UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                                (Amendment No. __1__ )*


                          VOLTERRA SEMICONDUCTOR CORP
--------------------------------------------------------------------------------
                                (Name of Issuer)


                                 Common Stock
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                   928708106
--------------------------------------------------------------------------------
                                 (CUSIP Number)



                              November 30, 2005
--------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

         [ X ]    Rule 13d-1(b)

         [   ]   Rule 13d-1(c)

         [   ]   Rule 13d-1(d)


*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).





                                  SCHEDULE 13G

CUSIP No.         928708106

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          1.   Names of Reporting Persons.  I.R.S.  Identification Nos. of above
               persons (entities only).
               AMVESCAP PLC
               INVESCO Private Capital, Inc.
               INVESCO Institutional (N.A.), Inc.

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          2.   Check the Appropriate Box if a Member of a Group (see
               Instructions)
               (a)
               (b)

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          3.   SEC Use Only  _______________________________________________

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          4.   Citizenship or Place of Organization
               AMVESCAP PLC: England
               INVESCO Private Capital, Inc.: Delaware
               INVESCO Institutional (N.A.), Inc.: Delaware

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                                    5.      Sole Voting Power 924,738: Such
                                            shares are held by the following
                                            entities in the respective amounts
                                            listed: INVESCO Private Capital, Inc.
                                            923,814; INVESCO Institutional (N.A.), 
                                            Inc. 924

Number of Shares           --------------------------------------------------------------------------------------------------
Beneficially Owned
by Each Reporting                   6.      Shared Voting Power       ______-0-______
Person With
                           --------------------------------------------------------------------------------------------------

                                    7.      Sole Dispositive Power 924,738:
                                            Such shares are held by the
                                            following entities in the respective
                                            amounts listed: INVESCO Private Capital, Inc.
                                            923,814; INVESCO Institutional (N.A.), 
                                            Inc. 924

                           --------------------------------------------------------------------------------------------------

                                    8.      Shared Dispositive Power     ______-0-______


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          9.   Aggregate  Amount  Beneficially  Owned by Each  Reporting  Person
               924,738

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          10.  Check if the Aggregate  Amount in Row (9) Excludes Certain Shares
               (See Instructions) N/A


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          11.  Percent of Class Represented by Amount in Row (9)        3.9%
                                                                        ----


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          12.  Type of Reporting Person (See  Instructions)
               IA, HC. See Items 2 and 3 of this statement.







                                  SCHEDULE 13G


               
Item 1(a)         Name of Issuer:
                  VOLTERRA SEMICONDUCTOR CORP


Item 1(b)         Address of Issuer's Principal Executive Offices:
                  3839 Spinnaker Court
                  Fremont, CA 94538


Item 2(a)         Name of Person Filing:
                  AMVESCAP PLC

                  In accordance with Securities and Exchange Commission Release
                  No. 34-39538 (January 12, 1998), this statement on Schedule
                  13G or amendment thereto is being filed by AMVESCAP PLC
                  ("AMVESCAP"), a U.K. entity, on behalf of itself and its
                  subsidiaries listed in Item 4 of the cover of this statement.
                  AMVESCAP through such subsidiaries provides investment
                  management services to institutional and individual investors
                  worldwide.

                  Executive officers and directors of AMVESCAP or its
                  subsidiaries may beneficially own shares of the securities of
                  the issuer to which this statement relates (the "Shares"), and
                  such Shares are not reported in this statement. AMVESCAP and
                  its subsidiaries disclaim beneficial ownership of Shares
                  beneficially owned by any of their executive officers and
                  directors. Each of AMVESCAP's direct and indirect subsidiaries
                  also disclaim beneficial ownership of Shares beneficially
                  owned by AMVESCAP and any other subsidiary.


Item 2(b)         Address of Principal Business Office:
                  30 Finsbury Square
                  London EC2A 1AG
                  England


Item 2(c)         Citizenship:
                  See the response to Item 2(a) of this statement.


Item 2(d)         Title of Class of Securities:
                  Common Stock, $.01 par value per share


Item 2(e)         CUSIP Number:
                  928708106


Item 3            If this statement is filed pursuant to ss240.13d-1(b) or
                  240.13d-2(b) or (c), check whether the person filing is a:

          (e) [x] An investment adviser in accordance with section 240.13d-1(b)(1)(ii)(E)

          (g) [x] A parent holding company or control person in accordance with section 240.13d-1(b)(1)(ii)(G)

                  As noted in Item 2 above, AMVESCAP is making this filing on
                  behalf of its subsidiaries listed herein. Each of these
                  entities is either an investment adviser registered with the
                  United States Securities and Exchange Commission under Section 203
                  of the Investment Advisers Act of 1940, as amended, or under
                  similar laws of other jurisdictions. AMVESCAP is a holding
                  company.









               
Item 4            Ownership:
                  Please see responses to Items 5-8 on the cover of this
                  statement, which are incorporated herein by reference.


Item 5            Ownership of Five Percent or Less of a Class:

                  If this statement is being filed to report the fact that as of the date hereof the reporting
                  person has ceased to be the beneficial owner of more than five percent of the class of securities,
                  check the following                                                             [ X ]

Item 6            Ownership of More than Five Percent on Behalf of Another Person:
                  N/A


Item 7            Identification and Classification of the Subsidiary Which Acquired the Security Being Reported
                  on By the Parent Holding Company:
                  Please see Item 3 of this statement, which is incorporated herein by reference.


Item 8            Identification and Classification of Members of the Group:
                  N/A


Item 9            Notice of Dissolution of a Group:
                  N/A


Item 10           Certification:
                  By signing below I certify that, to the best of my knowledge
                  and belief, the securities referred to above were acquired and
                  are held in the ordinary course of business and were not
                  acquired and are not held for the purpose of or with the
                  effect of changing or influencing the control of the issuer of
                  the securities and were not acquired and are not held in
                  connection with or as a participant in any transaction having
                  that purpose or effect.

                  Signature:
                  After reasonable inquiry and to the best of my knowledge and
                  belief, I certify that the information set forth in this
                  statement is true, complete and correct.


                                                                       December 29, 2005
                                                              --------------------------------------------
                                                                       Date

                                                              AMVESCAP PLC

                                                              By:      /s/  Kevin M. Carome
                                                              --------------------------------------------


                                                              Kevin M. Carome
                                                              General Counsel