Abstract:
A reference voltage device and a reference voltage generating method thereof. The reference voltage device comprises a bandgap unit, a voltage generating unit, a comparator, and a calibration controller. The calibration controller controls the voltage generating unit to generate a final calibrating voltage to serve as an ideal target voltage. The bandgap unit generates a bandgap voltage with zero offset voltage according to the final calibrating voltage to serve as a reference voltage. The variation of the reference voltage output by the reference voltage device is thus reduced.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a reference voltage generating method, and in particular relates to a reference voltage device. 
   2. Description of the Related Art 
   Integrated circuits often require a reference voltage which remains stable under PVT (process, voltage, temperature) variations.  FIG. 1  depicts a conventional generating circuit of a bandgap voltage serving as a reference voltage for integrated circuits. Referring to  FIG. 1 , the generating circuit  1  comprises an operational amplifier OPAMP, bipolar devices B 11  and B 12 , and resistors R 11  to R 13 . The values of the resistors R 11  and R 12  are the same. The operational amplifier OPAMP of a high gain is used, and base-emitter voltage Vbe 1  and Vbe 1 ′ are almost equal due the closed loop. A bandgap voltage Vbg is determined according to the base-emitter voltage Vbe 1  and Vbe 2  (negative temperature coefficient) and thermal voltage V T  (positive temperature coefficient) of the bipolar devices B 11  and B 12 . With a proper ratio of the base-emitter voltage and the thermal voltage V T  for each bipolar, the temperature dependence of the bandgap voltage Vbg is almost eliminated. 
   However, because the area of the bipolar devices B 11  and B 12  is different, the current density in the bipolar devices B 11  and B 12  is also different, thus, the base-emitter voltage Vbe 1  and Vbe 2  of the bipolar devices B 11  and B 12  becomes unequal. Accordingly, the same current density in different areas of the bipolar devices B 11  and B 12  results in a current magnitude which is equal to ΔVbe/R 13  and provides a positive temperature coefficient. The bandgap voltage Vbg is then determined according to the base-emitter voltage Vbe 1  and a scale of ΔVbe and expressed as: 
   
     
       
         
           Vbg 
           = 
           
             
               Vbe 
               ⁢ 
               
                   
               
               ⁢ 
               1 
             
             + 
             
               
                 
                   R 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   12 
                 
                 
                   R 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   13 
                 
               
               × 
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               Vbe 
             
           
         
       
     
   
   Typically, the ratio of the resistors R 12  and R 11  is equal to about 10 to nullify the temperature coefficient. 
     FIG. 2  depicts another conventional generating circuit of a bandgap voltage operating at low voltage, serving as a reference voltage for integrated circuits. Referring to  FIG. 2 , the generating circuit  2  mainly comprises an operational amplifier OPAMP, bipolar devices B 21  and B 22 , and resistors R 21  to R 24 . The values of the resistor R 21  and R 22  are the same. A bandgap voltage can be scaled freely by adjusting the ratio of the resistors and expressed as: 
   
     
       
         
           Vbg 
           = 
           
             
               
                 R 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 24 
               
               
                 R 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 22 
               
             
             = 
             
               × 
               
                 ( 
                 
                   
                     Vbe 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   + 
                   
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         22 
                       
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         23 
                       
                     
                     × 
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Vbe 
                   
                 
                 ) 
               
             
           
         
       
     
   
   According to the two generating circuits  1  and  2 , the bandgap voltage of the generating circuit  2  is equal to R 24 /R 22  of that of the generating circuit  1 . 
   In above generating circuits  1  and  2 , it is assumed that the operational amplifier OPAMP is ideal, meaning that the voltage of the two input terminals of the operational amplifier OPAMP is ideally equal. In practice, however, the voltage of two input terminals of the operational amplifier OPAMP is not equal, and there is a non-zero offset voltage Vos between the two input terminals. When the non-zero offset voltage Vos is considered, the generating circuit  1  of  FIG. 1  is redrawn as in  FIG. 3 , and a bandgap voltage Vbg′ is expressed as: 
   
     
       
         
           
             
               
                 
                   Vbg 
                   ′ 
                 
                 = 
                 
                   
                     Vbe 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   + 
                   
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         12 
                       
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         13 
                       
                     
                     × 
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     Vbe 
                   
                   + 
                   
                     
                       ( 
                       
                         1 
                         + 
                         
                           
                             R 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             12 
                           
                           
                             R 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             13 
                           
                         
                       
