<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 August 1, 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 24,475,157 shares of common stock outstanding as of August 1, 1998.




                                       -1-

<PAGE>   2
                          PART I. FINANCIAL INFORMATION

Item 1. Financial Statements

               Unitrode Corporation and Consolidated Subsidiaries
                                 Balance Sheets
                                 (in thousands)

<TABLE>
<CAPTION>
                                               August 1, 1998  January 31, 1998
Assets                                          (Unaudited)
--------------------------------------------------------------------------------
<S>                                               <C>             <C>

Current assets:

  Cash and cash equivalents                       $ 63,623        $ 65,074
  Accounts receivable, net of allowance
     of $366 in August, 1998
     and $460 in January, 1998                      17,290          24,507
  Notes receivable                                     720             709
  Inventories:
     Raw materials                                     986           1,276
     Work in process                                10,015           8,774
     Finished goods                                  2,734           2,992
                                                  --------        --------
       Total inventories                            13,735          13,042
                                                  --------        --------

  Deferred income taxes                              5,563           7,886
  Prepaid expenses and other
    current assets                                   2,426           2,373
                                                  --------        --------

     Total current assets                          103,357         113,591
                                                  --------        --------

Property, plant and equipment, at cost             140,237         140,568
  Less accumulated depreciation                     65,109          62,403
                                                  --------        --------
    Property, plant and equipment, net              75,128          78,165
                                                  --------        --------

Notes and other receivables, net of discount         2,437           2,828
Deferred income taxes                                    -             324
Restricted cash and investments                      1,115           1,180
Excess of cost over net assets acquired,
   net of accumulated amortization of
   $2,536 in August, 1998 and
   $2,394 in January, 1998                           1,554           1,696
Other assets and deferred charges                    1,591           4,255
                                                  --------        --------

Total assets                                      $185,182        $202,039
                                                  ========        ========
</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>
                                               August 1, 1998   January 31, 1998
Liabilities and Stockholders' Equity            (Unaudited)
--------------------------------------------------------------------------------
<S>                                            <C>              <C>

Current liabilities:
  Accounts payable                                $  8,933          $ 14,231
  Income taxes payable                               1,434             3,944
  Accrued employee compensation and benefits         1,835            10,916
  Accrued distributor liability                      3,578             3,291
  Other current liabilities                          4,375             7,373
                                                  --------          --------

     Total current liabilities                      20,155            39,755
                                                  --------          --------

Deferred income taxes                                2,223             1,791
Other long-term liabilities                            941             1,131
                                                  --------          --------

     Total liabilities                              23,319            42,677
                                                  --------          --------

Stockholders' equity:
  Common stock,$.01 par value:
    Authorized - 60,000,000 shares
    Issued - 24,475,157 in August, 1998
             and 24,310,682 in January, 1998           245               243
  Additional paid-in capital                        46,721            45,089
  Retained earnings                                115,776           115,163
                                                  --------          --------
                                                   162,742           160,495

  Less:  Deferred compensation                         879             1,133
                                                  --------          --------

     Total stockholders' equity                    161,863           159,362
                                                  --------          --------

Total liabilities and
    stockholders' equity                          $185,182          $202,039
                                                  ========          ========
</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                       August 1, 1998   August 2, 1997
--------------------------------------------------------------------------------
<S>                                              <C>              <C>

Net revenues                                         $29,705         $48,178
Cost of revenues                                      15,839          22,624
                                                     -------         -------

  Gross profit                                        13,866          25,554
                                                     -------         -------

Operating expenses:
  Research and development expenses                    3,424           4,409
  Selling, general and administrative expenses         5,191           7,863
  New fab pre-operating expenses                         966           1,631
  Merger costs                                           619               -
                                                     -------         -------

    Total operating expenses                          10,200          13,903
                                                     -------         -------

Income from operations                                 3,666          11,651
                                                     -------         -------

