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                                                                   Exhibit 10.18

PROPRIETARY INFORMATION, CONFIDENTIALITY AND INVENTIONS AGREEMENT

To: HITTITE MICROWAVE CORPORATION
     21 Cabot Road
     Woburn, Massachusetts 01801                 As of February 18, 1992

     The undersigned, in consideration of and as a condition of my employment by
you hereby agrees as follows:

         1.       CONFIDENTIALITY. I agree to keep confidential, except as the
Company may otherwise consent in writing, and, except for the Company's benefit,
not to disclose or make any use of at any time either during or subsequent to my
employment, any Inventions (as hereinafter defined), trade secrets, confidential
information, knowledge, data or other information of the Company relating to
products, processes, know-how, designs, formulas, test data, customer lists,
business plans, marketing plans and strategies, pricing strategies, or other
subject matter pertaining to any business of the Company or any of its
affiliates, which I may produce, obtain, or otherwise acquire during the course
of my employment, except as herein provided. I further agree not to deliver,
reproduce or in any way allow any such trade secrets, confidential information,
knowledge, data or other information or any documentation relating thereto, to
be delivered to or used by any third parties without specific direction or
consent of a duly authorized representative of the Company.

         2.       CONFLICTING EMPLOYMENT; RETURN OF CONFIDENTIAL MATERIAL. I
agree that during my employment with the Company I will not engage in any other
employment, occupation, consulting or other activity relating to the business in
which the Company is now or may hereafter become engaged, or which would
otherwise conflict with my obligations to the Company. In the event my
employment with the Company terminates for any reason whatsoever, I agree to
promptly surrender and deliver to the Company all records, materials, equipment,
drawings, documents and data of which I may obtain or produce during the course
of my employment, and I will not take with me any description containing or
pertaining to any confidential information, knowledge or data of the Company
which I may produce or obtain during the course of my employment.

         3.       ASSIGNMENT OF INVENTIONS.

         3.1      I hereby acknowledge and agree that the Company is the owner
of all Inventions. In order to protect the Company's rights to such Inventions,
by executing this Agreement I hereby irrevocably assign to the Company all my
right, title and interest in and to all Inventions to the Company.

         3.2      For purposes of this Agreement, "Inventions" shall mean all
discoveries, processes, designs, technologies, devices, or improvements in any
of the foregoing or bother ideas, whether or not patentable and whether or not
reduced to practice, made or conceived by me (whether solely or jointly with
others) during, the period of my employment with the Company which relate in any
manner to the actual or demonstrably anticipated business, work, or research and
development of the Company, or result from or are suggested by any task assigned
to me or any work performed by me for or on behalf of the Company.

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         3.3      Any discovery, process, design, technology, device, or
improvement in any of the foregoing or other ideas, whether or not patentable
and whether or not reduced to practice, made or conceived by me (whether solely
or jointly with others) which I develop entirely on my own time not using any of
the Company's equipment, supplies, facilities, or trade SECRET information
("Personal Invention") is excluded from this Agreement provided such Personal
Invention (a) does not relate to the actual or demonstrably anticipated
business, research and development of the Company; and (b) does not result,
directly or indirectly, from any work performed by me for the Company.

         4.       DISCLOSURE OF INVENTIONS. I agree that in connection with any
Invention, I will promptly disclose such Invention to my immediate superior at
the Company in order to permit the Company to enforce its property rights to
such Invention in accordance with this Agreement. My disclosure shall be
received in confidence by the Company.

         5.       PATENTS AND COPYRIGHTS; EXECUTION OF DOCUMENTS.

         5.1      Upon request, I agree to assist the Company or its nominee (at
its expense) during and at any time subsequent to my employment in every
reasonable way to obtain for its own benefit patents and copyrights for
Inventions in any and all countries. Such patents and copyrights shall be and
remain the sole and exclusive property of the Company or its nominee. I agree to
perform such lawful acts as the Company deems to be necessary to allow it to
exercise all right, title and interest in and to such patents and copyrights.

         5.2      In connection with this Agreement, I agree to execute,
acknowledge and deliver to the Company or its nominee upon request and at its
expense all documents, including assignments of title, patent or copyright
applications, assignments of such applications, assignments of patents or
copyrights upon issuance, as the Company may determine necessary or desirable to
protect the Company's or its nominee's interest in Inventions, and/or to use in
obtaining patents or copyrights in any and all countries and to vest title
thereto in the Company or its nominee to any of the foregoing.

         6.       MAINTENANCE OF RECORDS. I agree to keep and maintain adequate
and current written records of all Inventions made by me (in the form of notes,
sketches, drawings and other records as may be specified by the Company), which
records shall be available to and remain the sole property of the Company at all
times.

