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                                                                   Exhibit 10.53
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               FIRST AMENDMENT TO CREDIT AND SECURITY AGREEMENT
                            AND WAIVER OF DEFAULTS

          This Amendment, dated as of March 30, 2001, is made by and between RF
MONOLITHICS, INC., a Delaware corporation (the "Borrower"), and WELLS FARGO
BUSINESS CREDIT, INC., a Minnesota corporation (the "Lender").

                                R E C I T A L S

          The Borrower and the Lender have entered into a Credit and Security
Agreement dated as of December 8, 2000 (the "Credit Agreement").  Capitalized
terms used in these recitals have the meanings given to them in the Credit
Agreement unless otherwise specified.

          The Borrower has requested that certain amendments be made to the
Credit Agreement, which the Lender is willing to make pursuant to the terms and
conditions set forth herein.

          NOW, THEREFORE, in consideration of the premises and of the mutual
covenants and agreements herein contained, it is agreed as follows:

          1.   Defined Terms. Capitalized terms used in this Amendment which are
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defined in the Credit Agreement shall have the same meanings as defined therein,
unless otherwise defined herein.

          2.   Amendment to Section 6.16.  Section 6.16 of the Credit Agreement
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is amended in its entirety to read as follows:

               Minimum Book Net Worth.  The Borrower will maintain, during each
               ----------------------
          period described below, its Book Net Worth in an amount not less than
          the amount set forth below:

               (a)  As of February 28, 2001, a minimum Book Net Worth of not
          less than $29,700,000;

               (b)  From March 1, 2001 through May 31, 2001, a minimum Book Net
          Worth of not less than $29,200,000;

               (c)  From June 1, 2001 through August 31, 2001, a minimum Book
          Net Worth of not less than $29,500,000; and

               (d)  From September 1, 2001 through November 30, 2001, a minimum
          Book Net Worth of not less than the Book Net Worth as of FYE August
          31, 2001, minus $1,500,000.

          3.   Amendment to Section 6.17.  Section 6.17 of the Credit Agreement
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is amended in its entirety to read as follows:

               Quarterly Minimum Net Income.  The Borrower will achieve (a)
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          during the six month fiscal period ended February 28, 2001, a minimum
          Net Income of greater than <$3,000,000>; (b) during the nine month
          fiscal period ending on May 31, 2001, a minimum Net Income of greater
          than <$3,500,000>; (c) during the fiscal year ending on August 31,
          2001, a minimum Net Income of greater than <$3,200,000>; and (d)
          during the three month fiscal period from August 31, 2001, to November
          30, 2001, a minimum Net Income of greater than <$1,500,000>.

          4.   Amendment to Exhibit C.  Exhibit C to the Credit Agreement is
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hereby amended to be in the form of Exhibit C to this Amendment.
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          5.   No Other Changes. Except as explicitly amended by this Amendment,
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all of the terms and conditions of the Credit Agreement shall remain in full
force and effect and shall apply to any advance or letter of credit thereunder.

          6.   Waiver of Defaults.  The Borrower is in default of Sections 6.16,
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6.17 and 6.18 of the Credit Agreement (collectively, the "Defaults").  Upon the
terms and subject to the conditions set forth in this Amendment, the Lender
hereby waives the Defaults through February 28, 2001.  This waiver shall be
effective only in this specific instance and for the specific purpose for which
it is given, and this waiver shall not entitle the Borrower to any other or
further waiver in any similar or other circumstances.

          7.   Amendment Fee.  The Borrower shall pay the Lender as of the date
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hereof a fully earned, non-refundable fee in the amount of $80,000.00 in
consideration of the Lender's execution of this Amendment (the "Amendment Fee").
The Amendment Fee shall be payable on the first day of each calendar month in
equal installments of $20,000.00 commencing on April 1, 2001 and ending on July
1, 2001.  Notwithstanding the foregoing, if a Default or an Event of Default or
a breach, default or event of default under any Security Document or other
document held by Lender occurs at any time prior to July 1, 2001, the entire
remaining amount of the Amendment Fee shall be immediately due and payable in
full.

