Low Cost, 300 MHz
Voltage Feedback Amplifiers
AD8055/AD8056
Rev. J
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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
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2006 Analog Devices, Inc. All rights reserved.
FEATURES CONNECTION DIAGRAMS
NC
1
–IN
2
+IN
3
–
V
S4
NC
8
+V
S
7
V
OUT
6
NC
5
NC = NO CONNECT
AD8055
01063-001
Low cost single (AD8055) and dual (AD8056)
V
OUT 1
+IN
3
–V
S2
+V
S
5
–IN
4
AD8055
01063-002
Easy-to-use voltage feedback architecture
High speed
300 MHz, −3 dB bandwidth (G = +1)
1400 V/μs slew rate
20 ns settling to 0.1%
Low distortion: −72 dBc @ 10 MHz Figure 1. N-8 and R-8 Figure 2. RJ-5
Low noise: 6 nV/√Hz
OUT1
1
–IN1
2
+IN1
3
–V
S4
+V
S
8
OUT
7
–IN2
6
+IN2
5
AD8056
01063-003
, 1.2 μA max I
Low dc errors: 5 mV max VOS B
Small packaging
AD8055 available in 5-lead SOT-23
AD8056 available in 8-lead MSOP
Excellent video specifications (RL = 150 Ω, G = +2)
Figure 3. N-8, R-8, and RM-8
Gain flatness 0.1 dB to 40 MHz
0.01% differential gain error Their 0.1 dB flatness out to 40 MHz, wide bandwidth out to
300 MHz, along with 1400 V/µs slew rate and 20 ns settling
time, make them useful for a variety of high speed applications.
0.02° differential phase error
Drives 4 video loads (37.5 V) with 0.02% differential
Gain and 0.1° differential phase
The AD8055 and AD8056 require only 5 mA typ/amplifier of
supply current and operate on a dual ±5 V or a single +12 V
power supply, while capable of delivering over 60 mA of load
current. The AD8055 is available in a small 8-lead PDIP, an 8-lead
SOIC, and a 5-lead SOT-23, while the AD8056 is available in an
8-lead MSOP. These features make the AD8055/AD8056 ideal
for portable and battery-powered applications where size and
power are critical. These amplifiers in the R-8, N-8, and RM-8
packages are available in the extended temperature range of
−40°C to +125°C.
Low power, ±5 V supplies 5 mA typ/amplifier power
supply current
High output drive current: over 60 mA
APPLICATIONS
Imaging
Photodiode preamps
Video line drivers
Differential line drivers
Professional cameras
FREQUENCY (Hz)
GAIN (dB)
5
4
–5
3
2
1
0
–1
–2
–3
–4
VIN
RC
50Ω
RGRFRL
VOUT
VOUT = 100mV p-p
RL= 100Ω
G=+2
RF=402Ω
G=+1
RF=0Ω
RC=100Ω
G=+10
RF=909Ω
G=+5
RF= 1000Ω
1G100M10M1M0.3M
01063-004
Video switchers
Special effects
A-to-D drivers
Active filters
GENERAL DESCRIPTION
The AD8055 (single) and AD8056 (dual) voltage feedback
amplifiers offer bandwidth and slew rate typically found in
current feedback amplifiers. Additionally, these amplifiers are
easy to use and available at a very low cost.
Despite their low cost, the AD8055 and AD8056 provide
excellent overall performance. For video applications, their
differential gain and phase error are 0.01% and 0.02° into a
150 load and 0.02% and 0.1° while driving four video loads
(37.50 ).
