Very low input voltage to opamp buffer on 5v single supply

[treez]

Hi,
The common mode range of MCP6001 does appear to be VSS-0.3V to vdd +0.3v, so I presume, if I connect it as a buffer, and put 50mV on the non inverting input, then I will get at least somewhere inside 50mV +/-7mV at the output?

(it will be on single 5v supply)

MCP6001 opamp

https://ww1.microchip.com/downloads...1U-2-4-1-MHz-Low-Power-Op-Amp-DS20001733L.pdf

 

[barry]

Where are you getting +/- 7mV? Offset voltage is +/- 4.5mV. The common mode range has nothing to do with what you're talking about; that just tells you how low an input voltage you can apply. Since you're applying 50mV, you're inside the common-mode range.

 

[KlausST]

Hi,

Why don't you amplify the signal?
It could be an improvement for further processing

Klaus

 

[danadakk]

CMOS OpAmps have an issue with non linearity due to asymmetrical Vth
curves of the input N and P mos transistors used in front end. Its small but
capable of causing significant errors in high res circuits, like A/D front ends
in DelSig applications.

Most datasheets do not discuss the problem, unfortunately. So you have
to either do some device characterization yourself, or use a part fully
documented

https://www.ti.com/lit/ds/symlink/opa320.pdf?ts=1592575246803&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FOPA320

Regards, Dana.