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Ultralow Distortion,
Ultralow Noise Op Amp
AD797
FEATURES
Low noise
0.9 nV/√Hz typical (1.2 nV/√Hz maximum) input voltage
noise at 1 kHz
50 nV p-p input voltage noise, 0.1 Hz to 10 Hz
Low distortion
−120 dB total harmonic distortion at 20 kHz
Excellent ac characteristics
800 ns settling time to 16 bits (10 V step)
110 MHz gain bandwidth (G = 1000)
8 MHz bandwidth (G = 10)
280 kHz full power bandwidth at 20 V p-p
20 V/μs slew rate
Excellent dc precision
80 μV maximum input offset voltage
1.0 μV/°C V
OS
drift
Specified for ±5 V and ±15 V power supplies
High output drive current of 50 mA
GENERAL DESCRIPTION
The AD797 is a very low noise, low distortion operational amplifier
ideal for use as a preamplifier. The low noise of 0.9 nV/√Hz and
low total harmonic distortion of −120 dB in audio bandwidths
give the AD797 the wide dynamic range necessary for preamps
in microphones and mixing consoles.
Furthermore, the AD797 has an excellent slew rate of 20 V/μs
and a 110 MHz gain bandwidth, which makes it highly suitable
for low frequency ultrasound applications.
The AD797 is also useful in infrared (IR) and sonar imaging
applications, where the widest dynamic range is necessary. The
low distortion and 16-bit settling time of the AD797 make it
ideal for buffering the inputs to Σ-Δ ADCs or the outputs of
high resolution DACs, especially when the device is used in
critical applications such as seismic detection or in spectrum
analyzers. Key features such as a 50 mA output current drive
and the specified power supply voltage range of ±5 V to ±15 V
make the AD797 an excellent general-purpose amplifier.
5
APPLICATIONS
Professional audio preamplifiers
IR, CCD, and sonar imaging systems
Spectrum analyzers
Ultrasound preamplifiers
Seismic detectors
Σ-Δ ADC/DAC buffers
INPUT VOLTAGE NOISE (nV/√Hz)
4
3
2
1
10
100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
Figure 1. AD797 Voltage Noise Spectral Density
Table 1. Low Noise Op Amps
Voltage Noise
Single
Dual
Quad
0.9 nV
AD797
1.1 nV
AD8597
AD8599
1.8 nV
ADA4004-1
ADA4004-2
ADA4004-4
2.8 nV
AD8675/ADA4075-2
AD8676
3.2 nV
OP27
OP270
OP470
3.8 nV
AD8671
AD8672
AD8674
Rev. H
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.
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 ©2002-2010 Analog Devices, Inc. All rights reserved.
00846-002
0
AD797
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
Pin Configuration ............................................................................. 5
Thermal Resistance ...................................................................... 5
ESD Caution .................................................................................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 11
Noise and Source Impedance Considerations ........................... 12
Low Frequency Noise ................................................................ 12
Wideband Noise ......................................................................... 12
Bypassing Considerations ......................................................... 13
The Noninverting Configuration ............................................. 13
The Inverting Configuration .................................................... 14
Driving Capacitive Loads .......................................................... 14
Settling Time ............................................................................... 14
Distortion Reduction ................................................................. 15
Outline Dimensions ....................................................................... 18
Ordering Guide .......................................................................... 19
REVISION HISTORY
6/10—Rev. G to Rev. H
Added Table 1; Renumbered Sequentially .................................... 1
Moved Figure 1 to Absolute Maximum Ratings Section;
Renumbered Sequentially................................................................ 5
Changes to Table 3 ............................................................................ 5
Added Thermal Resistance Section and Table 4 .......................... 5
Moved Figure 3 to Typical Performance Characteristics
Section .............................................................................................. 10
Change to Noise and Source Impedance Considerations
Section .............................................................................................. 12
Changes to Ordering Guide .......................................................... 19
9/08—Rev. F to Rev. G
Changes to Input Common-Mode Voltage Range Parameter,
Table 1 ................................................................................................ 3
1/08—Rev. E to Rev. F
Changes to Absolute Maximum Ratings ....................................... 5
Change to Equation 1 ..................................................................... 12
Changes to the Noninverting Configuration Section ................ 13
Updated Outline Dimensions ....................................................... 19
Changes to Ordering Guide .......................................................... 20
7/05—Rev. D to Rev. E
Updated Figure 1 Caption ................................................................1
Deleted Metallization Photo ............................................................6
Changes to Equation 1 ................................................................... 12
Updated Outline Dimensions ....................................................... 19
Changes to Ordering Guide .......................................................... 20
10/02—Rev. C to Rev. D
Deleted 8-Lead CERDIP Package (Q-8) ......................... Universal
Edits to Specifications .......................................................................2
Edits to Absolute Maximum Ratings ..............................................3
Edits to Ordering Guide ...................................................................3
Edits to Table I ...................................................................................9
Deleted Operational Amplifiers Graphic .................................... 15
Updated Outline Dimensions ....................................................... 15
Rev. H | Page 2 of 20
AD797
SPECIFICATIONS
T
A
= 25°C and V
S
= ±15 V dc, unless otherwise noted.
