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                                                                    EXHIBIT 10.1

                           ALLEGRO MICROSYSTEMS, INC.

                             2001 STOCK OPTION PLAN

1.   PURPOSES OF PLAN. The purposes of the Allegro MicroSystems, Inc. 2001
     Incentive and Non-Qualified Stock Option Plan (the "Plan") are to provide
     to employees of and consultants to Allegro MicroSystems, Inc., (the
     "Corporation"), as well as employees of or consultants to subsidiary
     corporations which may currently exist or be formed or acquired in the
     future, an opportunity for investment in the Corporation's common stock
     (the "Shares"), as an inducement for such individuals to remain with the
     Corporation, and to encourage them to increase their efforts to make the
     Corporation's business more successful.

2.   EFFECTIVE DATE AND TERMINATION OF PLAN. The effective date of the Plan is
     May 30, 2001, the date on which the Plan was adopted by the Board of
     Directors of the Corporation (the "Board"). The Plan shall terminate on,
     and no option shall be granted hereunder, after May 29, 2011; provided,
     however, that the Board may at any time prior to that date terminate the
     Plan; and provided further that any option granted hereunder prior to the
     termination of the Plan shall remain exercisable in accordance with its
     terms as then in effect.

3.   ADMINISTRATION OF PLAN. The Plan shall be administered by the Board. The
     Board may, however, to the extent permissible under the Corporation's
     Certificate of Incorporation, By-laws and applicable law, delegate any of
     its functions under this Plan to a committee of the Board or any other
     committee. Wherever in this Plan the term "Board of Directors" or "Board"
     is used it shall be construed to mean such committee to the extent, if any,
     that the Board has delegated its functions to such committee. The acts of a
     majority of the members present at any meeting of the Board at which a
     quorum is present, or acts approved in writing by a majority of the entire
     Board, shall be the acts of the Board for purposes of the Plan. The Board
     in its discretion may do all things necessary to administer and interpret
     the Plan, such actions of the Board to be conclusive and binding on all
     persons. The Board may make such rules and regulations and establish such
     procedures for the administration of the Plan as it deems appropriate.

4.   ELIGIBILITY AND GRANT OF OPTIONS. Subject to the provisions of the Plan,
     the Board shall (i) authorize the granting of incentive stock options (as
     that term is defined in the Internal Revenue Code of 1986, as amended (the
     "Code")), non-qualified stock options, or a combination of incentive stock
     options and non-qualified stock options (hereinafter collectively referred
     to as "options" unless otherwise stated); (ii) determine and designate from
     time to time those employees of and consultants to the Corporation or any
     of its subsidiaries to whom options are to be granted; (iii) determine the
     number of Shares subject to each option; and (iv) determine the time or
     times when and the manner in which each option shall be exercisable, the
     duration of the exercise period, and other terms of the option. Only
     employees of the Corporation and its subsidiary corporations (as defined in
     Section 424(f) of the Code) shall be eligible to be awarded incentive stock
     options under the Plan. In determining the eligibility of an individual to
     receive an option, as well as in determining the number of Shares to be
     optioned to any individual, the Board shall consider the position and
     responsibilities of the employee or consultant, the nature and value to the
     Corporation or subsidiary of his or her services and accomplishments, his
     or her present and potential contribution to the success of the Corporation
     or subsidiary, and such other factors as the Board may deem relevant. A
     Director shall abstain from voting on the grant of any options to himself
     or herself or to his or her spouse, children, grandchildren or parents. The
     grant of each option shall be confirmed by a stock option agreement in a
     form prescribed by the Board (the "Stock Option Agreement") which shall be
     executed by the Corporation and the optionee as promptly as practicable
     after such grant. More than one option may be granted to an individual.

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     Each option granted pursuant to the Plan shall be presumed to provide by
     its terms that it is to be treated as a non-qualified stock option unless,
     at the date of grant, it is expressly designated as an incentive stock
     option in the Stock Option Agreement.

5.   NUMBER OF SHARES SUBJECT TO OPTIONS. Subject to adjustment as provided in
     paragraph 20, the aggregate number of Shares that may be delivered upon the
     exercise of options granted under the Plan shall be 3,750,000. No
     fractional Shares shall be delivered under the Plan. Shares as to which an
     option granted under the Plan shall remain unexercised at the expiration or
     termination thereof, and Shares subject to options which are cancelled, may
     be the subject of the grant of further options.

6.   OPTION PRICE. The option price per Share shall be determined in each case
     by the Board and shall not be less than one hundred percent (100%) of the
     fair market value thereof as determined by the Board by any reasonable
     method on the date the option is granted. In the case of an incentive stock
     option granted to a ten percent (10%) shareholder, the option price per
     Share shall be determined by the Board and shall not be less than one
     hundred ten percent (110%) of the fair market value thereof, as determined
     by the Board by any reasonable method on the date the option is granted.

7.   VESTING AND EXERCISABILITY. Options granted to a participant shall vest and
     be exercisable as follows:

     Except as otherwise provided in the Plan, each option shall be unvested and
     unexercisable until the fifth anniversary of the date of grant and shall
     become 100% vested and exercisable on such fifth anniversary; provided
     that, upon an initial public offering of the Corporation's stock, the
     portion of any outstanding option that is then unvested (or, if vested,
     unexercisable) shall become 100% vested and exercisable.

     Notwithstanding the foregoing, the Board or its designees shall have the
     right to grant options with any vesting and exercisability schedules,
     including immediate vesting and exercisability, and in the case of an
     option not immediately vested and exercisable, may accelerate vesting
     and/or exercisability at any time.

8.   OPTION TERM. The latest date on which an option may be exercised (the
     "Final Exercise Date") shall, unless an earlier date is specified by the
     Board, be the date that is ten (10) years after the date of grant or, in
     the case of an incentive stock option granted to a ten percent (10%)
     shareholder, five (5) years after the date of grant. Except as otherwise
     provided below, an option may be exercised only by the employee or
     consultant to whom it was granted and, subject to the rules set forth
     below, only if, at all times during the period beginning on the date of the
     grant of such option and ending with the date of exercise of such option,
     the optionee is an employee of or consultant to the Corporation or a
     subsidiary of the Corporation.

     (a)  Death, Disability, Involuntary Termination, or Retirement. Except as
          otherwise provided by the Board, in the case of an optionee whose
          employment (including in the term "employment," for purposes of this
          paragraph 8, the independent contractor service relationship of a
          non-employee consultant) with the Corporation and its subsidiaries
          terminates by reason of death, disability, involuntary termination, or
          retirement, (i) options that are exercisable but have not yet been
          exercised as of the date of termination of employment shall remain
          exercisable until the Final Exercise Date unless earlier exercised or
          terminated pursuant to paragraph 11, and (ii) options that are
          unvested shall vest (but shall not thereby become exercisable)
          immediately prior to such termination.


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          An option that vests pursuant to clause (ii) of the preceding sentence
          shall become exercisable only pursuant to paragraph 7 above (or
          pursuant to paragraph 11, if applicable) and, once exercisable, shall
          remain exercisable until the Final Exercise Date unless earlier
          exercised or terminated pursuant to paragraph 11. In the case of the
          optionee's death occurring on or after the date of the termination of
          employment, the option, to the extent exercisable in accordance with
          the foregoing, shall be exercisable by the optionee's executor or
          administrator or by the person or persons to whom the option is
          transferred by will or the applicable laws of descent and distribution
          (such person, persons, representative or representatives hereinafter
          referred to as "Successors of an Optionee").

     (b)  Voluntary Termination Prior to Retirement; Termination for Cause.
          Except as otherwise provided by the Board, in the case of an optionee
          who voluntarily terminates his or her employment with the Corporation
          and its subsidiaries prior to retirement, or of an optionee whose
          employment is terminated by the Corporation (or the subsidiary which
          employs the optionee) at any time for cause, all options which are
          unexercised (whether or not otherwise vested or exercisable) as of the
          date of termination of employment shall be forfeited immediately.

