AD8421 Datasheet, PDF (1/28 Pages) Analog Devices – 3 nV/√Hz, Low Power

Data Sheet
FEATURES
Low power
2.3 mA maximum supply current
Low noise
3.2 nV/√Hz maximum input voltage noise at 1 kHz
200 fA/√Hz current noise at 1 kHz
Excellent ac specifications
10 MHz bandwidth (G = 1)
2 MHz bandwidth (G = 100)
0.6 μs settling time to 0.001% (G = 10)
80 dB CMRR at 20 kHz (G = 1)
35 V/μs slew rate
High precision dc performance (AD8421BRZ)
94 dB CMRR minimum (G = 1)
0.2 μV/°C maximum input offset voltage drift
1 ppm/°C maximum gain drift (G = 1)
500 pA maximum input bias current
Inputs protected to 40 V from opposite supply
±2.5 V to ±18 V dual supply (5 V to 36 V single supply)
Gain set with a single resistor (G = 1 to 10,000)
APPLICATIONS
Medical instrumentation
Precision data acquisition
Microphone preamplification
Vibration analysis
Multiplexed input applications
ADC driver
GENERAL DESCRIPTION
The AD8421 is a low cost, low power, extremely low noise, ultralow
bias current, high speed instrumentation amplifier that is ideally
suited for a broad spectrum of signal conditioning and data
acquisition applications. This product features extremely high
CMRR, allowing it to extract low level signals in the presence of
high frequency common-mode noise over a wide temperature
range.
The 10 MHz bandwidth, 35 V/μs slew rate, and 0.6 μs settling
time to 0.001% (G = 10) allow the AD8421 to amplify high speed
signals and excel in applications that require high channel count,
multiplexed systems. Even at higher gains, the current feedback
architecture maintains high performance; for example, at G = 100,
the bandwidth is 2 MHz and the settling time is 0.8 μs. The
AD8421 has excellent distortion performance, making it suitable
for use in demanding applications such as vibration analysis.
Rev. 0
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3 nV/√Hz, Low Power
Instrumentation Amplifier
AD8421
PIN CONNECTION DIAGRAM
–IN 1
R_G 2
R_G 3
+IN 4
AD8421
8 +V_S
7 V_OUT
6 REF
5 –V_S
TOP VIEW
(Not to Scale)
Figure 1.
10µ
G = 100
1µ
BEST AVAILABLE
7mA LOW NOISE IN-AMP
100n
BEST AVAILABLE
1mA LOW POWER IN-AMP
10n
AD8421
1n
100
R_S NOISE ONLY
1k
10k
100k
1M
SOURCE RESISTANCE, R_S (Ω)
Figure 2. Noise Density vs. Source Resistance
The AD8421 delivers 3 nV/√Hz input voltage noise and
200 fA/√Hz current noise with only 2 mA quiescent current,
making it an ideal choice for measuring low level signals. For
applications with high source impedance, the AD8421 employs
innovative process technology and design techniques to provide
noise performance that is limited only by the sensor.
The AD8421 uses unique protection methods to ensure robust
inputs while still maintaining very low noise. This protection
allows input voltages up to 40 V from the opposite supply rail
without damage to the part.
A single resistor sets the gain from 1 to 10,000. The reference
pin can be used to apply a precise offset to the output voltage.
The AD8421 is specified from −40°C to +85°C and has typical
performance curves to 125°C. It is available in 8-lead MSOP
and SOIC packages.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
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