Hi Folks, not quite sure this is the right place, but here it goes:
I need to design a regulated 5V reference for an op-amp, for a current source output on my arduino.
The problem is its 5V with reference to the VCC Rail and not to GND as it is typical.
I have first used a shunt regulator based on a zenner, but the voltage drifted quite a bit as the supply changed (4.90 - 5.20).
Any hints on alternative ways to achieve this?
5V reference with respect to Vcc rail? I don't follow that.
Do you mean 10V?
Mark
holmes4:
Do you mean 10V?Mark
No, I mean a multimeter from VCC to the output of the second circuit should read 5V, with a 7 to 15V supply.
Ok, I had to think a bit out of the box for this one.
So if I imagine VCC as my virtual GND and therefore my GND as the negative supply, this fits perfectly within the scope of a 79xx linear regulator.
All sorted now.
Look for single rail op-amps they only need Vcc No -ve required.
Mark
The opamp is already fed from a single supply.
I need my a reference voltage referenced to VCC, as I am measuring a high side current shunt.
Here's what I am talking about:
http://electronicdesign.com/power/what-s-difference-between-high-side-and-low-side-current-sensing
How about the Linear LT1019-5 precision voltage reference?
http://cds.linear.com/docs/en/datasheet/1019fd.pdf
Connect its Ground to Vcc and feed 12V (relative to Arduino Ground) to the IN pin. You should get Vcc+5.00 on the OUT pin.
johnwasser:
How about the Linear LT1019-5 precision voltage reference?
http://cds.linear.com/docs/en/datasheet/1019fd.pdfConnect its Ground to Vcc and feed 12V (relative to Arduino Ground) to the IN pin. You should get Vcc+5.00 on the OUT pin.
Looks good, buts its damn expensive. £8.58 in farnell ($15?) 
If you only need a reasonably well regulated 5V rather than a 0.05% precision 5.00V reference you can use a 7805 linear regulator the same way.
