AD8223

Preliminary Technical Data

Rev.

PrA | Page 16 of 20

APPLICATIONS INFORMATION

+2.5V TO +6V

REF (INPUT)

–2.5V TO –6V

REF

OUTPUT

+3V TO +12V

+

–

+

–

10µF

0.1µF

10µF

0.1µF

10µF

0.1µF

+

+

+

REF (INPUT)

REF

OUTPUT

A. DUAL SUPPLY

B. SINGLE SUPPLY

Figure 34. Basic Connections

BASIC CONNECTION

Figure 34 shows the basic connection circuit for the AD8223.

supplies should be capacitively decoupled close to the device’s

power pins. 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 35 shows how to create a differential output in-amp. A

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

20k

Ω

+

–

OP1177

+OUT

–OUT

20k

Ω

Figure 35. 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, the AD8223 output should be

buffered with a precision single-supply op amp such as the

while driving a load as small as 600 Ω.

5V

AD8223

REF

OP113

5V

+

–

0.1µF

0.1µF

+

–

Figure 36. 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 37 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

100

Ω

AD8223

AD8031

REFERENCE

2

2

7

6

5

4

1

8

3

Figure 37. Common-Mode Shield Driver