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Joined: 11/19/2015(UTC) Posts: 2 
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Hello,
My Trident 1.2V arrived without the shunt transistor. The component was not inside the bag so check because the fault is at the very origin of the part.
BTW no problem because I had the right part in stock and I soldered it by myself.
Sorry if I am wrong but the voltage at the inverting input of the opamp violates the common-mode voltage input range on the negative side. Being single supply the voltage on IN- should not be lower than ground + 1.5V (refer to OPA209 DS). Measured value is 1.17V for the 1.2V output version.
How can I expect a predictable behaviour from the opamp?
Thank you for your answer :)
D.
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Which version of the Trident are you using? The latest has 2 resistors: SMD and through hole. If the through hole resistor is not in the bag, it's likely already in place (SMD).
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Rank: Member
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Guy read my post again, I wrote the shunt transistor was missing. Not resistors. :) Edited by user Thursday, November 19, 2015 8:12:32 PM(UTC)
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Sorry, but I had a hard time understanding what you're writing. My best bet was that instead of transistor you meant resistor, because I fail to see how the module could possibly pass Brians' testing without the transistor.
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As for the question on the common mode voltage - this is one of the reasons we went with this particular op amp. It actually works quite well with 1.2V at V- (actually testing and measuring) because of the total correction mode. For most circuits I would never try it. We simply haven't found anything better to use yet. :)
Cheers!
Russ
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