Abstract:
A switched-capacitor circuit includes a plurality of sequentially-operated switched-capacitors A first capacitor is arranged to be coupled and thereafter uncoupled to an input signal during a first time period. Thereby the first capacitor is charged to an input value in dependence on the input signal. A second capacitor is arranged to be coupled and thereafter uncoupled to the first capacitor during a second time period for charge distribution between the second and first capacitor. Pairwise charge distribution is possibly done with further sequentially-operated switched capacitors. A final capacitor is arranged to be coupled and thereafter uncoupled to a previous capacitor during the final time period for charge distribution between the final and the previous capacitor. The switched-capacitor circuit further includes selectively coupling the first and the second sequentially-operated switched-capacitors to an output circuit thereby enabling a desired weighting of the input signal to be attained.

Description:
TECHNICAL FIELD 
     The invention concerns switched capacitor technology, specifically variable value switched capacitor circuits and switched capacitor filters, such as finite impulse response filters (FIR-filter), with variable value switched capacitor circuits. 
     BACKGROUND 
     Switched capacitor circuits are used for their suitability to be placed on a single semiconductor chip thereby replacing filters that have been conventionally constructed using discrete resistors, capacitors and inductors. In switched capacitor circuits, resistors and inductors are replaced by switches and capacitors. 
     Finite impulse response filters (FIR-filters) can be expressed as a series, for example such as            y                   (   k   )       =       ∑     n   =   0     k                     g                   (   n   )     *   x                   (   n   )           ,                          
     where g(n) is the n:th weight factor/coefficient for the n:th input value x(n). Expanded it will end up to be y(k)=g(0)*x(0)+g(1)*x(1)+g(2)*x(2)+. . . +g(k−1)*x(k−1)+g(k)*x(k). The series needs k+1, possibly different, weights/coefficients if it has k terms and an initial value. An implementation of such an equation would not be practical. If a simple and flexible solution to this is desired then an implementation of the recursive equation y(k)=y(k−1)+g(k)*x(k) is preferably made. However, an implementation according to the recursive equation requires dynamically adjustable coefficients. In an implementation utilizing switched capacitor technology the value of the coefficient can be varied by, for example, dividing the sampling capacitor into a suitable number of equal sized part-capacitors, for example 256 part-capacitors. The number of part-capacitors used will depend on the desired resolution of the coefficient, a 12 bit resolution coefficient, for example, needs 4096 capacitors. During each sampling all of the sampling capacitors are charged to the input signal value. Thereafter, the input is disconnected and a number of the capacitors representing the desired filter coefficient, are connected to an output circuit, in this case an integrator. An example of such a circuit is described in the U.S. Pat. No. 5,220,286. This method of obtaining a variable coefficient circuit can suitably be named the capacitance division method. A disadvantage can be considered to be the large number of capacitances and corresponding switches that are necessary if a high resolution is desired. 
     SUMMARY 
     An object of the invention is to define a variable value switched capacitor circuit requiring a drastically reduced number of capacitors and switches in relation to a circuit according to the capacitance division method. 
     Another object of the invention is to define a method of controlling a switched capacitor circuit to thereby obtain a variable value switched capacitor with a drastically reduced number of capacitors and switches in relation to a circuit according to the capacitance division method. 
     The aforementioned objects are achieved according to the invention by a switched-capacitor circuit comprising a plurality of sequentially-operated switched-capacitors. A first capacitor is arranged to be coupled and thereafter uncoupled to an input signal during a first time period. Thereby the first capacitor is charged to an input value in dependence on the input signal. A second capacitor is arranged to be coupled and thereafter uncoupled to the first capacitor during a second time period for charge distribution between the second and the first capacitor. Pairwise charge distribution is possibly done with further sequentially-operated switched capacitors. A final capacitor is arranged to be coupled and thereafter uncoupled to a previous capacitor during the final time period for charge distribution between the final and the previous capacitor. The switched-capacitor circuit further comprises means for selectively coupling the first and the second sequentially-operated switched-capacitors to an output circuit thereby enabling a desired weighting of the input signal to be attained. 
     The aforementioned objects are also achieved according to the invention by a switched-capacitor circuit comprising a plurality of sequentially-operated switched-capacitors. The capacitors are sequentially switched during a plurality of time periods. The circuit comprises at least a first, a second and a final sequentially-operated switched-capacitor. The first switched-capacitor is arranged to be coupled and thereafter uncoupled to an input signal during a first time period. The first switched-capacitor is thus charged to an input value in dependence on the input signal. The second switched-capacitor is arranged to be coupled and thereafter uncoupled to the first switched-capacitor during a second time period for charge distribution between the second and the first switched-capacitor. The charge is thus divided between the first and the second switched-capacitor. The second switched-capacitor becoming a previous switched-capacitor during the time period following the time period the second switched-capacitor received charge. The final switched-capacitor is arranged to be coupled and thereafter uncoupled to the previous switched-capacitor, in the minimum case this is the second switched-capacitor, during the final time period for charge distribution between the final and the previous switched-capacitor. The charge is thus divided between the final and the previous switched-capacitor. The switched-capacitor circuit further comprises means for selectively coupling the first and the second switched-capacitors to an output circuit thereby enabling a desired weighting of the input signal to be attained. 
     Advantageously, to achieve a higher weight factor resolution, the circuit further comprises a predetermined number of additional sequentially-operated switched-capacitors. The additional capacitors are arranged between the second switched-capacitor and the final switched-capacitor. Each additional sequentially-operated switched-capacitor is arranged to be coupled and thereafter uncoupled to a previous switched-capacitor during a time period for charge distribution between an additional switched-capacitor in question and the previous switched-capacitor. The charge is thus divided between the additional switched-capacitor in question and the previous switched-capacitor. The additional switched-capacitor in question becoming the previous switched-capacitor during the time period following the time period the additonal switched-capacitor in question received charge. The switched-capacitor circuit further comprises means for selectively coupling each additional sequentially-operated switched-capacitor to an output circuit. 
     Some embodiments of the switched capacitor circuit further comprises a first parallel-operated capacitor. The first parallel-operated capacitor is arranged to be coupled and thereafter be uncoupled to the input signal during the first time period. The first parallel-operated capacitor is not involved in any charge sharing with the sequentially-operated switched-capacitors. The circuit further comprises means for selectively coupling the first parallel-operated capacitor to an output circuit. 
     Advantageously each means for selectively coupling a sequentially-operated capacitor to an output circuit is for each capacitor in question selectively activated during a time period which is after a time period when the capacitor in question distributed its charge to a further capacitor. 
     Preferably each capacitor which is not coupled directly to the input signal is shorted at the latest during a time period before a time period in which a capacitor in question receives a charge distribution from a previous capacitor. 
     In certain embodiments the circuit is doubled into two identical branches, the operation of the branches being time shifted in relation to each other, thereby doubling the throughput rate. In some version the circuit is quadrupled into four identical branches, the operation of the branches being time shifted in relation to each other, thereby quadrupling the throughput rate. In some versions the circuit is arranged to be coupled to one output for every four sequentially-operated switched-capacitors that can be selectively coupled to an output circuit. 
     Preferably all the capacitors all have the same capacitance thereby enabling a selectable linear binary weighting of the input signal. 
     Advantageously the circuit comprises further more parallel-operated input capacitors. The circuit also further advantageously comprises more parallel-operated least significant bit switched-capacitors. In some embodiments the final switched-capacitor consists of a plurality of parallel-operated least significant bit switched-capacitors. 