Other income (expense):
  Royalty income                                         442           1,047
  Non-operating income (expense), net                    355            (472)
  Interest income, net                                   666             655
                                                     -------         -------

    Total other income (expense)                       1,463           1,230
                                                     -------         -------

Income before income tax provision                     5,129          12,881

Income tax provision                                   2,167           4,763
                                                     -------         -------

Net income                                           $ 2,962         $ 8,118
                                                     =======         =======


Earnings per common share:
    Basic                                            $   .12         $   .35
                                                     =======         =======
    Diluted                                          $   .12         $   .33
                                                     =======         =======

Average common and common equivalent
  shares outstanding:
    Basic                                         24,445,782      23,526,894
                                                  ==========      ==========
    Diluted                                       24,778,883      24,912,691
                                                  ==========      ==========

</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 six months ended                         August 1, 1998   August 2, 1997
--------------------------------------------------------------------------------
<S>                                              <C>              <C>

Net revenues                                         $57,724         $89,018
Cost of revenues                                      33,422          41,770
                                                     -------         -------

  Gross profit                                        24,302          47,248
                                                     -------         -------

Operating expenses:
  Research and development expenses                    7,217           8,731
  Selling, general and administrative expenses        10,754          14,590
  New fab pre-operating expenses                       2,075           3,145
  Merger costs                                         1,385               -
  Restructuring costs                                  1,267               -
                                                     -------         -------

    Total operating expenses                          22,698          26,466
                                                     -------         -------

Income from operations                                 1,604          20,782
                                                     -------         -------

Other income (expense):
  Royalty income                                       1,000           1,650
  Non-operating expense, net                          (2,277)           (297)
  Interest income, net                                 1,495           1,266
                                                     -------         -------

    Total other income (expense)                         218           2,619
                                                     -------         -------

Income before income tax provision                     1,822          23,401

Income tax provision                                   1,209           8,697
                                                     -------         -------

Net income                                           $   613         $14,704
                                                     =======         =======


Earnings per common share:
    Basic                                            $   .03         $   .63
                                                     =======         =======
    Diluted                                          $   .02         $   .60
                                                     =======         =======

Average common and common equivalent
   shares outstanding:
    Basic                                         24,390,945      23,441,817
                                                  ==========      ==========
    Diluted                                       24,896,754      24,648,827
                                                  ==========      ==========

</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 six months ended                               August 1, 1998   August 2, 1997
--------------------------------------------------------------------------------------
<S>                                                   <C>               <C>

Cash flows from operating activities:
   Net income                                              $   613         $ 14,704
   Adjustments to reconcile net income to
     net cash provided (used) by operating activities:
     Depreciation and amortization                           5,759            5,545
     Deferred compensation                                     254               47
     Writedown of assets                                     5,615            1,105
     Deferred income taxes                                   3,079             (535)
     Other, net                                                  5              (87)
    (Increase) decrease in assets:
       Accounts receivable                                   7,217          (11,792)
       Inventories                                          (3,143)            (227)
       Other current and long-term assets                      (94)             197
     Increase (decrease) in liabilities:
       Accounts payable                                     (5,298)           2,156
       Income taxes payable                                 (2,510)             730
       Accrued employee compensation and benefits           (9,081)           4,505
       Accrued distributor liability                           287              247
       Other current and long-term liabilities              (3,188)           2,114
                                                           -------         --------
         Total adjustments                                  (1,098)           4,005
                                                           -------         --------
     Net cash provided (used) by operating activities         (485)          18,709
                                                           -------         --------

Cash flows from investing activities:
   Property, plant and equipment and deposits               (3,150)         (26,331)
   Proceeds on sale of assets                                   87               94
   Repayment of notes receivable                               391              578
   Restricted cash and investments                              72             (160)
                                                           -------         --------
     Net cash used by investing activities                  (2,600)         (25,819)
                                                           -------         --------
Cash flows from financing activities:
   Proceeds from exercise of stock options and warrants      1,634            2,256
   Purchase of common stock                                      -             (239)
                                                           -------         --------
     Net cash provided by financing activities               1,634            2,017
                                                           -------         --------

