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PDF AD8674 Data sheet ( Hoja de datos )
| Número de pieza | AD8674 | |
| Descripción | Low Input Bias Current Operational Amplifiers | |
| Fabricantes | Analog Devices | |
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Data Sheet
Precision, Very Low Noise, Low Input
Bias Current Operational Amplifiers
AD8671/AD8672/AD8674
FEATURES
Very low noise: 2.8 nV/√Hz, 77 nV p-p
Wide bandwidth: 10 MHz
Low input bias current: 12 nA max
Low offset voltage: 75 μV max
High open-loop gain: 120 dB min
Low supply current: 3 mA typ per amplifier
Dual-supply operation: ±5 V to ±15 V
Unity-gain stable
No phase reversal
APPLICATIONS
PLL filters
Filters for GPS
Instrumentation
Sensors and controls
Professional quality audio
GENERAL DESCRIPTION
The AD8671/AD8672/AD8674 are very high precision amplifiers
featuring very low noise, very low offset voltage and drift, low
input bias current, 10 MHz bandwidth, and low power
consumption. Outputs are stable with capacitive loads of over
1000 pF. Supply current is less than 3 mA per amplifier at 30 V.
The AD8671/AD8672/AD8674’s combination of ultralow noise,
high precision, speed, and stability is unmatched. The MSOP
version of the AD8671/AD8672 requires only half the board
space of comparable amplifiers.
Applications for these amplifiers include high quality PLL
filters, precision filters, medical and analytical instrumentation,
precision power supply controls, ATE, data acquisition, and
precision controls as well as professional quality audio.
The AD8671/AD8672 are specified over the extended industrial
temperature range (−40°C to +125°C), and the AD8674 is specified
over the industrial temperature range (−40°C to +85°C).
The AD8671/AD8672 are available in the 8-lead SOIC and
8-lead MSOP packages. The AD8674 is available in 14-lead
SOIC and 14-lead TSSOP packages.
Surface-mount devices in MSOP packages are available in tape
and reel only.
PIN CONFIGURATIONS
NC 1
8 NC
–IN 2 AD8671 7 V+
+IN 3 TOP VIEW 6 OUT
(Not to Scale)
V– 4
5 NC
NC = NO CONNECT
Figure 1. 8-Lead SOIC_N (R-8) and 8-Lead MSOP (RM-8)
OUT A 1
8 V+
–IN A 2 AD8672 7 OUT B
+IN A 3 TOP VIEW 6 –IN B
(Not to Scale)
V– 4
5 +IN B
Figure 2. 8-Lead SOIC-N (R-8) and 8-Lead MSOP (RM-8)
OUT A 1
14 OUT D
–IN A 2
13 –IN D
+IN A 3 AD8674 12 +IN D
V+ 4 TOP VIEW 11 V–
+IN B 5 (Not to Scale) 10 +IN C
–IN B 6
9 –IN C
OUT B 7
8 OUT C
Figure 3. 14-Lead SOIC_N (R-14) and 14-Lead TSSOP (RU-14)
The AD8671, AD8672, and AD8674 are members of a growing
series of low noise op amps offered by Analog Devices, Inc.
Table 1. Voltage Noise
Package 0.9 nV 1.1 nV
Single AD797 AD8597
Dual
AD8599
Quad
1.8 nV
ADA4004-1
ADA4004-2
ADA4004-4
2.8 nV
AD8675
AD8676
3.8 nV
AD8671
AD8672
AD8674
Rev. F
Document Feedback
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©2004–2013 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 4.1
Parameter
Rating
Supply Voltage
Input Voltage
Differential Input Voltage
Output Short-Circuit Duration
36 V
VS– to VS+
±0.7 V
Indefinite
Storage Temperature Range
All Packages
Operating Temperature Range
8-Lead Packages
14-Lead Packages
Junction Temperature Range
All Packages
Lead Temperature Range (Soldering, 60 sec)
–65°C to +150°C
–40°C to +125°C
–40°C to +85°C
–65°C to +150°C
300°C
1 Absolute maximum ratings apply at 25°C, unless otherwise noted.
AD8671/AD8672/AD8674
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
See the Applications section for a related discussion on power.
