250 MHz, General Purpose
Voltage Feedback Op Amps
AD8047/AD8048
FEATURES
Wide Bandwidth
AD8047, G = +1
Small Signal
250 MHz
Large Signal (2 V p-p) 130 MHz
AD8048, G = +2
260 MHz
160 MHz
5.8 mA Typical Supply Current
Low Distortion, (SFDR) Low Noise
–66 dBc Typ @ 5 MHz
–54 dBc Typ @ 20 MHz
5.2 nV/√Hz (AD8047), 3.8 nV/√Hz (AD8048) Noise
Drives 50 pF Capacitive Load
High Speed
Slew Rate 750 V/s (AD8047), 1000 V/s (AD8048)
Settling 30 ns to 0.01%, 2 V Step
3 V to 6 V Supply Operation
APPLICATIONS
Low Power ADC Input Driver
Differential Amplifiers
IF/RF Amplifiers
Pulse Amplifiers
Professional Video
DAC Current to Voltage Conversion
Baseband and Video Communications
Pin Diode Receivers
Active Filters/Integrators
FUNCTIONAL BLOCK DIAGRAM
8-Pin Plastic PDIP (N)
and SOIC (R) Packages
AD8047/
AD8048
8
NC
2
7
+VS
+INPUT
3
6
OUTPUT
–V S
4
5
NC
NC
1
–INPUT
(TOP VIEW)
NC = NO CONNECT
The AD8047 and AD8048’s low distortion and cap load drive
make the AD8047/AD8048 ideal for buffering high speed ADCs.
They are suitable for 12-bit/10 MSPS or 8-bit/60 MSPS ADCs.
Additionally, the balanced high impedance inputs of the voltage
feedback architecture allow maximum flexibility when designing
active filters.
The AD8047 and AD8048 are offered in industrial (–40°C to
+85°C) temperature ranges and are available in 8-lead PDIP
and SOIC packages.
PRODUCT DESCRIPTION
The AD8047 and AD8048 are very high speed and wide bandwidth amplifiers. The AD8047 is unity gain stable. The AD8048 is
stable at gains of two or greater. The AD8047 and AD8048,
which utilize a voltage feedback architecture, meet the requirements of many applications that previously depended on current
feedback amplifiers.
A proprietary circuit has produced an amplifier that combines
many of the best characteristics of both current feedback and
voltage feedback amplifiers. For the power (6.6 mA max), the
AD8047 and AD8048 exhibit fast and accurate pulse response
(30 ns to 0.01%) as well as extremely wide small signal and large
signal bandwidth and low distortion. The AD8047 achieves
–54 dBc distortion at 20 MHz, 250 MHz small signal, and
130 MHz large signal bandwidths.
1V
5ns
Figure 1. AD8047 Large Signal Transient Response,
VO = 4 V p-p, G = +1
REV. A
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 companies.
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.
AD8047/AD8048–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter
DYNAMIC PERFORMANCE
Bandwidth (–3 dB)
Small Signal
Large Signal1
Bandwidth for 0.1 dB Flatness
Slew Rate, Average +/–
Rise/Fall Time
Settling Time
To 0.1%
To 0.01%
HARMONIC/NOISE PERFORMANCE
Second Harmonic Distortion
Third Harmonic Distortion
Input Voltage Noise
Input Current Noise
Average Equivalent Integrated
Input Noise Voltage
Differential Gain Error (3.58 MHz)
Differential Phase Error (3.58 MHz)
(VS = 5 V, RLOAD = 100 , AV = 1 (AD8047), AV = 2 (AD8048), unless otherwise noted.)
