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Low Cost, Low Power
a
Instrumentation Amplifier
AD620
CONNECTION DIAGRAM
FEATURES
EASY TO USE
8-Lead Plastic Mini-DIP (N), Cerdip (Q)
Gain Set with One External Resistor
and SOIC (R) Packages
(Gain Range 1 to 1000)
Wide Power Supply Range (62.3 V to 618 V)
1 8 R
R
G G
Higher Performance than Three Op Amp IA Designs
Available in 8-Lead DIP and SOIC Packaging –IN 2 7 +V
S
Low Power, 1.3 mA max Supply Current
+IN 3 6 OUTPUT
EXCELLENT DC PERFORMANCE (“B GRADE”)
–V 4
5 REF
S
AD620
50 mV max, Input Of
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AD620–SPECIFICATIONS (Typical @ +258C, V = 615 V, and R = 2 kV, unless otherwise noted) S L 1 AD620A AD620B AD620S Model Conditions Min Typ Max Min Typ Max Min Typ Max Units GAIN G = 1 + (49.4 k/R ) G Gain Range 1 10,000 1 10,000 1 10,000 2 Gain Error V = ±10 V OUT G = 1 0.03 0.10 0.01 0.02 0.03 0.10 % G = 10 0.15 0.30 0.10 0.15 0.15 0.30 % G = 100 0.15 0.30 0.10 0.15 0.15 0.30 % G = 1000 0.40 0.70 0.35 0.50 0.40 0.70 % Nonlinearity, V = –10 V to +10 V, OUT G = 1–1000 R = 10 kΩ 10 40 10 40 10 4
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AD620 1 AD620A AD620B AD620S Model Conditions Min Typ Max Min Typ Max Min Typ Max Units DYNAMIC RESPONSE Small Signal –3 dB Bandwidth G = 1 1000 1000 1000 kHz G = 10 800 800 800 kHz G = 100 120 120 120 kHz G = 1000 12 12 12 kHz Slew Rate 0.75 1.2 0.75 1.2 0.75 1.2 V/μs Settling Time to 0.01% 10 V Step G = 1–100 15 15 15 μs G = 1000 150 150 150 μs NOISE 2 2 Voltage Noise, 1 kHz Total RTI Noise = (e )+(e /G) no ni Input, Voltage Noise, e 913 9 13 913 nV/√Hz ni Output, Voltage Noise, e 72 100
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AD620 1 ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±18 V 2 Model Temperature Ranges Package Options* Internal Power Dissipation . . . . . . . . . . . . . . . . . . . . . 650 mW Input Voltage (Common Mode) . . . . . . . . . . . . . . . . . . . . ±V S AD620AN –40°C to +85°C N-8 Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . .±25 V AD620BN –40°C to +85°C N-8 Output Short Circuit Duration . . . .
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AD620 (@ +258C, V = 615 V, R = 2 kV, unless otherwise noted) Typical Characteristics S L 50 2.0 SAMPLE SIZE = 360 1.5 40 1.0 +I B –I B 0.5 30 0 20 –0.5 –1.0 10 –1.5 0 –2.0 –80 –40 0 +40 +80 –75 –25 25 75 125 175 INPUT OFFSET VOLTAGE – mV TEMPERATURE – 8C Figure 3. Typical Distribution of Input Offset Voltage Figure 6. Input Bias Current vs. Temperature 50 2 SAMPLE SIZE = 850 40 1.5 30 1 20 0.5 10 0 0 –1200 –600 0 +600 +1200 051234 INPUT BIAS CURRENT – pA WARM-UP TIME – Minutes Figure 4. Typical
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AD620–Typical Characteristics 1000 100 10 1 1000 10 100 FREQUENCY – Hz Figure 9. Current Noise Spectral Density vs. Frequency Figure 11. 0.1 Hz to 10 Hz Current Noise, 5 pA/Div 100,000 10,000 FET INPUT IN-AMP 1000 AD620A 100 10 TIME – 1 SEC/DIV 1k 10k 100k 1M 10M SOURCE RESISTANCE – V Figure 12. Total Drift vs. Source Resistance Figure 10a. 0.1 Hz to 10 Hz RTI Voltage Noise (G = 1) +160 G = 1000 +140 G = 100 +120 G = 10 +100 G = 1 +80 +60 +40 +20 0 0.1 1 10 100 1k 10k 100k 1M TIME – 1 SEC/DIV F
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AD620 180 35 G = 10, 100, 1000 160 30 140 25 G = 1000 120 G = 1 20 100 G = 100 15 80 G = 10 10 60 G = 1 5 40 G = 1000 G = 100 20 0 0.1 1 10 100 1k 10k 100k 1M 1k 10k 100k 1M FREQUENCY – Hz FREQUENCY – Hz Figure 17. Large Signal Frequency Response Figure 14. Positive PSR vs. Frequency, RTI (G = 1–1000) +V –0.0 180 S 160 –0.5 –1.0 140 –1.5 120 100 G = 1000 80 +1.5 G = 100 60 +1.0 G = 10 40 +0.5 G = 1 20 –V +0.0 S 0 5 10 15 20 0.1 1 10 100 1k 10k 100k 1M SUPPLY VOLTAGE 6 Volts FREQUENCY – Hz
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AD620 30 .... .... .... .... .... .... .... .... .... .... V = 615V S G = 10 20 10 .... .... .... .... .... .... .... .... .... .... 0 0 100 1k 10k LOAD RESISTANCE – V Figure 20. Output Voltage Swing vs. Load Resistance Figure 23. Large Signal Response and Settling Time, G = 10 (0.5 mV = 001%) .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... Figur
