This Jfet lists noise figure as 2.1 dB, how do I turn that into v/rtHz ? Is the reference a 50 ohm resistor? So 3dB would be twice the voltage noise density of a 50 ohm resistor?
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Thx, George H.
Noise figure and Volts/rtHz
Sep 18, 2019
5 Replies
That was likely measured at 100 MHz with optimal narrowband tuned matching networks on input and output, so there's no clear correlation to equivalent voltage noise.
Buy something else, properly specified.
Well the other jfets (that aren't EOL) look noisy. like this
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or have a noise figure
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I already bought the cph3190... Hey it came really fast from DK. They now have an option for USPS shipping. It's cheaper and faster than UPS ground.
ordered Friday, here on Monday.
George H.
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** The noise figure graph shows 1dB, rel 1kohm.Equates to 12% more noise voltage than the resistor alone.
So: Noise of 1k ohms at room temp = 4.03 nVrtHz
Total noise = 4.5 nVrtHz
Noise fet = sqrt(20-16) = 2 nVrtHz.
.... Phil
Noise is a power thing. Doubling the noise voltage is 6 db . Doubling noise power is 3 db
Huh thanks Phil. George H.
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