Figure 4. Frequency Response
AD8055/AD8056
Rev. J | Page 2 of 16
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description......................................................................... 1
Connection Diagrams...................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
Maximum Power Dissipation ..................................................... 5
ESD Caution.................................................................................. 5
Typical Performance Characteristics ............................................. 6
Test Circuits ..................................................................................... 11
Applications..................................................................................... 12
Four-Line Video Driver............................................................. 12
Single-Ended-to-Differential Line Driver............................... 12
Low Noise, Low Power Preamp................................................ 12
Power Dissipation Limits .......................................................... 13
Resistor Selection ....................................................................... 13
Driving Capacitive Loads.......................................................... 13
Outline Dimensions....................................................................... 14
Ordering Guide .......................................................................... 16
REVISION HISTORY
2/06—Rev. I to Rev. J
Changes to Format .............................................................Universal
Updated Outline Dimensions....................................................... 15
Changes to Ordering Guide .......................................................... 16
2/04—Rev. H to Rev. I
Changes to Features.......................................................................... 1
Changes to Ordering Guide ............................................................ 3
6/03—Rev. G to Rev. H
Changes to Absolute Maximum Ratings....................................... 3
Updated Ordering Guide................................................................. 3
Updated Outline Dimensions....................................................... 11
2/03—Rev. F to Rev. G
Changes to Product Description .................................................... 1
Changes to Specifications................................................................ 2
Change to Ordering Guide.............................................................. 3
Outline Dimensions Updated ....................................................... 11
10/02—Rev. E to Rev. F
Text Changes to Reflect Extended Temperature Range for
R-8, N-8 Packages..............................................................................1
Changes to Specifications.................................................................2
Changes to Absolute Maximum Ratings........................................3
Figure 2 Replaced ..............................................................................3
Changes to Ordering Guide.............................................................3
Outline Dimensions Updated....................................................... 11
7/01—Rev. D to Rev. E
TPC 24 Replaced with New Graph.................................................7
3/01—Rev. C to Rev. D
Edit to Curve in TPC 23 ...................................................................7
2/01—Rev. B to Rev. C
Edits to Text at Top of Specifications Page (65 to 5)....................2
AD8055/AD8056
Rev. J | Page 3 of 16
SPECIFICATIONS
TA = 25°C, VS = ±5 V, RF = 402 , RL = 100 , Gain = +2, unless otherwise noted.
Table 1.
