<PAGE>   1


                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON D.C. 20549

                                    FORM 10-Q

(Mark One)

[X]  QUARTERLY REPORT PURSUANT TO SECTION 13 or 15(d) OF THE SECURITIES EXCHANGE
     ACT OF 1934

                 For the quarterly period ended OCTOBER 31, 1998

                                       OR

[ ]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
     EXCHANGE ACT OF 1934

                For the transition period from _______ to _______

                          Commission file number 1-5609

                              UNITRODE CORPORATION
             (Exact name of registrant as specified in its charter)

             MARYLAND                                     04-2271186
   (State or other jurisdiction of                     (I.R.S. Employer
    incorporation or organization)                      Identification No.)

             7 CONTINENTAL BOULEVARD, MERRIMACK, NEW HAMPSHIRE 03054
               (Address of principal executive offices) (Zip Code)

       Registrant's telephone number, including area code: (603) 424-2410

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of Securities Exchange Act of 1934 during the
preceding 12 months (or for such shorter period that the registrant was required
to file such reports), and (2) has been subject to such filing requirements for
the past 90 days. Yes   X    No
                      -----     -----

There were 31,706,255 shares of common stock outstanding as of October 31, 1998.


                                       -1-


<PAGE>   2


                          PART I. FINANCIAL INFORMATION

Item 1. Financial Statements

               Unitrode Corporation and Consolidated Subsidiaries
                                 Balance Sheets
                                 (in thousands)

<TABLE>
<CAPTION>
                                           October 31, 1998  January 31, 1998
Assets                                        (Unaudited)                     
-------------------------------------------------------------------------------
<S>                                            <C>               <C>     
Current assets:                                               
  Cash and cash equivalents                    $ 78,603          $ 67,956
  Short-term investments                              -            17,061
  Accounts receivable, net of allowance                       
     of $507 in October, 1998                                 
     and $489 in January, 1998                   24,008            29,109
  Notes receivable                                  725               709
  Inventories:                                                
     Raw materials                                1,839             2,654
     Work in process                             14,143             9,998
     Finished goods                               6,462             5,082
                                               --------          --------
       Total inventories                         22,444            17,734
                                               --------          --------
                                                              
  Deferred income taxes                           6,225             8,744
  Prepaid expenses and other                                  
    current assets                                3,719             4,201
                                               --------          --------
                                                              
     Total current assets                       135,724           145,514
                                               --------          --------
                                                              
Property, plant and equipment, at cost          152,275           151,671
  Less accumulated depreciation                  75,080            68,019
                                               --------          --------
    Property, plant and equipment, net           77,195            83,652
                                               --------          --------
                                                              
Prepayment for production purchases               3,360             3,360
Notes and other receivables, net                              
  of discount                                     2,443             2,828
Deferred income taxes                                 -               403
Restricted cash and investments                     985             1,180
Excess of cost over net assets acquired,                      
   net of accumulated amortization of                         
   $2,607 in October, 1998 and                                
   $2,394 in January, 1998                        1,483             1,696
Other assets and deferred charges                 1,848             4,254
                                               --------          --------
                                                              
Total assets                                   $223,038          $242,887
                                               ========          ========
</TABLE>                                                      
                                                           

    The accompanying notes are an integral part of the financial statements.


                                       -2-


<PAGE>   3


               Unitrode Corporation and Consolidated Subsidiaries
                                 Balance Sheets
                        (in thousands except share data)
<TABLE>
<CAPTION>

                                               October 31, 1998 January 31, 1998
Liabilities and Stockholders' Equity              (Unaudited)           
--------------------------------------------------------------------------------
<S>                                                <C>              <C>     
Current liabilities:
  Accounts payable                                 $  9,507         $ 16,125
  Income taxes payable                                  956            4,282
  Accrued employee compensation and benefits          2,259           11,155
  Accrued distributor liability                       6,028            3,348
  Capital lease obligations                             588            1,229
  Deferred income on shipments to distributors            -            1,250
  Other current liabilities                           5,475            7,758
                                                   --------         --------

     Total current liabilities                       24,813           45,147
                                                   --------         --------

Deferred income taxes                                 1,670            2,322
Capital lease obligations                               321              702
Other long-term liabilities                             946            1,130
                                                   --------         --------

     Total liabilities                               27,750           49,301
                                                   --------         --------

Stockholders' equity:
  Common stock,$.01 par value:
    Authorized - 60,000,000 shares
    Issued - 31,706,255 in October, 1998
             and 31,316,099 in January, 1998            317              313
  Additional paid-in capital                         74,396           71,168
  Retained earnings                                 121,346          123,226
  Unrealized gain on investments                          -               12
                                                   --------         --------
                                                    196,059          194,719

  Less:  Deferred compensation                          771            1,133
                                                   --------         --------

     Total stockholders' equity                     195,288          193,586
                                                   --------         --------

Total liabilities and
    stockholders' equity                           $223,038         $242,887
                                                   ========         ========
</TABLE>


    The accompanying notes are an integral part of the financial statements.