Net decrease in cash and cash equivalents                   (1,451)          (5,093)
Cash and cash equivalents at beginning of period            65,074           52,012
                                                           -------         --------
Cash and cash equivalents at end of period                 $63,623         $ 46,919
                                                           =======         ========

Supplemental information:
   Interest paid                                           $    30         $     71
   Income taxes paid, net of tax refunds                   $   644         $  8,502

</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
                                 August 1, 1998
                                   (Unaudited)
                        (in thousands except share data)


NOTE 1 - BASIS OF PRESENTATION

The accompanying unaudited consolidated financial statements 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 report on
Form 10-K of Unitrode Corporation (the "Company") for the year ended January 31,
1998.

In the opinion of management, all adjustments considered necessary for a fair
presentation have been included. Operating results for the six-month period
ended August 1, 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 August 1, 1998 and August 2, 1997, there
were no differences between the Company's comprehensive income and net income.

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.

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                              August 1, 1998    August 2, 1997
--------------------------------------------------------------------------------
<S>                                             <C>               <C>

  Net income                                      $     2,962       $     8,118
                                                  ===========       ===========

  Basic weighted average shares outstanding        24,445,782        23,526,894
  Effect of dilutive securities-stock options         333,101         1,173,313
  Effect of dilutive securities-stock warrants              -           212,484
                                                  -----------       -----------
  Diluted weighted average shares outstanding      24,778,883        24,912,691
                                                  ===========       ===========

  Basic earnings per share                        $       .12       $       .35
                                                  ===========       ===========

  Diluted earnings per share                      $       .12       $       .33
                                                  ===========       ===========
</TABLE>



                                       -7-


<PAGE>   8
NOTE 3 - EARNINGS PER SHARE (continued)

<TABLE>
<CAPTION>

Six months ended                                August 1, 1998    August 2, 1997
--------------------------------------------------------------------------------
<S>                                             <C>               <C>

  Net income                                      $       613       $    14,704
                                                  ===========       ===========

  Basic weighted average shares outstanding        24,390,945        23,441,817
  Effect of dilutive securities-stock options         505,809         1,048,589
  Effect of dilutive securities-stock warrants              -           158,421
                                                  -----------       -----------
  Diluted weighted average shares outstanding      24,896,754        24,648,827
                                                  ===========       ===========

  Basic earnings per share                        $       .03       $       .63
                                                  ===========       ===========

  Diluted earnings per share                      $       .02       $       .60
                                                  ===========       ===========
</TABLE>

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             Six months ended
                        --------------------------    --------------------------
                                        Range of                      Range of
                                        Exercise                      Exercise
                         Options         Prices        Options         Prices
                        ---------    -------------    ---------    -------------
<S>                     <C>          <C>              <C>          <C>

  August 1, 1998        1,781,650    $13.50-$40.36    1,082,000    $16.03-$40.36
  August 2, 1997            -              -            501,800    $24.06
</TABLE>



NOTE 4 - NON-OPERATING INCOME (EXPENSE)

<TABLE>
<CAPTION>

Three months ended                              August 1, 1998    August 2, 1997
--------------------------------------------------------------------------------
<S>                                             <C>               <C>

  Foreign exchange gains (losses)                    $ 236             $ (96)
  Gains (losses) on sale of fixed assets                (2)                1
  Net rental income                                    121                88
  Writedown of investments                               -              (465)
                                                     -----             -----
            Total                                    $ 355             $(472)
                                                     =====             =====
</TABLE>


<TABLE>
<CAPTION>

Six months ended                                August 1, 1998    August 2, 1997
--------------------------------------------------------------------------------
<S>                                             <C>               <C>

  Foreign exchange losses                           $    (8)           $ (66)
  Gains (losses) on sale of fixed assets                (11)              34
  Net rental income                                     242              200
  Writedown of investments                           (2,500)            (465)
                                                    -------            -----
            Total                                   $(2,277)           $(297)
                                                    =======            =====
</TABLE>

NOTE 5 - SPECIAL CHARGES

During the first half of fiscal year 1999, the Company recorded pre-tax special
charges totaling $7.8 million of which $2.6 million was charged to cost of
sales, $2.7 million was charged to restructuring and merger 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.

