AD8047AR [ADI]
250 MHz, General Purpose Voltage Feedback Op Amps; 250兆赫，通用电压反馈运算放大器
| 型号： | AD8047AR |
| 厂家： | 
ADI |
| 描述： | 250 MHz, General Purpose Voltage Feedback Op Amps |
| 文件： | 总16页 (文件大小：480K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
250 MHz, General Purpose
Voltage Feedback Op Amps
a
AD8047/AD8048
FEATURES
Wide Bandwidth
Small Signal
FUNCTIONAL BLOCK DIAGRAM
8-Pin Plastic Mini-DIP (N), Cerdip (Q)
and SO (R) Packages
AD8047, G = +1 AD8048, G = +2
250 MHz
260 MHz
160 MHz
Large Signal (2 V p-p) 130 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
8
7
6
5
1
2
3
4
NC
–INPUT
+INPUT
NC
+V
S
OUTPUT
NC
AD8047/48
–V
S
(Top View)
High Speed
NC = NO CONNECT
Slew Rate 750 V/µs (AD8047), 1000 V/µs (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
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-pin plastic
DIP and SOIC packages.
Active Filters/Integrators
PRODUCT DESCRIPTION
The AD8047 and AD8048 are very high speed and wide band-
width 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 and 250 MHz small sig-
nal and 130 MHz large signal bandwidths.
1V
5ns
Figure 1. AD8047 Large Signal Transient Response,
VO = 4 V p-p, G = +1
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
© Analog Devices, Inc., 1995
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
AD8047/AD8048–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS(±VS = ±5 V; RLOAD = 100 Ω; AV = 1 (AD8047); AV = 2 (AD8048), unless otherwise noted)
AD8047A
AD8048A
Parameter
Conditions
Min Typ Max Min Typ Max Units
DYNAMIC PERFORMANCE
Bandwidth (–3 dB)
Small Signal
V
OUT ≤ 0.4 V p-p
VOUT = 2 V p-p
OUT = 300 mV p-p
8047, RF = 0 Ω; 8048, RF = 200 Ω
OUT = 4 V Step
OUT = 0.5 V Step
OUT = 4 V Step
170
100
250
130
180 260
135 160
MHz
MHz
Large Signal1
Bandwidth for 0.1 dB Flatness
V
35
50
740 1000
1.2
MHz
V/µs
ns
Slew Rate, Average +/–
Rise/Fall Time
V
V
V
475
750
1.1
4.3
3.2
ns
Settling Time
To 0.1%
To 0.01%
V
OUT = 2 V Step
13
30
13
30
ns
ns
VOUT = 2 V Step
HARMONIC/NOISE PERFORMANCE
2nd Harmonic Distortion
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
–48
–60
–56
–65
3.8
dBc
dBc
dBc
dBc
nV/√Hz
pA/√Hz
3rd Harmonic Distortion
Input Voltage Noise
Input Current Noise
1.0
1.0
Average Equivalent Integrated
Input Noise Voltage
Differential Gain Error (3.58 MHz)
Differential Phase Error (3.58 MHz)
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
3
4
1
3
4
mV
mV
µV/°C
µA
µA
µA
T
MIN–TMAX
Offset Voltage Drift
Input Bias Current
±5
1
±5
1
3.5
6.5
2
3.5
6.5
2
T
MIN–TMAX
MIN–TMAX
Input Offset Current
0.5
0.5
T
3
3
µA
Common-Mode Rejection Ratio
Open-Loop Gain
V
V
CM = ±2.5 V
OUT = ±2.5 V
74
58
54
80
62
74
65
56
80
68
dB
dB
dB
TMIN–TMAX
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
500
1.5
±3.4
500
1.5
±3.4
kΩ
pF
V
Input Common-Mode Voltage Range
OUTPUT CHARACTERISTICS
Output Voltage Range, RL = 150 Ω
Output Current
Output Resistance
Short Circuit Current
±2.8 ±3.0
±2.8 ±3.0
V
mA
Ω
50
0.2
130
50
0.2
130
mA
POWER SUPPLY
Operating Range
Quiescent Current
±3.0 ±5.0 ±6.0 ±3.0 ±5.0 ±6.0
V
5.8 6.6
7.5
5.9 6.6
7.5
mA
mA
dB
TMIN–TMAX
Power Supply Rejection Ratio
72
78
72
78
NOTES
1See Max Ratings and Theory of Operation sections of data sheet.