                                       -3-


<PAGE>   4


               Unitrode Corporation and Consolidated Subsidiaries
                            Statements of Operations
                                   (Unaudited)
                        (in thousands except share data)

<TABLE>
<CAPTION>

For the Three Months Ended                  October 31, 1998   November 1, 1997
-------------------------------------------------------------------------------
<S>                                           <C>                <C>        
Net revenues                                  $     40,403       $    59,348
Cost of revenues                                    21,373            27,890
                                              ------------       -----------

  Gross profit                                      19,030            31,458
                                              ------------       -----------

Operating expenses:
  Research and development expenses                  5,031             5,491
  Selling, general and administrative
    expenses                                         7,481             9,741
  New fab pre-operating expenses                         -             1,506
  Merger costs                                         354                 -
  Restructuring and other costs                      5,237                 -
                                              ------------       -----------

    Total operating expenses                        18,103            16,738
                                              ------------       -----------

Income from operations                                 927            14,720
                                              ------------       -----------

Other income (expense):
  Royalty income                                       416               716
  Non-operating income (expense), net               (6,645)              112
  Interest income, net                                 928               885
                                              ------------       -----------

    Total other income (expense)                    (5,301)            1,713
                                              ------------       -----------

Income (loss) before income tax
  provision (benefit)                               (4,374)           16,433

Income tax provision (benefit)                      (1,508)            5,935
                                              ------------       -----------

Net income (loss)                             $     (2,866)      $    10,498
                                              ============       ===========



Earnings (loss) per common share:
    Basic                                     $       (.09)      $       .34
                                              ============       ===========
    Diluted                                   $       (.09)      $       .31
                                              ============       ===========

Average common and common equivalent
  shares outstanding:
    Basic                                       31,678,484        30,941,945
                                              ============       ===========
    Diluted                                     31,678,484        33,333,312
                                              ============       ===========
</TABLE>
                                                                             
                                                                             
                                           
    The accompanying notes are an integral part of the financial statements.


                                       -4-


<PAGE>   5


               Unitrode Corporation and Consolidated Subsidiaries
                            Statements of Operations
                                   (Unaudited)
                        (in thousands except share data)

<TABLE>
<CAPTION>


For the Nine Months Ended                  October 31, 1998    November 1, 1997
--------------------------------------------------------------------------------
<S>                                          <C>                 <C>         
Net revenues                                 $    116,232        $    171,535
Cost of revenues                                   64,302              81,074
                                             ------------        ------------

  Gross profit                                     51,930              90,461
                                             ------------        ------------

Operating expenses:
  Research and development expenses                14,252              16,033
  Selling, general and administrative
    expenses                                       23,179              29,196
  New fab pre-operating expenses                    2,075               4,651
  Merger costs                                      2,672                   -
  Restructuring and other costs                     6,504                   -
                                             ------------        ------------

    Total operating expenses                       48,682              49,880
                                             ------------        ------------

Income from operations                              3,248              40,581
                                             ------------        ------------

Other income (expense):
  Royalty income                                    1,416               2,365
  Non-operating expenses, net                      (8,924)               (220)
  Interest income, net                              2,728               2,371
                                             ------------        ------------

    Total other income (expense)                   (4,780)              4,516
                                             ------------        ------------

Income (loss) before income tax provision          (1,532)             45,097

Income tax provision                                  372              16,526
                                             ------------        ------------

Net income (loss)                            $     (1,904)       $     28,571
                                             ============        ============



Earnings (loss) per common share:
    Basic                                    $       (.06)       $        .94
                                             ============        ============
    Diluted                                  $       (.06)       $        .87
                                             ============        ============

Average common and common equivalent
  shares outstanding:
    Basic                                      31,570,572          30,485,006
                                             ============        ============
    Diluted                                    31,570,572          32,658,106
                                             ============        ============
</TABLE>


    The accompanying notes are an integral part of the financial statements.


                                       -5-


<PAGE>   6


               Unitrode Corporation and Consolidated Subsidiaries
                            Statements of Cash Flows
                                   (Unaudited)
                                 (in thousands)

<TABLE>
<CAPTION>


For the Nine Months Ended                                        October 31, 1998  November 1, 1997
---------------------------------------------------------------------------------------------------
<S>                                                                 <C>               <C>     
Cash flows from operating activities:
   Net income (loss)                                                $ (1,904)         $ 28,571
   Adjustments to reconcile net income (loss) to
   net cash provided (used) by operating activities:
     Depreciation and amortization                                    10,937             9,894
     Deferred and other compensation                                   1,181                71
     Writedown of assets                                               6,786             1,105
     Deferred income taxes                                             2,190              (520)
     Other, net                                                         (279)                7
    (Increase) decrease in assets:
       Accounts receivable                                             3,690           (13,155)
       Inventories                                                    (6,614)              310
       Other current and long-term assets                                590              (652)
     Increase (decrease) in liabilities:
       Accounts payable                                               (6,554)            2,538
       Income taxes payable                                           (3,342)            1,701
       Accrued employee compensation and benefits                     (8,846)            7,240
       Accrued distributor liability                                   2,670             1,836
       Deferred income on shipments to distributors                   (1,112)              (61)
       Other current and long-term liabilities                        (2,402)            2,567
                                                                    --------          --------
         Total adjustments                                            (1,105)           12,881
                                                                    --------          --------
     Net cash provided (used) by operating activities                 (3,009)           41,452
                                                                    --------          --------
Cash flows from investing activities:
   Property, plant and equipment and deposits                         (6,268)          (36,497)
   Proceeds on sale of assets                                            149                95
   Repayment of notes receivable                                         666               751
   Payment of note for wafer agreement                                     -            (2,000)
   Restricted cash and investments                                        (2)             (369)
   Maturities of short-term investments                               26,431            46,546
   Purchases of short-term investments                                (8,905)          (46,837)
                                                                    --------          --------
     Net cash provided (used) by investing activities                 12,071           (38,311)
                                                                    --------          --------
Cash flows from financing activities:
   Proceeds from exercise of stock options and warrants                2,123            10,556
   Purchase of common stock                                                -              (274)
   Principal payments under capital lease obligations                   (940)           (1,068)
                                                                    --------          --------
     Net cash provided by financing activities                         1,183             9,214
                                                                    --------          --------

Addition of Benchmarq's net cash activity for January, 1998              402                 -
                                                                    --------          --------

Net increase in cash and cash equivalents                             10,647            12,355
Cash and cash equivalents at beginning of period                      67,956            54,587
                                                                    --------          --------
Cash and cash equivalents at end of period                          $ 78,603          $ 66,942
                                                                    ========          ========
Supplemental information:
   Interest paid                                                    $    115          $    211
   Income taxes paid, net of tax refunds                            $  2,047          $ 15,915
</TABLE>



    The accompanying notes are an integral part of the financial statements.

