ANALOG DEVICES AD8274 Service Manual
Very Low Distortion,
V
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FEATURES
Very low distortion
0.00025% THD + N (20 kHz)
0.0015% THD + N (100 kHz)
Drives 600 Ω loads
Excellent gain accuracy
0.03% maximum gain error
2 ppm/°C maximum gain drift
Gain of ½ or 2
AC specifications
20 V/μs minimum slew rate
800 ns to 0.01% settling time
High accuracy dc performance
83 dB minimum CMRR
700 μV maximum offset voltage
8-lead SOIC and MSOP packages
Supply current: 2.6 mA maximum
Supply range: ±2.5 V to ±18 V
APPLICATIONS
ADC driver
High performance audio
Instrumentation amplifier building blocks
Level translators
Automatic test equipment
Sine/cosine encoders
Precision Difference Amplifier
AD8274
FUNCTIONAL BLOCK DIAGRAM
+
S
7
12kΩ 6kΩ
2
12kΩ
3 1
4
–V
S
Figure 1.
Table 1. Difference Amplifiers by Category
Low
Distortion
AD8270 AD628 AD8202 AD8205
AD8273 AD629 AD8203 AD8206
AD8274 AD8216
AMP03
High
Voltage
Single-Supply
Unidirectional
6kΩ
5
6
07362-001
Single-Supply
Bidirectional
GENERAL DESCRIPTION
The AD8274 is a difference amplifier that delivers excellent ac
and dc performance. Built on Analog Devices, Inc., proprietary
iPolar® process and laser-trimmed resistors, AD8274 achieves a
breakthrough in distortion vs. current consumption and has
excellent gain drift, gain accuracy, and CMRR.
Distortion in the audio band is an extremely low 0.00025%
(112 dB) at a gain of ½ and 0.00035% (109 dB) at a gain of 2
while driving a 600 load
With supply voltages up to ±18 V (+36 V single supply), the
AD8274 is well suited for measuring large industrial signals.
Additionally, the part’s resistor divider architecture allows it to
measure voltages beyond the supplies.
Rev. 0
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.
Trademarks and registered trademarks are the property of their respective owners.
With no external components, the AD8274 can be configured
as a G = ½ or G = 2 difference amplifier. For single-ended
applications that need high gain stability or low distortion
performance, the AD8274 can also be configured for several
gains ranging from −2 to +3.
The excellent distortion and dc performance of the AD8274,
along with its high slew rate and bandwidth, make it an excellent
ADC driver. Because of the part’s high output drive, it also
makes a very good cable driver.
The AD8274 only requires 2.6 mA maximum supply current. It
is specified over the industrial temperature range of −40°C to
+85°C and is fully RoHS compliant. For the dual version, see the
AD8273 data sheet.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved.
AD8274
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TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Absolute Maximum Ratings ............................................................ 4
Thermal Resistance ...................................................................... 4
Maximum Power Dissipation ..................................................... 4
Short-Circuit Current .................................................................. 4
ESD Caution .................................................................................. 4
REVISION HISTORY
7/08—Revision 0: Initial Version
Pin Configurations and Function Description ..............................5
Typical Performance Characteristics ..............................................6
Theory of Operation ...................................................................... 12
Circuit Information .................................................................... 12
Driving the AD8274 ................................................................... 12
Power Supplies ............................................................................ 12
Input Voltage Range ................................................................... 12
Configurations ............................................................................ 13
Driving Cabling .......................................................................... 14
Outline Dimensions ....................................................................... 15
Ordering Guide .......................................................................... 15
Rev. 0 | Page 2 of 16
AD8274
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SPECIFICATIONS
VS = ±15 V, V
Table 2.
G = ½ G = 2
Parameter Conditions Min Typ Max Min Typ Max Unit
DYNAMIC PERFORMANCE
Bandwidth 20 10 MHz
Slew Rate 20 20 V/μs
Settling Time to 0.1% 10 V step on output, CL = 100 pF 650 750 675 775 ns
Settling Time to 0.01% 10 V step on output, CL = 100 pF 725 800 750 825 ns
NOISE/DISTORTION
THD + Noise
Noise Floor, RTO
Output Voltage Noise
(Referred to Output)
f = 1 kHz 26 52 nV/√Hz
GAIN
Gain Error 0.03 0.03 %
Gain Drift −40°C to +85°C 0.5 2 0.5 2 ppm/°C
Gain Nonlinearity V
INPUT CHARACTERISTICS
3
Offset
vs. Temperature −40°C to +85°C 3 6 μV/°C
vs. Power Supply VS = ±2.5 V to ±18 V 5 10 μV/V
Common-Mode Rejection Ratio
Input Voltage Range
Impedance
Differential VCM = 0 V 24 12 kΩ
Common Mode
OUTPUT CHARACTERISTICS
Output Swing
Short-Circuit Current Limit Sourcing 90 90 mA
Sinking 60 60 mA
Capacitive Load Drive 200 1200 pF
POWER SUPPLY
Supply Current (per Amplifier) 2.3 2.6 2.3 2.6 mA
TEMPERATURE RANGE
Specified Performance −40 +85 −40 +85 °C
1
Includes amplifier voltage and current noise, as well as noise of internal resistors.