Conditions
Min
VOUT ≤ 0.4 V p-p
VOUT = 2 V p-p
VOUT = 300 mV p-p
AD8047, RF = 0 Ω;
AD8048, RF = 200 Ω
VOUT = 4 V Step
VOUT = 0.5 V Step
VOUT = 4 V Step
170
100
AD8047A
Typ Max
475
250
130
35
750
1.1
4.3
Unit
180
135
260
160
MHz
MHz
50
1000
1.2
3.2
MHz
V/µs
ns
ns
740
VOUT = 2 V Step
VOUT = 2 V Step
13
30
13
30
ns
ns
2 V p-p; 20 MHz
RL = 1 kΩ
2 V p-p; 20 MHz
RL = 1 kΩ
f = 100 kHz
f = 100 kHz
–54
–64
–60
–61
5.2
1.0
–48
–60
–56
–65
3.8
1.0
dBc
dBc
dBc
dBc
nV/√Hz
pA/√Hz
0.1 MHz to 10 MHz
RL = 150 Ω, G = +2
RL = 150 Ω, G = +2
16
0.02
0.03
11
0.01
0.02
µV rms
%
Degree
DC PERFORMANCE2, RL = 150 Ω
Input Offset Voltage3
1
TMIN to TMAX
±5
1
Offset Voltage Drift
Input Bias Current
TMIN to TMAX
Input Offset Current
Common-Mode Rejection Ratio
Open-Loop Gain
AD8048A
Min Typ Max
0.5
TMIN to TMAX
VCM = ± 2.5 V
VOUT = ± 2.5 V
TMIN to TMAX
74
58
54
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Common-Mode Voltage Range
OUTPUT CHARACTERISTICS
Output Voltage Range, RL = 150 Ω
Output Current
Output Resistance
Short-Circuit Current
POWER SUPPLY
Operating Range
Quiescent Current
1
±5
1
3.5
6.5
2
3
80
62
0.5
74
65
56
3
4
3.5
6.5
2
3
80
68
mV
mV
µV/°C
µA
µA
µA
µA
dB
dB
dB
500
1.5
± 3.4
500
1.5
± 3.4
kΩ
pF
V
± 2.8
± 3.0
50
0.2
130
± 2.8 ± 3.0
50
0.2
130
V
mA
Ω
mA
± 3.0
± 5.0 ± 6.0
5.8 6.6
7.5
78
± 3.0 ± 5.0 ± 6.0
5.9 6.6
7.5
72
78
V
mA
mA
dB
TMIN to TMAX
Power Supply Rejection Ratio
3
4
72
NOTES
1
See Absolute Maximum Ratings and Theory of Operation sections.
2
Measured at AV = 50.
3
Measured with respect to the inverting input.
Specifications subject to change without notice.
–2–
REV. A
AD8047/AD8048
ABSOLUTE MAXIMUM RATINGS 1
MAXIMUM POWER DISSIPATION
Supply Voltage, (+VS) – (–VS) . . . . . . . . . . . . . . . . . . . . 12.6 V
Voltage Swing × Bandwidth Product
AD8047 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 V-MHz
AD8048 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 V-MHz
Internal Power Dissipation2
Plastic Package (N) . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 W
Small Outline Package (R) . . . . . . . . . . . . . . . . . . . . . 0.9 W
Input Voltage (Common Mode) . . . . . . . . . . . . . . . . . . . . ± VS
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . ± 1.2 V
Output Short-Circuit Duration . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . Observe Power Derating Curves
Storage Temperature Range (N, R) . . . . . . . –65°C to +125°C
Operating Temperature Range (A Grade) . . . –40°C to +85°C
Lead Temperature Range (Soldering 10 sec) . . . . . . . . . 300°C
The maximum power that can be safely dissipated by these devices
is limited by the associated rise in junction temperature. The
maximum safe junction temperature for plastic encapsulated
devices is determined by the glass transition temperature of the
plastic, approximately 150°C. Exceeding this limit temporarily
may cause a shift in parametric performance due to a change in
the stresses exerted on the die by the package. Exceeding a
junction temperature of 175°C for an extended period can
result in device failure.
While the AD8047 and AD8048 are internally short circuit
protected, this may not be sufficient to guarantee that the maximum junction temperature (150°C) is not exceeded under all
conditions. To ensure proper operation, it is necessary to observe
the maximum power derating curves.
NOTES
1
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.
2
Specification is for device in free air: 8-Lead PDIP Package, ␪JA = 90°C/W; 8-Lead
SOIC Package, ␪JA = 140°C/W
2.0
MAXIMUM POWER DISSIPATION (W)
8-PIN PDIP PACKAGE
METALLIZATION PHOTOS
Dimensions shown in inches and (mm)
Connect Substrate to –V S.
AD8047
+VS
TJ = +150C
1.5
1.0
8-PIN SOIC PACKAGE
0.5
0
–50 –40 –30 –20 –10
0 10 20 30 40 50 60
AMBIENT TEMPERATURE (C)
0.045
(1.14)
70
80
90
Figure 2. Plot of Maximum Power Dissipation vs.