                       ) 
                     
                     × 
                     Vos 
                   
                 
               
             
             
               
                 ( 
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
                 ) 
               
             
           
         
       
     
   
   Similarly, when the non-zero offset voltage Vos is considered, a bandgap voltage Vbg′ generated by the generating circuit  2  of  FIG. 2  is expressed as: 
   
     
       
         
           
             
               
                 
                   Vbg 
                   ′ 
                 
                 = 
                 
                     
                 
                 ⁢ 
                 
                   
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       24 
                     
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       22 
                     
                   
                   × 
                   
                     [ 
                     
                       ( 
                       
                         
                           Vbe 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                         + 
                         
                           
                             
                               R 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               22 
                             
                             
                               R 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               23 
                             
                           
                           × 
                           Δ 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           Vbe 
                         
                         + 
                         
                           
                             ( 
                             
                               1 
                               + 
                               
                                 
                                   R 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   22 
                                 
                                 
                                   R 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   23 
                                 
                               
                             
                             ) 
                           
                           × 
                           Vos 
                         
                       
                       ] 
                     
                   
                 
               
             
             
               
                 ( 
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
                 ) 
               
             
           
         
       
     
   
   According to Equation 1 and Equation 2, the non-zero offset voltage Vos of the operational amplifier OPAMP is amplified by (1+R 22 /R 23 ). As described previously, in order to nullify temperature dependence of the bandgap voltage, the ratio of the resistors R 2  and R 1  is set to about 10. Thus, when the non-zero offset voltage Vos is considered, the bandgap voltage Vbg may drift from its ideal value by 10 times the non-zero offset voltage Vos. The amplified non-zero offset voltage Vos causes the reference voltage to vary greatly from chip to chip. 
   In order to reduce the variation of the reference voltage from chip to chip, several techniques are introduced. One method uses a trimming circuit.  FIG. 4  depicts a trimming circuit. A bandgap voltage Vbg′ with a non-zero offset voltage Vos is amplified by an amplifier  40 , and a trimmed output voltage Vref is selected from a resistor string  41 . At the beginning of the trimming process, an ideal target voltage value is applied to an external tester and compared with an output voltage Vref of the trimming circuit. The output voltage Vref is selected by varying a final control code CODE 40  which is determined according to the comparison result signal. When the output voltage Vref is equal to the ideal target voltage value, the final control code CODE 40  is obtained. According to the final control code CODE 40 , the trimmed output voltage Vref is determined. The ideal target voltage value and the trimmed output voltage Vref can be fixed and remembered in an IC by fuses which can be programmed by laser or electronically. The trimming process, however, requires more time in the tester for calibration and fuses trimming. 
   Chopper stabilization is another method to reduce the variation in the reference voltage. U.S. Pat. No. 6,462,612 discloses a chopper stabilized bandgap reference circuit to cancel offset variation. Referring to  FIG. 5 , an input signal of an amplifier  51  is modulated by a high frequency modulator (MOD)  50 . The modulated signal is amplified by the amplifier  51  and demodulated by a demodulator (DEMOD)  52 . Since an offset voltage of the amplifier  51  is not modulated, the offset voltage is modulated to a high frequency in the demodulation process. The high frequency noise can be filtered by a low pass filter (LPF)  53 . The chopper stabilized bandgap reference circuit is useful to reduce the variation caused by the offset voltage of the amplifier  51 . The circuit requires a high frequency clock for modulation, however, which produces noise. Moreover, the low pass filter  53  occupies a large area. 
   BRIEF SUMMARY OF THE INVENTION 
   An exemplary embodiment of a method for calibrating a bandgap voltage generated by a bandgap unit is provided. The bandgap unit comprises an operational amplifier. The method comprises switching a first input with a second input of the operational amplifier to measure a first bandgap voltage and a second bandgap voltage respectively, averaging the first bandgap voltage and the second bandgap voltage to generate a calibration voltage, and modifying the bandgap voltage so that a resulting bandgap voltage is equal to the calibration voltage. 
