Apparatus for providing a bandgap voltage reference

Abstract

The invention relates to a device (10) for providing a bandgap voltage reference. The device comprises a first circuit (20) for providing a first temperature voltage (PTAT) which is proportional to a current temperature, wherein the first circuit has two parallel current paths (21, 22), wherein a first diode element (23) is arranged in a first current path (21) of the parallel current paths (21, 22) and a second diode element (24) is arranged in a second current path (22) of the parallel current paths (21, 22); a second circuit (30) for providing a second temperature voltage (CTAT) which is complementary to the current temperature; an adjustment circuit (40) which is arranged for adjusting a voltage difference between the two parallel current paths (21, 22) of the first circuit (20); a current biasing circuit (50) which is arranged for controlling a ratio of a current flow through the first diode (23) and a current flow through the second diode (24), wherein the current biasing circuit (50) comprises a calibration circuit (60) which adjusts the ratio to a target value.

Description

TECHNICAL FIELD

[0001] The present application relates to a device for providing a bandgap voltage reference. BACKGROUND

[0002] Reference voltages with high precision, for example with a deviation of less than 1% from a target value, are required in a variety of products. Thus, reference voltages with high precision are required, for example, for precise voltage or current measurements or precise temperature measurements. The precision of the reference voltage must be constant over the service life of the product and also over varying temperatures here. In order to achieve this, techniques are used by means of which systematic errors and statistical errors in the circuit for generating the reference voltage are minimized.

[0003] One technique for providing a precise reference voltage is the use of a circuit for a so-called bandgap voltage reference. The technique used here is also referred to as "bandgap biasing". Here, a voltage is generated which is proportional to the current temperature. Such a voltage is referred to here as a Proportional-to-Absolute-Temperature, PTAT, voltage. In addition, here a further voltage is also generated which falls on the temperature curve. Such a voltage is referred to as a Complementary-to-Absolute-Temperature, CTAT, voltage. If the PTAT voltage and the CTAT voltage are, for example, added together, the deviations of the respective voltages based on the temperature are mutually compensated. Thus, a reference voltage can be provided which is largely independent of the temperature.

[0004] In such a circuit, it is common for the ratio of two currents through two diodes, for example the ratio of the respective emitter currents through bipolar transistors, to be known and to be set, preferably, to a reasonable value. This is achieved, for example, by using n+1 current sources of the same type. Thus, for example, the current through a first of the bipolar transistors is determined by n of the current sources and the current through a further bipolar transistor is determined by one further voltage source, in order to achieve a current ratio of n / 1.

[0005] However, the problem arises that, due to age-dependent effects or other effects, the ratio between the currents deviates from the originally intended value, which leads to a loss of precision in the reference voltage. In order to overcome this problem, the currents can be alternated between the different current sources, which can be achieved, for example, on the basis of a Dynamic Element Matching, DEM, method. In this way, deviations between the different current sources can be compensated.

[0006] However, the technique based on the matching of dynamic elements leads to the problem that different combinations of current sources also lead to different ratios between the currents flowing through the two diodes, for example, two bipolar transistors. This can thus lead to a deviation in the CTAT voltage and the PTAT voltage. This in turn leads to voltage jumps or spikes in the reference voltage, the so-called "voltage ripple". As a result, only a time-averaged correct reference voltage can be achieved with such a circuit. However, if the reference voltage is used for nonlinear signal processing, for example in an ADC, the temporally limited deviation of the reference voltage can lead to intermodulation disturbances. Therefore, such a deviation in the reference voltage is to be avoided. SUMMARY

[0007] The invention for a device for providing a bandgap voltage reference comprises a first circuit for providing a first temperature voltage proportional to a current temperature, wherein the first circuit has two parallel current paths, wherein a first diode element is arranged in a first current path of the parallel current paths and a second diode element is arranged in a second current path of the parallel current paths, a second circuit for providing a second temperature voltage complementary to the current temperature, and a current biasing circuit configured to control a ratio of a current flow through the first diode element and a current flow through the second diode element, wherein the current biasing circuit comprises a calibration circuit that adjusts the ratio to a target value.