     (c)  Definitions. For purposes of the Plan, the following terms shall have
          the following meanings:

          1. "cause" shall mean (i) any act of personal dishonesty taken by the
          optionee in connection with his or her responsibilities as an employee
          or consultant and intended to result in substantial personal
          enrichment of the optionee; (ii) the conviction of or a plea of nolo
          contendere with respect to a felony; (iii) a willful act by the
          optionee which constitutes gross misconduct and which is injurious to
          the Corporation or any subsidiary of the Corporation; or (iv)
          following delivery to the optionee of a written demand for performance
          from the Corporation (or the subsidiary which employs the optionee)
          which describes the basis for the Corporation's (or subsidiary's)
          belief that the optionee has not substantially performed his or her
          duties, continued violations by the optionee of the optionee's
          obligations to the Corporation (or the subsidiary) which are
          demonstrably willful and deliberate on the optionee's part;

          2. "disability" shall mean total disability as defined in the
          Corporation's long-term disability plan;

          3. "involuntary termination" shall mean a termination of employment by
          the Corporation (or the subsidiary which employs the optionee) without
          cause (as defined above). In addition, to the extent the Board at the
          time of grant so provides in the Stock Option Agreement, the term
          "involuntary termination" shall also include a termination of
          employment by the optionee after one or more of the following
          resulting from an action by the Corporation or its subsidiaries or by
          a successor employer following a transaction described in paragraph
          11: (i) a significant reduction of the optionee's employment duties,
          authority or responsibilities, (ii) a substantial reduction without
          good business reasons, of the optionee's facilities and perquisites
          (including office space and location), (iii) a reduction of more than
          ten percent (10%) in the base salary of the optionee, (iv) a material
          reduction of the optionee's benefits, (v) the relocation of the
          optionee to a facility or a location more than thirty-five (35) miles
          from the optionee's then present location, or (vi) any act or set of
          facts or circumstances which would, under


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          Massachusetts case law or statute, constitute a constructive
          termination of the optionee; and

          4. "retirement" shall mean a voluntary termination of employment on or
          after the optionee's attainment of age 62; provided that at the time
          of the termination the optionee has provided at least fifteen (15)
          continuous years of service to the Corporation, Sprague Electric
          Company, or any subsidiary of either the Corporation or Sprague
          Electric Company.

9.   EXERCISE OF OPTIONS. An option that is exercisable may be exercised, and
     payment in full of the option price made, by an optionee only by written
     notice (in a form prescribed by the Board) to the Corporation specifying
     the number of Shares to be so purchased. Such notice shall state that the
     option price shall be paid in full in a manner acceptable to the Board,
     subject to the following:

     (a)  all payment will be by cash or check acceptable to the Board or,

     (b)  if so permitted by the Board at (in the case of a non-qualified stock
          option, at or after) the date of grant, through the delivery of Shares
          which have been outstanding for at least six months (unless the Board
          approves a shorter period) and which have a fair market value equal to
          the exercise price.

     As soon as practicable after receipt by the Corporation of such notice and
     of payment in full of the option price of all the Shares with respect to
     which an option has been exercised, the Shares shall be delivered to the
     optionee or to the Successors of an Optionee.

10.  NO RIGHTS TO CONTINUED EMPLOYMENT; NO RIGHTS AS SHAREHOLDER. Nothing in the
     Plan or in any option granted pursuant to the Plan shall confer on any
     individual any right to continue in the employ of the Corporation or any
     subsidiary or interfere in any way with the right of the Corporation or any
     subsidiary to terminate his or her employment at any time. Furthermore, the
     holder of an option granted under the Plan shall not have the rights of a
     shareholder with respect to such option except as to Shares actually
     transferred to the option holder upon exercise of the option.

11.  MERGER, ASSET SALE, AND CERTAIN OTHER TRANSACTIONS. In the event of a
     covered transaction in which there is an acquiring or surviving entity (the
     "Successor Company"), outstanding options may be assumed or substantially
     equivalent options may be substituted by the Successor Company or a parent
     or subsidiary thereof. A substitute award shall not be considered
     "substantially equivalent" unless, among other things, it preserves the
     intrinsic value of the original option (as reasonably determined by the
     Board) and provides for vesting and exercisability (including duration of
     the option) on terms that are not less favorable to the optionee or
     Successors of an Optionee, as the case may be, than the provisions relating
     to vesting and exercisability (including duration of the option) contained
     in the original option.

     If the Successor Company does not assume an outstanding option or
     substitute for it a substantially equivalent option, the option shall
     become fully vested and exercisable, including as to Shares for which it
     would not otherwise be exercisable immediately prior to the covered
     transaction. In such event the option shall become fully vested and
     exercisable, prior to the consummation of the covered transaction, on such
     terms (including the effective date of the acceleration of vesting and
     exercisability) as the Board shall reasonably determine to enable the


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     holder of the option, upon exercise, to participate in the covered
     transaction as a shareholder. Upon the consummation of the covered
     transaction the option shall terminate.

     For the purposes of the Plan, the term "covered transaction" shall mean any
     of (i) a consolidation, merger or other transaction in which the
     Corporation is not the surviving corporation or which results in the
     acquisition of all or substantially all of the Corporation's then
     outstanding common stock by a single person or entity or by a group of
     persons and/or entities acting in concert, (ii) a sale or transfer of all
     or substantially all the Corporation's assets, or (iii) a dissolution or
     liquidation of the Corporation.

12.  TAX WITHHOLDING. As a condition to the exercise of any option awarded under
     the Plan, the optionee shall (i) remit to the Corporation (or the
     subsidiary which employs the optionee), in cash, an amount sufficient to
     satisfy any federal, state, or local withholding tax requirements arising
     by reason of such exercise or make other arrangements satisfactory to the
     Corporation (or the subsidiary which employs the optionee) with regard to
     such taxes, and (ii) in the case of an incentive stock option, agree to
     inform the Corporation (or the subsidiary which employs the optionee)
     promptly of any disposition (within the meaning of Section 424(c) of the
     Code and the regulations thereunder) of Shares received upon exercise and,
     unless the Board otherwise determines, to give such security as the Board
     deems adequate to meet the potential liability of the Corporation (or
     subsidiary which employs the optionee) for the withholding of tax with
     respect to the later disposition of such Shares and to augment such
     security from time to time in any amount reasonably deemed necessary by the
     Board to preserve the adequacy of such security. If permitted by the Board,
     either at the time of the grant of the option or the time of exercise, the
     optionee may elect, at such time and in such manner as the Board may
     prescribe, to satisfy any withholding obligation by delivering to the
     Corporation Shares having a fair market value equal to such withholding
     obligation or by requesting that the Corporation withhold from the Shares
     to be delivered upon the exercise a number of Shares having a fair market
     value equal to such withholding obligations; provided, that no more than
     the minimum withholding required by law may be satisfied by the use of
     Shares as provided in this sentence.

13.  EXERCISE BY SUCCESSORS AND PAYMENT IN FULL. Notwithstanding anything herein
     to the contrary, the Corporation shall be under no obligation to deliver
     Shares pursuant to an exercise by a Successor Optionee until the
     Corporation is satisfied as to the authority of the person or persons
     exercising the option.

14.  NON-TRANSFERABILITY OF OPTION. Each incentive stock option, and, except as
     otherwise determined by the Board and set forth in the Stock Option
     Agreement, each non-qualified stock option granted under the Plan, shall by
     its terms be nontransferable by the optionee except by will or the laws of
     descent and distribution. If the Board makes a non-qualified stock option
     transferable, such option shall contain such additional terms and
     conditions, as the Board deems appropriate.

15.  OTHER TERMS OF OPTION. Options granted pursuant to the Plan shall contain
     such terms, provisions, and conditions not inconsistent herewith as shall
     be determined by the Board.

16.  REGISTRATION OF CERTIFICATES. Certificates representing Shares may be
     registered either in the name of the optionee or in the name or names of
     the Successors of an Optionee.

