<PAGE>

                                    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 September 28, 1997
                                           
                                          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 0-3698
                                           
                                SILICONIX INCORPORATED
                (Exact name of registrant as specified in its charter)
                                           
        Delaware                                    94-1527868
(State or other jurisdiction                      (I.R.S. Employer
    of incorporation                             Identification No.)
    or organization)

                 2201 Laurelwood Road, Santa Clara, California 95054
                       (Address of principal executive offices)
                                           
           Registrant's telephone number including area code (408) 988-8000
                                           
    Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the 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
                                       ---       ---    
    Indicate the number of shares outstanding of each of the registrant's
classes of common stock:

          Common stock, $0.01 par value -- 9,959,680 outstanding shares as 
                                 of November 1, 1997.



                                        1

<PAGE>

                                SILICONIX INCORPORATED
                                           
                            TABLE OF CONTENTS TO FORM 10-Q
                                           

Part I.  Financial Information                                      Page No.

Item 1   Financial Statements (Unaudited)

           Consolidated statements of operations for the three
           months and nine months ended September 28, 1997                3 
           and September 29, 1996

           Consolidated balance sheets as of September 28, 1997
           and December 31, 1996                                          4

           Consolidated statements of cash flows for the nine
           months ended September 28, 1997 and September 29, 1996         5

           Notes to consolidated financial statements                     6-7

Item 2   Management's Discussion and Analysis of
         Financial Condition and Results of Operations                    8-10


Part II. Other Information

Item 6   Exhibits and Reports on Form 8-K                                 11
    
         Signature                                                        12


                                        2


<PAGE>

                                        PART 1


                                SILICONIX INCORPORATED

                        CONSOLIDATED STATEMENTS OF OPERATIONS

                                     (UNAUDITED)
<TABLE>
<CAPTION>
 

---------------------------------------------------------------------------------------------------------------------------
                                                          Three Months Ended                     Nine Months Ended

                                                 September 28,       September 29,       September 28,      September 29,
(IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)              1997                1996                1997               1996
---------------------------------------------------------------------------------------------------------------------------
<S>                                              <C>                 <C>                 <C>                 <C>     
Net sales                                          $  80,960           $  62,033           $ 231,196           $ 196,173
Cost of sales                                         48,848              37,771             141,779             116,736
                                                --------------------------------------------------------------------------
Gross profit                                          32,112              24,262              89,417              79,437
Research and development                               4,026               5,095              12,549              16,131
Selling, marketing, and administration                16,748              11,847              45,546              40,308
                                                --------------------------------------------------------------------------
Operating income                                      11,338               7,320              31,322              22,998
Interest expense                                         590                 592               1,750               1,774
Other (income) expense - net                              12                (158)                 (7)               (350)
                                                --------------------------------------------------------------------------
Income before taxes                                   10,736               6,886              29,579              21,574
Income taxes                                           2,362                 998               6,232               2,613
                                                --------------------------------------------------------------------------
Net income                                         $   8,374           $   5,888           $  23,347           $  18,961
                                                --------------------------------------------------------------------------
                                                --------------------------------------------------------------------------


Net income per share                               $    0.84           $    0.59           $    2.34           $    1.90
                                                --------------------------------------------------------------------------
                                                --------------------------------------------------------------------------


Shares used to compute earnings per share              9,960               9,960               9,960               9,960
                                                --------------------------------------------------------------------------
                                                --------------------------------------------------------------------------


</TABLE>
 

See accompanying notes to consolidated financial statements.


                                        3

<PAGE>

                                SILICONIX INCORPORATED

                             CONSOLIDATED BALANCE SHEETS


--------------------------------------------------------------------------------
                                                 September 28,   December 31,
(IN THOUSANDS)                                       1997           1996
--------------------------------------------------------------------------------
                                                  (UNAUDITED)

Assets
--------------------------------------------------------------------------------

Current assets:
 Cash and equivalents                            $   10,577      $   12,201
 Short term investment with affiliate                 6,044          12,136
 Accounts receivable, less allowances                42,809          37,044
 Accounts receivable from affiliates                 16,593          14,802
 Inventories                                         35,986          30,162
 Other current assets                                17,502           8,044
 Deferred income taxes                                7,314           5,314
                                                  ---------------------------
  Total current assets                              136,825         119,703
                                                  ---------------------------