[0008] The first circuit is thus a PTAT circuit. The first temperature voltage output by the first circuit is proportional to the current temperature. This means that the first circuit outputs a lower voltage as the first temperature voltage at a lower temperature than the voltage output by the first circuit as the first temperature voltage at a relatively higher temperature. The abbreviation PTAT stands for "proportional to absolute temperature" here. The current flow through the first current path and the current flow through the second current path are input here by means of the current biasing circuit The first diode element is thus connected in parallel with the second diode element. The ratio of the current flow through the first diode element and the current flow through the second diode element is predetermined by the current biasing circuit. The first temperature voltage is thus applied between the output contacts of the two diode elements.

[0009] The diode element is here an element having the electrical properties of a diode, in particular an element having the characteristic curve of a diode.

[0010] The second circuit is a CTAT circuit. The second circuit is provided for providing a second temperature voltage, which is complementary to the current temperature. Here, it is preferred that the second circuit is integrated into the first circuit, i.e. preferably using common components with the first circuit. Furthermore, it is preferred that the second circuit comprises a diode element, through which a predefined current is guided. The voltage drop over the diode of the second circuit corresponds to the second temperature voltage. In particular, the diode element of the second circuit is the second diode element of the first circuit. The second temperature voltage is a CTAT voltage, wherein the abbreviation CTAT stands for "complementary to absolute temperature". This means that the voltage value of the second temperature voltage is greater at low temperatures than at relatively higher temperatures. This means that the voltage value of the second temperature voltage decreases with increasing temperature.

[0011] The current biasing circuit is provided for controlling the ratio of the current flow through the first diode element to the current flow through the second diode element. As such, the current biasing circuit preferably comprises two inputs, i.e. two ports or input contacts, wherein a first input of the current biasing circuit is connected with the first current path and a second input of the current biasing circuit is connected with the second current path.

[0012] The current biasing circuit is a circuit which comprises a plurality of sources and which adjusts the ratio of the currents flowing through the first and second current paths to each other by assigning sources to the first and second current paths. As such, for example, X sources are assigned to the first current path and Y sources are assigned to the second current path. In this case, by way of example, the ratio is given as X:Y.

[0013] Here, the current biasing circuit is preferably dynamic, i.e. in successive cycles, the sources are assigned to the first and second current paths in different combinations, wherein, however, the ratio remains constant. In this way, an error is minimized, which arises due to the fact that the individual elements are not absolutely identical, for example have structural deviations from each other. The current biasing circuit is therefore a circuit which controls the ratio of the current flow through the first diode element to the current flow through the second diode element by means of averaging. As such, the current biasing circuit preferably comprises a dynamic element matching circuit, also referred to as DEM circuit, which enables a dynamic assignment of the sources.

[0014] The current biasing circuit comprises a calibration circuit which adjusts the ratio to a target value. This is achieved, inter alia, by balancing the individual sources of the current biasing circuit with each other, i.e. adjusting them to a common calibration value. If the individual sources of the current biasing circuit are balanced with each other, the ratio is thus also adjusted to the target value. Here, the ratio is a value which results from the number of sources assigned to the first current path in relation to the number of sources assigned to the second current path.

[0015] The dependent claims show preferred extensions of the application.

[0016] The current biasing circuit comprises a plurality of internal current paths, and is arranged for providing, in mutually successive periods, a current flow through a first diode element of the first circuit by a number X of the internal current paths, and a current flow through a second diode element of the first circuit by a number Y of the internal current paths, respectively, wherein different combinations of the internal current paths are assigned to the number X and the number Y in said mutually successive periods, and wherein the ratio of the current flows corresponds to a value which corresponds to the ratio of the number X to the number Y. Thus, each of the sources of the current biasing circuit is preferably one internal current path. Here, each of the internal current paths is arranged for ensuring the same amount of current flow, wherein, however, differences can occur between the currents of the individual internal current paths which are defined by the structure, by the temperature or by the aging. These differences are corrected by means of the calibration circuit.

