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Noise Figure of a Balanced Amplifier

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93413245

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Hi everyone,
I was wondering if you could help me prove that noise figure of a balanced amplifier equals the average of noise figures of the individual amplifiers, i.e. F = (Fa+Fb)/2 where Fa and Fb are the noise figures of the individual amplifiers.
Thanks in advance
 

vfone

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A balanced amplifier configuration provides better reliability, linearity, stability, and wider bandwidth compared to a single-ended amplifier.
But by definition (due to using the inherent input balun or quadrature coupler) the overall noise figure of a balance amplifier is higher than a single-ended amplifier.
 

jiripolivka

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Noise figure is defined independently from line structure or impedance. Unfortunately most of test RF equipment operates with unsymmetric 50 Ohms, and other structures and impedances can be used only with adapters that can be lossy.
One can design noise sources in symmetrical lines as well as power meters for output power evaluation.

So to measure noise parameters in your situation, use adapters and discount their loss from measurements. Then there will be no problem with real noise figure of a symmetrical or balanced amplifier.
 

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