Programmable Gain Instrumentation Amplifier

AD8251

Rev. 0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibilityis assumedbyAnalogDevicesforitsuse,norforanyinfringements of patents or other

rightsofthirdpartiesthatmayresultfromitsuse.Specificationssubjecttochangewithoutnotice.No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.

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

Tel: 781.329.4700

www.analog.com

Fax: 781.461.3113

©2007 Analog Devices, Inc. All rights reserved.

FEATURES

Small package: 10-lead MSOP

Programmable gains: 1, 2, 4, 8

Digital or pin-programmable gain setting

Wide supply: ±5 V to ±15 V

Excellent dc performance

High CMRR: 98 dB (minimum), G = 8

Low gain drift: 10 ppm/°C (maximum)

Low offset drift: 1.8 μV/°C (maximum), G = 8

Excellent ac performance

Fast settling time: 785 ns to 0.001% (maximum)

High slew rate: 20 V/μs (minimum)

Low distortion: −110 dB THD at 1 kHz,10 V swing

High CMRR over frequency: 80 dB to 50 kHz (minimum)

Low noise: 18 nV/√Hz, G = 10 (maximum)

Low power: 4 mA

APPLICATIONS

Data acquisition

Biomedical analysis

Test and measurement

GENERAL DESCRIPTION

The AD8251 is an instrumentation amplifier with digitally

programmable gains that has GΩ input impedance, low output

noise, and low distortion, making it suitable for interfacing with

sensors and driving high sample rate analog-to-digital converters

(ADCs). It has high bandwidth of 10 MHz, low THD of −110 dB,

and fast settling time of 785 ns (maximum) to 0.001%. Offset

drift and gain drift are guaranteed to 1.8 μV/°C and 10 ppm/°C,

respectively, for G = 8. In addition to its wide input common

voltage range, it boasts a high common-mode rejection of 80 dB

at G = 1 from dc to 50 kHz. The combination of precision dc

performance coupled with high speed capabilities makes the

AD8251 an excellent candidate for data acquisition. Furthermore,

this monolithic solution simplifies design and manufacturing

and boosts performance of instrumentation by maintaining a

tight match of internal resistors and amplifiers.

The AD8251 user interface consists of a parallel port that allows

users to set the gain in one of two different ways (see Figure 1

for the functional block diagram). A 2-bit word sent via a bus

can be latched using the WR input. An alternative is to use

transparent gain mode where the state of logic levels at the gain

port determines the gain.

FUNCTIONAL BLOCK DIAGRAM

A1

A0

DGND WR

AD8251

REF

OUT

+IN

LOGIC

10

8

3

7

4

5

6

2

9

Figure 1.

25

–10

1k

100M

FREQUENCY (Hz)

10k

100k

1M

10M

20

15

10

5

0

–5

G = 1

G = 2

G = 4

G = 8

Figure 2. Gain vs. Frequency

Table 1. Instrumentation and Difference Amplifiers

by Category

High

Performance

Low

Cost

High

Voltage

Mil

Grade

Low

Power

Digital

Gain

AD82201

AD6231

AD628

AD620

AD6271

AD82311

AD8221

AD85531

AD629

AD621

AD8250

AD8222

AD524

AD85551

AD82241

AD526

AD85561

AD624

AD85571

The AD8251 is available in a 10-lead MSOP package and is

specified over the −40°C to +85°C temperature range, making it

an excellent solution for applications where size and packing

density are important considerations.