AD8066

High Performance, 145 MHz FastFET™ Op Amps AD8065/AD8066 FEATURES FET input amplifier 1 pA input bias current Low cost High speed: 145 MHz, −3 dB bandwidth (G = +1) 180 V/μs slew rate (G = +2) Low noise 7 nV/√Hz (f = 10 kHz) 0.6 fA/√Hz (f = 10 kHz) Wide supply voltage range: 5 V to 24 V Single-supply and rail-to-rail output Low offset voltage 1.5 mV maximum High common-mode rejection ratio: −100 dB Excellent distortion specifications SFDR −88 dBc @ 1 MHz Low power: 6.4 mA/amplifier typical supply current No phase reversal Small packaging: SOIC-8, SOT-23-5, and MSOP-8 APPLICATIONS Instrumentation Photodiode preamps Filters A/D drivers Level shifting Buffering CONNECTION DIAGRAMS VOUT 1 –VS 2 +IN 3 4 AD8065 5 +VS NC 1 –IN 2 AD8065 8 7 6 NC +VS VOUT NC TOP VIEW (Not to Scale) –IN +IN 3 –VS 4 TOP VIEW (Not to Scale) 5 AD8066 VOUT1 1 –IN1 2 +IN1 3 –VS 4 TOP VIEW (Not to Scale) 8 7 6 5 +VS VOUT2 –IN2 +IN2 02916-E-001 Figure 1. GENERAL DESCRIPTION The AD8065/AD80661 FastFET amplifiers are voltage feedback amplifiers with FET inputs offering high performance and ease of use. The AD8065 is a single amplifier, and the AD8066 is a dual amplifier. These amplifiers are developed in the Analog Devices, Inc. proprietary XFCB process and allow exceptionally low noise operation (7.0 nV/√Hz and 0.6 fA/√Hz) as well as very high input impedance. With a wide supply voltage range from 5 V to 24 V, the ability to operate on single supplies, and a bandwidth of 145 MHz, the AD8065/AD8066 are designed to work in a variety of applications. For added versatility, the amplifiers also contain rail-to-rail outputs. Despite the low cost, the amplifiers provide excellent overall performance. The differential gain and phase errors of 0.02% and 0.02°, respectively, along with 0.1 dB flatness out to 7 MHz, make these amplifiers ideal for video applications. Additionally, they offer a high slew rate of 180 V/μs, excellent distortion (SFDR of −88 dBc @ 1 MHz), extremely high common-mode rejection of −100 dB, and a low input offset voltage of 1.5 mV maximum under warmed up conditions. The AD8065/ AD8066 1 operate using only a 6.4 mA/amplifier typical supply current and are capable of delivering up to 30 mA of load current. The AD8065/AD8066 are high performance, high speed, FET input amplifiers available in small packages: SOIC-8, MSOP-8, and SOT-23-5. They are rated to work over the industrial temperature range of −40°C to +85°C. 24 21 18 15 GAIN (dB) G = +10 VO = 200mV p-p G = +5 12 9 G = +2 6 3 G = +1 0 –3 02916-E-002 –6 0.1 1 10 FREQUENCY (MHz) 100 1000 Figure 2. Small Signal Frequency Response Protected by U. S. Patent No. 6,262,633. 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 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. AD8065/AD8066 TABLE OF CONTENTS Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Specifications..................................................................................... 3 Absolute Maximum Ratings............................................................ 6 ESD Caution.................................................................................. 6 Maximum Power Dissipation ..................................................... 7 Output Short Circuit .................................................................... 7 Typical Performance Characteristics ............................................. 8 Test Circuits................................................................................. 15 Theory of Operation ...................................................................... 18 Closed-Loop Frequency Response........................................... 18 Noninverting Closed-Loop Frequency Response.................. 18 Inverting Closed-Loop Frequency Response ......................... 18 Wideband Operation ................................................................. 19 Input Protection ......................................................................... 19 Thermal Considerations............................................................ 20 Input and Output Overload Behavior ..................................... 20 Layout, Grounding, and Bypassing Considerations .................. 21 Power Supply Bypassing ............................................................ 21 Grounding ................................................................................... 21 Leakage Currents........................................................................ 22 Input Capacitance ...................................................................... 22 Output Capacitance ................................................................... 22 Input-to-Output Coupling ........................................................ 23 Wideband Photodiode Preamp ................................................ 23 High Speed JFET Input Instrumentation Amplifier.............. 24 Video Buffer ................................................................................ 24 Outline Dimensions ....................................................................... 25 Ordering Guide .......................................................................... 26 2/03—Data Sheet changed from Rev. A to Rev. B. Changes to Absolute Maximum Ratings...................................... 4 Changes to Test Circuit 10 ........................................................... 14 Changes to Test Circuit 11 ........................................................... 15 Changes to Noninverting Closed-Loop Frequency Response 16 Changes to Inverting Closed-Loop Frequency Response ....... 16 Updated Figure 6 .......................................................................... 18 Changes to Figure 7....................................................................... 19 Changes to Figure 10..................................................................... 