     To enable weighted summations some embodiments of the circuit further comprises output means in the form of an integrator, thereby providing a computing-element for weighted summations. The circuit is in some embodiments a filter which filters the input signal. The circuit can then for example be a finite impulse response filter working according to a series development. The circuit can also comprise two output circuits, one output giving a quadrature value and the other output giving an in-phase value. 
     Preferably the circuit is completely differential to thereby handle both positive and negative weight factors. Other important advantages with these embodiments of the invention is that the circuit will be immune to supply noise and achieve a high common mode rejection ratio. In some embodiments the circuit comprises a reversing switch to reverse a polarity of the input signal to thereby enable both positive and negative weight factors. 
     The different additional enhancements of the invention can be combined in any desired manner as long as not any conflicting features are combined. The aforementioned objects are also achieved according to the invention by a switched-capacitor circuit which comprises a plurality of sequentially-operated switched-capacitors. The first of which is coupled to an input signal during a first time period thereby charging the first switched-capacitor to an input value in dependence on the input signal. Thereafter the charge on the first switched capacitor is sequentially charge distributed during further time periods. Each sequential charge distribution is between pairs of sequentially-operated switched-capacitors. First the charge is divided between a first pair of sequentially-operated switched capacitors consisting of the first sequentially-operated switched-capacitor and a second sequentially-operated switched-capacitor. Then during a next time period the charge is divided between a second pair of sequentially-operated switched-capacitors consisting of the second sequentially-operated switched-capacitor and a third sequentially-operated switched-capacitor. This is repeated between pairs of sequentially-operated switched-capacitors until a last sequentially-operated switched-capacitor belongs to a pair of switched-capacitors performing charge division. The switched-capacitor circuit further comprises means for selectively coupling the switched-capacitors to an output circuit thereby enabling a desired weighting of the input signal to be attained. 
     The aforementioned objects are also achieved according to the invention by a switched-capacitor circuit comprising a plurality of sequentially-operated switched-capacitors. An input sequentially-operated switched-capacitor is arranged to be coupled and thereafter uncoupled to an input signal during a first time period. The input switched-capacitor is thus charged to an input value in dependence on the input signal. For a following time period the input switched-capacitor becomes a previously charged switched-capacitor. A predetermined number of further sequentially-operated switched-capacitors are arranged to sequentially perform a number of steps. Of which further sequentially-operated switched-capacitors, a discharged current switched-capacitor is arranged to be coupled and thereafter uncoupled to the previously charged switched-capacitor during a time period for charge distribution between the current and the previously charged switched-capacitor. The charge is thus divided between them. Thereafter the current switched-capacitor becomes the previously charged switched-capacitor and the process-steps are repeated until all further sequentially-operated switched-capacitors have become the previously charged switched-capacitor. A final switched-capacitor is arranged to be coupled and thereafter uncoupled to the previously charged switched-capacitor during the final time period for charge distribution between the final and the previously charged switched-capacitor. The charge is thus divided between the final and the previously charged switched-capacitor. Then by further coupling by coupling means selected switched-capacitors to an output circuit a desired weighting of the input signal can be attained. 
     The aforementioned objects are also achieved according to the invention by a method of weighting an input signal by means of a switched-capacitor circuit comprising a plurality of switched-capacitors. According to the method the switched capacitors are sequentially switched during a plurality of time periods. The method comprises a number of steps. In a first step a first switched-capacitor is charged to an input value in dependence on the input signal by coupling and thereafter uncoupling the first switched-capacitor to an input signal during a first time period. Thereafter in a second step the charge on the first switched-capacitor is divided between the first switched-capacitor and a second switched-capacitor by coupling and thereafter uncoupling the second switched-capacitor to the first switched-capacitor during a second time period for enabling charge distribution between the second and the first switched-capacitor, the second switched-capacitor becoming a previous switched-capacitor during the third time period. Thereafter in a final charge division step the charge on the previous switched capacitor is divided between the previous switched-capacitor and a final switched-capacitor by coupling and thereafter uncoupling the final switched capacitor to the previous switched-capacitor during a final time period for enabling charge distribution between the final and the previous switched-capacitor. The first switched-capacitor and the second switched-capacitor are also selectively coupled to an output circuit to thereby enable a desired weighting of the input signal to be attained. 
     Advantageously to further extend the resolution of the weigthing factor the method further comprises a predetermined number of addional steps. The additional steps are preferably performed between the second time period and the final time period and performed on one or more additional switched-capacitors. The additional steps comprises a step that is performed repeatedly on one additonal switched capacitor at a time. The step comprises dividing the charge on the previous switched-capacitor between the previous switched-capacitor and an additional switched-capacitor in question by coupling and thereafter uncoupling the additional switched-capacitor in question to the previous capacitor during a time period for charge distribution between the additional switched-capacitor in question and the previous switched-capacitor. The additional switched-capacitor in question thereafter becomes the previous switched-capacitor for a time period directly following the time period for charge distribution between the additional switched-capacitor in question and the previous switched-capacitor. The method also comprises the additional step or steps of selectively coupling each additional switched-capacitor to the output circuit. 
     In some versions of the method each step of selectively coupling a switched-capacitor to an output circuit is for each switched-capacitor in question selectively activated during a time period which is after a time period when the switched-capacitor in question distributed its charge to a further capacitor. 
     In other versions the method further comprises the step of coupling and thereafter uncoupling a first parallel-operated switched-capacitor to the input signal during the first time period, and selectively coupling the first parallel-operated capacitor to an output circuit. 
     In still other versions for each switched-capacitor which is not coupled directly to the input signal the method comprises the step of shorting a switched-capacitor in question at the latest during a time period before a time period in which the switched-capacitor in question receives a charge distribution from a previous capacitor. 
     The different additional enhancements of the method according to the invention can be combined in any desired manner as long as not any conflicting enhancements are combined. 
     By providing a variable value switched-capacitor circuit a plurality of advantages over prior art systems are obtained. A primary purpose of the invention is to reduce the number of capacitors and switches needed for a specific resolution. For a 12 bit binary coefficient/weight factor, in a basic embodiment of the invention with charge sharing, 13 equal sized capacitors and approximately 40 switches are needed. These numbers should be compared with the 4096 equal sized capacitors and more than 8000 switches that are needed with the capacitance division method. According to the invention this reduction is achieved primarily by sequential charge sharing between pairs of capacitors. The use of a low number of a equal sized capacitors enables a higher accuracy to be achieved as it is easier to manufacture a limited number of equal sized capacitors than manufacturing a large number of equal sized capacitors or a scale of different sized capacitors. Speed improvements are easily attained by adding parallel processing paths. 
     Other advantages of this invention will become apparent from the detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in more detail for explanatory, and in no sense limiting, purposes, with reference to the following figures, in which 
     FIG. 1 shows a switched capacitor circuit according to the invention and an example of its use with an output circuit, 
     FIG. 2 shows a most significant bit or bits expansion, 
     FIG. 3 shows a least significant bit or bits expansion. 
    
