Low Distortion,
Differential ADC Driver
AD8138
Data Sheet
PIN CONFIGURATION
–IN 1
8
+IN
VOCM 2
7
NC
V+ 3
+OUT 4
6
AD8138
V–
5
–OUT
NC = NO CONNECT
Figure 1.
TYPICAL APPLICATION CIRCUIT
5V
5V
499Ω
VIN
499Ω
+
VOCM
499Ω
AIN
AIN
–
AVDD
DVDD
DIGITAL
OUTPUTS
ADC
AD8138
AVSS
VREF
01073-002
Easy to use, single-ended-to-differential conversion
Adjustable output common-mode voltage
Externally adjustable gain
Low harmonic distortion
−94 dBc SFDR at 5 MHz
−85 dBc SFDR at 20 MHz
−3 dB bandwidth of 320 MHz, G = +1
Fast settling to 0.01% of 16 ns
Slew rate 1150 V/µs
Fast overdrive recovery of 4 ns
Low input voltage noise of 5 nV/√Hz
1 mV typical offset voltage
Wide supply range +3 V to ±5 V
Low power 90 mW on 5 V
0.1 dB gain flatness to 40 MHz
Available in 8-Lead SOIC and MSOP packages
01073-001
FEATURES
499Ω
Figure 2.
APPLICATIONS
ADC drivers
Single-ended-to-differential converters
IF and baseband gain blocks
Differential buffers
Line drivers
GENERAL DESCRIPTION
The AD8138 is a major advancement over op amps for
differential signal processing. The AD8138 can be used as a
single-ended-to-differential amplifier or as a differential-todifferential amplifier. The AD8138 is as easy to use as an op
amp and greatly simplifies differential signal amplification and
driving. Manufactured on the proprietary ADI XFCB bipolar
process, the AD8138 has a −3 dB bandwidth of 320 MHz and
delivers a differential signal with the lowest harmonic distortion
available in a differential amplifier. The AD8138 has a unique
internal feedback feature that provides balanced output gain
and phase matching, suppressing even order harmonics. The
internal feedback circuit also minimizes any gain error that
would be associated with the mismatches in the external gain
setting resistors.
The differential output of the AD8138 helps balance the input
to differential ADCs, maximizing the performance of the ADC.
Rev. G
The AD8138 eliminates the need for a transformer with high
performance ADCs, preserving the low frequency and dc information. The common-mode level of the differential output is
adjustable by a voltage on the VOCM pin, easily level-shifting the
input signals for driving single-supply ADCs. Fast overload
recovery preserves sampling accuracy.
The AD8138 distortion performance makes it an ideal ADC
driver for communication systems, with distortion performance
good enough to drive state-of-the-art 10-bit to 16-bit converters
at high frequencies. The high bandwidth and IP3 of the
AD8138 also make it appropriate for use as a gain block in IF
and baseband signal chains. The AD8138 offset and dynamic
performance makes it well suited for a wide variety of signal
processing and data acquisition applications.
The AD8138 is available in both SOIC and MSOP packages for
operation over −40°C to +85°C temperatures.
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