21 Changes to Figure 11..................................................................... 22 Changes to High Speed JFET Instrumentation Amplifier....... 22 Changes to Video Buffer............................................................... 22 8/02—Data Sheet changed from Rev. 0 to Rev. A. Added AD8066 ..................................................................Universal Added SOIC-8 (R) and MSOP-8 (RM) ........................................ 1 Edits to General Description ......................................................... 1 Edits to Specifications ..................................................................... 2 New Figure 2 .................................................................................... 5 Changes to Ordering Guide ........................................................... 5 Edits to TPCs 18, 25, and 28 .......................................................... 8 New TPC 36 ................................................................................... 11 Added Test Circuits 10 and 11..................................................... 14 MSOP (RM-8) added.................................................................... 23 REVISION HISTORY 1/06—Rev. F to Rev. G Changes to Ordering Guide .......................................................... 26 12/05—Rev. E to Rev. F Updated Format..................................................................Universal Changes to Features.......................................................................... 1 Changes to General Description .................................................... 1 Changes to Figure 22 through Figure 27 ..................................... 11 Updated Outline Dimensions ....................................................... 25 Changes to Ordering Guide .......................................................... 26 2/04—Data Sheet Changed from Rev. D to Rev. E. Updated Format................................................................ Universal Updated Figure 56 ......................................................................... 21 Updated Outline Dimensions ...................................................... 25 Updated Ordering Guide.............................................................. 26 11/03—Data Sheet changed from Rev. C to Rev. D. Changes to Features......................................................................... 1 Changes to Connection Diagrams ................................................ 1 Updated Ordering Guide................................................................ 5 Updated Outline Dimensions ...................................................... 22 4/03—Data Sheet changed from Rev. B to Rev. C. Added SOIC-8 (R) for the AD8065............................................... 4 Rev. G | Page 2 of 28 AD8065/AD8066 SPECIFICATIONS @ TA = 25°C, VS = ±5 V, RL = 1 kΩ, unless otherwise noted. Table 1. Parameter DYNAMIC PERFORMANCE −3 dB Bandwidth Conditions G = +1, VO = 0.2 V p-p (AD8065) G = +1, VO = 0.2 V p-p (AD8066) G = +2, VO = 0.2 V p-p G = +2, VO = 2 V p-p G = +2, VO = 0.2 V p-p G = +1, −5.5 V to +5.5 V G = −1, −5.5 V to +5.5 V G = +2, VO = 4 V step G = +2, VO = 2 V step G = +2, VO = 8 V step fC = 1 MHz, G = +2, VO = 2 V p-p fC = 5 MHz, G = +2, VO = 2 V p-p fC = 1 MHz, G = +2, VO = 8 V p-p fC = 10 MHz, RL = 100 Ω f = 10 kHz f = 10 kHz NTSC, G = +2, RL = 150 Ω NTSC, G = +2, RL = 150 Ω VCM = 0 V, SOIC package SOIC package TMIN to TMAX TMIN to TMAX VO = ±3 V, RL = 1 kΩ Min 100 100 Typ 145 120 50 42 7 175 170 180 55 205 −88 −67 −73 24 7 0.6 0.02 0.02 0.4 1 2 25 1 1 113 1000 || 2.1 1000 || 4.5 −5 to +1.7 See the Theory of Operation section VCM = −1 V to +1 V VCM = −1 V to +1 V (SOT-23) RL = 1 kΩ RL = 150 Ω VO = 9 V p-p, SFDR ≥ −60 dBc, f = 500 kHz 30% overshoot G = +1 5 ±PSRR −85 6.4 −100 −85 −82 −4.88 to +4.90 −5.0 to +2.4 −5.0 to +5.0 −100 −91 −4.94 to +4.95 −4.8 to +4.7 35 90 20 24 7.2 1.5 17 6 10 Max Unit MHz MHz MHz MHz MHz ns ns V/μs ns ns dBc dBc dBc dBm nV/√Hz fA/√Hz % Degrees mV μV/°C pA pA pA pA dB GΩ || pF GΩ || pF V V dB dB V V mA mA pF V mA dB Bandwidth for 0.1 dB Flatness Input Overdrive Recovery Time Output Recovery Time Slew Rate Settling Time to 0.1% NOISE/HARMONIC PERFORMANCE SFDR 130 Third-Order Intercept 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 Offset Current Open-Loop Gain INPUT CHARACTERISTICS Common-Mode Input Impedance Differential Input Impedance Input Common-Mode Voltage Range FET Input Range Usable Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Output Current Short-Circuit Current Capacitive Load Drive POWER SUPPLY Operating Range Quiescent Current per Amplifier Power Supply Rejection Ratio 100 Rev. G | Page 3 of 28 AD8065/AD8066 @ TA = 25°C, VS = ±12 V, RL = 1 kΩ, unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE −3 dB Bandwidth Conditions G = +1, VO = 0.2 V p-p (AD8065) G = +1, VO = 0.2 V p-p (AD8066) G = +2, VO = 0.2 V p-p G = +2, VO = 2 V p-p G = +2, VO = 0.2 V p-p G = +1, −12.5 V to +12.5 V G = −1, −12.5 V to +12.5 V G = +2, VO = 4 V step G = +2, VO = 2 V step G = +2, VO = 10 V step fC = 1 MHz, G = +2, VO = 2 V p-p fC = 5 MHz, G = +2, VO = 2 V p-p fC = 1 MHz, G = +2, VO = 10 V p-p fC = 10 MHz, RL = 100 Ω f = 10 kHz f = 10 kHz NTSC, G = +2, RL = 150 Ω NTSC, G = +2, RL = 150 Ω VCM = 0 V, SOIC package SOIC package TMIN to TMAX TMIN to TMAX VO = ±10 V, RL = 1 kΩ Min 100 100 Typ 145 115 50 40 7 175 170 180 55 250 −100 −67 −85 24 7 1 0.04 0.03 0.4 1 3 25 2 2 114 1000 || 2.1 1000 || 4.5 −12 to +8.5 See the Theory of Operation section VCM = −1 V to +1 V VCM = −1 V to +1 V (SOT-23) RL = 1 kΩ RL = 350 Ω VO = 22 V p-p, SFDR ≥ −60 dBc, f = 500 kHz 30% overshoot G = +1 5 ±PSRR −84 6.6 −93 −85 −82 −11.8 to +11.8 −12.0 to +9.5 −12.0 to +12.0 −100 −91 −11.9 to +11.9 −11.25 to +11.5 