    
     DETAILED DESCRIPTION 
     In order to clarify the method and device according to the invention, some examples of its use will now be described in connection with FIGS. 1 to  3 . 
     The basic principle of the invention is to sequentially divide an initial charge between pairs of capacitors. By this division of charge an arbitrary desired coefficient/weight factor can be realised by connecting one or more of the charged capacitors to an output circuit (unless the coefficient is zero, then no capacitor is connected to the output circuit). The method according to the invention will be called the charge sharing method. FIG. 1 shows a switched capacitor circuit  100  according to the invention and an example of its use with an output circuit  199 . In the embodiment according to this example of the invention there are six charge sharing capacitors C 1 , C 2 , C 3 , C 4 , C 5 , C 6 , all of which have an associated signal switch s 1 , s 2 , s 3 , s 4 , s 5 , s 6  for connection of the corresponding capacitor to a charge source, for example a previously charged capacitor, to thereby enable charge sharing. The switches of the switched capacitor circuit can, for example, be MOS transistors. At least all but the first capacitor C 1  have an associated reset/nullification/discharge switch n 2 , n 3 , n 4 , n 5 , n 6  which short circuits, i.e. discharges/nullifies/resets, the corresponding capacitor C 2 , C 3 , C 4 , C 5 , C 6  at the latest during the time period before a capacitor in question is charged during a charge sharing. Normally the first capacitor C 1  does not need to be discharged before it is connected to an input voltage V IN , unless, for example, there is no active source driver feeding the switched capacitor circuit. All but the last capacitor C 6  have an associated part-coefficient switch k 1 , k 2 , k 3 , k 4 , k 5  for connection of the corresponding capacitor C 1 , C 2 , C 3 , C 4 , C 5  to an output V OUT , which is suitably connected to an output circuit, for example like the output circuit  199  in the figure. The output circuit  199  in the figure is an integrator comprising an op-amp OP, an integration capacitor C i ; with an associated nullification/discharge switch n i  for discharging the integration capacitor C i . An integrator  199  is suitable to use as an output circuit when the switched capacitor circuit  100  is used for, for example, realizing a series development. 
     An input voltage V IN  is connected to the first capacitor C 1  through the first signal switch s 1  for charging the first capacitor C 1  to V IN  during a first time period. Also during the first time period the second capacitor C 2  is, at the latest, discharged by means of the associated discharge switch n 2 . The signal switch s 1  and discharge switch n 2  are thus switched from open to closed at the beginning of the first time period, kept closed during the first time period and then opened again at the end of the first time period. During a second time period the charge is shared between the first capacitor C 1  and the second capacitor C 2  by means of signal switch s 2 . The charge is distributed between the two capacitors C 1 , C 2  in dependence of their relative capacitance. The relative capacitances of the capacitors C 1 , C 2 , C 3 , C 4 , C 5 , C 6  will determine what part-coefficient/weight factor each part-coefficient switch k 1 , k 2 , k 3 , k 4 , k 5  will represent. In a preferred embodiment of the invention, the charge sharing capacitors C 1 , C 2 , C 3 , C 4 , C 5 , C 6  of the switched capacitor circuit according to the invention, all have the same capacitance. Each charge sharing will then half the charge and thus also half the voltage which the source capacitor had before the sharing. This will result in linear binary coefficients where the first part-coefficient switch k 1  will represent a value of 0.5, the second part-coefficient switch k 2  will represent a value of 0.25, the third part-coefficient k 3  will represent a value of 0.125, and so on as seen in the basic control table below. 
     Additionally during the second time period, the third capacitor C 3  is discharged by means of its associated discharge switch n 3 . The signal switch s 2  and discharge switch n 3  are thus switched from open to closed at the beginning of the second time period, kept closed during the second time period and then opened again at the end of the second time period. Thus, between the second time period and the third time period the first capacitor C 1  has shared its charge with the second capacitor C 2  and the third capacitor C 3  has been discharged to enable a charge sharing with the second capacitor C 2  during a third time period. During the third time period the second capacitor C 2  shares its charge with the third capacitor C 3 , and the fourth capacitor C 4  is discharged by means of its associated discharge switch n 4 . The signal switch s 3  and discharge switch n 4  are thus switched from open to closed at the beginning of the third time period, kept closed during the third time period and then opened again at the end of the third time period. Additionally, when, for example, an output circuit comprises an accumulator/adder, such as the output circuit  199  shown in the figure, the part-coefficients can be added sequentially to an output circuit. Thus in this example, during the third time period, the part-coefficient switch k 1  associated with the first capacitor C 1  can, in dependence of the desired total weight factor/coefficient, be used for a charge/voltage transfer of the charge/voltage on C 1  to the output V OUT  and output circuit  199  by switching part-coefficient switch k 1  from open to closed at the beginning of the third time period, kept closed during the third time period and then opened again at the end of the third time period. 
     The procedure is repeated during the following time periods for the remainder of capacitors C 4 , C 5 , C 6 , the only divergence to the procedure being that the last capacitor C 6  does not have a part-coefficient switch in this embodiment and can thus not transfer its charge/voltage to the output V OUT . If all of the capacitors C 1 , C 2 , C 3 , C 4 , C 5 , C 6  have the same capacitance, then the last capacitor C 6  and the second to last capacitor C 5  will have the same charge/voltage, a part-coefficient switch for C 6  is thus unnecessary. 
     If the switched capacitor circuit  100  is used in the computation of, for example, a series expansion where several weigthed samples are accumulated/integrated, then a certain degree of overlap can exist between consecutive samples, i.e. in dependence on the length of the switched capacitor circuit two or more different samples are being processed by the switched capacitor circuit at the same time, the samples are pipelined. As high a degree of overlap as possible should always be aspired to be attained. This is made possible by the early transfer of charge, if it should be done, from a capacitor that is not used for any more charge sharing, to an output circuit via the capacitor&#39;s corresponding part-coefficient switch to thereby free the capacitor in question for the next sample. 
     A complete basic control table of the switches is shown below where all of the empty boxes for the switches denote that the switch in question is open, i.e. non-conducting, a “c” denotes closed, i.e. conducting, and c/o denotes that the switch is either closed or open. For the capacitors only the capacitor voltages which have any influence are shown, where V 1  is the first sample and V 2  is the second sample. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Basic Control Table 
               
