LMH6552: Regarding Noise Figure & Noise

Hello Shivakant,

The best way would probably be to simulate your circuit on SPICE.

Best,

Hasan Babiker

I have all those calculators somewhere but would need your circuit (R values) gain of 1 is not good on NF. Normally, if you can be ac coupled with gain, I use an input balun to improve noise figure. Have written a number of articles on that topic - I can look for those also if you need them. 

Of course noise figure (NF) is defined in the context of a source impedance noise - usually matched at the input but not always - what are you using?

The lowest noise will be the active match approach with an FDA, no shunt termination at input. that would be for single to diff.

Hi Shivakant,

can you post a schematic?

Kai

Hi Kai,

Please find my design for gain = 1 V/V of LMH6553.

In that case i want to know it's Noise figure.

Please have a look of my design which is replica of following Tina schematic:

Well Noise Figure is not defined unless you are coming from some source impedance (the plots of NF indicate a 50ohm system) - I think what you are actually wanting it the input referred spot noise for the FDA stage? You also changed to the LMH6553, there is no spot noise plot in that datasheet, but spec lines (no idea what the 1/f corners are) This is a CFA FDA so the current noise is high. 

Anyway, using your resistor values it will have 7.2nV input referred (at the output of the ADA4899. ) So that will definitely dominate over the ADA4899 output noise of about 2nV