Property, plant and equipment, at cost:
 Land                                                 1,174           1,183
 Buildings and improvements                          43,765          42,672
 Machinery and equipment                            208,193         187,791
                                                  ---------------------------
                                                    253,132         231,646
 Accumulated depreciation                          (136,307)       (124,524)
                                                  ---------------------------
  Net property, plant and equipment                 116,825         107,122
Other assets                                         14,849          11,844
                                                  ---------------------------
  Total assets                                   $  268,499      $  238,669
                                                  ---------------------------
                                                  ---------------------------


Liabilities and Shareholders' Equity
--------------------------------------------------------------------------------

Current liabilities:
 Current portion of debt obligations             $        -      $    1,041
 Accounts payable                                    30,365          26,286
 Accounts payable to affiliates                       9,875          11,115
 Accrued payroll and related compensation            13,909          13,614
 Accrued liabilities                                 31,902          29,418
                                                  ---------------------------
  Total current liabilities                          86,051          81,474

Long-term related party debt                         34,570          34,570
Long-term debt, less current portion                  3,879           4,859
Deferred income taxes                                 4,148           1,148
                                                  ---------------------------
  Total liabilities                                 128,648         122,051
                                                  ---------------------------
Shareholders' equity:
 Common stock                                           100             100
 Additional paid-in-capital                          59,458          59,440
 Retained earnings                                   80,882          57,535
 Accumulated translation adjustments                   (589)           (457)
                                                  ---------------------------
  Total shareholders' equity                        139,851         116,618
                                                  ---------------------------
  Total liabilities and shareholders' equity     $  268,499      $  238,669
                                                  ---------------------------
                                                  ---------------------------

See accompanying notes to consolidated financial statements.


                                        4

<PAGE>

                                SILICONIX INCORPORATED

                        CONSOLIDATED STATEMENTS OF CASH FLOWS

                                     (UNAUDITED)

--------------------------------------------------------------------------------
                                          Nine Months Ended   Nine Months Ended
                                            September 28,       September 29,
(IN THOUSANDS)                                   1997               1996 
--------------------------------------------------------------------------------

Cash flows from operating activities:
Net income                                     $ 23,347           $  18,961
Adjustments to reconcile net income to net
 cash provided by operating activities:
  Depreciation and amortization                  16,676              12,865
  Deferred income taxes                           1,000              (1,900)
  Undistributed earnings from joint venture      (2,265)             (1,514)
  Payment of pension benefits                    (1,394)                (23)
  Other non-cash expenses                           481                 377
  Changes in:
   Accounts receivable                           (5,438)              8,245
   Accounts receivable from affiliates           (1,791)             (1,684)
   Inventories                                   (5,822)             (5,180)
   Other current assets                          (8,326)             (1,469)
   Accounts payable                               4,036              (8,399)
   Accounts payable to affiliates                (1,240)             (1,445)
   Accrued liabilities                            2,707                 183
                                               ----------------------------
Net cash provided by operating activities        21,971              19,017
                                               ----------------------------

Cash flows from investing activities:
Purchase of property, plant and equipment       (24,610)            (31,829)
Investment in joint venture                           -              (2,053)
Short term investment with affiliate              6,092              12,768
Purchase of other assets                         (3,750)             (2,340)
                                               ----------------------------
Net cash used in investing activities           (22,268)            (23,454)
                                               ----------------------------

Cash flows from financing activities:
Repayment of short term debt                       (999)                  -

Effect of exchange rate changes on
 cash and equivalents                              (328)                123
                                               ----------------------------

Net decrease in cash and equivalents             (1,624)             (4,314)

Cash and equivalents:
Beginning of period                              12,201              10,513
                                               ----------------------------
End of period                                  $ 10,577            $  6,199
                                               ----------------------------
                                               ----------------------------


See accompanying notes to consolidated financial statements.


                                        5

<PAGE>

                                SILICONIX INCORPORATED
                                           
                      NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                     (UNAUDITED)
                                           

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 with the instructions to Form 10-Q and Article 10 of
Regulation S-X.  Accordingly, they do not include all of the information and
footnotes required by generally accepted accounting principles for complete
financial statements.