                                       -8-
<PAGE>   9
NOTE 5 - SPECIAL CHARGES (continued)

The $2.7 million charged to operating expenses consisted of $1.3 million for
actions intended to align the business with reduced customer demand in fiscal
year 1999 and $1.4 million for professional services incurred to date in
connection with the merger of BENCHMARQ Microelectronics, Inc. ("Benchmarq").
Restructuring charges of $1.3 million 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 is 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 production ramp up of
the Company's 6" fab in the second half of the year has substantially reduced
demand for wafers produced at this foundry. The Company currently is the primary
customer of this foundry. The material reduction in wafer output will negatively
impact this foundry's financial condition and estimated future cash flows. The
Company did not establish a valuation allowance on its $1.0 million note
receivable as it believes that the fair market value of the foundry's tangible
assets are sufficient to recover the value of the asset.

NOTE 6 - SUBSEQUENT EVENTS

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
is being accounted for on a pooling-of-interests basis. The Company expects to
record total merger-related costs, on a combined basis, of approximately $2.7
million primarily for professional services, such as investment banking, legal,
and accounting.

There were no transactions between Benchmarq and Unitrode prior to the
combination and certain items in the financial statements were reclassified to
conform to Unitrode's presentation. Prior to the merger, Benchmarq's fiscal year
ended on December 31. The unaudited proforma results for the separate companies
and combined company are presented in the table below. This table represents
Unitrode's and Benchmarq's results for the three months and six months ended
August 1, 1998, and Unitrode's results for the three months and six months ended
August 2, 1997 combined with Benchmarq's three months and six months ended June
30, 1997. Merger-related costs incurred to date and recorded in the historical
net income for Unitrode and Benchmarq were $2.3 million and have been excluded
from the unaudited proforma results.

<TABLE>
<CAPTION>
                                       Three months ended     Six months ended
      --------------------------------------------------------------------------
                                      August 1,  August 2,  August 1,  August 2,
      Proforma Results                   1998       1997       1998       1997
      --------------------------------------------------------------------------
<S>                                    <C>        <C>        <C>        <C>
      Net sales:
        Unitrode                       $29,705    $48,178    $57,724    $ 89,018
        Benchmarq                        9,196     11,458     18,105      23,169
                                       -------    -------    -------    --------
        Combined                       $38,901    $59,636    $75,829    $112,187
                                       =======    =======    =======    ========
      Net income:
        Unitrode                       $ 3,581    $ 8,118    $ 1,998    $ 14,704
        Benchmarq                          847      1,725      1,282       3,368
                                       -------    -------    -------    --------
        Combined                       $ 4,428    $ 9,843    $ 3,280    $ 18,072
                                       =======    =======    =======    ========
      Diluted earnings per share:
        Unitrode                       $   .14    $   .33    $   .08    $    .60
                                       =======    =======    =======    ========
        Benchmarq                      $   .11    $   .22    $   .17    $    .44
                                       =======    =======    =======    ========
        Combined                       $   .14    $   .30    $   .10    $    .56
                                       =======    =======    =======    ========
</TABLE>

LEGAL SETTLEMENT

BENCHMARQ Microelectronics, Inc. ("Benchmarq"), a wholly owned subsidiary of the
Company, was involved in litigation with Dallas Semiconductor Corporation
("DSC") in which DSC alleged, among other things, the willful and deliberate
infringement by Benchmarq of certain patents owned by DSC. DSC sought, among
other things, an injunction against further infringement relating to certain
products, damages for lost profits (which may under certain circumstances be
trebled), interest and attorney fees. Benchmarq had sued DSC in the same court,
alleging unfair business practices and seeking damages. The respective lawsuits
were settled on September 14, 1998 and dismissed with prejudice. The settlement
involves a cash payment of $5.5 million by Benchmarq and a limited cross license
agreement between the parties. The Company will record the charge to
non-operating expense in its financial statements for the third quarter ended
October 31, 1998.