30 120 25 24 7.4 1.5 17 7 10 Max Unit MHz MHz MHz MHz MHz ns ns V/μs ns ns dBc dBc dBc dBm nV/√Hz fA/√Hz % Degrees mV μV/°C pA pA pA pA dB GΩ || pF GΩ || pF V V dB dB V V mA mA pF V mA dB Bandwidth for 0.1 dB Flatness Input Overdrive Recovery Output Overdrive Recovery Slew Rate Settling Time to 0.1% NOISE/HARMONIC PERFORMANCE SFDR 130 Third-Order Intercept 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 Offset Current Open-Loop Gain INPUT CHARACTERISTICS Common-Mode Input Impedance Differential Input Impedance Input Common-Mode Voltage Range FET Input Range Usable Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Output Current Short-Circuit Current Capacitive Load Drive POWER SUPPLY Operating Range Quiescent Current per Amplifier Power Supply Rejection Ratio 103 Rev. G | Page 4 of 28 AD8065/AD8066 @ TA = 25°C, VS = 5 V, RL = 1 kΩ, unless otherwise noted. Table 3. Parameter DYNAMIC PERFORMANCE −3 dB Bandwidth Conditions G = +1, VO = 0.2 V p-p (AD8065) G = +1, VO = 0.2 V p-p (AD8066) G = +2, VO = 0.2 V p-p G = +2, VO = 2 V p-p G = +2, VO = 0.2 V p-p G = +1, −0.5 V to +5.5 V G = −1, −0.5 V to +5.5 V G = +2, VO = 2 V step G = +2, VO = 2 V step fC = 1 MHz, G = +2, VO = 2 V p-p fC = 5 MHz, G = +2, VO = 2 V p-p fC = 10 MHz, RL = 100 Ω f = 10 kHz f = 10 kHz NTSC, G = +2, RL = 150 Ω NTSC, G = +2, RL = 150 Ω VCM = 1.0 V, SOIC package SOIC package TMIN to TMAX TMIN to TMAX VO = 1 V to 4 V (AD8065) VO = 1 V to 4 V (AD8066) Min 125 110 Typ 155 130 50 43 6 175 170 160 60 −65 −50 22 7 0.6 0.13 0.16 0.4 1 1 25 1 1 113 103 1000 || 2.1 1000 || 4.5 0 to 1.7 See the Theory of Operation section VCM = 0.5 V to 1.5 V VCM = 1 V to 2 V (SOT-23) RL = 1 kΩ RL = 150 Ω VO = 4 V p-p, SFDR ≥ −60 dBc, f = 500 kHz 30% overshoot G = +1 5 5.8 −78 −74 −78 0.1 to 4.85 0 to 2.4 0 to 5.0 −100 −91 0.03 to 4.95 0.07 to 4.83 35 75 5 24 7.0 1.5 17 5 5 Max Unit MHz MHz MHz MHz MHz ns ns V/μs ns dBc dBc dBm nV/√Hz fA/√Hz % Degrees mV μV/ºC pA pA pA pA dB dB GΩ || pF GΩ || pF V V dB dB V V mA mA pF V mA dB Bandwidth for 0.1 dB Flatness Input Overdrive Recovery Time Output Recovery Time Slew Rate Settling Time to 0.1% NOISE/HARMONIC PERFORMANCE SFDR Third-Order Intercept 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 Offset Current Open-Loop Gain INPUT CHARACTERISTICS Common-Mode Input Impedance Differential Input Impedance Input Common-Mode Voltage Range FET Input Range Usable Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Output Current Short-Circuit Current Capacitive Load Drive POWER SUPPLY Operating Range Quiescent Current per Amplifier Power Supply Rejection Ratio 105 100 90 ±PSRR 6.4 −100 Rev. G | Page 5 of 28 AD8065/AD8066 ABSOLUTE MAXIMUM RATINGS Table 4. Parameter Supply Voltage Power Dissipation Common-Mode Input Voltage Differential Input Voltage Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering, 10 sec) Rating 26.4 V See Figure 3 VEE − 0.5 V to VCC + 0.5 V 1.8 V −65°C to +125°C −40°C to +85°C 300°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. G | Page 6 of 28 AD8065/AD8066 MAXIMUM POWER DISSIPATION The maximum safe power dissipation in the AD8065/AD8066 packages is limited by the associated rise in junction temperature (TJ) on the die. The plastic encapsulating the die locally reaches the junction temperature. At approximately 150°C, which is the glass transition temperature, the plastic changes its properties. Even temporarily exceeding this temperature limit can change the stresses that the package exerts on the die, permanently shifting the parametric performance of the AD8065/AD8066. Exceeding a junction temperature of 175°C for an extended time can result in changes in the silicon devices, potentially causing failure. The still air thermal properties of the package and PCB (θJA), ambient temperature (TA), and total power dissipated in the package (PD) determine the junction temperature of the die. The junction temperature can be calculated by TJ = TA + (PD × θJA) The power dissipated in the package (PD) is the sum of the quiescent power dissipation and the power dissipated in the package due to the load drive for all outputs. The quiescent power is the voltage between the supply pins (VS) times the quiescent current (IS). Assuming the load (RL) is referenced to midsupply, then the total drive power is VS /2 × IOUT, some of which is dissipated in the package and some in the load (VOUT × IOUT). The difference between the total drive power and the load power is the drive power dissipated in the package. PD = Quiescent Power + (Total Drive Power − Load Power ) ⎞ V OUT ⎛V V PD = (VS × I S ) + ⎜ S × OUT ⎟ − 2 RL ⎠ RL ⎝ 2 2.0 MAXIMUM POWER DISSIPATION (W) 1.5 MSOP-8 SOIC-8 1.0 SOT-23-5 0.5 –40 –20 0 20 40 60 80 100 AMBIENT TEMPERATURE (°C) Figure 3. Maximum Power Dissipation vs. Temperature for a 4-Layer Board Airflow increases heat dissipation, effectively reducing θJA. Also, more metal directly in contact with the package leads from metal traces, through holes, ground, and power planes reduce the θJA. Care must be taken to minimize parasitic capacitances at the input leads of high speed op amps as discussed in the Layout, Grounding, and Bypassing Considerations section. Figure 3 shows the maximum safe power dissipation in the package vs. the ambient temperature for the SOIC (125°C/W), SOT-23 (180°C/W), and MSOP (150°C/W) packages on a JEDEC standard 4-layer board. θJA values are approximations. OUTPUT SHORT CIRCUIT Shorting the output to ground or drawing excessive current for the AD8065/AD8066 will likely cause catastrophic failure. RMS output voltages should be considered. If RL is referenced to VS−, as in single-supply operation, then the total drive power is VS × IOUT. If the rms signal levels are indeterminate, then consider the worst case, when VOUT = VS/4 for RL to midsupply. PD = (VS × I S ) + (VS /4 )2 RL In single-supply operation with RL referenced to VS−, worst case is VOUT = VS/2. Rev. G | Page 7 of 28 02916-E-003 0 –60 AD8065/AD8066 TYPICAL PERFORMANCE CHARACTERISTICS Default Conditions: ±5 V, CL = 5 pF, RL = 1 kΩ, VOUT = 2 V p-p, Temperature = 25°C. 24 21 18 15 GAIN (dB) 6.9 G = +10 VO = 200mV p-p 6.7 G = +5 GAIN (dB) RL = 150Ω G = +2 VOUT = 0.2V p-p VOUT = 0.7V p-p VOUT = 1.4V p-p 6.8 6.6 6.5 6.4 6.3 6.2 12 9 G = +2 6 3 G = +1 0 –3 02916-E-004 6.1 6.0 02916-E-007 02916-E-009 02916-E-008 –6 0.1 1 10 FREQUENCY (MHz) 100 1000 5.9 0.1 1 10 FREQUENCY (MHz) 100 Figure 4. Small Signal Frequency Response for Various Gains 6 VO = 200mV p-p G = +1 4 VS = +5V 2 GAIN (dB) GAIN (dB) Figure 7. 