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A Iarge percentage of microwave field-effect transistors (FET's) are shown to act as a broad-band artificial resistor with a resistance of about 25 Omega when their drain is connected to their gate. The resistance appears between the gate-drain lead and the source lead. This resistance can be raised to 50 Omega with its reactive components eliminated over a reasonable bandwidth by using a matching transmission line of the proper impedance and a length near a quarter-wave at midband. An HFET- 1000 constructed in this configuration showed an impedance of 18+-3 Omega over an octave bandwidth, and when transformed with a 30-Omega quarter-wave transmission line produced a resistance of 51+-1 Omega from 8 to 13 GHz. A noise analysis shows that, at some frequencies, some FET's in this configuration will produce artificial resistors with an effective noise temperature as low as 67 K.
Microwave Theory and Techniques, IEEE Transactions on (Volume:31 , Issue: 1 )
Date of Publication: Jan. 1983