17.  LISTING AND REGISTRATION OF SHARES. The delivery of Shares upon exercise of
     an option shall be subject to compliance with (i) applicable federal and
     state laws and regulations, (ii) if the outstanding Shares are at the time
     of delivery listed on any stock exchange, the listing


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     requirements of such exchange, and (iii) Corporation's counsel's approval
     of all other legal matters in connection with the issue and delivery of
     such Shares. If at any time the Board shall determine, in its discretion,
     that the listing, registration, or qualification of any of the Shares
     subject to options under the Plan upon any securities exchange or under any
     state or federal law, or the consent or approval of any governmental
     regulatory body is necessary or desirable as a condition of or in
     connection with the granting of options or the purchase or issue of Shares
     thereunder, no further options may be granted and outstanding options may
     not be exercised in whole or in part unless and until such listing,
     registration, qualification, consent, or approval shall have been effected
     or obtained free of any conditions not acceptable to the Board. The Board
     shall have the authority to cause the Corporation at its expense to take
     any action related to the Plan which may be required in connection with
     such listing, registration, qualification, consent, or approval. The Board
     may require that any person exercising an option hereunder shall make such
     representations and agreements and furnish such information as it deems
     appropriate to assure compliance with the foregoing or any other applicable
     legal requirement.

18.  AMENDMENT. The Board may amend this Plan or any outstanding option for any
     purpose which may at the time be permitted by law; provided that, no such
     amendment shall adversely affect the rights of an optionee under any
     existing Stock Option Agreement without the consent of such optionee. In
     addition, no amendment may, without approval of the shareholders of the
     Corporation within twelve months before or after the date on which such
     amendment was adopted, (a) increase the total number of Shares which may be
     made subject of options granted under the Plan (subject to paragraph 20
     below), (b) change the manner of determining the option price, (c) change
     the criteria of determining which employees are eligible to receive
     options, (d) extend the period during which options may be granted or
     exercised, or (e) withdraw the administration of the Plan from the Board.

19.  INDEMNIFICATION AND EXCULPATION.

     (a)  To the fullest extent permitted by applicable law, each person who is
          or shall have been a member of the Board shall be indemnified and held
          harmless by the Corporation against and from any and all loss, cost,
          liability, or expense that may be imposed upon or reasonably incurred
          by him or her in his or her capacity as a member of the Board and in
          connection with or resulting from any claim, action, suit, or
          proceeding to which he or she may be or become a party or in which he
          or she may be or become involved by reason of any action taken or
          failure to act under the Plan and against and from any and all amounts
          paid by him or her in settlement thereof (with the Corporation's
          written approval) or paid by him or her in satisfaction of a judgment
          in any such action, suit, or proceeding, except a judgment in favor of
          the Corporation based upon a finding of his or her lack of good faith;
          subject, however, to the condition that upon the institution of any
          claim, action, suit, or proceeding against him or her, he or she shall
          in writing give the Corporation an opportunity, at its own expense, to
          handle and defend the same before he or she undertakes to handle and
          defend it on his or her own behalf. The foregoing right of
          indemnification shall not be exclusive of any other right to which
          such person may be entitled as a matter of law or otherwise, or any
          power that the Corporation may have to indemnify him or her or hold
          him or her harmless.

     (b)  Each member of the Board, and each officer and employee of the
          Corporation shall be fully justified in relying or acting in good
          faith upon any information furnished in connection with the
          administration of the Plan by any appropriate person or persons other
          than himself/herself. To the fullest extent permitted by applicable
          law, in no event shall any person who is or shall have been a member
          of the Board, or an officer or employee of


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          the Corporation be held liable for any determination made or other
          action taken or any omission to act in reliance upon any such
          information, or for any action (including the furnishing of
          information) taken or any failure to act, if taken or omitted in good
          faith.

20.  CHANGES IN CAPITAL STRUCTURE. In the event of a stock dividend, stock split
     or combination of shares, recapitalization or other change in the
     Corporation's capital structure, the Board will make appropriate
     adjustments to the maximum number of shares that may be delivered under the
     Plan, and will also make appropriate adjustments to the number and kind of
     shares of stock or securities subject to options then outstanding or
     subsequently granted, any exercise prices relating to options and any other
     provision of options affected by such change. The Board may also make
     adjustments of the type described in the preceding sentence to take into
     account distributions to common stockholders other than those provided for
     in paragraph 11 or the preceding sentence, or in any other event, if the
     Board determines that adjustments are appropriate to avoid distortion in
     the operation of the Plan and to preserve the value of options made
     hereunder.

21.  NOTICES. All notices under the Plan shall be in writing, and if to the
     Corporation, shall be delivered to the Treasurer of the Corporation or
     mailed to the Corporation's principal office, addressed to the attention of
     the Treasurer; and if to the optionee, shall be delivered personally or
     mailed to the optionee at the address appearing in the records of the
     Corporation (or a subsidiary). Such addresses may be changed at any time by
     written notice to the other party.

22.  CORPORATION'S OPTION. The Corporation shall have, in addition to any rights
     it may have under paragraph 23 below, the right, but not the obligation, to
     purchase from any optionee (or his or her successor, assignee or
     transferee) Shares issued upon the exercise of options granted hereunder
     (the "Call Option").

     (a)  Exercise of the Call Option. The Company may exercise the Call Option
          by delivery of written notice to the optionee, which notice shall
          state the number of Shares to be purchased, the exercise price per
          Share (subject to subparagraph (b) below), and the payment method
          (subject to subparagraph (c) below).

     (b)  Exercise Price. The exercise price per Share of the Call Option shall
          be equal to the fair market value of such Share at the time of
          exercise, as determined by the Corporation in good faith.

     (c)  Payment. The payment election shall be, at the election of the
          Corporation, by cash (including by check), by a cancellation of any
          outstanding indebtedness of the optionee to the Corporation, or by a
          combination thereof.

     (d)  Termination of Call Option. This Call Option shall terminate at the
          completion of an initial public offering of the Corporation's stock or
          upon the consummation of a merger, consolidation, corporate
          reorganization, or similar transaction in which the Shares are
          converted into or exchanged for securities of the acquiror or
          surviving entity or of an affiliate thereof that are part of a class
          of securities that are publicly traded.

23.  CORPORATION'S RIGHT OF FIRST REFUSAL

     Before any Shares held by optionee (or a successor, assignee or transferee,
     any such person being sometimes referred to herein as the "Holder") may be
     sold or otherwise transferred (including transfer by gift or operation of
     law), the Corporation shall have a right of first refusal to purchase


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     the Shares on the terms and conditions set forth in this paragraph 23 (the
     "Right of First Refusal"). Any attempt to sell, transfer, or hypothecate
     Shares prior to an initial public offering without notice (as defined
     below) to the Corporation shall be null and void.

     (a)  Notice of Proposed Transfer. The Holder of the Shares shall deliver to
          the Corporation a written notice (the "Notice") stating: (i) the
          Holder's bona fide intention to sell or otherwise transfer such
          Shares; (ii) the name of each proposed purchaser or other transferee
          ("Proposed Transferee"); (iii) the number of Shares to be transferred
          to each Proposed Transferee; and (iv) the bona fide cash price or
          other consideration for which the Holder proposes to transfer the
          Shares (the "Offered Price"), and the Holder shall offer the Shares at
          the Offered Price to the Corporation.

     (b)  Exercise of Right of First Refusal. At any time within thirty (30)
          days after receipt of the Notice, the Corporation may, by giving
          written notice to the Holder, elect to purchase all, but not less than
          all, of the Shares proposed to be transferred to any one or more of
          the Proposed Transferees, at the purchase price determined in
          accordance with subparagraph (c) below.

     (c)  Purchase Price. The purchase price ("Purchase Price") for the Shares
          purchased by the Corporation under this paragraph 23 shall be the
          Offered Price. If the Offered Price includes consideration other than
          cash, the cash equivalent value of the non-cash consideration shall be
          determined by the Board in good faith.

     (d)  Payment. Payment of the Purchase Price shall be made within thirty
          (30) days after receipt of the Notice or in the manner and at the
          times set forth in the Notice, at the option of the Corporation, in
          cash (including by check), by cancellation of all or a portion of any
          outstanding indebtedness of the Holder to the Corporation, or by any
          combination thereof.

