Ex parte MONTI et al. - Page 10

              Appeal No. 95-3917                                                                                                                          
              Application 07/861,144                                                                                                                      

              35 U.S.C.  103                                                                                                                             

                       Hochschild and Merrick                                                                                                             

                       Figure 1 of Hochschild shows an operational amplifier 10 having a feedback resistor network                                        

              comprising four series-connected resistors 40, 42, 44, and 48 in parallel with series-connected resistors                                   

              36, 38 in parallel with resistor 34.  The transistors 28, 30, and 32 are connected in series in each of the                                 

              parallel paths.  The examiner concludes that "it would have been obvious to one skilled in the art to use a                                 

              similar decoder to control each of the Digitally Controlled Resistors in the circuit disclosed to Hochschild                                

              for the expected additive result of having less control lines" (Examiner's Answer, page 5).  We agree that                                  

              it would have been obvious to use a digital signal and decoder as taught in Merrick to control the transistors                              

              of Hochschild.  Equally apparent is that it would have been obvious to use parallel-connected resistors as                                  

              taught by Hochschild in place of the series-connected resistors in Merrick to achieve the same result of a                                  

              variable resistance between two points.  Moreover, we think that the use of parallel-connected resistors                                    

              would have been obvious even without a reference since the person of ordinary skill in the art would have                                   

              known that whatever could be done with series-connected resistors could be done with an equivalent                                          

              circuit of parallel-connected resistors.  Note that Merrick describes that "[t]he internal circuit of the digitally                         

              controlled resistance D  is schematically represented by series resistors r , r  and r  that are respectivelyR                                                    1  2       3                                              

              shunted by switches s , s  and s ; but in actuality, the resistor connections would be much more1   2       3                                                                                                    
              complicated" (column 18, lines 57-61).                                                                                                      

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