Dual, Ultralow Noise Variable Gain Amplifier AD604 FEATURES FUNCTIONAL BLOCK DIAGRAM PAOx FBKx DSXx +DSXx VGNx Ultralow input noise at maximum gain 0.80 nV/Hz, 3.0 pA/Hz GAIN CONTROL VREF AD604 2 independent linear-in-dB channels AND SCALING Absolute gain range per channel programmable 0dB TO 48.4dB DIFFERENTIAL 0 dB to 48 dB (preamplifier gain = 14 dB) through 6 dB to PASSIVE INPUT ATTENUATOR PAIx 54 dB (preamplifier gain = 20 dB) AFA OUTx R-1.5R 1.0 dB gain accuracy LADDER 40 VOCM NETWORK Bandwidth: 40 MHz (3 dB) FIXED GAIN 32 Input resistance: 300 k AMPLIFIER 34.4dB Variable gain scaling: 20 dB/V through 40 dB/V 8 Stable gain with temperature and supply variations Single-ended unipolar gain control COMx Power shutdown at lower end of gain control Figure 1. Drive ADCs directly APPLICATIONS Ultrasound and sonar time-gain controls High performance AGC systems Signal measurement GENERAL DESCRIPTION Preamplifier gains between 5 and 10 (14 dB and 20 dB) provide The AD604 is an ultralow noise, very accurate, dual-channel, overall gain ranges per channel of 0 dB through 48 dB and 6 dB linear-in-dB variable gain amplifier (VGA) optimized for time- through 54 dB. The two channels of the AD604 can be cascaded based variable gain control in ultrasound applications however, to provide greater levels of gain range by bypassing the preamplifier it supports any application requiring low noise, wide bandwidth, of the second channel. However, in multiple channel systems, variable gain control. Each channel of the AD604 provides a cascading the AD604 with other devices in the AD60x VGA 300 k input resistance and unipolar gain control for ease of family that do not include a preamplifier may provide a more use. User-determined gain ranges, gain scaling (dB/V), and dc efficient solution. The AD604 provides access to the output of level shifting of output further optimize performance. the preamplifier, allowing for external filtering between the Each channel of the AD604 uses a high performance preamplifier and the differential attenuator stage. preamplifier that provides an input-referred noise voltage of Note that scale factors up to 40 dB/V are achievable with reduced 0.8 nV/Hz. The very accurate linear-in-dB response of the accuracy for scales above 30 dB/V. The gain scales linearly in AD604 is achieved with the differential input exponential decibels with control voltages of 0.4 V to 2.4 V with the 20 dB/V amplifier (DSX-AMP) architecture. Each DSX-AMP comprises scale. Below and above this gain control range, the gain begins a variable attenuator of 0 dB to 48.36 dB followed by a high to deviate from the ideal linear-in-dB control law. The gain speed fixed-gain amplifier. The attenuator is a 7-stage control region below 0.1 V is not used for gain control. When R-1.5R ladder network. The attenuation between tap points is the gain control voltage is <50 mV, the amplifier channel is 6.908 dB and 48.36 dB for the ladder network. powered down to 1.9 mA. The equation for the linear-in-dB gain response is The AD604 is available in 24-lead SSOP, SOIC, and PDIP G (dB) = packages and is guaranteed for operation over the 40C to (Gain Scaling (dB/V) VGN (V)) + (Preamp Gain (dB) 19 dB) +85C temperature range. Rev. G 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 19962010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. 00540-001AD604 TABLE OF CONTENTS Features .............................................................................................. 1 Applications Information .............................................................. 18 Applications ....................................................................................... 1 Ultralow Noise AGC Amplifier with 82 dB to 96 dB Gain R ange ............................................................................................ 19 Functional Block Diagram .............................................................. 1 Ultralow Noise, Differential Input-Differential Output VGA General Description ......................................................................... 1 ....................................................................................................... 21 Revision History ............................................................................... 2 Medical Ultrasound TGC Driving the AD9050, a 10-Bit, 40 Specif icat ions ..................................................................................... 3 MSPS ADC .................................................................................. 22 Absolute Maximum Ratings ............................................................ 5 Evaluation Board ............................................................................ 24 ESD Caution .................................................................................. 5 Connecting a Waveform to the AD604-EVALZ ........................ 24 Pin Configuration and Function Descriptions ............................. 6 DSX Input Connections ............................................................ 24 Typical Performance Characteristics ............................................. 7 Preamplifier Gain ....................................................................... 25 Theory of Operation ...................................................................... 13 Outputs ........................................................................................ 25 Preamplifier ................................................................................. 14 DC Operating Conditions ......................................................... 25 Differential Ladder (Attenuator) .............................................. 15 Evaluation Board Artwork and Schematic ............................. 26 AC Coupling ............................................................................... 16 Outline Dimensions ....................................................................... 28 Gain Control Interface ............................................................... 16 Ordering Guide .......................................................................... 29 Active Feedback Amplifier (Fixed-Gain Amp) ...................... 16 REVISION HISTORY 12/10Rev. F to Rev. G Changes to An Ultralow Noise AGC Amplifier with 82 dB to Changes to Figure 1 .......................................................................... 1 96 dB Gain Range Section ............................................................. 19 Changes to Figure 55 and Figure 56............................................. 24 Changes to Evaluation Board Section, Figure 55, Using the Preamplifier Section, Figure 56, and DSX Input Connections Changes to Cascaded DSX Section and Outputs Section ......... 25 Section .............................................................................................. 24 Changes to Figure 57 to Figure 60 ................................................ 26 Changes to Preamplifier Gain Section, Outputs Section, DC Changes to Figure 61 and Table 6................................................. 27 Operating Conditions Section, Table 4 and Table 5................... 25 Changes to Ordering Guide .......................................................... 29 Added Figure 57 Renumbered Sequentially .............................. 25 3/07Rev. B to Rev. C Changes to Figure 58 to Figure 61 ................................................ 26 Added Evaluation Board Section ................................................. 24 Added Figure 62 .............................................................................. 26 Added Evaluation Board Artwork and Schematics Section ..... 26 Changes to Figure 63 ...................................................................... 27 Changes to Ordering Guide .......................................................... 29 Updated Outline Dimensions ....................................................... 28 12/06Rev. A to Rev. B 4/10Rev. E to Rev. F Changes to General Description .....................................................1 Changes to Figure 55, DSX Input Connections Section, and Changes to Figure 54 ...................................................................... 23 Differential DSX Inputs Section ................................................... 24 Changes to Ordering Guide .......................................................... 25 Changes to Figure 61, Deleted Table 6 ......................................... 27 1/04Rev. 0 to Rev. A Changes to Ordering Guide .......................................................... 29 Changes to Specifications .................................................................2 10/08Rev. D to Rev. E Changes to Absolute Maximum Ratings ........................................3 Changes to Figure 1 .......................................................................... 1 Changes to Ordering Guide .............................................................3 Changes to Figure 37 ...................................................................... 13 Changes to Figure 1 Caption............................................................5 Changes to Figure 41 ...................................................................... 15 Changes to Figure 11 Caption .........................................................6 Changes to Evaluation Board Model Name ................................ 24 Changes to Figure 17 .........................................................................6 Changes to Ordering Guide .......................................................... 29 Changes to Figure 51 ...................................................................... 17 1/08Rev. C to Rev. D Updated Outline Dimensions ....................................................... 18 Changes to AC Coupling Section ................................................. 16 10/96Revision 0: Initial Version Changes to Applications Information Section ............................ 18 Rev. G Page 2 of 32