AD627ARZ-R7 datasheet(17/24 Pages) AD

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AD627

Rev. D | Page 17 of 24

Table 7. Maximum Gain for Low Common-Mode, Single-Supply Applications

VIN

REF Pin

Supply Voltage

RG (1% Tolerance)

Resulting Maximum Gain

Output Swing WRT 0 V

±100 mV, VCM = 0 V

2 V

5 V to 15 V

28.7 kΩ

12.0

0.8 V to 3.2 V

±50 mV, VCM = 0 V

2 V

5 V to 15 V

10.7 kΩ

23.7

0.8 V to 3.2 V

±10 mV, VCM = 0 V

2 V

5 V to 15 V

1.74 kΩ

119.9

0.8 V to 3.2 V

V− = 0 V, V+ = 0 V to 1 V

1 V

10 V to 15 V

78.7 kΩ

7.5

1 V to 8.5 V

V− = 0 V, V+ = 0 mV to 100 mV

1 V

5 V to 15 V

7.87 kΩ

1 V to 4.1 V

V− = 0 V, V+ = 0 mV to 10 mV

1 V

5 V to 15 V

787 Ω

259.1

1 V to 3.6 V

Table 8. RTI Error Sources

Maximum Total RTI Offset Error (μV)

Maximum Total RTI Offset Drift (μV/°C)

Total RTI Noise (nV/√Hz)

Gain

AD627A

AD627B

AD627A

AD627B

AD627A /AD627B

450

250

+10

350

200

+20

300

175

3.5

1.5

+50

270

160

3.2

1.2

+100

270

155

3.1

1.1

+500

252

151

+1000

251

151

Table 7 gives values for the maximum gain for various single-

supply input conditions. The resulting output swings refer to

0 V. To maximize the available gain and output swing, set the

voltages on the REF pins to either 2 V or 1 V. In most cases,

there is no advantage to increasing the single supply to greater

than 5 V (the exception is an input range of 0 V to 1 V).

OUTPUT BUFFERING

The AD627 is designed to drive loads of 20 kΩ or greater but

can deliver up to 20 mA to heavier loads at lower output voltage

swings (see Figure 10). If more than 20 mA of output current is

required at the output, buffer the AD627 output with a precision

op amp, such as the OP113. Figure 40 shows this for a single

supply. This op amp can swing from 0 V to 4 V on its output

while driving a load as small as 600 Ω.

VIN RG

+VS

–VS

AD627

0.1µF

–VS

VOUT

REF

0.1µF

OP113

Figure 40. Output Buffering

INPUT AND OUTPUT OFFSET ERRORS

The low errors of the AD627 are attributed to two sources,

input and output errors. The output error is divided by G when

referred to the input. In practice, input errors dominate at high

gains and output errors dominate at low gains. The total offset

error for a given gain is calculated as

Total Error RTI = Input Error + (Output Error/Gain)

(5)

Total Error RTO = (Input Error × G) + Output Error

(6)

RTI offset errors and noise voltages for different gains are listed

in Table 8.

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