AD8571ARZ Analog Devices Inc, AD8571ARZ Datasheet - Page 20

• Manufacturer Part Number: AD8571ARZ
• Description: IC OPAMP CHOPPER R-R 30MA 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Chopper Stabilizationr

Specifications of AD8571ARZ

• Slew Rate: 0.4 V/µs
• Amplifier Type: Chopper (Zero-Drift)
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Gain Bandwidth Product: 1.5MHz
• Current - Input Bias: 10pA
• Voltage - Input Offset: 1µV
• Current - Supply: 850µA
• Current - Output / Channel: 30mA
• Voltage - Supply, Single/dual (±): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Op Amp Type: Zero Drift
• No. Of Amplifiers: 1
• Bandwidth: 1.5MHz
• Supply Voltage Range: 2.7V To 5V
• Amplifier Case Style: SOIC
• No. Of Pins: 8
• Rail/rail I/o Type: Rail to Rail Input/Output
• Number Of Elements: 1
• Unity Gain Bandwidth Product: 1.5MHz
• Common Mode Rejection Ratio: 120dB
• Input Offset Voltage: 5uV
• Input Bias Current: 50pA
• Single Supply Voltage (typ): 3V
• Dual Supply Voltage (typ): Not RequiredV
• Voltage Gain In Db: 145dB
• Power Supply Rejection Ratio: 120dB
• Power Supply Requirement: Single
• Shut Down Feature: No
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Technology: CMOS
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC N
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Lead Free Status / Rohs Status: Compliant

AD8571/AD8572/AD8574
APPLICATIONS INFORMATION
5 V PRECISION STRAIN GAGE CIRCUIT
The extremely low offset voltage of the AD8572 makes it an ideal
amplifier for any application requiring accuracy with high gains,
such as a weigh scale or strain gage. Figure 63 shows a configura-
tion for a single-supply, precision strain gage measurement system.
The REF192 provides a 2.5 V precision reference voltage for A2.
The A2 amplifier boosts this voltage to provide a 4.0 V reference
for the top of the strain gage resistor bridge. Q1 provides the
current drive for the 350 Ω bridge network. A1 is used to amplify
the output of the bridge with the full-scale output voltage equal to
where R
Using the values given in Figure 63, the output voltage linearly
varies from 0 V with no strain to 4 V under full strain.
3 V INSTRUMENTATION AMPLIFIER
The high common-mode rejection, high open-loop gain,
and operation down to 3 V of the supply voltage make the
AD857x family an excellent op amp choice for discrete single-
supply instrumentation amplifiers. The common-mode
rejection ratio of the AD857x is greater than 120 dB, but the
CMRR of the system is also a function of the external resistor
tolerances. The gain of the difference amplifier shown in Figure 64
is given as
EQUIVALENT
NOTE:
USE 0.1% TOLERANCE RESISTORS.
V
2
OUT
LOAD
×
350Ω
CELL
B
2N2222
(
is the resistance of the load cell.
R +
4.0V
R
=
1
OR
Q1
B
V
Figure 63. 5 V Precision Strain Gage Amplifier
1
R
⎛
⎜
⎝
2
R
AD8572-B
)
3
1kΩ
R
FULL-SCALE
+
4
R
40mV
12kΩ
4
⎞
⎟
⎠
⎛
⎜
⎝
1
5V
+
A2
R
R
17.4kΩ
17.4kΩ
1
2
R1
R3
⎞
⎟
⎠
A1
2.5V
−
20kΩ
AD8572-A
V
100Ω
R2
100Ω
2
R4
⎛
⎜
⎝
6
R
R
2
1
REF192
⎞
⎟
⎠
4
2
0V TO 4V
V
OUT
3
(17)
(18)
Rev. E | Page 20 of 24
In an ideal difference amplifier, the ratio of the resistors is set
equal to
Set the output voltage of the system to
Due to finite component tolerance, the ratio between the four
resistors is not exactly equal, and any mismatch results in a
reduction of common-mode rejection from the system. Referring
to Figure 64, the exact common-mode rejection ratio can be
expressed as
In the 3-op amp instrumentation amplifier configuration shown
in Figure 65, the output difference amplifier is set to unity gain
with all four resistors equal in value. If the tolerance of the
resistors used in the circuit is given as δ, the worst-case CMRR
of the instrumentation amplifier is
Therefore, using 1% tolerance resistors results in a worst-case
system CMRR of 0.02, or 34 dB. To achieve high common-
mode rejection, either high precision resistors or an additional
trimming resistor, as shown in Figure 65, should be used. The
value of this trimming resistor should be equal to the value of
multiplied by its tolerance. For example, using 10 kΩ resistors
with 1% tolerance would require a series trimming resistor
equal to 100 Ω.
V2
V1
V
CMRR
CMRR
A
OUT
V
R
V
Figure 65. Discrete Instrumentation Amplifier Configuration
OUT
G
=
Figure 64. Using the AD857x as a Difference Amplifier
= A
= 1 +
V1
V2
R
MIN
R
=
2
1
V
IF
2R
R
(V1 − V2)
R
=
G
AD8574-B
=
R4
R3
1R4
AD8574-A
R
R
(V1 – V2)
R
R
2
2
=
1
4
3
δ
R1R4
R1
R3
R2
R1
+
, THEN V
2
R4
R2R4
−
2
R
R
R2R3
OUT
R
+
TRIM
=
R2R3
R2
R
R2
R1
AD8571/
AD8572/
AD8574
(V1 – V2)
R
AD8574-C
V
OUT
V
OUT
(19)
(20)
(21)
(22)
R