             
          
           
               
                   
                 Time Period 
               
             
          
           
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
               
               
                   
                   
               
             
          
           
               
                 Reset switch 
               
             
          
           
               
                 n2 
                 c 
                   
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
               
               
                 n3 
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n4 
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n5 
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n6 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
             
          
           
               
                 Signal switch 
               
             
          
           
               
                 s1 
                 c 
                   
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
               
               
                 s2 
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s3 
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s4 
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s5 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s6 
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
             
          
           
               
                 Part-Coefficient switch 
               
             
          
           
               
                 k1 
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
                   
                   
                   
                   
               
               
                 k2 
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k3 
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k4 
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k5 
                   
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
             
          
           
               
                 Capacitor voltage 
               
             
          
           
               
                 C1 
                 V 1   
                 V 1 /2 
                 V 1 /2 
                   
                 V 2   
                 V 2 /2 
                 V 2 /2 
                   
                   
                   
                   
               
               
                 C2 
                 0 
                 V 1 /2 
                 V 1 /4 
                 V 1 /4 
                 0 
                 V 2 /2 
                 V 2 /4 
                 V 2 /4 
               
               
                 C3 
                   
                 0 
                 V 1 /4 
                 V 1 /8 
                 V 1 /8 
                 0 
                 V 2 /4 
                 V 2 /8 
                 V 2 /8 
               
               
                 C4 
                   
                   
                 0 
                 V 1 /8 
                 V 1 /16 
                 V 1 /16 
                 0 
                 V 2 /8 
                 V 2 /16 
                 V 2 /16 
               
               
                 C5 
                   
                   
                   
                 0 
                 V 1 /16 
                 V 1 /32 
                 V 1 /32 
                 0 
                 V 2 /16 
                 V 2 /32 
                 V 2 /32 
               
               
                 C6 
                   
                   
                   
                   
                 0 
                 V 1 /32 
                   
                   
                 0 
                 V 2 /32 
               
               
                   
               
             
          
         
       
     
     After the last sample, in for example a series expansion calculation, the pipeline must be emptied, the final weighted sample added in the output circuit  199  and fed to another circuit. The output circuit must be cleared/made ready for the next calculation of, for example a series expansion, by, for example, discharging the integration capacitor Ci by discharge switch ni, before a new sample, i.e. the first sample of the next calculation, is in any part fed to the output V OUT . According to an enhancement of the invention this can be avoided by providing multiple output circuits, one for every start of a multiple of four part-coefficients, the example above should therefore have two output circuits in such an embodiment. In some applications/embodiments of the invention there is no accumulation in an output circuit and then there can be no overlap, all the part-coefficient switches have to switch during the same time period for transfer of charges/voltages to an output circuit. A no accumulation/overlap control table to the switched capacitor circuit  100  is shown below where all of the empty boxes for the switches denote that the switch in question is open, i.e. non-conducting, a “c” denotes closed, i.e. conducting, and c/o denotes that the switch is either closed or open. For the capacitors only the capacitor voltages which have any influence are shown, where V 1  is the first sample and V 2  is the second sample. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 No accumulator/overlap Control Table 
               
             
          
           
               
                   
                 Time Period 
               
             
          
           
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
               
               
                   
                   
               
             
          
           
               
                 Reset switch 
               
             
          
           
               
                 n2 
                 c 
                   
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
               
               
                 n3 
                   
                 c 
                   
                   
                   
                   
                   
                   
                 c 
               
               
                 n4 
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
                 c 
               
               
                 n5 
                   
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
                 c 
               
               
                 n6 
                   
                   
                   