AD8055A/AD8056A
Parameter Conditions Min Typ Max Unit
DYNAMIC PERFORMANCE
−3 dB Bandwidth G = +1, VO = 0.1 V p-p 220 300 MHz
G=+1, VO = 2 V p-p 125 150 MHz
G=+2, VO = 0.1 V p-p 120 160 MHz
G=+2, VO = 2 V p-p 125 150 MHz
Bandwidth for 0.1 dB Flatness VO = 100 mV p-p 25 40 MHz
Slew Rate G = +1, VO = 4 V step 1000 1400 V/μs
G = +2, VO = 4 V step 750 840 V/μs
Settling Time to 0.1% G = +2, VO = 2 V step 20 ns
Rise and Fall Time, 10% to 90% G = +1, VO = 0.5 V step 2 ns
G = +1, VO = 4 V step 2.7 ns
G = +2, VO = 0.5 V step 2.8 ns
G = +2, VO = 4 V step 4 ns
NOISE/HARMONIC PERFORMANCE
Total Harmonic Distortion fC = 10 MHz, VO = 2 V p-p, RL = 1 kΩ −72 dBc
f
C = 20 MHz, VO = 2 V p-p, RL = 1 kΩ −57 dBc
Crosstalk, Output-to-Output (AD8056) f = 5 MHz, G = +2 −60 dB
Input Voltage Noise f = 100 kHz 6 nV/√Hz
Input Current Noise f = 100 kHz 1 pA/√Hz
Differential Gain Error NTSC, G = +2, RL = 150 Ω 0.01 %
NTSC, G = +2, RL = 37.5 Ω 0.02 %
Differential Phase Error NTSC, G = +2, RL = 150 Ω 0.02 Degree
NTSC, G = +2, RL = 37.5 Ω 0.1 Degree
DC PERFORMANCE
Input Offset Voltage 3 5 mV
T
MIN to TMAX 10 mV
Offset Drift 6 μV/°C
Input Bias Current 0.4 1.2 μA
T
MIN to TMAX 1 μA
Open-Loop Gain VO = ±2.5 V 66 71 dB
T
MIN to TMAX 64 dB
INPUT CHARACTERISTICS
Input Resistance 10 MΩ
Input Capacitance 2 pF
Input Common-Mode Voltage Range 3.2 ±V
Common-Mode Rejection Ratio VCM = ±2.5 V 82 dB
OUTPUT CHARACTERISTICS
Output Voltage Swing RL = 150 Ω 2.9 3.1 ±V
Output Current1 VO = ±2.0 V 55 60 mA
Short-Circuit Current1 110 mA
AD8055/AD8056
Rev. J | Page 4 of 16
AD8055A/AD8056A
Parameter Conditions Min Typ Max Unit
POWER SUPPLY
Operating Range ±4.0 ±5.0 ±6.0 V
Quiescent Current AD8055 5.4 6.5 mA
T
MIN to 125°C 7.6 mA
T
MIN to 85°C 7.3 mA
AD8056 10 12 mA
T
MIN to 125°C 13.9 mA
T
MIN to 85°C 13.3 mA
Power Supply Rejection Ratio +VS = +5 V to +6 V, −VS = −5 V 66 72 dB
−VS = –5 V to −6 V, +VS = +5 V 69 86 dB
OPERATING TEMPERATURE RANGE AD8055ART −40 +85 °C
AD8055AR, AD8055AN, AD8056AR, AD8056AN, AD8056ARM −40 +125 °C
1 Output current is limited by the maximum power dissipation in the package. See Figure 5.
AD8055/AD8056
Rev. J | Page 5 of 16
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Ratings
MAXIMUM POWER DISSIPATION
The maximum power that can be safely dissipated by the
AD8055/AD8056 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 can 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.
Supply Voltage 13.2 V
Input Voltage (Common Mode) ±VS
Differential Input Voltage ±2.5 V
Output Short-Circuit Duration Observe Power
Derating Curves
Storage Temperature Range N, R −65°C to +150°C
Operating Temperature Range (A Grade) −40°C to +125°C
Lead Temperature (Soldering 10 sec) 300°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.
While the AD8055/AD8056 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.
0.5 SOT-23-5
0
1.0
1.5
2.0
2.5
MSOP-8
SOIC-8
PDIP-8
MAXIMUM POWER DISSIPATION (W)
–55 –45 –35 –25 –15 –5 5 15 25 35 45 55 65 75 85 95 105 115 125
AMBIENT TEMPERATURE (°C)
01063-005
Figure 5. Plot of Maximum Power Dissipation vs.
Temperature for AD8055/AD8056
