Datasheet

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

CONNECTION DIAGRAM

8-Pin Plastic Mini-DIP (N), Cerdip (Q)

and SOIC (R) Packages

–IN

–V

+IN

OUTPUT

REF

AD620

TOP VIEW

REV. D

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

Low Cost, Low Power

Instrumentation Amplifier

AD620

FEATURES

EASY TO USE

Gain Set with One External Resistor

(Gain Range 1 to 1000}

Wide Power Supply Range (62.3 V to 618 V)

Higher Performance than Three Op Amp IA Designs

Available in 8-Pin DIP and SOIC Packaging

Low Power, 1.3 mA max Supply Current

EXCELLENT DC PERFORMANCE (“A GRADE”)

125 mV max, Input Offset Voltage (50 mV max

“B” Grade)

1 mV/8C max, Input Offset Drift

2.0 nA max, Input Bias Current

93 dB min Common-Mode Rejection Ratio (G = 10)

LOW NOISE

9 nV/√

Hz, @ 1 kHz, Input Voltage Noise

0.28 mV p-p Noise (0.1 Hz to 10 Hz)

EXCELLENT AC SPECIFICATIONS

120 kHz Bandwidth (G = 100)

15 ms 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

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700 Fax: 617/326-8703

PRODUCT DESCRIPTION

The AD620 is a low cost, high accuracy instrumentation ampli-

fier which requires only one external resistor to set gains of 1 to

1000. Furthermore, the AD620 features 8-pin SOIC and DIP

packaging that is smaller than discrete designs, and offers lower

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)

Three Op Amp IA Designs vs. AD620

SOURCE RESISTANCE – Ω

100M10k1k 10M1M100k

10,000

0.1

100

1,000

TYPICAL STANDARD

BIPOLAR INPUT

IN-AMP

AD620 SUPERßETA

BIPOLAR INPUT

IN-AMP

RTI VOLTAGE NOISE

(0.1 –10Hz) – µV p-p

G = 100

Total Voltage Noise vs. Source Resistance

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 sys-

tems, such as weigh scales and transducer interfaces. Further-

more, 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,

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.

Summary of content (16 pages)

