Low Distortion, Differential Analog-to-Digital Converter Driver AD8138A FEATURES PIN CONFIGURATION Easy to use, single-ended-to-differential conversion IN 1 8 +IN V 2 7 NC Adjustable output common-mode voltage OCM V+ 3 6 V Externally adjustable gain +OUT 4 5 OUT AD8138A Low harmonic distortion 94 dBc SFDR 5 MHz NC = NO CONNECT 85 dBc SFDR 20 MHz Figure 1. 3 dB bandwidth of 300 MHz, G = +1 TYPICAL APPLICATION CIRCUIT Fast settling to 0.01% of 16 ns 5V 5V Slew rate: 1150 V/s 499 Fast overdrive recovery of 4 ns 499 AVDD DVDD V Low input voltage noise of 5 nV/Hz IN AIN V OCM DIGITAL 1 mV typical offset voltage AD8138A ADC OUTPUTS 499 AIN Wide supply range: +3 V to 5 V V AVSS REF Low power: 90 mW on 5 V 499 0.1 dB gain flatness to 30 MHz Available in 8-lead SOIC and MSOP packages Figure 2. APPLICATIONS ADC drivers Single-ended-to-differential converters IF and baseband gain blocks Differential buffers Line drivers GENERAL DESCRIPTION The AD8138A is a major advancement over op amps for The AD8138A eliminates the need for a transformer with high differential signal processing. The AD8138A can be used as performance ADCs, preserving the low frequency and dc infor- a single-ended-to-differential amplifier or as a differential-to- mation. The common-mode level of the differential output is differential amplifier. The AD8138A is as easy to use as an op adjustable by a voltage on the VOCM pin, easily level shifting the amp and greatly simplifies differential signal amplification and input signals for driving single-supply ADCs. Fast overload driving. recovery preserves sampling accuracy. Manufactured on the Analog Devices, Inc., proprietary XFCB The AD8138A distortion performance makes it an ideal ADC bipolar process, the AD8138A has a 3 dB bandwidth of 300 MHz driver for communication systems, with distortion performance and delivers a differential signal with low harmonic distortion. good enough to drive state-of-the-art 10-bit to 16-bit converters The AD8138A has a unique internal feedback feature that provides at high frequencies. The high bandwidth and IP3 of the AD8138A balanced output gain and phase matching, suppressing even- make it appropriate for use as a gain block in IF and baseband order harmonics. The internal feedback circuit minimizes any signal chains. The AD8138A offset and dynamic performance gain error that is associated with the mismatches in the external makes it well-suited for a wide variety of signal processing and gain setting resistors. data acquisition applications. The differential output of the AD8138A helps balance the input The AD8138A is available in both SOIC and MSOP packages for operation over the 40C to +85C temperature range. to differential analog-to-digital converters (ADCs), maximizing the performance of the ADC. Rev. 0 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 07834-001 07834-002AD8138A TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation ...................................................................... 17 Applications ....................................................................................... 1 Analyzing an Application Circuit ............................................ 17 Pin Configuration ............................................................................. 1 Setting the Closed-Loop Gain .................................................. 17 Typical Application Circuit ............................................................. 1 Estimating the Output Noise Voltage ...................................... 17 General Description ......................................................................... 1 The Impact of Mismatches in the Feedback Networks ......... 18 Revision History ............................................................................... 2 Calculating The Input Impedance of an Application Circuit .......................................................................................... 18 Specif icat ions ..................................................................................... 3 Input Common-Mode Voltage Range in Single-Supply IN to OUT Specifications ....................................................... 3 Applications ................................................................................ 18 VOCM to OUT Specifications ..................................................... 4 Setting the Output Common-Mode Voltage .......................... 18 IN to OUT Specifications ....................................................... 5 Driving a Capacitive Load ......................................................... 18 VOCM to OUT Specifications ..................................................... 6 Layout, Grounding, and Bypassing .............................................. 19 Absolute Maximum Ratings ............................................................ 7 Balanced Transformer Driver ....................................................... 20 Thermal Resistance ...................................................................... 7 High Performance ADC Driving ................................................. 21 ESD Caution .................................................................................. 7 3 V Operation ................................................................................. 22 Pin Configuration and Function Descriptions ............................. 8 Outline Dimensions ....................................................................... 23 Typical Performance Characteristics ............................................. 9 Ordering Guide .......................................................................... 23 Test Circuits ..................................................................................... 15 Terminology .................................................................................... 16 REVISION HISTORY 10/08Revision 0: Initial Version Rev. 0 Page 2 of 24