   An exemplary embodiment of a calibration circuit for calibrating an input offset of an operational amplifier is provided. The operational amplifier is used in a bandgap unit. The calibration circuit comprises a comparator, a calibration controller, and a voltage DAC. The comparator receives a bandgap voltage and a calibration voltage. The bandgap voltage is generated by the bandgap unit and the comparator generates a comparison result signal. The calibration controller receives the comparison result signal to generate a digital code and generates a control code to adjust the bandgap voltage. The voltage DAC receives the digital code to generate the calibration voltage. 
   An exemplary embodiment of a reference voltage generating method for a reference voltage device is provided. The reference voltage comprises a bandgap unit which alternately operates in two modes. The reference voltage generating method comprises, for each mode of the bandgap unit, setting an operation mode of the bandgap unit to one of the two modes, generating a calibration voltage based a first control code, comparing the calibration voltage with a bandgap voltage output by the bandgap unit to generate a first comparison result signal to indicate whether or not the calibration voltage is greater than the bandgap voltage, adjusting the first control code to modify the calibration voltage based on the first comparison result signal, and recoding the first control code when the calibration voltage is substantially equal to the bandgap voltage. The reference voltage generating method further comprises generating a second control code by averaging the first control codes, generating the calibration voltage to form a final calibration voltage based on the second control code, and generating the bandgap voltage of the bandgap unit based on the final calibration voltage to serve as the reference voltage. 
   An exemplary embodiment of a reference voltage device is provided. The reference voltage device comprises a bandgap unit, a voltage generating unit, a comparator, and a calibration controller. The bandgap unit alternately operates in two modes according to a selected signal and generates a bandgap voltage. The voltage generating unit receives a first control code and generates a calibrating voltage according to the first control code in each mode of the bandgap unit. The comparator receives and compares the bandgap voltage and the calibrating voltage, and generates a first comparison result signal according to the comparison result in each mode of the bandgap unit. The first comparison result signal indicates whether or not the calibrating voltage is greater than the bandgap voltage. The calibration controller receives the first comparison result signal, adjusts the first control code to modify the calibrating voltage based on the first comparison result signal, and recodes the first control code when the calibrating voltage is substantially equal to the bandgap voltage in each mode of the bandgap unit. 
   The calibration controller generates a second control code by averaging the recoded first control codes in the first and second modes. The voltage generating unit generates the calibration voltage to form a final calibrating voltage based on the second control code. The bandgap unit generates the bandgap voltage based on the final calibrating voltage to serve as the reference voltage. 
   A detailed description is given in the following embodiments with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
       FIG. 1  depicts a conventional generating circuit of a bandgap voltage; 
       FIG. 2  depicts another conventional generating circuit of a bandgap voltage operating t low voltage; 
       FIG. 3  shows a non-zero offset voltage Vos of a conventional generating circuit of a bandgap voltage in  FIG. 1 ; 
       FIG. 4  depicts a trimming circuit; 
       FIG. 5  shows a chopper stabilized bandgap reference circuit to cancel offset variation; 
       FIG. 6  depicts an embodiment of a reference voltage device; 
       FIG. 7  depicts an embodiment of a voltage generating unit in  FIG. 6 ; 
       FIG. 8  depicts an embodiment of a bandgap unit in  FIG. 6 ; 
       FIG. 9  shows a circuit of an operational amplifier in  FIG. 8 ; and 
       FIG. 10  is a flow chart of an embodiment of a reference voltage generating method. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
   Reference voltage devices are provided. In the exemplary embodiment of a reference voltage device of  FIG. 6 , a reference voltage device  6  generates a reference voltage and comprises a bandgap unit  60 , a voltage generating unit  61 , a comparator  62 , and a calibration controller  63 . The bandgap unit  60  alternately operates in first and second modes and outputs a bandgap voltage Vbg. In this embodiment, the bandgap unit  60  is implemented by the generating circuit  1  in  FIG. 1 , without limitation. 
   First, the operation mode of the bandgap unit  60  is set to the first mode according to a selecting code MODE provided by the calibration controller  63 . The calibration controller  63  provides a first control code CODE_C 1  to the voltage generating unit  61 . The voltage generating unit  61  generates a calibration voltage Vref based the first control code CODE_C 1 . The bandgap voltage Vbg has a positive offset voltage in the first mode and serves as a bandgap voltage Vbg_high, and the bandgap voltage Vbg_high is expressed as: 
   
     
       
         
           Vbg_high 
           = 
           
             
               Vbe 
               ⁢ 
               
                   
               
               ⁢ 
               1 
             
             + 
             
               
                 
                   R 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   12 
                 
                 
                   R 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   13 
                 
               
               × 
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               Vbe 
             
             + 
             
               
                 ( 
                 
                   1 
                   + 
                   
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       12 
                     
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       13 
                     
                   
                 