2Measured at AV = 50.
3Measured with respect to the inverting input.
Specifications subject to change without notice.
REV. 0
–2–
AD8047/AD8048
MAXIMUM POWER DISSIPATION
ABSOLUTE MAXIMUM RATINGS1
The maximum power that can be safely dissipated by these de-
vices is limited by the associated rise in junction temperature.
The maximum safe junction temperature for plastic encapsu-
lated devices is determined by the glass transition temperature
of the plastic, approximately +150°C. Exceeding this limit tem-
porarily may cause a shift in parametric performance due to a
change in the stresses exerted on the die by the package. Exceed-
ing a junction temperature of +175°C for an extended period can
result in device failure.
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.6 V
Voltage Swing × Bandwidth Product (AD8047) . . . 180 V – MHz
(AD8048) . . . 250 V– MHz
Internal Power Dissipation2
Plastic Package (N) . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Watts
Small Outline Package (R) . . . . . . . . . . . . . . . . . . . 0.9 Watts
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
While the AD8047 and AD8048 are internally short circuit pro-
tected, this may not be sufficient to guarantee that the maxi-
mum junction temperature (+150°C) is not exceeded under all
conditions. To ensure proper operation, it is necessary to ob-
serve the maximum power derating curves.
NOTES
1Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent 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.
2Specification is for device in free air:
2.0
T
= +150°C
J
8-PIN MINI-DIP PACKAGE
1.5
1.0
0.5
8-Pin Plastic DIP Package: θJA
= 90°C/Watt
8-Pin SOIC Package: θJA = 140°C/Watt
METALIZATION PHOTOS
Dimensions shown in inches and (mm).
Connect Substrate to –VS.
8-PIN SOIC PACKAGE
AD8047
+V
S
0
–50 –40 –30 –20 –10
0 10 20 30 40 50 60 70 80 90
AMBIENT TEMPERATURE –
°C
Figure 2. Plot of Maximum Power Dissipation vs.
Temperature
0.045
(1.14)
V
OUT
ORDERING GUIDE
–IN
Temperature
Range
Package
Description Option*
Package
–V
S
+IN
Model
0.044
(1.13)
AD8047AN
AD8047AR
AD8047-EB
–40°C to +85°C
–40°C to +85°C
Plastic DIP N-8
SOIC
R-8
AD8048
+V
Evaluation
Board
S
AD8048AN
AD8048AR
AD8048-EB
–40°C to +85°C
–40°C to +85°C
Plastic DIP N-8
SOIC
R-8
Evaluation
Board
0.045
–OUT (1.14)
*N = Plastic DIP; R= SOIC (Small Outline Integrated Circuit)
–IN
–V
S
+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 these devices feature 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.
WARNING!
