<PAGE>   1





                       SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C.  20549
                                   FORM 10-Q





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

For quarterly period ended DECEMBER 31, 1996

[   ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE
SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD
FROM _______TO _______

Commission File No. 0-26690

                          ELANTEC SEMICONDUCTOR, INC.
             (Exact Name of registrant as specified in its charter)

           Delaware                                    77-0408929
--------------------------------------------------------------------------------
(State or other jurisdiction of                     (I.R.S. Employer
incorporation or organization)                     Identification No.)

675 Trade Zone Boulevard, Milpitas, California             95035
--------------------------------------------------------------------------------
(Address of principal executive offices)                 (Zip Code)

Registrant's telephone number, including area code: (408) 945-1323
--------------------------------------------------------------------------------

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 issuer's classes of
common stock, as of the latest practicable date.

                       Class Outstanding at December 31, 1996
--------------------------------------------------------------------------------
Common Stock,  $0.01 par value                      8,766,542 shares
<PAGE>   2

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                  Page
                                                                                                  ----
<S>              <C>                                                                               <C>
PART I           FINANCIAL INFORMATION

    Item 1.      Condensed Consolidated Financial Statements  . . . . . . . . . . . . . . . . .    3-5

                 Notes to Condensed Consolidated Financial Statements . . . . . . . . . . . . .    6-7

    Item 2.      Management's Discussion and Analysis of Financial Condition
                   and Results of Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   8-11

PART II          OTHER INFORMATION

    Item 6.      Exhibits and Reports on Form 8-K . . . . . . . . . . . . . . . . . . . . . . .     12

                 Signatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .     13
</TABLE>





<PAGE>   3
PART I.  FINANCIAL INFORMATION
Item 1.   Condensed Consolidated Financial Statements



                          ELANTEC SEMICONDUCTOR, INC.
             CONDENSED CONSOLIDATED STATEMENTS OF INCOME OPERATIONS
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
                                  (UNAUDITED)



<TABLE>
<CAPTION>
                                                                                 Three Months Ended
                                                                                     December 31,
                                                                             ----------------------------
                                                                               1996                1995
                                                                             --------            --------
<S>                                                                          <C>                 <C>
Net revenues                                                                 $  8,001            $  8,567
Cost of revenues                                                                4,810               4,062
                                                                             --------            --------
   Gross profit                                                                 3,191               4,505
Operating expenses:
   Research and development                                                     1,283               1,544
   Marketing, sales, general and administrative                                 2,106               1,850
                                                                             --------            --------
   Total operating expenses                                                     3,389               3,394
                                                                             --------            --------
Income from operations                                                           (198)              1,111
Interest and other income, net                                                     87                 105
                                                                             --------            --------
Income (Loss) before taxes                                                       (111)              1,216
Income tax (Benefit) provision                                                    (14)                 95
                                                                             --------            --------
Net income (Loss)                                                            $    (97)           $  1,121
                                                                             ========            ========
Net income (Loss) per share                                                  $  (0.01)           $   0.12
                                                                             ========            ========
Shares used in computing per share amounts                                      8,759               9,174
                                                                             ========            ========
</TABLE>





See accompanying notes to the condensed consolidated financial statements.





<PAGE>   4
                          ELANTEC SEMICONDUCTOR, INC.
                     CONDENSED CONSOLIDATED BALANCE SHEETS
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                                      Dec. 31          Sept. 30
                                                                                       1996            1996 (1)
                                                                                    -----------        --------
                                                                                    (Unaudited)
<S>                                                                                   <C>              <C>
ASSETS:                                               
Current assets:
   Cash and cash equivalents                                                           $7,079           $ 9,377
   Short-term investments                                                               7,010             6,663  
   Accounts receivable, net                                                             4,555             4,175
   Inventories                                                                          6,722             6,475
   Prepaid expenses and other current assets                                              706               554
                                                                                      -------          --------
Total current assets                                                                   26,090            27,244

Property and equipment, net                                                             8,329             7,360
Other assets, net                                                                         636               642
                                                                                      -------          --------
Total assets                                                                          $35,055          $ 35,246
                                                                                      =======          ========

LIABILITIES AND STOCKHOLDERS' EQUITY:
Current liabilities:
   Accounts payable and accrued liabilities                                           $ 4,532          $  5,335
   Deferred revenue                                                                     3,200             3,143
   Current portion of long-term debt and capital lease obligations                      1,288             1,128
                                                                                      -------          --------
Total current liabilities                                                               9,020             9,606

Long-term debt and capital lease obligations                                            2,033             1,566

Stockholders' equity                                                                   24,002            24,074
                                                                                      -------          --------
Total liabilities and stockholders' equity                                            $35,055          $ 35,246
                                                                                      =======          ========
</TABLE>




(1) The information in this column was derived from the Company's audited
    consolidated financial statements at September 30, 1996.





