Abstract:
Various embodiments that pertain to electronic element matching are described. Having electronic elements, such as transistors, match can be relatively easy in an integrated circuit environment. Transitioning to a discrete circuit environments, finding electronics elements that match one another can be more challenging. If the electronic elements themselves do not match, then their outputs will not match. To compensate for this mismatch when one wants the outputs to match, an output of one of the elements can be modified so that the outputs do match one another. Therefore, a discrete circuit can be produced that functions similarly to that of an integrated circuit.

Description:
GOVERNMENT INTEREST 
       [0001]    The innovation described herein may be manufactured, used, imported, sold, and licensed by or for the Government of the United States of America without the payment of any royalty thereon or therefor. 
     
    
     BACKGROUND 
       [0002]    An electrical circuit designer can want to create a circuit with elements that have matching physical characteristics. The designer can select to use an integrated circuit to produce the circuit with elements that have matching physical characteristics. This matching can occur with relative ease because in the integrated circuit the elements share a substrate. However, if the designer wants to use a discrete circuit as opposed to the integrated circuit, then the substrate is not available for the matching and this can make matching more difficult. 
       SUMMARY 
       [0003]    In one embodiment, a system comprises a determination component and a compensation component. The determination component can be configured to make a determination that an output of a first discrete electronic element that is part of a circuit and an output of a second discrete electronic element that is part of the circuit do not match. The compensation component can be configured to perform a compensation upon the circuit such that the output of the first discrete electronic element and the output of the second discrete electronic element match. The determination component, the compensation component, or a combination thereof is implemented, at least in part, by way of non-software. 
         [0004]    In one embodiment, a method is performed by a circuit management apparatus. The method comprises obtaining a first voltage change from across a first measurement resistor, where the first measurement resistor is associated with a first transistor. The method also comprises calculating a current through the first measurement resistor by use of the first voltage change. The method further comprises obtaining a second voltage change from across a second measurement resistor, where the second measurement resistor is associated with a second transistor. In addition, the method comprises calculating a current through the second measurement resistor by use of the second voltage change. Further, the method comprises determining if a difference that is undesired exists between the current through the first measurement resistor and the current through the second measurement resistor. The method additionally comprises computing a value for a discrete compensation resistor when it is determined that the difference does exist, where the value is based, at least in part, on the difference between the current through the first measurement resistor and the current through the second measurement resistor. The method also comprises setting the discrete compensation resistor to implement with the value such that the current of the first transistor and the current of the second transistor match, where the discrete compensation resistor is associated with the second transistor. 
         [0005]    In one embodiment, a system comprises a differential pair comprising a first discrete transistor and a second discrete transistor, where the current of the first discrete transistor does not match with a current of the second discrete transistor. The system also comprises a first discrete measurement hardware component that is physically coupled to the first discrete transistor and that produces an information set of the current of the first discrete transistor and a second discrete measurement hardware component that is physically coupled to the second discrete transistor and that produces an information set of the current of the second discrete transistor. Additionally, the system comprises a discrete compensation resistor that is physically coupled to the second discrete transistor and that performs a modification to the current of the second discrete transistor to produce a modified current of the second discrete transistor where the current of the first discrete transistor and the modified current of the second transistor match. The modification can be based, at least in part, on the information set of the current of the first discrete transistor and the information set of the current of the second discrete transistor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Incorporated herein are drawings that constitute a part of the specification and illustrate embodiments of the detailed description. The detailed description will now be described further with reference to the accompanying drawings as follows: 
           [0007]      FIG. 1  illustrates one embodiment of a system comprising a first transistor, a second discrete transistor, a first measurement resistor, a second measurement resistor, and a compensation resistor; 
           [0008]      FIG. 2  illustrates one embodiment of a system comprising the first transistor, the second discrete transistor, the first measurement resistor, the second measurement resistor, the compensation resistor, an analog-to-digital converter, and a controller. 
           [0009]      FIG. 3  illustrates one embodiment of a system comprising the first transistor, the second discrete transistor, the first measurement resistor, the second measurement resistor, the compensation resistor, an analog-to-digital converter, a controller, and an input switch. 
