Have you seen the scheme where several transistors are used in
parallel as the input stage to reduce the effect of base-spreading
resistance? If you use 4 transistors the noise is reduced by a
factor of 2, etc. I can find a PMI (now ADI) app note if you want.
73, WN6Q
"In learning about low-noise design, I've discovered that
a major contributor to lousy noise figure is a transistor's
base spreading resistance. This affects direct-conversion
receiver audio preamps, where input source Z is 50 ohms. RF preamps
too."
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Anthony Felino, Pacific Information Design
email: anthony@pacinfosb.com
telephone: (805) 730 1565, x25
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