     (e)  Holder's Right to Transfer. If all of the Shares proposed in the
          Notice to be transferred to a given Proposed Transferee are not
          purchased by the Corporation as provided in this paragraph 23, then
          the Holder may sell or otherwise transfer such Shares to that Proposed
          Transferee at the Offered Price or at a higher price, provided that
          such sale or other transfer is consummated with one hundred and twenty
          (120) days after the date of the Notice and provided further that any
          such sale or other transfer is effected in accordance with any
          applicable securities laws and the Proposed Transferee agrees in
          writing that the provisions of this paragraph 23 shall continue to
          apply to the Shares in the hands of such Proposed Transferee. If the
          Shares described in the Notice are not transferred to the Proposed
          Transferee within such period, a new Notice shall be given to the
          Corporation, and the Corporation shall again be offered the Right of
          First Refusal before any Shares held by the Holder may be sold or
          otherwise transferred.

     (f)  Exception for Certain Transfers at Death or to Permitted Transferees.
          Anything to the contrary contained in this paragraph 23
          notwithstanding, the transfer of any or all of the Shares during the
          optionee's lifetime or on the optionee's death by will or intestacy to
          the optionee's immediate family or a trust, family limited
          partnership, or similar entity for the benefit of the optionee's
          immediate family shall be exempt from the provisions of this paragraph
          23. "Immediate Family" as used herein shall mean spouse, lineal
          descendant, father, mother, brother or sister. In such case, the
          transferee or other recipient shall receive and hold the Shares so
          transferred subject to the provisions of this paragraph 23,


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          and there shall be no further transfer of such Shares except in
          accordance with the terms of this paragraph 23.


     (g)  Termination of Right of First Refusal. This Right of First Refusal
          shall terminate at the completion of an initial public offering of the
          Corporation's stock or upon the consummation of a merger,
          consolidation, corporate reorganization, or similar transaction in
          which the Shares are converted into or exchanged for securities of the
          acquiror or surviving entity or of an affiliate thereof that are part
          of a class of securities that are publicly traded.


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                         Optionee's Name:    ((FIRST_NAME)) ((LAST_NAME))
                         Optionee's Address: ((STREET1)) ((STREET2)) ((STREET3))
                                             ((CITY)), ((STATE)) ((ZipCode))
                                             ((COUNTRY))

                           ALLEGRO MICROSYSTEMS, INC.

                             2001 STOCK OPTION PLAN

                        INCENTIVE STOCK OPTION AGREEMENT

     Pursuant to this Stock Option Agreement, Allegro MicroSystems, Inc. (the
"Corporation") grants to ((FIRST_NAME)) ((LAST_NAME)), an employee of the
Corporation or its subsidiaries (the "Optionee"), an incentive stock option on
the terms provided herein. Unless otherwise defined herein, all initially
capitalized terms used herein shall have the meaning specified in the Allegro
MicroSystems, Inc. 2001 Stock Option Plan (the "Plan").

I.   Grant of Incentive Stock Option.

     Effective ((Grant_Date)) (the "Date of Grant"), the Corporation hereby
grants the Optionee an option (the "Option") to purchase, in whole or in part,
on the terms provided herein, a total of ((Number_of_Options)) shares of common
stock of the Corporation (the "Shares") at an exercise price per Share equal to
((GRANT_PRICE)) (the "Exercise Price"), which is not less than the fair market
value of the Shares on the Date of Grant. The Final Exercise Date (as that term
is defined in the Plan) is ((ExpirationDate)). It is intended that the Option
shall be, to the maximum extent possible consistent with section 422 of the
Internal Revenue Code of 1986 (as from time to time amended, the "Code"), an
incentive stock option as defined in section 422 of the Code.

II.  Vesting and Exercisability.

     The Option shall become vested and shall be exercisable in accordance with
the following rules:

     A.   Except as hereinafter provided, the Option shall become vested and
          exercisable only upon the earlier to occur of (i) the fifth (5th)
          anniversary of the Date of Grant or (ii) an initial public offering of
          the common stock of the Corporation, and prior thereto shall be
          neither vested nor exercisable.

     B.   Upon termination of the Optionee's employment with the Corporation and
          its subsidiaries by reason of death, disability, involuntary
          termination (other than for cause), or retirement, any portion of the
          Option that is then outstanding but unvested shall become fully vested
          immediately prior to such termination of employment. Any portion of
          the Option that becomes vested by application of the immediately
          preceding sentence shall, notwithstanding such accelerated vesting,
          become exercisable only in accordance with subparagraph A. above. The
          terms "disability" and "retirement" shall have the meanings specified
          in the Plan.

     C.   Once exercisable, the Option shall remain exercisable until the Final
          Exercise Date, subject to possible earlier termination pursuant to
          paragraph 11 of the Plan or to forfeiture pursuant to Paragraph III of
          this Stock Option Agreement.

ISO

((EMPLID))

<PAGE>

     D.   For purposes of the Paragraph II, "involuntary termination (other than
          for cause)" shall mean a termination of employment by the Corporation
          and its subsidiaries without cause (as defined in the Plan), or a
          termination of employment by the Optionee after one or more of the
          following resulting from an action by the Corporation or its
          subsidiaries or by a successor employer following a covered
          transaction (as defined in the Plan): (i) a significant reduction of
          the Optionee's employment duties, authority or responsibilities, (ii)
          a substantial reduction, without good business reasons, of the
          Optionee's facilities and perquisites (including office space and
          location), (iii) a reduction of more than ten percent (10%) in the
          base salary of the Optionee, (iv) a material reduction of the
          Optionee's benefits, (v) the relocation of the Optionee to a facility
          or a location more than thirty-five (35) miles from the Optionee's
          then present location, or (vi) any act or set of facts or
          circumstances which would, under Massachusetts case law or statute,
          constitute a constructive termination of the Optionee.

III. Forfeiture.

     In the event that the Optionee voluntarily terminates his or her employment
with the Corporation and its subsidiaries prior to retirement (as defined in the
Plan), or the Corporation and its subsidiaries terminates the Optionee's
employment at any time for cause (as defined in the Plan), any then outstanding
portions of the Option shall be immediately forfeited.

IV.  Exercise of Option.

     1.   Method of Exercise. The Option, to the extent exercisable, may be
          exercised through the Final Exercise Date only in accordance with the
          provisions of the Plan and this Stock Option Agreement. The Optionee
          (or, following the death of the Optionee, the Successor Optionee) may
          elect to exercise the Option by delivering to the Corporation's Human
          Resources Department a written exercise notice in the form to be
          provided by the Corporation's Human Resources Department (the
          "Exercise Notice"). The Exercise Notice shall be signed by the
          Optionee (or, following the death of the Optionee, the Successor
          Optionee), state the number of Shares in respect of which the Option
          is being exercised (the "Exercised Shares"), and include such other
          representations and agreements as may be required by the Corporation
          pursuant to the provisions of the Plan. The Exercise Notice shall be
          accompanied by payment of the aggregate Exercise Price as to all
          Exercised Shares. In the event that the Option is exercised by a
          Successor Optionee, the Corporation shall have no obligation to
          deliver Shares hereunder unless and until it is satisfied as to the
          authority of the person or persons exercising the Option. No Shares
          shall be issued or delivered pursuant to the exercise of the Option
          unless such issuance and exercise complies with all applicable laws.

     2.   Method of Payment. Payment of the aggregate Exercise Price shall be by
          any of the following, or a combination thereof, at the election of the
          Optionee.

          (a)  cash;

          (b)  check acceptable to the Board of Directors ("the Board") of the
               Corporation; or

          (c)  through the deliver of Shares which have been outstanding for at
               least six months and which on a per Exercised Share basis have a
               fair market value equal to the Exercise Price.

ISO


                                        2

<PAGE>

V.   Notice of Disposition.

     The person exercising the Option shall notify the Corporation when making
any disposition of the Shares acquired upon exercise of the Option, whether by
sale, gift, or otherwise.

VI.  Tax Withholding.

     As a condition to the exercise of the Option, the Optionee shall (i) remit
to the Corporation or to such other person as the Corporation may designate, in
cash, an amount sufficient to satisfy any federal, state, or local withholding
tax requirements arising by reason of such exercise or make other arrangements
satisfactory to the Corporation with respect to such taxes, and (ii) give such
security, if any, as the Board deems adequate to meet any potential liability of
the Corporation and its subsidiaries for the withholding of tax with respect to
the later disposition of such Shares and to augment such security from time to
time in any amount reasonably deemed necessary by the Board to preserve the
adequacy of such security. To the extent permitted by the Board, the Optionee
may elect, at such time and in such manner as the Board may prescribe, to
satisfy any withholding obligation by delivering to the Corporation Shares
having a fair market value equal to such withholding obligation or by requesting
that the Corporation withhold from the Shares to be delivered upon the exercise
a number of Shares having a fair market value equal to such withholding
obligations; provided, that no more than the minimum withholding required by law
may be satisfied by the use of Shares as provided in this sentence.