     In the opinion of the management of the Company, the consolidated financial
statements appearing herein contain all adjustments (consisting only of normal
recurring accruals) necessary for a fair presentation of the results for, and as
of the end of, the periods indicated therein.  These statements should be read
in conjunction with the Company's December 31, 1996 consolidated financial
statements and notes thereto.  The results of operations for the first nine
months of 1997 are not necessarily indicative of the results to be expected for
the full year.

NOTE 2.   INVENTORIES
     
     The components of inventory consist of the following:
     
                           September 28,       December 31, 
                               1997               1996
                               ----               ----
                                    (In thousands)

     Finished goods      $     4,715         $     6,105
     Work-in-process          24,686              18,838
     Raw materials             6,585               5,219
                         -----------         -----------
                         $    35,986         $    30,162
                         -----------         -----------
                         -----------         -----------

NOTE 3.        CONTINGENCIES

     The Company is party to two environmental proceedings.  The first involves
property that the Company vacated in 1972. The California Regional Water Quality
Control Board (RWQCB) issued a cleanup and abatement order to both the Company
and the current owner of the property.  The Company subsequently reached a
settlement of this matter with the current owner in which the current owner
indemnifies the Company against any liability that may arise out of any
governmental agency actions brought for environmental cleanup of the site,
including liability arising out of the current cleanup and abatement order.  The
second proceeding involves the Company's current facility in Santa Clara. The
RWQCB issued a cleanup and abatement order based on the discovery of
contamination of both the soil and the groundwater on the property by certain
chemical solvents. The Company is currently engaged in certain remedial action
and has accrued $750,000 for the estimated future costs related to this matter.

     In management's opinion, based on discussion with legal counsel and other
considerations, the ultimate resolution of the above-mentioned matters will not
have a material adverse effect on the Company's consolidated financial condition
or results of operations. 

     The Company is engaged in discussions with various parties regarding patent
licensing and cross patent licensing issues. In the opinion of management, the
outcome of these discussions will not have a material adverse effect on the
Company's consolidated financial condition or overall trends in the results of
operations.


                                        6

<PAGE>

                                SILICONIX INCORPORATED
                                           
                      NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                     (UNAUDITED)
                                           


NOTE 4.   RECENT ACCOUNTING PRONOUNCEMENTS

     In February 1997, the Financial Accounting Standards Board issued Statement
of Financial Accounting Standards ("SFAS") No. 128, "Earnings Per Share."   SFAS
No. 128 requires the presentation of basic earnings per share ("EPS") and, for
companies with complex capital structures, diluted EPS.  SFAS No. 128 is
effective for annual and interim periods ending after December 15, 1997.  The
Company expects that basic EPS will not differ materially from net income per
share as presented in the accompanying consolidated financial statements.

     In June 1997, the Financial Accounting Standards Board issued SFAS No. 130,
"Reporting Comprehensive Income," and SFAS No. 131, "Disclosures about Segments
of an Enterprise and Related Information."  SFAS No. 130 establishes standards
for reporting and presentation of comprehensive income and its components and is
effective for fiscal years beginning after December 15, 1997.  SFAS No. 131,
effective for fiscal years beginning after December 15, 1997, establishes
standards for an enterprise to report information about operating segments in
annual financial statements and interim financial reports.  The Company is
presently analyzing these statements and has not yet determined the impact on
the Company's financial statements. 


                                        7

<PAGE>

ITEM 2.

MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
CONDITION AND RESULTS OF OPERATIONS


RESULTS OF OPERATIONS


     Siliconix designs, markets, and manufactures power and analog semiconductor
products. The Company focuses on technologies and products for the computer,
data storage, communications, and automotive markets.