0.1 dB Flatness Frequency Response (See Figure 43) 9 VO = 200mV p-p G = +2 8 VS = +5V VS = ±5V 7 VS = ±5V 0 VS = ±12V –2 6 VS = ±12V 5 –4 4 1 10 FREQUENCY (MHz) 100 1000 02916-E-005 –6 0.1 3 0.1 1 10 FREQUENCY (MHz) 100 1000 Figure 5. Small Signal Frequency Response for Various Supplies (See Figure 42) 2 VO = 2V p-p 1 0 VS = ±5V GAIN (dB) GAIN (dB) Figure 8. Small Signal Frequency Response for Various Supplies (See Figure 43) 8 G = +1 7 6 G = +2 VS = +5V VS = ±5V VS = ±12V 5 4 3 –1 VS = ±12V –2 –3 –4 2 1 02916-E-006 –5 0.1 1 10 FREQUENCY (MHz) 100 1000 0 0.1 1 10 FREQUENCY (MHz) 100 1000 Figure 6. Large Signal Frequency Response for Various Supplies (See Figure 42) Figure 9. Large Signal Frequency Response for Various Supplies (See Figure 43) Rev. G | Page 8 of 28 AD8065/AD8066 9 VO = 200mV p-p G = +1 6 CL = 25pF CL = 20pF GAIN (dB) 2 0 –2 –4 8 CL = 25pF RSNUB = 20Ω 6 CL = 5pF 4 CL = 55pF CL = 25pF 3 GAIN (dB) 0 CL = 5pF –3 –6 –6 02916-E-010 VO = 200mV p-p G = +2 1 10 FREQUENCY (MHz) 100 1000 02916-E-013 02916-E-015 –9 0.1 1 10 FREQUENCY (MHz) 100 1000 –8 0.1 Figure 10. Small Signal Frequency Response for Various CLOAD (See Figure 42) 8 VOUT = 0.2V p-p 6 G = +2 4 2 VOUT = 4V p-p 0 –2 –4 –6 02916-E-011 Figure 13. Small Signal Frequency Response for Various CLOAD (See Figure 43) 8 7 RL = 100Ω VOUT = 2V p-p 6 5 4 3 2 1 0 0.1 VO = 200mV p-p G = +2 1 10 FREQUENCY (MHz) 100 1000 02916-E-014 RL = 1kΩ GAIN (dB) –8 0.1 1 10 FREQUENCY (MHz) 100 1000 Figure 11. Frequency Response for Various Output Amplitudes (See Figure 43) 14 VO = 200mV p-p 12 10 8 G = +2 RF = RG = 1kΩ, RS = 500Ω RF = RG = 500Ω, RS = 250Ω RF = RG = 500Ω, RS = 250Ω, CF = 2.2pF Figure 14. Small Signal Frequency Response for Various RLOAD (See Figure 43) 80 120 GAIN (dB) PHASE 60 OPEN-LOOP GAIN (dB) 60 PHASE (DEGREES) GAIN (dB) 40 GAIN 20 0 6 4 2 0 –2 RF = RG = 1kΩ, RS = 500Ω, CF = 3.3pF –60 0 –120 02916-E-012 –4 0.1 1 10 FREQUENCY (MHz) 100 1000 –20 0.01 0.1 1 10 100 –180 1000 FREQUENCY (MHz) Figure 12. Small Signal Frequency Response for Various RF/CF (See Figure 43) Figure 15. Open-Loop Response Rev. G | Page 9 of 28 AD8065/AD8066 –30 –40 –50 –60 DISTORTION (dBc) DISTORTION (dBc) –40 G = +2 –50 –60 –70 –80 –90 –100 –110 02916-E-016 HD2 G = +2 –70 HD2 G = +1 –80 HD3 G = +2 HD2 RL = 150Ω HD2 RL = 1kΩ HD3 RL = 1kΩ HD3 RL = 150Ω –90 HD3 G = +1 –100 1 10 FREQUENCY (MHz) 100 1 10 FREQUENCY (MHz) 100 Figure 16. Harmonic Distortion vs. Frequency for Various Loads (See Figure 43) –30 –40 –50 DISTORTION (dBc) Figure 19. Harmonic Distortion vs. Frequency for Various Gains (See Figure 42 and Figure 43) –20 G = +2 VS = ±12V F = 1MHz DISTORTION (dBc) –30 –40 –50 –60 VS = ±12V G = +2 HD2 VO = 20V p-p HD3 VO = 20V p-p –60 –70 –80 –90 –100 –110 –120 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 OUTPUT AMPLITUDE (V p-p) HD3 RL = 300Ω HD2 RL = 150Ω HD3 RL = 150Ω HD2 RL = 300Ω HD2 VO = 10V p-p –70 –80 –90 –100 –110 HD2 VO = 2V p-p HD3 VO = 2V p-p 1.0 FREQUENCY (MHz) 10.0 02916-E-020 02916-E-021 HD3 VO = 10V p-p 02916-E-017 –120 0.1 Figure 17. Harmonic Distortion vs. Amplitude for Various Loads VS = ±12 V (See Figure 43) 50 RL = 100Ω 45 INTERCEPT POINT (dBm) Figure 20. Harmonic Distortion vs. Frequency for Various Amplitudes (See Figure 43) 100 VS = ±12V 40 35 NOISE (nV/ Hz) VS = ±5V 10 30 VS = +5V 25 20 02916-E-018 15 1 FREQUENCY (MHz) 10 1 10 100 1k 10k 100k 1M 10M 100M 1G FREQUENCY (Hz) Figure 18. Third-Order Intercept vs. Frequency and Supply Voltage Figure 21. Voltage Noise Rev. G | Page 10 of 28 02916-E-019 –120 0.1 –110 0.1 AD8065/AD8066 G = +1 CL = 20pF CL = 5pF G = +1 50mV/DIV 50mV/DIV 25ns/DIV 25ns/DIV 02916-022 Figure 22. Small Signal Transient Response 5 V Supply (See Figure 42) G = +1 VS = ±12V Figure 25. Small Signal Transient Response ±5 V (See Figure 42) G = +2 5µs VS = ±12V VOUT = 10V p-p VOUT = 10V p-p VOUT = 4V p-p VOUT = 2V p-p VOUT = 2V p-p 2V/DIV 50ns/DIV 02916-023 2V/DIV 50ns/DIV 02916-026 Figure 23. Large Signal Transient Response (See Figure 42) G = –1 VS = ±5V Figure 26. Large Signal Transient Response (See Figure 43) G = +1 VS = ±5V 2.0V/DIV 2.0V/DIV 100ns/DIV 02916-024 100ns/DIV Figure 24. Output Overdrive Recovery (See Figure 44) Figure 27. Input Overdrive Recovery (See Figure 42) Rev. G | Page 11 of 28 02916-027 02916-025 AD8065/AD8066 VIN = 140mV/DIV VIN = 500mV/DIV +0.1% VOUT – 2VIN +0.1% –0.1% t=0 –0.1% t=0 VOUT – 2VIN 2mV/DIV 64 μs/DIV 02916-E-028 2mV/DIV 10ns/DIV 02916-E-031 Figure 28. Long-Term Settling Time (See Figure 49) 0 42 36 30 24 18 12 6 0 10 –15 +Ib Ib (pA) Figure 31. 