                                       -9-
<PAGE>   10
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     Six months ended
                                      ------------------------------------------
                                      August 1,  August 2,  August 1,  August 2,
                                         1998       1997       1998       1997
                                      ------------------------------------------
<S>                                    <C>        <C>        <C>        <C>

      Net revenues                      100.0%     100.0%     100.0%     100.0%
      Cost of revenues                   53.3       47.0        57.9      46.9
                                        -----      -----       -----     -----
           Gross profit                  46.7       53.0        42.1(1)   53.1
                                        -----      -----       -----     -----
      Operating expenses:
        Research & development expenses  11.5        9.2        12.5       9.8
        Selling, general and
           administrative expenses       17.5       16.3        18.6      16.4
        New fab pre-operating expenses    3.3        3.4         3.6       3.5
        Restructuring and merger costs    2.1          -         4.6         -
                                        -----      -----       -----     -----
           Total operating expenses      34.3       28.9        39.3      29.7
                                        -----      -----       -----     -----

      Income from operations             12.3       24.2         2.8      23.3
      Other income (expense)              4.9        2.6         0.4       2.9
                                        -----      -----       -----     -----
      Income before income tax
        provision                        17.3       26.7         3.2      26.3
      Net income                         10.0%      16.9%        1.1%     16.5%
</TABLE>


(1) Gross profit was 46.6% excluding special charges

Three Months Ended August 1, 1998 versus Three Months Ended August 2, 1997

Net sales for the Company's second quarter ended August 1, 1998 were $29.7
million compared with $48.2 million in the previous year's second quarter, a
decrease of $18.5 million, or 38%. The decline was principally due to a
reduction of approximately $9.7 million in motion control products, primarily
related to a specific disk drive customer, and approximately $5.5 million in
power management products, primarily due to the weakness in the EDP market.
Approximately 61% of sales in the second quarter were international compared
with 63% in the prior year.

During the three and six-month periods ended August 1, 1998, the Company
discontinued the manufacture of a specific custom circuit to Western Digital
Corporation, which in the past had accounted for more than 10% of the Company's
sales. The Company has determined not to compete for future versions of this
custom circuit. As a result, the Company recorded special charges in the first
quarter ended May 2, 1998 to exit this business and re-align its cost structure
with the reduced level of sales. See Note 5 in the Company's consolidated
financial statements for further information.

Gross profit as a percentage of net sales was 46.7% in the second 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 demand from
the Company's served markets which reduced utilization of manufacturing
capacity. The Company currently expects its gross profit percentage in the third
quarter to be approximately the same as the previous quarter.

Weakness, primarily in the EDP market, has affected and may continue to affect
the Company's bookings and the scheduling of existing backlog. 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) increased in the second quarter of fiscal 1999 compared to the
preceding quarter. Customers continue to provide limited visibility as to future
demand and revenues are increasingly dependent on turns business.



                                      -10-

<PAGE>   11
RESULTS OF OPERATIONS (continued)

Some of the Company's customers and distributors must still balance their
inventories to demand before making any significant purchase commitments.

Research and development expenses were approximately 11.5% of net sales, or 
$3.4 million, compared with 9.2%, or $4.4 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 17.5% of net sales, or $5.2 million, compared with 16.3%, or 
$7.9 million, in the previous year's second quarter. The decrease of
$2.7 million was primarily due to reductions in accruals for incentive
compensation and lower sales commissions.