ESD SENSITIVE DEVICE
REV. 0
–3–
AD8047/AD8048
AD8047–Typical Characteristics
R
F
10µF
+VS
10µF
+V
S
PULSE
GENERATOR
0.1µF
0.1µF
7
PULSE
GENERATOR
T
/T = 500ps
F
R
2
3
R
IN
7
V
6
VOUT
2
3
AD8047
4
IN
TR/TF = 500ps
VIN
0.1µF
V
6
AD8047
4
OUT
R
= 66.5Ω
T
RL = 100Ω
0.1µF
10µF
RT = 49.9Ω
R
= 100Ω
L
100Ω
10µF
–VS
–V
S
Figure 3. Noninverting Configuration, G = +1
Figure 6. Inverting Configuration, G = –1
1V
5ns
1V
5ns
Figure 4. Large Signal Transient Response;
VO = 4 V p-p, G = +1
Figure 7. Large Signal Transient Response;
VO = 4 V p-p, G = –1, RF = RIN = 200 Ω
100mV
5ns
100mV
5ns
Figure 5. Small Signal Transient Response;
VO = 400 mV p-p, G = +1
Figure 8. Small Signal Transient Response;
VO = 400 mV p-p, G = –1, RF = RIN = 200 Ω
–4–
REV. 0
AD8047/AD8048
AD8048–Typical Characteristics
RF
R
F
PULSE
GENERATOR
10µF
0.1µF
10µF
0.1µF
+VS
+V
7
PULSE
GENERATOR
S
TR/T F = 500ps
RIN
T
/T = 500ps
F
R
R
7
IN
2
3
V
IN
2
3
VOUT
6
AD8048
4
V
6
R
T
= 66.5Ω
AD8048
4
OUT
0.1µF
0.1µF
VIN
RL = 100Ω
R
L
= 100Ω
RT = 49.9Ω
R = 100Ω
S
10µF
10µF
–VS
–V
S
Figure 9. Noninverting Configuration, G = +2
Figure 12. Inverting Configuration, G= –1
1V
1V
5ns
5ns
Figure 10. Large Signal Transient Response;
Figure 13. Large Signal Transient Response;
VO = 4 V p-p, G = +2, RF = RIN = 200 Ω
VO = 4 V p-p, G = –1, RF = RIN = 200 Ω
100mV
5ns
100mV
5ns
Figure 11. Small Signal Transient Response;
Figure 14. Small Signal Transient Response;
VO = 400 mV p-p, G = +2, RF = RIN = 200 Ω
VO = 400 mV p-p, G = –1, RF = RIN = 200 Ω
REV. 0
–5–
AD8047/AD8048
AD8047–Typical Characteristics
1
1
0
0
–1
–1
–2
–3
–4
–5
–6
R
R
R
V
= 100Ω
L
F
F
R
R
R
= 100Ω
= 0Ω FOR DIP
= 66.5Ω FOR SOIC
= 0Ω FOR DIP
= 66.5Ω FOR SOIC
= 2V p-p
L
–2
–3
–4
–5
–6
F
F
OUT
V
= 300mV p-p
OUT
–7
–8
–9
–7
–8
–9
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY – Hz
FREQUENCY – Hz
Figure 15. AD8047 Small Signal Frequency Response
G = +1
Figure 18. AD8047 Large Signal Frequency Response,
G = +1
0.1
0
1
0
–0.1
–1
R
R
R
= 100Ω
= 0Ω FOR DIP
= 66.5Ω FOR SOIC
L
–0.2
–0.3
–0.4
R
R
V
= 100Ω
–2
–3
–4
–5
–6
L
F
F
= R = 200Ω
IN
F
= 300mV p-p
OUT
V
= 300mV p-p
OUT
–0.5
–0.6
–0.7
–0.8
–0.9
–7
–8
–9
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY – Hz
FREQUENCY – Hz
Figure 16. AD8047 0.1 dB Flatness, G = +1
Figure 19. AD8047 Small Signal Frequency Response,
G = –1
100
70
60
–20
80
R
V
= 1kΩ
L
–30
= 2V p-p
PHASE
MARGIN
OUT
60
40
20
0
50
40
–40
–50
–60
–70
–80
–90
30
GAIN
20
2ND HARMONIC
–20
–40
10
0
R
= 100Ω
3RD HARMONIC
L
–60
–80
–10
–20
–30
–100
–110
–120
–100
1k
10k
100k
1M
10M
100M
1G
10k
100k
1M
10M
100M
FREQUENCY – Hz
FREQUENCY – Hz
Figure 17. AD8047 Open-Loop Gain and Phase Margin vs.
