AD8223

Rev. 0 | Page 17 of 20

APPLICATIONS INFORMATION

+2V TO +12V

REF (INPUT)

–2V TO –12V

REF

OUTPUT

+3V TO +24V

+

–

+

–

10µF

0.1µF

10µF

0.1µF

10µF

0.1µF

+

+

+

REF (INPUT)

REF

OUTPUT

A. DUAL SUPPLY

B. SINGLE SUPPLY

Figure 36. Basic Connections

BASIC CONNECTION

Figure 36 shows the basic connection circuit for the AD8223.

be capacitively decoupled close to the power pins of the device.

For best results, use surface-mount 0.1 μF ceramic chip capacitors

and 10 μF electrolytic tantalum capacitors.

The input voltage, which can be either single-ended (tie either

−IN or +IN to ground) or differential, is amplified by the

programmed gain. The output signal appears as the voltage

difference between the output pin and the externally applied

voltage on the REF input.

DIFFERENTIAL OUTPUT

Figure 37 shows how to create a differential output in-amp. An

OP1177 op amp creates the inverted output. Because the op

amp drives the AD8223 reference pin, the AD8223 can still

ensure that the differential voltage is correct. Errors from the

op amp or mismatched resistors are common to both outputs

and are thus common mode. These common-mode errors

should be rejected by the next device in the signal chain.

+IN

–IN

REF

AD8223

20kΩ

+

–

OP1177

+OUT

–OUT

20kΩ

Figure 37. Differential Output Using Op Amp

OUTPUT BUFFERING

The AD8223 is designed to drive loads of 10 kΩ or greater. If

the load is less than this value, buffer the AD8223 output with a

precision single-supply op amp such as the OP113. This op amp

can swing from 0 V to 4 V on its output while driving a load as

small as 600 Ω.

5V

AD8223

REF

OP113

5V

+

–

0.1µF

0.1µF

+

–

Figure 38. Output Buffering

CABLES

Receiving from a Cable

In many applications, shielded cables are used to minimize

noise; for best CMR over frequency, the shield should be

properly driven. Figure 39 shows an active guard drive that

is configured to improve ac common-mode rejection by

bootstrapping the capacitances of input cable shields, thus

minimizing the capacitance mismatch between the inputs.

2

–INPUT

+INPUT

100Ω

AD8223

AD8031

REFERENCE

2

2

7

6

5

4

1

8

3

Figure 39. Common-Mode Shield Driver