In the second quarter of fiscal year 1999, the Company incurred $1.0 million in
pre-operating expenses associated with the new 6" BiCMOS wafer fabrication
facility in Merrimack, New Hampshire. Pre-operating costs, which are incurred
prior to the commencement of production, relate primarily to the qualification
of equipment and manufacturing processes to meet design, test, and reliability
as well as to recruit and train personnel. The Company spent a total of 
$8.4 million in pre-operating expenses associated with this new facility. The
new wafer fabrication facility became operational at the end of the second
quarter. The Company does not expect to record any additional pre-operating
costs.

During the second quarter of fiscal year 1999, the Company recorded merger costs
of $0.6 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.

The consolidated effective tax rate for the quarter ended August 1, 1998 was
42.2% compared with 37.0% for the quarter ended August 2, 1997. Excluding
non-deductible merger costs, the effective tax rate was 37.7% in the second
quarter of fiscal year 1999.

Net income for the second quarter of fiscal year 1999 was $3.0 million, or $.12
per diluted share, compared with net income of $8.1 million, or $.33 per diluted
share for the comparable period of the prior year. Excluding merger costs, net
income would have been $3.6 million, or $.14 per diluted share, for the second
quarter of fiscal year 1999.

Six Months Ended August 1, 1998 versus Six Months Ended August 2, 1997

Net sales for the six months ended August 1, 1998 were $57.7 million compared
with $89.0 million in the previous year's six-month period, a decrease of 
$31.3 million, or 35%. The decline was principally due to a reduction of
approximately $20.0 million in motion control products, primarily related to a
specific disk drive customer, and approximately $8.7 million in power management
products, primarily due to the weakness in the EDP market. Approximately 61% of
sales for the first six months were international compared with 65% in the prior
year.

Gross profit as a percentage of net sales was 42.1% compared to 53.1% 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 46.6%. The decrease in the gross profit percentage compared to the
prior year, excluding the special charge, was primarily due to lower demand from
the Company's served markets which reduced utilization of manufacturing
capacity.



                                      -11-

<PAGE>   12
RESULTS OF OPERATIONS (continued)

Research and development expenses were approximately 12.5% of net sales, or 
$7.2 million, compared with 9.8%, or $8.7 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 18.6% of net sales, or $10.8 million, compared with 16.4%, or
$14.6 million, in the previous year. The decrease of $3.8 million was primarily
due to reductions in accruals for incentive compensation and lower sales
commissions.

During the first six months of fiscal year 1999, the Company incurred 
$2.1 million in pre-operating expenses associated with the new 6" BiCMOS wafer
fabrication facility in Merrimack, New Hampshire.

During the first half of fiscal year 1999, the Company recorded special charges
totaling $7.8 million of which $2.6 million was charged to cost of sales,
$2.7 million was charged to restructuring and merger costs in operating
expenses, and $2.5 million was charged to other income (expense). See Note 5 in
the Company's consolidated financial statements for further information.

The consolidated effective tax rate for the six months ended August 1, 1998 was
66.4% compared with 37.2% for the six months ended August 2, 1997. Excluding
non-deductible merger costs, the effective tax rate was 37.7% in the first half
of fiscal year 1999.

Net income for the six months ended August 1, 1998 was $0.6 million, or $.02 per
diluted share, compared with net income of $14.7 million, or $.60 per diluted
share, for the comparable period of the prior year. Excluding special charges,
net income would have been $6.0 million, or $.24 per diluted share, for the six
months ended August 1, 1998.

FINANCIAL CONDITION

Cash and cash equivalents at August 1, 1998 decreased by $1.5 million to
$63.6 million since the beginning of fiscal year 1999. Cash flow from operating
activities was essentially unchanged for the six months ended August 1, 1998. 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 $3.2 million for the first six months of fiscal year
1999. In fiscal year 1999, the Company expects capital expenditures to total
approximately $14 to $16 million for the support of ongoing operations which
includes approximately $3 million for additional manufacturing capacity in the
new 6" wafer fab and is contingent on future business conditions.

