Dual 600 MHz, 50 mW Current Feedback Amplifier AD8002 Data Sheet PIN CONNECTION BLOCK DIAGRAM Excellent video specifications (RL = 150 , G = +2) Gain flatness: 0.1 dB to 60 MHz Differential gain error: 0.01% Differential phase error: 0.02 Low power Maximum power supply current (50 mW): 5.0 mA/amp High speed and fast settling -3 dB bandwidth (G = +1): 600 MHz -3 dB bandwidth (G = +2): 500 MHz Slew rate: 1200 V/s Settling time to 0.1%: 16 ns Low distortion THD at fC = 5 MHz: -65 dBc Third-order intercept at f1 = 10 MHz: 33 dBm SFDR at f = 5 MHz: -66 dB Crosstalk at f = 5 MHz: -60 dB High output drive Over 70 mA output current Drives up to eight back terminated 75 loads (four loads/side) while maintaining good differential gain/phase performance (0.01%/0.17) Available in 8-lead SOIC and MSOP packages APPLICATIONS Analog-to-digital drivers Video line drivers Differential line drivers Professional cameras Video switchers Special effects RF receivers OUT1 1 -IN1 8 V+ 7 OUT2 2 6 -IN2 +IN1 3 V- 4 AD8002 5 +IN2 01044-001 FEATURES Figure 1. The AD8002 offers a low power of 5.0 mA/amp maximum (VS = 5 V) and can run on a single 12 V power supply, yet is capable of delivering over 70 mA of load current. It is offered in 8-lead SOIC and MSOP packages. These features make this amplifier ideal for portable and battery-powered applications where size and power are critical. The bandwidth of 600 MHz along with 1200 V/s of slew rate make the AD8002 useful in many general-purpose high speed applications where dual power supplies of up to 6 V and single supplies from 6 V to 12 V are needed. The AD8002 is available in the industrial temperature range of -40C to +85C. GENERAL DESCRIPTION Rev. E SIDE 1 G = +2 1V STEP SIDE 2 200mV 5ns 01044-003 The AD8002 is a dual, low power, high speed amplifier designed to operate on 5 V supplies. The AD8002 features unique transimpedance linearization circuitry, which allows the AD8002 to drive video loads with excellent differential gain and phase performance on only 50 mW of power per amplifier. The AD8002 is a current feedback amplifier and features gain flatness of 0.1 dB to 60 MHz while offering differential gain and phase error of 0.01% and 0.02, which makes the AD8002 ideal for professional video electronics such as cameras and video switchers. Additionally, the low distortion and fast settling of the AD8002 make it ideal for buffer high speed analog-todigital converters (ADCs). Figure 2. 1 V Step Response, G = +1 Document Feedback 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 (c)2015 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com AD8002 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Choice of Feedback and Gain Resistors .................................. 14 Applications ....................................................................................... 1 Printed Circuit Board (PCB) Layout Considerations ........... 14 General Description ......................................................................... 1 Power Supply Bypassing ............................................................ 14 Pin Connection Block Diagram ..................................................... 1 DC Errors and Noise.................................................................. 14 Revision History ............................................................................... 2 Driving Capacitive Loads .......................................................... 15 Specifications..................................................................................... 3 Communications ........................................................................ 15 Absolute Maximum Ratings ............................................................ 5 Operation as a Video Line Driver ............................................ 15 Maximum Power Dissipation ..................................................... 5 Driving ADCs ............................................................................. 16 ESD Caution .................................................................................. 5 Single-Ended-to-Differential Driver Using an AD8002 ....... 16 Pin Configurations and Function Descriptions ........................... 6 Applications Information .............................................................. 18 Typical Performance Characteristics ............................................. 7 Layout Considerations ............................................................... 18 Test Circuits ..................................................................................... 13 Outline Dimensions ....................................................................... 21 Theory of Operation ...................................................................... 14 Ordering Guide .......................................................................... 21 REVISION HISTORY 8/15--Rev. D to Rev. E Updated Format .................................................................. Universal Deleted 8-Lead Plastic DIP ............................................... Universal Changes to Features Section............................................................ 1 Deleted Figure 1; Renumbered Sequentially ................................. 1 Changes to Table 1 ............................................................................ 