Frequency
Figure 20. AD8047 Harmonic Distortion vs. Frequency,
G = +1
–6–
REV. 0
AD8047/AD8048
–20
–30
0.5
R
= 100Ω
= 2V p-p
L
V
R
R
V
= 100Ω
= 0Ω
OUT
0.4
0.3
L
F
–40
–50
–60
–70
–80
–90
= 2V STEP
OUT
0.2
0.1
2ND HARMONIC
0.0
–0.1
–0.2
–0.3
3RD HARMONIC
–100
–110
–120
–0.4
–0.5
10k
100k
1M
FREQUENCY – Hz
10M
100M
0
5
10
15
20
25
30
35
40
45
SETTLING TIME – ns
Figure 21. AD8047 Harmonic Distortion vs. Frequency,
G = +1
Figure 24. AD8047 Short-Term Settling Time, G = +1
–25
0.25
R
R
V
= 100Ω
= 0Ω
0.20
0.15
L
F
f = 20MHz
–30
–35
–40
–45
–50
–55
R
R
= 1kΩ
= 0Ω
L
F
= 2V STEP
OUT
0.10
0.05
0.00
3RD HARMONIC
2ND HARMONIC
4.5
–0.05
–0.10
–0.15
–60
–65
–0.20
–0.25
0
2
4
6
8
10
12
14
16
18
1.6
2.5
3.5
5.5
6.5
SETTLING TIME – µs
OUTPUT SWING – V p-p
Figure 25. AD8047 Long-Term Settling Time, G = +1
Figure 22. AD8047 Harmonic Distortion vs. Output Swing,
G = +1
17
0.04
0.02
15
13
11
9
0.00
–0.02
–0.04
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th
0.04
0.02
7
0.00
5
–0.02
–0.04
3
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th
10
100
1k
10k
100k
FREQUENCY – Hz
Figure 26. AD8047 Noise vs. Frequency
Figure 23. AD8047 Differential Gain and Phase Error,
G = +2, RL = 150 Ω, RF = 200 Ω, RIN = 200 Ω
REV. 0
–7–
AD8047/AD8048
AD8048–Typical Characteristics
7
6
5
7
6
5
R
R
V
= 100Ω
L
F
R
R
V
= 100Ω
L
F
= R = 200Ω
IN
4
3
= R = 200Ω
IN
= 2V p-p
4
3
OUT
= 300mV p-p
OUT
2
1
0
2
1
0
–1
–2
–3
–1
–2
–3
1M
10M
100M
1G
1M
10M
100M
1G
FREQUENCY – Hz
FREQUENCY – Hz
Figure 27. AD8048 Small Signal Frequency Response,
G = +2
Figure 30. AD8048 Large Signal Frequency Response,
G = +2
6.5
1
0
6.4
6.3
R
R
= 100Ω
L
= R = 200Ω
IN
F
V
= 300mV p-p
OUT
–1
R
R
V
= 100Ω
L
= R = 200Ω
F
IN
6.2
6.1
= 300mV p-p
–2
–3
OUT
6.0
5.9
5.8
–4
–5
–6
5.7
5.6
5.5
–7
–8
–9
1M
10M
100M
1G
1M
10M
100M
FREQUENCY – Hz
1G
FREQUENCY – Hz
Figure 31. AD8048 Small Signal Frequency Response,
G = –1
Figure 28. AD8048 0.1 dB Flatness, G = +2
100
90
80
70
–20
80
60
40
20
R
L
= 1kΩ
–30
V
= 2V p-p
OUT
–40
–50
–60
–70
–80
–90
PHASE
60
50
40
0
2ND HARMONIC
–20
–40
–60
–80
30
20
10
0
R
= 100Ω
L
3RD HARMONIC
–100
–110
–120
–100
–120
–10
–20
1k
10k
100k
1M
10M
100M
1G
10k
100k
1M
10M
100M
FREQUENCY – Hz
FREQUENCY – Hz
Figure 29. AD8048 Open-Loop Gain and Phase Margin vs.
