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OPA2234U　INPUT IMPEDANCE

Seishin
Genius 4135 points

Hi,

I want to know the input impedance(TYP) in whole temperature range .

Could you please give me information on that?（Approximate value）

Best regards,
Seishin

  • 0
    TI__Guru 74331 points

    Seishin,

    By definition the common-mode input resistance is the change of the input bias current, IB, with the change in the input common-mode voltage:

    Rin_cm=ΔVcm/ΔIB

    Therefore, you may use the Input Bias Current vs Input Common-Mode Voltage graphs shown in datasheet to calculate Rin value for different supply voltages, Vs -  see below:

    Rin_cm (Vs=+/-15V)= ΔVcm/ΔIB = 30V/5nA=6Gohm

    Rin_cm (Vs=+5V)= ΔVcm/ΔIB = 4V/1.6nA=2.5Gohm

    Rin_cm (Vs=+2.7V)= ΔVcm/ΔIB = 2V/0.8nA=2.5Gohm

    Since the input bias current does not vary significantly with temperature (see below), the input resistance will likewise hardly change over temp.

    Also, the approximate value of the input impedance is given in the datasheet table -  see below: