Abstract:
An arrangement for measuring the temperature of an electronic circuit, the arrangement comprising 
     a measuring element being in close thermal communication with the electronic circuit, which measuring element comprises a temperature-dependent component in each one of at least two current paths and whose current-voltage characteristic is dependent on the temperature in accordance with a different predetermined function in at least two of the current paths, which temperature-dependent components can each be impressed with a predetermined current for generating a voltage dependent on the temperature at each one of the temperature-dependent components, and 
     an evaluation circuit for forming an output voltage representing a measure of the temperature of the electronic circuit from the difference of the voltages at the temperature-dependent components. 
     By measuring the output voltage of the arrangement according to the invention, it is possible to measure the instantaneous temperature of the semiconductor body in a simple, rapid and accurate manner. The measured value of the temperature may be directly evaluated by means of an electronic signal processing operation, for example, in an apparatus for performing the pre-measurement.

Description:
FIELD OF THE INVENTION 
     The invention relates to an arrangement for measuring the temperature of an electronic circuit. 
     BACKGROUND OF THE INVENTION 
     In the manufacture of semiconductor circuits, particularly monolithically integrated semiconductor circuits, a test, denoted as pre-measurement, is usually performed after finishing the conductor structures on the semiconductor body and before incorporating the semiconductor body in a housing, so as to reject defective circuits before they are incorporated in the housing. Moreover, a classification or specification of the semiconductor circuits based on their operating data can be performed with this pre-measurement. A condition for a correct pre-measurement is the knowledge of the instantaneous temperature of the semiconductor body, because many measuring values are temperature-dependent. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an arrangement with which a measurement of the instantaneous temperature of the semiconductor body is possible in a simple, rapid and accurate manner. 
     According to the invention, this object is achieved by an arrangement for measuring the temperature of an electronic circuit, the arrangement comprising 
     a measuring element being in close thermal communication with the electronic circuit, which measuring element comprises a temperature-dependent component in each one of at least two current paths and whose current-voltage characteristic is dependent on the temperature in accordance with a different predetermined function in at least two of the current paths, which temperature-dependent components can each be impressed with a predetermined current for generating a voltage dependent on the temperature at each one of the temperature-dependent components, and 
     an evaluation circuit for forming an output voltage representing a measure of the temperature of the electronic circuit from the difference of the voltages at the temperature-dependent components. 
     By measuring the output voltage of the arrangement according to the invention, it is possible to measure the instantaneous temperature of the semiconductor body in a simple, rapid and accurate manner. The measured value of the temperature may be directly evaluated by means of an electronic signal processing operation, for example, in an apparatus for performing the pre-measurement. 
     Moreover, the arrangement according to the invention may also be used in the specifically defined operation of the electronic circuit for a continuous temperature observation. Measures for protecting the electronic circuit, for example, from overheating can then be taken in a very simple manner. 
     The temperature-dependent components are preferably formed with semiconductor diodes. These semiconductor diodes have a simple structure and can be provided in an electronic circuit without any additional manufacturing steps. Their temperature dependence is satisfactorily reproducible. 
     Particularly, the semiconductor diodes arranged in the different current paths are formed with different surfaces of their semiconductor junctions. This provides the easy possibility of manufacturing them in accordance with different predetermined functions of the temperature-dependent components without changing manufacturing parameters, for example, in the diffusion of the conductor structures of the semiconductor body of the electronic circuit. 
     In accordance with a further embodiment of the arrangement according to the invention, the temperature-dependent components are interconnected by way of a respective first one of their terminals, and their respective second terminals are connected to a device for impressing at least substantially identical currents. In accordance with the different temperature dependencies of the current voltage characteristics of the temperature-dependent components, different temperature-dependent voltages are generated at the temperature-dependent components, which voltage differences can be measured and evaluated easily and accurately. 
