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OPA810: Input impedance for differential mode

Ryuuichi machida
Guru 11935 points
Part Number: OPA810
Other Parts Discussed in Thread: OPA863

Hello,

According to datasheet of OPA810, this describes only spec for input impedance case of "common mode".
On the other hand, case of another opamp (Ex OPA863), there are description for both "common mode" and "differential mode" input.

Do you mean that opamps which do NOT describe "differential mode" input impedance should NOT be used differential circuit such as subtraction circuit ?

BR,
 

  • 0
    TI__Expert 8400 points

    Hi Ryuuichi, 

    You can absolutely use both amplifiers for difference amplifier circuits like a subtractor. The differential input impedance is a little bit of a confusing spec as that is the impedance between the inputs with no feedback connected. In a normal amplifier circuit, the loop-gain of the circuit will cause the impedance between the input to effectively be very high which is why many datasheets to not list a differential value. 

    Best, 

    Jacob