Temperature
VOUT
–IN
ORDERING GUIDE
–VS
+IN
0.044
(1.13)
AD8048
+VS
0.045
(1.14)
VOUT
Model
Temperature
Range
Package
Description
Package
Option*
AD8047AN
AD8047AR
AD8047AR-REEL
AD8047AR-REEL7
AD8048AN
AD8048AR
AD8048AR-REEL
AD8048AR-REEL7
–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
PDIP
SOIC
SOIC
SOIC
PDIP
SOIC
SOIC
SOIC
N-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
*N = PDIP, R= SOIC
–IN
–VS
+IN
0.044
(1.13)
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
AD8047/AD8048 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. A
–3–
AD8047/AD8048–Typical Performance Characteristics
RF
PULSE
GENERATOR
10F
+VS
TR/TF = 500ps
0.1F
PULSE
GENERATOR
2
TR/TF = 500ps
3
VOUT
6
0.1F
4
RT = 49.9
2
VIN
AD8047
VIN
0.1F
RIN
7
3
RL = 100
4
RL = 100
10F
–VS
TPC 1. AD8047 Noninverting Configuration, G = +1
TPC 4. AD8047 Inverting Configuration, G = –1
5ns
1V
TPC 2. AD8047 Large Signal Transient Response;
VO = 4 V p-p, G = +1
100mV
VOUT
6
0.1F
100
–VS
1V
7
AD8047
RT = 66.5
10F
10F
+VS
5ns
TPC 5. AD8047 Large Signal Transient Response;
VO = 4 V p-p, G = –1, RF = RIN = 200 Ω
100mV
5ns
TPC 3. AD8047 Small Signal Transient Response;
VO = 400 mV p-p, G = +1
5ns
TPC 6. AD8047 Small Signal Transient Response;
VO = 400 mV p-p, G = –1, RF = RIN = 200 Ω
–4–
REV. A
AD8047/AD8048
RF
PULSE
GENERATOR
10F
+VS
TR/TF = 500ps
PULSE
GENERATOR
2
2
VIN
VOUT
6
3
4
RL = 100
RL = 100
–VS
TPC 7. AD8048 Noninverting Configuration, G = +2
TPC 10. AD8048 Inverting Configuration, G= –1
1V
5ns
TPC 8. AD8048 Large Signal Transient Response;
VO = 4 V p-p, G = +2, RF = RIN = 200 Ω
5ns
TPC 11. AD8048 Large Signal Transient Response;
VO = 4 V p-p, G = –1, RF = RIN = 200 Ω
100mV
5ns
TPC 9. AD8048 Small Signal Transient Response;
VO = 400 mV p-p, G = +2, RF = RIN = 200 Ω
REV. A
4
10F
–VS
100mV
VOUT
6
0.1F
RS = 100
10F
1V
7
AD8048
RT = 66.5
0.1F
RT = 49.9
10F
0.1F
RIN
7
AD8048
3
+VS
TR/TF = 500ps
0.1F
RIN
VIN
RF
5ns
TPC 12. AD8048 Small Signal Transient Response;
VO = 400 mV p-p, G = –1, RF = RIN = 200 Ω
–5–
AD8047/AD8048
1
1
0
0
–1
–1
RL = 100
RF = 0 FOR DIP
RF = 66.5 FOR SOIC
VOUT = 300mV p-p
–3
–2
OUTPUT (dBm)
OUTPUT (dBm)
–2
–4
–5
–3
–4
–5
–6
–6
–7
–7
–8
–8
–9
1M
10M
100M
RL = 100
RF = 0 FOR DIP
RF = 66.5 FOR SOIC
VOUT = 2V p-p
–9
1M
1G
10M
FREQUENCY (Hz)
TPC 13. AD8047 Small Signal Frequency Response,
G = +1
1
0
0
RL = 100
RF = 0 FOR DIP
RF = 66.5 FOR SOIC
VOUT = 300mV p-p
–1
–2
OUTPUT (dBm)
OUTPUT (dBm)
–0.2
–0.3
–0.4
–0.5
–4
–5
–6
–0.7
–7
–0.8
–8
10M
100M
RL = 100
RF = RF = 200
VOUT = 300mV p-p
–3
–0.6
–0.9
1M
–9
1M
1G
10M
FREQUENCY (Hz)
100
60
80
PHASE
MARGIN
20
30
GAIN
0
–20
10
–40
0
RL = 100
–40
1k
10k
100k
1M
10M
100M
–70
SECOND HARMONIC
–80
THIRD HARMONIC
–100
–80
–30
–60
–90
–60
–20
RL = 1k
VOUT = 2V p-p
–50
OUTPUT (dBm)
40
PHASE MARGIN (Degrees)
GAIN (dB)
–20
–30
60
40
–10
1G
TPC 17. AD8047 Small Signal Frequency Response,
G = –1
70
20
100M
