Motorola Corporation

Fred H Bonn

John M Golio

George B Norris

A field effect transistor structure which can serve as a low noise amplifier. The field effect transistor has a major surface and source and drain regions extending from the major surface into a body of semiconductor material. A channel region is formed in a portion of the body of semiconductor material separating the source and drain regions. The channel region has a first boundary perpendicular to the major and contiguous with the source region, a second boundary parallel to the first boundary and contiguous with the drain region, a third boundary perpendicular to the first boundary, and a fourth boundary parallel to the channel region. A first portion of the channel region is enclosed by a first border parallel to the first boundary of the channel region, a second border parallel to the second boundary of the channel region, a third boundary of the channel region, and the fourth boundary of the channel region. A non-conductive section is formed in the body of semiconductor material extending from the major surface and enclosed by a first edge coinciding with the first border of the first portion of the channel region, a second edged coinciding with the second border of the first portion of the channel region, a third edge parallel to the third boundary of the channel region, and a fourth edge parallel to the fourth boundary of the channel region. A gate structure is formed above the first portion of the channel region.

Field effect transistor

A mixer circuit (10) combines a buffered RF signal with the LO signal at the gate of a mixing transistor (20) for providing sum and difference product terms as the IF output signal. An inductor (46) provides a DC signal path between the source of the mixing transistor and the drain of the buffering transistor (14) to share the same operating current and thereby reduce power consumption in the mixer. The DC path inductor provides a high impedance to block the RF signal and LO signal. A bias circuit (26, 28) sets the bias point at the gate of the mixing transistor to a mid-point value between V.sub.DD and ground potential. In disable mode, the bias point of the mixing transistor is sufficiently low that the LO signal does not have sufficient power to turn on buffering and mixing transistors that could generate mixing products at the IF output.

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Chandler, AZ, United States of America

Fred H Bonn