AD8138 Analog Devices Low-Distortion Differential ADC Driver User Guide (Volume 1)

Low Distortion Differential ADC Driver AD8138

FEATURES PIN CONFIGURATION Easy to Use Single-Ended-to-Differential Conversion Adjustable Output Common-Mode Voltage

–IN +IN

Externally Adjustable Gain

NCVOCM

Low Harmonic Distortion –94 d Bc—Second, –114 d Bc—Third @ 5 MHz into V+ V–

+OUT –OUT

–87 d Bc—Second, –85 d Bc—Third @ 20 MHz into

AD8138

NC = NO CONNECT

–3 d B Bandwidth of 320 MHz, G = +1 Fast Settling to 0.01% of 16 ns

Slew Rate 1150 V/s TYPICAL APPLICATION CIRCUIT

Fast Overdrive Recovery of 4 ns

Low Input Voltage Noise of 5 n V/÷Hz 1 m V Typical Offset Voltage Wide Supply Range +3 V to 5 V

VIN AVDD DVDD AIN

Low Power 90 m W on 5 V VOCM

DIGITAL

OUTPUTSAD8138

0.1 d B Gain Flatness to 40 MHz

AVSS VREF

Available in 8-Lead SOIC and MSOP Packages

APPLICATIONS ADC Driver Single-Ended-to-Differential Converter IF and Baseband Gain Block Differential Buffer Line Driver

PRODUCT DESCRIPTION The AD8138 eliminates the need for a transformer with high The AD8138 is a major advancement over op amps for differential performance ADCs, preserving the low frequency and dc infor- signal processing. The AD8138 can be used as a single-ended- mation. The common-mode level of the differential output is to-differential amplifier or as a differential-to-differential adjustable by a voltage on the VOCM pin, easily level-shifting the

amplifier. The AD8138 is as easy to use as an op amp, and input signals for driving single-supply ADCs. Fast overload greatly simplifies differential signal amplification and driving. recovery preserves sampling accuracy.

Manufactured on ADI’s proprietary XFCB bipolar process, the

The AD8138 distortion performance makes it an ideal ADC driver

AD8138 has a –3 d B bandwidth of 320 MHz and delivers a

for communication systems, with distortion performance good

differential signal with the lowest harmonic distortion available

enough to drive state-of-the-art 10-bit to 16-bit converters at

in a differential amplifier. The AD8138 has a unique internal

high frequencies. The AD8138’s high bandwidth and IP3 also

feedback feature that provides balanced output gain and phase

make it appropriate for use as a gain block in IF and baseband

matching, suppressing even order harmonics. The internal feed-

signal chains. The AD8138 offset and dynamic performance

back circuit also minimizes any gain error that would be associated

make it well suited for a wide variety of signal processing and

with the mismatches in the external gain setting resistors.

data acquisition applications.

The AD8138’s differential output helps balance the input-to-

The AD8138 is available in both SOIC and MSOP packages for

differential ADCs, maximizing the performance of the ADC.

operation over –40∞C to +85∞C temperatures.

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