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                                                                   EXHIBIT 10.55


                               ALTERA CORPORATION

                       RESTRICTED STOCK PURCHASE AGREEMENT

               THIS RESTRICTED STOCK PURCHASE AGREEMENT (this "Agreement") is
entered into as of ____________, 2000, by and between Altera Corporation, a
Delaware corporation (the "Company"), and Michael Jacobs ("Recipient").


                               W I T N E S S E T H

               WHEREAS, Recipient is a newly hired employee of the Company;

               WHEREAS, the Company believes that Recipient will be a valuable
contributor to the Company and has determined that it would be in the interests
of the Company and its stockholders to sell the Shares (as defined below)
provided for in this Agreement to Recipient (i) as compensation for the
compensation and benefits that Recipient relinquished when Recipient left his
previous employer and joined the Company and (ii) as an incentive for continued
service with the Company and increased achievements in the future by Recipient;
and

               WHEREAS, on January 11, 2000, the Compensation Committee of the
Board of Directors of the Company approved the issuance of the Shares (as
defined below) to Recipient for a consideration of $0.001 per share and this
Agreement memorializes such issuance;

               NOW, THEREFORE, in consideration of the mutual covenants
hereinafter set forth, the parties to this Agreement hereby agree as follows:

                                A G R E E M E N T

               1. Restricted Stock Purchase.

                    (a) Contemporaneously with the execution of this Agreement,
the Company will issue and sell to Recipient twenty-five thousand (25,000)
shares of Common Stock, $0.001 par value per share, of the Company (the "Stock")
for a consideration of $0.001 per share ("Purchase Price Per Share") for a total
purchase price of Twenty-Five Dollars ($25) (the "Total Purchase Price").
Payment for the Stock in the amount of the Total Purchase Price shall be made to
the Company upon execution of this Agreement. Such payment shall be made in the
form of a check. The Stock certificate(s) evidencing the Stock will be retained
by the Company, accompanied by (i) blank stock powers executed by Recipient and
Recipient's spouse, if any, and (ii) a consent of spouse (if any), for the
period during which the Stock constitutes Restricted Stock (as defined below)
pursuant to the terms of Sections 2 and 3 hereof.

                    (b) All shares of Stock issued hereunder shall be deemed
issued to Recipient as fully paid and nonassessable shares, and Recipient shall
have all rights of a stockholder with respect thereto, including the right to
vote, receive dividends (including stock dividends), participate in stock splits
or other recapitalizations, and exchange such shares in a merger, consolidation
or other reorganization. The term "Stock," in addition to the shares purchased
pursuant to this Agreement, also refers to all securities received in
replacement of the



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Stock, as a stock dividend or as a result of any stock split, recapitalization,
merger, reorganization, exchange or the like, and all new, substituted or
additional securities or other properties to which Recipient is entitled by
reason of Recipient's ownership of the Stock.

               2. Restrictions.

                    (a) No Stock issued to the Recipient hereunder shall be
sold, transferred by gift, pledged, hypothecated, or otherwise transferred or
disposed of by the Recipient prior to the date when the Recipient shall become
vested in such Stock pursuant to Section 3 or 4 hereof, and such Stock shall
constitute "Restricted Stock" until such date. Any attempt to transfer Stock in
violation of this Section 2 shall be null and void and shall be disregarded by
the Company.

                    (b) In addition, Restricted Stock shall be subject to a
repurchase option in favor of the Company (the "Repurchase Option"). The
Repurchase Option shall be subject to the following terms and conditions:

                         (i) If Recipient voluntarily terminates his employment
with the Company ("Voluntary Termination") or if the Company terminates
Recipient's employment with Cause (as defined below) ("Termination with Cause"),
the Company shall, upon the date of such termination, have an irrevocable,
exclusive option for a period of ninety (90) days from such date to repurchase
any or all Restricted Stock from Recipient or any person receiving the
Restricted Stock by operation of law of other involuntary transfer, at the
original Purchase Price Per Share for the Restricted Stock. The Repurchase
Option may be assigned by the Company to any third person or entity.