     Advantageously, the device for impressing at least substantially identical currents comprises a current mirror arrangement with which corresponding currents can be generated and supplied easily and accurately. 
     Advantageously, the interconnected first terminals of the temperature-dependent components are preferably coupled to a device for supplying a reference voltage. The measurement of the temperature-dependent voltages at the individual temperature-dependent components is performed with respect to this reference voltage. In particular, the reference voltage does not correspond to a ground potential provided by the electronic circuit at, for example, a ground conductor system in the electronic circuit, but the reference voltage is rather generated in a preferably separate temperature-stable manner. In accordance with an advantageous further embodiment of the invention, this can be achieved in that the device for supplying a reference voltage is formed with a bandgap reference from which the reference voltage is derived. By utilizing the reference voltage generated in a separate temperature-stable manner instead of the ground potential, inaccuracies in the temperature measurement, as may occur due to local fluctuations of the ground conductor system in the electronic circuit, are eliminated. 
     In a further embodiment of the invention, the evaluation circuit comprises 
     at least an inverter stage for inverting at least one of the temperature-dependent voltages at at least one of the temperature-dependent components, 
     at least a voltage combination stage for forming a voltage value which corresponds to the arithmetic mean value of at least one of the temperature-dependent voltages at at least one of the temperature-dependent components and at least one of the inverted temperature-dependent voltages at at least a further one of the temperature-dependent components, and 
     an output amplifier stage for amplifying and supplying the voltage value formed by the voltage combination stage as an output voltage representing a measure of the temperature of the electronic circuit. 
     This embodiment of the evaluation stage provides the possibility of determining the output voltage representing a measure of the temperature of the electronic circuit independently of indirect values such as the reference voltage and only by the dimensioning of the arrangement according to the invention. 
     In a further embodiment of the arrangement according to the invention described hereinbefore, in which the interconnected first terminals of the temperature-dependent components are coupled to a device for supplying a reference voltage, the evaluation circuit receives the same reference voltage for fixing its working point as the interconnected first terminals of the temperature-dependent components. This additionally enhances the accuracy of the temperature measurement. Moreover, the use of the internally generated reference voltage has the result that the components comprised by the arrangement according to the invention can be operated at optimal working points. As a result, the arrangement according to the invention operates to a very linear extent over a large temperature range. 
     In a further embodiment of the arrangement according to the invention described hereinbefore, 
     the electronic circuit, whose temperature is to be measured, is constituted as a monolithically integrated semiconductor circuit, 
     the measuring element and the evaluation circuit are combined with the electronic circuit constituted as a monolithically integrated semiconductor circuit on a semiconductor body, and 
     the electronic circuit constituted as a monolithically integrated semiconductor circuit comprises contacts for supplying and/or draining electric voltages and/or currents to and from the electronic circuit for supplying and draining power supply energy and/or signals, respectively, wherein 
     at least a first of these contacts is adapted to provide an output voltage of the evaluation circuit representing a measure of the temperature of the electronic circuit, and 
     at least a second contact provides the reference voltage applied to the temperature-dependent components at their interconnected first terminals as well as to the evaluation circuit for fixing its working point. 
     In this embodiment, the arrangement according to the invention is easily and directly usable for determining the temperature of the electronic circuit and for evaluating the measuring value of the temperature also outside the electronic circuit, for example, during a test of this circuit in a manufacturing process. 