           [0010]      FIG. 4  illustrates one embodiment of a system comprising a determination component and a compensation component; 
           [0011]      FIG. 5  illustrates one embodiment of a system comprising the determination component, the compensation component, an identification component, and a causation component; 
           [0012]      FIG. 6  illustrates one embodiment of a system comprising a processor and a non-transitory computer-readable medium; 
           [0013]      FIG. 7  illustrates one embodiment of a method comprising five actions; and 
           [0014]      FIG. 8  illustrates one embodiment of a method comprising four actions. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    When creating a circuit with discrete components, it can be difficult to find discrete elements that actually match (e.g., elements that have the same cross-sectional area and/or have the same doping profile). Even if two transistors have the same part number, the β-value (common-emitter current gain) of the two transistors can vary widely between them. Transistors can be similar, but a difference of one micrometer from one transistor to another can produce results such that the transistors are not matched. Further, even if two discrete transistors do physically match, the transistors may have different temperature in operation and therefore still not fully match. Having the temperature of these transistors match while current is in operation can be important since electrical characteristics can vary with temperature. Since discrete transistors do not share a substrate, the chances of their temperature matching are extremely small. If the temperatures do not match, then the discrete transistors themselves do not match and in turn their outputs do not match. 
         [0016]    With practice of aspects disclosed here a discrete circuit can function similar to an integrated circuit. This similar functioning can include functioning as if there is temperature and physical matching of electronic element characteristics. Since the discrete circuit does not have the substrate of the integrated circuit, the discrete circuit can cause physical matching of elements, such as transistors, through a feedback system. Voltage and/or current can be measured for a first transistor and a second transistor that are part of the discrete circuit, such as part of a differential pair. If the voltages or currents of the transistors do not match, then a resistor associated with one of the transistors can have its value modified. The modification of this value can cause the output of the transistors to match. Therefore, the discrete circuit can emulate an integrated circuit. 
         [0017]    Aspects disclosed herein can be practiced at least in the fields of circuit design, analog electronics, and electronic instrumentation. In one example, aspects disclosed herein can be used in making a prototype of a circuit with discrete elements. Having a manufacturer make a prototype with an integrated circuit can be cost prohibitive. Therefore, it can be advantageous to make a prototype of discrete circuits since it can be cheaper. With this, the prototype can be for a circuit intended to be manufactured as an integrated circuit. 
         [0018]    The following includes definitions of selected terms employed herein. The definitions include various examples. The examples are not intended to be limiting. 
         [0019]    “One embodiment”, “an embodiment”, “one example”, “an example”, and so on, indicate that the embodiment(s) or example(s) can include a particular feature, structure, characteristic, property, or element, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property or element. Furthermore, repeated use of the phrase “in one embodiment” may or may not refer to the same embodiment. 
         [0020]    “Computer-readable medium”, as used herein, refers to a medium that stores signals, instructions and/or data. Examples of a computer-readable medium include, but are not limited to, non-volatile media and volatile media. Non-volatile media may include, for example, optical disks, magnetic disks, and so on. Volatile media may include, for example, semiconductor memories, dynamic memory, and so on. Common forms of a computer-readable medium may include, but are not limited to, a floppy disk, a flexible disk, a hard disk, a magnetic tape, other magnetic medium, other optical medium, a Random Access Memory (RAM), a Read-Only Memory (ROM), a memory chip or card, a memory stick, and other media from which a computer, a processor or other electronic device can read. In one embodiment, the computer-readable medium is a non-transitory computer-readable medium. 
         [0021]    “Component”, as used herein, includes but is not limited to hardware, firmware, software stored on a computer-readable medium or in execution on a machine, and/or combinations of each to perform a function(s) or an action(s), and/or to cause a function or action from another component, method, and/or system. Component may include a software controlled microprocessor, a discrete component, an analog circuit, a digital circuit, a programmed logic device, a memory device containing instructions, and so on. Where multiple components are described, it may be possible to incorporate the multiple components into one physical component or conversely, where a single component is described, it may be possible to distribute that single component between multiple components. The term ‘component’ and the term ‘module’ can be used interchangeably to have the same meaning 
         [0022]    “Software”, as used herein, includes but is not limited to, one or more executable instructions stored on a computer-readable medium that cause a computer, processor, or other electronic device to perform functions, actions and/or behave in a desired manner. The instructions may be embodied in various forms including routines, algorithms, modules, methods, threads, and/or programs including separate applications or code from dynamically linked libraries. 