                 ) 
               
               × 
               Vos 
             
           
         
       
     
   
   The comparator  62  compares the calibration voltage Vref with the bandgap voltage Vbg_high to generate a first comparison result signal S_ 1  to indicate the calibration voltage Vref is greater than the bandgap voltage Vbg_high or not. The calibration controller  63  adjusts the first control code CODE_C 1  to modify the calibration voltage Vref based on the first comparison result signal S_ 1 . When the calibration voltage Vref is substantially equal to the bandgap voltage Vbg_high, the calibration controller  63  recodes the first control code CODE_C 1  to be a code CODE_HIGH. 
   Then, the operation mode of the bandgap unit is set to the second mode according to the selecting code MODE. The voltage generating unit  61  generates the calibration voltage Vref based the first control code CODE_C 1 . The bandgap voltage Vbg has a negative offset voltage in the second mode and serves as a bandgap voltage Vbg_low, and the bandgap voltage Vbg_low is expressed as: 
   
     
       
         
           Vbg_low 
           = 
           
             
               Vbe 
               ⁢ 
               
                   
               
               ⁢ 
               1 
             
             + 
             
               
                 
                   R 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   12 
                 
                 
                   R 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   13 
                 
               
               × 
               Δ 
               ⁢ 
               
                   
               
               ⁢ 
               Vbe 
             
             - 
             
               
                 ( 
                 
                   1 
                   + 
                   
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       12 
                     
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       13 
                     
                   
                 
                 ) 
               
               × 
               Vos 
             
           
         
       
     
   
   The comparator  62  compares the calibration voltage Vref with the bandgap voltage Vbg_low to generate the first comparison result signal S_ 1  to indicate the calibration voltage Vref is greater than the bandgap voltage Vbg_low or not. The calibration controller  63  adjusts the first control code CODE_C 1  to modify the calibration voltage Vref based on the first comparison result signal S_ 1 . When the calibration voltage Vref is substantially equal to the bandgap voltage Vbg_low, the calibration controller  63  recodes the first control code CODE_C 1  to be a code CODE_LOW. 
   After the first and second modes, the calibration controller  63  generates a second control code CODE_C 2  by averaging the codes CODE_HIGH and CODE_LOW. 
   The voltage generating unit  61  generates the calibration voltage Vref to yield a final calibration voltage Vref_F based on the second control code CODE_C 2 . The final calibration voltage Vref_F is expressed as: 
   
     
       
         
           Vref_F 
           = 
           
             
               
                 1 
                 2 
               
               ⁢ 
               
                 ( 
                 
                   Vbg_high 
                   + 
                   Vbg_low 
                 
                 ) 
               
             
             = 
             
               Vbe 
               + 
               
                 
                   
                     R 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     12 
                   
                   
                     R 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     13 
                   
                 
                 × 
                 Δ 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 Vbe 
               
             
           
         
       
     
   
