Multiple precision references

[dark]

Hi,

My analog circuit require different reference voltages for ADCs ,subtraction, virtual GNDs .These are 10V, 5V , 2.5V . If I integrate different ICs for this the cost shoots up . I need your advise if its allright to use a single 10V reference generator IC and then use resistive dividers and op amp buffers thereafter . Any pitfalls?

Regards

 

[BrownOut]

Regulator chips aren't expensive. Spend a couple bucks and do it right.

 

[MikeMl]

...I need your advise if its allright to use a single 10V reference generator IC and then use resistive dividers and op amp buffers thereafter . Any pitfalls?

It is preferable to use a single precision 10V reference, and then to derive the others off that using a voltage divider. That way, everything tracks better, as long as you use good quality metal-film resistors.

Voltage dividers work fine as long as they only have to supply the input bias current to opamps. If you need to draw current off any voltage divider tap, then use an opamp voltage follower between the tap and where the current flows....

 

[Roff]

When you consider component tolerances and temperature coefficients, it may or may not be cheaper to use resistors (and op amps if needed) instead of individual reference ICs. Maybe you guys have this information memorized, but I would have to research it.

 

[dark]

Hi,
I think the divider will also introduce Resistor noise ?. Is this an issue? .

 

[ericgibbs]

Hi,
I think the divider will also introduce Resistor noise ?. Is this an issue? .

hi,
As Mikel points out its often important that the tapped voltages track, so using a precision MF [metal film] resistor divider chain will give good results and low noise.

As stated, if the individual voltage taps are 'loaded' you should add a non inv buffer OPA at each tap.

 

[mneary]

When you consider component tolerances and temperature coefficients, it may or may not be cheaper to use resistors (and op amps if needed) instead of individual reference ICs. Maybe you guys have this information memorized, but I would have to research it.

I would buffer all the references, so that part is resolved for me. Then it comes down to how costly will references of 5.0 and 2.5V be, compared to four matched resistors? (I would use a resistor array, precision less important than matching.) Op amps would be chosen primarily for low offset voltage.

 

[dark]

Thanks for putting me on the right track . I would like to ask if its benificial to remove trim pots from these divider networks?

 

[ericgibbs]

Thanks for putting me on the right track . I would like to ask if its benificial to remove trim pots from these divider networks?

I have used Cermet multi-turn trim pots in dividers without problems.

 

[dark]

I have used Cermet multi-turn trim pots in dividers without problems.

hi ,
Can you tell something regarding BOURNS 3296 series ?.

 

[ericgibbs]

hi ,
Can you tell something regarding BOURNS 3296 series ?.

Im not quite sure what you mean.?
I have used Bourns pots on lots of analog projects.

Datasheets here:
Search Results | Farnell United Kingdom

 

[dark]

Im not quite sure what you mean.?
I have used Bourns pots on lots of analog projects.

Datasheets here:
Search Results | Farnell United Kingdom

I mean are the Cermet multi-turn trim pots (I havnt used ) are different from 3296 . I concern regarding trim pots contact point as a future culprit for noise induction.