PAGE 1
a Low Cost, Low Power Instrumentation Amplifier AD620 CONNECTION DIAGRAM FEATURES EASY TO USE Gain Set with One External Resistor (Gain Range 1 to 1000} Wide Power Supply Range (62.3 V to 618 V) Higher Performance than Three Op Amp IA Designs Available in 8-Pin DIP and SOIC Packaging Low Power, 1.
PAGE 2
AD620–SPECIFICATIONS (Typical @ +258C, VS = 615 V, and RL = 2 kV, unless otherwise noted) Model Conditions GAIN Gain Range Gain Error2 G=1 G = 10 G = 100 G = 1000 Nonlinearity, G = 1–1000 G = 1–100 Gain vs. Temperature G = 1 + (49.
PAGE 3
AD620 Model Conditions DYNAMIC RESPONSE Small Signal –3 dB Bandwidth G=1 G = 10 G = 100 G = 1000 Slew Rate Settling Time to 0.01% 10 V Step G = 1–100 G = 1000 AD620A Typ Max Min 1000 800 120 12 1.2 0.75 AD620B Typ Max Min 1000 800 120 12 1.2 0.75 15 150 Min 0.75 15 150 AD620S1 Typ Max Units 1000 800 120 12 1.2 kHz kHz kHz kHz V/µs 15 150 µs µs NOISE Voltage Noise, 1 kHz Input, Voltage Noise, e ni Output, Voltage Noise, e no RTI, 0.1 Hz to 10 Hz G=1 G = 10 G = 100–1000 Current Noise 0.
PAGE 4
AD620 ABSOLUTE MAXIMUM RATINGS 1 ORDERING GUIDE Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V Internal Power Dissipation2 . . . . . . . . . . . . . . . . . . . . . 650 mW Input Voltage (Common Mode) . . . . . . . . . . . . . . . . . . . . ± VS Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . ± 25 V Output Short Circuit Duration . . . . . . . . . . . . . . . . . Indefinite Storage Temperature Range (Q) . . . . . . . . . .
PAGE 5
AD620 Typical Characteristics (@ +258C, V = 615 V, R = 2 kV, unless otherwise noted) S L 50 2.0 SAMPLE SIZE = 360 +I B 1.0 INPUT CURRENT – nA PERCENTAGE OF UNITS 1.5 40 30 20 0.5 –I B 0 –0.5 –1.0 10 –1.5 0 –2.0 –80 –40 0 +40 +80 –75 –25 25 75 TEMPERATURE – °C INPUT OFFSET VOLTAGE – µV Figure 1. Typical Distribution of Input Offset Voltage 125 175 Figure 4. Input Bias Current vs.
PAGE 6
AD620–Typical Characteristics 1000 1s 100mV CURRENT NOISE – fA/ Hz 100 90 100 10 0% 10 1 10 100 FREQUENCY – Hz 1000 Figure 7. Current Noise Spectral Density vs. Frequency Figure 9. 0.1 Hz to 10 Hz Current Noise, 5 pA/Div RTI NOISE – 2.0 µV/div TOTAL DRIFT FROM 25°C TO 85°C, RTI – µV 100,000 10,000 FET INPUT IN-AMP 1000 100 AD620A 10 TIME – 1 sec/div 1k 10k 100k 1M SOURCE RESISTANCE – Ω 10M Figure 10. Total Drift vs. Source Resistance Figure 8a. 0.
PAGE 7
AD620 35 180 G = 10, 100, 1000 30 140 G = 1000 PSR – dB 120 100 G = 100 80 G = 10 60 G=1 20 15 10 5 G=1 40 25 BW LIMIT OUTPUT VOLTAGE – Volts p-p 160 G = 1000 G = 100 20 0.1 0 1 10 100 1k FREQUENCY – Hz 10k 100k 1k 1M 100k 1M FREQUENCY – Hz Figure 15. Large Signal Frequency Response Figure 12. Positive PSR vs. Frequency, RTI (G = 1–1000) +Vs –0.0 160 –0.
PAGE 8
AD620 OUTPUT VOLTAGE SWING – Volts p-p 30 5V VS = ±15V G = 10 1mV 100 90 20 10 10 0% 10µs 0 0 100 1k LOAD RESISTANCE – Ω 10k Figure 18. Output Voltage Swing vs. Load Resistance 5V Figure 21. Large Signal Response and Settling Time, G = 10 (0.5 mV = 001%) 1mV 20mV 100 100 90 90 10 10 0% 0% 10µs 10µs Figure 22. Small Signal Response, G = 10, RL = 2 kΩ, CL = 100 pF Figure 19. Large Signal Pulse Response and Settling Time G = 1 (0.5 mV = 0.
PAGE 9
AD620 20 20mV TO 0.01% 100 15 SETTLING TIME – µs 90 10 TO 0.1% 10 5 0% 10µs 0 0 5 10 15 OUTPUT STEP SIZE – Volts 20 Figure 27. Settling Time vs. Step Size (G = 1) Figure 24. Small Signal Pulse Response, G = 100, RL = 2 kΩ, CL = 100 pF 1000 5V 5mV 100 SETTLING TIME - µs 90 100 10 10 0% 100 µs 1 1 10 100 1000 GAIN Figure 25. Large Signal Response and Settling Time, G = 1000 (0.5 mV = 0.01%) Figure 28. Settling Time to 0.01% vs.
PAGE 10
AD620 100µV I1 2V 20µA VB 20µA I2 100 A1 90 A2 C1 10kΩ C2 10kΩ OUTPUT A3 R3 400Ω – IN R1 10kΩ R2 Q1 R4 400Ω RG 0% GAIN SENSE REF +IN Q2 10 10kΩ GAIN SENSE –VS Figure 31. Simplified Schematic of AD620 Figure 29b. Gain Nonlinearity, G = 100, RL = 10 kΩ (100 µ V = 10 ppm) 1mV THEORY OF OPERATION The AD620 is a monolithic instrumentation amplifier based on a modification of the classic three op amp approach.
PAGE 11
AD620 Make vs. Buy: A Typical Bridge Application Error Budget The AD620 offers improved performance over “homebrew” three op amp IA designs, along with smaller size, less components and 10× lower supply current. In the typical application, shown in Figure 32, a gain of 100 is required to amplify a bridge output of 20 mV full scale over the industrial temperature range of –40°C to +85°C. The error budget table below shows how to calculate the effect various error sources have on circuit accuracy.
PAGE 12
AD620 +5V ≈ 3kΩ 20kΩ 7 3 3kΩ REF 8 3kΩ 3kΩ AD620B G=100 499Ω 6 IN 5 1 2 10kΩ ADC 4 AD705 DIGITAL DATA OUTPUT AGND 20kΩ 1.3mA MAX 1.7mA 0.6mA MAX 0.10mA Figure 33. 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 scales, the AD620 is especially suited for higher resistance pressure sensors powered at lower voltages where small size and low power become more significant.
PAGE 13
AD620 Precision V-I Converter INPUT AND OUTPUT OFFSET VOLTAGE The AD620 along with another op amp and two resistors make a precision current source (Figure 35). 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 14
AD620 problems by simply tying the REF pin to the appropriate “local ground.” COMMON-MODE REJECTION Instrumentation amplifiers like the AD620 offer high CMR which is a measure of the change in output voltage when both inputs are changed by equal amounts. These specifications are usually given for a full-range input voltage change and a specified source imbalance.
PAGE 15
AD620 for these currents; therefore when amplifying “floating” input +VS – INPUT 2 1 7 +VS VOUT AD620 RG sources such as transformers, or ac-coupled sources, there must be a dc path from each input to ground as shown in Figure 40. Refer to the Instrumentation Amplifier Application Guide (free from Analog Devices) for more information regarding in amp applications.
PAGE 16
AD620 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). Plastic DIP (N-8) Package 5 0.25 (6.35) PIN 1 1 C15499b–12–4/93 8 0.31 (7.87) 4 0.30 (7.62) REF 0.39 (9.91) MAX 0.035±0.01 (0.89±0.25) 0.165±0.01 (4.19±0.25) 0.011±0.003 (0.28±0.08) 0.18±0.03 (4.57±0.76) 0.125 (3.18) MIN 0.018±0.003 (0.46±0.08) 0.10 (2.54) BSC 0.033 (0.84) NOM 15 ° 0° SEATING PLANE Cerdip (Q-8) Package 0.005 (0.13) MIN 0.055 (1.40) MAX 8 5 0.310 (7.87) 0.220 (5.59) PIN 1 1 4 0.320 (8.13) 0.290 (7.37) 0.