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Wrong balanced line receiver information in ADA4075 data sheet

Question asked by DanLavry on Aug 16, 2013
Latest reply on Aug 22, 2013 by DanLavry

On page 19 of the ADA4075-2 data sheet, there is a circuit called "Balanced Line Driver.


The whole page is one big wrong thing.


The first thing that caught my eye is the equation for (high degree of CMRR). When plugging the values of R1, R2, R3, and R4 into the equation It yields 0dB improovment.


So I looked at the circuit itself, and it is just wrong. Resistors The "R7 and R8 and capacitor C1 branch" are connected between three low impedance output - The output of A1 and the signal sources marked as +IN and -IN.. Thus the current running through R8 and R7 (through C1) serve no purpose other than demand more current from the inputs, for no reason at all. OPamp A3, resistors R7, R8, R9, R10 and C1 do nothing to accommodate better CMRR. That part of the circuit does nothing other than increase the current that the inputs have to supply. 


The OPamp itself is very fine, and most of the data is just fine. But this whole page is should be deleted or altered to show a circuit that works,


Dan Lavry

Lavry Engineering