Driving output of MCP601 opamp to near ground? (on single supply)

[treez]

Hello,

I need our (single supply) MCP601 opamp follower (U17 in below schematic) to be able to drive its output down to as low as about 10mV above ground….and still be operating in the linear region.

However, page 2 (near bottom) of the MCP601 datasheet states that MCP601 can only drive to within 100mV of ground..However, this is when there is a resistance to ground of 25K.
In our schematic, ,we have at least 100 times more than 25K resistance to ground, so I presume I will be able to drive the MCP601 output down to 10mV above ground?
(I presume the “VL” in the datasheet means “ground” for single supply connection?)

MCP601 datasheet:
https://ww1.microchip.com/downloads/en/devicedoc/21314g.pdf

 

[FvM]

See FIGURE 2-20 "Output Voltage Headroom vs. Output Current"

 

[treez]

thanks FvM, I see what you mean..but page 2 ("output" section) suggests under any circumstances, you cant get closer to ground than 100mV and be in the linear region.?

 

[FvM]

Depends on your understanding of "linear range". The datasheet specification refers to Aol=100dB. If you need to guarantee this open loop gain in the respective operation point, 100 mV are valid. If you can accept a lower gain, you can calculate with a smaller output voltage.

Seriously, you never get all informations from a datasheet (and neither from a simulation). At a certain point, you have to measure yourself.

 

[123jack]

FvM is right as always but a point I'd add is this is ok for one off or hobby work but if you intend to
manufacture even small runs - I'd look for a device designed to do what you need.
(an event with matched transistors in the chopper circuit of switched mode PSU's many years ago still gives nightmares...)