     Revenues in the third quarter of 1997 increased to a record $81.0 
million, compared with $62.0 million in the third quarter of 1996.  For the 
first nine months of 1997, revenues were $231.2 million, compared with $196.2 
million for the first nine months of 1996.  Increased demand from the 
telecommunications market for power MOSFET products accounted for much of the 
revenue growth in the third quarter and first nine months of fiscal 1997.  
Sales of power MOSFETs grew by 39% from the third quarter of last year and 
again achieved record quarterly revenues.  Power MOSFET sales for the first 
nine months of 1997 increased 25% from the first nine months of 1996.  Sales 
in Europe and North America were up 32% and 37%, respectively, from the third 
quarter of 1996.  Revenues in Asia Pacific, excluding Japan, were up 53% with 
revenues in Japan down somewhat from the third quarter of 1996.  Sales in 
Europe and North America were up 31% and 21%, respectively, from the first 
nine months of 1996.  Revenues in Asia Pacific, excluding Japan, were up 39% 
with revenues in Japan down somewhat from the first nine months of 1997.  The 
revenue decrease in Japan is primarily due to intense pricing competition, 
caused in part by excess DRAM capacity in Japan which has been converted to 
PowerMOS production.  In addition, the weakness of the yen against the dollar 
during 1997 has also contributed to the revenue decrease in Japan.

     Gross margin increased to 40% in the third quarter of 1997 from 39% in 
the third quarter of 1996.  Gross margin for the first nine months of 1997 
decreased to 39% from 40% for the same period in 1996. The decrease in 
year-to-date margins is primarily due to pricing pressures worldwide, but 
especially in Japan, as well as start-up costs associated with the leased 
fabrication facility in Itzehoe, Germany. As production at the leased 
fabrication facility in Itzehoe, Germany, reaches its planned capacity by 
mid-1998, we anticipate a favorable impact on manufacturing costs, resulting 
in an increase in gross margin related to this area.

     Research and development as a percentage of revenues decreased to 5% for
the third quarter of 1997 from 8% for the third quarter of 1996.  Research and
development as a percentage of revenues was 5% and 8% for the first nine months
of 1997 and 1996, respectively.  The Company remains committed to the
development of future products and continues to invest in power MOSFET and power
IC technology as well as product development.  Planned research and development
expenditures for 1997 are expected to be below those of 1996.

     Selling, marketing, and administration expenses as a percentage of 
revenues increased to 21% for the third quarter of 1997 from 19% for the 
third quarter of 1996.  However, selling, marketing, and administration 
expenses as a percentage of revenues for the first nine months of 1997 
decreased to 20% from 21% for the same period of 1996.  Continued economies 
of scale and the Company's cost reduction programs will be offset in the 
second half of the year by incremental spending in anticipation of 1998 
growth. The Company anticipates 1997 selling, marketing, and administration 
expenses as a percentage of revenues to be comparable to 1996 levels.

                                        8

<PAGE>

     Interest expense for the first nine months of 1997 remained flat at $1.8
million compared to the first nine months of 1996, as short-term market interest
rates have not fluctuated significantly over the past year.
     
     Income tax expense increased in the third quarter of 1997 to $2.4 million
from $1.0 million for the third quarter of 1996.  For the first nine months of
1997, income tax expense was $6.2 million as compared to $2.6 million for the
first nine months of 1996.  This increase is due to the depletion of  net
operating loss carryforwards at the end of 1996 and the increase in earnings
before taxes during the first nine months of 1997.

     During its quarterly assessment of deferred income taxes, management 
reduced the valuation allowance on deferred income tax assets.  This decision 
to recognize additional deferred income tax assets was based on management's 
belief that, it is more likely than not, the Company will realize benefit 
from a portion of its deferred income taxes. The primary positive factors 
assessed by management in reaching its conclusion about the Company's ability 
to realize the deferred income tax assets include positive earnings and 
continued increases in gross profits for the past three years.

     The expectations for the future are that, even with the extremely volatile
environment in which the Company competes, operating income of the Company will
more than likely be sufficient to realize a portion of the deferred income tax
asset; however, due to certain factors beyond management's control, there can be
no assurance that sufficient taxable income will be generated in each of the
Company's taxing jurisdictions to realize recorded tax benefits. In addition,
there is no assurance that the Company will generate any earnings or any
specific level of continuing earnings in future years. 

     The primary negative factors assessed by management in reaching its
conclusion about the Company's ability to realize the net deferred income tax
asset are discussed in the section titled "Certain Factors" in the Management's
Discussion and Analysis of Financial Condition and Results of Operations section
of the Company's 1996 Annual Report on Form 10-K, which is incorporated herein
by reference.

