Wide Supply Range, Micropower, Rail-to-Rail Instrumentation Amplifier Data Sheet AD8420 FEATURES PIN CONFIGURATION AD8420 Maximum supply current: 90 A NC 1 8 V Minimum CMRR: 100 dB OUT +IN 2 7 FB + Drives heavy capacitive loads: ~700 pF IN 3 + 6 REF Rail-to-rail output TOP VIEW V +V 4 5 S S (Not to Scale) Input voltage range goes below ground Figure 1. Gain set with 2 external resistors Can achieve low gain drift at any gain Very wide power supply range 1 Single supply: 2.7 V to 36 V Table 1. Instrumentation Amplifiers by Category Dual supply: 2.7 V to 18 V General Military Low Digital Purpose Zero Drift Grade Power Gain Bandwidth (G = 100): 2.5 kHz Input voltage noise: 55 nV/Hz AD8221, AD8222 AD8231 AD620 AD8420 AD8250 High dc precision AD8220, AD8224 AD8290 AD621 AD8235 AD8251 Maximum offset voltage: 125 V AD8236 Maximum offset drift: 1 V/C AD8226, AD8227 AD8293G80, AD524 AD627 AD8253 AD8293G160 Maximum differential input voltage: 1 V AD8228 AD8553 AD526 AD8226 AD8231 8-lead MSOP package AD8227 APPLICATIONS AD8295, AD8224 AD8556 AD624 AD623 Bridge amplifiers AD8557 AD8223 Pressure measurement 1 See www.analog.com for the latest instrumentation amplifiers. Medical instrumentation Portable data acquisition Multichannel systems GENERAL DESCRIPTION The AD8420 is a low cost, micropower, wide supply range, Single-supply operation, micropower current consumption, and instrumentation amplifier with a rail-to-rail output and a novel rail-to-rail output swing make the AD8420 ideal for battery- architecture that allows for extremely flexible design. It is optimized powered applications. Its rail-to-rail output stage maximizes to amplify small differential voltages in the presence of large dynamic range when operating from low supply voltages. Dual- common-mode signals. supply operation (15 V) and low power consumption make the AD8420 ideal for a wide variety of applications in medical The AD8420 is based on an indirect current feedback architecture or industrial instrumentation. that gives it an excellent input common-mode range. Unlike conventional instrumentation amplifiers, the AD8420 can easily The AD8420 is available in an 8-lead MSOP package. Performance amplify signals at or even slightly below ground without requiring is specified over the full temperature range of 40C to +85C, dual supplies. The AD8420 has rail-to-rail output, and the output and the device is operational from 40C to +125C. voltage swing is completely independent of the input common- mode voltage. Rev. A Document Feedback 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20122015 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. 09945-001AD8420 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Gain Accuracy ............................................................................ 20 Applications ....................................................................................... 1 Input Voltage Range ................................................................... 20 Pin Configuration ............................................................................. 1 Input Protection ......................................................................... 20 General Description ......................................................................... 1 Layout .......................................................................................... 21 Revision History ............................................................................... 2 Driving the Reference Pin ......................................................... 21 Specif icat ions ..................................................................................... 3 Input Bias Current Return Path ............................................... 22 Absolute Maximum Ratings ............................................................ 7 Radio Frequency Interference (RFI) ........................................ 22 Thermal Resistance ...................................................................... 7 Output Buffering ........................................................................ 23 ESD Caution .................................................................................. 7 Applications Information .............................................................. 24 Pin Configuration and Function Descriptions ............................. 8 AD8420 in Electrocardiography (ECG) .................................. 24 Typical Performance Characteristics ............................................. 9 Classic Bridge Circuit ................................................................ 25 Theory of Operation ...................................................................... 19 4 mA to 20 mA Single-Supply Receiver .................................. 25 Architec ture ................................................................................. 19 Outline Dimensions ....................................................................... 26 Setting the Gain .......................................................................... 19 Ordering Guide .......................................................................... 26 REVISION HISTORY 1/15Rev. 0 to Rev. A Changes to Features Section............................................................ 1 Changes to Specifications Section .................................................. 3 Changes to Quiescent Current Parameter, Table 2 ...................... 4 Changes to Common-Mode Rejection Ratio (CMRR) Parameter, Table 3 and Quiescent Current Parameter, Table 3 ......... 5 Changes to ESD Parameter, Table 4 ............................................... 7 Changes to Figure 9, Figure 11, Figure 13, and Figure 14 ......... 10 Changes to Figure 15, Figure 16 Caption, Figure 18 Caption, and Figure 20 Caption .................................................................... 11 Changes to Figure 38 ...................................................................... 14 Change to Figure 40 Caption ........................................................ 15 Changes to Figure 56 Caption ....................................................... 17 Changes to Figure 57 Caption ....................................................... 18 Changes to Figure 58 and Architecture Section ......................... 19 Changes to Gain Accuracy Section .............................................. 20 Changes to Driving the Reference Pin Section ........................... 21 Changes to Output Buffering Section .......................................... 23 Changes to 4 mA to 20 mA Single-Supply Receiver Section .... 25 3/12Revision 0: Initial Version Rev. A Page 2 of 26