          8.   Conditions Precedent.  This Amendment, and the waiver set forth
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in Paragraph 6 hereof, shall be effective when the Lender shall have received an
executed original hereof, together with each of the following, each in substance
and form acceptable to the Lender in its sole discretion:

               (a)  The Acknowledgment and Agreement of Guarantor set forth at
          the end of this Amendment, duly executed by the Guarantor.

               (b)  A Certificate of the Secretary of the Borrower certifying as
          to (i) the resolutions of the board of directors of the Borrower
          approving the execution and delivery of this Amendment, (ii) the fact
          that the articles of incorporation and bylaws of the Borrower, which
          were certified and delivered to the Lender pursuant to the Certificate
          of Authority of the Borrower's secretary or assistant secretary dated
          as of December 8, 2000 in connection with the execution and delivery
          of the Credit Agreement continue in full force and effect and have not
          been amended or otherwise modified except as set forth in the
          Certificate to be delivered, and (iii) certifying that the officers
          and agents of the Borrower who have been certified to the Lender,
          pursuant to the Certificate of Authority of the Borrower's secretary
          or assistant secretary dated as of December 8, 2000, as being
          authorized to sign and to act on behalf of the Borrower continue to be
          so authorized or setting forth the sample signatures of each of the
          officers and agents of the Borrower authorized to execute and deliver
          this Amendment and all other documents, agreements and certificates on
          behalf of the Borrower.

               (c)  Payment of the fee described in Paragraph 7.

               (d)  Such other matters as the Lender may require.

          9.   Representations and Warranties.  The Borrower hereby represents
               ------------------------------
and warrants to the Lender as follows:s

               (a)  The Borrower has all requisite power and authority to
          execute this Amendment and to perform all of its obligations
          hereunder, and this Amendment has been duly executed and delivered by
          the Borrower and constitutes the legal, valid and binding obligation
          of the Borrower, enforceable in accordance with its terms.

               (b)  The execution, delivery and performance by the Borrower of
          this Amendment have been duly authorized by all necessary corporate
          action and do not (i) require any authorization, consent or approval
          by any governmental department, commission, board, bureau, agency or
          instrumentality, domestic or foreign, (ii) violate any provision of
          any law, rule or regulation or of any order, writ, injunction or
          decree presently in effect, having applicability to the Borrower, or
          the articles of incorporation or by-laws of the

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     Borrower, or (iii) result in a breach of or constitute a default under any
     indenture or loan or credit agreement or any other agreement, lease or
     instrument to which the Borrower is a party or by which it or its
     properties may be bound or affected.

          (c)  All of the representations and warranties contained in Article V
     of the Credit Agreement are correct on and as of the date hereof as though
     made on and as of such date, except to the extent that such representations
     and warranties relate solely to an earlier date.

     10.  References.  All references in the Credit Agreement to "this
          ----------
Agreement" shall be deemed to refer to the Credit Agreement as amended hereby;
and any and all references in the Security Documents to the Credit Agreement
shall be deemed to refer to the Credit Agreement as amended hereby.

     11.  No Other Waiver.  Except as set forth in Paragraph 6 hereof, the
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execution of this Amendment and acceptance of any documents related hereto shall
not be deemed to be a waiver of any Default or Event of Default under the Credit
Agreement or breach, default or event of default under any Security Document or
other document held by the Lender, whether or not known to the Lender and
whether or not existing on the date of this Amendment.