VII. Non-Transferability of Option.

     The Option may not be transferred in any manner otherwise than by will or
by the laws of descent or distribution and may be exercised during the lifetime
of the Optionee only by the Optionee. The terms of the Plan and this Option
Agreement shall be binding upon the executors, administrators, heirs, successors
and assigns of the Optionee.

VIII. Restrictions on Transfer of Shares.

     Optionee agrees not to sell, transfer or otherwise dispose of any Shares
acquired upon exercise of the Option during the period beginning upon the
effective date of a registration statement under the Securities Act of 1933, as
amended, restating to a firm commitment underwritten public offering of the
Shares and ending on the date specified by the representative of the
underwriters of such offering, such period not to exceed 180 days.

IX.  Corporation's Right to Repurchase Shares.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation will have the
right, but not the obligation, to purchase from the Optionee any Shares issued
on the exercise of the Option on the terms and conditions set forth in paragraph
22 of the Plan.

X.   Corporation's Right of First Refusal.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class

ISO


                                       3

<PAGE>

of securities that are publicly traded, the Corporation shall have a right of
first refusal to purchase any Shares acquired upon exercise of this Option on
the terms and conditions set forth in paragraph 23 of the Plan.

XI.  Entire Agreement; Governing Law.

     The Plan is incorporated herein by reference. The Plan and this Stock
Option Agreement constitute the entire agreement of the parties with respect to
the subject matter hereof and supersede in their entirety all prior undertakings
and agreements of the Corporation and Optionee with respect to the subject
matter hereof, and may not be modified adversely to the Optionee's interest
except by means of a writing signed by the Corporation and Optionee. This
Agreement is governed by the internal substantive laws, but not the choice of
law rules, of Massachusetts.

XII. No Guarantee of Continued Service.

     Optionee acknowledges and agrees that this Stock Option Agreement, the
transactions contemplated hereunder and the vesting and exercisability
provisions set forth herein do not constitute an express or implied promise of
employment for any period or at all and shall not interfere with Optionee's
right or the Corporation's right to terminate Optionee's employment at any time,
with or without cause.

     IN WITNESS WHEREOF, the Optionee and the Corporation have caused this
instrument to be executed ((Grant_Date)). The Corporation has caused this
instrument to be executed by a duly authorized officer.

     By signature of the Optionee and the signature of the Corporation's officer
below, the Optionee and the Corporation agree that each has received a copy of
the Plan, that each has had an opportunity to read the Plan prior to entering
into this Stock Option Agreement, and that the Option is granted under and
governed by the terms and conditions of the Plan and this Stock Option
Agreement. Optionee hereby agrees to accept as binding, conclusive and final all
decisions or interpretations of the Board upon any questions relating to the
Plan and this Stock Option Agreement. Optionee further agrees to notify the
Corporation upon any change in the address indicated below.

OPTIONEE                                ALLEGRO MICROSYSTEMS, INC.


-------------------------------------   ----------------------------------------
((FIRST_NAME)) ((LAST_NAME))            Marybeth Perry
((STREET1)) ((STREET2)) ((STREET3))     Vice President of Human Resources
((CITY)), ((STATE)) ((ZipCode))
((COUNTRY))

ISO


                                       4

<PAGE>

                             Optionee's Name:    ((FirstName)) ((LastName))
                             Optionee's Address: ((Address1)) ((Address2))
                                                 ((Address3))
                                                 ((City)), ((StateID)) ((Zip__))
                                                 ((Country))

                           ALLEGRO MICROSYSTEMS, INC.

                             2001 STOCK OPTION PLAN

                        INCENTIVE STOCK OPTION AGREEMENT

     Pursuant to this Stock Option Agreement, Allegro MicroSystems, Inc. (the
"Corporation") grants to ((FirstName)) ((LastName)), an employee of the
Corporation or its subsidiaries (the "Optionee"), an incentive stock option on
the terms provided herein. Unless otherwise defined herein, all initially
capitalized terms used herein shall have the meaning specified in the Allegro
MicroSystems, Inc. 2001 Stock Option Plan (the "Plan").

I.   Grant of Incentive Stock Option.

     Effective ((Date_of_Grant)) (the "Date of Grant"), the Corporation hereby
grants the Optionee an option ((the "Option") to purchase, in whole or in part,
on the terms provided herein, a total of ((Number_of_Options)) shares of common
stock of the Corporation (the "Shares") at an exercise price per Share equal to
((Exercise_Price)) (the "Exercise Price"), which is not less than the fair
market value of the Shares on the Date of Grant. The Final Exercise Date (as
that term is defined in the Plan) is ((Date_of_Expiration)). It is intended that
the Option shall be, to the maximum extent possible consistent with section 422
of the Internal Revenue Code of 1986 (as from time to time amended, the "Code"),
an incentive stock option as defined in section 422 of the Code.

II.  Vesting and Exercisability.

     The Option shall become vested and shall be exercisable in accordance with
the following rules:

     A.   Except as hereinafter provided, the Option shall become vested and
          exercisable only upon the earlier to occur of (i) the fifth (5th)
          anniversary of the Date of Grant or (ii) an initial public offering of
          the common stock of the Corporation, and prior thereto shall be
          neither vested nor exercisable.

     B.   Upon termination of the Optionee's employment with the Corporation and
          its subsidiaries by reason of death, disability, involuntary
          termination (other than for cause), or retirement, any portion of the
          Option that is then outstanding but unvested shall become fully vested
          immediately prior to such termination of employment. Any portion of
          the Option that becomes vested by application of the immediately
          preceding sentence shall, notwithstanding such accelerated vesting,
          become exercisable only in accordance with subparagraph A. above. The
          terms "disability" and "retirement" shall have the meanings specified
          in the Plan.

     C.   Once exercisable, the Option shall remain exercisable until the Final
          Exercise Date, subject to possible earlier termination pursuant to
          paragraph 11 of the Plan or to forfeiture pursuant to Paragraph III of
          this Stock Option Agreement.

                                                                             ISO
<PAGE>

     D.   For purposes of the Paragraph II, "involuntary termination (other than
          for cause)" shall mean a termination of employment by the Corporation
          and its subsidiaries without cause (as defined in the Plan).

III. Forfeiture.

     In the event that the Optionee voluntarily terminates his or her employment
with the Corporation and its subsidiaries prior to retirement (as defined in the
Plan), or the Corporation and its subsidiaries terminates the Optionee's
employment at any time for cause (as defined in the Plan), any then outstanding
portions of the Option shall be immediately forfeited.

IV.  Exercise of Option.

     1.   Method of Exercise. The Option, to the extent exercisable, may be
          exercised through the Final Exercise Date only in accordance with the
          provisions of the Plan and this Stock Option Agreement. The Optionee
          (or, following the death of the Optionee, the Successor Optionee) may
          elect to exercise the Option by delivering to the Corporation's Human
          Resources Department a written exercise notice in the form to be
          provided by the Corporation's Human Resources Department (the
          "Exercise Notice"). The Exercise Notice shall be signed by the
          Optionee (or, following the death of the Optionee, the Successor
          Optionee), state the number of Shares in respect of which the Option
          is being exercised (the "Exercised Shares"), and include such other
          representations and agreements as may be required by the Corporation
          pursuant to the provisions of the Plan. The Exercise Notice shall be
          accompanied by payment of the aggregate Exercise Price as to all
          Exercised Shares. In the event that the Option is exercised by a
          Successor Optionee, the Corporation shall have no obligation to
          deliver Shares hereunder unless and until it is satisfied as to the
          authority of the person or persons exercising the Option. No Shares
          shall be issued or delivered pursuant to the exercise of the Option
          unless such issuance and exercise complies with all applicable laws.

     2.   Method of Payment. Payment of the aggregate Exercise Price shall be by
          any of the following, or a combination thereof, at the election of the
          Optionee.