[0017] In order to adjust the ratio to the target value, a number X of the internal current paths is assigned to the first current path. At the same time, a number Y of the internal current paths is assigned to the second current path. Since each of the internal current paths is arranged for ensuring the same current flow, a ratio of X:Y arises between the current in the first current path and the current in the second current path. This ratio remains the same in each of the mutually successive periods. Here, however, in each period, different ones of the internal current paths are assigned to the number X and to the number Y. This means that not always the same internal current paths are coupled with the first current path or the second current path. In this way, an error in the target ratio of the current flows is compensated in its time average. However, if a discrete point in time is considered, the ratio at this point in time can be wrong when no calibration is carried out. Therefore, the internal current paths are brought into mutual conformity by the calibration circuit, for example in such a way that the current flows through the individual current paths are brought into mutual conformity, i.e. are matched to each other, preferably are equalized.

[0018] It is preferred that the number of internal current paths of the current biasing circuit is greater than the number X plus the number Y and that the calibration circuit is arranged for calibrating one of the internal current paths to one calibration value in one cycle, which one of the internal current paths is neither assigned to the number X nor to the number Y in this cycle. This means that the calibration circuit is arranged for calibrating at least one of the internal current paths in one cycle, which at least one of the internal current paths is neither coupled to the first current path nor to the second current path. Since the internal current paths are reselected and assigned to the current paths with each cycle, it is made possible that at least one of the internal current paths is calibrated in each cycle. Thus, a pause between the individual cycles is not required for the calibration. Thus, the calibration can be implemented in the operation of the device.

[0019] Here, it is preferred that the calibration value corresponds to a reference current provided by a reference current source. Each of the internal current paths is arranged for ensuring that a determined current is guided through the internal current path. In the calibration, the current guided through the internal current path is adjusted such that it corresponds to the reference current.

[0020] It is preferred that each of the internal current paths here comprises an own internal current source. In the calibration, it is preferred that each of the internal current sources is adjusted in such a way that it provides a current corresponding to the reference current. It is preferred that the current biasing circuit thus comprises a plurality of current sources, wherein it is preferred that, respectively, the number X of the current sources is assigned to the first current path and provides a current through the first diode element and the number Y of the current sources is assigned to the second diode element in order to provide a current through the second diode element. Thus, the ratio between the current through the first diode element and the current through the second diode element is X:Y, which results from the number of respectively assigned current sources. Furthermore, the current biasing circuit comprises at least one further current source in one further internal current path, which at least one further current source is calibrated, in particular in such a way that it is balanced with the reference current source while the other current sources provide one current or a plurality of currents in the ratio X:Y. In each of the cycles, a different one of the internal current sources is calibrated. After a determined number of cycles, the calibration of the individual internal current sources is repeated. If each of the internal current sources has been calibrated to the reference current, i.e. adjusted to the reference current, the individual internal current sources of the current biasing circuit are identical to each other in that they provide the same current, i.e. the reference current. Since the assignment of the current sources to the first current path and to the second current path can be fixedly adjusted by means of the circuit matrix, the ratio is also adjusted to the desired target value.

[0021] Preferably, when different combinations of internal current paths are assigned to the number X and the number Y in cycles following one another, the internal current paths are assigned to the number X or the number Y according to a rotation principle or a random principle or another sequence. This means that the internal current paths are assigned to the first current path or the second current path, in particular in a predefined order or in a random order. The rotation principle is advantageous here, since a defined order is used. It is thereby ensured that each of the internal current paths and thus also each of the preferred internal current sources is aligned after a fixed number of cycles. Under the random principle, it can happen that the period of time until each of the internal current paths is aligned is greater than under the rotation principle. However, with the random principle, interference in a defined frequency range is avoided.