See accompanying notes to the condensed consolidated financial statements.





<PAGE>   5
                          ELANTEC SEMICONDUCTOR, INC.
                CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS
                                 (IN THOUSANDS)
                                  (UNAUDITED)



<TABLE>
<CAPTION>
                                                                            Three Months Ended
                                                                               December 31,
                                                                            -------    -------
                                                                             1996       1995
                                                                            -------    -------
<S>                                                                         <C>        <C>
OPERATING ACTIVITIES:
                                                                            -------    -------
Net income (loss)                                                           $   (97)   $ 1,121
Adjustments to reconcile net income to net cash
   provided by operating activities:
      Depreciation and amortization                                             474        377
      Changes in operating assets and liabilities:
          Accounts receivable                                                  (380)      (222)
          Inventories                                                          (247)      (768)
          Prepaid expenses and other current assets                            (152)        62
          Accounts payable and accrued liabilities                             (803)         8
          Deferred revenue                                                       57         (5)
                                                                            -------    -------
Net cash provided by (used in) operating activities                          (1,148)       573

INVESTING ACTIVITIES:
Purchase of available-for-sale securities                                      (347)     (1,255)
Purchase of property and equipment                                             (514)      (837)
Decrease in other assets                                                          6        333
                                                                            -------    -------
Net cash used in investing activities                                          (855)    (1,759)

FINANCING ACTIVITIES:
Payments on capital lease and other debt                                       (302)      (182)
Issuance of common stock                                                         25      8,259
                                                                            -------    -------
Net cash (used in)/provided by financing activities                            (277)     8,077

Increase (decrease) in cash and cash equivalents                             (2,280)     6,891
Cash and cash equivalents at beginning of period                              9,377      6,009
                                                                            -------    -------
Cash and cash equivalents at end of period                                  $ 7,097    $12,900
                                                                            =======    =======

SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Lease and installment financing for capital equipment                       $   929    $   421
Interest paid                                                               $    59    $    39
Taxes paid                                                                  $    25    $    58
</TABLE>



See accompanying notes to the condensed consolidated financial statements.





<PAGE>   6
ELANTEC SEMICONDUCTOR, INC.
NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

NOTE 1.  BASIS OF PRESENTATION

The unaudited condensed consolidated financial statements included herein have
been prepared by the Company pursuant to the rules and regulations of the
Securities and Exchange Commission.  Certain information and footnote
disclosures normally included in financial statements prepared in accordance
with generally accepted accounting principles have been condensed or omitted
pursuant to such rules and regulations.  In the opinion of management, all
adjustments (consisting of normal recurring items) considered necessary for a
fair presentation have been included.  The results of operations for the three
months ended December 31, 1996 are not necessarily indicative of the results to
be expected for the entire year.  These consolidated financial statements should
be read in conjunction with the consolidated financial statements and the notes
thereto included in the Company's Annual Report on Form 10-K for the year 
ended September 30, 1996.

The Company's fiscal year end is the Sunday closest to September 30.  The
Company's fiscal quarters end on the Sunday closest to the end of the calendar
quarter. For convenience, the Company has indicated that its quarters end on
December 31, March 31, June 30 and September 30.

NOTE 2.  CASH AND CASH EQUIVALENTS

The Company considers all highly liquid investments with an original maturity
(at the date of purchase) of three months or less to be the equivalent of cash
for purposes of balance sheet and statement of cash flows presentation.  Cash
and cash equivalents are carried at cost, which approximates market value.

NOTE 3.  SHORT-TERM INVESTMENTS

The Company's policy is to invest in various short-term instruments with
investment grade credit ratings.  Generally such investments have contractual
maturities of less than one year.  All of the Company's marketable investments
are classified as "available-for-sale" and the Company classifies its
available-for-sale portfolio as available for use in its current operations.
At December 31, 1996, there was no significant difference between the fair
market value and the underlying cost of such securities.

