AD8224 Datasheet, PDF (1/27 Pages) Analog Devices – Precision, Dual-Channel, JFET Input Rail-to-Rail Instrumentation Amplifier

Preliminary Technical Data
Precision, Dual-Channel, JFET Input
Rail-to-Rail Instrumentation Amplifier
AD8224
FEATURES
Two channels in a small 4 mm × 4 mm LFCSP
Low input currents
10 pA maximum input bias current (B grade)
0.6 pA maximum input offset current (B grade)
High CMRR
100 dB CMRR (minimum), G = 10 (B grade)
80 dB CMRR (minimum) to 5 kHz, G = 1 (B grade)
Excellent ac specifications and low power
1.5 MHz bandwidth (G = 1)
14 nV/√Hz input noise (1 kHz)
Slew rate 2 V/μs
750 μA quiescent supply current per amplifier (maximum)
Versatility
Rail-to-rail output
Input voltage range to below negative supply rail
4 kV ESD protection
4.5 V to 36 V single supply
±2.25 V to ±18 V dual supply
Gain set with single resistor (G = 1 to 1000)
APPLICATIONS
Medical instrumentation
Precision data acquisition
Transducer interface
Differential drive for
High resolution input ADCs
Remote sensors
GENERAL DESCRIPTION
The AD8224 is the first single-supply junction field effect
transistor (JFET) input instrumentation amplifier available in
the space-saving 16-lead, 4 mm×4 mm LFCSP. It requires the
same board area as a typical single instrumentation amplifier,
yet doubles the channel density and offers a lower cost per
channel without compromising performance.
Designed to meet the needs of high performance, portable
instrumentation, the AD8224 has a minimum common-mode
rejection ratio (CMRR) of 86 dB at dc and a minimum CMRR
of 80 dB at 5 kHz for G = 1. Maximum input bias current is
10 pA and typically remains below 300 pA over the entire
industrial temperature range. Despite the JFET inputs, the
AD8224 typically has a noise corner of only 10 Hz.
With the proliferation of mixed-signal processing, the number of
power supplies required in each system has grown.
Rev. PrB
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FUNCTIONAL BLOCK DIAGRAM
16 15 14 13
AD8224
–IN1 1
RG1 2
RG1 3
+IN1 4
12 –IN2
11 RG2
10 RG2
9 +IN2
5 678
Figure 1. 4mm × 4 mm LFCSP
Table 1. In Amps and Difference Amplifiers by Category
High
Low
Perform. Cost
High
Volt.
Mil
Low
Digital
Grade Power Gain
AD8220¹ AD8553¹ AD628 AD620 AD627¹ AD8555¹
AD8221 AD623¹ AD629 AD621
AD8556¹
AD8222
AD524
AD8557¹
AD8224¹
AD526
AD624
1 _{Rail-to-rail output.}
Designed to alleviate this problem, the AD8224 can operate on a
±18 V dual supply, as well as on a single +5 V supply. The device’s
rail-to-rail output stage maximizes dynamic range on the low
voltage supplies common in portable applications. Its ability to run
on a single 5 V supply eliminates the need for higher voltage, dual
supplies. The AD8224 draws a maximum of 750 μA of quiescent
current per amplifier, making it ideal for battery-powered devices.
In addition, the AD8224 can be configured as a single-channel,
differential output instrumentation amplifier. Differential
outputs provide high noise immunity, which can be useful when
the output signal must travel through a noisy environment, such
as with remote sensors. The configuration can also be used to
drive differential input ADCs.
For a single-channel version, use the AD8220 device.
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