[0022] It is advantageous if the device comprises a regulation circuit, which is designed to regulate a voltage difference between the parallel current paths of the first circuit, wherein the regulation circuit preferably regulates the voltage difference to a target value of 0 volts. Thus, a voltage balance is carried out between two predefined points in the first current path and in the second current path. It is thereby defined at which point the first temperature voltage can be taken in one of the current paths. When the regulation circuit regulates the voltage difference to the target value of 0 volts, an optimum operating point for the first circuit is selected.

[0023] It is also advantageous if the regulation circuit comprises a control element and an amplifier, wherein the amplifier is coupled to the first circuit in such a way that the voltage difference is applied to the input contacts of the amplifier, and wherein the control element is designed to control the magnitude of the current flowing through the current biasing circuit or the output resistance of the current biasing circuit on the basis of the output voltage of the amplifier. Thus, a parameter is adjusted by the amplifier, which has a direct influence on the voltages present in the first current path and in the second current path. In this way, a defined operating point for the first circuit can be selected and manipulated. The control element is hereby preferably formed by a plurality of or all internal current sources of the current biasing circuit, wherein the internal current sources are controllable current sources.

[0024] It is preferred that, here, a resistance is arranged in one of the parallel current paths, in particular in the second current path. The current path also preferably comprises the second diode element. In this way, the resistance is preferably arranged in the second current path, so that a second temperature voltage is provided simultaneously by the second diode element, which second temperature voltage drops over the second diode element. In this way, in particular, the first current path comprises only the first diode element, and the second current path preferably comprises the second diode element and the resistance connected in series with the second diode element. The voltage difference adjusted by the adjustment circuit is preferably here the voltage difference applied between the input contacts of the current biasing circuit. It is also preferred that the voltage difference adjusted by the adjustment circuit is the voltage difference applied between the output contact of the first diode element and the contact of the resistance remote from the second diode element.

[0025] It is furthermore preferred that the first diode element and / or the second diode element is a diode or a transistor in a diode circuit, wherein in the diode circuit a diode is simulated by a transistor. In this way, the first diode element and / or the second diode element is provided in particular by means of an associated transistor in a diode circuit. The transistor is preferably a bipolar transistor here. BRIEF DESCRIPTION OF DRAWINGS

[0026] In the following, embodiments of the application are described in detail with reference to the attached drawings. In the drawings:

[0027] Figure 1 is a circuit diagram of a device for providing a bandgap voltage reference according to an embodiment of the application; and

[0028] Figure 2 is a schematic diagram of a mode of operation of the current biasing circuit. DETAILED DESCRIPTION

[0029] Figure 1 A circuit diagram of a device 10 for providing a bandgap voltage reference is shown. Here, in Figure 1 in particular a part of the circuit is shown, by means of which a first temperature voltage PTAT and a second temperature voltage CTAT are provided. The device 10 optionally comprises further components by means of which the first temperature voltage PTAT and the second temperature voltage CTAT are combined into a reference voltage, which reference voltage forms a voltage reference.

[0030] The device 10 comprises a first circuit 20, a second circuit 30, an adjustment circuit 40 and a current biasing circuit 50.

[0031] The first circuit 20 is arranged for generating and providing a first temperature voltage PTAT. The first temperature voltage PTAT is a voltage that is proportional to the current temperature. This means that with an increase of the current temperature a higher first temperature voltage PTAT is output by the first circuit 20.

[0032] The first circuit 20 comprises two parallel current paths 21, 22. In the first current path 21 of the parallel current paths 21, 22 a first diode element 23 is arranged. In the second current path 22 of the parallel current paths 21, 22 a second diode element 24 and a resistor 25 are arranged. The first diode element 23 and the second diode element 24 are here each provided by a bipolar transistor that is interconnected in diode operation. Here, the first diode element 23 and the second diode element 24 are each coupled with a first side to the supply voltage VDD. In this way, in particular the base and the collector of the transistor forming the diode elements 23, 24 are each coupled to the supply voltage VDD. In the first current path 21 the second side of the first diode element 23, i.e. the emitter of the transistor of the first diode element 23, is coupled to a first input of a current biasing circuit 50. In the second current path 22 the second side of the second diode element 24, i.e. the emitter of the transistor of the second diode element 24, is coupled via the resistor 25 to a second input of the current biasing circuit 50.

