AD622ARZ-R7 Analog Devices Inc, AD622ARZ-R7 Datasheet - Page 10

• Manufacturer Part Number: AD622ARZ-R7
• Description: IC,Instrumentation Amplifier,SINGLE,SOP,8PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD622ARZ-R7

• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• Slew Rate: 1.2 V/µs
• -3db Bandwidth: 1MHz
• Current - Input Bias: 2nA
• Voltage - Input Offset: 60µV
• Current - Supply: 900µA
• Current - Output / Channel: 18mA
• Voltage - Supply, Single/dual (±): ±2.6 V ~ 18 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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
Table 4. Make vs. Buy Error Budget
Error Source
ABSOLUTE ACCURACY at T
DRIFT TO 85°C
RESOLUTION
Total RTI Offset Voltage, μV
Input Offset Current, nA
CMR, dB
Gain Drift, ppm/°C
Total RTI Offset Voltage, μV/°C
Input Offset Current, pA/°C
Gain Nonlinearity, ppm of Full Scale
Typ 0.1 Hz to 10 Hz Voltage Noise, μV p-p
A
= 25°C
AD622 Circuit Calculation
250 μV + 1500 μV/10
2.5 nA × 1 kΩ
86 dB→50 ppm × 0.5 V
(50 ppm + 5 ppm) × 60°C
(2 μV/°C + 15 μV/°C /10) × 60°C
2 pA/°C × 1 kΩ × 60°C
10 ppm
0.6 μV p-p
Rev. D | Page 10 of 16
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.
Homebrew Circuit Calculation
800 μV × 2
15 nA × 1 kΩ
(0.1% Match × 0.5 V)/10 V
Total Absolute Error
(50 ppm)/°C × 60°C
9 μV/°C × 2 × 60°C
155 pA/°C × 1 kΩ × 60°C
Total Drift Error
20 ppm
0.55 μV p-p × √2
Total Resolution Error
Grand Total Error
Total Error in ppm
Relative to 1 V FS
AD622
400
2.5
25
427.5
3300
210
0.12
3510.12
10
0.6
10.6
3948
1600
3000
1080
9.3
4089.3
0.778
Homebrew
15
50
1665
20
20.778
5775