FREQUENCY (Hz)
TPC 14. AD8047 0.1 dB Flatness, G = +1
50
1G
TPC 16. AD8047 Large Signal Frequency Response,
G = +1
0.1
–0.1
100M
FREQUENCY (Hz)
–110
–100
1G
–120
10k
FREQUENCY (Hz)
100k
1M
10M
100M
FREQUENCY (Hz)
TPC 15. AD8047 Open-Loop Gain and Phase Margin
vs. Frequency
TPC 18. AD8047 Harmonic Distortion vs. Frequency,
G = +1
–6–
REV. A
AD8047/AD8048
0.5
–20
RL = 100
VOUT = 2V p-p
–40
0.3
–50
0.2
–60
–70
RL = 100
RF = 0
VOUT = 2V STEP
0.4
ERROR (%)
HARMONIC DISTORTION (dBc)
–30
SECOND HARMONIC
–80
0.1
0.0
–0.1
–0.2
–90
THIRD HARMONIC
–0.3
–100
–110
–0.4
–120
10k
–0.5
100k
10M
1M
100M
0
5
10
FREQUENCY (Hz)
–25
0.15
0.10
–40
ERROR (%)
HARMONIC DISTORTION (dBc)
45
RL = 100
RF = 0
VOUT = 2V STEP
0.20
–35
–45
THIRD HARMONIC
–50
0.05
0.00
–0.05
–0.10
–55
–0.15
SECOND HARMONIC
–0.20
–65
1.5
2.5
3.5
4.5
5.5
–0.25
6.5
0
2
4
OUTPUT SWING (V p-p)
TPC 20. AD8047 Harmonic Distortion vs. Output
Swing, G = +1
6
10
12
8
SETTLING TIME (s)
14
16
18
TPC 23. AD8047 Long-Term Settling Time, G = +1
0.04
17
0.02
15
INPUT NOISE VOLTAGE (nV/√Hz)
DIFF GAIN (%)
40
0.25
f = 200MHz
RL = 1k
RF = 0 FOR SOIC
–60
0.00
–0.02
–0.04
1st
DIFF PHASE (Degrees)
35
TPC 22. AD8047 Short-Term Settling Time, G = +1
TPC 19. AD8047 Harmonic Distortion vs. Frequency,
G = +1
–30
15
25
30
20
SETTLING TIME (ns)
2nd
3rd
4th
5th
6th
7th
8th
9th
10th 11th
0.04
0.02
0.00
13
11
9
7
5
–0.02
–0.04
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
3
10th 11th
10
100
1k
10k
FREQUENCY (Hz)
TPC 21. AD8047 Differential Gain and Phase Error,
G = +2, RL = 150 Ω, RF = 200 Ω, RIN = 200 Ω
REV. A
TPC 24. AD8047 Noise vs. Frequency
–7–
100k
AD8047/AD8048
7
7
6
6
RL = 100
RF = RIN = 200
VOUT = 300mV p-p
OUTPUT (dBm)
4
5
OUTPUT (dBm)
5
3
2
1
4
3
2
1
0
0
–1
–1
–2
–2
–3
–3
1M
10M
100M
FREQUENCY (Hz)
1M
1G
10M
1G
TPC 28. AD8048 Large Signal Frequency Response,
G = +2
6.5
1
6.4
0
RL = 100
RF = RIN = 200
VOUT = 300mV p-p
6.3
–1
OUTPUT (dBm)
6.2
6.1
6.0
5.9
–2
–4
–5
–6
5.7
–7
5.6
–8
1M
10M
100M
RL = 100
RF = RIN = 200
VOUT = 300mV p-p
–3
5.8
5.5
–9
1M
1G
10M
FREQUENCY (Hz)
TPC 26. AD8048 0.1 dB Flatness, G = +2
100
–20
80
80
–30
70
60
HARMONIC DISTORTION (dBc)
90
40
50
20
40
0
–20
RL = 100
20
–40
PHASE (Degrees)
60
30
–60
10
–80
0
–10
–100
–20
–120
1G
1k
10k
100k
1M
10M
FREQUENCY (Hz)
100M
100M
FREQUENCY (Hz)
1G
TPC 29. AD8048 Small Signal Frequency Response,
G = –1
PHASE
GAIN (dB)
100M
FREQUENCY (Hz)
TPC 25. AD8048 Small Signal Frequency Response,
G = +2
OUTPUT (dBm)
RL = 100
RF = RIN = 200
VOUT = 2V p-p
–40
RL = 1k
VOUT = 2V p-p
–50
–60
–70
SECOND HARMONIC
–80
–90
THIRD HARMONIC
–100
–110
–120
10k
100k
1M
FREQUENCY (Hz)
10M
100M
TPC 30. AD8048 Harmonic Distortion vs. Frequency,
G = +2
TPC 27. AD8048 Open-Loop Gain and Phase Margin
vs. Frequency
–8–
REV. A
AD8047/AD8048
0.5
–20
RL = 100
VOUT = 2V p-p
0.4
–40
0.3
–50
0.2
–60
0.1
–70
ERROR (%)
HARMONIC DISTORTION (dBc)
–30
SECOND HARMONIC