                                       -6-


<PAGE>   7


               Unitrode Corporation and Consolidated Subsidiaries
                   Notes to Consolidated Financial Statements
                                October 31, 1998
                                   (Unaudited)
                        (in thousands except share data)

NOTE 1 - BASIS OF PRESENTATION

The accompanying unaudited consolidated financial statements include the
accounts of Unitrode Corporation and its wholly owned subsidiaries (see Note 6),
and have been prepared in accordance with generally accepted accounting
principles for interim financial information and pursuant to the rules and
regulations of the Securities and Exchange Commission. Accordingly, they do not
include all of the information and footnotes required by generally accepted
accounting principles for complete financial statements. For further
information, refer to the consolidated financial statements and footnotes
included in the annual reports on Form 10-K of Unitrode Corporation (the
"Company") for the year ended January 31, 1998 and Benchmarq Microelectronics,
Inc. ("Benchmarq") for the year ended December 31, 1997.

In the opinion of management, all adjustments considered necessary for a fair
presentation have been included. Operating results for the nine-month period
ended October 31, 1998 are not necessarily indicative of the results that may be
expected for the year ending January 31, 1999. Certain amounts for fiscal year
1998 have been reclassified to conform with presentation of similar amounts in
fiscal year 1999.

NOTE 2 - NEW ACCOUNTING STANDARDS

Effective February 1, 1998, the Company adopted Statement of Financial
Accounting Standards ("SFAS") No. 130, "Reporting Comprehensive Income." SFAS
No. 130 requires disclosure of comprehensive income in interim periods and
additional disclosures of the components of comprehensive income on an annual
basis. Comprehensive income includes all changes in equity during a period
except those resulting from investments by and distributions to the Company's
shareholders. For the periods ended October 31, 1998 and November 1, 1997,
components of the Company's comprehensive income (loss) are listed below:
<TABLE>
<CAPTION>
                                              Three months ended    Nine months ended 
 -------------------------------------------------------------------------------------
                                                Oct. 31,  Nov. 1,   Oct. 31,   Nov. 1,
                                                 1998      1997       1998      1997  
 -------------------------------------------------------------------------------------
<S>                                            <C>       <C>       <C>        <C>    
 Net income (loss)                             $(2,866)  $10,498   $(1,904)   $28,571
 Unrealized gain (loss) on investments              (2)        2       (12)         2
                                               -------   -------   -------    -------
 Comprehensive income (loss)                   $(2,868)  $10,500   $(1,916)   $28,573
                                               =======   =======   =======    =======
</TABLE>


In June 1997, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards No. 131, "Disclosures about Segments of an
Enterprise and Related Information," which establishes annual and interim
reporting standards for an enterprise's business segments and related
disclosures about its products, services, geographic areas and major customers.
Adoption of this statement will not impact the Company's consolidated financial
position, results of operations or cash flows. The Company will adopt this
statement in its year-end financial statements for fiscal year 1999.


                                       -7-


<PAGE>   8


In June, 1998, the Financial Accounting Standards Board issued Statement of
Financial Accounting Standards No. 133, "Accounting for Derivative Instruments
and Hedging Activities", which requires that all derivative instruments be
recorded on the balance sheet at their fair value. Changes in the fair value of
derivatives are recorded each period in current earnings or other comprehensive
income, depending on whether a derivative is designated as part of a hedge
transaction and, if it is, the type of hedge transaction. Adoption of this
statement will not have a significant effect on the Company's results of
operations or its financial position. The Company will adopt this statement in
its financial statements for fiscal year 2001.

NOTE 3 - EARNINGS PER SHARE

The following tables sets forth the computation of basic and diluted earnings
per share.
<TABLE>
<CAPTION>

Three months ended                                 October 31, 1998     November 1, 1997
----------------------------------------------------------------------------------------
<S>                                                  <C>                  <C>        
Net income (loss)                                    $    (2,866)         $    10,498
                                                     ===========          ===========

Basic weighted average shares outstanding             31,678,484           30,941,945
Effect of dilutive securities-stock options                    -            2,372,598
Effect of dilutive securities-stock warrants                   -               18,769
                                                     -----------          -----------
Diluted weighted average shares outstanding           31,678,484           33,333,312
                                                     ===========          ===========

Basic earnings per share                             $      (.09)         $       .34
                                                     ===========          ===========

Diluted earnings per share                           $      (.09)         $       .31
                                                     ===========          ===========
</TABLE>

<TABLE>
<CAPTION>

Nine months ended                                  October 31, 1998      November 1, 1997
-----------------------------------------------------------------------------------------
<S>                                                  <C>                  <C>        
Net income (loss)                                    $    (1,904)         $    28,571
                                                     ===========          ===========

Basic weighted average shares outstanding             31,570,572           30,485,006
Effect of dilutive securities-stock options                    -            2,061,229
Effect of dilutive securities-stock warrants                   -              111,871
                                                     -----------          -----------
Diluted weighted average shares outstanding           31,570,572           32,658,106
                                                     ===========          ===========

Basic earnings per share                             $      (.06)         $       .94
                                                     ===========          ===========

Diluted earnings per share                           $      (.06)         $       .87
                                                     ===========          ===========
</TABLE>

Options to purchase a total of 638,439 and 884,716 shares of common stock at
prices ranging from $0.28 to $11.59 and $0.28 to $14.38 were outstanding for the
three months and nine months ended October 31, 1998, respectively, but not
included in the computation of diluted earnings per share because the Company
reported a net loss for these periods.

