<PAGE>   1
                                                                      Exhibit 11

               Unitrode Corporation and Consolidated Subsidiaries
           Computation of Primary and Fully Diluted Earnings per Share
                      (in thousands except per share data)


<TABLE>
<CAPTION>
Three months ended                                     November 1, 1997    October 26, 1996
<S>                                                    <C>                 <C>
Net income                                                 $ 8,850              $ 4,985
                                                           =======              =======
                                                                             
Primary earnings per share:                                                  
Weighted average of common shares outstanding               24,053               23,094
Equivalent shares arising from the assumed                                   
  exercise of stock options                                  1,406                  457
                                                           -------              -------
Weighted average of common and common                                        
  equivalent shares outstanding                             25,459               23,551
                                                           =======              =======
                                                                             
Net income                                                 $   .35              $   .21
                                                           =======              =======
                                                                             
Fully diluted earnings per share:                                            
Weighted average of common and common                                        
  equivalent shares outstanding                                              
  (as determined for Primary earnings                                        
  per share above)                                          25,459               23,551
Incremental shares to reflect full                                           
  dilution                                                       1(1)                99(1)
                                                           -------              -------
Weighted average of common and common                                        
  equivalent shares outstanding, as                                          
  adjusted                                                  25,460               23,650
                                                           =======              =======
                                                                             
Net income                                                 $   .35              $   .21
                                                           =======              =======
</TABLE>
                                                                             
(1)      This calculation is submitted in accordance with Regulation S-K item
         601(b)(11) although not required by footnote 2 to paragraph 14 of APB
         Opinion No. 15 because it results in dilution of less than 3%.
<PAGE>   2
                                                                      Exhibit 11

               Unitrode Corporation and Consolidated Subsidiaries
           Computation of Primary and Fully Diluted Earnings per Share
                      (in thousands except per share data)


<TABLE>
<CAPTION>
Nine months ended                                      November 1, 1997         October 26, 1996
<S>                                                    <C>                      <C>
Net income                                                  $23,554                  $14,954
                                                            =======                  =======
                                                                               
Primary earnings per share:                                                    
Weighted average of common shares outstanding                23,645                   23,024
Equivalent shares arising from the assumed                                     
  exercise of stock options                                   1,275                      621
                                                            -------                  -------
Weighted average of common and common                                          
  equivalent shares outstanding                              24,920                   23,645
                                                            =======                  =======
                                                                               
 Net income                                                 $   .95                  $   .63
                                                            =======                  =======
                                                                               
Fully diluted earnings per share:                                              
Weighted average of common and common                                          
  equivalent shares outstanding                                                
  (as determined for Primary earnings                                          
  per share above)                                           24,920                   23,645
Incremental shares to reflect full                                             
  dilution                                                      117(1)                    34(1)
                                                            -------                  -------
Weighted average of common and common                                          
  equivalent shares outstanding, as                                            
  adjusted                                                   25,037                   23,679
                                                            =======                  =======
                                                                               
 Net income                                                 $   .94                  $   .63
                                                            =======                  =======
</TABLE>
                                                                               
(1)      This calculation is submitted in accordance with Regulation S-K item
         601(b)(11) although not required by footnote 2 to paragraph 14 of APB
         Opinion No. 15 because it results in dilution of less than 3%.