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Difference Amp vs INA

Hari T O0
Genius 3820 points

Dear Team,

May I know how to decide when to use a difference amplifier and when to use an instrumentation amplifier.

Regards

Hari

  • 0
    Guru 140200 points

    Hi Hari,

    a difference amplifier shows different input impedances for the +input and -input. Differential signals and common mode signals are treated differently. An instrumentation amplifier, on the other hand, offers a high degree of symmetry regarding the inputs. Furthermore, an instrumentation amplifier can provide a considerably enhanced common mode rejection.

    Kai

  • 0 in reply to kai klaas69
    TI__Guru 67971 points
    Adding to Kai's comments, since difference amplifier differential and common-mode input impedance is composed of the actual resistors, they have greatly limited magnitude typically in the range of kohm to Mohm (1e3-1e6). On the other hand, the input impedance of an instrumentation amplifier may be as high as Teraohm (1e12), thus virtually eliminating any input current, which in case of difference amplifier may materially contribute to a measurement error especially in current shunt applications measuring relatively small currents.