In addition, the following stock options were not included in the computation of
diluted earnings per share because their exercise prices were greater than the
average market price of the common shares as of such date and were, therefore,
anti-dilutive under the Treasury stock method. 

<TABLE>
<CAPTION>

                                             Three months ended                Nine months ended     
                                           ------------------------         -----------------------
                                                           Range of                        Range of
                                                           Exercise                        Exercise
                                           Options         Prices           Options        Prices     
                                           -------         --------         -------        ---------  
      <S>                                <C>            <C>               <C>           <C>        
      October 31, 1998                    3,862,026     $12.25-$40.36     2,116,983     $14.50-$40.36
      November 1, 1997                        3,626     $40.36               16,319     $29.53-$40.36
</TABLE>



                                       -8-


<PAGE>   9


NOTE 4 - NON-OPERATING INCOME (EXPENSE)
<TABLE>
<CAPTION>

           Three months ended                          October 31, 1998     November 1, 1997
           ----------------------------------------------------------------------------------
<S>                                                        <C>                  <C>   
           Foreign exchange losses                         $    (7)             $ (14)
           Gains on sale of fixed assets                        88                  7
           Net rental income                                   115                119
           Legal settlements                                (6,841)                 -
                                                           -------              -----
                     Total                                 $(6,645)             $ 112
                                                           =======              =====
</TABLE>

<TABLE>
<CAPTION>

           Nine months ended                           October 31, 1998     November 1, 1997
           ---------------------------------------------------------------------------------
<S>                                                        <C>                  <C>   
           Foreign exchange losses                         $   (14)             $ (80)
           Gains on sale of fixed assets                        75                  4
           Net rental income                                   356                321
           Legal settlements                                (6,841)                 -
           Writedown of investments                         (2,500)              (465)
                                                           -------              -----
                     Total                                 $(8,924)             $(220)
                                                           =======              =====
</TABLE>

NOTE 5 - SPECIAL CHARGES

FIRST QUARTER OF FISCAL YEAR 1999

During the first quarter of fiscal year 1999, the Company recorded pre-tax
special charges totaling $6.4 million of which $2.6 million was charged to cost
of sales, $1.3 million was charged to restructuring and other costs in operating
expenses, and $2.5 million was charged to other income (expense).

The charge of $2.6 million to cost of sales was for inventory writeoffs and
consisted primarily of a custom product which was manufactured in the first
quarter of fiscal year 1999 for a specific disk drive customer. The product did
not meet the customer's specifications and has been scrapped.

The $1.3 million charged to operating expenses was for actions intended to align
the business with reduced customer demand in fiscal year 1999. These
restructuring charges consisted of $0.8 million used to writedown equipment
associated with the production of 4" bipolar wafers to net realizable value and
$0.5 million for severance costs associated with a reduction in the workforce of
about 5% or 34 employees. The annualized reduction in cost resulting from the
restructuring were anticipated to be approximately $1.8 million.

The $2.5 million charge to other income (expense) was to account for a reduction
in the carrying value of the Company's equity investment in an outside foundry
in which the Company maintained a $2.5 million equity investment and a $1.0
million note receivable. The significant reduction in the Company's business in
the first quarter of fiscal year 1999 and the anticipated ramp-up of the
Company's 6" fab in the second half of the year has substantially reduced future
demand for wafers produced at this foundry. The Company currently is the primary
customer of this foundry. The material reduction in wafer output has negatively
impacted this foundry's financial condition and cash flows. The Company did not
establish a valuation allowance on its $1.0 million note receivable as it
believed that the fair market value of the foundry's tangible assets were
sufficient to recover the value of the note.

THIRD QUARTER OF FISCAL YEAR 1999

During the third quarter of fiscal year 1999, the Company recorded pre-tax
special charges totaling $12.1 million of which $5.2 million was charged to
restructuring and other costs in operating expenses, and $6.9 million was
charged to other income (expense).


                                       -9-


<PAGE>   10


THIRD QUARTER OF FISCAL 1999 (continued)

The $5.2 million charged to operating expenses was primarily for costs related
to the integration of Benchmarq Microelectronics, Inc. ("Benchmarq"). These
costs principally consisted of $1.2 million for equipment writedowns intended to
consolidate back-end operations, $2.8 million in severance costs to reduce
redundant activities, and $1.2 million in other integration costs which includes
costs associated with relocating the Dallas test operations to the Company's
Singapore facility.

The $6.9 million charge to other income (expense) consisted of costs incurred to
settle a patent infringement lawsuit between Dallas Semiconductor Corporation
and Benchmarq as well as a patent infringement lawsuit initiated by the Lemelson
Medical Education & Research Foundation, Limited Partnership against Unitrode.

           SPECIAL CHARGES ROLLFORWARD:
<TABLE>
<CAPTION>
                                                           Balance Sheet                   
                                           --------------------------------------------------------------------------
                                               Valuation Allowances
                               Special         --------------------                   Legal               Other
                               Charges                Fixed                Employee   Costs     Paid-in   Integration
                               Provision   Inventory  Assets  Investmts.   Accruals   Accrual   Capital   Accruals  
      ---------------------------------------------------------------------------------------------------------------
      <S>                      <C>          <C>       <C>       <C>         <C>      <C>         <C>        <C>   
      Q1 FY99 Charge           $ 6,363      $2,596    $  665    $2,500      $  520   $     -     $  -       $   82
      Q3 FY99 Charge            12,078           -     1,177         -       2,009     6,841      819        1,232
      FY99 Payments/Disposals        -      (2,203)     (558)        -        (663)   (6,841)       -         (815)
                               -------      ------    ------    ------      ------   -------      ---       ------
      Q3 FY99 Balance          $18,441      $  393    $1,284    $2,500      $1,866   $     -     $819       $  499
                               =======      ======    ======    ======      ======   =======     ====       ======
</TABLE>


NOTE 6 - BENCHMARQ MERGER

On August 3, 1998, the Company completed its acquisition of Benchmarq, a Dallas,
Texas provider of integrated circuits and electronics modules for portable and
power-sensitive electronics systems. In connection with the transaction, the
Company issued approximately 7.2 million shares of its common stock. The merger
was accounted for on a pooling-of-interests basis. Accordingly, the Company's
consolidated financial statements have been restated to include the accounts and
operations of Benchmarq for all periods presented. The Company recorded combined
merger-related transaction costs of $2.7 million primarily for professional
services, such as investment banking, legal, and accounting.