2
dBu = 20 log(V rms/0.7746).
3
Includes input bias and offset current errors.
4
May also be limited by absolute maximum input voltage or by the output swing. See the Absolute Maximum Ratings section and Figure 8 through Figure 11 for details.
5
Internal resistors are trimmed to be ratio matched but to have ±20% absolute accuracy.
6
Common mode is calculated by looking into both inputs. The common-mode impedance at only one input is 18 kΩ.
= 0 V, TA = 25°C, RL = 2 kΩ, unless otherwise noted.
REF
1
f = 1 kHz, V
= 10 V p-p,
OUT
0.00025 0.00035 %
600 Ω load
2
20 kHz BW −106 −100 dBu
f = 20 Hz to 20 kHz 3.5 7 μV rms
= 10 V p-p, 600 Ω load 2 2 ppm
OUT
Referred to output 150 700 300 1100 μV
= ±40 V, RS = 0 Ω, referred
V
CM
77 86 83 92 dB
to input
4
−3V
+ 4.5
5
6
9 9 kΩ
−V
1.5
S
+
S
+3VS
− 4.5
+V
S
1.5
−
−1.5VS
+ 2.3
−VS +
1.5
+1.5VS
V
− 2.3
+V
S
−
V
1.5
Rev. 0 | Page 3 of 16
AD8274
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ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
Supply Voltage ±18 V
Maximum Voltage at Any Input Pin −VS + 40 V
Minimum Voltage at Any Input Pin +VS – 40 V
Storage Temperature Range −65°C to +150°C
Specified Temperature Range −40°C to +85°C
Package Glass Transition Temperature (TG) 150°C
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.
THERMAL RESISTANCE
The θJA values in Tabl e 4 assume a 4-layer JEDEC standard
board with zero airflow.
MAXIMUM POWER DISSIPATION
The maximum safe power dissipation for the AD8274 is limited
by the associated rise in junction temperature (T
approximately 150°C, which is the glass transition temperature,
the properties of the plastic change. Even temporarily exceeding
this temperature limit may change the stresses that the package
exerts on the die, permanently shifting the parametric performance
of the amplifiers. Exceeding a temperature of 150°C for an
extended period may result in a loss of functionality.
2.0
TJ MAX = 150°C
1.6
1.2
MSOP
θ
= 135°C/W
0.8
0.4
MAXIMUM POWER DISSIPATIO N (W)
JA
SOIC
= 121°C/W
θ
JA
) on the die. At
J
Table 4. Thermal Resistance
Package Type θJA Unit
8-Lead MSOP 135 °C/W
8-Lead SOIC 121 °C/W
0
–50 0–25 25 50 75 100 125
Figure 2. Maximum Power Dissipation vs. Ambient Temperature
AMBIENT TEM ERATURE (°C)
07362-004
SHORT-CIRCUIT CURRENT
The AD8274 has built-in, short-circuit protection that limits the
output current (see Figure 16 for more information). While the
short-circuit condition itself does not damage the part, the heat
generated by the condition can cause the part to exceed its
maximum junction temperature, with corresponding negative
effects on reliability. Figure 2 and Figure 16, combined with
knowledge of the part’s supply voltages and ambient temperature,
can be used to determine whether a short circuit will cause the
part to exceed its maximum junction temperature.
ESD CAUTION
Rev. 0 | Page 4 of 16
AD8274
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PIN CONFIGURATIONS AND FUNCTION DESCRIPTION
REF
1
AD8274
2
–IN
TOP VIEW
+IN
3
(Not to Scal e)
–V
4
S
NC = NO CONNECT
Figure 3. MSOP Pin Configuration
Table 5. Pin Function Descriptions
Pin No. Mnemonic Description
1 REF
2 −IN
3 +IN
4 −VS Negative Supply.
5 SENSE
6 OUT Output.
7 +VS Positive Supply.
8 NC No Connect.
NC
8
7
6
5
+V
S
OUT
SENSE
07362-002
REF
1
–IN
2
+IN
3
(Not to Scale)
4
–V
S
NC = NO CONNECT
AD8274
TOP VIEW
8
7
6
5
NC
+V
S
OUT
SENSE
07362-003
Figure 4. SOIC Pin Configuration
6 kΩ Resistor to Noninverting Terminal of Op Amp. Used as reference pin in G = ½ configuration. Used as
positive input in G = 2 configuration.
12 kΩ Resistor to Inverting Terminal of Op Amp. Used as negative input in G = ½ configuration. Connect
to output in G = 2 configuration.
12 kΩ Resistor to Noninverting Terminal of Op Amp. Used as positive input in G = ½ configuration. Used
as reference pin in G = 2 configuration.
6 kΩ Resistor to Inverting Terminal of Op Amp. Connect to output in G = ½ configuration. Used as
negative input in G = 2 configuration.
Rev. 0 | Page 5 of 16
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