                         (ii) Notwithstanding the foregoing, the Repurchase
Option shall lapse with respect to all of the unvested shares of Stock (as
described in Section 3 hereof) if the Company terminates Recipient's employment
without Cause. For purposes of this Agreement, "Cause" shall exist if, in the
reasonable judgment of the Chief Executive Officer of the Company, (i) the
Recipient commits fraud, theft, or embezzlement against the Company or any of
its subsidiaries; (ii) the Recipient commits a felony; (iii) the Recipient
compromises any trade secret or violates Recipient's confidentiality obligations
to the Company; (iv) the Recipient fails to devote his full business time and
effort to the performance of his duties to the Company; (v) the Recipient
engages in any grossly negligent act or willful misconduct in the scope of his
duties to the Company; or (vi) the Recipient receives a "needs improvement"
rating in an annual performance evaluation.

                         (iii) The Repurchase Option shall be exercised by
written notice by the Company or its assignee to Recipient or his executor and,
at the Company's or its assignee's option, by delivery to the Recipient or his
executor, with such notice, of (A) a check in the amount of the Purchase Price
Per Share for the Restricted Stock being repurchased, (B) in the event that
Recipient is indebted to the Company or its assignee, by cancellation by the
Company or its assignee of an amount of such indebtedness equal to the Purchase
Price Per Share for the Restricted Stock being repurchased, or (C) by a
combination of (A) and (B) so that the combined payment and cancellation of
indebtedness equals such Purchase Price Per Share. Upon delivery by the Company
or its assignee of such notice and payment of the Purchase Price Per Share, the
Company or its assignee shall become the legal and beneficial owner of the
Restricted Stock being repurchased and all rights and interest therein or
related thereto, and the



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Company shall have the right to transfer to its or its assignee's own name the
number of shares of Restricted Stock being repurchased by the Company or its
assignee, without further action by Recipient.

                    (c) For purposes of facilitating the enforcement of the
provisions of this Section 2, Recipient agrees that (i) the stock certificate(s)
evidencing the Stock will be retained by the Company to be held in escrow for so
long as such Stock remains Restricted Stock, (ii) Recipient shall promptly
deliver to the Secretary or Assistant Secretary of the Company, or their
designee, (A) an Assignment Separate from Certificate, in substantially the form
of that attached hereto as Exhibit A, executed in blank by Recipient and
Recipient's spouse (if any) with respect to each stock certificate evidencing
the Stock, and (B) if Recipient is married, a Consent of Spouse in substantially
the form of that attached hereto as Exhibit B, and (iii) the Company shall have
the authority to take all such actions and to effectuate all such transfers
and/or releases as may be necessary or appropriate to accomplish the objectives
of this Agreement in accordance with the terms hereof. Recipient hereby
acknowledges that the appointment of the Secretary or Assistant Secretary of the
Company (or their designee) as the escrow holder hereunder with the stated
authorities is a material inducement to the Company to make this Agreement and
that such appointment is coupled with an interest and is accordingly
irrevocable. Recipient agrees that such escrow holder shall not be liable to any
party hereto (or to any other party) for any actions or omissions unless such
escrow holder is grossly negligent relative thereto. The escrow holder may rely
upon any letter, notice or other document executed by any signature purported to
be genuine and may resign at any time.

               3. Vesting. For purposes of this Agreement, the term "vest" shall
mean with respect to any share of the Stock that such share is no longer
Restricted Stock subject to the restrictions on transfer set forth in Section 2
and that such share is released from the Repurchase Option. If Recipient would
become vested in any fraction of a share of Stock on any date, such fractional
share shall not vest and shall remain Restricted Stock until the Recipient
becomes vested in the entire share. The shares of Stock subject to this
Agreement shall, subject to Section 2, vest with respect to one-fourth of the
Stock on each anniversary of Recipient's hire date of January 11, 2000, such
that all the shares of Stock shall vest on the fourth anniversary of such date.