Due to the different fiscal year-ends of the Company and Benchmarq, prior year
financial information for different fiscal periods has been combined. The
audited balance sheet as of January 31, 1998 combines the Company's January 31,
1998 financial position with Benchmarq's December 31, 1997 financial position.
The Company's statements of operations and cash flows for its fiscal year ended
January 31, 1998 are combined with Benchmarq's statements of operations and cash
flows for the fiscal year ended December 31, 1997. Accordingly, the statements
of operations combine the Company's operating results for the three and nine
months ended November 1, 1997 with the corresponding Benchmarq operating results
for the three and nine months ended September 30, 1997. The statement of cash
flows combines the Company's cash flows for the nine months ended November 1,
1997 with the corresponding Benchmarq cash flows for the nine months ended
September 30, 1997. Benchmarq's net income for the one month period ended
January 31, 1998 was $24,000 and was excluded from the Company's combined fiscal
year 1999 operating results. Benchmarq's net cash flows for the one month period
ended January 31, 1998 were $402,000 and have been added as a separate line in
the Company's combined fiscal year 1999 statement of cash flows.

Certain financial statement balances of Benchmarq have been reclassified to
conform with the Company's financial statement presentation. Certain adjustments
have also been made to conform Benchmarq accounting policies to those followed
by Unitrode. Effective in the Company's fiscal third quarter ended October 31,
1998, Benchmarq's revenue recognition policy for distributor sales was changed
from deferral until products were sold by distributors to the Company's policy
of recognizing revenue at the time of shipment as a result of the consolidation 
of the Company's distributors.


                                      -10-


<PAGE>   11


NOTE 6 - BENCHMARQ MERGER (CONTINUED)

Revenues and net income of the combined entities for the six-month period prior
to the merger are presented in the following table. Prior to the merger, there
were no intercompany transactions between the two companies and certain
Benchmarq amounts in the financial statements were reclassified to conform to
Unitrode's presentations. Merger-related transaction costs of $2.3 million
recorded in the historical net income for the first six months have been
excluded from the unaudited proforma results.

                                                          Six months ended
          Proforma Results                                 August 1, 1998  
          ----------------                                 --------------  

           Net Revenues:
           -------------
             Unitrode                                         $57,724
             Benchmarq                                         18,105
                                                              -------
             Combined                                         $75,829
                                                              =======

           Net Income:
           -----------
             Unitrode                                         $1,998
             Benchmarq                                         1,282
                                                              ------
             Combined                                         $3,280
                                                              ======


The following table represents a reconciliation of net revenues and net income
previously reported by the combining companies to those presented in the
accompanying consolidated financial statements.
<TABLE>
<CAPTION>
                                                        Three months ended         Nine months ended
                                                        November 1, 1997           November 1, 1997
                                                        ------------------         -----------------
<S>                                                           <C>                       <C>     
      Net Revenues:
      -------------
        Unitrode                                              $48,538                   $137,556
        Benchmarq                                              10,810                     33,979
                                                              -------                   --------
        Combined                                              $59,348                   $171,535
                                                              =======                   ========

      Net Income:
      -----------
        Unitrode                                              $ 8,850                   $ 23,554
        Benchmarq                                               1,648                      5,017
                                                              -------                   --------
        Combined                                              $10,498                   $ 28,571
                                                              =======                   ========
</TABLE>


                                      -11-


<PAGE>   12


Item 2. Management's Discussion and Analysis of Financial Condition and Results
        of Operations

RESULTS OF OPERATIONS

The following table sets forth, for the fiscal periods indicated, the percentage
of net revenues represented by certain items in Unitrode's statements of
operations:
<TABLE>
<CAPTION>
                                          Three months ended             Nine months ended     
------------------------------------------------------------------------------------------------
                                    Oct. 31,  Oct. 31,    Nov. 1,  Oct. 31,  Oct. 31,    Nov. 1,
                                      1998     1998        1997      1998      1998       1997  
------------------------------------------------------------------------------------------------
                                    Proforma*                      Proforma*
<S>                                  <C>       <C>        <C>       <C>       <C>        <C>   
Net revenues                         100.0%    100.0%     100.0%    100.0%    100.0%     100.0%
Cost of revenues                      52.9      52.9       47.0      53.1      55.3       47.3
                                     -----     -----      -----     -----     -----      -----
     Gross profit                     47.1      47.1       53.0      46.9      44.7       52.7
                                     -----     -----      -----     -----     -----      -----
Operating expenses:
  Research & development expenses     12.5      12.5        9.3      12.3      12.3        9.3
  Selling, general and
     administrative expenses          18.5      18.5       16.4      19.9      19.9       17.0
  New fab pre-operating expenses         -         -        2.5       1.8       1.8        2.7
  Merger, restructuring and
       and other costs                   -      13.8          -         -       7.9          -
                                     -----     -----      -----     -----     -----      -----
     Total operating expenses         31.0      44.8       28.2      34.0      41.9       29.0
                                     -----     -----      -----     -----     -----      -----

