Datasheet

ManualsBrandsANALOG DEVICES ManualsLinear ICsLinear IC - In-amp InAmp SOIC 8

Low Cost Low Power

Instrumentation Amplifier

AD620

Rev. H

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However, no responsibility is assumed by Analog Devices for its use, nor for any

infringements of patents or other rights of third parties that may result from its use.

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FEATURES

Easy to use

Gain set with one external resistor

(Gain range 1 to 10,000)

Wide power supply range (±2.3 V to ±18 V)

Higher performance than 3 op amp IA designs

Available in 8-lead DIP and SOIC packaging

Low power, 1.3 mA max supply current

Excellent dc performance (B grade)

50 μV max, input offset voltage

0.6 μV/°C max, input offset drift

1.0 nA max, input bias current

100 dB min common-mode rejection ratio (G = 10)

Low noise

9 nV/√Hz @ 1 kHz, input voltage noise

0.28 μV p-p noise (0.1 Hz to 10 Hz)

Excellent ac specifications

120 kHz bandwidth (G = 100)

15 μs settling time to 0.01%

APPLICATIONS

Weigh scales

ECG and medical instrumentation

Transducer interface

Data acquisition systems

Industrial process controls

Battery-powered and portable equipment

CONNECTION DIAGRAM

–IN

–V

+IN

OUTPUT

REF

AD620

TOP VIEW

00775-0-001

Figure 1. 8-Lead PDIP (N), CERDIP (Q), and SOIC (R) Packages

PRODUCT DESCRIPTION

The AD620 is a low cost, high accuracy instrumentation

amplifier that requires only one external resistor to set gains of

1 to 10,000. Furthermore, the AD620 features 8-lead SOIC and

DIP packaging that is smaller than discrete designs and offers

lower power (only 1.3 mA max supply current), making it a

good fit for battery-powered, portable (or remote) applications.

The AD620, with its high accuracy of 40 ppm maximum

nonlinearity, low offset voltage of 50 μV max, and offset drift of

0.6 μV/°C max, is ideal for use in precision data acquisition

systems, such as weigh scales and transducer interfaces.

Furthermore, the low noise, low input bias current, and low power

of the AD620 make it well suited for medical applications, such

as ECG and noninvasive blood pressure monitors.

The low input bias current of 1.0 nA max is made possible with

the use of Superϐeta processing in the input stage. The AD620

works well as a preamplifier due to its low input voltage noise of

9 nV/√Hz at 1 kHz, 0.28 μV p-p in the 0.1 Hz to 10 Hz band,

and 0.1 pA/√Hz input current noise. Also, the AD620 is well

suited for multiplexed applications with its settling time of 15 μs

to 0.01%, and its cost is low enough to enable designs with one

in-amp per channel.

Table 1. Next Generation Upgrades for AD620

Part Comment

AD8221 Better specs at lower price

AD8222 Dual channel or differential out

AD8226 Low power, wide input range

AD8220 JFET input

AD8228 Best gain accuracy

AD8295 +2 precision op amps or differential out

AD8429 Ultra low noise

0 5 10 15 20

30,000

5,000

10,000

15,000

20,000

25,000

TOTAL ERROR, PPM OF FULL SCALE

SUPPLY CURRENT (mA)

AD620A

3 OP AMP

IN-AMP

(3 OP-07s)

00775-0-002

Figure 2. Three Op Amp IA Designs vs. AD620

Downloaded from Arrow.com.

Summary of content (20 pages)