Table 5. Package Characteristics
Package Type
θJA 1
8-Lead MSOP (RM) 142
8-Lead SOIC_N (R) 120
14-Lead SOIC_N (R) 90
14-Lead TSSOP (RU) 112
θJC
44
43
36
35
Unit
°C/W
°C/W
°C/W
°C/W
1 θJA is specified for the worst-case conditions, that is., θJA is specified for the
device soldered on a 4-layer circuit board for surface-mount packages.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. F | Page 5 of 20
5 Page 
Data Sheet
APPLICATIONS
POWER DISSIPATION CALCULATIONS
To achieve low voltage noise in a bipolar op amp, the current
must be increased. The emitter-base theoretical voltage noise is
approximately
en = 109 kT
2
qI C
nV/
Hz
To achieve the low voltage noise of 2.8 nV/√Hz, the input stage
current is higher than most op amps with an equivalent gain
bandwidth product. The thermal noise of a 1 kΩ resistor is
4 nV/√Hz, which is higher than the voltage noise of AD8671
family. Low voltage noise requires using low values of resistors,
so low voltage noise op amps should have good drive capability,
such as a 600 Ω load. This means that the second stage and
output stage are also biased at higher currents. As a result, the
supply current of a single op amp is 3.5 mA maximum at room
temperature.
Junction temperature has a direct affect on reliability. For more
information, visit the following Analog Devices, Inc., website:
http://www.analog.com/en/quality-and-reliability/reliability-
data/content/index.html
MTTF and FIT calculations can be done based on the junction
temperature and IC process. Use the following equation to
determine the junction temperature:
TJ = TA + PD × θJA
For the AD8671 single in the 8-lead MSOP package, the thermal
resistance, θJA, is 142°C/W. If the ambient temperature is 30°C
and the supply voltages are ±12 V, the power dissipation is
24 V × 3.5 mA = 84 mW
Therefore, the rise above ambient temperature is
84 mW × 142°C/W = 12°C
If the ambient temperature is 30°C, the junction temperature is
42°C. The previously mentioned website that details the effect
of the junction temperature on reliability has a calculator that
requires only the part number and the junction temperature to
determine the process technology.
For the AD8674 single in the 14-Lead TSSOP package, the thermal
resistance, θJA, is 112°C/W. Although θJA is lower than it is for the
8-lead package, the four op amps are powered simultaneously. If
the ambient temperature is 50°C and the supply voltages are ±15 V,
the power dissipation is
30 V × 4.2 mA × four op amps = 504 mW
AD8671/AD8672/AD8674
Therefore, the rise above ambient temperature is
504 mW × 112°C/W = 56°C
With an ambient temperature of 50°C, the junction temperature
is 106°C. This is less than the specified absolute maximum junction
temperature, but for systems with long product lifetimes (years),
this should be considered carefully.
Note that these calculations do not include the additional
dissipation caused by the load current on each op amp. Possible
solutions to reduce junction temperature include system level
considerations such as fans, Peltier thermoelectric coolers, and
heat pipes. Board considerations include operation on lower
voltages, such as ±12 V or ±5 V, and using two dual op amps
instead of one quad op amp. If the extremely low voltage noise
and high gain bandwidth is not required, using other quad op
amps, such as ADA4091-4, OP4177, ADA4004-4, OP497, or
AD704 can be considered.
UNITY-GAIN FOLLOWER APPLICATIONS
When large transient pulses (>1 V) are applied at the positive
terminal of amplifiers (such as the OP27, LT1007, OPA227, and
AD8671) with back-to-back diodes at the input stage, the use of
a resistor in the feedback loop is recommended to avoid having
the amplifier load the signal generator. The feedback resistor,
RF, should be at least 500 Ω. However, if large values must be
used for RF, a small capacitor, CF, should be inserted in parallel
with RF to compensate for the pole introduced by the input
capacitance and RF.
Figure 30 shows the uncompensated output response with a
10 kΩ resistor in the feedback and the compensated response
with CF = 15 pF.
OUTPUT UNCOMPENSATED
OUTPUT
COMPENSATED
REF1 +OVER
23.23%
CH2 +OVER
7.885%
TIME (100ns/DIV)
Figure 30. Transient Output Response
Rev. F | Page 11 of 20
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AD8674.PDF ] | |
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