NOTE 4.  INVENTORIES

Inventories are stated at the lower of standard cost (first-in, first-out
method) or market and consist of the following balances in thousands:

<TABLE>
<CAPTION>
                                                 December 31,     September 30,
                                                    1996              1996
                                                 ------------     -------------
        <S>                                        <C>               <C>
        Raw materials                              $   797           $   800
        Work-in-process                              4,745             4,266
        Finished goods                               1,180             1,409
                                                   -------           -------
                                                   $ 6,722           $ 6,475
                                                   =======           =======
</TABLE>





<PAGE>   7
NOTE 5.  NET INCOME (LOSS) PER SHARE

Net income per share is calculated based on the weighted average number of
common and dilutive common share equivalents outstanding using the Treasury
Stock method.  Common share equivalents reflect the dilutive effect of
outstanding stock options.

Dilutive securities include options of warrants. Loss per share excludes common
equivalent shares as the effect on net loss is antidilutive.



<PAGE>   8
ITEM 2.  MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
         RESULTS OF OPERATIONS

Except for the historical information contained herein, matters discussed in
the Form 10-Q may contain forward looking statements that involve risks and
uncertainties.  These risks and uncertainties include business conditions and
growth in the markets the Company serves, fluctuations in gross margin due to
the initiation of new manufacturing processes, ability to control manufacturing
yields, timely availability and acceptance of new products, the impact of
competitive products and pricing, and the Company's ability to meet customer
delivery schedules. The Company's actual future results could differ materially
from those discussed here.   Factors that could cause or contribute to such
differences include, but are not limited to, those discussed in this section,
as well as in the section entitled "Business" in the Company's 1996 Form 10-K
filed with the Securities and Exchange Commission.

RESULTS OF OPERATIONS - Net sales for the first quarter of fiscal 1997 were $8.0
million compared to $8.6 million for the corresponding period in fiscal 1996, a
decrease of approximately 7%.  This decrease is attributed to higher unit sales
volume offset by a shift in sales mix to lower priced products and lower average
selling prices due to competitive pressures.

Cost of goods sold increased to approximately 60% of net sales for the first
quarter of fiscal 1997 compared to 47% for the first quarter of fiscal 1996.
The resulting decrease in gross margins is due primarily to increased
manufacturing variances caused by lower production volumes, increased
unfavorable manufacturing yield variances and lower average selling prices due
to a more competitive market environment.

Research and development expenses in the first quarter of fiscal 1997 were $1.3
million, representing a decrease of 13% from that the $1.5 million reported in
the first quarter of fiscal 1996.  As a percentage of net sales, expenditures
for research and development decreased from approximately 18% in the first
quarter of fiscal 1996 to approximately 16% in the first quarter of fiscal 1997.
This decrease is attributable to decreased expenditures for mask sets, silicon
and other materials.  The Company expects to incur higher absolute research and
development expenses in the future.  However, there can be no that net revenues
will fluctuate at the same rate as the anticipated research and development
expenses.

Marketing, sales, general and administrative expenses for the first quarter of
fiscal 1997 were $2.1 million, representing an increase from the $1.9 million
reported for the same period in fiscal 1996.  As a percentage of net sales,
selling, general and administrative expenses increased from approximately 21%
of net sales in the first quarter of fiscal 1996 to 26% of net sales in the
first quarter of fiscal 1997.  The increase as a percentage of net sales
reflects the lower volume of sales in the first quarter of fiscal 1997.

The Company's provision for income taxes for the first quarter of fiscal 1997 is
lower than the statutory rate, principally due to the benefit of net operating
loss carryforwards offset by alternative minimum taxes and foreign withholding
taxes.





<PAGE>   9

Elantec's operating results have been, and in the future may be, subject to
fluctuations due to a wide variety of factors including the timing of or delays
in new product and process technology announcements and product introductions
by the Company or its competitors, competitive pricing pressures, fluctuations
in manufacturing yields, changes in the mix of product sold, availability and
costs of raw materials, the cyclical nature of the semiconductor industry,
industry-wide wafer processing capacity,  economic conditions in various
geographic areas, and costs associated with other events, such as
underutilization or expansion of production capacity, intellectual property
disputes, environmental regulation, or other litigation.  Further, there can be
no assurance that the Company will be able to compete successfully in the
future against existing or potential competitors or that the Companies
operating results will not be adversely affected by increased price
competition.