–80
0.0
–0.1
THIRD HARMONIC
–90
–0.2
–100
–0.3
–110
–0.4
–0.5
–120
10k
100k
10M
1M
FREQUENCY (Hz)
100M
0
5
10
25
30
35
40
0.20
f = 20MHz
RL = 1k
RF = 200
–25
–30
RL = 100
RF = 200
VOUT = 2V STEP
0.15
THIRD HARMONIC
0.10
ERROR (%)
–35
–40
–45
0.05
0.0
–0.05
–50
SECOND HARMONIC
–0.10
–55
–0.15
–60
–0.20
–65
–70
1.5
2.5
3.5
4.5
5.5
–0.25
6.5
0
2
4
OUTPUT SWING (V p-p)
TPC 32. AD8048 Harmonic Distortion vs. Output
Swing, G = +2
6
10
12
8
SETTLING TIME (s)
14
16
18
TPC 35. AD8048 Long-Term Settling Time 2 V
Step, G = +2
17
0.04
0.02
INPUT NOISE VOLTAGE (nV/√Hz)
15
0.00
–0.02
–0.04
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
10th 11th
0.04
0.02
0.00
13
11
9
7
5
–0.02
3
–0.04
1st
2nd
3rd
4th
5th
6th
7th
8th
9th
10th 11th
10
100
1k
10k
FREQUENCY (Hz)
TPC 33. AD8048 Differential Gain and Phase Error,
G = +2, RL = 150 Ω, RF = 200 Ω, RIN = 200 Ω
REV. A
45
0.25
–20
DIFF GAIN (%)
20
TPC 34. AD8048 Short-Term Settling Time, G = +2
–15
DIFF PHASE (Degrees)
15
SETTLING TIME (ns)
TPC 31. AD8048 Harmonic Distortion vs. Frequency,
G = +2
HARMONIC DISTORTION (dBc)
RL = 100
RF = 200
VOUT = 2V STEP
TPC 36. AD8048 Noise vs. Frequency
–9–
100k
AD8047/AD8048
100
100
VCM = 1V
RL = 100
80
80
70
70
60
60
50
50
40
40
30
30
20
100k
1M
10M
100M
VCM = 1V
RL = 100
90
CMRR (dB)
CMRR (dB)
90
20
100k
1G
1M
FREQUENCY (Hz)
100M
1G
TPC 40. AD8048 CMRR vs. Frequency
100
100
10
10
ROUT ()
ROUT ()
TPC 37. AD8047 CMRR vs. Frequency
10M
FREQUENCY (Hz)
1
0.1
1
0.1
0.01
10k
100k
1M
10M
100M
0.01
10k
1G
100k
1M
10M
100M
1G
FREQUENCY (Hz)
FREQUENCY (Hz)
TPC 38. AD8047 Output Resistance vs. Frequency,
G = +1
TPC 41. AD8048 Output Resistance vs. Frequency,
G = +2
90
90
80
80
–PSRR
+PSRR
70
+PSRR
–PSRR
60
PSRR (dB)
PSRR (dB)
60
70
50
40
50
40
30
30
20
20
10
10
0
10k
100k
1M
10M
100M
0
1G
3k
FREQUENCY (Hz)
10k
100k
1M
100M
500M
FREQUENCY (Hz)
TPC 39. AD8047 PSRR vs. Frequency
TPC 42. AD8048 PSRR vs. Frequency,
G = +2
–10–
REV. A
AD8047/AD8048
4.1
83.0
3.9
RL = 1k
+VOUT
82.0
AD8047
3.7
OUTPUT SWING (V)
–VOUT 
81.0
CMRR (–dB)
3.5
3.3
+VOUT
RL = 150
3.1
–VOUT 
80.0
AD8048
79.0
2.9
78.0
2.7
+VOUT
2.5
2.3
–60
–40
–20
77.0
RL = 50
–VOUT 
0
20
40
60
80
100
JUNCTION TEMPERATURE (C)
120
76.0
–60
140
–40
–20
0
20
40
60
80
100
120
140
JUNCTION TEMPERATURE (C)
TPC 43. AD8047/AD8048 Output Swing vs. Temperature
TPC 46. AD8047/AD8048 CMRR vs. Temperature
2600
8.0
2400
7.5
AD8048
SUPPLY CURRENT (mA)
OPEN-LOOP GAIN (V/V)
AD8048
2200
2000
1800
1600
1400
6V
6.5
AD8048
6.0
5V
5.0
–40
–20
0
20
40
60
80
100
120
4.5
–60
140
–40
–20
JUNCTION TEMPERATURE (C)
92
800
PSRR (–dB)
INPUT OFFSET VOLTAGE (V)
900
+PSRR
88
AD8048
86
84
–PSRR
AD8048
+PSRR
AD8047
82
80
78
–PSRR
–20
0
20
40
60
80
100
120
700
60
80
100
120
140
AD8048
600
AD8047
500
400
300
100
–60
140
JUNCTION TEMPERATURE (C)
TPC 45. AD8047/AD8048 PSRR vs. Temperature
REV. A
40
200
AD8047
–40
20
TPC 47. AD8047/AD8048 Supply Current vs.
