Filed by Exar Corporation Pursuant to Rule 425

Under the Securities Act of 1933

And Deemed Filed Pursuant to Rule 14a-12

Under the Securities Exchange Act of 1934

Subject Company: Sipex Corporation

Commission File No.: 1-33403

A Strategic Connectivity Opportunity July 23, 2007

2 Disclaimer Cautionary Statement Regarding Forward-Looking Statements This document contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995. These statements are based on management’s current expectations and beliefs and are subject to a number of factors and uncertainties that could cause actual results to differ materially from those described in the forward-looking statements. The forward-looking statements contained in this document include statements about future financial and operating results; benefits of the transaction to customers, stockholders and employees; potential synergies and cost savings resulting from the transaction; the ability of the combined company to drive growth and expand customer and partner relationships and other statements regarding the proposed transaction. These statements are not guarantees of future performance, involve risks, uncertainties and assumptions that are difficult to predict, and are based upon assumptions as to future events that may not prove accurate. Therefore, actual outcomes and results may differ materially from what is expressed herein. For example, if Exar and Sipex do not each receive required stockholder approval or the parties fail to satisfy other conditions to closing, the transaction may not be consummated. Similarly, anticipated costs savings may not be achieved and projections as to whether, when and the extent to which the transaction will be accretive may not prove accurate.  In any forward-looking statement in which Exar or Sipex expresses an expectation or belief as to future results, such expectation or belief is expressed in good faith and believed to have a reasonable basis, but there can be no assurance that the statement or expectation or belief will result or be achieved or accomplished. The following factors, among others, could cause actual results to differ materially from those described in the forward-looking statements: failure of the Exar and Sipex stockholders to approve the proposed merger; the challenges and costs of closing, integrating, restructuring and achieving anticipated synergies; the ability to retain key employees; and other economic, business, competitive, and/or regulatory factors affecting the businesses of Exar and Sipex generally, including those set forth in the filings of Exar and Sipex with the Securities and Exchange Commission, especially in the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of their respective annual reports on Form 10-K and quarterly reports on Form 10-Q, their current reports on Form 8-K and other SEC filings. Exar and Sipex are under no obligation to (and expressly disclaim any such obligation to) update or alter their forward-looking statements whether as a result of new information, future events, or otherwise.

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 3 Exar Strategic Vision Leader in System-Level Mixed-Signal Connectivity Solutions Build a $300M Company in 3 to 5 Years through Strategic Acquisitions and Organic Growth

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 4 A New Strategic Focus • Key management changes made in Feb 2007 – Interim CEO named – CFO hired • Committed to substantial revenue, profit and EPS growth • Focused on transforming Company • Launched program to substantially improve R&D ROI • Headcount cut by 6% in Mar 2007 • Evaluation of potential acquisitions continues

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 5 First Step – Exar-Sipex Merger Exar – Sipex Merger Announced May 8, 2007 Shareholder approvals and closing expected on August 24, 2007

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 6 • Leading supplier of analog and mixed-signal silicon solutions for the serial communications, network transmission and storage markets • Year Founded: 1971 • Headquarters: Fremont, CA • Revenue (LTM - Mar 2007): $69M • Key Product Families • Network Transmission • Serial Communications • Storage Interconnect • Employees: 235 • Leading supplier of analog and mixed-signal silicon solutions for the power management, interface and optical storage markets • Year Founded: 1965 • Headquarters: Milpitas, CA • Revenue (LTM – Mar 2007): $78M • Key Product Families • Power Management • Interface • Optical Storage • Employees: 270 Company Profiles

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 7 Transaction Overview Structure • Combined company will maintain Exar name • Stock-for-stock exchange • 0.6679 shares of Exar for each share of Sipex • Stockholder Ownership: Exar 68%, Sipex  32% Financials • Pro forma revenues of ~$150M (LTM) • Pro forma cash of ~$365M (Mar 2007) • >$10M of annualized Non-GAAP cost synergies anticipated by CY 2008 Q2 • Lower Non-GAAP taxes expected due to use of Sipex NOLs • Non-GAAP earnings expected to be accretive by CY 2008 Q2 Leadership • Chairman: Richard L. Leza • Chief Executive Officer: Ralph Schmitt • Chief Financial Officer: J. Scott Kamsler Governance • 5 Board members from Exar, including Richard L. Leza • 3 Board members from Sipex, including Ralph Schmitt Timing • Announced, May 2007 • Shareholder approvals and closing expected on August 24, 2007

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 8 • Establish product leadership positions across a broader spectrum of high growth connectivity solutions – Complementary products and technologies • Accelerate revenue growth – Leverage cross-selling and sales channel opportunities – Considerably strengthened presence in high growth China/Asia Pac regions – Significant scale benefits • Significant cost synergies expected • Accelerate earnings growth anticipated • Accretive: target – CY 2008 Q2 Transaction Rationale

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 9 Scale to Expand Growth Opportunities • More competitive organization with enhanced growth prospects • Expanded array of products, customers and channels • Complementary products and technology capabilities • Strong balance sheet • Platform for consolidation

