Low Noise, High Speed Amplifier
for 16-Bit Systems
AD8021
FEATURES
Low Noise
2.1 nV/√Hz Input Voltage Noise
2.1 pA/√Hz Input Current Noise
Custom Compensation
Constant Bandwidth from G = –1 to G = –10
High Speed
200 MHz (G = –1)
190 MHz (G = –10)
Low Power
34 mW or 6.7 mA Typ for 5 V Supply
Output Disable Feature, 1.3 mA
Low Distortion
–93 dB Second Harmonic, f
C
= 1 MHz
–108 dB Third Harmonic, f
C
= 1 MHz
DC Precision
1 mV Max Input Offset Voltage
0.5 V/ C Input Offset Voltage Drift
Wide Supply Range, 5 V to 24 V
Low Price
Small Packaging
Available in SOIC-8 and MSOP-8
APPLICATIONS
ADC Preamp and Driver
Instrumentation Preamp
Active Filters
Portable Instrumentation
Line Receivers
Precision Instruments
Ultrasound Signal Processing
High Gain Circuits
CONNECTION DIAGRAM
SOIC-8 (R-8)
MSOP-8 (RM-8)
AD8021
1
2
3
4
8
7
6
5
LOGIC
REFERENCE
–IN
+IN
–V
S
DISABLE
+V
S
V
OUT
C
COMP
The AD8021 allows the user to choose the gain bandwidth
product that best suits the application. With a single capacitor,
the user can compensate the AD8021 for the desired gain with
little trade-off in bandwidth. The AD8021 is a very well behaved
amplifier that settles to 0.01% in 23 ns for a 1 V step. It has a fast
overload recovery of 50 ns.
The AD8021 is stable over temperature with low input offset
voltage drift and input bias current drift, 0.5
µV/°C
and 10 nA/°C,
respectively. The AD8021 is also capable of driving a 75
Ω
line
with
±
3 V video signals.
The AD8021 is not only technically superior, but also priced
considerably less than comparable amps drawing much higher
quiescent current. The AD8021 is a high speed, general-purpose
amplifier, ideal for a wide variety of gain configurations, and can
be used throughout a signal processing chain and in control loops.
The AD8021 is available in both standard 8-lead SOIC and MSOP
packages in the industrial temperature range of –40°C to +85°C.
24
V
OUT
= 50mV p-p
PRODUCT DESCRIPTION
21
18
G = –10, R
F
= 1k , R
G
= 100 ,
R
IN
= 100 , C
C
= 0pF
G = –5, R
F
= 1k , R
G
= 200 ,
R
IN
= 66.5 , C
C
= 1.5pF
The AD8021 is a very high performance, high speed voltage
feedback amplifier that can be used in 16-bit resolution systems.
It is designed to have low voltage and current noise (2.1 nV/√Hz
typ and 2.1 pA/√Hz typ) while operating at the lowest quiescent
supply current (7 mA @
±
5 V) among today’s high speed, low
noise op amps. The AD8021 operates over a wide range of
supply voltages from
±
2.5 V to
±
12 V, as well as from single
5 V supplies, making it ideal for high speed, low power instru-
ments. An output disable pin allows further reduction of the
quiescent supply current to 1.3 mA.
CLOSED-LOOP GAIN – dB
15
12
9
6
3
0
–3
–6
0.1M
1M
10M
FREQUENCY – Hz
100M
1G
G = –2, R
F
= 499 , R
G
= 249 ,
R
IN
= 63.4 , C
C
= 4pF
G = –1, R
F
= 499 , R
G
= 499 ,
R
IN
= 56.2 , C
C
= 7pF
Figure 1. Small Signal Frequency Response
REV. D
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. 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: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
AD8021–SPECIFICATIONS
V
S
= 5 V
Parameter
DYNAMIC PERFORMANCE
–3 dB Small Signal Bandwidth
(@ T
A
= 25 C, V
S
= 5 V, R
L
= 1 k , Gain = +2, unless otherwise noted.)