Temperature
94
90
0
JUNCTION TEMPERATURE (C)
TPC 44. AD8047/AD8048 Open-Loop Gain vs.
Temperature
76
–60
AD8047
5V
5.5
AD8047
1200
1000
–60
AD8047
6V
7.0
–40
–20
0
20
40
60
80
100
JUNCTION TEMPERATURE (C)
120
140
TPC 48. AD8047/AD8048 Input Offset Voltage vs.
Temperature
–11–
AD8047/AD8048
For general voltage gain applications, the amplifier bandwidth
can be closely estimated as
ωO
f 3 dB ≅
  R 
2π 1+  F  
  RG  
THEORY OF OPERATION
General
The AD8047 and AD8048 are wide bandwidth, voltage feedback amplifiers. Since their open-loop frequency response follows
the conventional 6 dB/octave roll-off, their gain bandwidth
product is basically constant. Increasing their closed-loop gain
results in a corresponding decrease in small signal bandwidth.
This can be observed by noting the bandwidth specification
between the AD8047 (gain of 1) and AD8048 (gain of 2).
This estimation loses accuracy for gains of +2/–1 or lower due
to the amplifier’s damping factor. For these low gain cases, the
bandwidth will actually extend beyond the calculated value (see
Closed-Loop BW plots, TPCs 13 and 25).
Feedback Resistor Choice
The value of the feedback resistor is critical for optimum performance on the AD8047 and AD8048. For maximum flatness at a
gain of 2, RF and RG should be set to 200 Ω for the AD8048.
When the AD8047 is configured as a unity gain follower, RF
should be set to 0 Ω (no feedback resistor should be used) for
the plastic DIP and 66.5 Ω for the SOIC.
G = 1+
where NG is the Noise Gain (1 + RF/RG) of the circuit. For
most voltage gain applications, this should be the case.
RF
10F
+VS
RF
As a general rule, capacitor CF will not be required if
NG
(RF RG ) × CI ≤
4 ωO
RG
VIN
7
3
RTERM
2
CF
0.1F
AD8047/
AD8048
VOUT
6
0.1F
4
II
RG
–VS
CI
AD8047
VOUT
10F
RF
Figure 5. Transimpedance Configuration
Figure 3. Noninverting Operation
Pulse Response
G= –
RF
7
3
RG
RG
VIN
0.1F
AD8047/
AD8048
2
RTERM
4
–VS
Unlike a traditional voltage feedback amplifier, where the slew
speed is dictated by its front end dc quiescent current and gain
bandwidth product, the AD8047 and AD8048 provide on
demand current that increases proportionally to the input step
signal amplitude. This results in slew rates (1000 V/µs) comparable to wideband current feedback designs. This, combined
with relatively low input noise current (1.0 pA/√Hz), gives the
AD8047 and AD8048 the best attributes of both voltage and
current feedback amplifiers.
10F
+VS
VOUT
6
0.1F
10F
RF
Large Signal Performance
Figure 4. Inverting Operation
When the AD8047 is used in the transimpedance (I to V) mode,
such as in photodiode detection, the values of RF and diode
capacitance (CI) are usually known. Generally, the value of RF
selected will be in the kΩ range, and a shunt capacitor (CF)
across RF will be required to maintain good amplifier stability.
The value of CF required to maintain optimal flatness (<1 dB
peaking) and settling time can be estimated as
[
2
CF ≅ (2 ωO CI RF – 1)/ωO RF
2
]
1/2
where ␻O is equal to the unity gain bandwidth product of
the amplifier in rad/sec, and CI is the equivalent total input
capacitance at the inverting input. Typically, ␻O = 800 × 106 rad/sec
(see Open-Loop Frequency Response curve, TPC 15).
