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Turning off an opamp based linear current regulator

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treez

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Hello,

We have a LED driver as in the attached schematic. We sometimes wish to shut it off by turning on the PNP and putting the opamp’s rail voltage on to its inverting input. We will later turn it back on again by turning off the PNP.

The opamp used is the MIC6211. The positive rail is obviously outside of its input common mode range. Some of the old opamps would malfunction if such a high voltage was placed on to one of their input pins. Do you think the MIC6211 will be OK with this?

MIC6211 datasheet:
https://ww1.microchip.com/downloads/en/DeviceDoc/mic6211.pdf
 

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  • LED driver shutdown1.pdf
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Hi,

It says nothing about "...with No Output Phase Inversion" - only one of the few op amps I know has/says so explicitly in the datasheet detailed description, with a 'scope shot and everything to show the response. The LM6464 is quite an old model, I think, but it's r2r in and out, and only 16V. From what I know (next to nothing), I'd be wary without a query to the manufacturer or it saying so somewhere (web/datasheet/selection guides/catalogues).
 
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Hi,

Without additional information about the Opamp behaviour you can't rely on it's output state.
The input is out if the specified range....

Klaus
 
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