AD622 查看數據表（PDF） - Analog Devices

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AD622

Low Cost Instrumentation Amplifier

Analog Devices 

AD622

The AD622 provides greater accuracy at lower cost. The higher

cost of the homebrew circuit is dominated in this case by the

matched resistor network. One could also realize a homebrew

design using cheaper discrete resistors that are either trimmed

or hand selected to give high common-mode rejection. This

level of common-mode rejection, however, degrades significantly

over temperature due to the drift mismatch of the discrete

resistors.

Note that for the homebrew circuit, the LT1013 specification for

noise has been multiplied by √2. This is because a two op amp

type instrumentation amplifier has two op amps at its inputs,

both contributing to the overall noise.

Table 4. Make vs. Buy Error Budget

Error Source

ABSOLUTE ACCURACY at TA = 25°C

Total RTI Offset Voltage, μV

Input Offset Current, nA

CMR, dB

DRIFT TO 85°C

Gain Drift, ppm/°C

Total RTI Offset Voltage, μV/°C

Input Offset Current, pA/°C

RESOLUTION

Gain Nonlinearity, ppm of Full Scale

Typ 0.1 Hz to 10 Hz Voltage Noise, μV p-p

AD622 Circuit Calculation Homebrew Circuit Calculation

250 μV + 1500 μV/10

2.5 nA × 1 kΩ

86 dB→50 ppm × 0.5 V

800 μV × 2

15 nA × 1 kΩ

(0.1% Match × 0.5 V)/10 V

Total Absolute Error

(50 ppm + 5 ppm) × 60°C

(2 μV/°C + 15 μV/°C /10) × 60°C

2 pA/°C × 1 kΩ × 60°C

(50 ppm)/°C × 60°C

9 μV/°C × 2 × 60°C

155 pA/°C × 1 kΩ × 60°C

Total Drift Error

10 ppm

0.6 μV p-p

20 ppm

0.55 μV p-p × √2

Total Resolution Error

Grand Total Error

Total Error in ppm

Relative to 1 V FS

AD622

Homebrew

400

2.5

25

427.5

1600

15

50

1665

3300

210

0.12

3510.12

3000

1080

9.3

4089.3

10

0.6

10.6

3948

20

0.778

20.778

5775

Rev. D | Page 10 of 16

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