          (a)  cash;

          (b)  check acceptable to the Board of Directors ("the Board") of the
               Corporation; or

          (c)  through the deliver of Shares which have been outstanding for at
               least six months and which on a per Exercised Share basis have a
               fair market value equal to the Exercise Price.

V.   Notice of Disposition.

     The person exercising the Option shall notify the Corporation when making
any disposition of the Shares acquired upon exercise of the Option, whether by
sale, gift, or otherwise.

VI.  Tax Withholding.

     As a condition to the exercise of the Option, the Optionee shall (i) remit
to the Corporation or to such other person as the Corporation may designate, in
cash, an amount sufficient to satisfy any federal, state, or local withholding
tax requirements arising by reason of such exercise or make other

                                                                             ISO


                                        2

<PAGE>

arrangements satisfactory to the Corporation with respect to such taxes, and
(ii) give such security, if any, as the Board deems adequate to meet any
potential liability of the Corporation and its subsidiaries for the withholding
of tax with respect to the later disposition of such Shares and to augment such
security from time to time in any amount reasonably deemed necessary by the
Board to preserve the adequacy of such security. To the extent permitted by the
Board, the Optionee may elect, at such time and in such manner as the Board may
prescribe, to satisfy any withholding obligation by delivering to the
Corporation Shares having a fair market value equal to such withholding
obligation or by requesting that the Corporation withhold from the Shares to be
delivered upon the exercise a number of Shares having a fair market value equal
to such withholding obligations; provided, that no more than the minimum
withholding required by law may be satisfied by the use of Shares as provided in
this sentence.

VII. Non-Transferability of Option.

     The Option may not be transferred in any manner otherwise than by will or
by the laws of descent or distribution and may be exercised during the lifetime
of the Optionee only by the Optionee. The terms of the Plan and this Option
Agreement shall be binding upon the executors, administrators, heirs, successors
and assigns of the Optionee.

VIII. Restrictions on Transfer of Shares.

     Optionee agrees not to sell, transfer or otherwise dispose of any Shares
acquired upon exercise of the Option during the period beginning upon the
effective date of a registration statement under the Securities Act of 1933, as
amended, restating to a firm commitment underwritten public offering of the
Shares and ending on the date specified by the representative of the
underwriters of such offering, such period not to exceed 180 days.

IX.  Corporation's Right to Repurchase Shares.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation will have the
right, but not the obligation, to purchase from the Optionee any Shares issued
on the exercise of the Option on the terms and conditions set forth in paragraph
22 of the Plan.

X.   Corporation's Right of First Refusal.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation shall have a
right of first refusal to purchase any Shares acquired upon exercise of this
Option on the terms and conditions set forth in paragraph 23 of the Plan.

XI.  Entire agreement; Governing Law.

     The Plan is incorporated herein by reference. The Plan and this Stock
Option Agreement constitute the entire agreement of the parties with respect to
the subject matter hereof and supersede in their entirety all prior undertakings
and agreements of the Corporation and Optionee with respect to the subject
matter hereof, and may not be modified adversely to the Optionee's interest
except by means of a

                                                                             ISO


                                       3

<PAGE>

writing signed by the Corporation and Optionee. This Agreement is governed by
the internal substantive laws, but not the choice of law rules, of
Massachusetts.

XII. No Guarantee of Continued Service.

     Optionee acknowledges and agrees that this Stock Option Agreement, the
transactions contemplated hereunder and the vesting and exercisability
provisions set forth herein do not constitute an express or implied promise of
employment for any period or at all and shall not interfere with Optionee's
right or the Corporation's right to terminate Optionee's employment at any time,
with or without cause.

     IN WITNESS WHEREOF, the Optionee and the Corporation have caused this
instrument to be executed ((Date_of_Grant)). The Corporation has caused this
instrument to be executed by a duly authorized officer.

     By signature of the Optionee and the signature of the Corporation's officer
below, the Optionee and the Corporation agree that each has received a copy of
the Plan, that each has had an opportunity to read the Plan prior to entering
into this Stock Option Agreement, and that the Option is granted under and
governed by the terms and conditions of the Plan and this Stock Option
Agreement. Optionee hereby agrees to accept as binding, conclusive and final all
decisions or interpretations of the Board upon any questions relating to the
Plan and this Stock Option Agreement. Optionee further agrees to notify the
Corporation upon any change in the address indicated below.

OPTIONEE                                ALLEGRO MICROSYSTEMS, INC.


-------------------------------------   ----------------------------------------
((FirstName)) ((LastName))              Marybeth Perry
((Address1)) ((Address2))               Vice President of Human Resources
((City)), ((StateID)) ((Zip_))
((Country))

                                                                             ISO


                                       4

<PAGE>

                           Optionee's Name:    ((FirstName)) ((LastName))
                           Optionee's Address: ((Address1)) ((Address2))
                                               ((City)), ((StateID)) ((ZipCode))
                                               ((Country))

                           ALLEGRO MICROSYSTEMS, INC.

                             2001 STOCK OPTION PLAN

                       NONSTATUTORY STOCK OPTION AGREEMENT

     Pursuant to this Stock Option Agreement, Allegro MicroSystems, Inc. (the
"Corporation") grants to ((FirstName)) ((LastName)), (the "Optionee"), a
nonstatutory stock option on the terms provided herein. Unless otherwise defined
herein, all initially capitalized terms used herein shall have the meaning
specified in the Allegro MicroSystems, Inc. 2001 Stock Option Plan (the "Plan").

I.   Grant of Nonstatutory Stock Option.

     Effective ((Date_of_Grant)) (the "Date of Grant"), the Corporation hereby
grants to the Optionee an option (the "Option") to purchase, in whole or in
part, on the terms provided herein, a total of ((Number_of_Options)) shares of
common stock of the Corporation (the "Shares") at an exercise price per Share
equal ((Exercise_Price)) (the "Exercise Price"), which is not less than the fair
market value of the Shares on the Date of Grant. The Final Exercise Date (as
that term is defined in the Plan) is ((Date_of_Expiration)). The Option is
intended to be a nonstatutory option, that is, an option that does not qualify
as an incentive stock option as defined in section 422 of the United States
Internal Revenue Code of 1986 (as from time to time amended, the "Code").

II.  Vesting and Exercisability.

     The Option shall become vested and shall be exercisable in accordance with
the following rules:

     A.   Except as hereinafter provided, the Option shall become vested and
          exercisable only upon the earlier to occur of (i) the fifth (5th)
          anniversary of the Date of Grant or (ii) an initial public offering of
          the common stock of the Corporation, and prior thereto shall be
          neither vested nor exercisable.

     B.   Upon termination of the Optionee's employment with the Corporation and
          its subsidiaries by reason of death, disability, involuntary
          termination (other than for cause), or retirement, any portion of the
          Option that is then outstanding but unvested shall become fully vested
          immediately prior to such termination of employment. Any portion of
          the Option that becomes vested by application of the immediately
          preceding sentence shall, notwithstanding such accelerated vesting,
          become exercisable only in accordance with subparagraph A. above. The
          terms "disability" and "retirement" shall have the meanings specified
          in the Plan.

     C.   Once exercisable, the Option shall remain exercisable until the Final
          Exercise Date, subject to possible earlier termination pursuant to
          paragraph 11 of the Plan or to forfeiture pursuant to Paragraph III of
          this Stock Option Agreement.

     D.   For purposes of this Paragraph II, "involuntary termination (other
          than for cause)" shall mean a termination of employment by the
          Corporation and its subsidiaries without cause

NSO

<PAGE>

          (as defined in the Plan), or a termination of employment by the
          Optionee after one or more of the following resulting from an action
          by the Corporation or its subsidiaries or by a successor employer
          following a covered transaction (as defined in the Plan): (i) a
          significant reduction of the Optionee's employment duties, authority
          or responsibilities, (ii) a substantial reduction, without good
          business reasons, of the Optionee's facilities and perquisites
          (including office space and location), (iii) a reduction of more than
          ten percent (10%) in the base salary of the Optionee, (iv) a material
          reduction of the Optionee's benefits, (v) the relocation of the
          Optionee to a facility or a location more than thirty-five (35) miles
          from the Optionee's then present location, or (vi) any act or set of
          facts or circumstances which would, under Massachusetts case law or
          statute, constitute a constructive termination of the Optionee.