   According to the above equation, the variation due to OPAMP offset voltage of the bandgap unit  60  is removed. The comparator  62  compares the bandgap voltage Vbg with the final calibration voltage Vref_F to generate a second comparison result signal S_ 2  to indicate the bandgap voltage Vbg is greater than the final calibration voltage Vref_F or not. The calibration controller  63  adjusts a third control code CODE_C 3  to modify the bandgap voltage Vbg based on the second comparison result signal S_ 2 . When the bandgap voltage Vbg is substantially equal to the final calibration voltage Vref_F, the bandgap unit  60  outputs the bandgap voltage Vbg to serve as the reference voltage. After a final version of the third control code CODE_C 3  is sent to adjust the bandgap voltage Vbg, the voltage generating unit  61 , the comparator  62 , and the calibration controller  63  can be powered down to save power. The voltage generating unit  61  can also be powered down after the third control code CODE_C 3  is sent to adjust the bandgap voltage Vbg. 
   In this embodiment, the first control code CODE_C 1  and the second control code CODE_C 2  can be digital signals, and the voltage generating unit  61  can be a voltage digital/analog converter (DAC), as shown in  FIG. 7 . A voltage DAC  7  receives first control code CODE_C 1  of n bits and outputs the calibration voltage Vref in the first and second modes, or receives the second control code CODE_C 2  of n bits and outputs the final calibration voltage Vref_F. The voltage DAC  7  comprises n current sources  70   0  to  70   n-1 , n switches  71   0  to  71   n-1 , and a resistor  72 . 
     FIG. 8  depicts an embodiment of the bandgap unit  60 . The bandgap unit  60  comprises transistors  801  to  803 , resistors R 81  to R 83 , bipolar transistors B 81  and B 82 , an operational amplifier  81 , and a variable resistor R 84 . The values of the resistors R 81  and R 82  are the same. The variable resistor R 84  is controlled by the third control code CODE_C 3 .  FIG. 9  shows a circuit of the operational amplifier  81  of the bandgap unit  60  in  FIG. 8 . The operational amplifier  83  is controlled by a clock CK and an inverse clock CKb, wherein the selecting code MODE serves as the clock CK, and an inverse code of the selecting code MODE serves as the inverse clock CKb. 
     FIG. 10  is a flowchart of an embodiment of a reference voltage generating method for a reference voltage device. The reference voltage device comprises a bandgap unit which alternately operates in two modes. A calibration controller provides a selecting code MODE (step S 100 ) to indicate the operation mode of the bandgap unit is the first or second mode. The operation mode of the bandgap unit is set according to the selecting code MODE (step  101 ). First, the operation mode of the bandgap unit is set to the first mode. The calibration controller provides a first control code CODE_C 1  to a voltage generating unit. The voltage generating unit generates a calibration voltage Vref (step S 102 ) based the first control code CODE_C 1 . The bandgap unit outputs a bandgap voltage Vbg. In the first mode, the bandgap voltage Vbg has a positive offset voltage and serves as a bandgap voltage Vbg_high. 
   A comparator compares the calibration voltage Vref with the bandgap voltage Vbg_high to generate a first comparison result signal S_ 1  (step S 103 ), and the first comparison result signal S_ 1  indicates whether or not the calibration voltage Vref is greater than the bandgap voltage Vbg_high. The calibration controller adjusts the first control code CODE_C 1  to modify the calibration voltage Vref based on the first comparison result signal S_ 1  (step S 104 ). When the calibration voltage Vref is substantially equal to the bandgap voltage Vbg_high, the calibration controller recodes the first control code CODE_C 1  to be a code CODE_HIGH (step S 105 ). 
   The operation mode of the bandgap unit is then set to the second mode, and the steps S 102  to S 104  are repeated. The calibration controller provides the first control code CODE_C 1  to the voltage generating unit. The voltage generating unit generates the calibration voltage Vref (step S 102 ) based the first control code CODE_C 1 . In the second mode, the bandgap voltage Vbg has a negative offset voltage and serves as a bandgap voltage Vbg_low. The comparator compares the calibration voltage Vref with the bandgap voltage Vbg_low to generate the first comparison result signal S_ 1  (step S 103 ), and the first comparison result signal S_ 1  indicates whether or not the calibration voltage Vref is greater than the bandgap voltage Vbg_low. The calibration controller adjusts the first control code CODE_C 1  to modify the calibration voltage Vref based on the first comparison result signal S_ 1  (step S 104 ). When the calibration voltage Vref is substantially equal to the bandgap voltage Vbg_low, the calibration controller recodes the first control code CODE_C 1  to be a code CODE_LOW (step S 105 ). 
   After the first and second modes, the calibration controller generates a second control code CODE_C 2  by averaging the codes CODE_HIGH and CODE_LOW (step S 106 ). The voltage generating unit generates the calibration voltage Vref to yield a final calibration voltage Vref_F based on the second control code CODE_C 2  (step S 107 ). The comparator compares the bandgap voltage Vbg with the final calibration voltage Verf_F to generate a second comparison result signal S_ 2  (step S 108 ). The second comparison result signal S_ 2  indicates whether or not the bandgap voltage Vbg is greater than the final calibration voltage Vref_F. The calibration controller adjusts a third control code CODE_C 3  to modify the bandgap voltage based Vbg on the second comparison result signal S_ 2  (step  109 ). When the bandgap voltage Vbg is substantially equal to the final calibration voltage Vref_F. the bandgap unit outputs the bandgap voltage Vbg to serve as the reference voltage (step S 110 ). 
   According to the invention, a reference voltage is generated without a non-zero offset voltage. The invention does not require an area consuming low pass filter. The low pass filter is replaced by digital averaging. Moreover, no high frequency modulation is performed, thus, noise is reduced. 
   While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.