ESD 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 this product 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.
AD8055/AD8056
Rev. J | Page 6 of 16
TYPICAL PERFORMANCE CHARACTERISTICS
0V
1V 5ns
01063-011
0V
20mV 5ns
01063-007
Figure 34
Figure 6. Small Step Response, G = +1 (See )
Figure 35
Figure 9. Large Step Response, G = −1 (See )
5ns1V
0V
01063-008
FREQUENCY (Hz)
GAIN (dB)
5
4
–5
3
2
1
0
–1
–2
–3
–4
V
IN
R
C
50Ω
R
G
R
F
R
L
V
OUT
V
OUT
= 100mV p-p
R
L
= 100Ω
G=+2
R
F
=402Ω
G=+1
R
F
=0Ω
R
C
=100Ω
G=+10
R
F
=909Ω
G=+5
R
F
= 1000Ω
1G100M10M1M0.3M
01063-012
Figure 7. Large Step Response, G = +1 (See Figure 34)
Figure 10. Small Signal Frequency Response, G = +1, G = +2, G = +5, G = +10
5ns20mV
0V
01063-010
FREQUENCY (Hz)
GAIN (dB)
5
4
–5
3
2
1
0
–1
–2
–3
–4
1G100M10M1M0.3M
V
OUT
=2Vp-p
R
L
= 100Ω
G=+1
R
F
=0Ω
G=+2
R
F
=402Ω
G=+10
R
F
=909Ω
G=+5
R
F
= 1000Ω
01063-013
Figure 8. Small Step Response, G = −1 (See Figure 35)
Figure 11. Large Signal Frequency Response, G = +1, G = +2, G = +5, G = +10
AD8055/AD8056
Rev. J | Page 7 of 16
–50
–90
–60
–70
–80
DISTORTION (dBc)
–
40
V
OUT
(V p-p)
THIRD
SECOND
G=+2
R
L
=1kΩ
0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0
01063-017
FREQUENCY (Hz)
0.5
0.4
–0.5
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
OUTPUT (dB)
V
OUT
= 100mV
G=+2
R
L
=100Ω
R
F
=402Ω
1G100M10M1M0.3M
01063-014
Figure 12. 0.1 dB Flatness
Figure 15. Distortion vs. VOUT @ 20 MHz
FREQUENCY (Hz)
–
50
–100
–60
–70
–80
–90
HARMONIC DISTORTION (dBc)
10k 100k 1M 100M10M
V
OUT
=2Vp-p
G=+2
R
L
= 100Ω
THIRD
SECOND
0
1063-015
10
4
0
9
5
3
1
7
6
2
8
RISE TIME AND FALL TIME (ns)
V
IN
(V p-p)
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
RISE TIME
FALL TIME
G=+1
R
L
= 100Ω
R
F
=0Ω
01063-018
Figure 13. Harmonic Distortion vs. Frequency
Figure 16. Rise Time and Fall Time vs. VIN
10
4
0
9
5
3
1
7
6
2
8
RISE TIME AND FALL TIME (ns)
V
IN
(V p-p)
G=+1
R
L
=1kΩ
R
F
=0Ω
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
FALL TIME
RISE TIME
0
1063-019
FREQUENCY (Hz)
–
50
–100
–60
–70
–80
–90
HARMONIC DISTORTION (dBc)
THIRD
SECOND
V
OUT
=2Vp-p
G=+2
R
L
=1kΩ
10k 100k 1M 100M10M
0
1063-016
Figure 17. Rise Time and Fall Time vs. VIN
Figure 14. Harmonic Distortion vs. Frequency
AD8055/AD8056
Rev. J | Page 8 of 16
TIME (ns)
–0.5
–0.4
ERROR (%)
–0.3
–0.2
–0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
V
OUT
=0VTO+2V OR
V
OUT
=0VTO–2V
G=+2
R
L
=100Ω
0 102030405060
01063-020
FREQUENCY (MHz)
0
–90
–10
–20
–30
–40
–50
–60
–70
–80
10
PSRR (dB)
+PSRR
–PSRR
G=+2
R
F
=402Ω
0.1 1 10 100 500
0
1063-023
Figure 18. Settling Time
Figure 21. PSRR vs. Frequency
1V 50ns
V
IN
V
OUT
G=+1
R
L
= 100Ω
V
S
=±5V
01063-024
10
4
0
9
5
3
1
7
6
2
8
RISE TIME AND FALL TIME (ns)
V
IN
(V p-p)
G=+2
R
L
=100Ω
R
F
=402Ω
FALL TIME
RISE TIME
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
01063-021
Figure 19. Rise Time and Fall Time vs. V Figure 22. Overload Recovery
IN
RISE TIME AND FALL TIME (ns)
5.0
2.0
0
4.5
2.5
1.5
0.5
3.5
3.0
1.0
4.0
G=+2
R
L
=1kΩ
R
F
=402Ω
FALL TIME
RISE TIME
V
IN
(V p-p)
0 0.2 0.4 0.6 0.8 1.61.0 1.2 1.4
0
1063-022
FREQUENCY (MHz)
–30
–120
–40
–50
–60
–70
