EXHIBIT 5.1

                 [LETTERHEAD OF WACHTELL, LIPTON, ROSEN & KATZ]

                                                                    July  , 2000

WJ Communications, Inc.
3333 Hillview Avenue
Palo Alto, California 94304

Ladies and Gentlemen:

    In connection with the registration of 5,400,000 shares of common stock, par
value $.01 per share (the "Shares"), of WJ Communications, Inc., a Delaware
corporation (the "Company"), under the Securities Act of 1933, as amended, on
Form S-1 filed with the Securities and Exchange Commission (the "Commission") on
June 2, 2000 (File No. 333-38518), as amended by Amendment No. 1 filed with the
Commission on July 12, 2000 and Amendment No. 2 filed with the Commission on
July 25, 2000 (collectively, and as it may be further amended, the "Registration
Statement"), you have requested our opinion with respect to the following
matters.

    In connection with the delivery of this opinion, we have examined originals
or copies of the Certificate of Incorporation and By-Laws of the Company as set
forth in exhibits to the Registration Statement, the Registration Statement,
certain resolutions adopted or to be adopted by the Board of Directors, the
specimen of common stock certificate representing the Shares and such other
records, agreements, instruments, certificates and other documents of public
officials, the Company and its officers and representatives and have made such
inquiries of the Company and its officers and representatives, as we have deemed
necessary or appropriate in connection with the opinions set forth herein. We
are familiar with the proceedings heretofore taken, and with the additional
proceedings proposed to be taken, by the Company in connection with the
authorization, registration, issuance and sale of the Shares. With respect to
certain factual matters material to our opinion, we have relied upon
representations from, or certificates of, officers of the Company. In making
such examination and rendering the opinions set forth below, we have assumed
without verification the genuineness of all signatures, the authenticity of all
documents submitted to us as originals, the authenticity of the originals of
such documents submitted to us as certified copies, the conformity to originals
of all documents submitted to us as copies, the authenticity of the originals of
such latter documents, and that all documents submitted to us as certified
copies are true and correct copies of such originals.

    Based on such examination and review, and subject to the foregoing, we are
of the opinion that the Shares have been duly authorized and, upon issuance,
delivery and payment therefor in the manner contemplated by the Registration
Statement, will be validly issued, fully paid and non-assessable.

    We are members of the Bar of the State of New York, and we have not
considered, and we express no opinion as to, the laws of any jurisdiction other
than the laws of the United States of America, the State of New York and the
General Corporation Law of the State of Delaware.

    We consent to the use of this opinion as an Exhibit to the Registration
Statement and to the reference to our firm in the Prospectus that is a part of
the Registration Statement. In giving such consent, we do not hereby admit that
we are in the category of persons whose consent is required under Section 7 of
the Securities Act of 1933.

                                          Very truly yours,

                                          /s/ Wachtell, Lipton, Rosen & Katz