Approximation
Formula |
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VNOISE
= Noise voltage density, i.e. pA/sqrt(Hz)
INOISE = Noise current density, i.e.
nV/sqrt(Hz)
RS = Source resistance, i.e. 50 W
k = Boltzmann's Constant = 1.380 662 x 10-23
J/K
T = Ambient temperature in Kelvin
The example to the
right uses T = 25 °C
= 298.15 K
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Complete Non-Inverting Opamp Noise Figure Formula
(for RS = RT)
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Complete
Inverting Opamp Noise Figure Formula (for RS
= RT)
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ENI
= Input noise voltage |
IBN
= Non-inverting input noise current |
IBI
= Inverting noise current |
RS
= Source resistor |
RT
= Termination resistor |
RF
= Feedback resistor |
RG
= Gain setting resistor |