Frequency
Figure 32. AD8048 Harmonic Distortion vs. Frequency,
G = +2
–8–
REV. 0
AD8047/AD8048
0.5
–20
–30
R
R
V
= 100Ω
= 200Ω
L
F
R
= 100Ω
= 2V p-p
0.4
0.3
L
V
OUT
= 2V STEP
OUT
–40
–50
–60
–70
–80
–90
0.2
0.1
0.0
2ND HARMONIC
–0.1
–0.2
–0.3
3RD HARMONIC
–100
–110
–120
–0.4
–0.5
0
5
10
15
20
25
30
35
40
45
10k
100k
1M
FREQUENCY – Hz
10M
100M
SETTLING TIME – ns
Figure 36. AD8048 Short-Term Settling Time, G = +2
Figure 33. AD8048 Harmonic Distortion vs. Frequency,
G = +2
–15
0.25
R
R
= 100Ω
= 200Ω
= 2V STEP
–20
L
0.20
0.15
f = 20MHz
F
R
= 1kΩ
–25
–30
L
F
V
OUT
3RD HARMONIC
R
= 200
0.10
–35
–40
–45
–50
–55
–60
0.05
0.0
–0.05
–0.10
–0.15
2ND HARMONIC
–0.20
–0.25
–65
–70
1.5
2.5
3.5
4.5
5.5
6.5
0
2
4
6
8
10
12
14
16
18
OUTPUT SWING – Volts p-p
SETTLING TIME – µs
Figure 34. AD8048 Harmonic Distortion vs. Output Swing,
G = +2
Figure 37. AD8048 Long-Term Settling Time 2 V Step,
G = +2
17
0.04
0.02
15
13
11
9
0.00
–0.02
–0.04
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th
0.04
0.02
7
0.00
5
–0.02
–0.04
3
1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th
10
100
1k
10k
100k
FREQUENCY – Hz
Figure 35. AD8048 Differential Gain and Phase Error,
Figure 38. AD8048 Noise vs. Frequency
G = +2, RL = 150 Ω, RF = 200 Ω, RIN = 200 Ω
REV. 0
–9–
AD8047/AD8048–Typical Characteristics
100
100
90
∆V
= 1V
∆V
R
L
= 1V
CM
= 100Ω
CM
= 100Ω
90
R
L
80
70
80
70
60
50
40
60
50
40
30
20
30
20
100k
1M
10M
100M
1G
100k
1M
10M
100M
1G
FREQUENCY – Hz
FREQUENCY – Hz
Figure 39. AD8047 CMRR vs. Frequency
Figure 42. AD8048 CMRR vs. Frequency
100
100
10
1
10
1
0.1
0.1
0.01
0.01
10k
100k
1M
10M
100M
1G
10k
100k
1M
10M
100M
1G
FREQUENCY – Hz
FREQUENCY – Hz
Figure 43. AD8048 Output Resistance vs. Frequency,
G = +2
Figure 40. AD8047 Output Resistance vs. Frequency,
G = +1
90
90
80
–PSRR
80
+PSRR
70
70
+PSRR
60
–PSRR
60
50
40
30
20
50
40
30
20
10
0
10
0
10k
100k
1M
10M
100M
1G
3k
10k
100k
1M
100M
500M
FREQUENCY – Hz
FREQUENCY – Hz
Figure 41. AD8047 PSRR vs. Frequency
Figure 44. AD8048 PSRR vs. Frequency,
G = +2
–10–
REV. 0
AD8047/AD8048
83.0
4.1
3.9
3.7
3.5
3.3
3.1
2.9
2.7
82.0
81.0
R
= 1kΩ
+V
OUT
L
AD8047
AD8048
–V
OUT
80.0
79.0
78.0
+V
OUT
R
L
= 150Ω
–V
OUT
+V
OUT
77.0
76.0
R
= 50Ω
2.5
2.3
L
–V
OUT
–60 –40 –20
0
20
40
60
80
100 120 140
–60 –40 –20
0
20
40
60
80
100 120 140
JUNCTION TEMPERATURE –
°
C
JUNCTION TEMPERATURE – °C
Figure 45. AD8047/AD8048 Output Swing vs. Temperature
Figure 48. AD8047/AD8048 CMRR vs. Temperature
8.0
2600
2400
AD8048
7.5
AD8047
AD8048
±6V
2200
7.0
2000
1800
1600
±6V
6.5
AD8048
6.0
AD8047
±5V
5.5
±5V
5.0
1400
AD8047
1200
1000
4.5
–60 –40 –20
0
20
40
60
80
100 120 140
–60 –40 –20
0
20
40
60
80
100 120 140
JUNCTION TEMPERATURE – °C
JUNCTION TEMPERATURE –
°C
Figure 46. AD8047/AD8048 Open-Loop Gain vs.