         [0023]      FIG. 1  illustrates one embodiment of a system  100  comprising a first transistor  110 , a second discrete transistor  120 , a first measurement resistor  130 , a second measurement resistor  140 , and a compensation resistor  150 . The transistors  110 - 120  and the resistors  130 - 150  can be discrete circuit elements. The first transistor  110  and the second transistor  120  can form a differential pair. The first measurement resistor  130  can be physically coupled to the first transistor  110  and can produce an information set of the current of the first transistor  110 . Likewise, the second measurement resistor  140  can be physically coupled to the second transistor  120  and can produce an information set of the current of the second transistor  120 . The information sets indicators of a voltage drop across a respective resistor. With this voltage drop and a value of the resistors  130  and  140  known (e.g., the resistors  130  and  140  are of about equal value), the currents for the first transistor  110  and the second transistor  120  can be calculated through Ohm&#39;s law (I=V/R). 
         [0024]    In one embodiment, as opposed to using the first measurement resistor  130  and/or the second measurement resistor  140 , non-invasive current sensors can be used. These current sensors could measure the current directly as opposed to measuring voltage across a resistor. The resistors  130  and  140  as well as the current sensors can be examples of measurement hardware components. Whether resistors  130  and  140  are used or current sensors, the same approach can be applied. 
         [0025]    If the currents are equal for both transistors  110  and  120 , then the compensation resistor  150  has a value of about zero (compensation is not performed). However, if the current of the first transistor  110  does not match with a current of the second transistor  120 , then the compensation resistor  150  can operate. The compensation resistor  150  can be physically coupled to the second transistor  120  and can perform a modification to the current of the second transistor  120 . This modification can change the current of the second transistor  120  into a modified current of the second transistor that matches the current of the first transistor  110 . The modification can be based, at least in part, on the information set of the current of the first transistor  110  and the information set of the current of the second transistor  120 . 
         [0026]    While the system  100  is illustrated with one compensation resistor  150 , it is to be appreciated by one of ordinary skill in the art that more than one compensation resistor can be used. In one example, in addition to the compensation resistor  150  being physically coupled to the second transistor  120  a second compensation resistor can be physically coupled to the first transistor  110  in an equivalent location to that of the compensation resistor  150 . This way, if the current is higher for the first transistor  110  than the second transistor  120 , then appropriate compensation can occur so currents match. 
         [0027]    While the system  100  addresses transistors  110  and  120 , it is to be appreciated by one of ordinary skill in the art that other electronic elements can be used and thus be matched. In one example, two diodes can be matched through aspects disclosed herein. Further, while the system  100  illustrates matching of two electronic elements, more than two electronic elements can be matched together if desired. In one example, the matched elements can be medal-oxide field-effect transistors (MOSFETs) or bipolar junction transistors (BJTs). 
         [0028]    In one example with the transistors  110  and  120  being BJTs, their emitters can be tied together and the bases of the BJTs can comprise input of the differential pair while collectors of the BJTs can comprise the output of the differential pair. The goal can be for the system  100 , as a circuit, to produce an about zero output voltage when input voltage to the bases is about equal. With this, the differential pair responds to voltage differences while rejecting identical voltage signals. 
         [0029]      FIG. 2  illustrates one embodiment of a system  200  comprising the first transistor  110 , the second discrete transistor  120 , the first measurement resistor  130 , the second measurement resistor  140 , the compensation resistor  150 , an analog-to-digital converter  210 , and a controller  220 . The analog-to-digital converter  210  can measure the information set of the current of the first transistor  110  and measure the information set of the current of the second transistor  120 . The controller  220  can make a determination of the value of the compensation resistor  150  through use of the information set of the current of the first transistor  110  and the information set of the current of the second transistor  120 . While shown as two distinct items, the analog-to-digital converter  210  and the controller  220  can function as a single physical item. The controller  220  can sets the value of the compensation resistor  150  in accordance with the determination. 