The semiconductor industry is highly cyclical and has been subject to
significant economic fluctuations at various times that have been characterized
by rapidly fluctuating product demand, periods of over and under capacity, and
accelerated erosion of average selling prices. A material change in
industry-wide production capacity, shift in industry capacity toward products
competitive with the Company's products, rapidly fluctuating demand, or other
factors could result in a rapid decline in product pricing or unit volumes
which could adversely affect the Company's operating results.

To address future capacity requirements, the Company plans to complete an
extensive production expansion at its primary manufacturing facility in
Milpitas, California. This expansion program faces a number of substantial
risks including, but not limited to, delays in construction, cost overruns,
equipment delays or shortages, manufacturing start-up or process problems, or
difficulties in hiring key managers and technical personnel. From time to time,
the Company has experienced production difficulties that have caused delivery
delays and quality problems.  There can be no assurance that the Company will
not experience manufacturing problems and product delivery delays in the future
as a result of, among other things, changes to its process technologies,
ramping production, installing new equipment at its facilities and constructing
new facilities in California. Further, the Company's has a single wafer
fabrication facility.  If the Company were unable to use this facility, as a
result of a natural disaster or otherwise, the Company's operations would be
materially adversely affected.

The Company's manufacturing expansion will result in a significant increase in
fixed and operating expenses. As commercial production at the new fabrication
facility commences, the operating costs will be classified as cost of revenues,
and the Company will begin to recognize depreciation expense relating to the
facility.  Accordingly, although the Company expects the Milpitas fabrication
facility to contribute to revenues in fiscal 1997, the Company will recognize
substantial operating expenses associated with the facility in 1997, which
could reduce gross margins.  Specifically, as commercial production begins in
fiscal 1997, the Company anticipates incurring substantial operating costs and
depreciation expense relating to the facility before production of substantial
volume is achieved.  Accordingly, if revenue levels do not increase
sufficiently to offset these additional expense levels, or if the Company is
unable to achieve gross comparable to the Company's current products, the
Company's future results of operations could be adversely impacted.

New products, process technology and start-up costs associated with the
Milpitas wafer fabrication facility will require significant research and
development expenditures.  However, there can be no assurance that the Company
will be able to develop and introduce new products in a timely manner,





<PAGE>   10
that new products will gain market acceptance or that new process technologies
can be successfully implemented.  If the Company is unable to develop new
products in a timely manner, and to sell them at gross margins comparable to
the Company's current products, the future results of operations could be
adversely impacted.

The Company's manufacturing operations depend upon obtaining adequate raw
materials on a timely basis. The number of vendors of certain raw materials,
such as silicon wafers, ultra-pure metals and certain chemicals and gases is
very limited.  In addition, certain materials used by the Company require long
lead times and are available from only a few suppliers.  For example, the
Company uses four inch silicon wafers in its wafer fabrication processes.  From
time to time, vendors have extended lead times or limited supply of four inch
wafers to the Company. The Company's results of operations would be adversely
affected if it were unable to obtain adequate supplies of raw materials in a
timely manner or if there were significant increases in the costs of raw
materials.

Part of the Company's future bipolar product development strategy includes the
development of an alternative form of silicon-on-insulator ("SOI") technology
called bonded wafers.  The Company believes that, if successful, the bonded
wafer technology could provide technologically advanced products at a lower
cost than the current dielectric isolation complementary bipolar technology.
However, there can be no assurance that the development of the bonded wafer
technology can be successfully accomplished in a timely manner or that it will
proved the desired improvements over the Company's current technology.
Significant delays in the development of the bonded wafer technology or
manufacturing problems associated with transferring the Company's current
product line to this technology would have a material adverse affect on the
Company's business and results of operations.  In addition, delays in the
development of this technology would adversely affect the Company's new product
development program.

The semiconductor industry is extremely capital intensive.  To remain
competitive, the Company must continue to invest in advanced manufacturing and
test equipment.  In fiscal 1997, the Company expects to expend approximately
$9.8 million in capital expenditures and anticipates significant continuing
capital expenditures in the next several years.  There can be no assurance that
the Company will not be required to seek financing to satisfy its cash and
capital needs or that such financing will be available on terms satisfactory to
the Company.  If such financing is required and if such financing is not
available on terms satisfactory to the Company, its operations would be
materially adversely affected.

