OPA735: Input resistance of OPA735 is not given datasheet of IC

Onkar Bhakare

Part Number: OPA735
Other Parts Discussed in Thread: OPA335

Hi,

I am using opa735 in my application. I need the value of its input resistance but it is not given in the datasheet of IC. Can you tell me its value?

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Onkar,

you can estimate it from the input leakage current. The input resistance is in the 10GOhm range at room temperature.

Kai

0 Marek Lis over 5 years ago in reply to kai klaas69

TI__Guru 60610 points

Adding to Kai's answer, the input common-mode resistance may be calculated from the slope of the IB vs Vcm graph: Rcm=ΔVcm/ΔIB.

Unfortunately, the graph is not shown in the OPA735 datasheet; however, you may see the trend in another zero-drift product datasheet, OPA335, shown below. From the graph below one may calculate the Rcm to be between ~100G (1E+11) at 25C to Rcm=~3V/150pA=2G (2E+9) at 125C.

0 Onkar Bhakare over 5 years ago in reply to Marek Lis

Intellectual 550 points

Thanks

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OPA735: Input resistance of OPA735 is not given datasheet of IC