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AD620 20 .... .... .... .... .... .... .... .... ........ 15 TO 0.01% TO 0.1% 10 5 .... .... .... .... .... .... .... .... ........ 0 02 5 10 150 OUTPUT STEP SIZE – Volts Figure 26. Small Signal Pulse Response, G = 100, Figure 29. Settling Time vs. Step Size (G = 1) R = 2 kΩ, C = 100 pF L L 1000 .... .... .... .... .... .... .... .... .... .... 100 10 .... .... .... .... .... .... .... .... .... .... 1 1 10 100 1000 GAIN Figure 27. Large Signal Response and Settling Time, Figure 30. Settling Tim
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AD620 20mA V I1 20mA I2 B .... .... .... .... .... .... .... .... ........ A1 A2 10kV C1 C2 10kV A3 OUTPUT 10kV 10kV R3 R1 R2 REF 400V – IN Q1 Q2 +IN R4 R 400V G .... .... .... .... .... .... .... .... ........ GAIN GAIN SENSE SENSE –V S Figure 33. Simplified Schematic of AD620 Figure 31b. Gain Nonlinearity, G = 100, R = 10 kΩ L (100 μV = 10 ppm) THEORY OF OPERATION The AD620 is a monolithic instrumentation amplifier based on a modification of the classic three op amp approach. Absolute value tr
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AD620 Make vs. Buy: A Typical Bridge Application Error Budget systems, absolute accuracy and drift errors are by far the most The AD620 offers improved performance over “homebrew” significant contributors to error. In more complex systems with three op amp IA designs, along with smaller size, fewer compo- an intelligent processor, an autogain/autozero cycle will remove all nents and 10´ lower supply current. In the typical application, absolute accuracy and drift errors leaving only the resoluti
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AD620 +5V 20kV 7 3 3kV 3kV REF 8 G=100 AD620B 6 IN DIGITAL 499V 3kV 3kV 5 10kV DATA ADC 1 OUTPUT 4 2 AGND AD705 20kV 0.6mA 1.7mA 0.10mA 1.3mA MAX MAX Figure 35. A Pressure Monitor Circuit which Operates on a +5 V Single Supply Pressure Measurement Medical ECG Although useful in many bridge applications such as weigh The low current noise of the AD620 allows its use in ECG scales, the AD620 is especially suitable for higher resistance monitors (Figure 36) where high source resistances of 1 MΩ or
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AD620 Precision V-I Converter INPUT AND OUTPUT OFFSET VOLTAGE The AD620, along with another op amp and two resistors, makes The low errors of the AD620 are attributed to two sources, a precision current source (Figure 37). The op amp buffers the input and output errors. The output error is divided by G when reference terminal to maintain good CMR. The output voltage referred to the input. In practice, the input errors dominate at V of the AD620 appears across R1, which converts it to a X high ga
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AD620 COMMON-MODE REJECTION GROUNDING Instrumentation amplifiers like the AD620 offer high CMR, Since the AD620 output voltage is developed with respect to the which is a measure of the change in output voltage when both potential on the reference terminal, it can solve many grounding inputs are changed by equal amounts. These specifications are problems by simply tying the REF pin to the appropriate “local usually given for a full-range input voltage change and a speci- ground.” fied source imb
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AD620 GROUND RETURNS FOR INPUT BIAS CURRENTS sources such as transformers, or ac-coupled sources, there must Input bias currents are those currents necessary to bias the input be a dc path from each input to ground as shown in Figure 42. transistors of an amplifier. There must be a direct return path Refer to the Instrumentation Amplifier Application Guide (free for these currents; therefore, when amplifying “floating” input from Analog Devices) for more information regarding in amp application
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AD620 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). Plastic DIP (N-8) Package 0.430 (10.92) 0.348 (8.84) 8 5 0.280 (7.11) 0.240 (6.10) 14 0.325 (8.25) 0.300 (7.62) 0.060 (1.52) PIN 1 0.015 (0.38) 0.195 (4.95) 0.210 (5.33) 0.115 (2.93) MAX 0.130 0.160 (4.06) (3.30) MIN 0.115 (2.93) 0.015 (0.381) SEATING 0.022 (0.558) 0.100 0.070 (1.77) 0.008 (0.204) PLANE (2.54) 0.014 (0.356) 0.045 (1.15) BSC Cerdip (Q-8) Package 0.055 (1.4) 0.005 (0.13) MAX MIN 8 5 0.310 (7.87) 0.220 (5.59) 1 4 PIN 1 0
