Tuesday, October 9, 2018

MPF102 biasing???

Where should the Q point be? What current and what voltage? I don't know? I wonder what the manufacturer says? Time to look at the datasheet.
 The noise figure goes down with higher current. I could use 1 ma and accept the noise or go up a little and reduce noise?
Well a low drain voltage increases the noise figure? So higher drain voltage and higher drain current improve the noise figure?
Higher drain current increase power gain? so it seems higher drain current is good. Let's look a little closer.
They used a drain current of 5ma for the test.
The noise figure levels off at 4 to 8 volts depending on frequency.
They used a drain voltage of 15 volts. At 5 ma the curve is leveling off.
At 100 MHz would 5 ma and 4 volts be good choices? 
Doubling the current gives 0.25db improvement in noise figure and 4 db power gain (at 100MHz). Above 5 ma we see a point of diminishing returns.
Lower values will conserve power and would be better for battery power circuits, if we can accept the higher noise and lower gain.

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