Datasheet AD605 (Analog Devices)

Dual, Low Noise, Single-Supply Variable Gain Amplifier AD605 FEATURES FUNCTIONAL BLOCK DIAGRAM 2 independent linear-in-dB channels FIXED GAIN Input noise at maximum gain: 1.8 nV/√Hz, 2.7 pA/√Hz PRECISION PASSIVE VGN AMPLIFIER GAIN INPUT ATTENUATOR +34.4dB Bandwidth: 40 MHz (−3 dB) CONTROL OUT AND Differential input SCALING VREF Absolute gain range programmable FBK −14 dB to +34 dB (FBK shorted to OUT) through 0 dB to 48 dB (FBK open) VOCM Variable gain scaling: 20 dB/V through 40 dB/V +IN DIFFERENTIAL ATTENUATOR Stable gain with temperature and supply variations –IN 0 TO –48.4dB AD605
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Single-ended unipolar gain control
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Output common mode independently set
0 Figure 1.
Power shutdown at lower end of gain control Single 5 V supply Low power: 90 mW/channel Drives ADCs directly APPLICATIONS Ultrasound and sonar time-gain controls High performance AGC systems Signal measurement GENERAL DESCRIPTION
The AD605 is a low noise, accurate, dual-channel, linear-in-dB Each independent channel of the AD605 provides a gain range variable gain amplifier (VGA), optimized for any application of 48 dB that can be optimized for the application. Gain ranges requiring high performance, wide bandwidth variable gain between −14 dB to +34 dB and 0 dB to +48 dB can be selected control. Operating from a single 5 V supply, the AD605 provides by a single resistor between Pin FBK and Pin OUT. The lower differential inputs and unipolar gain control for ease of use. and upper gain ranges are determined by shorting Pin FBK to Added flexibility is achieved with a user-determined gain range Pin OUT or leaving Pin FBK unconnected, respectively. The and an external reference input that provide user-determined two channels of the AD605 can be cascaded to provide 96 dB gain scaling (dB/V). of very accurate gain range in a monolithic package. The high performance linear-in-dB response of the AD605 is The gain control interface provides an input resistance of achieved with the differential input, single-supply, exponential approximately 2 MΩ and scale factors from 20 dB/V to 30 dB/V amplifier (DSX-AMP) architecture. Each of the DSX-AMPs for a VREF input voltage of 2.5 V to 1.67 V, respectively. Note comprises a variable attenuator of 0 dB to −48.4 dB followed by that scale factors up to 40 dB/V are achievable with reduced a high speed, fixed-gain amplifier. The attenuator is based on a accuracy for scales above 30 dB/V. The gain scales linearly in dB 7-stage R-1.5R ladder network. The attenuation between tap with control voltages (VGN) of 0.4 V to 2.4 V for the 20 dB/V points is 6.908 dB, and 48.360 dB for the entire ladder network. scale and 0.20 V to 1.20 V for the 40 dB/V scale. When VGN is The DSX-AMP architecture results in 1.8 nV/√Hz input noise <50 mV, the amplifier is powered down to draw 1.9 mA. Under spectral density and accepts a ±2.0 V input signal when VOCM normal operation, the quiescent supply current of each amplifier is biased at VP/2. channel is only 18 mA. The AD605 is available in a 16-lead PDIP and a 16-lead SOIC_N package and is guaranteed for operation over the −40°C to +85°C temperature range.
Rev. F 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 license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Tel: 781.329.4700 www.analog.com Trademarks and registered trademarks are the property of their respective owners. Fax: 781.461.3113 ©1996–2008 Analog Devices, Inc. All rights reserved.
Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM GENERAL DESCRIPTION TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS (PER CHANNEL) THEORY OF OPERATION DIFFERENTIAL LADDER (ATTENUATOR) AC COUPLING GAIN CONTROL INTERFACE FIXED GAIN AMPLIFIER AND INTERPOLATOR CIRCUITS—APPLYING AN ACTIVE FEEDBACK AMPLIFIER APPLICATIONS INFORMATION CONNECTING TWO AMPLIFIERS TO DOUBLE THE GAIN RANGE EVALUATION BOARD INPUT CONNECTIONS ADJUSTING GAIN, COMMON-MODE, AND REFERENCE LEVELS OUTPUT CONNECTIONS OUTLINE DIMENSIONS ORDERING GUIDE