Temperature
Figure 49. AD8047/AD8048 Supply Current vs.
Temperature
94
92
900
800
90
88
86
84
82
80
78
76
+PSRR
700
AD8048
AD8047
AD8048
AD8048
600
500
400
–PSRR
+PSRR
AD8047
AD8047
300
200
100
–PSRR
–60 –40 –20
0
20
40
60
80
100 120 140
–60 –40 –20
0
20
40
60
80
100 120 140
JUNCTION TEMPERATURE – °C
JUNCTION TEMPERATURE – °C
Figure 50. AD8047/AD8048 Input Offset Voltage vs.
Temperature
Figure 47. AD8047/AD8048 PSRR vs. Temperature
REV. 0
–11–
AD8047/AD8048
THEORY OF OPERATION
General
For general voltage gain applications, the amplifier bandwidth
can be closely estimated as:
The AD8047 and AD8048 are wide bandwidth, voltage feed-
back amplifiers. Since their open-loop frequency response fol-
lows 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).
ωO
f3 dB
RF
2π 1+
RG
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, Figures 15 and 26).
Feedback Resistor Choice
The value of the feedback resistor is critical for optimum perfor-
mance 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.
As a rule of thumb, capacitor CF will not be required if:
NG
(RFʈRG )× CI ≤
4 ωO
where NG is the Noise Gain (1 + RF/RG) of the circuit. For
most voltage gain applications, this should be the case.
+V
S
10µF
R
F
R
F
G = 1 +
R
G
7
C
F
V
IN
3
2
0.1µF
6
V
OUT
AD8047/48
R
TERM
0.1µF
4
V
AD8047
OUT
I
C
I
I
R
G
10µF
–V
S
R
F
Figure 53. Transimpedance Configuration
Pulse Response
Figure 51. Noninverting Operation
+VS
10µF
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 de-
mand” current that increases proportionally to the input “step”
signal amplitude. This results in slew rates (1000 V/µs) compa-
rable 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.
RF
G = –
7
RG
3
2
0.1µF
VOUT
6
AD8047/48
0.1µF
4
RG
VIN
RTERM
10µF
–VS
RF
Figure 52. Inverting Operation
Large Signal Performance
When the AD8047 is used in the transimpedance (I to V) mode,
such as in photodiode detection, the value 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:
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 250 V-MHz product on
the AD8048.
Power Supply Bypassing
1/2
2
2
CF (2 ωOCI RF –1)/ωO RF
Adequate power supply bypassing can be critical when optimiz-
ing 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.
[
]
where ωO 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 ωO = 800 × 106
rad/sec (see Open-Loop Frequency Response curve, Fig-
ure 17).
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:
Driving Capacitive Loads
The AD8047/AD8048 have excellent cap load drive capability
for high speed op amps as shown in Figures 55 and 57. How-
ever, when driving cap loads greater than 25 pF, the best fre-
quency response is obtained by the addition of a small series
resistance. It is worth noting that the frequency response of the
1. 6
f3 dB
2πR F C F
–12–
REV. 0
AD8047/AD8048
circuit when driving large capacitive loads will be dominated by
the passive roll-off of RSERIES and CL.
(1000 V/µs) give higher performance capabilities to these appli-
cations over previous voltage feedback designs.
R
F
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 su-
perb linearity at relatively high signal frequencies, the AD8047
and AD8048 are ideal drivers for ADCs up to 12 bits.