Conditions
G = +1, C
C
= 10 pF, V
O
= 0.05 V p-p
G = +2, C
C
= 7 pF, V
O
= 0.05 V p-p
G = +5, C
C
= 2 pF, V
O
= 0.05 V p-p
G = +10, C
C
= 0 pF, V
O
= 0.05 V p-p
G = +1, C
C
= 10 pF
G = +2, C
C
= 7 pF
G = +5, C
C
= 2 pF
G = +10, C
C
= 0 pF
V
O
= 1 V Step, R
L
= 500
Ω
AD8021AR/AD8021ARM
Min
Typ
Max
355
160
150
110
95
120
250
380
490
205
185
150
120
150
300
420
23
Unit
MHz
MHz
MHz
MHz
V/µs
V/µs
V/µs
V/µs
ns
Slew Rate, 1 V Step
Settling Time to 0.01%
Overload Recovery (50%)
DISTORTION/NOISE PERFORMANCE
f = 1 MHz
HD2
HD3
f = 5 MHz
HD2
HD3
Input Voltage Noise
Input Current Noise
Differential Gain Error
±
2.5 V Input Step, G = +2
50
ns
V
O
= 2 V p-p
V
O
= 2 V p-p
V
O
= 2 V p-p
V
O
= 2 V p-p
f = 50 kHz
f = 50 kHz
NTSC, R
L
= 150
Ω
–93
–108
–70
–80
2.1
2.1
0.03
dBc
dBc
dBc
dBc
nV/√Hz
pA/√Hz
%
2.6
Differential Phase Error
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Input Bias Current Drift
Input Offset Current
NTSC, R
L
= 150
Ω
0.04
0.4
0.5
7.5
10
0.1
1.0
10.5
0.5
Degrees
mV
µV/°C
µA
nA/°C
±µA
T
MIN
to T
MAX
+Input or –Input
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Common-Mode Input Capacitance
Input Common-Mode Voltage Range
82
86
10
1
–4.1 to +4.6
dB
MΩ
pF
V
Common-Mode Rejection Ratio
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current
Short-Circuit Current
V
CM
=
±
4 V
–86
–3.5 to +3.2
–98
–3.8 to +3.4
60
75
dB
V
mA
mA
Capacitive Load Drive for 30% Overshoot
DISABLE CHARACTERISTICS
Off Isolation
Turn-On Time
Turn-Off Time
V
O
= 50 mV p-p/1 V p-p
f = 10 MHz
V
O
= 0 V to 2 V, 50% Logic to 50% Output
V
O
= 0 V to 2 V, 50% Logic to 50% Output
15/120
–40
45
50
pF
dB
ns
ns
DISABLE
Voltage—Off/On
Enabled Leakage Current
Disabled Leakage Current
POWER SUPPLY
Operating Range
Quiescent Current
+Power Supply Rejection Ratio
–Power Supply Rejection Ratio
Specifications subject to change without notice.
V
DISABLE
– V
LOGIC REFERENCE
Logic Ref = 0.4 V
DISABLE
= 4.0 V
Logic Ref = 0.4 V
DISABLE
= 0.4 V
±
2.25
Output Enabled
Output Disabled
V
CC
= +4 V to +6 V, V
EE
= –5 V
V
CC
= +5 V, V
EE
= –6 V to –4 V
–86
–86
1.75/1.90
70
2
30
33
±
5
7.0
1.3
–95
±
12.0
7.7
1.6
V
µA
µA
µA
µA
V
mA
mA
dB
–95
dB
–2–
REV. D
AD8021
V
S
= 12 V
(@ T = 25 C, R = 1 k
A
L
, Gain = +2, unless otherwise noted.)
Conditions
G = +1, C
C
= 10 pF, V
O
= 0.05 V p-p
G = +2, C
C
= 7 pF, V
O
= 0.05 V p-p
G = +5, C
C
= 2 pF, V
O
= 0.05 V p-p
G = +10, C
C
= 0 pF, V
O
= 0.05 V p-p
G = +1, C
C
= 10 pF
G = +2, C
C
= 7 pF
G = +5, C
C
= 2 pF
G = +10, C
C
= 0 pF
V
O
= 1 V Step, R
L
= 500
Ω
±
6 V Input Step, G = +2
Parameter
DYNAMIC PERFORMANCE
–3 dB Small Signal Bandwidth
Min
520
175
170
125
105
140
265
400
AD8021AR/AD8021ARM
Typ
Max
560
220
200
165
130
170
340
460
21
90
Unit
MHz
MHz
MHz
MHz
V/µs
V/µs
V/µs
V/µs
ns
ns
Slew Rate, 1 V Step
Settling Time to 0.01%
Overload Recovery (50%)
DISTORTION/NOISE PERFORMANCE
f = 1 MHz
HD2
HD3
f = 5 MHz
HD2
HD3
Input Voltage Noise
Input Current Noise
Differential Gain Error
Differential Phase Error
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Input Bias Current Drift
Input Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Common-Mode Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
V
O
= 2 V p-p
V
O
= 2 V p-p
V
O
= 2 V p-p
V
O
= 2 V p-p
f = 50 kHz
f = 50 kHz
NTSC, R
L
= 150
Ω
NTSC, R
L
= 150
Ω
–95
–116
–71
–83
2.1
2.1
0.03
0.04
0.4
0.2
8
10
0.1
88
10
1
–11.1 to +11.6
–96
–10.6 to +10.2
70
115
15/120
–40
45
50
1.80/1.95
70
2
30
33
±
2.25
±
5
7.8
1.7
–96
–100
dBc
dBc
dBc
dBc
nV/√Hz
pA/√Hz
%
Degrees
mV
µV/°C
µA
nA/°C
±µA
dB
MΩ
pF
V
dB
V
mA
mA
pF
dB
ns
ns
V
µA
µA
µA
µA
±
12.0 V
8.6
mA
2.0
mA
dB
dB
2.6
1.0
11.3
0.5
T
MIN
to T
MAX
+Input or –Input
84
V
CM
=
±
10 V
–86
–10.2 to +9.8
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current
Short-Circuit Current
Capacitive Load Drive for 30% Overshoot V
O
= 50 mV p-p/1 V p-p
DISABLE CHARACTERISTICS
Off Isolation
Turn-On Time
Turn-Off Time
DISABLE
Voltage—Off/On
Enabled Leakage Current
Disabled Leakage Current
POWER SUPPLY
Operating Range
Quiescent Current
+Power Supply Rejection Ratio
–Power Supply Rejection Ratio
Specifications subject to change without notice.