–80
–90
–100
–110
–
20
CROSSTALK (dB)
SIDE 1 DRIVEN
SIDE 2 DRIVEN
0.1 1 10 100 200
V
IN
=0dBm
G=+2
R
L
=100Ω
R
F
=402Ω
0
1063-025
Figure 20. Rise Time and Fall Time vs. VIN
Figure 23. Crosstalk (Output-to-Output) vs. Frequency
AD8055/AD8056
Rev. J | Page 9 of 16
45
90
0
–45
–90
135
PHASE (Degrees)
FREQUENCY (Hz)
180
10k 100k 1M 10M 100M 500M
01063-029
FREQUENCY (MHz)
0
–90
–10
–20
–30
–40
–50
–60
–70
–80
–100
CMRR (dB)
0.1 1 10 100 500
402Ω
50Ω
402Ω
402Ω
58Ω402Ω
01063-026
Figure 24. CMRR vs. Frequency
Figure 27. Phase vs. Frequency
V
OUT
(2V/DIV)
V
IN
(1V/DIV)
G=+2
R
L
= 100Ω
R
F
= 402Ω
V
S
=±5V
50ns
01063-027
–0.04
–0.02
0
0.02
0.04
–0.04
DIFFERENTIAL GAIN (%)
–0.02
0
0.02
0.04
DIFFERENTIAL PHASE
(Degrees)
IRE
1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
IRE
1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
1 BACK TERMINATED LOAD (150Ω)
1 BACK TERMINATED LOAD (150Ω)
G=+2
R
F
= 402Ω
G=+2
R
F
= 402Ω
01063-030
Figure 25. Overload Recovery
Figure 28. Differential Gain and Differential Phase
FREQUENCY (MHz)
90
40
80
70
60
50
30
20
10
0
–10
OPEN-LOOP GAIN (dB)
0.01 0.1 1 10 100 500
R
L
=100Ω
01063-028
–0.04
DIFFERENTIAL GAIN (%)
–0.02
0
0.02
0.04
DIFFERENTIAL PHASE
(Degrees)
IRE
1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
IRE
1ST 2ND 3RD 4TH 5TH 6TH 7TH 8TH 9TH 10TH 11TH
G=+2
R
F
= 402Ω
–0.15
–0.10
0
0.05
0.15
0.10
–0.05
G=+2
R
F
= 402Ω
4 VIDEO LOADS (37.5Ω)
4 VIDEO LOADS (37.5Ω)
01063-031
Figure 29. Differential Gain and Differential Phase
Figure 26. Open-Loop Gain vs. Frequency
AD8055/AD8056
Rev. J | Page 10 of 16
FREQUENCY (Hz)
CURRENT NOISE (pA/ Hz)
100
10
0.1
1
10 100 1k 10k 100k 1M 10M 50M
01063-034
4.5
2.5
3.5
3.0
5.0
4.0
2.0
1.5
1.0
0.5
0
TEMPERATURE (°C)
–55 –35 –15 5 25 45 65 85 105 125
±
V
OUT
(V)
V
S
=±5V
R
L
=1kΩ
R
L
=50Ω
R
L
=150Ω
0
1063-032
Figure 30. Output Swing vs. Temperature
Figure 32. Current Noise vs. Frequency
FREQUENCY (Hz)
VOLTAGE NOISE (nV/ Hz)
1000
100
1
10
10 100 1k 10k 100k 1M 10M 50M
6nV/ Hz
01063-033
FREQUENCY (MHz)
40
20
10
0
30
5
15
25
35
45
–5
G=+2
R
F
=402Ω
|Z
OUT
| (Ω)
0.01 0.1 1 10 100 500
01063-035
Figure 31. Voltage Noise vs. Frequency
Figure 33. Output Impedance vs. Frequency
AD8055/AD8056
Rev. J | Page 11 of 16
TEST CIRCUITS
AD8055
V
OUT
4.7µF
0.01µF
0.001µF
6
7
3
2
4
100Ω
HP8130A
PULSE
GENERATOR
T
R
/T
F
=0.67ns
4.7µF
0.01µF
0.001µF
+V
S
V
IN
57Ω
402Ω
402Ω
–V
S
01063-009
AD8055
VOUT
4.7µF
0.01µF
0.001µF
6
7
2
3
4100Ω
HP8130A
PULSE
GENERATOR
TR/TF=1ns
4.7µF
0.01µF
0.001µF
+VS
VIN
50Ω
100Ω
–VS
01063-006
Figure 35. G = −1, R = 100 Ω
Figure 34. G = +1, R = 100 Ω L
L
AD8055/AD8056
Rev. J | Page 12 of 16
APPLICATIONS
FOUR-LINE VIDEO DRIVER Between these points, a feedback resistor can be used to close
the loop. As in the case of a conventional op amp inverting gain
stage, an input resistor is added to vary the gain.
The AD8055 is a useful low cost circuit for driving up to four
video lines. For such an application, the amplifier is configured
for a noninverting gain of 2, as shown in Figure 36. The input
video source is terminated in 75 Ω and is applied to the high
impedance noninverting input.