     These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a block diagram showing the measurement of the temperature of a monolithically integrated electronic circuit formed with an arrangement according to the invention, 
     FIG. 2 shows an example of an embodiment of an arrangement according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, the reference IC denotes a monolithically integrated electronic circuit which is diagrammatically shown in a rectangular form with contact rows arranged on the sides symbolized in FIG. 1 by boundary lines shown in a perpendicular alignment. These contacts are used in the electronic circuit for supplying and/or draining electric voltages and/or currents to and from the electronic circuit for supplying or draining power supply energy and/or signals. An arrangement in accordance with, for example, FIG.  2  and described with reference to this Figure supplies an output voltage V temp  representing a measure of the temperature of the electronic circuit IC at a first of these contacts which is selected in FIG. 1, for example, as the second from the top in the contact row shown on the right-hand side of the electronic circuit IC. The same arrangement also supplies a temperature-constant reference voltage V ref  generated in the arrangement at a second contact which is selected in FIG. 1, for example, as the fifth one from the top in the contact row shown on the right-hand side of the electronic circuit IC. By simple voltage measurement, the difference between the output voltage V temp  representing a measure of the temperature of the electronic circuit IC and the reference voltage V ref  is determined. 
     The temperature of the electronic circuit IC is defined by the following                T   =         V   temp     -     V   ref       a       ,           [   1   ]                                
     wherein T is the absolute temperature of the electronic circuit IC and 
     a is a constant. 
     To determine the constant a, the following considerations are made hereinafter with reference to FIG.  2 . 
     The measurement of the voltage difference between the output voltage V temp  and the reference voltage V ref  by means of a voltmeter thus provides the possibility, after solving the linear equation [1], of rapidly and easily determining the instantaneous temperature T of the electronic circuit IC. 
     FIG. 2 shows an example of an arrangement with which the above-mentioned output voltage V temp  and the reference voltage V ref  are generated. The principle of the measuring method used in this respect will hereinafter be briefly elucidated before describing the components of the arrangement shown in FIG.  2 . 
     To be able to measure the temperature T, components are required whose electrical properties change with this temperature T. An electronic component which has this property is the diode. The operating behavior of a diode in the forward range for currents which are large with respect to their reverse saturation current can be defined by the following equations:                    I   =       I   S     ·            V   D       V   T                         V   T     =       k   ·   T     q                   [   2   ]                                
     In this equation, 
     I is the current intensity of the current through the diode, 
     I S  is the reverse saturation current of the diode, 
     V D  is the diode voltage measured in the forward direction of the diode, 
     V T  is the temperature voltage, 
     k=1,38*10 −23  J/K is the Boltzmann constant and 
     q=1,6*10 −19  C is the elementary charge. 
     When the above-mentioned diode equation [2] is converted to the diode voltage V D , the following equation is obtained:                V   D     =       V   T     ·     ln        (     I     I   S       )                 [   3   ]                                
     Since the reverse saturation current I S  of a semiconductor diode is proportional to the surface of its (P−N) junction, the relations                      V   D1     =       V   T     ·     ln        (     I     I   S1       )                       V   D2     =       V   T     ·     ln        (     I     I   S2       )                       [   4   ]                                
     are obtained from equation [3] for two diodes D 1  and D 2  with different surfaces. 
     In this equation, 
     I S1  is the reverse saturation current of diode D 1 , 
     I S2  is the reverse saturation current of diode D 2 , 
     V D1  is the diode voltage of diode D 1 , measured in the forward direction, 
     V D2  is the diode voltage of diode D 2 , measured in the forward direction. 
     In the practical embodiment of a monolithically integrated circuit, different diode surfaces are often obtained by parallel arrangement of a corresponding multitude of identical diode in conformity with the desired surface factor, i.e. the mutual ratio of the diode surfaces. 
     In the case considered, the reverse saturation currents of the diodes D 1  and D 2  can be determined by means of the equations 
     