f = 10 MHz
V
O
= 0 V to 2 V, 50% Logic to 50% Output
V
O
= 0 V to 2 V, 50% Logic to 50% Output
V
DISABLE
– V
LOGIC REFERENCE
Logic Ref = 0.4 V
DISABLE
= 4.0 V
Logic Ref = 0.4 V
DISABLE=
0.4 V
Output Enabled
Output Disabled
V
CC
= +11 V to +13 V, V
EE
= –12 V
V
CC
= +12 V, V
EE
= –13 V to –11 V
–86
–86
REV. D
–3–
AD8021
V
S
= 5 V
(@ T = 25 C, R = 1 k
A
L
, Gain = +2, unless otherwise noted.)
Conditions
G = +1, C
C
= 10 pF, V
O
= 0.05 V p-p
G = +2, C
C
= 7 pF, V
O
= 0.05 V p-p
G = +5, C
C
= 2 pF, V
O
= 0.05 V p-p
G = +10, C
C
= 0 pF, V
O
= 0.05 V p-p
G = +1, C
C
= 10 pF
G = +2, C
C
= 7 pF
G = +5, C
C
= 2 pF
G = +10, C
C
= 0 pF
V
O
= 1 V Step, R
L
= 500
Ω
0 V to 2.5 V Input Step, G = +2
Parameter
DYNAMIC PERFORMANCE
–3 dB Small Signal Bandwidth
AD8021AR/AD8021ARM
Min
Typ
Max
270
155
135
95
80
110
210
290
305
190
165
130
110
140
280
390
28
40
Unit
MHz
MHz
MHz
MHz
V/µs
V/µs
V/µs
V/µs
ns
ns
Slew Rate, 1 V Step
Settling Time to 0.01%
Overload Recovery (50%)
DISTORTION/NOISE PERFORMANCE
f = 1 MHz
HD2
HD3
f = 5 MHz
HD2
HD3
Input Voltage Noise
Input Current Noise
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Input Bias Current Drift
Input Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Common-Mode Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current
Short-Circuit Current
Capacitive Load Drive for 30% Overshoot
DISABLE CHARACTERISTICS
Off Isolation
Turn-On Time
Turn-Off Time
DISABLE
Voltage—Off/On
Enabled Leakage Current
Disabled Leakage Current
POWER SUPPLY
Operating Range
Quiescent Current
+Power Supply Rejection Ratio
–Power Supply Rejection Ratio
Specifications subject to change without notice.
V
O
= 2 V p-p
V
O
= 2 V p-p
V
O
= 2 V p-p
V
O
= 2 V p-p
f = 50 kHz
f = 50 kHz
–84
–91
–68
–81
2.1
2.1
0.4
0.8
7.5
10
0.1
76
10
1
0.9 to 4.6
–98
1.10 to 3.60
30
50
10/120
–40
45
50
1.55/1.70
70
2
30
33
±
2.25
±
5
6.7
1.2
–82
–84
dBc
dBc
dBc
dBc
nV/√Hz
pA/√Hz
mV
µV/°C
µA
nA/°C
±µA
dB
MΩ
pF
V
dB
V
mA
mA
pF
dB
ns
ns
V
µA
µA
µA
µA
±
12.0 V
7.5
mA
1.5
mA
dB
dB
2.6
1.0
10.3
0.5
T
MIN
to T
MAX
+Input or –Input
72
1.5 V to 3.5 V
–84
1.25 to 3.38
V
O
= 50 mV p-p/1 V p-p
f = 10 MHz
V
O
= 0 V to 1 V, 50% Logic to 50% Output
V
O
= 0 V to 1 V, 50% Logic to 50% Output
V
DISABLE
– V
LOGIC REFERENCE
Logic Ref = 0.4 V
DISABLE
= 4.0 V
Logic Ref = 0.4 V
DISABLE
= 0.4 V
Output Enabled
Output Disabled
V
CC
= 4.5 V to 5.5 V, V
EE
= 0 V
V
CC
= +5 V, V
EE
= –0.5 V to +0.5 V
–74
–76
–4–
REV. 0
AD8021
ABSOLUTE MAXIMUM RATINGS
1
MAXIMUM POWER DISSIPATION (mW)
2.0
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.4 V
Power Dissipation . . . . . . . . Observed Power Derating Curves
Input Voltage (Common-Mode) . . . . . . . . . . . . . . .