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 10 Near-Term Synergies • Revenue expansion through cross-selling and focused channel partners • >$10M of annualized Non-GAAP cost synergies anticipated by CY 2008 Q2 • Lower Non-GAAP taxes expected due to use of Sipex NOLs • Optimization of businesses and projects for accelerated second year revenue and earnings growth

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 11 Network Transmission Interface Serial Communications Power Management Broader Product Portfolio >30% 5-10% 15-20% Expected Market Growth Rate ~ Pro Forma Revenue % 20% 55% 25%* * Includes Sipex Optical/Other

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 12 Complementary Products, Technologies & Markets MPOS Mappers Framers SONET/SDH to OC-192 T/E SAS SATA FC ISA & PCI Multi-channel Low Voltage/ Low Power UARTS RS-232 Combo Communications Storage / Computing Consumer Industrial Wireless PowerBlox Buck Reg Boost Reg Charge Pumps Controllers Multiprotocol RS-232 USB RS-485 Programmable Skew Spread Spectrum ZDB I 2 C & SPI

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 13 Increased Customer Relevancy & Diversity

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 14 End Market & Geographic Presence Exar Business Units Sipex Business Units Network Serial Power Transmission Communications Interface Management End Markets Industrial Consumer Communications Storage / Computing Market Penetration Americas Europe Asia

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 15 56% 29% 15% Interface Power Optical/Other Revenue by Market Segment (LTM – Mar 2007) Sipex Exar Pro forma Combined ~$150M 58% 3% 39% Serial Communications Video & Imaging Network & Transmission 57% 16% 18% 9% Interface/Serial Power Network & Transmission Other

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 16 20% 60% 20% North America Asia Europe/ROW Revenue by Geography (LTM – Mar 2007) Sipex Exar Pro forma Combined ~$150M 44% 30% 26% North America Asia Europe/ROW 31% 46% 23% North America Asia Europe/ROW

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 17 Future Expansion Through Acquisition Network Transmission Interface Power Management Combined Enterprise SATA I/II PCI Express USB Multi-Protocol Ethernet Digital Power DC/DC Batter Chg

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 18 Summary Pro Forma Financials • Pro forma annual revenue doubled to ~$150M (LTM) • Pro forma cash of ~$365M (Mar 2007) • No debt following merger and conversion of Sipex notes • >$10M of annualized Non-GAAP cost synergies anticipated by CY 2008 Q2 • Lower Non-GAAP taxes expected due to use of Sipex NOLs • NOL tax benefit reduces goodwill • Non-GAAP earnings expected to be accretive by CY 2008 Q2

Increasing Shareholder Value Transaction Rationale Pro Forma Financials Overview Of Merger 19 Increasing Shareholder Value • Broader footprint – End markets diversified – Product portfolio broadened – Customer base expanded • Stronger Company – Management team – Synergies – revenue and cost – Core technical competencies deepened • Short term impact – Revenue doubles – Expected to be accretive by CY 2008 Q2 on a Non- GAAP basis

An Opportunity for Increasing Shareholder Value

21 Legend Additional Information and Where You Can Find It Exar has filed a Registration Statement on Form S-4 containing a proxy statement/prospectus and other documents concerning the proposed merger transaction with the Securities and Exchange Commission (the “SEC”). Security holders are urged to read the proxy statement/prospectus and other relevant documents filed with the SEC because they contain important information. Security holders may obtain a free copy of the proxy statement/prospectus and other documents filed by Exar and Sipex with the SEC at the SEC’s web site at http://www.sec.gov. The proxy statement/prospectus and other documents may also be obtained for free by contacting Exar Investor Relations by e-mail at investorrelations@Exar.com or by telephone at 1-510-668- 7201 or by contacting Sipex Investor Relations by e-mail at investorrelations@Sipex.com or by telephone at 1-408-934-7586. Exar and its executive officers and directors may be deemed to be participants in the solicitation of proxies from Exar’s stockholders with respect to the transactions contemplated by the merger agreement. Information regarding such executive officers and directors is included in Exar’s Proxy Statement for its 2006 Annual Meeting of Stockholders filed with the SEC on August 9, 2006, which is available free of charge at the SEC’s web site at http://www.sec.gov and from Exar Investor Relations which can be contacted by e-mail at investorrelations@Exar.com or by telephone at 1-510-668-7201. Certain executive officers and directors of Exar have interests in the transaction that may differ from the interests of Exar stockholders generally. These interests are described in the proxy statement/prospectus. Sipex and its executive officers and directors may be deemed to be participants in the solicitation of proxies from Sipex’s stockholders with respect to the transactions contemplated by the merger agreement. Information regarding such executive officers and directors is included in Sipex’s Proxy Statement for its 2006 Annual Meeting of Stockholders filed with the SEC on October 24, 2006, which is available free of charge at the SEC’s web site at http://www.sec.gov and from Sipex Investor Relations which can be contacted by e-mail at investorrelations@Sipex.com or by telephone at 1-408-934-7586. Certain executive officers and directors of Sipex have interests in the transaction that may differ from the interests of Sipex stockholders generally. These interests are described in the proxy statement/prospectus.