         7.       PRIOR INVENTIONS. It is understood that all Personal
Inventions, if any, whether patented or unpatented, which I made prior to my
employment by the Company, are excluded from this Agreement. To preclude any
possible uncertainty, I have set forth on Schedule A attached hereto a complete
list of all of my prior Personal Inventions, including numbers of all patents
and patent applications and a brief description of all unpatented Personal
Inventions which are not the property of a previous employer. I represent and
covenant that the list is complete and that, if no items are on the list, I have
no such prior Personal Inventions. I agree to notify the Company in writing
before I make any disclosure or perform any work on behalf of the Company which
appears to threaten or conflict with proprietary rights I claim in any Personal
Invention. In the event of my failure to give such notice, I agree that I will
make no claim against the Company with respect to any such Personal Invention.

                                      - 2 -
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         8.       OTHER OBLIGATIONS. I acknowledge that the Company from time to
time may have agreements with other persons or with the U.S. Government or
agencies thereof, which impose obligations or restrictions on the Company
regarding Inventions made during the course of work thereunder or regarding the
confidential nature of such work. I agree to be bound by all such obligations
and restrictions and to take all action necessary to discharge the Company's
obligations.

         9.       TRADE SECRETS OF OTHERS. I represent that my performance of
all the terms of this Agreement and as an employee of the Company does not and
will not breach any agreement to keep confidential proprietary information,
knowledge or data acquired by me in confidence or in trust prior to my
employment with the Company, and I will not disclose to the Company, or induce
the Company to use, any confidential or proprietary information or material
belonging to any previous employer or others. I agree not to enter into any
agreement either written or oral in conflict herewith.

         10.      MODIFICATION. I agree that any subsequent change or changes in
my employment duties, salary or compensation or, if applicable, in any
Employment Agreement between the Company and me, shall not affect the validity
or scope of this Agreement.

         11.      SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon
my heirs, executors, administrators or other legal representatives- and is for
the benefit of the Company, its successors and assigns.

         12.      INTERPRETATION. IT IS THE INTENT OF THE PARTIES THAT in case
any one or more of the provisions contained in this Agreement shall, for any
reason, be held to be invalid, illegal or unenforceable in any respect, such
invalidity, illegality or unenforceability shall not affect the other provisions
of this Agreement, and this Agreement shall be construed as if such invalid,
illegal or unenforceable provision had never been contained herein. MOREOVER, IT
IS THE INTENT OF THE PARTIES THAT in case any one or more of the provisions
contained in this Agreement shall for any reason be held to be excessively broad
as to duration, geographical scope, activity or subject, such provision shall be
construed by limiting and reducing it in accordance with a judgment of a court
of competent jurisdiction, so as to be enforceable to the extent compatible with
applicable law.

         13.      WAIVERS. If either party should waive any breach of any
provision of this Agreement, he or it shall not thereby be deemed to have waived
any preceding or succeeding breach of the same or any other provision of this
Agreement.

         14.      COMPLETE AGREEMENT, AMENDMENTS. I acknowledge receipt of this
Agreement, and agree that with respect to the subject matter thereof it is my
entire agreement with the Company, superseding any previous oral or written
communications, representations, understandings, or agreements with the Company
or any officer or representative thereof. Any amendment to this Agreement or
waiver by either party of any right hereunder shall be effective only if
evidenced by a written instrument executed by the parties hereto, and, in the
case of the Company, upon written authorization of the Company's Board of
Directors.

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         15.      HEADINGS. The headings of the sections hereof are inserted for
convenience only and shall not be deemed to constitute a part hereof nor to
affect the meaning thereof.

         16.      COUNTERPARTS. This Agreement may be signed in two
counterparts, each of which shall be deemed an original and both of which shall
together constitute one agreement.

         17.      GOVERNING LAW. This Agreement shall be governed and construed
under Massachusetts law.

                                             EMPLOYEE

                                             /s/ Norman G. Hildreth 1-30-92
                                             ------------------------------
Accepted and Agreed:

HITTITE MICROWAVE CORPORATION

By: /s/ Yalcin Ayasli 1-29-92
    -------------------------
     Duly Authorized

                                      - 4 -<Page>

                                                                   Exhibit 10.19

PROPRIETARY INFORMATION, CONFIDENTIALITY AND INVENTIONS AGREEMENT

To: HITTITE MICROWAVE CORPORATION
21 Cabot Road
Woburn, Massachusetts 01801                                     As of 12/13/1999

         I, the undersigned, in consideration of and as a condition of my
employment by Hittite Microwave Corporation (the "Company"), and for other good
and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, hereby agree as follows:

         1.       CONFIDENTIALITY. I agree to keep confidential, except as the
Company may otherwise consent in writing, and, except for the Company's benefit,
not to disclose or make any use of at any time either during or subsequent to my
employment, any Inventions (as hereinafter defined), trade secrets, confidential
information, knowledge, data or other information of the Company relating to
products, processes, know-how, designs, formulas, test data, customer lists,
business plans, marketing plans and strategies, pricing strategies, or other
subject matter pertaining to any business of the Company or any of its
affiliates, which I may produce, obtain, or otherwise acquire during the course
of my employment, except as herein provided. I further agree not to deliver,
reproduce or in any way allow any such trade secrets, confidential information,
knowledge, data or other information or any documentation relating thereto, to
be delivered to or used by any third parties without specific direction or
consent of a duly authorized representative of the Company.