[0033] In order that the first circuit 20 is able to provide the first temperature setting PTAT, it is necessary that the ratio between the current flowing through the first current path 21 and the current flowing through the second current path 22 is known. This is achieved by the current biasing circuit 50 that is arranged for controlling the ratio of the current flow through the first diode element 23 and the current flow through the second diode element 24. In this way, for example, n times the current is directed through the first current path 21 compared to the second current path 22 and thus through the second diode element 24. Thus, the ratio is for example n:1.

[0034] The current biasing circuit 50 comprises a plurality of internal current paths 51-59. Here, the current biasing circuit 50 is configured to assign a number X of the internal current paths 51-59 to the first current path 21 and a number Y of the internal current paths 51-59 to the second current path 22 in each other successive period. Each of the internal current paths 51-59 of the current biasing circuit 50 comprises here an internal current source. Here, it is desirable that each of the internal current sources and thus each of the internal current paths 51-59 provides the same current. However, here, a structural or aging-defined deviation can occur. By the ratio of the number of the internal current paths 51-59 assigned to the first current path 21 and the number of the internal current paths 51-59 assigned to the second current path 22, a ratio of the current flow through the first diode element 23 and the current flow through the second diode element 24 is obtained. Thus, in the present embodiment, the number X is equal to the number n and the number Y is equal to one. Thus, X / Y = n / 1 applies.

[0035] Here, the current biasing circuit 50 comprises a circuit matrix 70 which connects the first current path 21 with a circuit ground via X, in particular n, of the internal current paths 51-59 and which connects the second current path 22 with the circuit ground via Y, in particular one, of the internal current paths 51-59. Here, the internal current sources 41 are arranged on an output side of the circuit matrix 70, wherein the number of the internal current sources 41 corresponds to the number of the internal current paths 51-59 of the current biasing circuit 50.

[0036] If the ratio is selected to be, for example, 7:1, a number of 7 of the internal current paths 51-59 is assigned to the first current path 21 and one of the internal current paths 51-59 is assigned to the second current path 22, respectively. Thus, 7 times the current flows through the first current path 21 and thus through the first diode element 23 relative to the current which flows through the second current path 22 and which flows through the second diode element 24.

[0037] In successive cycles, different combinations of internal current paths 51-59 are assigned to quantities X and Y, respectively. Thus, X internal current sources are assigned to the first current path 21 via the current bias circuit 50, wherein the same internal current paths 51-59 are not always assigned to the first current path 21. This applies correspondingly to the second current path 22, which is not always assigned the same internal current path among internal current paths 51-59. With each cycle, other internal current paths 51-59 are assigned to either the first current path 21 or the second current path 22. Here, it is preferable to assign internal current paths 51-59 to quantities X or Y, and thus to either the first current path 21 or the second current path 22, according to a rotation principle or a random principle.

[0038] Figure 2 Multiple internal current paths 51-59 of the current bias circuit 50 are illustrated exemplarily. Thus, in Figure 2 The diagram shows a first current path 51, a second current path 52, a third current path 53, a fourth current path 54, a fifth current path 55, a sixth current path 56, a seventh current path 57, an eighth current path 58, and a ninth current path 59. Each of the current paths 51-59 includes exactly one of the internal current sources 41.

[0039] Figure 2 An exemplary cycle is shown. Here, the first to seventh internal current paths 51-57 are assigned to quantity X and thus to the first current path 21. Furthermore, the eighth current path 58 is assigned to quantity Y and thus to the second current path 22. The internal current paths belonging to quantity X are connected in parallel here. Therefore, in Figure 2 In the cycle shown, seven times more current flows through the first current path 21 compared to the second current path 22. In subsequent cycles, other current paths among the internal current paths 51-59 are assigned to a quantity X. Thus, for example, the second to eighth current paths 52-58 are assigned to a quantity X and therefore to the first current path 21, and the ninth internal current path 59 is assigned to a quantity Y and therefore to the second current path 22.