III. Forfeiture.

     In the event that the Optionee voluntarily terminates his or her employment
with the Corporation and its subsidiaries prior to retirement (as defined in the
Plan), or the Corporation and its subsidiaries terminates the Optionee's
employment at any time for cause (as defined in the Plan), any then outstanding
portions of the Option shall be immediately forfeited.

IV.  Exercise of Option.

     1.   Method of Exercise. The Option, to the extent exercisable, may be
          exercised through the Final Exercise Date only in accordance with the
          provisions of the Plan and this Stock Option Agreement. The Optionee
          (or, following the death of the Optionee, the Successor Optionee) may
          elect to exercise the Option by delivering to the Corporation's Human
          Resources Department a written exercise notice in the form to be
          provided by the Corporation's Human Resources Department (the
          "Exercise Notice"). The Exercise Notice shall be signed by the
          Optionee (or, following the death of the Optionee, the Successor
          Optionee), state the number of Shares in respect of which the Option
          is being exercised (the "Exercised Shares"), and include such other
          representations and agreements as may be required by the Corporation
          pursuant to the provisions of the Plan. The Exercise Notice shall be
          accompanied by payment of the aggregate Exercise Price as to all
          Exercised Shares. In the event that the Option is exercised by a
          Successor Optionee, the Corporation shall have no obligation to
          deliver Shares hereunder unless and until it is satisfied as to the
          authority of the person or persons exercising the Option. No Shares
          shall be issued or delivered pursuant to the exercise of the Option
          unless such issuance and exercise complies with all applicable laws.

     2.   Method of Payment. Payment of the aggregate Exercise Price shall be by
          any of the following, or a combination thereof, at the election of the
          Optionee:

          (a)  cash;

          (b)  check acceptable to the Board of Directors ("the Board") of the
               Corporation; or

          (c)  to the extent so provided by the Board through the delivery of
               Shares which have been outstanding for at least six months and
               which on a per Exercised Share basis have a fair market value
               equal to the Exercise Price.

NSO


                                       2

<PAGE>

V.   Notice of Disposition.

     The person exercising the Option shall notify the Corporation when making
any disposition of the Shares acquired upon exercise of the Option, whether by
sale, gift, or otherwise.

VI.  Tax Withholding.

     As a condition to the exercise of the Option, the Optionee shall remit to
the Corporation or to such other person as the Corporation may designate, in
cash, an amount sufficient to satisfy any federal, state, or local withholding
tax requirements arising by reason of such exercise or make other arrangements
satisfactory to the Corporation with respect to such taxes. To the extent
permitted by the Board, the Optionee may elect, at such time and in such manner
as the Board may prescribe, to satisfy any withholding obligation by delivering
to the Corporation Shares having a fair market value equal to such withholding
obligation or by requesting that the Corporation withhold from the Shares to be
delivered upon the exercise a number of Shares having a fair market value equal
to such withholding obligations; provided, that no more than the minimum
withholding required by law may be satisfied by the use of Shares as provided in
this sentence.

VII. Non-Transferability of Option.

     The Option may not be transferred in any manner otherwise than by will or
by the laws of descent or distribution and may be exercised during the lifetime
of the Optionee only by the Optionee. The terms of the Plan and this Option
Agreement shall be binding upon the executors, administrators, heirs, successors
and assigns of the Optionee.

VIII. Restrictions on Transfer of Shares.

     Optionee agrees not to sell, transfer or otherwise dispose of any Shares
acquired upon exercise of the Option during the period beginning upon the
effective date of a registration statement under the Securities Act of 1933, as
amended, relating to a firm commitment underwritten public offering of the
Shares and ending on the date specified by the representative of the
underwriters of such offering, such period not to exceed 180 days.

IX.  Corporation's Right to Repurchase Shares.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation will have the
right, but not the obligation, to purchase from the Optionee any Shares issued
on the exercise of the Option on the terms and conditions set forth in paragraph
22 of the Plan.

X.   Corporation's Right of First Refusal.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation shall have a
right of first refusal to purchase any Shares acquired upon exercise of this
Option on the terms and conditions set forth in paragraph 23 of the Plan.

NSO


                                       3

<PAGE>

XI.  Entire Agreement; Governing Law.

     The Plan is incorporated herein by reference. The Plan and this Stock
Option Agreement constitute the entire agreement of the parties with respect to
the subject matter hereof and supersede in their entirety all prior undertakings
and agreements of the Corporation and Optionee with respect to the subject
matter hereof, and may not be modified adversely to the Optionee's interest
except by means of a writing signed by the Corporation and Optionee. This
Agreement is governed by the internal substantive laws, but not the choice of
law rules, of Massachusetts.

XII. No Guarantee as to Tax Consequences.

     The Optionee should consult a personal tax adviser before exercising the
Option or disposing of the Shares acquired upon exercise of the Option. Tax laws
vary from country to country and may change following the Date of Grant. The
Corporation makes no guarantees whatsoever with regard to any national, federal,
state, or local tax consequences relating to the grant or exercise of the
Option, or to the later disposition of Shares acquired upon exercise of the
Option.

XIII. No Guarantee of Continued Service.

     Optionee acknowledges and agrees that this Stock Option Agreement, the
transactions contemplated hereunder and the vesting and exercisability
provisions set forth herein do not constitute an express or implied promise of
employment of a continuing service relationship for any period or at all and
shall not interfere with Optionee's right or the Corporation's right to
terminate Optionee's employment or other service relationship at any time, with
or without cause.

     IN WITNESS WHEREOF, the Optionee and the Corporation have caused this
instrument to be executed on ((Date_of_Grant)). The Corporation has caused this
instrument to be executed by a duly authorized officer.

     By signature of the Optionee and the signature of the Corporation's officer
below, the Optionee and the Corporation agree that each has received a copy of
the Plan, that each has had an opportunity to read the Plan prior to entering
into this Stock Option Agreement, and that the Option is granted under and
governed by the terms and conditions of the Plan and this Stock Option
Agreement. Optionee hereby agrees to accept as binding, conclusive and final all
decisions or interpretations of the Board upon any questions relating to the
Plan and this Stock Option Agreement. Optionee further agrees to notify the
Corporation upon any change in the address indicated below.

OPTIONEE                                ALLEGRO MICROSYSTEMS, INC.


-------------------------------------   ----------------------------------------
((FirstName)) ((LastName))              Marybeth Perry
((Address1)) ((Address2))               Vice President of Human Resources
((City)), ((StateID)) ((ZipCode))
((Country))

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<PAGE>

                 Optionee's Name:    ((FIRST_NAME)) ((LAST_NAME))
                 Optionee's Address: ((STREET1)) ((STREET2))
                                     ((STREET3)) ((CITY)), ((STATE)) ((ZipCode))
                                     ((COUNTRY))

                           ALLEGRO MICROSYSTEMS, INC.

                             2001 STOCK OPTION PLAN

                       NONSTATUTORY STOCK OPTION AGREEMENT

     Pursuant to this Stock Option Agreement, Allegro MicroSystems, Inc. (the
"Corporation") grants to ((FIRST_NAME)) ((LAST_NAME)), (the "Optionee"), a
nonstatutory stock option on the terms provided herein. Unless otherwise defined
herein, all initially capitalized terms used herein shall have the meaning
specified in the Allegro MicroSystems, Inc. 2001 Stock Option Plan (the "Plan").

I.   Grant of Nonstatutory Stock Option.

     Effective ((Grant_Date)) (the "Date of Grant"), the Corporation hereby
grants to the Optionee an option (the "Option") to purchase, in whole or in
part, on the terms provided herein, a total of ((Number_of_Options)) shares of
common stock of the Corporation (the "Shares") at an exercise price per Share
equal ((GRANT_PRICE)) (the "Exercise Price"), which is not less than the fair
market value of the Shares on the Date of Grant. The Final Exercise Date (as
that term is defined in the Plan) is (ExpirationDate). The Option is intended to
be a nonstatutory option, that is, an option that does not qualify as an
incentive stock option as defined in section 422 of the United States Internal
Revenue Code of 1986 (as from time to time amended, the "Code").