Table 2.
AD797A
Parameter
INPUT OFFSET VOLTAGE
Offset Voltage Drift
INPUT BIAS CURRENT
T
MIN
to T
MAX
INPUT OFFSET CURRENT
OPEN-LOOP GAIN
T
MIN
to T
MAX
V
OUT
= ±10 V
R
LOAD
= 2 kΩ
T
MIN
to T
MAX
R
LOAD
= 600 Ω
T
MIN
to T
MAX
@ 20 kHz
1
G = 1000
G = 1000
2
G = 10
V
OUT
= 20 V p-p,
R
LOAD
= 1 kΩ
R
LOAD
= 1 kΩ
10 V step
V
CM
= CMVR
T
MIN
to T
MAX
V
S
= ±5 V to ±18 V
T
MIN
to T
MAX
f = 0.1 Hz to 10 Hz
f = 10 Hz
f = 1 kHz
f = 10 Hz to 1 MHz
f = 1 kHz
±5 V, ±15 V
±15 V
1
1
1
1
14,000
Conditions
T
MIN
to T
MAX
±5 V, ±15 V
±5 V, ±15 V
Supply
Voltage (V)
±5 V, ±15 V
Min
Typ
25
50
0.2
0.25
0.5
100
120
20
6
15
5
20,000
Max
80
125/180
1.0
1.5
3.0
400
600/700
Min
AD797B
Typ
10
30
0.2
0.25
0.25
80
120
20
10
15
7
20,000
Max
40
60
0.6
0.9
2.0
200
300
Unit
μV
μV
μV/°C
μA
μA
nA
nA
V/μV
V/μV
V/μV
V/μV
V/V
2
2
2
2
14,000
DYNAMIC PERFORMANCE
Gain Bandwidth Product
–3 dB Bandwidth
Full Power Bandwidth
1
Slew Rate
Settling Time to 0.0015%
COMMON-MODE REJECTION
POWER SUPPLY REJECTION
INPUT VOLTAGE NOISE
±15 V
15 V
±15 V
±15 V
±15 V
±15 V
±5 V, ±15 V
12.5
114
110
114
110
110
450
8
280
20
800
130
120
130
120
50
1.7
0.9
1.0
2.0
±12
±3
±13
±13
±3
80
50
110
450
8
280
12.5
1200
120
114
120
130
20
800
130
120
114
120
50
1.7
0.9
1.0
2.0
±12
±3
±13
±13
±3
80
50
MHz
MHz
MHz
kHz
V/μs
ns
dB
dB
dB
dB
nV p-p
nV/√Hz
nV/√Hz
μV rms
pA/√Hz
V
V
V
V
V
mA
mA
1200
INPUT CURRENT NOISE
INPUT COMMON-MODE
VOLTAGE RANGE
OUTPUT VOLTAGE SWING
±15 V
±15 V
±15 V
±15 V
±15 V
±15 V
±5 V
±15 V
±15 V
±5 V
±5 V, ±15 V
±5 V, ±15 V
1.2
1.3
±11
±2.5
±12
±11
±2.5
30
2.5
1.2
1.2
±11
±2.5
±12
±11
±2.5
30
R
LOAD
= 2 kΩ
R
LOAD
= 600 Ω
R
LOAD
= 600 Ω
Short-Circuit Current
Output Current
3
Rev. H | Page 3 of 20
AD797
AD797A
Parameter
TOTAL HARMONIC
DISTORTION
Conditions
R
LOAD
= 1 kΩ, C
N
= 50 pF,
f = 250 kHz, 3 V rms
R
LOAD
= 1 kΩ,
f = 20 kHz, 3 V rms
Supply
Voltage (V)
±15 V
±15 V
Min
Typ
−98
−120
Max
−90
−110
Min
AD797B
Typ
−98
−120
Max
−90
−110
Unit
dB
dB
INPUT CHARACTERISTICS
Input Resistance
Differential
Common Mode
Input Capacitance
Differential
4
Common Mode
OUTPUT RESISTANCE
POWER SUPPLY
Operating Range
Quiescent Current
1
2
7.5
100
20
5
3
±5
±5 V, ±15 V
8.2
±18
10.5
±5
7.5
100
20
5
3
±18
10.5
kΩ
MΩ
pF
pF
mΩ
V
mA
A
V
= 1, f = 1 kHz
8.2
Full power bandwidth = slew rate/2π V
PEAK
.
Specified using external decompensation capacitor.
3
Output current for |V
S
− V
OUT
| > 4 V, A
OL
> 200 kΩ.
4
Differential input capacitance consists of 1.5 pF package capacitance and 18.5 pF from the input differential pair.
Rev. H | Page 4 of 20
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