PAGE 1
Low Cost Low Power Instrumentation Amplifier AD620 FEATURES CONNECTION DIAGRAM Weigh scales ECG and medical instrumentation Transducer interface Data acquisition systems Industrial process controls Battery-powered and portable equipment –IN 2 7 +VS +IN 3 6 –VS 4 AD620 RG OUTPUT 5 REF Figure 1.
PAGE 2
AD620 TABLE OF CONTENTS Specifications .....................................................................................3 RF Interference............................................................................15 Absolute Maximum Ratings ............................................................5 Common-Mode Rejection.........................................................16 ESD Caution ..................................................................................5 Grounding..............
PAGE 3
AD620 SPECIFICATIONS Typical @ 25°C, VS = ±15 V, and RL = 2 kΩ, unless otherwise noted. Table 2. AD620A Parameter GAIN Gain Range Gain Error2 G=1 G = 10 G = 100 G = 1000 Nonlinearity G = 1–1000 G = 1–100 Gain vs. Temperature VOLTAGE OFFSET Input Offset, VOSI Overtemperature Average TC Output Offset, VOSO Overtemperature Average TC Offset Referred to the Input vs.
PAGE 4
AD620 AD620A AD620B Parameter Conditions Min Typ Max Common-Mode Rejection Ratio DC to 60 Hz with 1 kΩ Source Imbalance VCM = 0 V to ± 10 V G=1 73 90 G = 10 93 110 G = 100 110 130 G = 1000 110 130 OUTPUT Output Swing RL = 10 kΩ VS = ±2.3 V −VS + +VS − 1.2 to ± 5 V 1.1 Overtemperature −VS + 1.4 +VS − 1.3 VS = ±5 V −VS + 1.2 +VS − 1.4 to ± 18 V Overtemperature −VS + 1.6 +VS – 1.5 Short Circuit Current ±18 DYNAMIC RESPONSE Small Signal –3 dB Bandwidth G=1 1000 G = 10 800 G = 100 120 G = 1000 12 Slew Rate 0.
PAGE 5
AD620 ABSOLUTE MAXIMUM RATINGS Table 3.
PAGE 6
AD620 TYPICAL PERFORMANCE CHARACTERISTICS (@ 25°C, VS = ±15 V, RL = 2 kΩ, unless otherwise noted.) 2.0 50 SAMPLE SIZE = 360 1.5 INPUT BIAS CURRENT (nA) PERCENTAGE OF UNITS 40 30 20 10 1.0 +IB –I B 0.5 0 –0.5 –1.0 –40 0 40 80 INPUT OFFSET VOLTAGE (μV) –2.0 –75 –25 25 75 TEMPERATURE (°C) 125 175 00775-0-008 –80 00775-0-005 0 5 00775-0-009 –1.5 Figure 6. Input Bias Current vs. Temperature Figure 3. Typical Distribution of Input Offset Voltage 2.
PAGE 7
AD620 10 1 10 100 FREQUENCY (Hz) 1000 00775-0-014 100 00775-0-011 CURRENT NOISE (fA/ Hz) 1000 Figure 12. 0.1 Hz to 10 Hz Current Noise, 5 pA/Div Figure 9. Current Noise Spectral Density vs. Frequency TOTAL DRIFT FROM 25°C TO 85°C, RTI (μV) 10,000 FET INPUT IN-AMP 1000 AD620A 100 10 1k 10k 100k 1M SOURCE RESISTANCE (Ω) 10M 00775-0-015 TIME (1 SEC/DIV) 00775-0-012 RTI NOISE (2.0μV/DIV) 100,000 Figure 13. Total Drift vs. Source Resistance Figure 10. 0.
PAGE 8
AD620 180 35 160 30 G = 100 80 G = 10 60 G=1 10 1 100 1k FREQUENCY (Hz) 10k 100k 10 1M 0 G = 1000 1k 10k 100k FREQUENCY (Hz) Figure 15. Positive PSR vs. Frequency, RTI (G = 1−1000) 160 –0.5 INPUT VOLTAGE LIMIT (V) (REFERRED TO SUPPLY VOLTAGES) +VS –0.0 140 PSR (dB) 120 G = 1000 80 G = 100 60 G = 10 G=1 1 10 100 1k FREQUENCY (Hz) 10k 100k 1M 00775-0-018 40 20 0.1 +1.5 +1.0 +0.
PAGE 9
AD620 .... .... .... .... .... .... .... .... .... .... VS = ±15V G = 10 20 10 0 0 100 1k LOAD RESISTANCE (Ω) 10k Figure 21. Output Voltage Swing vs. Load Resistance 00775-0-026 .... .... .... .... .... .... .... .... .... .... 00775-0-023 OUTPUT VOLTAGE SWING (V p-p) 30 Figure 24. Large Signal Response and Settling Time, G = 10 (0.5 mV = 0.01%) .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... .... ..
PAGE 10
AD620 20 .... .... .... .... .... .... .... .... ........ SETTLING TIME (μs) 15 TO 0.01% TO 0.1% 10 0 5 10 OUTPUT STEP SIZE (V) 20 00775-0-032 00775-0-029 0 1000 00775-0-033 5 .... .... .... .... .... .... .... .... ........ 15 Figure 30. Settling Time vs. Step Size (G = 1) Figure 27. Small Signal Pulse Response, G = 100, RL = 2 kΩ, CL = 100 pF 1000 SETTLING TIME (μs) .... .... .... .... .... .... .... .... .... .... 100 10 00775-0-030 .... .... .... .... .... .... .... .... .... ...
PAGE 11
