Data Sheet

AD8253

Rev. B | Page 21 of 24

APPLICATIONS INFORMATION

DIFFERENTIAL OUTPUT

In certain applications, it is necessary to create a differential

signal. High resolution analog-to-digital converters often require a

differential input. In other cases, transmission over a long distance

can require differential signals for better immunity to interference.

Figure 61 shows how to configure the AD8253 to output a

differential signal. An op amp, the AD8675, is used in an

output midpoint according to the equation shown in the figure.

Errors from the op amp are common to both outputs and are

thus common mode. Likewise, errors from using mismatched

resistors cause a common-mode dc offset error. Such errors are

rejected in differential signal processing by differential input

ADCs or instrumentation amplifiers.

set using a resistor divider from the ADC reference to make the

output ratiometric with the ADC.

SETTING GAINS WITH A MICROCONTROLLER

+15V

MICRO-

CONTROLLER

–15V

A0

A1

WR

+IN

–IN

10μF0.1µF

10μF0.1µF

REF

AD8253

+

–

DGND

DGND

Figure 60. Programming Gain Using a Microcontroller

+15V

–15V

A0

A1

WR

+IN

10μF

0.1μF

10μF

0.1μF

AD8253

REF

G = 1

0.1µF

4.99kΩ

4.99kΩ

AD8675

0.1µF

+15V

–15V

0V

2

2

+2.5V

–2.5V

0V

+2.5V

–2.5V

0V

TIME

AMPLITUDE

0V

TIME

AMPLITUDE

+5V

–5V

AMPLITUDE

56pF

+15V

–15V

+

–

+

–

DGND

DGND

Figure 61. Differential Output with Level Shift