High Speed Amplifier

Low Noise, High Speed Amplifier for 16-Bit Systems AD8021 FEATURES Low noise 2.1 nV/√Hz input voltage noise 2.1 pA/√Hz input current noise Custom compensation Constant bandwidth from G = −1 to G = −10 High speed 200 MHz (G = −1) 190 MHz (G = −10) Low power 34 mW or 6.7 mA typical for 5 V supply Output disable feature, 1.3 mA Low distortion −93 dBc second harmonic, fC = 1 MHz −108 dBc third harmonic, fC = 1 MHz DC precision 1 mV maximum input offset voltage 0.5 μV/°C input offset voltage drift Wide supply range, 5 V to 24 V Low price Small packaging Available in SOIC-8 and MSOP-8 CONNECTION DIAGRAM LOGIC 1 REFERENCE –IN 2 +IN 3 –VS 4 AD8021 8 7 6 5 DISABLE +VS VOUT CCOMP 01888-001 Figure 1. SOIC-8 (R-8) and MSOP-8 (RM-8) The AD8021 allows the user to choose the gain bandwidth product that best suits the application. With a single capacitor, the user can compensate the AD8021 for the desired gain with little trade-off in bandwidth. The AD8021 is a well-behaved amplifier that settles to 0.01% in 23 ns for a 1 V step. It has a fast overload recovery of 50 ns. The AD8021 is stable over temperature with low input offset voltage drift and input bias current drift, 0.5 μV/°C and 10 nA/°C, respectively. The AD8021 is also capable of driving a 75 Ω line with ±3 V video signals. www.DataSheet4U.com APPLICATIONS ADC preamps and drivers Instrumentation preamps Active filters Portable instrumentation Line receivers Precision instruments Ultrasound signal processing High gain circuits The AD8021 is both technically superior and priced considerably less than comparable amps drawing much higher quiescent current. The AD8021 is a high speed, general-purpose amplifier, ideal for a wide variety of gain configurations and can be used throughout a signal processing chain and in control loops. The AD8021 is available in both standard 8-lead SOIC and MSOP packages in the industrial temperature range of −40°C to +85°C. 24 21 18 CLOSED-LOOP GAIN (dB) VOUT = 50mV p-p G = –10, RF = 1kΩ, RG = 100Ω, RIN = 100Ω, CC = 0pF G = –5, RF = 1kΩ, RG = 200Ω, RIN = 66.5Ω, CC = 1.5pF GENERAL DESCRIPTION The AD8021 is an exceptionally high performance, high speed voltage feedback amplifier that can be used in 16-bit resolution systems. It is designed to have both low voltage and low current noise (2.1 nV/√Hz typical and 2.1 pA/√Hz typical) while operating at the lowest quiescent supply current (7 mA @ ±5 V) among today’s high speed, low noise op amps. The AD8021 operates over a wide range of supply voltages from ±2.25 V to ±12 V, as well as from single 5 V supplies, making it ideal for high speed, low power instruments. An output disable pin allows further reduction of the quiescent supply current to 1.3 mA. 15 12 9 6 3 0 –3 –6 0.1M G = –2, RF = 499Ω, RG = 249Ω, RIN = 63.4Ω, CC = 4pF G = –1, RF = 499Ω, RG = 499Ω, RIN = 56.2Ω, CC = 7pF 1M 10M FREQUENCY (Hz) 100M 1G Figure 2. Small Signal Frequency Response 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 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. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2006 Analog Devices, Inc. All rights reserved. 01888-002 AD8021 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Connection Diagram ....................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 7 Maximum Power Dissipation ..................................................... 7 ESD Caution.................................................................................. 7 Pin Configuration and Function Descriptions............................. 8 Typical Performance Characteristics ............................................. 9 Test Circuits................................................................................. 17 Applications..................................................................................... 19 Using the Disable Feature.......................................................... 20 Theory of Operation ...................................................................... 21 PCB Layout Considerations...................................................... 21 Driving 16-Bit ADCs ................................................................. 22 Differential Driver...................................................................... 22 Using the AD8021 in Active Filters ......................................... 