invention have, in addition to the advantages already mentioned, the property; that they differ in terms of the temperature coefficient hold different. For example, the circuit arrangement according to FIG. 4 shows a positive temperature coefficient, while the Circuit arrangement c-n according to FIGS. 5 to 7 has a negative temperature coefficient exhibit. It is therefore depending on the special circuit in which the current-keeping transistors

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be applied, possible to choose a circuit that includes the overall circuit the temperature range to be expected during use. So it can be beneficial to a circuit to be used with a negative temperature coefficient, as the current gain factor is particularly important at temperatures around freezing point of transistors or transistor structures is highly dependent on current. For this reason, take the collector currents of the current-maintaining transistors at low temperatures, this can be done by the negative temperature coefficient in be balanced again to a certain extent.

The exemplary embodiments according to FIGS. 2 to 7 were explained on the basis of circuits in which the transistors which maintain a constant current are connected to the live pole of an operating voltage source _{U 0.} This corresponds in general to a use in which the transistors which maintain a constant current are used as collector resistors, ie in which the transistors which maintain a constant current are at a potential in the vicinity of the operating voltage. However, as is known from the above-mentioned Valvo manual, the current-maintaining transistors can also be used, for example, as emitter resistors of differential amplifiers. Then the current-maintaining transistors are at a relatively lower potential, usually even at a negative potential compared to the circuit zero point in the case of npn transistors as differential amplifier transistors. The individual variants of the control circuit with

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Appropriate switching of the reference voltage source can also be selected for this application so that depending on the desired Characteristic a positive or negative temperature coefficient and an additional voltage stabilization is obtained.

The control circuit according to the invention is particularly useful in circuits who work with small voltages and with small currents are advantageous. Such circuits are multi-stage, for example Frequency divider circuits consisting of flip-flop stages, such as those used in digital technology for memories, shift registers, and allocators etc. or how they are used in organs and in clocks controlled by a frequency standard can.

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Claims (8)

Fl 658 ιΛ W. Kreitz PATENT CLAIMS ' 1. Monolithically integrable circuit arrangement for controlling one or more transistors or transistor structures of one conduction type and the same or different emitter configuration / which are connected as constant-current elements / which are used in discrete or integrated circuits as a substitute for ohmic resistances, preferably as a substitute for high-ohmic resistors, and their base-emitters -Strains in the case of several current-maintaining elements are connected in parallel in the same direction, which control circuit consists of one (a) control transistor (structure) of the one conductivity type whose base-emitter path is the same as the base-emitter path of the current-maintaining transistor (transistor structure) is connected in parallel and its collector is connected to its base and connected to one pole of the operating voltage source via a collector resistor, characterized in that the connecting line between the connecting pu nkt. (A) the base of the control transistor (T) with the base (s) of the transistor (s) maintaining constant current (T .., T _3. »T), the first connection point, and the connection point (D) of the collector resistor (R _n ) with the collector of the control transistor (T _n ) / the second connection point, is separated, that between the two connection points (A, D) a constant - 20 - 209826 / 02JU 206050A Fl 658. W. Kreitz et al 4-3-1 Current control amplifier (V) is connected, via the output of which the straight base current of the current-maintaining transistors (transistor structures) (Τ _Ί , T ".. T) and the control 1 2. η transistor (T ") and its input only a fraction
this common base current flows, and that the DC control amplifier (V) compares the potential at the second connection point (B) with the potential of a reference voltage source (U _f ) with respect to a common reference point in such a way that the potential difference between the potential of the second connection point (B) and the potential of
Reference voltage source becomes zero with respect to this common reference point. 2. Circuit arrangement according to claim 1, characterized in that one end of the reference _{voltage source (U f} ) is connected to the live pole of the operating voltage source (U) (Fig. 2). 3. Circuit arrangement according to claim 1, characterized in that one end of the reference voltage source (U, -) with the Circuit neutral is connected (Fig. 3). 4. Circuit arrangement according to one of claims 1 to 3, characterized in that the base-emitter diode is used as the reference voltage source a transistor (transistor structure) is used. - 21 - 209826/024 "; - 21 Fl 658 W. Kreitz et al 4-3-1 5, circuit arrangement according to claims 2 and 4, characterized in that the base of a transistor (transistor structure) (T _v ) of the one conduction type with the collector 1
gate of the control transistor (T), the emitter of this transistor is connected to the live pole of the operating voltage source (U _R ) and the collector to the base of a transistor (transistor structure) (T) of the other conductivity type and that its emitter is connected to circuit neutral and whose collector is connected to the first connection point (A) (Fig. 4). 6. Circuit arrangement according to claims 3 and 4, characterized in that that the base of a transistor (transistor structure) (T) of the other conductivity type with the collector ^V 3 gate of the control transistor (T_), the emitter of this complementary Transistor with the circuit zero point and its collector with the base of a transistor (T) of the one Line type is connected and that its emitter is live Pole of the operating voltage source (U) and its collector on the one hand via a resistor (Ry) on the circuit 1 zero point and on the other hand at the first connection point (A) is connected (Fig. 5). 7. Circuit arrangement according to Claims 3 and 4, characterized in that that the base of a transistor (tran- - 22 - 209826/0244 ■ "■ JL JL " ■ * Fl 658. W. Kreitz et al 4-3-1 transistor structure) (T) of the other conduction type with the ^V 3
Collector of the control transistor (T _n ), the emitter of this complementary transistor with the circuit zero point and its collector on the one hand with the base of a further transistor (transistor structure) (T) of the other conductivity type and on the other hand via a resistor [K. ) ^V 2 is connected to the live pole of the operating voltage source (U) and that the emitter of this further complementary transistor is connected to the circuit zero point and its collector is connected to the first connection point (A) (Fig. 6). 8. Circuit arrangement according to claim 7, characterized in that the base-emitter path of the control transistor (T) the base-emitter path of one (a) transistor (transistor structure) (T) of the one conduction type in the same direction ^V 6
is held in parallel, the collector of which is connected to the battery voltage-remote end of the resistor (R ^.) connected 2 (Fig. 7). 209826/0244 Blank page