As an example, choosing RF = 10 kΩ and CI = 5 pF requires
CF to be 1.1 pF (Note: CI includes both source and parasitic
circuit capacitance). The bandwidth of the amplifier can be
estimated using the CF calculated as
f 3 dB
1.6
≅
2πR F CF
The outstanding large signal operation of the AD8047 and
AD8048 is due to a unique, proprietary design architecture.
In order to maintain this level of performance, the maximum
180 V-MHz product must be observed (e.g., @ 100 MHz,
VO ≤ 1.8 V p-p) on the AD8047 and the 250 V-MHz product
must be observed on the AD8048.
Power Supply Bypassing
Adequate power supply bypassing can be critical when optimizing the performance of a high frequency circuit. Inductance in
the power supply leads can form resonant circuits that produce
peaking in the amplifier’s response. In addition, if large current
transients must be delivered to the load, then bypass capacitors
(typically greater than 1 µF) will be required to provide the best
settling time and lowest distortion. A parallel combination of at
least 4.7 µF, and between 0.1 µF and 0.01 µF, is recommended.
Some brands of electrolytic capacitors will require a small series
damping resistor ≈4.7 Ω for optimum results.
Driving Capacitive Loads
The AD8047/AD8048 have excellent cap load drive capability
for high speed op amps, as shown in Figures 7 and 9. However,
when driving cap loads greater than 25 pF, the best frequency
response is obtained by the addition of a small series resistance.
–12–
REV. A
AD8047/AD8048
It is worth noting that the frequency response of the circuit
when driving large capacitive loads will be dominated by the
passive roll-off of RSERIES and CL.
margin (65°), low noise current (1.0 pA/√Hz), and slew rate
(1000 V/µs) give higher performance capabilities to these applications over previous voltage feedback designs.
With a settling time of 30 ns to 0.01% and 13 ns to 0.1%, the
devices are an excellent choice for DAC I/V conversion. The
same characteristics along with low harmonic distortion make
them a good choice for ADC buffering/amplification. With
superb linearity at relatively high signal frequencies, the AD8047
and AD8048 are ideal drivers for ADCs up to 12 bits.
RF
AD8047
RSERIES
RL
1k
CL
Operation as a Video Line Driver
The AD8047 and AD8048 have been designed to offer outstanding performance as video line drivers. The important
specifications of differential gain (0.01%) and differential phase
(0.02°) meet the most exacting HDTV demands for driving
video loads.
Figure 6. Driving Capacitive Loads
200
200
10F
+VS
0.1F
7
2
3
VIN
500mV
5ns
75
AD8047/
AD8048
75
CABLE
75
CABLE
6
0.1F
75
4
75
VOUT
10F
–VS
Figure 7. AD8047 Large Signal Transient Response;
VO = 2 V p-p, G = +1, RF = 0 Ω, RSERIES = 0 Ω, CL = 27 pF
Figure 10. Video Line Driver
Active Filters
RF
RIN
AD8048
The wide bandwidth and low distortion of the AD8047 and
AD8048 are ideal for the realization of higher bandwidth active
filters. These characteristics, while being more common in many
current feedback op amps, are offered in the AD8047 and AD8048
in a voltage feedback configuration. Many active filter configurations are not realizable with current feedback amplifiers.
RSERIES
RL
1k
CL
A multiple feedback active filter requires a voltage feedback
amplifier and is more demanding of op amp performance than
other active filter configurations such as the Sallen-Key. In
general, the amplifier should have a bandwidth that is at least
10 times the bandwidth of the filter if problems due to phase
shift of the amplifier are to be avoided.
Figure 8. Driving Capacitive Loads
Figure 11 is an example of a 20 MHz low-pass multiple feedback active filter using an AD8048.
C1
50pF
R4
154
500mV
VIN
5ns
R1
154
R3
78.7
C2
100pF
Figure 9. AD8048 Large Signal Transient Response;
VO = 2 V p-p, G = +2, RF = RIN = 200 Ω, RSERIES = 0 Ω,
CL = 27 pF
0.1F
1
7
2
AD8048
3
6
5
0.1F
4
100
10F
–5V
Figure 11. Active Filter Circuit
APPLICATIONS
The AD8047 and AD8048 are voltage feedback amplifiers well
suited for such applications as photodetectors, active filters, and
log amplifiers. The devices’ wide bandwidth (260 MHz), phase
REV. A
10F
+5V
–13–
VOUT
AD8047/AD8048
Choose
Layout Considerations
FO = Cutoff Frequency = 20 MHz
␣ = Damping Ratio = 1/Q = 2
The specified high speed performance of the AD8047 and
AD8048 requires careful attention to board layout and component selection. Proper RF design techniques and low-pass
parasitic component selection are mandatory.
