LMV641: LMV641 differential input of Vid principle

Pei Gong

Part Number: LMV641
Other Parts Discussed in Thread: LMV651,

Nice to meet you, could you please help to explain below parameter of LM641? why the differential input of Vid limit in ±0.3V?

could you also share the internal circuit to better understand this parameter?

Thanks for your help!

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Pei,

yes this looks a bit weird. I think it can be read this way: "The differential input voltage can be up to +/-0.3V. But please don't exceed +/-0.3V" :-)

I think it's just a typo and there should not be any value in the table below "MIN".

Kai

0 Pei Gong over 4 years ago in reply to kai klaas69

TI__Prodigy 510 points

Hi kai

Thanks for your quick respond. Could you please tell me how to obtain this differential voltage(+/-0.3V) through internal circuit or how to conduct this value?

0 kai klaas69 over 4 years ago in reply to Pei Gong

Guru 140200 points

Hi Pei,

I guess that there are two antiparallel protection diodes between the inputs.

Kai

0 Raymond Zhang1 over 4 years ago in reply to kai klaas69

TI__Guru 57741 points

Hi Pei Gong,

I think that there may be a typo in min (+/-0.3V) column in differential input requirements. It should have been left blank.

LMV651 and LMV641 are very similar, and it looks like that they are in the same family. Here is what the datasheet is specified.

Normally, the input of V+ and V- in op amp will follow each other anyway as open loop gain is high. So it is not likely that they should vary more than 300mV, unless the op amp is damaged or will be damaged (such as a large transient conditions at Op Amp's input or output pins, if they are unprotected.

Best,

Raymond

0 kai klaas69 over 4 years ago in reply to Raymond Zhang1

Guru 140200 points

Hi Pei,

and the feedback resistors will usually sufficiently limit the current. If the feedback resistors are rather low ohmic (in a non-inverting amplifier stage), an additional current limiting resistor in series to the +input can be helpful.

To furtherly discuss your circuit, you could post the schematic here.

Kai

0 Tamara M Alani over 4 years ago in reply to Pei Gong

TI__Genius 10850 points

Hi Pei Gong,

We haven't heard from you in a while. We hope the issue was resolved. I am going to close thing thread now, please reply to reopen if you have any additional questions / information.

0 Pei Gong over 4 years ago in reply to Tamara M Alani

TI__Prodigy 510 points

HI Tamara

The issue was resolved.

please close the thread.Thank you!

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LMV641: LMV641 differential input of Vid principle