[sdiy] Voltage dividers - best practice

[Seb Francis]

Antti Huovilainen wrote:
> On Sat, 2 Aug 2008, Justin Owen wrote:
>
>> When I come to laying out the PCB - would it be best practice to have 
>> individual voltage dividers providing the reference voltage at the 
>> points closest to where they're need (i.e. multiple dividers like I 
>> have now)? Or would it be better to have one reference point and have 
>> everything drawing from that? Or does it make no difference?
>
> You'd be best off using a dedicated 3-terminal voltage reference and 
> an opamp to provide one common Vref and then have all voltage dividers 
> connected to that. LM385, TLC431 or other el cheapo reference  will do 
> fine, the goal is to make the Vref independent of exact V+ value and 
> noise coupling through power supply.
>


Or if you really do just just want a V/2 reference you can just use a 
potential divider and buffer with a unity gain opamp.  Might be worth 
decoupling the reference voltage somewhere close to where it is used 
(perhaps in more than 1 place).

Seb