                   
                 c 
               
             
          
           
               
                 Signal switch 
               
             
          
           
               
                 s1 
                 c 
                   
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
               
               
                 s2 
                   
                 c 
                   
                   
                   
                   
                   
                   
                 c 
               
               
                 s3 
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
                 c 
               
               
                 s4 
                   
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
                 c 
               
               
                 s5 
                   
                   
                   
                   
                 c 
               
               
                 s6 
                   
                   
                   
                   
                   
                 c 
               
             
          
           
               
                 Part-Coefficient switch 
               
             
          
           
               
                 k1 
                   
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                   
               
               
                 k2 
                   
                   
                   
                   
                   
                   
                 c/o 
               
               
                 k3 
                   
                   
                   
                   
                   
                   
                 c/o 
               
               
                 k4 
                   
                   
                   
                   
                   
                   
                 c/o 
               
               
                 k5 
                   
                   
                   
                   
                   
                   
                 c/o 
               
             
          
           
               
                 Capacitor voltage 
               
             
          
           
               
                 C1 
                 V 1   
                 V 1 /2 
                 V 1 /2 
                 V 1 /2 
                 V 1 /2 
                 V 1 /2 
                 V 1 /2 
                 V 2   
                 V 2 /2 
                 V 2 /2 
                 V 2 /2 
               
               
                 C2 
                 0 
                 V 1 /2 
                 V 1 /4 
                 V 1 /4 
                 V 1 /4 
                 V 1 /4 
                 V 1 /4 
                 0 
                 V 2 /2 
                 V 2 /4 
                 V 2 /4 
               
               
                 C3 
                   
                 0 
                 V 1 /4 
                 V 1 /8 
                 V 1 /8 
                 V 1 /8 
                 V 1 /8 
                   
                 0 
                 V 2 /4 
                 V 2 /8 
               
               
                 C4 
                   
                   
                 0 
                 V 1 /8 
                 V 1 /16 
                 V 1 /16 
                 V 1 /16 
                   
                   
                 0 
                 V 2 /8 
               
               
                 C5 
                   
                   
                   
                 0 
                 V 1 /16 
                 V 1 /32 
                 V 1 /32 
                   
                   
                   
                 0 
               
               
                 C6 
                   
                   
                   
                   
                 0 
                 V 1 /32 
               
               
                   
               
             
          
         
       
     
