LM9044: Differential input and Common mode input range

Hello Sunney,

Regarding your LM9044 questions:

And Vdiff is always mentioned as 0 to 1V in datasheet. if Vdiff is less than 0V then the output is always zero as LM9044 is not powered with dual power supply. Please confirm.

• Yes, the Electrical Characteristics specified VDIFF is 0 ≤ VDIFF ≤ 1V

Case1:

Vin(+) = 1V

Vin(-) = 0V

V.cm = [Vin(+) - Vin(-)]/2 = (1-0)/2 = 0.5

V.diff = Vin(+) - Vin(-) = 1-(0) = 1

• Yes, that is correct

Case2:

Vin(+) = 0V

Vin(-) = 1V

V.cm = [Vin(+) - Vin(-)]/2 = (0-1)/2 = -0.5

V.diff = Vin(+) - Vin(-) = 0-1 = -1

• Yes, that is correct. Even though the LM9044 has a common-mode range of −3V ≤ VCM ≤ +1V, a +1 V voltage applied to the inverting input would try to drive the output to a negative voltage which can't be done with a single positive supply device. The 0 ≤ VDIFF ≤ 1V range assures that won't happen.

Regards, Thomas

Precision Amplifiers Applications Engineering