±
V
S
±
1 V
Differential Input Voltage
2
. . . . . . . . . . . . . . . . . . . . . .
±
0.8 V
Differential Input Current . . . . . . . . . . . . . . . . . . . . .
±
10 mA
Output Short-Circuit Duration
. . . . . . . . . . . . . . . . . . . . . . Observed Power Derating Curves
Storage Temperature . . . . . . . . . . . . . . . . . . –65∞C to +125∞C
Operating Temperature Range . . . . . . . . . . . –40∞C to +85∞C
Lead Temperature Range (Soldering, 10 sec) . . . . . . . . 300∞C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only and 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.
2
The AD8021 inputs are protected by diodes. Current-limiting resistors are not
used in order to preserve the low noise. If a differential input exceeds
±
0.8 V, the
input current should be limited to
±
10 mA.
1.5
8-LEAD SOIC
1.0
8-LEAD MSOP
0.5
0.01
–55 –45 –35 –25 –15 –5 5 15 25 35 45 55 65 75
85
AMBIENT TEMPERATURE ( C)
Figure 2. Maximum Power Dissipation vs. Temperature*
*
Specification is for device in free air:
8-Lead SOIC:
JA
= 125∞C/W
8-Lead MSOP:
JA
= 145∞C/W
MAXIMUM POWER DISSIPATION
The maximum power that can be safely dissipated by the AD8021
is limited by the associated rise in junction temperature. The maxi-
mum safe junction temperature for plastic encapsulated devices
is determined by the glass transition temperature of the plastic,
approximately 150∞C. Temporarily exceeding this limit may cause
a shift in parametric performance due to a change in the stresses
exerted on the die by the package. Exceeding a junction tempera-
ture of 175∞C for an extended period can result in device failure.
While the AD8021 is internally short-circuit protected, this may
not be sufficient to guarantee that the maximum junction tem-
perature (150∞C) is not exceeded under all conditions. To ensure
proper operation, it is necessary to observe the maximum power
derating curves.
PIN CONFIGURATION
LOGIC
REFERENCE
–IN
+IN
–V
S
1
2
3
4
PIN FUNCTION DESCRIPTIONS
Pin No. Mnemonic
1
2
3
4
5
6
7
8
Function
LOGIC REFERENCE Reference for Pin 8* Voltage
Level. Connect to logic low
supply.
–IN
Inverting Input
+IN
Noninverting Input
Negative Supply Voltage
–V
S
Compensation Capacitor. Tie
C
COMP
to –V
S
. (See the Applications
section for value.)
Output
V
OUT
Positive Supply Voltage
+V
S
DISABLE
Disable, Active Low*
AD8021
8
7
6
5
DISABLE
+V
S
V
OUT
C
COMP
*When
Pin 8 (DISABLE) is about 2 V or more higher than Pin 1 (LOGIC
REFERENCE), the part is enabled. When Pin 8 is brought down to within about
1.5 V of Pin 1, the part is disabled. (See the Specification tables for exact disable and
enable voltage levels.) If the disable feature is not going to be used, Pin 8 can be tied
to +V
S
or a logic high source, and Pin 1 can be tied to ground or logic low. Alterna-
tively, if Pin 1 and Pin 8 are not connected, the part will be in an enabled state.
ORDERING GUIDE
Model
AD8021AR
AD8021AR-REEL
AD8021AR-REEL7
AD8021ARM
AD8021ARM-REEL
AD8021ARM-REEL7
AD8021ARZ*
AD8021ARZ-REEL*
AD8021ARZ-REEL7*
*Z
= Lead Free
Temperature Range
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
–40∞C to +85∞C
Package Description
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
8-Lead MSOP
8-Lead MSOP
8-Lead MSOP
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
Package Outline
R-8
R-8
R-8
RM-8
RM-8
RM-8
R-8
R-8
R-8
Branding
HNA
HNA
HNA
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 the
AD8021 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. D
–5–
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