         2.       CONFLICTING EMPLOYMENT: RETURN OF CONFIDENTIAL MATERIAL. I
agree that during my employment with the Company I will not engage in any other
employment, occupation, consulting or other activity relating to the business in
which the Company is now or may hereafter become engaged, or which would
otherwise conflict with my obligations to the Company. In the event my
employment with the Company terminates for any reason whatsoever, I agree to
promptly surrender and deliver to the Company all records, materials, equipment,
drawings, documents and data which I may obtain or produce during the course of
my employment, and I further agree that I will not take with me any description
containing or pertaining to any confidential information, knowledge or data of
the Company which I may produce or obtain during the course of my employment.

         3.       NON-SOLICITATION OF COMPANY EMPLOYEES. I will not, during the
course of my employment and for a period of three (3) years thereafter
(regardless of the reason for termination of the employment relationship),
directly or indirectly, solicit, hire, attempt to hire, or assist in the hiring
of any employee of the Company, or otherwise persuade or attempt to persuade any
such employee to discontinue his/her employment relationship with the Company.

         4.       ASSIGNMENT OF INVENTIONS.

         4.1.     I hereby acknowledge and agree that the Company is the owner
of all Inventions (as herein defined). In order to protect the Company's rights
to such Inventions, by executing

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this Agreement I hereby irrevocably assign to the Company all my right, title
and interest in and to all Inventions.

         4.2.     For purposes of this Agreement, "Inventions" shall mean all
discoveries, processes, designs, technologies, devices, or improvements in any
of the foregoing or other ideas, whether or not patentable and whether or not
reduced to practice, made or conceived by me (whether solely or jointly with
others) during the period of my employment with the Company which relate in any
manner to the actual or demonstrably anticipated business, work, or research and
development of the Company, or result from or are suggested by any tasks
assigned to me or any work performed by me for or on behalf of the Company.

         4.3.     Any discovery, process, design, technology, device, or
improvement in any of the foregoing or other ideas, whether or not patentable
and whether or not reduced to practice, made or conceived by me (whether solely
or jointly with others) which I develop entirely on my own time not using any of
the Company's equipment, supplies, facilities, or trade secret information
("Personal Invention") is excluded from this Agreement provided such Personal
Invention (a) does not relate to the actual or demonstrably anticipated
business, research and development of the Company; and (b) does not result,
directly or indirectly, from any work performed by me for the Company.

         5.       DISCLOSURE OF INVENTIONS. I agree that in connection with any
Invention, I will promptly disclose such Invention to my immediate supervisor at
the Company in order to permit the Company to enforce its property rights to
such Invention in accordance with this Agreement. My disclosure shall be
received in confidence by the Company.

         6.       PATENTS AND COPYRIGHTS; EXECUTION OF DOCUMENTS.

         6.1.     Upon request, I agree to assist the Company or its nominee (at
its expense) during and at any time subsequent to my employment in every
reasonable way to obtain for its own benefit patents and copyrights for
Inventions in any and all countries. Such patents and copyrights shall be and
remain the sole and exclusive property of the Company or its nominee. I agree to
perform such lawful acts as the Company deems to be necessary to allow it to
exercise all right, title and interest in and to such patents and copyrights.

         6.2.     In connection with this Agreement, I agree to execute,
acknowledge and deliver to the Company or its nominee upon request and at its
expense all documents, including assignments of title, patent or copyright
applications, assignments of such applications, assignments of patents or
copyrights upon issuance, as the Company may determine necessary or desirable to
protect the Company's or its nominee's interest in Inventions, and/or to use in
obtaining patents or copyrights in any and all countries and to vest title
thereto in the Company or its nominee to any of the foregoing.

         7.       MAINTENANCE OF RECORDS. I agree to keep and maintain adequate
and current written records of all Inventions made by me (in the form of notes,
sketches, drawings and other records as may be specified by the Company), which
records shall be available to and remain the sole property of the Company at all
times.