II.  Vesting and Exercisability.

     The Option shall become vested and shall be exercisable in accordance with
the following rules:

     A.   Except as hereinafter provided, the Option shall become vested and
          exercisable only upon the earlier to occur of (i) the fifth (5th)
          anniversary of the Date of Grant or (ii) an initial public offering of
          the common stock of the Corporation, and prior thereto shall be
          neither vested nor exercisable.

     B.   Upon termination of the Optionee's employment with the Corporation and
          its subsidiaries by reason of death, disability, involuntary
          termination (other than for cause), or retirement, any portion of the
          Option that is then outstanding but unvested shall become fully vested
          immediately prior to such termination of employment. Any portion of
          the Option that becomes vested by application of the immediately
          preceding sentence shall, notwithstanding such accelerated vesting,
          become exercisable only in accordance with subparagraph A. above. The
          terms "disability" and "retirement" shall have the meanings specified
          in the Plan.

     C.   Once exercisable, the Option shall remain exercisable until the Final
          Exercise Date, subject to possible earlier termination pursuant to
          paragraph 11 of the Plan or to forfeiture pursuant to Paragraph III of
          this Stock Option Agreement.

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<PAGE>

     D.   For purposes of this Paragraph II, "involuntary termination (other
          than for cause)" shall mean a termination of employment by the
          Corporation and its subsidiaries without cause (as defined in the
          Plan).

III. Forfeiture.

     In the event that the Optionee voluntarily terminates his or her employment
with the Corporation and its subsidiaries prior to retirement (as defined in the
Plan), or the Corporation and its subsidiaries terminates the Optionee's
employment at any time for cause (as defined in the Plan), any then outstanding
portions of the Option shall be immediately forfeited.

IV.  Exercise of Option.

     1.   Method of Exercise. The Option, to the extent exercisable, may be
          exercised through the Final Exercise Date only in accordance with the
          provisions of the Plan and this Stock Option Agreement. The Optionee
          (or, following the death of the Optionee, the Successor Optionee) may
          elect to exercise the Option by delivering to the Corporation's Human
          Resources Department a written exercise notice in the form to be
          provided by the Corporation's Human Resources Department (the
          "Exercise Notice"). The Exercise Notice shall be signed by the
          Optionee (or, following the death of the Optionee, the Successor
          Optionee), state the number of Shares in respect of which the Option
          is being exercised (the "Exercised Shares"), and include such other
          representations and agreements as may be required by the Corporation
          pursuant to the provisions of the Plan. The Exercise Notice shall be
          accompanied by payment of the aggregate Exercise Price as to all
          Exercised Shares. In the event that the Option is exercised by a
          Successor Optionee, the Corporation shall have no obligation to
          deliver Shares hereunder unless and until it is satisfied as to the
          authority of the person or persons exercising the Option. No Shares
          shall be issued or delivered pursuant to the exercise of the Option
          unless such issuance and exercise complies with all applicable laws.

     2.   Method of Payment. Payment of the aggregate Exercise Price shall be by
          any of the following, or a combination thereof, at the election of the
          Optionee:

          (a)  cash;

          (b)  check acceptable to the Board of Directors ("the Board") of the
               Corporation; or

          (c)  to the extent so provided by the Board through the delivery of
               Shares which have been outstanding for at least six months and
               which on a per Exercised Share basis have a fair market value
               equal to the Exercise Price.

V.   Notice of Disposition.

     The person exercising the Option shall notify the Corporation when making
any disposition of the Shares acquired upon exercise of the Option, whether by
sale, gift, or otherwise.

VI.  Tax Withholding.

     As a condition to the exercise of the Option, the Optionee shall remit to
the Corporation or to such other person as the Corporation may designate, in
cash, an amount sufficient to satisfy any federal,

                                                                             NSO


                                       2


<PAGE>

state, or local withholding tax requirements arising by reason of such exercise
or make other arrangements satisfactory to the Corporation with respect to such
taxes. To the extent permitted by the Board, the Optionee may elect, at such
time and in such manner as the Board may prescribe, to satisfy any withholding
obligation by delivering to the Corporation Shares having a fair market value
equal to such withholding obligation or by requesting that the Corporation
withhold from the Shares to be delivered upon the exercise a number of Shares
having a fair market value equal to such withholding obligations; provided, that
no more than the minimum withholding required by law may be satisfied by the use
of Shares as provided in this sentence.

VII. Non-Transferability of Option.

     The Option may not be transferred in any manner otherwise than by will or
by the laws of descent or distribution and may be exercised during the lifetime
of the Optionee only by the Optionee. The terms of the Plan and this Option
Agreement shall be binding upon the executors, administrators, heirs, successors
and assigns of the Optionee.

VIII. Restrictions on Transfer of Shares.

     Optionee agrees not to sell, transfer or otherwise dispose of any Shares
acquired upon exercise of the Option during the period beginning upon the
effective date of a registration statement under the Securities Act of 1933, as
amended, relating to a firm commitment underwritten public offering of the
Shares and ending on the date specified by the representative of the
underwriters of such offering, such period not to exceed 180 days.

IX.  Corporation's Right to Repurchase Shares.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation will have the
right, but not the obligation, to purchase from the Optionee any Shares issued
on the exercise of the Option on the terms and conditions set forth in paragraph
22 of the Plan.

X.   Corporation's Right of First Refusal.

     Until the completion of an initial public offering of the Shares or the
consummation of a merger, consolidation, corporate reorganization, or similar
transaction in which the Shares are converted into or exchanged for securities
of the acquirer or surviving entity or of an affiliate thereof that are part of
a class of securities that are publicly traded, the Corporation shall have a
right of first refusal to purchase any Shares acquired upon exercise of this
Option on the terms and conditions set forth in paragraph 23 of the Plan.

XI.  Entire Agreement; Governing Law.

     The Plan is incorporated herein by reference. The Plan and this Stock
Option Agreement constitute the entire agreement of the parties with respect to
the subject matter hereof and supersede in their entirety all prior undertakings
and agreements of the Corporation and Optionee with respect to the subject
matter hereof, and may not be modified adversely to the Optionee's interest
except by means of a writing signed by the Corporation and Optionee. This
Agreement is governed by the internal substantive laws, but not the choice of
law rules, of Massachusetts.

                                                                             NSO


                                       3

<PAGE>

XII. No Guarantee as to Tax Consequences.

     The Optionee should consult a personal tax adviser before exercising the
Option or disposing of the Shares acquired upon exercise of the Option. Tax laws
vary from country to country and may change following the Date of Grant. The
Corporation makes no guarantees whatsoever with regard to any national, federal,
state, or local tax consequences relating to the grant or exercise of the
Option, or to the later disposition of Shares acquired upon exercise of the
Option.

XIII. No Guarantee of Continued Service.

     Optionee acknowledges and agrees that this Stock Option Agreement, the
transactions contemplated hereunder and the vesting and exercisability
provisions set forth herein do not constitute an express or implied promise of
employment of a continuing service relationship for any period or at all and
shall not interfere with Optionee's right or the Corporation's right to
terminate Optionee's employment or other service relationship at any time, with
or without cause.

     IN WITNESS WHEREOF, the Optionee and the Corporation have caused this
instrument to be executed on ((Grant_Date)). The Corporation has caused this
instrument to be executed by a duly authorized officer.

     By signature of the Optionee and the signature of the Corporation's officer
below, the Optionee and the Corporation agree that each has received a copy of
the Plan, that each has had an opportunity to read the Plan prior to entering
into this Stock Option Agreement, and that the Option is granted under and
governed by the terms and conditions of the Plan and this Stock Option
Agreement. Optionee hereby agrees to accept as binding, conclusive and final all
decisions or interpretations of the Board upon any questions relating to the
Plan and this Stock Option Agreement. Optionee further agrees to notify the
Corporation upon any change in the address indicated below.

OPTIONEE                                     ALLEGRO MICROSYSTEMS, INC.


-------------------------------------        -----------------------------------
((FIRST_NAME)) ((LAST_NAME))                 Marybeth Perry
((STREET1)) ((STREET2))                      Vice President of Human Resources
((STREET3)) ((CITY)) ((STATE)) ((ZipCode))
((COUNTRY))

                                                                             NSO


                                        4