Amendment No. 1 to Rights Agreement



 EXHIBIT 4.2.1 
  
 AMENDMENT NO. ONE 
 TO RIGHTS AGREEMENT 
  
 THIS AMENDMENT NO. ONE TO RIGHTS
AGREEMENT dated as of December 16, 2005 (the “Amendment”) with respect to the Rights Agreement dated as of December 22, 2000 (herein, including all amendments, referred to as the “Agreement”) between Microsemi
Corporation, a Delaware corporation (the “Company”), and Mellon Investor Services, LLC, a New Jersey limited liability company (the “Rights Agent”). 
  
 W I T N E S S E T H 
  
 WHEREAS, the Board of Directors deems it appropriate under the Agreement and in the exercise of its authority under the Agreement to approve an amendment
of the Agreement prior to the Distribution Date; 
  
 NOW,
THEREFORE, FOR GOOD AND VALUABLE CONSIDERATIONS, the receipt and sufficiency of which are hereby acknowledged, the Agreement is hereby amended as follows: 
  
 1. Section 3(a), the third sentence is amended and restated in its entirety as follows: “In the event that an adjustment in the number of Rights
per share of Common Stock has been made pursuant to Section 11(p) hereof, at the time of distribution of the Rights Certificates, the Company shall make the necessary and appropriate adjustments, in accordance with Section 14(a) hereof,
such that all fractional shares are separately and independently valid, and after aggregating all fractional Rights to be received by such holder, each holder of fractional Rights shall receive from Parent an amount pursuant to Section 14(a)
hereof.” 
  
 2. Section 11(h), in the first sentence,
the reference to “(calculated to the nearest one-millionth)” is amended and restated as “(calculated to the nearest one ten-millionth of a share of Preferred Stock)”. 
  
 3. Section 11(h), in the first sentence, the reference to “price” is amended and restated as
“prior”, and in Section 11(p), in the first sentence, the reference to “price” is amended and restated as “prior”. 
  
 4. Section 11(i), in the third sentence, the reference to “(calculated to the nearest one-ten-thousandth)” is amended and restated as
“(calculated to the nearest one ten-thousandth of a Right)”. 
  
 5. Section 14(a), the first sentence is amended and restated in its entirety as follows: “The Company shall issue fractional Rights as contemplated in Section 11(p), and such fractions of Rights as are issued pursuant thereto
shall entitle the holder, in proportion to such holder’s fractional Rights, to exercise and to have all the benefits, powers and privileges of Rights under this agreement. Except as contemplated in Section 11(p), the Company shall not
issue fractional Rights. Except for fractional Rights issued as contemplated in Section 11(p), each holder of Rights who would otherwise be entitled to a fraction of a Right (after aggregating all fractional Rights to be received by such
holder) shall receive from Company an amount of 

  

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cash without interest (rounded to the nearest whole cent) equal to the product of (i) such fraction, multiplied by (ii) the current market value of
a whole Right.” 
  
 6. Section 23(a), in the first
sentence, “10%” is amended and restated as “20%”. 
  
 7. Section 23(a), after the final sentence of the section, insert “The redemption of the Rights by the Board of Directors of the Company may be made effective at such time and on such date (the “Redemption Date”), on
such basis and with such conditions as the Board of Directors of the Company, in its sole discretion, may establish.” 
  
 8. Section 24(b), after the final sentence of the section, insert “Any failure to give, or any defect in, any notice of redemption shall not
affect the validity of such redemption.” 
  
 9.
Section 26 of the Agreement, the respective addresses for notice for the Company and the Rights Agent are amended and restated as follows: 
  
 MICROSEMI CORPORATION 
 2381 Morse Avenue 
 Irvine, California 92614 
 Attention: David R. Sonksen, Executive Vice President, Chief Financial Officer 
  
 MELLON INVESTOR SERVICES, LLC 
 400 South Hope Street 
 4th Floor 
 Los Angeles, CA 90071 
 Attention: Relationship Manager 
  
 With a copy to: 
 MELLON INVESTOR SERVICES, LLC 
 Newport Office Center VII 
 Jersey City, New Jersey 07310 
 Attention: General Counsel 
  
 10.
Section 26, after the last sentence in Section 26, insert “The Rights Agent or the Company may, from time to time, change its address pursuant to this Section 26 upon delivery of written notice to the other party, in accordance
with this Section 26.” 
  
 11. Exhibit A to the
Agreement is amended as set forth in the Certificate of Amendment of Certificate of Designation of Rights, Preferences and Privileges of Series A Junior Participating Preferred Stock of Microsemi Corporation, attached hereto. 
  
 12. Except as expressly provided in this Amendment, and except for the
additional terms and provisions set forth in this Amendment, the Agreement shall continue in full force and effect in accordance with its terms, and this Amendment shall be governed by such terms. This Amendment and the Agreement, as amended,
supersede any other agreement or understanding concerning the subject matter hereof. 
  
 13. Capitalized terms used herein and not defined herein shall have their defined meanings as set forth in the Agreement. 
  

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 14. This Amendment may be executed in one or more counterparts, each of which shall be deemed an original
and all of which together shall constitute one instrument. 
  
 15.
The undersigned officers of the Company each hereby certifies, as indicated by each officer’s signature below, to the Rights Agent that the Amendment is in compliance with the terms of Section 27 of the Agreement. 
  
 IN WITNESS WHEREOF, the parties hereto have caused this Amendment No. One to
Rights Agreement to be duly executed all as of the day and year first above written. 
  

			
	MICROSEMI CORPORATION
		
	 By:
	 	 /s/    James J. Peterson        


	 	 	 James J. Peterson,
 President and Chief Executive Officer

	
	 Attest:
  

[Seal]

		
	 By:
	 	 /s/    David R. Sonksen       


	 	 	 David R. Sonksen, Executive Vice President,
 Chief Financial Officer, Secretary and Treasurer



  
  

			
	MELLON INVESTOR SERVICES, LLC
		
	 By:
	 	

	 	 	 Name:
 Title:

		
	 By:
	 	

	 	 	 Name:
 Title:



  
  
  

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