                                      - 2 -
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         8.       PRIOR INVENTIONS. It is understood that all Personal
Inventions, if any, whether patented or unpatented, which I made prior to my
employment by the Company, are excluded from this Agreement. To preclude any
possible uncertainty, I have set forth on Schedule A attached hereto a complete
list of all of my prior Personal Inventions, including numbers of all patents
and patent applications and a brief description of all unpatented Personal
Inventions which are not the property of a previous employer. I represent and
covenant that the list is complete and that, if no items are on the list, I have
no such prior Personal Inventions. I agree to notify the Company in writing
before I make any disclosure or perform any work on behalf of the Company which
appears to threaten or conflict with proprietary rights I claim in any Personal
Invention. In the event of my failure to give such notice, I agree that I will
make no claim against the Company with respect to any such Personal Invention.

         9.       OTHER OBLIGATIONS. I acknowledge that the Company from time to
time may have agreements with other persons or with the U.S. Government or
agencies thereof, which impose obligations or restrictions on the Company
regarding Inventions made during the course of work thereunder or regarding the
confidential nature of such work. I agree to be bound by all such obligations
and restrictions and to take all action necessary to discharge the Company's
obligations.

         10.      TRADE SECRETS OF OTHERS. I represent that my performance of
all the terms of this Agreement and as an employee of the Company does not and
will not breach any agreement to keep confidential proprietary information,
knowledge or data acquired by me in confidence or in trust prior to my
employment with the Company, and I will not disclose to the Company, or induce
the Company to use, any confidential or proprietary information or material
belonging to any previous employer or others. I agree not to enter into any
agreement either written or oral in conflict herewith.

         11.      Without limiting the remedies available to the Company, I
acknowledge that a breach of any of the terms of this Agreement could result in
irreparable injury to the Company for which there might be no adequate remedy at
law and that, in the event of such a breach or threat thereof, the Company shall
be entitled to obtain a temporary restraining order and/or a preliminary
injunction and a permanent injunction restraining me from engaging in any
activities prohibited by this Agreement or such other equitable relief as may be
required to enforce specifically any of the covenants of this Agreement.

         12.      MODIFICATION. I agree that any subsequent change or changes in
my employment duties, salary or compensation or, if applicable, in any
Employment Agreement between the Company and me, shall not affect the validity
or scope of this Agreement.

         13.      SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon
my heirs, executors, administrators or other legal representatives and is for
the benefit of the Company, its successors and assigns.

         14.      INTERPRETATION. IT IS THE INTENT OF THE PARTIES THAT in case
any one or more of the provisions contained in this Agreement shall, for any
reason, be held to be invalid, illegal or unenforceable in any respect, such
invalidity, illegality or unenforceability shall not affect the other provisions
of this Agreement, and this Agreement shall be construed as if such

                                      - 3 -
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invalid, illegal or unenforceable provision had never been contained herein.
MOREOVER, IT IS THE INTENT OF THE PARTIES THAT in case any one or more of the
provisions contained in this Agreement shall for any reason be held to be
excessively broad as to duration, geographical scope, activity or - subject,
such provision shall be construed by dating and reducing it in accordance with a
judgment of a court of competent jurisdiction, so as to be enforceable to the
extent compatible with applicable law.

         15.      WAIVERS. If either party should waive any breach of any
provision of this Agreement, he or it shall not thereby be deemed to have waived
any preceding or succeeding breach of the same or any other provision of this
Agreement.

         16.      COMPLETE AGREEMENT, AMENDMENTS. I acknowledge receipt of this
Agreement, and agree that with respect to the subject matter thereof it is my
entire agreement with the Company, superseding any previous oral or written
communications, representations, understandings, or agreements with the Company
or any officer or representative thereof. I understand and acknowledge that this
Agreement is an agreement of proprietary information, confidentiality and
inventions, and that this is not a contract for any term of employment and does
not modify the at-will status of the employment relationship. I further
acknowledge that this Agreement creates no contractual terms of employment other
than those specifically enumerated herein. Any amendment to this Agreement or
waiver by either party of any right hereunder shall be effective only if
evidenced by a written instrument executed by the parties hereto, and, in the
case of the Company, upon written authorization of the Company's Board of
Directors.

         17.      HEADINGS. The headings of the sections hereof are inserted for
convenience only and shall not be deemed to constitute a part hereof nor to
affect the meaning thereof.

         18.      COUNTERPARTS. This Agreement may be signed in two
counterparts, each of which shall be deemed an original and both of which shall
together constitute one agreement.

         19.      GOVERNING LAW. This Agreement shall be governed and construed
under Massachusetts Law.

                                             EMPLOYEE

                                             /s/ Michael Koechlin 12-13-99
                                             ---------------------------------

                                             Accepted and Agreed:

                                             HITTITE MICROWAVE CORPORATION

                                             By: /s/ William Sylvanowicz
                                                 ----------------------------
                                             Duly Authorized

                                      - 4 -

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