     12.  Release.  The Borrower, and the Guarantor by signing the
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Acknowledgment and Agreement of Guarantor set forth below, each hereby
absolutely and unconditionally releases and forever discharges the Lender, and
any and all participants, parent corporations, subsidiary corporations,
affiliated corporations, insurers, indemnitors, successors and assigns thereof,
together with all of the present and former directors, officers, agents and
employees of any of the foregoing, from any and all claims, demands or causes of
action of any kind, nature or description, whether arising in law or equity or
upon contract or tort or under any state or federal law or otherwise, which the
Borrower or such Guarantor has had, now has or has made claim to have against
any such person for or by reason of any act, omission, matter, cause or thing
whatsoever arising from the beginning of time to and including the date of this
Amendment, whether such claims, demands and causes of action are matured or
unmatured or known or unknown.

     13.  Costs and Expenses.  The Borrower hereby reaffirms its agreement under
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the Credit Agreement to pay or reimburse the Lender on demand for all costs and
expenses incurred by the Lender in connection with the Credit Agreement, the
Security Documents and all other documents contemplated thereby, including
without limitation all reasonable fees and disbursements of legal counsel.
Without limiting the generality of the foregoing, the Borrower specifically
agrees to pay all fees and disbursements of counsel to the Lender for the
services performed by such counsel in connection with the preparation of this
Amendment and the documents and instruments incidental hereto. The Borrower
hereby agrees that the Lender may, at any time or from time to time in its sole
discretion and without further authorization by the Borrower, make a loan to the
Borrower under the Credit Agreement, or apply the proceeds of any loan, for the
purpose of paying any such fees, disbursements, costs and expenses and the
Amendment Fee required under paragraph 7 hereof.

     14.  Miscellaneous.  This Amendment and the Acknowledgment and Agreement of
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Guarantor may be executed in any number of counterparts, each of which when so
executed and delivered shall be deemed an original and all of which
counterparts, taken together, shall constitute one and the same instrument.

     15.  Governing Law; Jurisdiction, Venue; Waiver of Jury Trial.  This
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Amendment, the Acknowledgment and Agreement of Guarantor and the Loan Documents
shall be governed by and construed in accordance with the substantive laws
(other than conflict laws) of the State of Texas.  Each party hereto and the
Guarantor hereby (i) consents to the personal jurisdiction of the state and
federal courts located in the State of Texas in connection with any controversy
related to this Amendment; (ii) waives any argument that venue in any such forum
is not convenient, (iii) agrees that any litigation initiated by the Lender or
the Borrower in connection with this Amendment or the other Loan Documents shall
be venued in either the District Court of Collin County, Texas, or the United
States District Court for the Northern  District of Texas; and (iv) agrees that
a final judgment in any such suit, action or proceeding shall be conclusive and
may be enforced in other jurisdictions by suit on the judgment or in any other
manner provided by law.  THE PARTIES WAIVE ANY RIGHT TO TRIAL BY JURY IN ANY
ACTION OR PROCEEDING BASED ON OR PERTAINING TO THIS AMENDMENT.

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     16.  ENTIRE AGREEMENT.  THIS AMENDMENT AND ALL OTHER INSTRUMENTS,
          ----------------
DOCUMENTS AND AGREEMENTS EXECUTED AND DELIVERED IN CONNECTION WITH THIS
AMENDMENT EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE PARTIES HERETO AND
SUPERSEDE ANY AND ALL PRIOR COMMITMENTS, AGREEMENTS, REPRESENTATIONS AND
UNDERSTANDINGS, WHETHER WRITTEN OR ORAL, RELATING TO THIS AMENDMENT, AND MAY NOT
BE CONTRADICTED OR VARIED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT
ORAL AGREEMENTS OR DISCUSSIONS OF THE PARTIES HERETO.  THERE ARE NO ORAL
AGREEMENTS AMONG THE PARTIES HERETO.

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed as of the date first written above.

WELLS FARGO BUSINESS CREDIT, INC.                RF MONOLITHICS, INC.


By: /s/ Terrance O. McKinney                     By: /s/ David M. Kirk
    -------------------------------------            ---------------------------
    Terrance O. McKinney                             David M. Kirk
    Assistant Vice President                         President

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