     With a switched capacitor circuit  100  according to FIG. 1 a sampled signal value can be divided into a number of values that form a linear binary series if the capacitors are of equal capacitance. This first basic example of the invention has a 5 bit coefficient/weight factor resolution which can be increased or decreased. After four time periods a new sample of the input signal can be taken if overlap is possible. If a higher sampling rate is desired without increasing the clock rate then several switched capacitor circuits can be coupled to work in parallel. By using four parallel time multiplexed branches the sampling rate corresponds to the switching rate of the switched capacitor circuit  100 . Sever al output circuits can also be used to enable a more efficient pipelining/overlap and/or to directly generate a quadrature and an inphase output. 
     An enhancement of the invention is to add an optional capacitor that is coupled to the input signal during the same time periods that the first capacitor C 1  is coupled to the input signal. Both C 1  and the optional capacitor will then have the whole signal value stored. The first charge sharing is then performed, as previously described, between the first capacitor C 1  and the second capacitor C 2  during the second time period. The optional capacitor is not used for charge sharing and an optional part-coefficient switch associated with the optional capacitor can then during the second time period, in dependence on the desired weight factor, transfer its charge/voltage to the output V OUT . The optional capacitor does not normally need a discharge switch. The most significant bit part-coefficient, from the optional capacitor, will become 1 and thereby increase the signal to noise ratio as more charge is conserved. 
     FIG. 2 shows a most significant bit or bits expansion (MSB-expansion)  200 . The MSB-expansion is meant to replace the most significant bit capacitor and associated switches of a variable switched capacitor circuit. To facilitate the understanding of the MSB-expansion  200  the replacement is done in relation to FIG.  1 . The MSB-expansion  200  is not restricted to be used with a switched capacitor circuit according to FIG.  1 . The MSB-expansion replaces the most significant bit (MSB) capacitor and associated switches, in this case capacitor C 1  and switches s 1  and k 1  of FIG.  1 . The connection points  210 ,  220 ,  230 ,  240  of the MSB-expansion  200  of FIG. 2 are connected to the respective connection points  110 ,  120 ,  130 ,  140  of FIG.  1 . 
     The MSB-expansion  200  of FIG. 2 demonstrates an expansion of three most significant bits. The MSB-expansion  200  comprises four capacitors C 10  (comprising four part-capacitors C 10   a , C 10   b , C 10   c , C 10   d  in the figure), C 11  (comprising two part-capacitors C 11   a , C 11   b  in the figure), C 12 , and C 13 . Each capacitor C 10 , C 11 , C 12 , C 13  has its own corresponding signal switch s 10 , s 11 , s 12 , s 13  and its own corresponding part-coefficient switch k 10 , k 11 , k 12 , k 13 . As previously discussed, according to preferred emodiments of the invention, all, or most, of the capacitors should have the same value. In normalized values and with binary linear coefficients, C 10  should be 4 units, i.e. 4 units of a factor of a Farad, C 11  should be 2 units and C 12  and C 13  should be 1 unit each. This means that C 10  can be made with four 1 unit capacitors C 10   a , C 10   b , C 10   c , C 10   d , and C 11  can be made with two 1 unit capacitors C 11   a , C 11   b , as is shown in FIG.  2 . As is explained above, the capacitance relationship between the capacitors can be different if another coefficient type is desired, such as logarithmic. Depending on the situation, another standard size capacitor can of course be used, for example 0.5 unit capacitors, this would result in C 10  being made of eight 0.5 unit capacitors, C 11  being made of four 0.5 unit capacitors, and C 12  and C 13  each being made of two 0.5 unit capacitors. The number of capacitors that make up each capacitor of FIG. 1 would also change accordingly. 
     The MSB-expansion  200  of FIG. 2 gives, assuming linear binary part-coefficients, a part-coefficient value of 4 for part-coefficient switch k 10  for capacitor C 10 , a part-coefficient value of 2 for part-coefficient switch k 11  for capacitor C 11 , a part-coefficient value of 1 for part-coefficient switch k 12  for capacitor C 12 , and a part-coefficient value of {fraction (1/2+L )} for part-coefficient switch k 13  for capacitor C 13  corresponding to part-coefficient switch k 1  of FIG.  1 . This enhanced verison of the invention results in an even larger dynamic range and thus also higher signal to noise ratio. 
     During a first time period of this enhanced switched capacitor circuit, the four capacitors C 10 , C 11 , C 12 , C 13  are connected to the input signal V IN  via their corresponding signal switches s 10 , s 11 , s 12 , s 13  to thereby fully charge these parallel coupled capacitors C 10 , C 11 , C 12 , C 13 . Additionally during the first time period, capacitor C 2  of FIG. 1 is discharged. The signal switches s 10 , s 11 , s 12 , s 13  and discharge switch n 2  are thus switched from open to closed at the beginning of the first time period, kept closed during the first time period and then opened again at the end of the first time period. During a second time period the part-coefficient switches k 10 , k 11 , k 12  corresponding to the three most significant bits/capacitors C 10 , C 11 , C 12  can be connected to the output V OUT  and an output circuit, in dependence on the desired weight factor and if an overlap is possible and the output circuit allows it, see above. Additionally during the second time period the charge on capacitor C 13  is shared with capacitor C 2  of FIG. 1, while capacitor C 3  of FIG. 1 is discharged. The signal switch s 2 , discharge switch n 3 , and possibly one or more of the part-coefficient switches k 10 , k 11 , k 12  are thus switched from open to closed at the beginning of the second time period, kept closed during the second time period and then opened again at the end of the second time period. The operation of this enhanced version is actually identical to the operation of the basic version according to FIG. 1 with capacitor C 13  and associated switches s 13 , k 13  working identical to capacitor C 1  and associated switches s 1 , k 1  of figure one and excluding the addition of the operation of the three most significant bit capacitors C 10 , C 11 , C 12  and their corresponding switches s 10 , s 11 , s 12 , k 11 , k 12 , k 13  during the first two time periods (if possible). 
     The control of the switches can be seen in the enhanced control table below. For the MSB-expansion  200  the first three time periods are the most relevant time periods. The enhanced control table also include control of a least significant bit or bits expansion (LSB-expansion) which is discussed below in relation to FIG.  3 . The MSB-expansion  200  can use more capacitors for added MSB part-coefficients or use less capacitors for fewer MSB part-coefficients than shown. For example, using only capacitor C 12  and capacitor C 13  with associated switches s 12 , s 13 , k 12 , k 13  is a visualization of the above described most significant expansion with an optional capacitor. 
     FIG. 3 shows a least significant bit or bits expansion (LSB-expansion)  300 . The LSB-expansion is meant to replace the last sequentally controlled charge sharing capacitor and associated switches of a variable switched capacitor circuit. To facilitate the understanding of the LSB-expansion  300  the replacement is done in relation to FIG.  1 . The LSB-expansion  300  is not restricted to be used with a switched capacitor circuit according to FIG.  1 . The LSB-expansion replaces the last capacitor and associated switches, in this case capacitor C 6  and switches s 6  and n 1  of FIG.  1 . The connection points  301 ,  302 ,  303  of the LSB-expansion  300  of FIG. 3 are connected to the respective connection points  101 ,  102 , 103  of FIG.  1 . 
     The LSB-expansion  300  of FIG. 3 demonstrates an expansion of three least significant bits. The LSB-expansion  300  comprises four capacitors C 60  (comprising four part-capacitors C 60   a , C 60   b , C 60   c , C 60   d  in the figure), C 61  (comprising two part-capacitors C 61   a , C 61   b  in the figure), C 62 , and C 63 . Each capacitor C 60 , C 61 , C 62 , C 63  has its own corresponding discharge switch n 60 , n 61 , n 62 , n 63 , and its own corresponding signal switch s 60 , s 61 , s 62 , s 63 . All the capacitors except the last capacitor C 63  has its own corresponding part-coefficient switch k 60 , k 61 , k 62 . As previously discussed, according to preferred emodiments of the invention, all, or most, of the capacitors should preferably have the same value. In normalized values and with linear binary coefficients, C 6  of FIG. 1, which the LSB-expansion is replacing, should be 1 unit. This means that the capacitors C 60 , C 61 , C 62 , C 63  of the LSB-expansion  300  should make up the same value as C 6  of FIG.  1  and at the same time keep the mutual relationship of C 60  having twice the capacitance of C 61 , which in turn should have twice the capacitance of C 62 , which in turn should have the same capacitance as C 63 . The smallest capacitor in this example will then be one eighth of a unit. Suitably, to keep as accurate a mutual relationship as possible, at least the LSB-expansion is made with the same size capacitors, in this example 0.125 unit capacitors or a division thereof. This means that C 60  is suitably made with four 0.125 unit capacitors C 60   a , C 60   b , C 60   c , C 60   d , and C 61  is made with two 0.125 unit capacitors C 61   a , C 61   b . C 62  and C 63  are made with one 0.125 unit capacitor each. As is explained previously, the capacitance relationship between the capacitors can be different if another coefficient type is desired, such as logarithmic. The rest of the switched capacitor circuit, the capacitors of FIG. 1, can advantageously either be made up of capacitors of 0.125 units each, thus needing eight for each capacitor of FIG. 1, or as previously mentioned of 1 unit each. 
     The part-coefficients that an LSB-expansion will give, will depend on what capacitor the LSB-expansion replaces, i.e. what charge that capacitor would have had and thus what part-coefficient value it represented. The LSB-expansion of FIG. 3 according to the example with FIG. 1 gives, assuming linear binary part-coefficients, a part-coefficient value of 1/64 for part-coefficient switch k 60  for capacitor C 60 , a part-coefficient value of 1/128 for part-coefficient switch k 61  for capacitor C 61 , and a part-coefficient value of 1/256 for part-coefficient switch k 62  for capacitor C 62 . 
     Looking only at the operation of the LSB-expansion  300 , during a first time period the capacitors C 60 , C 61 , C 62 , C 63  are discharged via their corresponding discharge switches n 60 , n 61 , n 62 , n 63 . The signal switch s 5  of FIG.  1  and discharge switches n 60 , n 61 , n 62 , n 63  are thus switched from open to closed at the beginning of the first time period, kept closed during the first time period and then opened again at the end of the first time period. During a second time period of this LSB-expansion  300 , the four capacitors C 60 , C 61 , C 62 , C 63  are connected to capacitor C 5  of FIG. 1 for charge sharing via their corresponding signal switches s 60 , s 61 , s 62 , s 63 . The signal switches s 60 , s 61 , s 62 , s 63  are thus switched from open to closed at the beginning of the second time period, kept closed during the second time period and then opened again at the end of the second time period. During a third time period the part-coefficient switches k 60 , k 61 , k 62  corresponding to the capacitors C 60 , C 61 , C 62  can be connected to the output V OUT  and an output circuit, in dependence on the desired weight factor by switching one or more part-coefficient switches k 60 , k 61 , k 62  from open to closed at the beginning of the third time period, kept closed during the third time period and then opened again at the end of the third time period. 
     The control of the switches can be seen in the enhanced control table below. For the LSB-expansion  300  the fifth, sixth and seventh time periods are the most relevant time periods. The enhanced control table also include control of a most significant bit or bits expansion (MSB-expansion) which is discussed above in relation to FIG.  2 . An LSB-expansion  300  can incorporate more or fewer added LSB part-coefficients. 
     A variable switched value capacitor circuit according to the invention can thus be made as a single chain with charge sharing, or with different combinations of for example capacitance division for MSB, which is advantageous regarding the signal to noise ration, and charge sharing for the rest, and possibly an LSB-expansion. Thus, a switched variable value capacitor circuit according to the invention can be made as a three part pipeline, where for example, the three most significant bits and the three least significant bits are scaled with capacitance division and the bits in between are scaled with charge sharing. Below is an enhanced control table which shows the control of a switched capacitor circuit comprising FIG. 1 except C 1 , s 1 , k 1 , C 6 , s 6 , and n 6  but including the circuits of FIGS. 2 and 3. The most significant bit expansion according to FIG. 2 is coupled via contact points  210 ,  220 ,  230 ,  240  to corresponding contact points  110 ,  120 ,  130 ,  140  of FIG.  1 . The least significant bit expansion according to FIG. 3 is coupled via contact points  301 ,  302 ,  303  to corresponding contact points  101 ,  102 ,  103  of FIG.  1 . The resulting variable value switched capacitor circuit will have an 11 bit resolution. 
     A complete control table of the switches is shown below where all of the empty boxes for the switches denote that the switch in question is open, i.e. non-conducting, a “c” denotes closed, i.e. conducting, and c/o denotes that the switch is either closed or open. For the capacitors the charge Q is shown, this in contrast to the previous two tables where the capacitor voltages were shown. Q 1  denotes the charge from the first sample and Q 2  from the second. The charges will give the part-coefficients for the different capacitors. 
     