LIQUIDITY AND CAPITAL RESOURCES

     Cash flows from operations were $22.0 million for the nine-month period
ended September 28, 1997 as compared to $19.0 million for the nine-month period
ended September 29, 1996.  Cash and equivalents decreased by $1.6 million and
the short term investment with affiliate decreased by $6.1 million from December
31, 1996 due to large expenditures in the first nine months of 1997.  These
included capital expenditures, royalty payments, commissions, yearly management
and employee bonuses, the 401(k) company match, and profit sharing
contributions.  Management expects 1997 cash flows from operations to be
sufficient to fund investments in capital expenditures and research and
development.

     Accounts receivable increased $5.8 million or 16% from December 31, 1996.
This increase is a result of record revenues earned in the third quarter of
1997.  Revenues for the third quarter of 1997 totaled $81.0 million, compared
with $72.8 million for the fourth quarter of 1996. In addition, there is
continuing revenue growth in Europe and longer payment terms are typically
afforded to European customers.



                                        9

<PAGE>

     Net affiliate receivables/payables increased $3.0 million from December 31,
1996 mainly due to timing differences of cash remitted to our unconsolidated
affiliates.  In addition, there was an increase in selling and administrative
expenses incurred on behalf of our unconsolidated affiliates, which are
reimbursed at cost.

     Inventories increased $5.8 million or 19% from December 31, 1996 
primarily due to the addition of manufacturing capacity, including the leased 
Itzehoe, Germany fabrication facility, in order to achieve 1997 planned 
revenue.

     Other current assets increased $9.5 million from December 31, 1996.  The
majority of this increase is due to purchases of equipment and supplies on
behalf of our subcontractors in Taiwan and Germany, which are reimbursed at
cost.
     
     Capital expenditures were $24.6 million in the first nine months of 1997,
compared to $31.8 million in the first nine months of 1996. These expenditures
were mainly related to additions for plant capacity expansion.  Capital spending
in 1997, funded from cash provided by operating activities, is expected to
approximate the 1996 level.

     Other assets increased $3.0 million or 25% from December 31, 1996 due to 
an increase in the Company's 50% share in earnings in the investment in 
Simconix, the Company's joint venture in The People's Republic of China.   
     
     Current liabilities increased $4.6 million or 6% from December 31, 1996. 
This increase is mainly due to the increase in income taxes payable associated
with high revenue growth during the first nine months of 1997.  In addition, the
difference is attributed to the timing of cash remittances made to our
subcontractors in Taiwan and Germany.

     Long-term debt decreased $1.0 million or 20% from December 31, 1996 mainly
due to the payment of benefits under our Taiwan pension plan for employees
electing early retirement.


SAFE HARBOR STATEMENT

     "Safe Harbor" Statement under the Private Securities Litigation Reform Act
of 1995: With the exception of historical information, the matters discussed in
this Form 10-Q are forward-looking statements that involve risks and
uncertainties including, but not limited to, economic conditions, product demand
and industry capacity, competitive products and pricing, manufacturing
efficiencies, new product development, availability of raw materials and
critical manufacturing equipment, the regulatory and trade environment, and
other risks indicated in filings with the Securities and Exchange Commission.



                                        10

<PAGE>

PART II - OTHER INFORMATION


ITEM 6:  EXHIBITS AND REPORTS ON FORM 8-K


      (a)   The following exhibits are filed herewith:

            10.13             Special Retention Bonus Plan (1998) of Siliconix
                              incorporated

            10.14             Amendment No. 1 to Change-in-Control Severance
                              Plan of Siliconix incorporated

            10.15             Amendment No. 1 to Siliconix Key Professional
                              Incentive Bonus Plan

            10.16             Amendment No. 2 to Siliconix Key Professional
                              Incentive Bonus Plan

            10.17             Amendment No. 1 to Siliconix Key Professional
                              Performance Unit Plan

            10.18             Amendment No. 2 to Siliconix Key Professional
                              Performance Unit Plan

            27.1              Financial Data Schedule

      (b)   No reports on Form 8-K were filed during the quarter ended
            September 28, 1997.


                                           
                                        11

<PAGE>

                                      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.


                                             SILICONIX INCORPORATED



Date: November 12, 1997                      By: /s/Juergen F. Biehn
                                                 -------------------
                                                 Juergen F. Biehn
                                                 Senior Vice President and
                                                 Chief Financial Officer


                                        12