       
         I S1   =I   S   [5] 
       
     
     
       
         
           I 
           S2 
           =x·I 
           S 
         
       
     
     in which 
     x is the surface factor, i.e. the mutual surface ratio of the diodes D 1  and D 2 . 
     When a (second) diode compared with a (first) diode with a predetermined surface has a surface factor x which is obtained, for example, in that the (second) diode consists of a diode field of x parallel arranged (first) diodes with said, predetermined surface, the diode voltage V T  will change accordingly with respect to that of the (first) diode with the predetermined surface when this (second) diode having the surface factor x is impressed with an unchanged current I. When these identical currents are supplied in the above-mentioned dimensioning of the diodes D 1  and D 2 , the following difference ΔV in the diode voltages is obtained:                      Δ                 V     =       V   D1     -     V   D2                   =         V   T     ·     (       ln        I     I   S1         -     ln        I     I   S2           )       =       V   T     ·     (       ln        I     I   S         -     ln        I     x   ·     I   S             )                     =           V   T     ·   ln                   x     =       T   ·         k   q        ln                 x          konst           _   _                       [   6   ]                                
     When, as shown in FIG. 2 at the diodes D 1  and D 2  in this Figure, two such dimensioned diodes are connected together by way of their cathodes, the difference ΔV in the diode voltages can be directly taken as a voltage difference from the anodes of the diodes. 
     The voltage difference ΔV between the diodes D 1  and D 2  described hereinbefore (for example, diodes D 1  and D 2  in FIG. 2) is dependent on the surface factor x and the temperature voltage V T  which, as is evident from equation [2], is directly proportional to the absolute temperature T. The voltage difference ΔV is thus also directly proportional to the absolute temperature T. 
     The arrangement shown in FIG. 2 utilizes this temperature dependence and provides the possibility of determining the absolute temperature of the electronic circuit IC via an external voltage measurement in a simple and accurate manner. 
     In the arrangement shown in FIG. 2, the references D 1  and D 2  denote a first and a second semiconductor diode dimensioned in accordance with the implementations described hereinbefore, which diodes have their cathodes connected together and to an output and an inverting input (−) of a first operational amplifier OPV 1 . Each diode D 1  and D 2  constitutes a temperature-dependent component of a measuring element and is inserted in one of two current paths by way of a connection of their anodes to a respective current source. The current sources are preferably constituted by two commonly controlled output branches of a current mirror arrangement. The diodes D 1  and D 2  are impressed as temperature-dependent components with a current I which is predetermined in the relevant current path by the associated current source. Consequently, a temperature-dependent voltage is generated at the anodes of the diodes D 1  and D 2 . To detect the temperature of the electronic circuit IC (not shown in FIG. 2) with this measuring element, it is in close thermal communication with this electronic circuit IC. The arrangement shown in FIG. 2 is preferably monolithically integrated with the electronic circuit IC on a common semiconductor body. Moreover, other thermal connections are possible, for example, adhesive or soldered joints with which the plurality of semiconductor bodies may be combined to a compact assembly. 
     The current paths formed from the diodes D 1  and D 2  and their series-arranged current sources in the arrangement of FIG. 2 are arranged parallel to each other between a power supply terminal VDD and the junction point of the cathodes of the diodes D 1 , D 2 . The anode of the second diode D 2  is further connected to a non-inverting input (+) of a second operational amplifier OPV 2 . An output and an inverting input (−) of the second operational amplifier OPV 2  are connected to a first terminal of a first ohmic resistor R 1 . In this way, the second operational amplifier OPV 2  constitutes a voltage follower by which the potential VD 2  from the anode of the second diode D 2  is low-ohmic supplied to the first terminal of the first ohmic resistor R 1 . 
     In a corresponding way, the anode of the first diode D 1  is connected to a non-inverting input (+) of a fourth operational amplifier OPV 4 . An output and an inverting input (−) of the fourth operational amplifier OPV 4  are interconnected. In this way, the fourth operational amplifier OPV 4  also constitutes a voltage follower by which the potential VD 1  is low-ohmic supplied by the anode of the first diode D 1 . 
     Also the first operational amplifier OPV 1  is arranged as a voltage follower. Its non-inverting input (+) receives the reference voltage V ref  which is preferably derived from a bandgap reference and is therefore very temperature-stable. This reference voltage V ref  is thus available with a low resistance at the cathode junction of the diodes D 1 , D 2 . It is also applied to the contact of the electronic circuit IC, which contact is indicated in a corresponding manner in FIG.  1 . 
     For further processing, the potentials of the anodes of the diodes D 1 , D 2  and the reference voltage V ref  are available with a low resistance in the arrangement described with reference to FIG.  2 . 
     A second terminal of the first ohmic resistor R 1  is connected to a first terminal of a second ohmic resistor R 2  and an inverting input of a third operational amplifier OPV 3 . A second terminal of the second ohmic resistor R 2  is connected to an output of the third operational amplifier OPV 3 . A non-inverting input (+) of the third operational amplifier OPV 3  is connected to the output of the first operational amplifier OPV 1 . The third operational amplifier OPV 3  operates as an inverting voltage amplifier whose voltage amplification is determined by the resistance ratio of the first and second ohmic resistors R 1 , R 2 . The reference voltage V ref  is used as a reference potential for this voltage amplifier. 