0.1% Short-Term Settling Time (See Figure 49) +Ib –Ib BJT INPUT STAGE FET INPUT STAGE –5 INPUT BIAS CURRENT (pA) –Ib –10 Ib (μA) 5 0 –5 –10 –15 –20 –Ib –20 +Ib –25 02916-E-029 25 35 45 55 65 75 85 –8 –6 –4 –2 0 2 4 6 8 10 12 TEMPERATURE (°C) COMMON-MODE VOLTAGE (V) Figure 29. Input Bias Current vs. Temperature 0.3 Figure 32. Input Bias Current vs. Common-Mode Voltage Range (See the Input and Output Overload Behavior Section) 40 35 30 N = 299 SD = 0.388 MEAN = –0.069 0.2 OFFSET VOLTAGE (mV) 0.1 VS = +5V 0 VS = ±5V 25 20 15 10 –0.2 5 02916-E-030 02916-E-033 –0.1 VS = ±12V –0.3 –14 –12 –10 –8 –6 –4 –2 0 2 4 6 8 10 12 14 0 –2.0 –1.5 –1.0 –0.5 0 0.5 1.0 1.5 2.0 COMMON-MODE VOLTAGE (V) INPUT OFFSET VOLTAGE (mV) Figure 30. Input Offset Voltage vs. Common-Mode Voltage Figure 33. Input Offset Voltage Rev. G | Page 12 of 28 02916-E-032 –30 –25 –30 –12 –10 AD8065/AD8066 –30 100 –40 10 –50 CMRR (dB) OUTPUT IMPEDANCE (Ω) –60 1 G = +1 –70 VS = ±12V G = +2 0.1 –80 –90 VS = ±5V 0.01 02916-E-034 1 10 FREQUENCY (MHz) 100 1k 10k 100k 1M 10M 100M FREQUENCY (Hz) Figure 34. CMRR vs. Frequency (See Figure 46) 0.30 Figure 37. Output Impedance vs. Frequency (See Figure 45 and Figure 47) 80 0.25 VCC – VOH 0.20 OUTPUT SATURATION VOLTAGE (mV) OUTPUT SATURATION VOLTAGE (V) 70 VCC – VOH 60 0.15 50 VOL – VEE 0.10 VOL – VEE 0.05 40 02916-E-035 0 10 20 ILOAD (mA) 30 40 25 35 45 55 65 75 85 TEMPERATURE (°C) Figure 35. Output Saturation Voltage vs. Output Load Current 0 –10 –20 –30 –PSRR +PSRR 0 –10 –20 Figure 38. Output Saturation Voltage vs. Temperature VIN = 2V p-p G = +1 PSRR (dB) –40 –50 –60 –70 –80 –90 CROSSTALK (dB) –30 –40 –50 –60 –70 A TO B –80 B TO A 02916-E-036 0.1 1 10 100 1000 1 10 FREQUENCY (MHz) 100 FREQUENCY (MHz) Figure 36. PSRR vs. Frequency (See Figure 48 and Figure 50) Figure 39. Crosstalk vs. Frequency (See Figure 51) Rev. G | Page 13 of 28 02916-E-039 –100 0.01 –90 0.1 02916-E-038 0 30 02916-E-037 –100 0.1 0 100 AD8065/AD8066 6.60 VS = ±12V 6.55 VS = ±5V 120 115 VS = ±12V 125 SUPPLY CURRENT (mA) OPEN-LOOP GAIN (dB) 6.50 6.45 VS = +5V 6.40 110 105 100 95 VS = ±5V 90 VS = +5V 6.35 6.30 6.25 –40 85 02916-E-040 02916-E-041 80 0 10 20 ILOAD (mA) 30 40 –20 0 20 40 60 80 TEMPERATURE (°C) Figure 40. Quiescent Supply Current vs. Temperature for Various Supply Voltages Figure 41. Open-Loop Gain vs. Load Current for Various Supply Voltages Rev. G | Page 14 of 28 AD8065/AD8066 TEST CIRCUITS SOIC-8 Pinout +VCC 4.7μF +VCC 4.7μF 0.1μF 24.9Ω 499Ω 49.9Ω 2.2pF 499Ω 0.1μF VIN RSNUB FET PROBE FET PROBE AD8065 VIN 49.9Ω 1kΩ 0.1μF CLOAD 249Ω AD8065 1kΩ 0.1μF 02916-E-042 4.7μF –VEE –VEE Figure 42. G = +1 +VCC 4.7μF Figure 44. G = −1 +VCC 4.7μF 0.1μF 2.2pF 499Ω 499Ω 0.1μF 24.9Ω FET PROBE AD8065 VIN 49.9Ω 249Ω 0.1μF RSNUB AD8065 NETWORK ANALYZER S22 1kΩ CLOAD 0.1μF 4.7μF 02916-E-043 4.7μF 02916-E-045 –VEE –VEE Figure 43. G = +2 Figure 45. Output Impedance G = +1 Rev. G | Page 15 of 28 02916-E-044 4.7μF AD8065/AD8066 +VCC 4.7μF VIN 1V p-p +VCC 0.1μF 49.9Ω 24.9Ω 499Ω 499Ω VIN FET PROBE FET PROBE AD8065 49.9Ω 499Ω 499Ω 0.1μF 1kΩ AD8065 0.1μF 1kΩ 4.7μF 02916-E-046 4.7μF 02916-E-048 –VEE –VEE Figure 46. CMRR +VCC 4.7μF Figure 48. Positive PSRR +VCC 4.7μF 0.1μF 0.1μF 499Ω 499Ω 499Ω 2.2pF 499Ω 249Ω AD8065 NETWORK ANALYZER S22 249Ω 976Ω TO SCOPE AD8065 0.1μF 49.9Ω 0.1μF VIN 49.9Ω 4.7μF 02916-E-047 4.7μF 02916-E-049 –VEE –VEE Figure 47. Output Impedance G = +2 Figure 49. Settling Time Rev. G | Page 16 of 28 AD8065/AD8066 +VCC 4.7μF 24.9Ω 0.1μF 24.9Ω 24.9Ω FET PROBE AD8066 +5V 4.7μF 1kΩ 0.1μF RECEIVE SIDE FET PROBE AD8065 1kΩ 49.9Ω 49.9Ω VIN AD8066 0.1μF 1kΩ 4.7μF 02916-E-051 02916-E-050 VIN 1V p-p –5V DRIVE SIDE –VEE Figure 50. Negative PSRR Figure 51. Crosstalk—AD8066 2.2pF 499Ω 499Ω 5V 1.5V 4.7μF 0.1μF FET PROBE 249Ω VIN 49.9Ω 1kΩ 02916-E-052 AD8065 1.5V 1.5V Figure 52. Single Supply Rev. G | Page 17 of 28 AD8065/AD8066 THEORY OF OPERATION The AD8065/AD8066 are voltage feedback operational amplifiers that combine a laser-trimmed JFET input stage with the Analog Devices eXtra Fast Complementary Bipolar (XFCB) process, resulting in an outstanding combination of precision and speed. The supply voltage range is from 5 V to 24 V. The amplifiers feature a patented rail-to-rail output stage capable of driving within 0.5 V of either power supply while sourcing or sinking up to 30 mA. Also featured is a single-supply input stage that handles common-mode signals from below the negative supply to within 3 V of the positive rail. Operation beyond the JFET input range is possible because of an auxiliary bipolar input stage that functions with input voltages up to the positive supply. The amplifiers operate as if they have a rail-to-rail input and exhibit no phase reversal behavior for common-mode voltages within the power supply. With voltage noise of 7 nV/√Hz and −88 dBc distortion for 1 MHz, 2 V p-p signals, the AD8065/AD8066 are a great choice for high resolution data acquisition systems. Their low noise, sub-pA input current, precision offset, and high speed make them superb preamps for fast photodiode applications. The speed and output drive capability of the AD8065/AD8066 also make them useful in video applications. NONINVERTING CLOSED-LOOP FREQUENCY RESPONSE Solving for the transfer function 2 π × f crossover (RG + RF ) VO = VI (RF + RG ) s + 2π × f crossover × RG where fcrossover is the frequency where the amplifier’s open-loop gain equals 0 db At dc VO RF + RG = VI RG Closed-loop −3 dB frequency f −3dB = f crossover × RG RF + RG INVERTING CLOSED-LOOP FREQUENCY RESPONSE −2π × f crossover × RF VO = VI s (RF + RG ) + 2π × f crossover × RG At dc CLOSED-LOOP FREQUENCY RESPONSE The AD8065/AD8066 are classic voltage feedback amplifiers with an open-loop frequency response that can be approximated as the integrator response shown in Figure 53. Basic closed-loop frequency response for inverting and noninverting configurations can be derived from the schematics shown. RF VO R =− F VI RG Closed-loop −3 dB frequency f − 3dB = f crossover × RG R F + RG RF RG VI VE VI RG VE A VO A VO 80 A = (2π × fcrossover)/s OPEN-LOOP GAIN (A) (dB) 60 40 20 fcrossover = 65MHz 0 0.01 0.1 1 FREQUENCY (MHz) 10 100 Figure 53. Open-Loop Gain vs. Frequency and Basic Connections Rev. G | Page 18 of 28 02916-E-053 AD8065/AD8066 The closed-loop bandwidth is inversely proportional to the noise gain of the op amp circuit, (RF + RG )/RG. This simple model is accurate for noise gains above 2. The actual bandwidth of circuits with noise