AD620 10kΩ * INPUT 10V p-p .... .... .... .... .... .... .... .... ........ 1kΩ 10T 10kΩ 100k Ω VOUT +VS 1kΩ 2 100 Ω 7 1 G = 1000 G=1 AD620 G = 100 G = 10 .... .... .... .... .... .... .... .... ........ 49.9Ω 499 Ω 5.49k Ω 00775-0-035 8 3 5 4 –VS *ALL RESISTORS 1% TOLERANCE Figure 33. Gain Nonlinearity, G = 100, RL = 10 kΩ (100 μV = 10 ppm) Figure 35. Settling Time Test Circuit .... .... .... .... .... .... .... .... ........ 00775-0-036 .... .... .... .... .... .... .... .... ....
PAGE 12
AD620 THEORY OF OPERATION The input transistors Q1 and Q2 provide a single differentialpair bipolar input for high precision (Figure 36), yet offer 10× lower input bias current thanks to Superϐeta processing. Feedback through the Q1-A1-R1 loop and the Q2-A2-R2 loop maintains constant collector current of the input devices Q1 and Q2, thereby impressing the input voltage across the external gain setting resistor RG.
PAGE 13
AD620 Note that for the homebrew circuit, the OP07 specifications for input voltage offset and noise have been multiplied by √2. This is because a three op amp type in-amp has two op amps at its inputs, both contributing to the overall input error. Regardless of the system in which it is being used, the AD620 provides greater accuracy at low power and price. In simple systems, absolute accuracy and drift errors are by far the most significant contributors to error.
PAGE 14
AD620 5V 3kΩ 3kΩ 3kΩ 3kΩ 20kΩ 7 3 REF 8 AD620B G = 100 499Ω 6 5 1 IN 10kΩ ADC 4 2 20kΩ 1.7mA AD705 AGND 0.6mA MAX 0.10mA 00775-0-042 1.3mA MAX DIGITAL DATA OUTPUT Figure 38.
PAGE 15
AD620 Precision V-I Converter INPUT AND OUTPUT OFFSET VOLTAGE The AD620, along with another op amp and two resistors, makes a precision current source (Figure 40). The op amp buffers the reference terminal to maintain good CMR. The output voltage, VX, of the AD620 appears across R1, which converts it to a current. This current, less only the input bias current of the op amp, then flows out to the load. The low errors of the AD620 are attributed to two sources, input and output errors.
PAGE 16
AD620 signal according to the following relationship: +VS – INPUT FilterFreq DIFF = FilterFreq CM = 1 2πR(2C D + C C ) 100Ω 1 2πRC C AD648 RG 100Ω AD620 VOUT –VS REFERENCE 00775-0-046 where CD ≥10CC. + INPUT CD affects the difference signal. CC affects the common-mode signal. Any mismatch in R × CC degrades the AD620 CMRR. To avoid inadvertently reducing CMRR-bandwidth performance, make sure that CC is at least one magnitude smaller than CD.
PAGE 17
AD620 +VS GROUND RETURNS FOR INPUT BIAS CURRENTS – INPUT Input bias currents are those currents necessary to bias the input transistors of an amplifier. There must be a direct return path for these currents. Therefore, when amplifying “floating” input sources, such as transformers or ac-coupled sources, there must be a dc path from each input to ground, as shown in Figure 46, Figure 47, and Figure 48.
PAGE 18
AD620 AD620ACHIPS INFORMATION Die size: 1803 μm × 3175 μm Die thickness: 483 μm Bond Pad Metal: 1% Copper Doped Aluminum To minimize gain errors introduced by the bond wires, use Kelvin connections between the chip and the gain resistor, RG, by connecting Pad 1A and Pad 1B in parallel to one end of RG and Pad 8A and Pad 8B in parallel to the other end of RG. For unity gain applications where RG is not required, Pad 1A and Pad 1B must be bonded together as well as the Pad 8A and Pad 8B.
PAGE 19
AD620 OUTLINE DIMENSIONS 0.400 (10.16) 0.365 (9.27) 0.355 (9.02) 5 1 4 5.00 (0.1968) 4.80 (0.1890) 0.280 (7.11) 0.250 (6.35) 0.240 (6.10) 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.100 (2.54) BSC 0.060 (1.52) MAX 0.210 (5.33) MAX 0.015 (0.38) MIN 0.150 (3.81) 0.130 (3.30) 0.115 (2.92) SEATING PLANE 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 4.00 (0.1574) 3.80 (0.1497) 0.195 (4.95) 0.130 (3.30) 0.115 (2.92) 0.015 (0.38) GAUGE PLANE 0.430 (10.92) MAX 0.005 (0.13) MIN 0.25 (0.0098) 0.10 (0.
PAGE 20
AD620 ORDERING GUIDE Model1 AD620AN AD620ANZ AD620BN AD620BNZ AD620AR AD620ARZ AD620AR-REEL AD620ARZ-REEL AD620AR-REEL7 AD620ARZ-REEL7 AD620BR AD620BRZ AD620BR-REEL AD620BRZ-RL AD620BR-REEL7 AD620BRZ-R7 AD620ACHIPS AD620SQ/883B 1 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −55°C t