     The output of the fourth operational amplifier OPV 4  is connected to a first terminal of a third ohmic resistor R 3 . The output of the third operational amplifier OPV 3  is connected to a first terminal of a fourth ohmic resistor R 4 . The third and fourth ohmic resistors R 3 , R 4  are connected together by way of their second terminals and to a non-inverting input (+) of a fifth operational amplifier OPV 5 . 
     Via the third and fourth ohmic resistors R 3  and R 4 , the voltages from the outputs of the third and fourth operational amplifiers OPV 3  and OPV 4  are combined at the junction point of the second terminals of the third and fourth ohmic resistors R 3 , R 4 . The third and fourth ohmic resistors R 3 , R 4  thus constitute a voltage combination stage for forming a voltage value which corresponds to the arithmetic mean value weighted by means of the resistances of the third and the fourth ohmic resistors R 3 , R 4  of the temperature-dependent voltage V D1  at the first temperature-dependent component, the first diode D 1 , and the temperature-dependent voltage V D2 , inverted by means of the voltage amplification of the third operational amplifier OPV 3 , at the second temperature-dependent component, the second diode D 2 . 
     The fifth operational amplifier OPV 5  operates as a non-inverting amplifier at the reference voltage V ref . To this end, an output of the fifth operational amplifier OPV 5  is connected to a first terminal of a fifth ohmic resistor R 5 . The fifth ohmic resistor R 5  constitutes a series arrangement with a sixth ohmic resistor R 6 , one end point of which is formed from the first terminal of the fifth ohmic resistor R 5  and the second end point of which is formed from a first terminal of the sixth ohmic resistor R 6 . This second end point is connected to the output of the first operational amplifier OPV 1  and thus receives the reference voltage V ref . Via a connection of their second terminals, the fifth ohmic resistor R 5  and the sixth ohmic resistor R 6  constitute the series arrangement; this connection is also combined with an inverting input (−) of the fifth operational amplifier OPV 5 . The amplification of the fifth operational amplifier OPV 5  results from the resistances of the fifth and sixth ohmic resistors R 5  and R 6 . The output voltage V temp  representing a measure of the temperature T of the electronic circuit IC is provided at the output of the fifth operational amplifier OPV 5 . 
     In combination with the above-mentioned equations [1] to [6], which also apply to the diodes D 1  and D 2  constituting the measuring element, the factor a presented in equation [1] can now be computed for the arrangement shown in FIG.  2 . Furthermore, it can be assumed in a satisfactory approximation that the voltages at the outputs of the voltage followers OPV 2  and OPV 4  correspond to the voltages at their respective (non-inverting (+)) inputs. While considering the circuitry of the third operational amplifier OPV 3 , the equation                  V     D2   ′       =       -         R   2       R   1            [       V   D2     -     V   ref       ]         +     V   ref         ,           [   7   ]                                
     is obtained, wherein 
     R 1  is the resistance of the first ohmic resistor R 1 , 
     R 2  is the resistance of the second ohmic resistor R 2 , and 
     V D2  is the potential at the output of the third operational amplifier OPV 3 . 
     Via the third and fourth ohmic resistors R 3  and R 4 , the voltages V D1  and V D2  are combined at the junction point of these resistors and hence at the non-inverting input (+) of the fifth operational amplifier OPV 5 . The following voltage V X , corresponding to the ratio between the resistances of these resistors R 3  and R 4 , is obtained at the non-inverting input (+) of the fifth operational amplifier OPV 5 :                  V   X     =           R   4         R   3     +     R   4              (       V   D1     -     V     D2   ′         )       +     V     D2   ′           ,           [   8   ]                                
     in which 
     R 3  is the resistance of the third ohmic resistor R 3  and 
     R 4  is the resistance of the fourth ohmic resistor R 4 . 
     The fifth operational amplifier OPV 5  operates as a non-inverting amplifier at the reference voltage V ref . The amplification is obtained from the resistors R 5  and R 6 . The fifth operational amplifier OPV 5  provides, at its output, the output voltage V temp  which is a measure of the temperature T of the electronic circuit IC, which voltage is computed from the following equation:                  V   temp     =         (       V   x     -     V   ref       )              R   5     +     R   6         R   6         +     V   ref         ,           [   9   ]                                
     in which 
     R 5  is the resistance of the fifth ohmic resistor R 5  and 
     R 6  is the resistance of the sixth ohmic resistor R 6 . 
     When equations [7] and [8] are used in equation [9], the following relation is obtained for the output voltage V temp  representing a measure of the temperature T of the electronic circuit IC:                V   temp     =         [           R   4         R   3     +     R   4         ·     V   D1       +       (     1   -       R   4         R   3     +     R   4           )     ·     (         -       R   2       R   1              (       V   D2     -     V   ref       )       +     V   ref       )       -     V   ref       ]     ·         R   5     +     R   6         R   6         +     V   ref               [   10   ]                                
     For an effective dimensioning of the described embodiment of the arrangement according to the invention, the resistances of the first and second ohmic resistors R 1 , R 2  are chosen to be equally large. Since the third operational amplifier OPV 3  is arranged as an inverting voltage amplifier, a voltage amplification of 
     