[0040] However, here, in successive cycles, the ratio of the number of internal current paths allocated to the number X to the number of current paths allocated to the number Y remains constant.

[0041] If the current sources in the internal current paths 51-59 were to be so identical that these current sources would provide exactly the same current, then the ratio X:Y and thus the ratio of the current through the first current path 21 to the current in the second current path 22 would be exactly 7:1. However, due to aging of the current biasing circuit 50 or due to fluctuations defined by temperature, differences between the currents provided by the individual current sources in the internal current paths 51-59 can occur. Therefore, the current biasing circuit 50 comprises a calibration circuit 60 which adjusts the ratio to a target value. This is achieved in that the number of internal current paths 51-59 of the current biasing circuit 50 is greater than the number X plus the number Y, and the calibration circuit provides for calibrating one of the internal current paths 51-59 to the target value in a cycle, respectively, wherein the internal current path to be calibrated is neither assigned to the number X nor to the number Y in this cycle. In this way, for example, from Figure 2 It can be seen that in the cycle shown, the ninth internal current path 59 is neither assigned to the number X nor to the number Y. The ninth internal current path 59, which comprises the internal current source belonging thereto, is calibrated in this cycle. Here, the internal current source of the ninth internal current path 59 is adjusted in such a way that the current provided by this current source corresponds to the reference current I ref In cycles following one another, each of the internal current sources of the individual internal current paths 51-59 is thus adjusted in such a way that the current provided by the respective internal current source corresponds to the reference current I ref It is thus achieved that the same current is provided through each of the internal current paths 51-59. It is thus achieved that the ratio of the currents provided by the current biasing circuit 50 for the first current path 21 and the second current path 22 also corresponds to the ratio of the numbers of internal current paths of the current biasing circuit 50 which are assigned to the parallel current paths 21, 22.

[0042] In a corresponding way, from Figure 1 It can be seen that one of the internal current paths 51-59 is coupled to the calibration circuit 60, respectively, which provides the reference current I ref n of the internal current paths 51-59 are coupled to the first current path 21, and one of the internal current paths 51-59 is coupled to the second current path 22. It is thus achieved that the ratio of the currents provided by the current biasing circuit 50 for the first current path 21 and the second current path 22 corresponds to the ratio of the numbers of internal current paths of the current biasing circuit 50 which are assigned to the parallel current paths 21, 22. Figure 1The circuit shown in the middle has n+2 internal current paths, wherein exactly one of the internal current sources 41 belongs to each of the internal current paths. Here, preferably, n of the internal current paths 51-59 are assigned to the first current path 21, one of the internal current paths 51-59 is assigned to the first current path 22, and one of the internal current paths 51-59 is assigned for calibration of the calibration circuit 60 by the circuit matrix 70, respectively.

[0043] The regulating circuit 40 comprises an operational amplifier 42 and a control element 41. In the embodiment described, the control element 41 is formed by an internal current source 43, which is a controllable current source. The operational amplifier 42 is connected with its non-inverting input to the second input of the current biasing circuit 50 and thus also to the second current path 22. The inverting input of the operational amplifier 42 is connected to the first input of the current biasing circuit 50 and thus to the first current path 21. By means of the regulating circuit 40, the internal current source 43 is manipulated in the same way, and it is adjusted how much total current flows through the current biasing circuit 50. The regulating circuit 40 does not change the ratio between the current flow through the first current path 21 and the current flow in the second current path 22, since this ratio is defined by the ratio in terms of the number of the internal current paths 51-59 assigned to the first current path 21 and the second current path 22 by the circuit matrix 70. Since different current flows through the first current path 21 and the second current path 22, the voltage difference between the first current path 21 and the second current path 22 is balanced by means of the regulating circuit 40, since this depends on how much current flows in total through the current biasing circuit 50. This voltage difference is adjusted here to the target value 0 V. Here, the first circuit 20 is regulated into a predefined operating point, in which the first circuit provides the first temperature voltage PTAT.

