LMP7721: Input impedance?

Etienne Haenni

Part Number: LMP7721

Hello,

Currently, I'm design a transimpedance amplifier using the LMP7721 and I look after the input impedance (ohm and fF) of this amplifier, but no way to find these values in the datasheet.

Would it be possible to you to provide these values?

Kind regards.

over 6 years ago

0 kai klaas69 over 6 years ago

Guru 140200 points

Hi Etienne,

page 18 of datasheet of LMP7721 mentions an input capacitance of 11pF. And the input resistance is in the TOhm range. See figures 1 to 5 of datasheet.

Kai

0 Michael Steffes over 6 years ago in reply to kai klaas69

Guru 48395 points

Hi Etienne,

The original model for the LMP7721 did not seem to have any input capacitance, There has been a Jan 2019 model update that appears to capture the input C. The attached file is that new model set up for the non-inverting (Ccm only) extract. That comes out as 15pF as Kai mentioned,

Going on to another test for the Ccm+Cdm shows 20pF so the Cdm (not specified seperately in the datasheet) in the model is 5pF. Hard to tell where they got that number, but for transimpedance sims, you should use the 20pF number.

V+ input C extract for LMP7721.TSC

0 Etienne Haenni over 6 years ago in reply to Michael Steffes

Prodigy 200 points

Dear All,

Thank you for your answers. This help me a lot for my design.

Kind regards.
Etienne

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LMP7721: Input impedance?