               4. Withholding of Taxes. Recipient shall provide the Company with
a copy of any timely election made pursuant to Section 83(b) of the Internal
Revenue Code or similar provision of state law (collectively, an "83(b)
Election"), a form of which election is attached hereto as Exhibit C. If
Recipient makes a timely 83(b) Election, Recipient shall immediately pay the
Company the amount necessary to satisfy any applicable federal, state, and local
income and employment tax withholding requirements. If Recipient does not make a
timely 83(b) Election, Recipient shall, either at the time that the restrictions
lapse under this Agreement or at the time withholding is otherwise required by
any applicable law, pay the Company the amount necessary to satisfy any
applicable federal, state, and local income and employment tax withholding
requirements. If, upon written request by the Company, Recipient fails to pay
the Company such amount in a timely manner, the Company shall have the right to
deduct such amount from any sum(s) due Recipient from Company and shall also
have the right to sell a sufficient number of shares of the Stock to satisfy
such tax obligation.



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               5. Additional Securities. Any securities received as the result
of ownership of Restricted Stock (hereinafter called "Additional Securities"),
including, without limitation, warrants, options and securities received as a
stock dividend or stock split, or as a result of a recapitalization or
reorganization, shall be retained by the Company in the same manner and subject
to the same conditions as the Restricted Stock with respect to which they were
issued. Recipient shall be entitled to direct the Company to exercise any
warrant or option received as Additional Securities upon supplying the funds
necessary to do so, in which event the securities so purchased shall constitute
Additional Securities, but the Recipient may not direct the Company to sell any
such warrant or option. If Additional Securities consist of a convertible
security, Recipient may exercise any conversion right, and any securities so
acquired shall be deemed Additional Securities. Additional Securities shall be
subject to the provisions of Sections 2 and 3 above in the same manner as the
Restricted Stock.

               6. Legends; Stop Transfer.

                    (a) All certificates for shares of the Stock shall bear
substantially the following legends:

               THE SHARES REPRESENTED BY THIS CERTIFICATE ARE RESTRICTED BY THE
               TERMS OF THAT CERTAIN RESTRICTED STOCK PURCHASE AGREEMENT BETWEEN
               THE COMPANY AND THE NAMED STOCKHOLDER. THE SHARES REPRESENTED BY
               THIS CERTIFICATE MAY BE TRANSFERRED ONLY IN ACCORDANCE WITH SUCH
               AGREEMENT, A COPY OF WHICH IS ON FILE WITH THE SECRETARY OF THE
               COMPANY.

                    (b) The certificates for shares of the Stock shall also bear
any other legends required by applicable state corporate or securities laws.

                    (c) In addition, the Company shall make a notation regarding
the restrictions on transfer of the Stock in its stockbooks, and shares of the
Stock shall be transferred on the books of the Company only if transferred or
sold pursuant to an effective registration statement under the Securities Act of
1933, as amended (the "1933 Act") covering such shares.

               7. NO EFFECT ON TERMS OF EMPLOYMENT. THIS AGREEMENT SHALL NOT
CONFER UPON RECIPIENT ANY RIGHT WITH RESPECT TO CONTINUATION OF RECIPIENT'S
EMPLOYMENT WITH THE COMPANY, NOR SHALL IT INTERFERE IN ANY WAY WITH THE RIGHT OF
RECIPIENT OR THE COMPANY TO TERMINATE RECIPIENT'S EMPLOYMENT WITH THE COMPANY AT
ANY TIME FOR ANY REASON WITH OR WITHOUT CAUSE OR CHANGE THE TERMS OF EMPLOYMENT
OF RECIPIENT.

