Low Cost, High Speed
Differential Driver
AD8131
Rev. B
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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
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FEATURES
High speed
400 MHz, −3 dB full power bandwidth
2000 V/μs slew rate
Fixed gain of 2 with no external components
Internal common-mode feedback to improve gain and phase
balance: −60 dB @ 10 MHz
Separate input to set the common-mode output voltage
Low distortion: 68 dB SFDR @ 5 MHz 200 Ω load
Power supply range +2.7 V to ±5 V
APPLICATIONS
Video line driver
Digital line driver
Low power differential ADC driver
Differential in/out level shifting
Single-ended input to differential output driver
FUNCTIONAL BLOCK DIAGRAM
NC = NO CONNECT
AD8131
1
2
3
45
6
7
8
750Ω 750Ω
1.5kΩ 1.5kΩ
–D
IN
V
OCM
V+
+OUT
+D
IN
NC
V–
–OUT
01072-001
Figure 1.
GENERAL DESCRIPTION
The AD8131 is a differential or single-ended input to
differential output driver requiring no external components for
a fixed gain of 2. The AD8131 is a major advancement over op
amps for driving signals over long lines or for driving
differential input ADCs. The AD8131 has a unique internal
feedback feature that provides output gain and phase matching
that are balanced to −60 dB at 10 MHz, reducing radiated EMI
and suppressing harmonics. Manufactured on the Analog
Devices, Inc. next generation XFCB bipolar process, the
AD8131 has a −3 dB bandwidth of 400 MHz and delivers a
differential signal with very low harmonic distortion.
The AD8131 is a differential driver for the transmission of
high-speed signals over low-cost twisted pair or coax cables.
The AD8131 can be used for either analog or digital video
signals or for other high-speed data transmission. The AD8131
driver is capable of driving either Cat3 or Cat5 twisted pair or
coax with minimal line attenuation. The AD8131 has
considerable cost and performance improvements over discrete
line driver solutions.
The AD8131 can replace transformers in a variety of applications,
preserving low frequency and dc information. The AD8131 does
not have the susceptibility to magnetic interference and hysteresis
of transformers. It is smaller, easier to work with, and has the high
reliability associated with ICs.
20
–30
–40
–50
–60
–70
–80
1 10 100 1000
BALANCE ERROR (dB)
FREQUENCY (MHz)
ΔV
OUT, dm
= 2V p-p
ΔV
OUT, cm
/ΔV
OUT, dm
V
S
= +5V
V
S
= ±5V
01072-002
Figure 2. Output Balance Error vs. Frequency
The AD8131’s differential output also helps balance the input
for differential ADCs, optimizing the distortion performance of
the ADCs. The common-mode level of the differential output is
adjustable by a voltage on the V
OCM
pin, easily level-shifting the
input signals for driving single-supply ADCs with dual supply
signals. Fast overload recovery preserves sampling accuracy.
The AD8131 is available in both SOIC and MSOP packages for
operation over −40°C to +125°C.