       
         
               
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Time Period 
               
             
          
           
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
                 8 
                 9 
                 10 
                 11 
               
               
                   
                   
               
             
          
           
               
                 Reset switch 
               
             
          
           
               
                 n2 
                 c 
                   
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
               
               
                 n3 
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n4 
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n5 
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n60 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n61 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n62 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 n63 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
             
          
           
               
                 Signal switch 
               
             
          
           
               
                 s10 
                 c 
                   
                   
                   
                 c 
                   
                   
                   
                   
                   
                   
               
               
                 s11 
                 c 
                   
                   
                   
                 c 
               
               
                 s12 
                 c 
                   
                   
                   
                 c 
               
               
                 s13 
                 c 
                   
                   
                   
                 c 
               
               
                 s2 
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s3 
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s4 
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s5 
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s60 
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s61 
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s62 
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
               
                 s63 
                   
                   
                   
                   
                   
                 c 
                   
                   
                   
                 c 
               
             
          
           
               
                 Part-Coefficient switch 
               
             
          
           
               
                 k10 
                   
                 c/0 
                   
                   
                   
                 c/o 
                   
                   
                   
                   
                   
               
               
                 k11 
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k12 
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k13 
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k2 
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k3 
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k4 
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k5 
                   
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k60 
                   
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k61 
                   
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
               
                 k62 
                   
                   
                   
                   
                   
                   
                 c/o 
                   
                   
                   
                 c/o 
               
             
          
           
               
                 Capacitor charge 
               
             
          
           
               
                 4*C10x 
                 4Q 1   
                 4Q 1   
                   
                   
                 4Q 2   
                 4Q 2   
                   
                   
                   
                   
                   
               
               
                 2*C11x 
                 2Q 1   
                 2Q 1   
                   
                   
                 2Q 2   
                 2Q 2   
               
               
                 C12 
                 Q 1   
                 Q 1   
                   
                   
                 Q 2   
                 Q 2   
               
               
                 C13 
                 Q 1   
                 Q 1 /2 
                 Q 1 /2 
                   
                 Q 2   
                 Q 2 /2 
                 Q 2 /2 
               
               
                 C2 
                 0 
                 Q 1 /2 
                 Q 1 /4 
                 Q 1 /4 
                 0 
                 Q 2 /2 
                 Q 2 /4 
                 Q 2 /4 
               
               
                 C3 
                   
                 0 
                 Q 1 /4 
                 Q 1 /8 
                 Q 1 /8 
                 0 
                 Q 2 /4 
                 Q 2 /8 
                 Q 2 /8 
               
               
                 C4 
                   
                   
                 0 
                 Q 1 /8 
                 Q 1 /16 
                 Q 1 /16 
                 0 
                 Q 2 /8 
                 Q 2 /16 
                 Q 2 /16 
               
               
                 C5 
                   
                   
                   