/R
The gain of this circuit from the input to AMP1 output is RF I,
while the gain to the output of AMP2 is −R /R
F I. The circuit
therefore creates a balanced differential output signal from a
single-ended input. The advantage of this circuit is that the gain
can be changed by changing a single resistor, while still
maintaining the balanced differential outputs.
Each output cable is connected to the op amp output via a 75 Ω
series back termination resistor for proper cable termination.
The terminating resistors at the other ends of the lines divide
the output signal by 2, which is compensated for by the gain of 2
of the op amp stage.
75Ω
+5V
–5V
AD8056
402Ω
402Ω
402Ω
402Ω
49.9Ω
49.9Ω
1
2
3
8
AMP1
5
6
7
4
AMP2
0.1µF
R
F
402Ω
R
I
402Ω
10µF
0.1µF 10µF
V
IN
+V
OUT
–V
OUT
01063-037
For a single load, the differential gain error of this circuit was
measured as 0.01%, with a differential phase error of 0.02°. The
two load measurements were 0.02% and 0.03°, respectively. For
four loads, the differential gain error is 0.02%, while the
differential phase increases to 0.1°.
V
OUT3
AD8055
+5V
–5V
6
7
2
34
75Ω
75Ω
75Ω
75Ω
75Ω
75Ω
75Ω
75Ω
V
OUT1
V
OUT2
V
OUT4
0.1µF
0.1µF 10µF
10µF
75Ω
402Ω
402Ω
V
IN
01063-036
Figure 37. Single-Ended-to-Differential Line Driver
Figure 36. Four-Line Video Driver LOW NOISE, LOW POWER PREAMP
SINGLE-ENDED-TO-DIFFERENTIAL LINE DRIVER The AD8055 makes a good, low cost, low noise, low power
preamp. A gain-of-10 preamp can be made with a feedback
resistor of 909 Ω and a gain resistor of 100 Ω, as shown in
Creating differential signals from single-ended signals is
required for driving balanced, twisted pair cables, differential
input ADCs, and other applications that require differential
signals. This can be accomplished by using an inverting and a
noninverting amplifier stage to create the complementary
signals.
Figure 38. The circuit has a −3 dB bandwidth of 20 MHz.
0.1µF 10µF
0.1µF 10µF
+5V
–5V
+
AD8055
6
7
2
34
V
OUT
R
S
909Ω
100Ω
0
1063-038
The circuit shown in Figure 37 shows how an AD8056 can be
used to make a single-ended-to-differential converter that offers
some advantages over the architecture previously mentioned.
Each op amp is configured for unity gain by the feedback
resistors from the outputs to the inverting inputs. In addition,
each output drives the opposite op amp with a gain of −1 by
means of the crossed resistors. The result of this is that the
outputs are complementary and there is high gain in the overall
configuration.
Figure 38. Low Noise, Low Power Preamp with G = +10 and BW = 20 MHz
With a low source resistance (< approximately 100 Ω), the
major contributors to the input-referred noise of this circuit are
the input voltage noise of the amplifier and the noise of the
100 resistor. These are 6 nV/√Hz and 1.2 nV/√Hz, respectively.
These values yield a total input referred noise of 6.1 nV/√Hz.
Feedback techniques similar to a conventional op amp are used
to control the gain of the circuit. From the noninverting input
of AMP1 to the output of AMP2 is an inverting gain.
AD8055/AD8056
Rev. J | Page 13 of 16
FREQUENCY (MHz)
5
4
–5
1
–2
–3
–4
3
2
–1
0
NORMALIZED GAIN (dB)
0.3 1 10 100 500
C
L
402Ω
100Ω
402Ω
50Ω
V
IN
=0dBm
C
L
=0pF
C
L
= 10pF
C
L
= 20pF
C
L
=30pF
01063-039
POWER DISSIPATION LIMITS
With a 10 V supply (total VCC − VEE), the quiescent power
dissipation of the AD8055 in the SOT-23-5 package is 65 mW,
while the quiescent power dissipation of the AD8056 in the
MSOP-8 is 120 mW. This translates into a 15.6°C rise above the
ambient for the SOT-23-5 package and a 24°C rise for the
MSOP-8 package.