gains at or below 2 are higher than those predicted with this model due to the influence of other poles in the frequency response of the real op amp. RF For the best settling times and the best distortion, the impedances at the AD8065/AD8066 input terminals should be matched. This minimizes nonlinear common-mode capacitive effects that can degrade ac performance. Actual distortion performance depends on a number of variables: • • • • • RG +VOS – VO VI RS Ib – A The closed-loop gain of the application Whether it is inverting or noninverting Amplifier loading Signal frequency and amplitude Board layout Ib+ 02916-E-054 Figure 54. Voltage Feedback Amplifier DC Errors Figure 54 shows a voltage feedback amplifier’s dc errors. For both inverting and noninverting configurations ⎛ R + RF ⎞ ⎛ R + RF ⎞ VO (error ) = I b+ × RS ⎜ G ⎟ − I × R F + VOS ⎜ G ⎟ RG ⎠ b − ⎝ ⎝ RG ⎠ Also see Figure 16 to Figure 20. The lowest distortion is obtained with the AD8065 used in low gain inverting applications, since this eliminates common-mode effects. Higher closed-loop gains result in worse distortion performance. INPUT PROTECTION The inputs of the AD8065/AD8066 are protected with back-toback diodes between the input terminals as well as ESD diodes to either power supply. This results in an input stage with picoamps of input current that can withstand up to 1500 V ESD events (human body model) with no degradation. Excessive power dissipation through the protection devices destroys or degrades the performance of the amplifier. Differential voltages greater than 0.7 V result in an input current of approximately (|V+ − V−| 0.7 V)/RI, where RI is the resistance in series with the inputs. For input voltages beyond the positive supply, the input current is approximately (VI − VCC − 0.7)/RI. Beyond the negative supply, the input current is about (VI − VEE + 0.7)/RI. If the inputs of the amplifier are to be subjected to sustained differential voltages greater than 0.7 V, or to input voltages beyond the amplifier power supply, input current should be limited to 30 mA by an appropriately sized input resistor (RI), as shown in Figure 55. RI > (| V+– V– | – 0.7V) 30mA RI > RI > (VI – VEE – 0.7V) 30mA (VI – VEE + 0.7V) 30mA FOR VI BEYOND SUPPLY VOLTAGES 02916-E-055 The voltage error due to Ib+ and Ib– is minimized if RS = RF || RG (though with the AD8065 input currents at less than 20 pA over temperature, this is likely not a concern). To include commonmode and power supply rejection effects, total VOS can be modeled VOS = VOS nom + Δ VS Δ VCM + PSR CMR VOS nom is the offset voltage specified at nominal conditions, ΔVS is the change in power supply from nominal conditions, PSR is the power supply rejection, ΔVCM is the change in common-mode voltage from nominal conditions, and CMR is the common-mode rejection. WIDEBAND OPERATION Figure 42 through Figure 44 show the circuits used for wideband characterization for gains of +1, +2, and −1. Source impedance at the summing junction (RF || RG) will form a pole in the amplifier’s loop response with the amplifier’s input capacitance of 6.6 pF. This can cause peaking and ringing if the time constant formed is too low. Feedback resistances of 300 Ω to 1 kΩ are recommended, since they will not unduly load down the amplifier and the time constant formed will not be too low. Peaking in the frequency response can be compensated for with a small capacitor (CF) in parallel with the feedback resistor, as illustrated in Figure 12. This shows the effect of different feedback capacitances on the peaking and bandwidth for a noninverting G = +2 amplifier. FOR LARGE | V+ – V– | RI AD8065 VI VO Figure 55. Current-Limiting Resistor Rev. G | Page 19 of 28 AD8065/AD8066 THERMAL CONSIDERATIONS With 24 V power supplies and 6.5 mA quiescent current, the AD8065 dissipates 156 mW with no load. The AD8066 dissipates 312 mW. This can lead to noticeable thermal effects, especially in the small SOT-23-5 (thermal resistance of 160°C/W). VOS temperature drift is trimmed to guarantee a maximum drift of 17 μV/°C, so it can change up to 0.425 mV due to warm-up effects for an AD8065/AD8066 in a SOT-23-5 package on 24 V. Ib increases by a factor of 1.7 for every 10°C rise in temperature. Ib is close to five times higher at 24 V supplies as opposed to a single 5 V supply. Heavy loads increase power dissipation and raise the chip junction temperature as described in the Maximum Power Dissipation section. Care should be taken to not exceed the rated power dissipation of the package. The circuit is arranged such that when the input commonmode voltage exceeds a certain threshold, the input JFET pair’s bias current turns OFF, and the bias current of an auxiliary NPN pair turns ON, taking over control of the amplifier. When the input common-mode voltage returns to a viable operating value, the FET stage turns back ON, the NPN stage turns OFF, and normal operation resumes. The NPN pair can sustain operation with the input voltage up to the positive supply, so this is a pseudo rail-to-rail input stage. For operation beyond the FET stage’s common-mode limit, the amplifier’s VOS changes to the NPN pair’s offset (mean of 160 μV, standard deviation of 820 μV), and Ib increases to the NPN pair’s base current up to 45 μA (see Figure 32). Switchback, or recovery time, is about 100 ns, see Figure 27. The output transistors of the rail-to-rail output stage have circuitry to limit the extent of their saturation when the output is overdriven. This helps output recovery time. Output recovery from a 0.5 V output overdrive on a ±5 V supply is shown in Figure 24. INPUT AND OUTPUT OVERLOAD BEHAVIOR The AD8065/AD8066 have internal circuitry to guard against phase reversal due to overdriving the input stage. A simplified schematic of the input stage, including the input-protection diodes and antiphase reversal circuitry, is shown in Figure 56. VCC R1 R5 TO REST OF AMP Q2 Q5 VTHRESHOLD VBIAS D1 R3 Q1 VN D3 Q3 S R4 D2 Q4 R7 S Q6 D4 VP R6 R2 R8 Q7 –VEE Figure 56. Simplified Input Stage Rev. G | Page 20 of 28 02916-E-056 IT1 IT2 AD8065/AD8066 LAYOUT, GROUNDING, AND BYPASSING CONSIDERATIONS POWER SUPPLY BYPASSING Power supply pins are actually inputs and care must be taken so that a noise-free stable dc voltage is applied. The purpose of bypass capacitors is to create low impedances from the supply to ground at all frequencies, thereby shunting or filtering most of the noise. Decoupling schemes are designed to minimize the bypassing impedance at all frequencies with a parallel combination of capacitors. 