The ratio of current assets to current liabilities was 5.13:1 at August 1, 1998
compared with 2.86:1 at January 31, 1998. Working capital of $83.2 million at
August 1, 1998 increased by $9.4 million from January 31, 1998. Accounts
receivable at August 1, 1998 decreased by $7.2 million from January 31, 1998
primarily due to reduced sales. Receivable day sales outstanding ("DSO") were 46
days at August 1, 1998 compared to 50 days at January 31, 1998 and 51 days at
August 2, 1997. Income taxes payable at August 1, 1998 decreased by a total of
$2.5 million from January 31 1998, primarily due to a tax benefit recorded in
the first quarter as a result of the special charges. Accrued employee
compensation and benefits were $9.1 million lower than at year-end due to the
payment of incentive compensation related to the Company's performance in fiscal
year 1998.



                                      -12-

<PAGE>   13
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
is being accounted for on a pooling-of-interests basis. The Company expects to
record total merger-related costs, on a combined basis, of approximately
$2.7 million primarily for professional services, such as investment banking,
legal, and accounting.

The Company is currently unable to estimate what total integration costs will be
following the merger but does not anticipate these costs will have a material
adverse effect on the financial condition of the combined company.

LEGAL SETTLEMENT

On September 14, 1998, a settlement was reached in the respective lawsuits
between Benchmarq and Dallas Semiconductor Corporation. The settlement involves
a cash payment of $5.5 million by Benchmarq and a limited cross license
agreement between the parties. The Company will record the charge to
non-operating expense in its financial statements for the third quarter ended
October 31, 1998. See Item 1. Legal Proceedings and Note 6 in the Company's 
consolidated financial statements for further information.

YEAR 2000 IMPACT

The Company has initiated a complete analysis of all computer-based software and
hardware to ensure Year 2000 compliance. In addition, the Company has begun
replacement of certain business systems with Year 2000 compliant software 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 could be negatively impacted if it or a third party is
unsuccessful in properly addressing this issue. Year 2000 project expenditures,
excluding capitalized cost associated with a new enterprise resource planning
system, are not anticipated to exceed $1.0 million and are primarily for
modifications to test equipment. The Year 2000 project is expected to be
substantially completed by the end of fiscal year 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 two customers, IBM Corporation and Compaq Corporation, represented
approximately 13% and 10%, respectively, of sales in the second quarter of
fiscal year 1999 compared with 10% and 7%, respectively, of sales in the second
quarter of fiscal year 1998, and 15% and 10%, respectively, of sales for the
first six months of fiscal year 1999 compared to 9% and 6%, respectively, of
sales for the first six months of fiscal year 1998. The loss or a substantial
reduction in sales from these customers would have a material adverse effect
upon the Company's business. Sales to Western Digital Corporation represented
approximately 21% of sales in the second quarter and 24% for the first six
months of the prior fiscal year, but were significantly less than 10% in
comparable periods in the current fiscal year.



                                      -13-

<PAGE>   14
FACTORS AFFECTING FUTURE RESULTS

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 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 will continue 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 year 2000. Additionally, the
Company has an option to purchase and TSMC has committed to provide certain
additional wafers through the 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. 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
will also result 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.



                                      -14-


<PAGE>   15
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.