The power dissipated under heavy load conditions is
approximately equal to the supply voltage minus the output
voltage, times the load current, plus the quiescent power
previously computed. The total power dissipation is then
multiplied by the thermal resistance of the package to find the
temperature rise, above ambient, of the part. The junction
temperature should be kept below 150°C.
Figure 39. Capacitive Load Drive
In general, to minimize peaking or to ensure the stability for
larger values of capacitive loads, a small series resistor, R
The AD8055 in the SOT-23-5 package can dissipate 270 mW,
while the AD8056 in the MSOP-8 package can dissipate
325 mW (at 85°C ambient) without exceeding the maximum
die temperature. In the case of the AD8056, this is greater than
1.5 V rms into 50 Ω, enough to accommodate a 4 V p-p sine
wave signal on both outputs simultaneously. However, because
each output of the AD8055 or AD8056 is capable of supplying
as much as 110 mA into a short circuit, a continuous short-
circuit condition will exceed the maximum safe junction
temperature.
S, can
be added between the op amp output and the capacitor, CL. For
the setup depicted in Figure 40, the relationship between RS and
C
RESISTOR SELECTION
Table 3 is a guide for resistor selection for maintaining gain
flatness vs. frequency for various values of gain.
Table 3.
Gain RF (Ω) RG (Ω) −3 dB Bandwidth (MHz)
+1 0 300
+2 402 402 160
+5 1 k 249 45
+10 909 100 20
DRIVING CAPACITIVE LOADS
When driving a capacitive load, most op amps exhibit peaking
in the frequency response just before the frequency rolls off.
Figure 39 shows the responses for an AD8056 running at a gain
of +2, with an 100 Ω load that is shunted by various values of
capacitance. It can be seen that under these conditions the part
is still stable with capacitive loads of up to 30 pF.
L was empirically derived and is shown in Figure 41. RS was
chosen to produce less than 1 dB of peaking in the frequency
response. Note also that after a sharp rise, RS quickly settles to
approximately 25 Ω.
50Ω
AD8055
+5V
–5V
402Ω
402Ω
6
7
2
34
FET PROBE
V
IN
=0dBm
V
OUT
R
S
C
L
0.1µF 10µF
0.1µF 10µF
01063-040
Figure 40. Setup for R vs. C
S L
40
0
35
20
15
10
5
30
25
C
L
(pF)
R
S
(Ω)
0 102030405060270
01063-041
Figure 41. R vs. C
S L
AD8055/AD8056
Rev. J | Page 14 of 16
OUTLINE DIMENSIONS
COMPLIANT TO JEDEC STANDARDS MS-001-BA
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
SEATING
PLANE
0.015
(0.38)
MIN
0.210
(5.33)
MAX
PIN 1
0.150 (3.81)
0.130 (3.30)
0.115 (2.92)
0.070 (1.78)
0.060 (1.52)
0.045 (1.14)
8
14
5
0.280 (7.11)
0.250 (6.35)
0.240 (6.10)
0.100 (2.54)
BSC
0.400 (10.16)
0.365 (9.27)
0.355 (9.02)
0.060 (1.52)
MAX
0.430 (10.92)
MAX
0.014 (0.36)
0.010 (0.25)
0.008 (0.20)
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.195 (4.95)
0.130 (3.30)
0.115 (2.92)
0.015 (0.38)
GAUGE
PLANE
0.005 (0.13)
MIN
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.
CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 42. 8-Lead Plastic Dual In-Line Package [PDIP]
Narrow Body (N-8)
Dimensions shown in inches and (millimeters)
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099) × 45°
8°
0°
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
41
85
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500)
BSC
6.20 (0.2440)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
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.