Income from operations                16.1       2.3       24.8      12.9       2.8       23.7
Other income (expense)                 3.8     (13.1)       2.9       3.9      (4.1)       2.6
                                     -----     -----      -----     -----     -----      -----
Income (loss) before income tax
  provision (benefit)                 19.9     (10.8)      27.7      16.8      (1.3)      26.3
Net income (loss)                     12.5%     (7.1)%     17.7%     10.6%     (1.6)%     16.7%
</TABLE>

*  Excluding special charges and merger costs  

Three Months Ended October 31, 1998 versus Three Months Ended November 1, 1997

Net sales for the Company's third quarter ended October 31, 1998 were $40.4
million compared with $59.3 million in the previous year's third quarter, a
decrease of $18.9 million, or 32%. The decline was principally due to a
reduction of approximately $10.1 million in a discontinued custom circuit for a
specific disk drive customer, as well as weakness in the EDP market and
depletion of excess customer inventories. Approximately 61% of sales in the
third quarter were international compared with 68% in the prior year.

Gross profit as a percentage of net sales was 47.1% in the third quarter of
fiscal year 1999 compared to 53.0% in the same quarter of the prior year. The
decrease in the gross profit percentage was primarily due to lower sales volume
which reduced utilization of manufacturing capacity and costs associated with
the initial ramp up of production in the Company's new 6" BiCMOS wafer
fabrication facility.

Weakness, primarily in the EDP market, has affected and may continue to affect
the Company's bookings. As a result of greater manufacturing capacity available
at the Company and in the semiconductor industry as a whole, lead times for
delivery have decreased considerably compared to the prior year. Turns business
(orders booked and shipped in the same quarter) was approximately 30% of sales
in the third quarter of fiscal year 1999 and has increased compared to the prior
two quarters. Customers continue to provide limited visibility as to future
demand and the Company will continue to be dependent upon increased turns
business to maintain the present revenue level.


                                      -12-


<PAGE>   13


RESULTS OF OPERATIONS (continued)

Research and development expenses were approximately 12.5% of net sales, or $5.0
million, compared with 9.3%, or $5.5 million, in the prior year. The percentage
increase was due to the decreased sales volume partially offset by lower
accruals for incentive compensation. Selling, general and administrative
expenses were 18.5% of net sales, or $7.5 million, compared with 16.4%, or $9.7
million, in the previous year's third quarter. The decrease of $2.2 million was
primarily due to reductions in accruals for incentive compensation and sales
commissions.

During the third quarter of fiscal year 1999, the Company recorded merger costs
of $0.4 million, primarily for professional fees, associated with the
acquisition of BENCHMARQ Microelectronics, Inc. ("Benchmarq"). See Note 6 in the
Company's consolidated financial statements for further information.

In the third quarter of fiscal year 1999, the Company recorded special charges
totaling $12.1 million of which $5.2 million was charged to restructuring and
other costs in operating expenses, and $6.9 million was charged to other income
(expense). See Note 5 in the Company's consolidated financial statements for
further information.

The consolidated effective rate of tax benefit for the quarter ended October 31,
1998 was 34.5% compared with an effective tax provision rate of 36.1% for the
quarter ended November 1, 1997. Excluding non-deductible merger costs, the
effective rate of tax benefit was 37.5% in the third quarter of fiscal year
1999.

Net loss for the third quarter of fiscal year 1999 was $(2.9) million, or $(.09)
per diluted share, compared with net income of $10.5 million, or $.31 per
diluted share for the comparable period of the prior year. Excluding special
charges and merger costs, net income would have been $5.0 million, or $.16 per
diluted share, for the third quarter of fiscal year 1999.

Nine Months Ended October 31, 1998 versus Nine Months Ended November 1, 1997

Net sales for the nine months ended October 31, 1998 were $116.2 million
compared with $171.5 million in the previous year's nine-month period, a
decrease of $55.3 million, or 32%. The decline was principally due to a
reduction of approximately $29.9 million in a discontinued custom circuit for a
specific disk drive customer, as well as weakness in the EDP market and
depletion of excess customer inventories. Approximately 62% of sales for the
first nine months were international compared with 66% in the prior year.

Gross profit as a percentage of net sales was 44.7% compared to 52.7% in the
prior year. Excluding the special charge of $2.6 million recorded in the first
quarter to account for inventory writeoffs, gross profit as a percentage of net
sales was 46.9%. The decrease in the gross profit percentage compared to the
prior year, excluding the special charge, was primarily due to lower sales
volume which reduced utilization of manufacturing capacity and costs associated
with the initial ramp up of production in the Company's new 6" BiCMOS wafer
fabrication facility.

Research and development expenses were approximately 12.3% of net sales, or
$14.3 million, compared with 9.3%, or $16.0 million, in the prior year. The
percentage increase was due to the decreased sales volume partially offset by
lower accruals for incentive compensation. Selling, general and administrative
expenses were 19.9% of net sales, or $23.2 million, compared with 17.0%, or
$29.2 million, in the previous year. The decrease of $6.0 million was primarily
due to reductions in accruals for incentive compensation and sales commissions.

The Company's new 6" BiCMOS wafer fabrication facility in Merrimack, New
Hampshire became operational at the end of the second quarter of fiscal year
1999. Pre-operating costs for fiscal year 1999 and for the life of the project
were $2.1 million and $8.4 million, respectively. Pre-operating costs, which
were incurred prior to the commencement of production, related primarily to the
qualification of equipment and manufacturing processes to meet design, test and
reliability specifications as well as to recruit and train personnel.


                                      -13-


<PAGE>   14


RESULTS OF OPERATIONS (continued)

During the first nine months of fiscal year 1999, the Company recorded special
charges totaling $18.5 million of which $2.6 million was charged to cost of
sales, $6.5 million was charged to restructuring and other costs in operating
expenses, and $9.4 million was charged to other income (expense). See Note 5 in
the Company's consolidated financial statements for further information. The
Company also recorded merger-related transaction costs of $2.7 million in fiscal
year 1999 as a result of the Benchmarq acquisition. See Note 6 in the Company's
consolidated financial statements for further information.