The semiconductor industry is characterized by vigorous protection and pursuit
of intellectual property rights or positions, which have resulted in
significant and often protracted and expensive litigation.  In recent years,
there has been a growing trend of companies to resort to litigation to protect
their semiconductor technology from unauthorized use by others. The Company
believes its products do not infringe upon any valid patents.  However, there
can be no assurance that the Company's position in these matters will prevail.
There can be no assurance that additional future claims alleging infringement
of intellectual property rights will not be asserted against the Company.  The
intellectual property claims that have been made, or may be asserted against
the Company in the future, could require that the Company discontinue the use
of certain processes or cease the manufacture, use and sale of infringing
products.  Additionally, the company may incur significant litigation costs and
damages to develop noninfringing technology.  There can be no assurance that
the Company would be able to obtain such licenses on acceptable terms or to
develop noninfringing technology without a material adverse effect on the
Company.





<PAGE>   11
The Company is subject to a variety of regulations related to hazardous
materials used in its manufacturing process.  Any failure by the Company to
control the use of, or to restrict adequately the discharge of, hazardous
materials under present or future regulations could subject it to substantial
liability or could cause its manufacturing operations to be suspended.

The Company's Common Stock has experienced substantial price volatility and
such volatility may occur in the future, particularly as a result of
quarter-to-quarter variations in the actual or anticipated financial results of
the Company, the companies in the semiconductor industry or in the markets
served by the Company, or announcements by the Company or its competitors
regarding new product introductions.   In addition, the stock market has
experienced extreme price and volume fluctuations that have affected the market
price of many technology companies' stock in particular.  These factors may
adversely affect the price of the Common Stock.

LIQUIDITY AND CAPITAL RESOURCES - During the first three months of fiscal 1997,
the Company financed its operations primarily from existing cash balances. At
December 31, 1996, the Company had approximately $14.1 million of cash and
short-term investments.

Net cash used in operating activities was $1.1 million for the three months
ended December 31, 1996 and consisted primarily of increases in inventory and
accounts receivable and a decrease in accounts payable offset by depreciation
expenses.  This represents a net operating loss for the quarter combined with
an increase in current assets and an overall decrease in current liabilities.

Capital expenditures were $1.4 million during the three-month period ended
December 31, 1996 of which $929,000 was leased using the Company's nonrevolving
lease line of credit.  This lease line of credit expired in December and a new
line is currently being renegotiated.  Additionally, there were outstanding
commitments to purchase capital expenditures of approximately $1.5 million at
December 31, 1996.

Historically, the Company has generated cash through operations and financing
activities in an amount sufficient to fund its requirements.  The Company
believes that cash on hand, cash generated from operations and cash obtained
through borrowing or leasing arrangements will be sufficient to meet the
Company's working capital and capital expenditure requirements at least through
the end of fiscal 1997.  Any major change in the nature of the Company's
business, such as the acquisition of products, the design of products not
currently under development or the need for significant new capital
expenditures, could change the Company's capital requirements.  To the extent
the Company requires additional cash, there can be no assurance that the
company will be able to obtain such financing on terms favorable to the
Company, or at all.





<PAGE>   12
                          PART II - OTHER INFORMATION

ITEM 6. - EXHIBITS AND REPORTS ON FORM 8-K


(a)      The following exhibits are filed as part of this report:

         Exhibit 11.1 - Statement re Computation of Per Share Earnings (Loss)
         Exhibit 27.1 - Financial Data Schedule

(b)      Reports on Form 8-K:

         The Company filed no reports on Form 8-K during the quarter ended
December 31, 1996.





<PAGE>   13

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.

ELANTEC SEMICONDUCTOR, INC.
(Registrant)



Date: February 14, 1997                 By: /s/ Terrence W. Plette
                                            ----------------------------------
                                        Terrence W. Plette
                                        Chief Financial Officer





<PAGE>   14
                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
Exhibit                                                                     Page
                                                                            ----
<S>         <C>                                                             <C>
11.1        Statement re Computation of Per Share Earnings (Loss) . . . . .  15
27.1        Financial Data Schedule
</TABLE>