         [0030]      FIG. 3  illustrates one embodiment of a system  300  comprising the first transistor  110 , the second discrete transistor  120 , the first measurement resistor  130 , the second measurement resistor  140 , the compensation resistor  150 , an analog-to-digital converter  210 , a controller  220 , and an input switch  310 . The input switch  310  can move among a first position aligned with an end of the first measurement resistor  130 , a second position aligned with an opposite end of the first measurement resistor  130 , a third position aligned with an end of the second measurement resistor  140 , and a fourth position aligned with an opposite end of the second measurement resistor  140 . The analog-to-digital converter  210  can obtains a voltage when the input switch is at the first position, the second position, the third position, and the fourth position. These voltages can be available to the controller  220 . The controller  220  can use a difference between the voltage when the input switch  310  is at the first position and the voltage when the input switch  310  is at the second position in making the determination. With this, the controller  220  can measure the voltage drop across the measurement resistor  130 . Similarly, the controller can use a difference between the voltage when the input switch  310  is at the third position and the voltage when the input switch  310  is at the fourth position in making the determination. 
         [0031]    With these differences, the controller  220  can determine if the outputs for the transistors  110  and  120  match. If values of the resistors  130  and  140  are about the same and the voltage drops are different, then the controller  220  can identify that the currents are different. Based on this difference, the controller  220  can calculate the value of the compensation resistor  150  to have the currents match and cause the compensation resistor  150  to implement with the value. 
         [0032]    In one example, the resistors  130  and  140  can have about the same value, such as about 1 Ohm (Ω). The voltage drop across the resistor  130  can be 1 Volts (V) while the voltage drop across the resistor  140  can be 2V. Therefore, the current can calculated as 1 Amp (A) for the transistor  110  due to current equaling 1 V/1Ω and 2 A for the transistor  120  due to current equaling 2 V/1Ω. The compensation resistor  150  can be set at 1 Ω such that the total resistance for the individual resistors  110  and  120  is 2Ω and this can cause the output currents to match at 1 A. 
         [0033]    After the controller  210  sets the value of the compensation resistor  150 , the analog-to-digital converter  210 , the input switch  310 , and the controller  220  can continue to perform their respective functionality. Multiple changes can occur in the system  300  (or, for example, the system  100  of  FIG. 1 ). In one example, over time, the transistors  110  and  120  to experience changes such that currents start to differ over time. In another example, voltage provided by the voltage sources can change (e.g. by technician instruction). The input switch  310  can continuously cycle among the four positions and the analog-to-digital converter  210  and controller  220  can work to update the compensation resistor  150  so that the currents continue to match when a change occurs. 
         [0034]      FIG. 4  illustrates one embodiment of a system  400  comprising a determination component  410  and a compensation component  420 . The determination component  410  can be configured to make a determination that an output of a first discrete electronic element (e.g., the first transistor  110  of  FIG. 1  or a diode) that is part of a circuit does not match an output of a second discrete electronic element (e.g., the second transistor  120  of  FIG. 1 ) that is part of the circuit. In one example, the output can be a current of the respective electronic element or can be a voltage of the respective electronic element. 
         [0035]    The compensation component  420  can be configured to perform a compensation upon the circuit such that the output of the first discrete electronic element and the output of the second discrete electronic element match. This compensation can be performed in different manners. In one embodiment, the compensation component  420  performs the compensation through adjustment of a bias of at least one of the first discrete electronic element or the second discrete electronic element. In this embodiment, this adjustment can comprise adjusting a direct current voltage or current for the discrete electronic element. The compensation component  420  can comprise logic to determine what electronic element bias to modify, how modification should occur and to what degree, or if adjustment of the bias should be the modification type. 
         [0036]    In one embodiment, the compensation component  420  performs the compensation through adjustment of a value of a variable resistor (e.g., the compensation resistor  150  of  FIG. 1 ) associated with the first discrete electronic element. The compensation component  420  can be configured to select the value of the variable resistor based, at least in part, on the output of the first discrete electronic element and the output of the second discrete electronic element. The variable resistor can modify at least one of the output of the first discrete electronic element or the output of the second discrete electronic element. The compensation component  420  can compare the output of the first discrete electronic element against the output of the second discrete electronic element to create a comparison result. The compensation component  420  can determine if the there is a difference between the output of the first discrete electronic element and the output of the second discrete electronic element. If there is no difference, then the outputs match and the value of the variable resistor can be unchanged. Conversely, if there is a difference, then the outputs do not match and setting or changing the value may be appropriate. When there is a difference the compensation component  420  can select and implement the value. 