                 0 
                 Q 1 /16 
                 C 1 /32 
                 C 1 /32 
                 0 
                 Q 2 /16 
                 Q 2 /32 
                 Q 2 /32 
               
               
                 4*C60x 
                   
                   
                   
                   
                 0 
                 Q 1 /64 
                 Q 1 /64 
                   
                 0 
                 Q 2 /64 
                 Q 2 /64 
               
               
                 2*C61x 
                   
                   
                   
                   
                 0 
                 Q 1 /128 
                 Q 1 /128 
                   
                 0 
                 Q 2 /128 
                 Q 2 /128 
               
               
                 C62 
                   
                   
                   
                   
                 0 
                 Q 1 /256 
                 Q 1 /256 
                   
                 0 
                 Q 2 /256 
                 Q 2 /256 
               
               
                 C63 
                   
                   
                   
                   
                 0 
                 Q 1 /256 
                   
                   
                 0 
                 Q 2 /256 
               
               
                   
               
             
          
         
       
     
     The described basic embodiments of the invention have only been for positive coefficients/weight factors. Only the embodiments which do not use any interleaving/overlap/pipelining can use inversion of the input terminals to the output circuit, as both positive and negative coefficients can appear simultaneously. One possible solution for the other embodiments that use interleaving can be time multiplexing between positive and negative coefficients, which can sometimes be considered to be time consuming. Another possibility is to split the output circuit, most commonly an integrator, into two circuits, one for negative values and one for positive values which are thereafter put together. A third solution is to build the whole circuit completely differential, then the sign of the coefficient can be decided at sampling by inverting the input signal and the sign is then automatically propagated through the pipeline so that all the bits of the coefficient gets the correct sign. This solution is advantageous also from an electrical interference point of view (common mode rejection). 
     FIG. 1 
       100  switched capacitor circuit 
       101  connection point for LSB enhancement of for example FIG. 3, connection point  301   
       102  connection point for LSB enhancement of for example FIG. 3, connection point  302   
       103  connection point for LSB enhancement of for example FIG. 3, connection point  303   
       110  connection point for MSB enhancement of for example FIG. 2, connection point  210   
       120  connection point for MSB enhancement of for example FIG. 2, connection point  220   
       130  connection point for MSB enhancement of for example FIG. 2, connection point  230   
       140  connection point for MSB enhancement of for example FIG. 2, connection point  240   
       199  optional output circuit, integrator 
     OP operational amplifier 
     C i  integrator capacitor 
     n i  integrator capacitor C i  nullification/discharge switch 
     n 2  nullification/discharge switch for capacitor C 2   
     n 3  nullification/discharge switch for capacitor C 3   
     n 4  nullification/discharge switch for capacitor C 4   
     n 5  nullification/discharge switch for capacitor C 5   
     n 6  nullification/discharge switch for capacitor C 6   
     s 1  charge switch for capacitor C 1   
     s 2  charge switch for capacitor C 2   
     s 3  charge switch for capacitor C 3   
     s 4  charge switch for capacitor C 4   
     s 5  charge switch for capacitor C 5   
     s 6  charge switch for capacitor C 6   
     k 1  part-coefficient switch for capacitor C 1   
     k 2  part-coefficient switch for capacitor C 2   
     k 3  part-coefficient switch for capacitor C 3   
     k 4  part-coefficient switch for capacitor C 4   
     k 5  part-coefficient switch for capacitor C 5   
     C 1  capacitor 
     C 2  capacitor 
     C 3  capacitor 
     C 4  capacitor 
     C 5  capacitor 
     C 6  capacitor 
     FIG. 2 
       200  most significant bits expansion with parallel operated capacitors 
       210  connection point to for example switched capacitor circuit of FIG. 1, connection point  110   
       220  connection point to for example switched capacitor circuit of FIG. 1, connection point  120   
       230  connection point to for example switched capacitor circuit of FIG. 1, connection point  130   
       240  connection point to for example switched capacitor circuit of FIG. 1, connection point  140   
     s 10  charge switch for capacitor C 10   
     s 11  charge switch for capacitor C 11   
     s 12  charge switch for capacitor C 12   
     s 13  charge switch for capacitor C 13   
     k 10  part-coefficient switch for capacitor CdO 
     k 11  part-coefficient switch for capacitor C 11   
     k 12  part-coefficient switch for capacitor C 12   
     k 13  part-coefficient switch for capacitor C 13   
     C 10  capacitor 
     C 10   a  part-capacitor for making C 10   
     C 10   b  part-capacitor for making C 10   
     C 10   c  part-capacitor for making C 10   
     C 10   d  part-capacitor for making C 10   
     C 11  capacitor 
     C 11   a  part-capacitor for making C 11   
     C 11   b  part-capacitor for making C 11   
     C 12  capacitor 
     C 13  capacitor 
     FIG. 3 
       300  least significant bits expansion with parallel operated capacitors 
       301  connection point to for example switched capacitor circuit of FIG. 1, connection point  101   
       302  connection point to for example switched capacitor circuit of FIG. 1, connection point  102   
       303  connection point to for example switched capacitor circuit of FIG. 1, connection point  103   
     n 60  nullification/discharge switch for capacitor C 60   
     n 61  nullification/discharge switch for capacitor C 61   
     n 62  nullification/discharge switch for capacitor C 62   
     n 63  nullification/discharge switch for capacitor C 63   
     s 60  charge switch for capacitor C 60   
     s 61  charge switch for capacitor C 61   
     s 62  charge switch for capacitor C 62   
     s 63  charge switch for capacitor C 63   
     k 60  part-coefficient switch for capacitor C 60   
     k 61  part-coefficient switch for capacitor C 61   
     k 62  part-coefficient switch for capacitor C 62   
     C 60  capacitor 
     C 60   a  part-capacitor for making C 60   
     C 60   b  part-capacitor for making C 60   
     C 60   c  part-capacitor for making C 60   
     C 60   d  part-capacitor for making C 60   
     C 61  capacitor 
     C 61   a  part-capacitor for making C 61   
     C 61   b  part-capacitor for making C 61   
     C 62  capacitor 
     C 63  capacitor