               8. California Law. This Agreement is to be construed in
accordance with and governed by the internal laws of the State of California as
permitted by Section 1646.5 of the California Civil Code (or any similar
successor provision) without giving effect to any choice of



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law rule that would cause the application of the laws of any jurisdiction other
than the internal laws of the State of California to the rights and duties of
the parties.

               9. Notice. Any notice required to be given under the terms of
this Agreement shall be addressed to the Company in care of its Secretary at the
office of the Company at 101 Innovation Drive, San Jose, CA 95134, and any
notice to be given to Recipient shall be addressed to him at the address given
by Recipient beneath his signature to this Agreement, or such other address as
either party to this Agreement may hereafter designate in writing to the other.
Any such notice shall be deemed to have been duly given when enclosed in a
properly sealed envelope or wrapper addressed as aforesaid, registered or
certified and deposited (postage or registration or certification fee prepaid)
in a post office or branch post office regularly maintained by the United
States.

               10.Successors. This Agreement shall be binding upon and inure to
the benefit of any successor or successors of the Company. Where the context
permits, "Recipient" as used in this Agreement shall include Recipient's
executor, administrator or other legal representative or the person or persons
to whom Recipient's rights pass by will or the applicable laws of descent and
distribution.

               11.Severability. If any provisions of this Agreement is
determined by any court or arbitrator of competent jurisdiction to be invalid,
illegal or unenforceable in any respect, such provision will be enforced to the
maximum extent possible given the intent of the parties hereto. If such clause
or provision cannot be so enforced, such provision shall be stricken from this
Agreement and the remainder of this Agreement shall be enforced as if such
invalid, illegal or unenforceable clause or provision had (to the extent not
enforceable) never been contained in this Agreement. Notwithstanding the
foregoing, if the value of this Agreement based upon the substantial benefit of
the bargain for any party is materially impaired, as determined by such party in
its sole discretion, than this Agreement will not be enforceable against such
affected party and both parties agree to renegotiate such provision(s) in good
faith.

               12.Amendment and Waiver. This Agreement may be amended only by a
written agreement executed by each of the parties hereto. No amendment of or
waiver of, or modification of any obligation under this Agreement will be
enforceable unless set forth in a writing signed by the party against which
enforcement is sought. Any amendment effected in accordance with this Section 12
will be binding upon all parties hereto and each of their respective successors
and assigns. No delay or failure to require performance of any provision of this
Agreement shall constitute a waiver of that provision as to that or any other
instance. No waiver granted under this Agreement as to any one provision herein
shall constitute a subsequent waiver of such provision or of any other provision
herein, nor shall it constitute the waiver of any performance other than the
actual performance specifically waived.

               13.Entire Agreement. This Agreement and the Exhibits attached
hereto constitute the entire agreement and understanding of the parties with
respect to the subject matter of this Agreement, and supercede all prior
understandings and agreements, whether oral or written, between or among the
parties hereto with respect to the specific subject matter hereof.



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        IN WITNESS WHEREOF, the parties hereto have duly executed this
Restricted Stock Purchase Agreement as of the date first above written.


ALTERA CORPORATION,                       RECIPIENT:
a Delaware corporation

By:__________________________________     ______________________________________
                                          Michael Jacobs

Name:________________________________
                                          Address:______________________________

Title:_______________________________             ______________________________






             [SIGNATURE PAGE TO RESTRICTED STOCK PURCHASE AGREEMENT]



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                                    EXHIBIT A

                      ASSIGNMENT SEPARATE FROM CERTIFICATE


               FOR VALUE RECEIVED and pursuant to that certain Restricted Stock
Purchase Agreement between the undersigned ("Recipient") and Altera Corporation,
Inc. dated ____________, 2000 (the "Agreement"), Recipient hereby sells, assigns
and transfers unto _______________ _________________ (_________) shares of
Common Stock of Altera Corporation standing in Recipient's name on the books of
said corporation represented by Certificate No. ____ herewith and does hereby
irrevocably constitute and appoint ______________________________ to transfer
said stock on the books of the within-named corporation with full power of
substitution in the premises. THIS ASSIGNMENT MAY ONLY BE USED AS AUTHORIZED BY
THE AGREEMENT AND THE EXHIBITS THERETO.




