Circuits with a single supply voltage

AN4586

16/19

DocID026915 Rev 1

One last term has to be taken into consideration, which is the accuracy of the voltage

reference itself. This accuracy depends on the voltage reference circuits chosen. The

accuracy for each circuit is given below.

•

Voltage reference IC (e.g. TS4041): 0.5 %

•

Programmable voltage reference IC (e.g. TL1431): 0.3 % plus the accuracy of the

resistors used for the Vka setting.

•

Divider bridge: ± 2ε considering the tolerance, ε, of the resistor used

•

DAC output: depends on the DAC specifications

Example

To understand the complete contribution of each parameter, we can consider an example

with a 3-op amp instrumentation configuration and a voltage reference IC.

The worst case output voltage is as follows:

When we use Gdiff, Gcm, and Voffset as calculated in the 3-op amp instrumentation

amplifier section we get the following:

Where 0.5 % is the accuracy of the voltage reference IC.

Vout3

Gdiff

Vdiff Gcm

Vicm Voffset Vreference

++

⋅

+

⋅

=

Vreference

Vref 1

Ry

Ry Rx

+

---------------------

4

+

⎝⎠

⎛⎞ 10.5%

+

()

=