Output

Load

Supply

ADC

V+

OUT

GND

IN-

IN+

C

BYPASS

0.01 F

m

to

0.1 F

m

+2.7V to +26V

REF

R

1

R

3

R

2

R

4

R

SHUNT

INA199A1, INA199B1

INA199A2, INA199B2

INA199A3, INA199B3

www.ti.com

SBOS469D – MAY 2009 – REVISED NOVEMBER 2012

REF INPUT IMPEDANCE EFFECTS

As with any difference amplifier, the INA199 series common-mode rejection ratio is affected by any impedance

present at the REF input. This concern is not a problem when the REF pin is connected directly to most

references or power supplies. When using resistive dividers from the power supply or a reference voltage, the

REF pin should be buffered by an op amp.

In systems where the INA199 output can be sensed differentially, such as by a differential input analog-to-digital

converter (ADC) or by using two separate ADC inputs, the effects of external impedance on the REF input can

be cancelled. Figure 23 depicts a method of taking the output from the INA199 by using the REF pin as a

reference.

Figure 23. Sensing INA199 to Cancel Effects of Impedance on the REF Input

Copyright © 2009–2012, Texas Instruments Incorporated

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Product Folder Links: INA199A1 INA199B1 INA199A2 INA199B2 INA199A3 INA199B3