Electronics > Projects, Designs, and Technical Stuff
-0.7V rail creation for op amp
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exe:
Afaik, there was an IC that generated -0.2V across its leads. It was connected in between ground negative supply of the opamp. I can't find it. I saw it in old app notes.

But the more I think about it the less I'm sure it's possible to create such a two-terminal device (unless it's a battery).  May be I'm dreaming.
ogden:

--- Quote from: exe on January 11, 2019, 02:01:25 pm ---Afaik, there was an IC that generated -0.2V across its leads. It was connected in between ground negative supply of the opamp. I can't find it.

--- End quote ---

I did mention such already:


--- Quote from: ogden on January 10, 2019, 07:21:05 pm ---You may consider purpose-built negative bias IC like http://www.ti.com/product/LM7705

--- End quote ---
David Hess:

--- Quote from: duak on January 11, 2019, 01:17:10 am ---Blueskull, is the 2N3055 trick the one where the base-emitter junction is reverse biased to breakdown, but a small negative voltage relative to the emitter appears on the collector?
--- End quote ---

I am sure it is.  I did it with 2N3904s and while it works, optocouplers provide at least 10 times the efficiency.
TrickyNekro:
Does your ADC have a -Vref? Cause if yes you can bias the -Vref with a simple diode and resistor. Granted you lose a bit of voltage range but that can be accounted for.
Hiemal:
As an alternative you can use a 555 timer as a charge pump to create a negative voltage.

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