Dated:  ________________, 20___        By:______________________________________
                                                 Michael Jacobs

                                       By:______________________________________
                                                 [Spouse, if any]


Instruction: Please do not fill in any blanks other than the signature line. The
purpose of this assignment is to enable the Company to exercise its repurchase
option set forth in the Agreement without requiring additional signatures on the
part of Recipient.



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                                    EXHIBIT B

                                 SPOUSE CONSENT


        The undersigned spouse of Michael Jacobs (the "Purchaser") has read,
understands and hereby approves all the terms and conditions of the Restricted
Stock Purchase Agreement dated_______________ (the "Agreement"), by and between
Purchaser and Altera Corporation, a Delaware corporation (the "Company"),
pursuant to which Purchaser has purchased twenty-five thousand (25,000) shares
of the Company's Common Stock, $0.001 par value per share (the "Shares").

        In consideration of the Company granting my spouse the right to purchase
the Shares under the Agreement, I hereby agree to be irrevocably bound by all
the terms and conditions of the Agreement (including but not limited to the
Company's Repurchase Option contained therein) and further agree that any
community property interest I may have in the Shares will be similarly bound by
the Agreement.

        I hereby appoint Purchaser as my attorney-in-fact, to act in my name,
place and stead with respect to any amendment of the Agreement and with respect
to the making and filing of an election under Internal Revenue Code Section
83(b) in connection with the purchase of the Shares.

Dated:____________________


                                       _________________________________________
                                            Signature of Spouse [Sign Here]


                                       _________________________________________
                                            Name of Spouse [Please Print]


                                            ____ Check this line if you do not
                                            have a spouse.


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                                    EXHIBIT C

                       ELECTION UNDER SECTION 83(b) OF THE
                              INTERNAL REVENUE CODE


The undersigned Taxpayer hereby elects, pursuant to Section 83(b) of the
Internal Revenue Code, as amended, to include in gross income for the Taxpayer's
current taxable year the excess, if any, of the fair market value of the
property described below at the time of transfer over the amount paid for such
property, as compensation for services.

1.      TAXPAYER'S NAME:            _________________________

        TAXPAYER'S ADDRESS:         _________________________



        SOCIAL SECURITY NUMBER:     _________________________

2.      The property with respect to which the election is made is described as
        follows: _____________ shares of Common Stock, $0.001 par value per
        share, of Altera Corporation, a Delaware corporation (the "Company"),
        which is Taxpayer's employer or the corporation for whom the Taxpayer
        performs services.

3.      The date on which the shares were transferred was _______________ and
        this election is made for calendar year 200_.

4.      The shares are subject to the following restrictions: The Company may
        repurchase all or a portion of the shares at the Taxpayer's original
        purchase price under certain conditions at the time of Taxpayer's
        termination of employment or services.

5.      The fair market value of the shares (without regard to restrictions
        other than restrictions which by their terms will never lapse) was
        $______ per share at the time of transfer.

6.      The amount paid for such shares was $_____ per share.

7.      The Taxpayer has submitted a copy of this statement to the Company.

THIS ELECTION MUST BE FILED WITH THE INTERNAL REVENUE SERVICE ("IRS"), AT THE
OFFICE WHERE THE TAXPAYER FILES ANNUAL INCOME TAX RETURNS, WITHIN 30 DAYS AFTER
THE DATE OF TRANSFER OF THE PROPERTY, AND MUST ALSO BE FILED WITH THE TAXPAYER'S
INCOME TAX RETURNS FOR THE CALENDAR YEAR. THE ELECTION CANNOT BE REVOKED WITHOUT
THE CONSENT OF THE IRS.


Dated:______________________________     _______________________________________
                                            Taxpayer's Signature