0.1 μF (X7R or NPO) chip capacitors are critical and should be as close as possible to the amplifier package. The 4.7 μF tantalum capacitor is less critical for high frequency bypassing, and, in most cases, only one is needed per board at the supply inputs. GROUNDING A ground plane layer is important in densely packed PC boards to spread the current minimizing parasitic inductances. However, an understanding of where the current flows in a circuit is critical to implementing effective high speed circuit design. The length of the current path is directly proportional to the magnitude of parasitic inductances and, therefore, the high frequency impedance of the path. High speed currents in an inductive ground return create unwanted voltage noise. The length of the high frequency bypass capacitor leads is most critical. A parasitic inductance in the bypass grounding works against the low impedance created by the bypass capacitor. Place the ground leads of the bypass capacitors at the same physical location. Because load currents flow from the supplies as well, the ground for the load impedance should be at the same physical location as the bypass capacitor grounds. For the larger value capacitors, which are effective at lower frequencies, the current return path distance is less critical. Rev. G | Page 21 of 28 AD8065/AD8066 LEAKAGE CURRENTS Poor PC board layout, contaminants, and the board insulator material can create leakage currents that are much larger than the input bias current of the AD8065/AD8066. Any voltage differential between the inputs and nearby runs sets up leakage currents through the PC board insulator, for example, 1 V/100 GΩ = 10 pA. Similarly, any contaminants on the board can create significant leakage (skin oils are a common problem). To significantly reduce leakage, put a guard ring (shield) around the inputs and input leads that are driven to the same voltage potential as the inputs. This way there is no voltage potential between the inputs and surrounding area to set up any leakage currents. For the guard ring to be completely effective, it must be driven by a relatively low impedance source and should completely surround the input leads on all sides, above and below, using a multilayer board. Another effect that can cause leakage currents is the charge absorption of the insulator material itself. Minimizing the amount of material between the input leads and the guard ring helps to reduce the absorption. Also, low absorption materials, such as Teflon® or ceramic, could be necessary in some instances. enough. It is recommended that the external passive components connected to the input pins be placed as close as possible to the inputs to avoid parasitic capacitance. The ground and power planes must be kept at a small distance from the input pins on all layers of the board. OUTPUT CAPACITANCE To a lesser extent, parasitic capacitances on the output can cause peaking and ringing of the frequency response. There are two methods to effectively minimize their effect: • As shown in Figure 57, put a small value resistor (RS) in series with the output to isolate the load capacitor from the amp’s output stage. A good value to choose is 20 Ω (see Figure 10). Increase the phase margin with higher noise gains or add a pole with a parallel resistor and capacitor from −IN to the output. • AD8065 VI RS = 20Ω CL VO 02916-E-057 INPUT CAPACITANCE Along with bypassing and ground, high speed amplifiers can be sensitive to parasitic capacitance between the inputs and ground. A few pF of capacitance reduces the input impedance at high frequencies, in turn increasing the amplifier’s gain, causing peaking of the frequency response or even oscillations, if severe Figure 57. Output Isolation Resistor CF RF IPHOTO CS RSH = 1011Ω CD CM CM VB RF VO Figure 58. Wideband Photodiode Preamp Rev. G | Page 22 of 28 02916-E-058 CF + CS AD8065/AD8066 INPUT-TO-OUTPUT COUPLING To minimize capacitive coupling between the inputs and output, the output signal traces should not be parallel with the inputs. bandwidth in half results in a flat frequency response with about 5% transient overshoot. The preamp’s output noise over frequency is shown in Figure 59. 1 2π RF (CF + CS + CM + 2CD) 1 2π RFCF WIDEBAND PHOTODIODE PREAMP Figure 58 shows an I/V converter with an electrical model of a photodiode. The basic transfer function is VOUT VOLTAGE NOISE (nV/ Hz) f1 = I PHOTO × RF = 1 + sC F RF f2 = f3 = fCR (CS + CM + 2CD + CF) /CF where IPHOTO is the output current of the photodiode, and the parallel combination of RF and CF sets the signal bandwidth. The stable bandwidth attainable with this preamp is a function of RF, the gain bandwidth product of the amplifier, and the total capacitance at the amplifier’s summing junction, including CS and the amplifier input capacitance. RF and the total capacitance produce a pole in the amplifier’s loop transmission that can result in peaking and instability. Adding CF creates a 0 in the loop transmission that compensates for the pole’s effect and reduces the signal bandwidth. It can be shown that the signal bandwidth