Low Noise, Low Gain Drift, G = 2000
Instrumentation Amplifier
Data Sheet
AD8428
Rev. A
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FEATURES
Fixed gain of 2000
Access to internal nodes provides flexibility
Low noise: 1.5 nV/√Hz input voltage noise
High accuracy dc performance
Gain drift: 5 ppm/°C
Offset drift: 0.3 μV/°C
Gain accuracy: 0.05%
CMRR: 140 dB min
Excellent ac specifications
Bandwidth: 3.5 MHz
Slew rate: 40 V/μs
Power supply range: ±4 V to ±18 V
8-lead SOIC package
ESD protection: 5000 V (HBM)
Temperature range for specified performance:
−40°C to +85°C
Operational up to 125°C
APPLICATIONS
Sensor interface
Medical instrumentation
Patient monitoring
FUNCTIONAL BLOCK DIAGRAM
IN
IN
FI
+FIL
+
S
–V
S
AD8428
3kΩ
6kΩ 6kΩ
6kΩ 6kΩ
120kΩ
120kΩ
30.15Ω
3kΩ
OUT
REF
09731-001
Figure 1.
Table 1. Instrumentation Amplifiers by Category
1
General-
Purpose
Zero
Drift
Military
Grade
Low
Power
Low
Noise
AD8220 AD8231 AD620 AD627 AD8428
AD8221 AD8290 AD621 AD623 AD8429
AD8222 AD8293 AD524 AD8235
AD8224 AD8553 AD526 AD8236
AD8228 AD8556 AD624 AD8426
AD8295 AD8557 AD8226
AD8227
AD8420
1
See www.analog.com for the latest instrumentation amplifiers.
GENERAL DESCRIPTION
The AD8428 is an ultralow noise instrumentation amplifier
designed to accurately measure tiny, high speed signals. It
delivers industry-leading gain accuracy, noise, and bandwidth.
All gain setting resistors for the AD8428 are internal to the part
and are precisely matched. Care is taken in both the chip pinout
and layout. This results in excellent gain drift and quick settling
to the final gain value after the part is powered on.
The high CMRR of the AD8428 prevents unwanted signals
from corrupting the signal of interest. The pinout of the AD8428
is designed to avoid parasitic capacitance mismatches that can
degrade CMRR at high frequencies.
The AD8428 is one of the fastest instrumentation amplifiers
available. The circuit architecture is designed for high bandwidth
at high gain. The AD8428 uses a current feedback topology for
the initial preamplifier gain stage of 200, followed by a difference
amplifier stage of 10. This architecture results in a 3.5 MHz
bandwidth at a gain of 2000 for an equivalent gain bandwidth
product of 7 GHz.
The AD8428 pinout allows access to internal nodes between the
first and second stages. This feature can be useful for modifying
the frequency response between the two amplification stages,
thereby preventing unwanted signals from contaminating the
output results.
The performance of the AD8428 is specified over the industrial
temperature range of −40°C to +85°C. It is available in an 8-lead
plastic SOIC package.
