AD8223BRM-RL 查看數據表（PDF） - Analog Devices

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AD8223BRM-RL

Single Supply, Rail-to-Rail, Low Cost Instrumentation Amplifier

Analog Devices 

AD8223

Preliminary Technical Data

APPLICATIONS INFORMATION

+VS

+2.5V TO +6V

+

0.1µF 10µF

VIN RG

+

RG

OUTPUT

RG REF

–

VOUT

REF (INPUT)

VIN RG

+VS

+3V TO +12V

+

0.1µF 10µF

+

RG

OUTPUT

RG REF

–

VOUT

REF (INPUT)

0.1µF +10µF

–2.5V TO –6V

–VS

A. DUAL SUPPLY

B. SINGLE SUPPLY

Figure 34. Basic Connections

BASIC CONNECTION

OUTPUT BUFFERING

Figure 34 shows the basic connection circuit for the AD8223.

The +VS and −VS terminals are connected to the power supply.

The supply can be either bipolar (VS = ±2.5 V to ±12.5 V) or

single supply (−VS = 0 V, +VS = +3.0 V to +25 V). Power

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.

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

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

0.1µF

5V

VIN RG

+

AD8223

–

REF

0.1µF

+

OP113

–

VOUT

DIFFERENTIAL OUTPUT

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

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

AD8223

–IN

REF 20kΩ

+OUT

VREF

20kΩ

–

+

OP1177

–OUT

Figure 35. Differential Output Using Op Amp

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.

100Ω

–INPUT

AD8031

+INPUT

+VS

2

RG 1

7

2

RG

AD8223 6

2

8

3

5

4

–VS

Figure 37. Common-Mode Shield Driver

VOUT

REFERENCE

Rev. PrA | Page 16 of 20

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