23 Driving Capacitive Loads.......................................................... 23 Outline Dimensions ....................................................................... 25 Ordering Guide .......................................................................... 25 REVISION HISTORY 5/06—Rev. E to Rev. F Updated Format..................................................................Universal Changes to General Description .................................................... 1 Changes to Figure 3.......................................................................... 7 Changes to Figure 60...................................................................... 19 Changes to Table 9.......................................................................... 23 3/05—Rev. D to Rev. E Updated Format..................................................................Universal Change to Figure 19 ....................................................................... 11 Change to Figure 25 ....................................................................... 12 Change to Table 7 and Table 8 ...................................................... 22 Change to Driving 16-Bit ADCs Section .................................... 22 10/03—Rev. C to Rev. D Updated Format..................................................................Universal 7/03—Rev. B to Rev. C Deleted All References to Evaluation Board...................Universal Replaced Figure 2 ..............................................................................5 Updated Outline Dimensions....................................................... 20 2/03—Rev. A to Rev. B Edits to Evaluation Board Applications....................................... 20 Edits to Figure 17 ........................................................................... 20 6/02—Rev. 0 to Rev. A Edits to Specifications .......................................................................2 Rev. F | Page 2 of 28 AD8021 SPECIFICATIONS VS = ±5 V, @ TA = 25°C, RL = 1 kΩ, gain = +2, unless otherwise noted. Table 1. Parameter DYNAMIC PERFORMANCE −3 dB Small Signal Bandwidth Conditions G = +1, CC = 10 pF, VO = 0.05 V p-p G = +2, CC = 7 pF, VO = 0.05 V p-p G = +5, CC = 2 pF, VO = 0.05 V p-p G = +10, CC = 0 pF, VO = 0.05 V p-p G = +1, CC = 10 pF G = +2, CC = 7 pF G = +5, CC = 2 pF G = +10, CC = 0 pF VO = 1 V step, RL = 500 Ω ±2.5 V input step, G = +2 Min 355 160 150 110 95 120 250 380 AD8021AR/AD8021ARM Typ Max 490 205 185 150 120 150 300 420 23 50 Unit MHz MHz MHz MHz V/μs V/μs V/μs V/μs ns ns Slew Rate, 1 V Step Settling Time to 0.01% Overload Recovery (50%) DISTORTION/NOISE PERFORMANCE f = 1 MHz HD2 HD3 f = 5 MHz HD2 HD3 Input Voltage Noise Input Current Noise Differential Gain Error Differential Phase Error DC PERFORMANCE Input Offset Voltage Input Offset Voltage Drift Input Bias Current Input Bias Current Drift Input Offset Current Open-Loop Gain INPUT CHARACTERISTICS Input Resistance Common-Mode Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Linear Output Current Short-Circuit Current Capacitive Load Drive for 30% Overshoot DISABLE CHARACTERISTICS Off Isolation Turn-On Time Turn-Off Time DISABLE Voltage—Off/On Enabled Leakage Current VO = 2 V p-p VO = 2 V p-p VO = 2 V p-p VO = 2 V p-p f = 50 kHz f = 50 kHz NTSC, RL = 150 Ω NTSC, RL = 150 Ω −93 −108 −70 −80 2.1 2.1 0.03 0.04 0.4 0.5 7.5 10 0.1 86 10 1 −4.1 to +4.6 −98 −3.8 to +3.4 60 75 15/120 −40 45 50 1.75/1.90 70 2 dBc dBc dBc dBc nV/√Hz pA/√Hz % Degrees mV μV/°C μA nA/°C ±μA dB MΩ pF V dB V mA mA pF dB ns ns V μA μA 2.6 1.0 10.5 0.5 TMIN to TMAX +Input or −input 82 VCM = ±4 V −86 −3.5 to +3.2 VO = 50 mV p-p/1 V p-p f = 10 MHz VO = 0 V to 2 V, 50% logic to 50% output VO = 0 V to 2 V, 50% logic to 50% output VDISABLE − VLOGIC REFERENCE LOGIC REFERENCE = 0.4 V DISABLE = 4.0 V Rev. F | Page 3 of 28 AD8021 Parameter Disabled Leakage Current POWER SUPPLY Operating Range Quiescent Current +Power Supply Rejection Ratio −Power Supply Rejection Ratio Conditions LOGIC REFERENCE = 0.4 V DISABLE = 0.4 V Min AD8021AR/AD8021ARM Typ Max 30 33 ±5 7.0 1.3 −95 −95 ±12.0 7.7 1.6 Unit μA μA V mA mA dB dB ±2.25 Output enabled Output disabled VCC = 4 V to 6 V, VEE = −5 V VCC = 5 V, VEE = −6 V to −4 V −86 −86 VS = ±12 V, @ TA = 25°C, RL = 1 kΩ, gain = +2, unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE −3 dB Small Signal Bandwi