The consolidated effective tax rate for the nine months ended October 31, 1998
was 24.3% compared with 36.6% for the nine months ended November 1, 1997.
Excluding non-deductible merger costs, the effective tax rate was 32.6% in the
first nine months of fiscal year 1999.

Net loss for the nine months ended October 31, 1998 was $(1.9) million, or
$(.06) per diluted share, compared with net income of $28.6 million, or $.87 per
diluted share, for the comparable period of the prior year. Excluding special
charges and merger costs, net income would have been $12.3 million, or $.38 per
diluted share, for the nine months ended October 31, 1998.

FINANCIAL CONDITION

Cash and short-term investments at October 31, 1998 decreased by $6.4 million to
$78.6 million since the beginning of fiscal year 1999. The principal uses of
cash were $3.0 million for operating activities and $6.3 million in capital
expenditures offset by $2.1 million in proceeds from exercises of employee stock
options. It is anticipated that the Company's operating cash needs for fiscal
year 1999, including planned capital expenditures, will be met by internally
generated funds and available cash.

Capital expenditures were $6.3 million for the first nine months of fiscal year
1999. In fiscal year 1999, the Company expects capital expenditures to total
approximately $11 million for the support of ongoing operations.

The ratio of current assets to current liabilities was 5.47:1 at October 31,
1998 compared with 3.22:1 at January 31, 1998. Working capital of $110.9 million
at October 31, 1998 increased by $10.5 million from January 31, 1998. Accounts
receivable at October 31, 1998 decreased by $5.1 million from January 31, 1998
primarily due to reduced sales. Receivable day sales outstanding ("DSO") were 51
days at October 31, 1998 compared to 47 days at January 31, 1998. Inventories at
October 31, 1998 increased by $4.7 million since January 31, 1998 primarily to
support the anticipated increase in turns business. Income taxes payable at
October 31, 1998 decreased by a total of $3.3 million from January 31, 1998,
primarily due to tax benefits resulting from the special charges. Accrued
employee compensation and benefits were $8.9 million lower than at year-end due
to the payment of incentive compensation related to the Company's performance in
fiscal year 1998. Accrued distributor liability increased by $2.7 million since
January 31, 1998 principally due to additional estimated inventory returns
associated with consolidating the Company's distributors with Benchmarq.


                                      -14-


<PAGE>   15


NEW ACCOUNTING STANDARDS

See Note 2 in the Company's consolidated financial statements for a discussion
of recently issued accounting standards.

BENCHMARQ MERGER

On August 3, 1998, the Company completed its acquisition of Benchmarq, a Dallas,
Texas provider of integrated circuits and electronics modules for portable and
power-sensitive electronics systems. In connection with the transaction, the
Company issued approximately 7.2 million shares of its common stock. The merger
was accounted for on a pooling-of-interests basis. Accordingly, the Company's
consolidated financial statements have been restated to include the accounts and
operations of Benchmarq for all periods presented.

YEAR 2000 IMPACT

The Company, including the Benchmarq operations, has completed an assessment of
all computer-based software and hardware to ensure Year 2000 compliance. Certain
non-Year 2000 compliant systems and equipment are being modified, scrapped, or
replaced. In addition, the Company has begun replacement of certain business
systems with a Year 2000 compliant enterprise resource planning system ("ERP
system") in order to improve reporting and productivity. Formal communications
have been established with all significant vendors to determine the extent to
which the Company could be impacted by third parties' failure to remediate their
own Year 2000 issues. The Company is currently unaware of any Year 2000 issues
at the Company or a third party that will not be compliant in a timely manner
and could result in a material effect on the Company's business, results of
operations, or financial condition. Year 2000 project expenditures, excluding
capitalized costs associated with the ERP system, have been immaterial to date
and are not anticipated to exceed $1.0 million. The Year 2000 project is
expected to be substantially completed by June, 1999.

FACTORS AFFECTING FUTURE RESULTS

The Company's future operating results are difficult to predict and may be
affected by a number of factors including the timely ability to develop and
market new products, competitive pricing pressures, fluctuations in
manufacturing yields, adequate availability of processed silicon wafers from
foundry sources, insufficient or excess manufacturing and testing capacity, the
timely ability to integrate Benchmarq's operations into the Company, changes in
product mix, and fluctuating economic conditions in the United States, Asia and
other international markets.

Sales to one customer, IBM Corporation, represented approximately 10% and 11% of
sales in the third quarter of fiscal years 1999 and 1998, respectively, and 11%
and 9% of sales in the first nine months of fiscal years 1999 and 1998,
respectively. The loss or a substantial reduction in sales from this customer
would have a material adverse effect upon the Company's business. Sales to
Western Digital Corporation represented approximately 18% of sales for the third
quarter and the first nine months of the prior fiscal year, but were
significantly less than 10% in comparable periods in the current fiscal year.


                                      -15-


<PAGE>   16


FACTORS AFFECTING FUTURE RESULTS (continued)

The semiconductor market historically has been cyclical and subject to
significant economic fluctuations at various times. As a result, orders and
backlog may fluctuate widely from time to time. Weakness, primarily in the EDP
market, has affected and may continue to affect the Company's bookings and the
scheduling of existing backlog. Because of this and other factors, there can be
no assurance that the Company will not experience material fluctuations in
future operating results on a quarterly or annual basis as a result of its
inability to adjust its manufacturing capacity or its cost structure to
increased or reduced customer demand.