R
SERIES
AD8047
R
L
C
L
1kΩ
Operation as a Video Line Driver
The AD8047 and AD8048 have been designed to offer out-
standing 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 54. Driving Capacitive Loads
200Ω
200Ω
10µF
+V
S
0.1µF
7
75Ω
CABLE
2
3
75Ω
75Ω
CABLE
AD8047/
AD8048
6
V
OUT
V
0.1µF
75Ω
IN
4
500mV
5ns
75Ω
10µF
Figure 55. AD8047 Large Signal Transient Response;
–V
S
VO = 2 V p-p, G = +1, RF = 0 Ω, RSERIES = 0 Ω, CL = 27 pF
Figure 58. Video Line Driver
R
F
Active Filters
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 configu-
rations are not realizable with current feedback amplifiers.
R
SERIES
R
IN
AD8048
R
L
C
L
1kΩ
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
ten times the bandwidth of the filter if problems due to phase
shift of the amplifier are to be avoided.
Figure 56. Driving Capacitive Loads
Figure 59 is an example of a 20 MHz low pass multiple feed-
back active filter using an AD8048.
+5V
C1
50pF
10µF
R4
154Ω
R1
R3
0.1µF
154Ω
78.7Ω
1
V
IN
7
2
500mV
5ns
C2
100pF
V
OUT
6
AD8048
100Ω
0.1µF
5
3
4
Figure 57. AD8048 Large Signal Transient Response;
VO = 2 V p-p, G = +2, RF = RIN = 200 Ω, RSERIES = 0 Ω,
CL = 27 pF
10µF
–5V
Figure 59. Active Filter Circuit
APPLICATIONS
Choose:
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
margin (65°), low noise current (1.0 pA/√Hz), and slew rate
FO = Cutoff Frequency = 20 MHz
α = Damping Ratio = 1/Q = 2
REV. 0
–13–
AD8047/AD8048
H = Absolute Value of Circuit Gain =
–R4
R1
= 1
The PCB should have a ground plane covering all unused por-
tions of the component side of the board to provide a low im-
pedance path. The ground plane should be removed from the
area near the input pins to reduce stray capacitance.
Then:
k = 2 π FO C1
4 C1(H +1)
Chip capacitors should be used for the supply bypassing (see
Figure 60). 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–10 µF) tantalum electrolytic capacitor should be
connected in parallel, though not necessarily so close, to supply
current for fast, large signal changes at the output.
C2 =
R1 =
R3 =
α2
α
2 HK
α
2 K (H +1)
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 in-
verting input will significantly affect high speed performance.
R4 = H(R1)
A/D Converter Driver
As A/D converters move toward higher speeds with higher reso-
lutions, there becomes a need for high performance drivers that
will not degrade the analog signal to the converter. It is desir-
able 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 termi-
nated at each end.
Evaluation Board
An evaluation board for both the AD8047 and AD8048 is avail-
able that has been carefully laid out and tested to demonstrate
that the specified high speed performance of the device can be
realized. For ordering information, please refer to the Ordering
Guide.
With high bandwidth, low distortion and fast settling time the
AD8047 and AD8048 make high performance A/D drivers for
advanced converters. Figure 60 is an example of an AD8047
used as an input driver for an AD872, a 12-bit, 10 MSPS A/D
converter.
The layout of the evaluation board can be used as shown or
serve as a guide for a board layout.