H = Absolute Value of Circuit Gain = –R4 = 1
R1
Then,
The PCB should have a ground plane covering all unused portions of the component side of the board to provide a low
impedance path. The ground plane should be removed from the
area near the input pins to reduce stray capacitance.
k = 2 π FO C1
4 C1(H +1)
α2
α
R1 =
2 HK
C2 =
R3 =
Chip capacitors should be used for the supply bypassing (see
Figure 12). One end should be connected to the ground plane
and the other within 1/8 inch of each power pin. An additional
large (0.47 µF to 10 µF) tantalum electrolytic capacitor should
be connected in parallel, though not necessarily so close, to the
supply current for fast, large signal changes at the output.
α
2 K (H +1)
R4 = H(R1)
The feedback resistor should be located close to the inverting
input pin in order to keep the stray capacitance at this node to a
minimum. Capacitance variations of less than 1 pF at the inverting
input will significantly affect high speed performance.
A/D Converter Driver
As A/D converters move toward higher speeds with higher resolutions, there becomes a need for high performance drivers that
will not degrade the analog signal to the converter. It is desirable from a system’s standpoint that the A/D be the element in
the signal chain that ultimately limits overall distortion. This
places new demands on the amplifiers used to drive fast, high
resolution A/Ds.
Stripline design techniques should be used for long signal traces
(greater than about 1 inch). These should be designed with a
characteristic impedance of 50 Ω or 75 Ω and be properly terminated at each end.
With high bandwidth, low distortion, and fast settling time,
the AD8047 and AD8048 make high performance A/D drivers
for advanced converters. Figure 12 is an example of an AD8047
used as an input driver for an AD872A, a 12-bit, 10 MSPS
A/D converter.
+5V DIGITAL
+5V ANALOG
10
7
DVDD
4
0.1F
+5V ANALOG
5
6
DGND
+5V DIGITAL
AVDD
22
DRVDD
AGND
23
DRGND
10F
AD872A
0.1F
AD8047
ANALOG IN
3
1
6
MSB
BIT2
BIT3
BIT4
BIT5
BIT6
BIT7
BIT8
BIT9
BIT10
BIT11
BIT12
VINA
0.1F
4
2
10F
VINB
27
–5V
ANALOG
REF GND
0.1F
28
REF IN
26
1F
19
18
17
16
15
14
13
12
11
10
9
8
AGND
REF OUT
AVSS
20
OTR
7
0.1F
CLOCK INPUT
21
CLK
2
0.1F
49.9
DIGITAL OUTPUT
24
AVSS
3
0.1F
25
0.1F
–5V ANALOG
Figure 12. AD8047 Used as Driver for an AD872A, a 12-Bit, 10 MSPS A/D Converter
–14–
REV. A
AD8047/AD8048
OUTLINE DIMENSIONS
8-Lead Plastic Dual In-Line Package [PDIP]
(N-8)
Dimensions shown in inches and (millimeters)
0.375 (9.53)
0.365 (9.27)
0.355 (9.02)
8
5
1
4
0.295 (7.49)
0.285 (7.24)
0.275 (6.98)
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.100 (2.54)
BSC
0.015
(0.38)
MIN
0.180
(4.57)
MAX
0.150 (3.81)
0.130 (3.30)
0.110 (2.79)
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
0.150 (3.81)
0.135 (3.43)
0.120 (3.05)
0.015 (0.38)
0.010 (0.25)
0.008 (0.20)
SEATING
PLANE
0.060 (1.52)
0.050 (1.27)
0.045 (1.14)
COMPLIANT TO JEDEC STANDARDS MO-095AA
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
8-Lead Standard Small Outline Package [SOIC]
(R-8)
Dimensions shown in millimeters and (inches)
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
8
5
1
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
SEATING
0.10
PLANE
6.20 (0.2440)
5.80 (0.2284)
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.31 (0.0122)
0.50 (0.0196)
45
0.25 (0.0099)
8
0.25 (0.0098) 0 1.27 (0.0500)
0.40 (0.0157)
0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
REV. A
–15–
AD8047/AD8048
Revision History
Location
Page
7/03—Data Sheet changed from REV. 0 to REV. A.
Deleted Evaluation Board Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Universal
Updated ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
–16–
REV. A
C01061–0–7/03(A)
Renumbered Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Universal