<Page>
Exhibit 10.21
-------------------------------------------------------------------------------
PROPRIETARY INFORMATION, CONFIDENTIALITY AND INVENTIONS
AGREEMENT
-------------------------------------------------------------------------------
To: HITTITE
MICROWAVE CORPORATION
12 Elizabeth Drive
Chelmsford, Massachusetts 01824
As of March 1, 2001
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, as
may be necessary in the ordinary
course of performing my duties to the
Company, 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 or confidential or proprietary
information of any third parties subject to
a duty on the part of the Company to
maintain the confidentiality of such
information, 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. ASSIGNMENT OF INVENTIONS.
3.1 I hereby acknowledge and agree that the Company is the owner of
all
Inventions (as hereinafter defined). 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.
3.2 For purposes of this Agreement, "Inventions" shall mean all
discoveries, processes, designs,
technologies, devices, or improvements in any
of the foregoing or other
<Page>
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.
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 a