COMPLIANT TO JEDEC STANDARDS MS-012-AA
Figure 43. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body (R-8)
Dimensions shown in millimeters and (inches)
AD8055/AD8056
Rev. J | Page 15 of 16
COMPLIANT TO JEDEC STANDARDS MO-187-AA
0.80
0.60
0.40
8°
0°
4
8
1
5
PIN 1
0.65 BSC
SEATING
PLANE
0.38
0.22
1.10 MAX
3.20
3.00
2.80
COPLANARITY
0.10
0.23
0.08
3.20
3.00
2.80
5.15
4.90
4.65
0.15
0.00
0.95
0.85
0.75
Figure 44. 8-Lead Mini Small Outline Package [MSOP]
(RM-8)
Dimensions shown in millimeters
PIN 1
1.60 BSC 2.80 BSC
1.90
BSC
0.95 BSC
5
123
4
0.22
0.08
10°
5°
0°
0.50
0.30
0.15 MAX SEATING
PLANE
1.45 MAX
1.30
1.15
0.90
2.90 BSC
0.60
0.45
0.30
COMPLIANT TO JEDEC STANDARDS MO-178-AA
Figure 45. 5-Lead Small Outline Transistor Package [SOT-23]
(RJ-5)
Dimensions shown in millimeters
AD8055/AD8056
Rev. J | Page 16 of 16
ORDERING GUIDE
Model Temperature Range Package Description Package Option Branding
AD8055AN −40°C to +125°C 8-Lead PDIP N-8
AD8055ANZ1−40°C to +125°C 8-Lead PDIP N-8
AD8055AR −40°C to +125°C 8-Lead SOIC_N R-8
AD8055AR-REEL −40°C to +125°C 8-Lead SOIC_N, 13" Tape and Reel R-8
AD8055AR-REEL7 −40°C to +125°C 8-Lead SOIC_N, 7" Tape and Reel R-8
AD8055ARZ1−40°C to +125°C 8-Lead SOIC_N R-8
AD8055ARZ-REEL1−40°C to +125°C 8-Lead SOIC_N, 13" Tape and Reel R-8
AD8055ARZ-REEL71−40°C to +125°C 8-Lead SOIC_N, 7" Tape and Reel R-8
AD8055ART-R2 −40°C to +85°C 5-Lead SOT-23, Reel RJ-5 H3A
AD8055ART-REEL −40°C to +85°C 5-Lead SOT-23, 13" Tape and Reel RJ-5 H3A
AD8055ART-REEL7 −40°C to +85°C 5-Lead SOT-23, 7" Tape and Reel RJ-5 H3A
AD8055ARTZ-R21−40°C to +85°C 5-Lead SOT-23, Reel RJ-5 H3A
AD8055ARTZ-REEL71−40°C to +85°C 5-Lead SOT-23, 7" Tape and Reel RJ-5 H072
AD8056AN −40°C to +125°C 8-Lead PDIP N-8
AD8056ANZ1−40°C to +125°C 8-Lead PDIP N-8
AD8056AR −40°C to +125°C 8-Lead SOIC_N R-8
AD8056AR-REEL −40°C to +125°C 8-Lead SOIC_N, 13" Tape and Reel R-8
AD8056AR-REEL7 −40°C to +125°C 8-Lead SOIC_N, 7" Tape and Reel R-8
AD8056ARZ1−40°C to +125°C 8-Lead SOIC_N R-8
AD8056ARZ-REEL1−40°C to +125°C 8-Lead SOIC_N, 13" Tape and Reel R-8
AD8056ARZ-REEL71−40°C to +125°C 8-Lead SOIC_N, 7" Tape and Reel R-8
AD8056ARM −40°C to +125°C 8-Lead MSOP RM-8 H5A
AD8056ARM-REEL −40°C to +125°C 8-Lead MSOP, 13" Tape and Reel RM-8 H5A
AD8056ARM-REEL7 −40°C to +125°C 8-Lead MSOP, 7" Tape and Reel RM-8 H5A
AD8056ARMZ1−40°C to +125°C 8-Lead MSOP RM-8 H5A#
AD8056ARMZ-REEL1−40°C to +125°C 8-Lead MSOP, 13" Tape and Reel RM-8 H5A#
AD8056ARMZ-REEL71−40°C to +125°C 8-Lead MSOP, 7" Tape and Reel RM-8 H5A#
1 Z = Pb-free part, # denotes lead-free product may be top or bottom marked.
2 Prior to 0542, parts were branded H3A.
©2006 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
C01063-0-2/06(J)
