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10 MHz, 20 V/μs, G = 1, 2, 4, 8 iCMOS
Programmable Gain Instrumentation Amplifier
AD8251
Rev. B
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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. Specifications subject to change without notice. No
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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 V/°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 = 8 (maximum)
Low power: 4.1 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 a 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 ways (see Figure 1). A 2-bit word
sent via a bus can be latched using the
WR
input. An alternative is
to use the transparent gain mode where the state of the logic
levels at the gain port determines the gain.
FUNCTIONAL BLOCK DIAGRAM
A1 A0DGND WR
AD8251
+V
S
–V
S
REF
OUT
+IN
LOGIC
–IN
1
10
8 3
7
4562
9
06287-001
Figure 1.
25
–10
1k 100M
06287-002
FREQUENCY (Hz)
GAIN (dB)
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 Amplifiers by Category
General
Purpose
Zero Drift
Mil
Grade
Low
Power
High Speed
PGA
AD8220
1
AD8231
1
AD620 AD627
1
AD8250
AD8221 AD8553
1
AD621 AD623
1
AD8251
AD8222 AD8555
1
AD524 AD8223
1
AD8253
AD8224
1
AD8556
1
AD526
AD8228 AD8557
1
AD624
1
Rail-to-rail output.
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.
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