THS6002

DUAL DIFFERENTIAL LINE DRIVERS AND RECEIVERS

SLOS202D– JANUARY 1998– REVISED JULY 1999

28

POST OFFICE BOX 655303

APPLICATION INFORMATION

noise calculations and noise figure

Noise can cause errors on very small signals. This is especially true for the receiver amplifiers which are

generally used for amplifying small signals coming over a transmission line. The noise model for current

feedback amplifiers (CFB) is the same as voltage feedback amplifiers (VFB). The only difference between the

two is that the CFB amplifiers generally specify different current noise parameters for each input while VFB

amplifiers usually only specify one noise current parameter. The noise model is shown in Figure 54. This model

includes all of the noise sources as follows:

_

+

RF

RS

RG

eRg

eRf

eRs

en

IN+

Noiseless

IN–

eni

eno

Figure 54. Noise Model

e

ni +

en

2

) IN )

R

S

2

) IN–

R

F ø

R

G

2

) 4kTRs ) 4kT RF ø RG

Where:

k = Boltzmann’s constant = 1.380658

T = temperature in degrees Kelvin (273 +

°C)

R

F

R

G

(Noninverting Case)