       
           A   V =−1 
       
     
     is obtained. 
     The resistors R 3  and R 4  determine the voltage V X  at the junction point of the second terminals of the third and fourth ohmic resistors R 3 , R 4  and the non-inverting input (+) of the fifth operational amplifier OPV 5 . The non-inverting input (+) of the fifth operational amplifier OPV 5  should receive the arithmetic mean value of the voltages V D1  and V D2 . The resistances of the third and fourth ohmic resistors R 3  and R 4  should therefore be chosen to be equally large. With 
     
       
           R   1   =R   2  and  R   3   =R   4   
       
     
     equation [10] is simplified as follows:                V   temp     =         1   2     ·           R   5     +     R   6         R   6            [       V   D1     -     V   D2       ]         +       V   ref     .               [   11   ]                                
     When, finally, the differences between the voltages at the anodes of the diodes D 1  and D 2  is replaced by equation [6], the following equation is obtained for the output voltage V temp  representing a measure of the temperature T of the electronic circuit IC:                V   temp     =                 k   ·   ln                   x       2      q                R   5     +     R   6         R   6              a       ·   T     +       V   ref     .               [   12   ]                                
     The factor combined to a in the above-mentioned equation [12] is constant via the temperature T and only dependent on the dimensioning of the circuit. As is also clear from equation [1], the factor a determines the slope of the temperature curve. The resistors R 5 , R 6  are dimensioned in such a way that an adequate amplification is obtained. The output voltage V temp  representing a measure of the temperature T of the electronic circuit IC thus increases linearly with the absolute temperature T. The output voltage V temp  consists of the addition of the temperature-dependent part and the reference voltage V ref  which is derived within the arrangement according to the invention or the electronic circuit IC, for example, from the bandgap voltage of a bandgap reference. When this reference voltage V ref  is available at an external contact of the electronic circuit IC, as is indicated in FIG. 1, the temperature-dependent part (of the potential) of the output voltage V temp  can be directly measured by measuring the potential difference between (the potential of) the output voltage V temp  and (the potential of) the reference voltage V ref . If the slope of V temp  is known, the absolute temperature T of the electronic circuit IC can thus be determined in a simple and accurate manner. 
     The invention thus provides a simple and precise measurement of the temperature of an electronic circuit, both during its manufacture and during its operation-defined use. As far as its accuracy is concerned, the arrangement according to the invention is only dependent on the spread of a small part of the components used and is therefore insensitive to manufacturing spreads and disturbances which relate to, for example, the reference voltage, or to disturbing effects on the power supply voltage or ground connections of the electronic circuit. By targeted use of the internal reference voltage V ref  instead of a ground potential occurring in the electronic circuit or the arrangement according to the invention, inaccuracies caused by local fluctuations are eliminated. 
     The arrangement according to the invention is preferably completely integrated with the electronic circuit whose temperature is to be measured. 
     The inverter stage formed by the third operational amplifier OPV 3  in the shown embodiment of the arrangement has a particular significance. By inverting the voltage V D2  at the anode of the second diode D 2  with respect to the reference voltage V ref , the sum of the two potentials V D1  and V D2  at the anodes of the first and second diodes D 1 , D 2  occurs at the series arrangement of the third and fourth ohmic resistors R 3  and R 4 . It is thereby additionally achieved that the reference voltage V ref  at the output of the fifth operational amplifier OPV 5  is only taken along as an additive value, as is evident from equation [12]. This reference voltage V ref  can be subtracted by measurement of the voltage difference, as is indicated in FIG.  1 . 
     The use of an internal reference voltage also has the effect that the components used in the arrangement according to the invention are operated at optimal working points. As a result, the arrangement according to the invention operates to a very linear extent over a large temperature range. In a dimensioning example, a range between −40° C. and +125° C. can be easily achieved. This is significant for the specification of the electronic circuits to be measured.