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OPA928: and OPA2197 Asymmetric power supply

Taito Takemura
Expert 3420 points
Part Number: OPA928
Other Parts Discussed in Thread: OPA2197,

Tool/software:

Hi team,

I'd like to use OPA928 and OPA2197 with power supply +33.5V / -2.5V and Vcm from 0V to 20V. I don't think there is any problem because the datasheet shows max Vs voltage of single supply is 36V and max Vs voltage of dual supply is +/- 18V. Could you please let me know if there is anything wrong with my understanding?

Also, I plan to use the OPA928 and OPA2197 as TIA or voltage follower. Would there be any problems with this?

OPA928 datasheet

OPA2197

Thank you for your help.

Regards,

Taito Takemura

  • 0
    TI__Guru 68541 points

    There would be no problem using OPA928 and OPA2197 on +33.5V and -2.5V supplies with 0V<Vcm<20V.  With their low IB, they both meant to be use for application like TIA or buffering (follower) high impedance sources.  

  • 0 in reply to Marek Lis
    TI__Expert 3420 points

    HI Marek,

    Thank you for your answer.

    Could you please another question about Ib value? Is it correct to assume that the value of Ib for Vcm when +33.5V and -2.5V are applied to the power supply is the same as Figure 5-27 shifted?

    In other words, to calculate Ib when +33.5V and -2.5V are applied using Fig.5-27, should I shift Vcm by -15.5V (= -18V -(-2.5V))?  I mean Ib at Vcm 0V (=-2.5V +2.5V) corresponds to Ib at Vcm -15.5V (=-18V+2.5V)  and Ib at Vcm 20V (=-2.5V +22.5V) corresponds to Ib at Vcm 4.5V (=-18V+22.5V) 

      Red Vcm is Vcm when +33.5V and -2.5V are applied to the power supply

      Blue Vcm is Vcm when +18V and -18V are applied to the power supply

  • 0 in reply to Taito Takemura
    TI__Guru 68541 points

    For your -2.5/+33.5V supplies, the horizontal scale in Fig 5-27 must be shifted up by +15.5V (33.5V-18V) - see below.