Presently, the Company is dependent upon GMT Microelectronics Corporation
("GMT"), an outside foundry, as a significant source of BiCMOS wafers for
certain products. The dependence on GMT is expected to continue until the
Company completes full qualification of manufacturing processes and products at
its 6" wafer fabrication facility and ramps up production. There can be no
assurance that GMT or other third-party foundries will be able to meet the
Company's future BiCMOS wafer production requirements.

After the August 3, 1998 merger with Benchmarq, the Company continued to be
dependent on Taiwan Semiconductor Manufacturing Company ("TSMC") for CMOS wafer
capacity. In May 1996, Benchmarq entered into an Option Agreement with TSMC
which committed the Company to purchase and TSMC to provide specified quantities
of wafers at prevailing market prices through the calendar year 2000.
Additionally, the Company has an option to purchase and TSMC has committed to
provide certain additional wafers through the calendar year 2000. The loss of
the TSMC Option Agreement, the failure of TSMC to honor the TSMC Option
Agreement or the failure to utilize option wafers as specified under the terms
of the TSMC Option Agreement could have a material adverse effect on the
Company.

The Company's new 6" BiCMOS wafer fabrication facility became operational at the
end of the second quarter ended August 1, 1998. Full qualification of
manufacturing processes and products is continuing. There can be no assurance
that certain processes and products will be qualified on time, that the added
capacity will match demand for its products, or that the initial ramp up of
production will result in acceptable manufacturing yields. The Company's
additional capacity has resulted in a significant increase in operating
expenses, such as depreciation, and if revenues do not increase to offset these
additional expenses, the Company's future gross profit percent of sales would be
adversely affected. Meanwhile, other semiconductor manufacturers are also
expanding or planning to expand their production capacity over the next several
years. There can be no assurance that the expansion by the Company and its
competitors will not lead to further over-capacity in the industry, which could
lead to price erosion that could adversely affect the Company's operating
results.

The integration of the Company's operations following the merger with Benchmarq
will require the dedication of management resources that may temporarily divert
attention from the day-to-day business of the combined Company and this
distraction could have an adverse effect on the near-term revenues and operating
results of the combined Company. Also, there can be no assurance that the
combined Company will be able to retain its key technical and management
personnel or that the combined Company will realize all or any of the
anticipated benefits of the merger.


                                      -16-


<PAGE>   17


FORWARD-LOOKING INFORMATION

The Private Securities Litigation Reform Act of 1995 ("the Act") provides a new
"safe harbor" for forward-looking statements so long as those statements are
identified as forward-looking and are accompanied by meaningful cautionary
statements identifying important factors that could cause actual results to
differ materially from those discussed in the statement. The Company desires to
take advantage of the new "safe harbor" provisions of the Act. Certain
information contained herein, particularly the information appearing under the
headings "Results of Operations," "Financial Condition," "Benchmarq Merger,"
"Year 2000 Impact," and "Factors Affecting Future Results" is forward-looking.

Information regarding certain important factors that could cause actual results
of operations or outcomes of other events to differ materially from any such
forward-looking statement appears together with such statement, and/or elsewhere
herein. This information should be read in conjunction with the Company's annual
report on Form 10-K for the year ended January 31, 1998 and Benchmarq's annual
report on Form 10-K for the year ended December 31, 1997.


                                      -17-


<PAGE>   18


                           PART II. OTHER INFORMATION
               Unitrode Corporation and Consolidated Subsidiaries
                                October 31, 1998


ITEM 1.  LEGAL PROCEEDINGS

On July 31, 1998, the Company, along with twenty-five other companies, was named
as a defendant in a lawsuit filed in U.S. District Court for the District of
Arizona by the Lemelson Medical Education & Research Foundation, Limited
Partnership ("Lemelson"). The suit alleged that certain manufacturing operations
of the Company, as well as certain manufacturing operations of the other
defendants, infringe sixteen Lemelson patents. The complaint sought an
injunction against infringement of the patents, damages in an unspecified amount
and attorneys' fees. The Company has entered into a license agreement with the
plaintiff in settlement of the matter and the lawsuit has been dismissed against
the Company.

ITEM 2.  CHANGES IN THE RIGHTS OF THE COMPANY'S SECURITY HOLDERS

None.

ITEM 3.  DEFAULTS UPON SENIOR SECURITIES

Not Applicable.

ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

None.


                                      -18-


<PAGE>   19



ITEM 5.  OTHER INFORMATION
None.

ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K

           (a)       Exhibits

                     Exhibit 27 - Financial Data Schedules

           (b)       REPORTS ON FORM 8-K: On August 4, 1998, the Registrant
                     filed a report on Form 8-K announcing that it had acquired
                     BENCHMARQ Microelectronics, Inc. pursuant to the terms of
                     the previously reported Agreement and Plan of Merger, dated
                     as of March 2, 1998, and the amendment thereto, dated as of
                     June 23, 1998.

                     On October 7, 1998, the Registrant filed a report on Form
                     8-K which included the financial statements of the acquired
                     business, Benchmarq Microelectronics, Inc., ("Benchmarq")
                     as well as unaudited proforma condensed financial
                     statements showing the business combination between
                     Unitrode Corporation and Benchmarq accounted for on a
                     "pooling-of-interests" basis.


                                      -19-


<PAGE>   20


               Unitrode Corporation and Consolidated Subsidiaries
                                October 31, 1998

                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

                                          UNITRODE CORPORATION


   December 15, 1998                      /s/ Robert J. Richardson
   -----------------                      --------------------------------------
   Date                                   Robert J. Richardson
                                          Chairman and Chief Executive Officer


   December 15, 1998                      /s/ Cosmo S. Trapani
   -----------------                      --------------------------------------
   Date                                   Cosmo S. Trapani
                                          Executive Vice President and
                                          Chief Financial Officer
                                          (Principal Financial and Accounting
                                          Officer)


                                      -20-