                                      -15-


<PAGE>   16
                           PART II. OTHER INFORMATION
               Unitrode Corporation and Consolidated Subsidiaries
                                 August 1, 1998


ITEM 1.  LEGAL PROCEEDINGS

BENCHMARQ Microelectronics, Inc. ("Benchmarq"), a wholly owned subsidiary of
the Company, was involved in litigation with Dallas Semiconductor Corporation
("DSC") in which DSC alleged, among other things, the willful and
deliberate infringement by Benchmarq of certain patents owned by DSC. DSC
sought, among other things, an injunction against further infringement relating
to certain products, damages for lost profits (which may under certain
circumstances be trebled), interest and attorney fees. Benchmarq had sued DSC
in the same court, alleging unfair business practices and seeking damages. The
respective lawsuits were settled on September 14, 1998 and dismissed with
prejudice. The settlement involves a cash payment of $5.5 million by Benchmarq
and a limited cross license agreement between the parties. The Company will
record the charge to non-operating expense in its financial statements for the
third quarter ended October 31, 1998.

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 alleges that certain manufacturing operations
of the Company, as well as certain manufacturing operations of the other
defendants, infringe sixteen Lemelson patents. The complaint seeks an injunction
against infringement of the patents, damages in an unspecified amount and
attorneys' fees. The complaint has not yet been served upon 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

The Registrant's annual meeting of stockholders was held on July 29, 1998, at
which three matters were submitted to a vote of security holders: (1) the
election of Robert J. Richardson as director of the Registrant for a two-year
term ending in 2000, and the election of Robert Gable and William R. Elder as
directors of the Registrant, each for a three-year term ending in 2001, and, (2)
the approval and ratification of an amendment to the Registrant's 1992 Employee
Stock Option Plan to increase the number of shares of common stock available for
issuance under the Plan from 6,000,000 shares to 7,000,000 shares, and, (3) the
approval of issuing of up to 8.6 million shares in connection with the
previously announced merger with BENCHMARQ Microelectronics, Inc. As of April
30, 1998, the record date for said meeting, there were outstanding 24,408,257
shares of the Registrant's common stock entitled to vote at the meeting. At such
meeting, the holders of 21,456,259 shares (88%) were represented in person or by
proxy, constituting a quorum. At such meeting, the vote with respect to the
matters proposed to the stockholders was as follows:

         (1)  ELECTION OF DIRECTORS:

                                         For           Withheld
                                     ----------        -------

              Mr. Gable              21,092,374        363,885
              Mr. Richardson         21,090,554        365,705
              Mr. Elder              21,090,954        365,305




                                      -16-

<PAGE>   17
ITEM 4.  SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS (continued)

         (2)  APPROVAL AND RATIFICATION OF AMENDMENT TO THE UNITRODE 1992
              EMPLOYEE STOCK OPTION PLAN:

                  For              Against         Abstain
              ----------          ---------        -------
              17,037,927          4,119,518        218,814

         (3)  APPROVAL OF ISSUING SHARES IN CONNECTION WITH BENCHMARQ MERGER:

                  For              Against         Abstain
              ----------           -------        ---------
              16,255,153           562,037        1,251,907

ITEM 5.  OTHER INFORMATION

None.

ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K

         (a)  Exhibits

              Exhibit 27 - Financial Data Schedule

         (b)  REPORTS ON FORM 8-K: On June 22, 1998, the Registrant filed a
              report on Form 8-K announcing that its Annual Meeting of
              Stockholders scheduled for June 29, 1998 would be adjourned and
              reconvened at a date later in July.

              On June 23, 1998, the Registrant filed a report on Form 8-K
              announcing that it had agreed with BENCHMARQ Microelectronics,
              Inc. to amend their previously reported Plan of Merger, dated
              March 2, 1998.



                                      -17-

<PAGE>   18
               Unitrode Corporation and Consolidated Subsidiaries
                                 August 1, 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



    September 14, 1998                    /s/ Robert J. Richardson
-------------------------------           --------------------------------------
Date                                      Robert J. Richardson
                                          Chairman and Chief Executive Officer

    September 14, 1998                    /s/ Cosmo S. Trapani
-------------------------------           --------------------------------------
Date                                      Cosmo S. Trapani
                                          Executive Vice President and
                                          Chief Financial Officer
                                          (Principal Financial and Accounting
                                          Officer)








                                      -18-