[0044] The second circuit 30 for providing the second temperature voltage CTAT is formed by a second diode element 24. The second temperature voltage CTAT is complementary to the current temperature. This means that the second temperature voltage CTAT falls with rising temperature voltage.

[0045] The first temperature voltage PTAT can thus be measured via the resistor 25 or can be measured between the first current path 21 and the second current path 22. The second temperature voltage can be measured via the second diode element 24.

[0046] In addition to the above disclosure, explicit reference is made to the disclosure of Figure 1 and Figure 2 .

Claims

1. A device (10) for providing a bandgap voltage reference, the device comprising: - A first circuit (20) configured to provide a first temperature voltage (PTAT) proportional to the current temperature, wherein the first circuit has two parallel current paths (21, 22), wherein a first diode element (23) is arranged in the first current path (21) of the parallel current paths (21, 22) and a second diode element (24) is arranged in the second current path (22) of the parallel current paths (21, 22). - A second circuit (30) configured to provide a second temperature voltage (CTAT) complementary to the current temperature, wherein the second circuit is integrated into the first circuit and the voltage drop across the second diode element (24) corresponds to the second temperature voltage (CTAT), and A current bias circuit (50) configured to control the ratio of current flow through the first diode element (23) to current flow through the second diode element (24), wherein the current bias circuit (50) includes a calibration circuit (60) that adjusts the ratio to a target value, wherein the current bias circuit (50) includes a plurality of internal current paths (51-59), characterized in that the current bias circuit (50) is configured to respectively: - Current flow through the first diode element (23) of the first circuit (20) is provided by x internal current paths (51-59), and - Current flow through the second diode element (24) of the first circuit (20) is provided via a number of y internal current paths (51-59). In the successive cycles, different combinations of the internal current paths (51-59) are assigned to the quantities x and y, respectively. The ratio of the current flow corresponds to the following value: the value corresponds to the ratio of quantity x to quantity y.

2. The device according to claim 1, characterized in that, The number of internal current paths (51-59) of the current bias circuit (50) is greater than the number x plus the number y, and the calibration circuit (60) is configured to calibrate one of the internal current paths (51-59) to a target value in one cycle, wherein the one internal current path is not assigned to either the number x or the number y in this cycle.

3. The device according to claim 2, characterized in that, The target value corresponds to the reference current (I) provided by the reference current source (61). ref ).

4. The device according to any one of claims 1 to 3, characterized in that, Each of the internal current paths (51-59) includes an associated internal current source.

5. The device according to any one of claims 1 to 3, characterized in that, When different combinations of the internal current paths (51-59) are assigned to the quantities x and y respectively in successive cycles, the internal current paths (51-59) are assigned to the quantities x or y according to the rotation principle or the random principle.

6. The device according to any one of claims 1 to 3, characterized in that, The device (10) includes an adjustment circuit (40) configured to adjust the voltage difference between the parallel current paths (21, 22) of the first circuit (20).

7. The device according to claim 6, characterized in that, The adjustment circuit (40) includes a control element (41) and an amplifier (42). The amplifier (42) is coupled to the first circuit (20) in such a way that the voltage difference is applied to the input contact of the amplifier (42), and The control element (41) is configured to control the magnitude of the current flowing through the current bias circuit (50) based on the output voltage of the amplifier (42).

8. The device according to any one of claims 1 to 3, characterized in that, A resistor (25) is arranged in one of the parallel current paths (21, 22), and the current path (22) also includes the second circuit (30).

9. The device according to any one of claims 1 to 3, characterized in that, The first diode element (23) and / or the second diode element (24) are diodes or transistors in a diode circuit, wherein a diode is simulated by a transistor in the diode circuit.

10. The device according to claim 6, characterized in that, The regulating circuit (40) adjusts the voltage difference to a target value of 0 volts.

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