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AD8055 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD8055
Beschreibung Voltage Feedback Amplifiers
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 16 Seiten
AD8055 Datasheet, Funktion
FEATURES
Low cost single (AD8055) and dual (AD8056)
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
Low noise: 6 nV/√Hz
Low dc errors: 5 mV max VOS, 1.2 μA max IB
Small packaging
AD8055 available in 5-lead SOT-23
AD8056 available in 8-lead MSOP
Excellent video specifications (RL = 150 Ω, G = +2)
Gain flatness 0.1 dB to 40 MHz
0.01% differential gain error
0.02° differential phase error
Drives 4 video loads (37.5 V) with 0.02% differential
Gain and 0.1° differential phase
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
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 Ω load and 0.02% and 0.1° while driving four video loads
(37.50 Ω).
Rev. J
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
Low Cost, 300 MHz
Voltage Feedback Amplifiers
AD8055/AD8056
CONNECTION DIAGRAMS
NC 1
8 NC
–IN 2
+IN 3
–VS 4
AD8055
7 +VS
6 VOUT
5 NC
NC = NO CONNECT
Figure 1. N-8 and R-8
VOUT 1
–VS 2
+IN 3
AD8055
5 +VS
4 –IN
Figure 2. RJ-5
OUT1 1
–IN1 2
+IN1 3
–VS 4
AD8056
8 +VS
7 OUT
6 –IN2
5 +IN2
Figure 3. N-8, R-8, and RM-8
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.
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.
5
4 VIN
RC
3 50
2 RG RF
1
0
VOUT
RL
VROL U=T1=00100mV p-p
G = +1
RRFC
=
=
0
100
G = +2
RF = 402
–1
–2
–3
–4
–5
0.3M
G = +10
RF = 909
G = +5
RF = 1000
1M 10M 100M
FREQUENCY (Hz)
Figure 4. Frequency Response
1G
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.






AD8055 Datasheet, Funktion
AD8055/AD8056
TYPICAL PERFORMANCE CHARACTERISTICS
0V
20mV
5ns
Figure 6. Small Step Response, G = +1 (See Figure 34)
0V
1V 5ns
Figure 7. Large Step Response, G = +1 (See Figure 34)
0V
20mV
5ns
Figure 8. Small Step Response, G = −1 (See Figure 35)
0V
1V 5ns
Figure 9. Large Step Response, G = −1 (See Figure 35)
5
4 VIN
RC
3 50
2 RG RF
1
0
VOUT
RL
VROL U=T1=00100mV p-p
G = +1
RRFC
=
=
0
100
G = +2
RF = 402
–1
–2
–3
–4
–5
0.3M
G = +10
RF = 909
G = +5
RF = 1000
1M 10M 100M
FREQUENCY (Hz)
1G
Figure 10. Small Signal Frequency Response, G = +1, G = +2, G = +5, G = +10
5
4
3
2
1
0
–1
–2
–3
–4
–5
0.3M
RVOL U=T1=002V p-p
G = +1
RF = 0
G = +2
RF = 402
G = +10
RF = 909
G = +5
RF = 1000
1M 10M 100M
FREQUENCY (Hz)
1G
Figure 11. Large Signal Frequency Response, G = +1, G = +2, G = +5, G = +10
Rev. J | Page 6 of 16

6 Page









AD8055 pdf, datenblatt
AD8055/AD8056
APPLICATIONS
FOUR-LINE VIDEO DRIVER
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.
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.
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°.
+5V
402
75
75
VOUT1
402
2
0.1µF
7
AD8055 6
VIN 3 4
75
0.1µF
10µF
10µF
75
75
75
VOUT2
75
VOUT3
–5V 75
VOUT4
75
Figure 36. Four-Line Video Driver
SINGLE-ENDED-TO-DIFFERENTIAL LINE DRIVER
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.
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.
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.
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 gain of this circuit from the input to AMP1 output is RF/RI,
while the gain to the output of AMP2 is −RF /RI. 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.
RF
402
+5V
RI
402
VIN
8
3
AMP1
2
402
0.1µF
1
10µF
49.9
+VOUT
AD8056
402
402
402
75
6
AMP2
54
7
49.9
–VOUT
0.1µF 10µF
–5V
Figure 37. Single-Ended-to-Differential Line Driver
LOW NOISE, LOW POWER PREAMP
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
Figure 38. The circuit has a −3 dB bandwidth of 20 MHz.
909
+5V
100
RS
0.1µF
27
AD8055 6
34
0.1µF
+
10µF
10µF
VOUT
–5V
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 Ω 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.
Rev. J | Page 12 of 16

12 Page





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