Layout Considerations
The specified high speed performance of the AD8047 and
AD8048 requires careful attention to board layout and compo-
nent selection. Proper RF design techniques and low pass para-
sitic component selection are mandatory
+5V DIGITAL
+5V ANALOG
10Ω
7
DVDD
0.1µF
6
+5V DIGITAL
DGND
4
AVDD
22
0.1µF
+5V ANALOG
DRVDD
5
0.1µF
AGND
23
DRGND
CLOCK INPUT
10µF
21
CLK
20
AD872
49.9Ω
OTR
0.1µF
1
19
18
7
2
3
MSB
BIT2
BIT3
BIT4
BIT5
BIT6
BIT7
BIT8
BIT9
BIT10
BIT11
BIT12
1
ANALOG IN
VINA
6
AD8047
17
16
15
14
13
12
11
10
0.1µF
10µF
5
4
2
DIGITAL OUTPUT
VINB
27
REF GND
–5V
ANALOG
0.1µF
1µF
9
8
28
26
REF IN
24
AGND
REF OUT
AVSS
3
AVSS
25
0.1µF
0.1µF
–5V ANALOG
Figure 60. AD8047 Used as Driver for an AD872, a 12-Bit, 10 MSPS A/D Converter
–14–
REV. 0
AD8047/AD8048
RF
+VS
+VS
RG
C1
C3
C5
RO
1000pF
0.1µF
10µF
OPTIONAL
OUT
IN
C2
C4
C6
1000pF
0.1µF
10µF
RT
–VS
–VS
Supply Bypassing
Noninverting Configuration
Figure 61. Noninverting Configurations for Evaluation Boards
Table I.
AD8047
AD8048
Component
–1
+1
+2
+10
+101
–1
+2
+10
+101
RF
RG
RO
RS
200 Ω
200 Ω
49.9 Ω
–
66.5 Ω
–
49.9 Ω
0 Ω
1 kΩ
1 kΩ
49.9 Ω
0 Ω
1 kΩ
1 kΩ
10 Ω
49.9 Ω
0 Ω
200 Ω
200 Ω
49.9 Ω
–
200 Ω
200 Ω
49.9 Ω
0 Ω
1 kΩ
1 kΩ
10 Ω
49.9 Ω
0 Ω
110 Ω
49.9 Ω
0 Ω
110 Ω
49.9 Ω
0 Ω
RT
66.5 Ω
49.9 Ω
49.9 Ω
49.9 Ω
49.9 Ω
66.5 Ω
49.9 Ω
49.9 Ω
49.9 Ω
Small Signal
BW (–3 dB)
90 MHz 260 MHz 95 MHz 10 MHz 1 MHz
250 MHz 250 MHz 22 MHz 2 MHz
SOIC (R)
SOIC (R)
NONINVERTER
INVERTER
Figure 62. Evaluation Board Silkscreen (Top)
SOIC (R)
SOIC (R)
INVERTER
NONINVERTER
Figure 63. Board Layout (Solder Side)
–15–
REV. 0
AD8047/AD8048
SOIC (R)
SOIC (R)
INVERTER
NONINVERTER
Figure 64. Board Layout (Component Side)
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Pin Plastic DIP
(N Package)
8
5
0.280 (7.11)
0.240 (6.10)
PIN 1
1
4
0.325 (8.25)
0.300 (7.62)
0.430 (10.92)
0.348 (8.84)
0.060 (1.52)
0.015 (0.38)
0.195 (4.95)
0.115 (2.93)
0.210
(5.33)
MAX
0.130
(3.30)
MIN
0.015 (0.381)
0.008 (0.204)
0.160 (4.06)
0.115 (2.93)
SEATING
PLANE
0.100
(2.54)
0.022 (0.558)
0.014 (0.356)
0.070 (1.77)
0.045 (1.15)
BSC
8-Pin Plastic SOIC
(R Package)
0.150 (3.81)
8
5
4
0.244 (6.20)
0.157 (3.99)
0.150 (3.81)
0.228 (5.79)
PIN 1
1
0.020 (0.051) x 45
CHAMF
°
0.190 (4.82)
0.197 (5.01)
0.189 (4.80)
0.170 (4.32)
8
0
°
°
0.090
(2.29)
0.102 (2.59)
0.094 (2.39)
0.010 (0.25)
0.004 (0.10)
10
°
0
°
0.050
(1.27)
BSC
0.019 (0.48)
0.014 (0.36)
0.030 (0.76)
0.018 (0.46)
0.098 (0.2482)
0.075 (0.1905)
–16–
REV. 0
相关型号：
AD8047ARZ-REEL
IC OP-AMP, 4000 uV OFFSET-MAX, PDSO8, ROHS COMPLIANT, PLASTIC, SOIC-8, Operational Amplifier
ADI
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