         [0037]    While discussion herein relates to a difference between the outputs, an actual implementation may be used that distinguishes between a desired difference and an undesired difference. Using the system  100  of  FIG. 1  as an example circuit in this paragraph, the transistors  110  and  120  should be matched so that the circuit as a whole responds to voltages. A circuit designer should be careful so that the circuit fails to respond to any external voltage. To put another way, the compensation resistor  150  should not be configured to compensate for every difference, just differences from arising from physical differences of the transistors  110  and  120  themselves (an undesired difference) as opposed to a signal-input difference (a desired difference). To achieve this, a circuit designer can design a system in accordance with aspects disclosed herein such that the system can distinguish between a desired difference and an undesired difference. 
         [0038]    Distinguishing between a desired difference and an undesired difference can be performed by the compensation component  420 . The compensation component  420  can determine if the difference is a desired difference or is not desired. The compensation component  420  can select the value, and in turn cause the variable resistor to implement with the value, when the difference is not desired and when the difference is desired the variable resistor can remain unchanged. 
         [0039]    The compensation component  420  can determine if the difference is desirable in various manners depending on circuit design. In one embodiment, the desired difference is that the difference meets a set threshold (e.g., exceed the set threshold or reaches the set threshold). This can be used such that a difference, such as a current difference, is neglected when above a certain amount. The compensation component  420  can determine if the difference is desired or not depending on if the difference is constant or if the difference is time-varying. If the difference is non-constant, such as being time varying, then the difference can be classified as desired, while a constant difference can be considered as undesired and therefore be subject to correction with the variable resistor. The compensation component  420  can be configured to not function, such as by being disabled, when an input signal is applied to the circuit. Once the input signal is no longer applied, the compensation component  420  can continue to operate. 
         [0040]    The determination component  410  and the compensation component  420  can function continuously. Once the compensation component  420  performs the compensation, the determination component  410  can continuously determine if the outputs continue to match or not. This lack of matching can occur to physical changes to the electronic elements over time. If a lack of matching is determined subsequent to the compensation, then the compensation component  420  can perform another compensation to cause the outputs to match. 
         [0041]      FIG. 5  illustrates one embodiment of a system  500  comprising the determination component  410 , the compensation component  420 , an identification component  510 , and a causation component  520 . The identification component  510  can be configured to identify a situation where mismatch of the output of the first discrete electronic element and the output of the second discrete electronic element is appropriate. The causation component  520  can be configured to prevent the compensation component  420  from performance of the compensation when the situation is identified. 
         [0042]      FIG. 6  illustrates one embodiment of a system  600  comprising a processor  610  and a computer-readable medium  620  (e.g., non-transitory computer-readable medium). In one embodiment, the computer-readable medium  620  is communicatively coupled to the processor  610  and stores a command set executable by the processor  610  to facilitate operation of at least one component disclosed herein (e.g., the determination component  410  of  FIG. 4  and/or the compensation component  420  of  FIG. 4 ). In one embodiment, at least one component disclosed herein (e.g., the identification component  510  of  FIG. 5  and/or the causation component  520  of  FIG. 5 ) can be implemented, at least in part, by way of non-software, such as implemented as hardware by way of the system  600 . The processor  610  and/or the computer-readable medium  620  can be used by systems disclosed herein. In one example, when the input switch  310  of  FIG. 3  moves and the analog-to-digital converter  210  of  FIG. 3  obtains a voltage represented as a number, the number can be retained by the computer-readable medium  620 . In one embodiment, the computer-readable medium  620  is configured to store processor-executable instructions that when executed by the processor  610  cause the processor  610  to perform a method disclosed herein (e.g., the method  700  and  800  addressed below). 
         [0043]      FIG. 7  illustrates one embodiment of a method  700  comprising five actions  710 - 750 . At  710 , voltage change information can be obtained. This can include obtaining a first voltage change from across the first measurement resistor  130  of  FIG. 1  that is associated with the first transistor  110  of  FIG. 1  as well as obtaining a second voltage change from across the second measurement resistor  140  of  FIG. 1  that is associated with the second transistor  120  of  FIG. 1 . Obtaining the first voltage change and second voltage change can comprise obtaining change information that numerically describes the first and second voltage change. 
