Datasheet AD622 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | Low Cost Instrumentation Amplifier |
| Pages / Page | 16 / 10 — AD622. Data Sheet. Table 5. Make vs. Buy Error Budget. Total Error in ppm … |
| Revision | E |
| File Format / Size | PDF / 282 Kb |
| Document Language | English |
AD622. Data Sheet. Table 5. Make vs. Buy Error Budget. Total Error in ppm Relative to 1 V FS. Error Source
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Text Version of Document
AD622 Data Sheet
The AD622 provides greater accuracy at lower cost. The higher over temperature due to the drift mismatch of the discrete cost of the homebrew circuit is dominated in this case by the resistors. matched resistor network. One could also realize a homebrew Note that for the homebrew circuit, the LT1013 specification for design using cheaper discrete resistors that are either trimmed noise has been multiplied by √2. This is because a two op amp or hand selected to give high common-mode rejection. This type instrumentation amplifier has two op amps at its inputs, level of common-mode rejection, however, degrades significantly both contributing to the overall noise.
Table 5. Make vs. Buy Error Budget Total Error in ppm Relative to 1 V FS Error Source AD622 Circuit Calculation Homebrew Circuit Calculation AD622 Homebrew
ABSOLUTE ACCURACY at TA = 25°C Total RTI Offset Voltage, µV 125 µV + 1500 µV/10 800 µV × 2 275 1600 Input Offset Current, nA 2.5 nA × 1 kΩ 15 nA × 1 kΩ 2.5 15 CMR, dB 86 dB→50 ppm × 0.5 V (0.1% Match × 0.5 V)/10 V 25 50 Total Absolute Error 302.5 1665 DRIFT TO 85°C Gain Drift, ppm/°C (50 ppm + 5 ppm) × 60°C (50 ppm)/°C × 60°C 3300 3000 Total RTI Offset Voltage, µV/°C (1 µV/°C + 15 µV/°C /10) × 60°C 9 µV/°C × 2 × 60°C 150 1080 Input Offset Current, pA/°C 2 pA/°C × 1 kΩ × 60°C 155 pA/°C × 1 kΩ × 60°C 0.12 9.3 Total Drift Error 3450.12 4089.3 RESOLUTION Gain Nonlinearity, ppm of Full Scale 10 ppm 20 ppm 10 20 Typ 0.1 Hz to 10 Hz Voltage Noise, µV p-p 0.6 µV p-p 0.55 µV p-p × √2 0.6 0.778 Total Resolution Error 10.6 20.778 Grand Total Error 3763 5775
Rev. E | Page 10 of 16 Document Outline Features Applications Pin Configuration General Description Revision History Specifications Absolute Maximum Ratings Thermal Resistance ESD Caution Typical Performance Characteristics Theory of Operation Make vs. Buy: A Typical Application Error Budget Gain Selection Input and Output Offset Voltage Reference Terminal Input Protection RF Interference Ground Returns for Input Bias Currents Outline Dimensions Ordering Guide
The AD622 provides greater accuracy at lower cost. The higher over temperature due to the drift mismatch of the discrete cost of the homebrew circuit is dominated in this case by the resistors. matched resistor network. One could also realize a homebrew Note that for the homebrew circuit, the LT1013 specification for design using cheaper discrete resistors that are either trimmed noise has been multiplied by √2. This is because a two op amp or hand selected to give high common-mode rejection. This type instrumentation amplifier has two op amps at its inputs, level of common-mode rejection, however, degrades significantly both contributing to the overall noise.
Table 5. Make vs. Buy Error Budget Total Error in ppm Relative to 1 V FS Error Source AD622 Circuit Calculation Homebrew Circuit Calculation AD622 Homebrew
ABSOLUTE ACCURACY at TA = 25°C Total RTI Offset Voltage, µV 125 µV + 1500 µV/10 800 µV × 2 275 1600 Input Offset Current, nA 2.5 nA × 1 kΩ 15 nA × 1 kΩ 2.5 15 CMR, dB 86 dB→50 ppm × 0.5 V (0.1% Match × 0.5 V)/10 V 25 50 Total Absolute Error 302.5 1665 DRIFT TO 85°C Gain Drift, ppm/°C (50 ppm + 5 ppm) × 60°C (50 ppm)/°C × 60°C 3300 3000 Total RTI Offset Voltage, µV/°C (1 µV/°C + 15 µV/°C /10) × 60°C 9 µV/°C × 2 × 60°C 150 1080 Input Offset Current, pA/°C 2 pA/°C × 1 kΩ × 60°C 155 pA/°C × 1 kΩ × 60°C 0.12 9.3 Total Drift Error 3450.12 4089.3 RESOLUTION Gain Nonlinearity, ppm of Full Scale 10 ppm 20 ppm 10 20 Typ 0.1 Hz to 10 Hz Voltage Noise, µV p-p 0.6 µV p-p 0.55 µV p-p × √2 0.6 0.778 Total Resolution Error 10.6 20.778 Grand Total Error 3763 5775
Rev. E | Page 10 of 16 Document Outline Features Applications Pin Configuration General Description Revision History Specifications Absolute Maximum Ratings Thermal Resistance ESD Caution Typical Performance Characteristics Theory of Operation Make vs. Buy: A Typical Application Error Budget Gain Selection Input and Output Offset Voltage Reference Terminal Input Protection RF Interference Ground Returns for Input Bias Currents Outline Dimensions Ordering Guide