resulting in a 45° phase margin (f(45)) is defined by f ( 45 ) = f CR 2π × RF × C S RF NOISE f2 f1 VEN (CF + CS + CM + 2CD)/CF f3 NOISE DUE TO AMPLIFIER FREQUENCY (Hz) Figure 59. Photodiode Voltage Noise Contributions where fCR is the amplifier crossover frequency, RF is the feedback resistor, and CS is the total capacitance at the amplifier summing junction (amplifier + photodiode + board parasitics). The value of CF that produces f(45) can be shown to be CF = CS 2π × RF × f CR The pole in the loop transmission translates to a 0 in the amplifier’s noise gain, leading to an amplification of the input voltage noise over frequency. The loop transmission 0 introduced by CF limits the amplification. The noise gain bandwidth extends past the preamp signal bandwidth and is eventually rolled off by the decreasing loop gain of the amplifier. Keeping the input terminal impedances matched is recommended to eliminate common-mode noise peaking effects, which adds to the output noise. Integrating the square of the output voltage noise spectral density over frequency and then taking the square root allows users to obtain the total rms output noise of the preamp. Table 5 summarizes approximations for the amplifier and feedback and source resistances. Noise components for an example preamp with RF = 50 kΩ, CS = 15 pF, and CF = 2 pF (bandwidth of about 1.6 MHz) are also listed. The frequency response in this case shows about 2 dB of peaking and 15% overshoot. Doubling CF and cutting the Table 5. RMS Noise Contributions of Photodiode Preamp Contributor RF (×2) Amp to f1 Amp (f2 – f1) Expression RMS Noise with RF = 50 kΩ, CS = 15 pF, CS = 15 pF 64.5 μV 2.4 μV 2 × 4 kT × RF × f 2 × 1.57 VEN × VEN × VEN × f1 C S + C M + C F + 2C D × CF C S + C M + C D + 2C F × CF f 2 − f1 f 3 × 1.57 31 μV Amp to (past f2) 260 μV 270 μV (Total) Rev. G | Page 23 of 28 02916-E-059 VEN AD8065/AD8066 VCC 4.7μ F 0.1μ F RS1 VN 1/2 AD8066 0.1μ F VEE 4.7μ F 2.2pF R2 500Ω VCC 4.7μ F R1 500Ω RF = 500Ω 0.1μ F AD8065 4.7μ F VO RG R3 RF = 500Ω VCC 4.7μ F R4 500Ω 500Ω 0.1μ F VEE 0.1μ F 1/2 RS2 VP 2.2pF AD8066 4.7μ F VEE Figure 60. High Speed Instrumentation Amplifier HIGH SPEED JFET INPUT INSTRUMENTATION AMPLIFIER Figure 60 shows an example of a high speed instrumentation amplifier with high input impedance using the AD8065/AD8066. The dc transfer function is VIDEO BUFFER The output current capability and speed of the AD8065 make it useful as a video buffer, shown in Figure 61. The G = +2 configuration compensates for the voltage division of the signal due to the signal termination. This buffer maintains 0.1 dB flatness for signals up to 7 MHz, from low amplitudes up to 2 V p-p (see Figure 7). Differential gain and phase have been measured to be 0.02% and 0.028°, respectively, at ±5 V supplies. +VS 0.1μ F 4.7μ F 75Ω AD8065 0.1μ F –VS 2.2pF 4.7μ F 75Ω + VO – ⎛ 1 + 1000 ⎞ VOUT = (VN − VP ) ⎜ ⎟ ⎝ RG ⎠ For G = +1, it is recommended that the feedback resistors for the two preamps be set to a low value (for instance 50 Ω for 50 Ω source impedance). The bandwidth for G = +1 is 50 MHz. For higher gains, the bandwidth is set by the preamp, equaling Inamp−3dB = ( f CR × RG )/ (2 × RF ) Common-mode rejection of the in-amp will be primarily determined by the match of the resistor ratios R1:R2 to R3:R4. It can be estimated 249Ω + VI – The summing junction impedance for the preamps is equal to RF || 0.5(RG). This is the value to be used for matching purposes. Figure 61. Video Buffer Rev. G | Page 24 of 28 02916-E-061 (δ1 − δ2 ) VO = VCM (1 + δ1) δ2 499Ω 499Ω 02916-E-060 0.1μ F AD8065/AD8066 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 5 4 3.20 3.00 2.80 4.00 (0.1574) 3.80 (0.1497) 1 6.20 (0.2440) 5.80 (0.2284) 3.20 3.00 2.80 8 5 1 5.15 4.90 4.65 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 1.75 (0.0688) 1.35 (0.0532) 0.50 (0.0196) × 45° 0.25 (0.0099) PIN 1 4 0.65 BSC 0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE 8° 0.25 (0.0098) 0° 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) 0.95 0.85 0.75 0.15 0.00 0.38 0.22 1.10 MAX 8° 0° 0.80 0.60 0.40 COMPLIANT TO JEDEC STANDARDS MS-012AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN 0.23 0.08 SEATING PLANE COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 62. 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 2.90 BSC Figure 64. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters 5 4 1.60 BSC 1 2 3 2.80 BSC PIN 1 0.95 BSC 1.30 1.15 0.90 1.90 BSC 1.45 MAX 0.22 0.08 10° 5° 0° 0.60 0.45 0.30 0.15 MAX 0.50 0.30 SEATING PLANE COMPLIANT TO JEDEC STANDARDS MO-178-AA Figure 63. 5-Lead Small Outline Transistor Package [SOT-23] (RT-5) Dimensions shown in millimeters Rev. G | Page 25 of 28 AD8065/AD8066 ORDERING GUIDE Model AD8065AR AD8065AR-REEL AD8065AR-REEL7 AD8065ARZ 1 AD8065ARZ-REEL1 AD8065ARZ-REEL71 AD8065ART-REEL AD8065ART-R2 AD8065ART-REEL7 AD8065ARTZ-R2 2 AD8065ARTZ-REEL2 AD8065ARTZ-REEL72 AD8066AR AD8066AR-REEL AD8066AR-REEL7 AD8066ARZ1 AD8066ARZ-RL1 AD8066ARZ-R71 AD8066ARM AD8066ARM-REEL AD8066ARM-REEL7 AD8066ARMZ1 AD8066ARMZ-REEL71 1 2 Temperature Range −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C −40°C to +85°C Package Description 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 5-Lead SOT-23 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead SOIC 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP 8-Lead MSOP Package Option R-8 R-8 R-8 R-8 R-8 R-8 RT-5 RT-5 RT-5 RT-5 RT-5 RT-5 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 RM-8 RM-8 RM-8 Branding HRA HRA HRA HRA # HRA # HRA # H1B H1B H1B H7C H7C Z = Pb-free part. Z = Pb-free part, # denotes lead-free product, may be top or bottom marked. Rev. G | Page 26 of 28 AD8065/AD8066 NOTES Rev. G | Page 27 of 28 AD8065/AD8066 NOTES ©2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C02916-0-1/06(G) Rev. G | Page 28 of 28