10 MHz, 20 V/μs, G = 1, 2, 4, 8 iCMOS®
Programmable Gain Instrumentation Amplifier
AD8251
FEATURES
FUNCTIONAL BLOCK DIAGRAM
DGND WR
A1
5
A0
4
Small package: 10-lead MSOP
Programmable gains: 1, 2, 4, 8
Digital or pin-programmable gain setting
Wide supply: 5 V to 15 V
2
6
LOGIC
1
–IN
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
7
OUT
10
+IN
Fast settling time: 785 ns to 0.001% (maximum)
High slew rate: 20 V/ꢀs (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
AD8251
8
3
–V
9
+V
REF
S
S
Figure 1.
25
APPLICATIONS
20
15
10
5
G = 8
G = 4
Data acquisition
Biomedical analysis
Test and measurement
G = 2
G = 1
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.
0
–5
–10
1k
100M
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 2. Gain vs. Frequency
Table 1. Instrumentation and Difference Amplifiers
by Category
High
Low
High
Mil
Low
Digital
Gain
AD6271 AD82311
Performance Cost
Voltage Grade Power
AD82201
AD8221
AD8222
AD82241
AD6231
AD85531
AD628
AD629
AD620
AD621
AD524
AD526
AD624
AD8250
AD85551
AD85561
AD85571
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
1 Rail-to-rail output.
WR
can be latched using the
input. An alternative is to use
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.
transparent gain mode where the state of logic levels at the gain
port determines the gain.
Rev. 0
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