         [0044]    At  720  calculating a current through the first measurement resistor  130  of  FIG. 1  can occur by use of the first voltage change. Also at  720  calculating a current through the second measurement resistor  140  of  FIG. 1  can occur by use of the second voltage change. While the obtaining and calculating of  710  and  720  respectively are illustrated as occurring in one action, these can occur in separate actions and may or may not occur concurrently. 
         [0045]    At  730  determining if a difference that is undesired exists between the current through the first measurement resistor and the current through the second measurement resistor takes place. If the difference is desired, then the method  700  can function as if there is no difference and the method can return to  710  to obtain changes. If the difference is undesired, then the method  700  can function as if there is a difference and continue. 
         [0046]    At  740 , a value for compensation resistor  150  of  FIG. 1  can be computed. This computation can occur when it is determined at  730  that the difference does exist. The value can be based, at least in part, on the difference between the current through the first measurement resistor  130  of  FIG. 1  and the current through the second measurement resistor  140  of  FIG. 1 . 
         [0047]    At  750 , the compensation resistor  150  of  FIG. 1  can be set to implement with the value. This implementation can be such that the current of the first transistor  110  of  FIG. 1  and the current of the second transistor  120  of  FIG. 1  match. In one embodiment, the method  700  can return to obtaining change information at  710  once the value is set. This can be to verify that the value is accurately compensating such that the transistors match. If accurate compensation is not occurring, then the method  700  can function again to change the value. 
         [0048]    The compensation can be initially accurate, but as time goes on the transistors can physically change such that the uncompensated difference changes and therefore the value no longer performs adequate compensation. This can be identified through actions  710  and  720 . At  730  determining if the current through the first measurement resistor  130  of  FIG. 1  does not match the current through the second measurement resistor  140  of  FIG. 1  after the discrete compensation resistor is set at  750  occurs. If the current through the first measurement resistor  130  of  FIG. 1  does not match the current through the second measurement resistor  140  of  FIG. 1 , then computing a second value (e.g., that is different from the value previously set) for the compensation resistor  150  of  FIG. 1  can occur. The compensation resistor  150  of  FIG. 1  can be set to implement with the second value such that the current of the first transistor  110  of  FIG. 1  and the current of the second transistor  120  of  FIG. 1  match. 
         [0049]    The method  700  can be performed by a circuit management apparatus. One example of the circuit management apparatus comprises the analog-to-digital converter  210  of  FIG. 2  and the controller  220  of  FIG. 2 . In this example, the analog-to-digital converter  210  of  FIG. 2  obtains the change information through measurement and transfers the information to the controller  220  of  FIG. 2  and the controller  220  of  FIG. 2  performs the other actions. In one example, circuit management apparatus comprises the controller  220  of  FIG. 2 . The controller  220  of  FIG. 2  can obtain the change information through collection of the change information from a measurement source (e.g., the analog-to-digital converter  210  of  FIG. 2 ). 
         [0050]      FIG. 8  illustrates one embodiment of a method  800  comprising four actions  810 - 840 . The method  800  can occur with a first and second electronic element that should match and a first and second compensation resistor that are associated with their respectively named element. At  810  an identification can be made that compensation should occur and at  820  a determination can be made on if compensation should take place on the first transistor  110  of  FIG. 1  or the second transistor of  FIG. 1 . In one example, this determination can take place by identifying a higher current between the first and second electronic element. The element with the higher current can have its current adjusted through increased resistance at  830  or  840 . Compensation can occur by modifying the value of both compensation resistors (e.g., move one value up and another down). 
         [0051]    While the methods disclosed herein are shown and described as a series of blocks, it is to be appreciated by one of ordinary skill in the art that the methods are not restricted by the order of the blocks, as some blocks can take place in different orders. Similarly, a block can operate concurrently with at least one other block. Moreover, designations of ‘first’ and ‘second’ are intended merely for identification purposes and not intended to provide any indication of timed order of function, physical location, superiority, importance, etc.