3 Change to Figure 3 ........................................................................... 5 Added Pin Configurations and Function Descriptions Section, Figure 4, Figure 5, and Table 3; Renumbered Sequentially ......... 6 Change to Figure 10 ......................................................................... 7 Change to Figure 16 ......................................................................... 8 Change to Figure ............................................................................... 9 Change to Figure 34 ....................................................................... 11 Change to Figure 32 ....................................................................... 11 Added Test Circuits Section and Figure 42 to Figure 47 ........... 13 Change to Theory of Operation Section ..................................... 14 Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 21 4/01--Rev. C to Rev. D Max Ratings Changed ...................................................................... 3 Rev. E | Page 2 of 21 Data Sheet AD8002 SPECIFICATIONS At TA = 25C, VS = 5 V, RL = 100 , RC1 = 75 , unless otherwise noted. Table 1. Parameter DYNAMIC PERFORMANCE -3 dB Small Signal Bandwidth R Package RM Package Bandwidth for 0.1 dB Flatness R Package RM Package Slew Rate Settling Time to 0.1% Rise and Fall Time NOISE/HARMONIC PERFORMANCE Total Harmonic Distortion (THD) Crosstalk (Output to Output) Input Voltage Noise Input Current Noise Differential Gain Error Differential Phase Error Third-Order Intercept 1 dB Gain Compression Spurious-Free Dynamic Range (SFDR) DC PERFORMANCE Input Offset Voltage Test Conditions/Comments Min MHz MHz MHz MHz G = +2, RF = 681 G = +2, RF = 681 G = +2, VOUT = 2 V step G = -1, VOUT = 2 V step G = +2, VOUT = 2 V step G = +2, VOUT = 2 V step, RF = 750 90 60 700 1200 16 2.4 MHz MHz V/s V/s ns ns fC = 5 MHz, VOUT = 2 V p-p, G = +2, RL = 100 f = 5 MHz, G = +2 f = 10 kHz, RC = 0 f = 10 kHz, +IN1,+IN2 f = 10 kHz, -IN1, -IN2 NTSC, G = +2, RL = 150 NTSC, G = +2, RL = 150 f1= 10 MHz f = 10 MHz f = 5 MHz -65 -60 2.0 2.0 18 0.01 0.02 33 14 -66 dBc dB nV/Hz pA/Hz pA/Hz % Degrees dBm dBm dB -25 -35 -6.0 -10 250 175 TMIN to TMAX Input Bias Current (+IN1, +IN2) Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio Offset Voltage Input Current (-IN1, -IN2) Input Current (+IN1, +IN2) OUTPUT CHARACTERISTICS Output Voltage Swing Output Current2 Short-Circuit Current2 Unit 500 600 500 600 Offset Drift Input Bias Current (-IN1, -IN2) INPUT CHARACTERISTICS Input Resistance Max G = +2, RF = 681 G = +1, RF = 953 G = +2, RF = 681 G = +1, RF = 1 k TMIN to TMAX Open-Loop Transresistance Typ TMIN to TMAX VOUT = 2.5 V TMIN to TMAX +IN1, +IN2 -IN1, -IN2 +IN1, +IN2 2.0 2.0 10 +5.0 +3.0 6 9 +25 +35 +6.0 +10 900 10 50 1.5 3.2 VCM = 2.5 V VCM = 2.5 V, TMIN to TMAX VCM = 2.5 V, TMIN to TMAX 49 RL = 150 2.7 85 Rev. E | Page 3 of 21 54 0.3 0.2 3.1 70 110 mV mV V/C A A A A k k M pF V 1.0 0.9 dB A/V A/V V mA mA AD8002 Parameter POWER SUPPLY Operating Range Quiescent Current/Both Amplifiers Power Supply Rejection Ratio Input Current (-IN1, -IN2) Input Current (+IN1, +IN2) 1 2 Data Sheet Test Conditions/Comments Min Typ 3.0 TMIN to TMAX +VS = +4 V to +6 V, -VS = -5 V -VS = -4 V to -6 V, +VS = +5 V TMIN to TMAX TMIN to TMAX 60 49 10.0 75 56 0.5 0.1 RC is recommended to reduce peaking and minimize input reflections at frequencies above 300 MHz. However, RC is not required. Output current is limited by the maximum power dissipation in the package. See Figure 3. Rev. E | Page 4 of 21 Max Unit 6.0 11.5 V mA dB dB A/V A/V 2.5 0.5 Data Sheet AD8002 ABSOLUTE MAXIMUM RATINGS Storage Temperature Range Operating Temperature Range Lead Temperature (Soldering 10 sec) 1 Rating 13.2 V 0.9 W 0.6 W VS 1.2 V Observe power derating curves -65C to +125C -40C to +85C 300C 2.0 TJ = 150C Specification is for device in free air: 8-lead SOIC: JA = 155C/W. 8-lead MSOP: JA = 200C/W. Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. 8-LEAD SOIC PACKAGE 1.5 1.0 0.5 8-LEAD MSOP PACKAGE 0 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 AMBIENT TEMPERATURE (C) Figure 3. Maximum Power Dissipation vs. Ambient Temperature ESD CAUTION MAXIMUM POWER DISSIPATION The maximum power that can be safely dissipated by the AD8002 is limited by the associated rise in junction temperature. The maximum safe junction temperature for plastic encapsulated devices is determined by the glass transition temperature of the plastic, approximately 150C. Exceeding this limit temporarily may cause a shift in parametric performance due to a change in the stresses exerted on the die by the package. Exceeding a junction temperature of 175C for an extended period can result in device failure. Rev. E | Page 5 of 21 01044-004 Parameter Supply Voltage Internal Power Dissipation1 SOIC (R) MSOP (RM) Input Common-Mode Voltage Differential Input Voltage Output Short-Circuit Duration Although the AD8002 is internally short-circuit protected, this may not be sufficient to guarantee that the maximum junction temperature (150C) is not exceeded under all conditions. To ensure proper operation, it is necessary to observe the maximum power derating curves. MAXIMUM POWER DISSIPATION (W) Table 2. AD8002 Data Sheet -IN1 2 +IN1 3 AD8002 8 V+ 7 OUT2 TOP VIEW (Not to Scale) 6 -IN2 V- 4 5 +IN2 OUT1 1 01044-100 OUT1 1 +IN1 3 TOP VIEW (Not to Scale) 8 V+ 7 OUT2 6 -IN2 5 +IN2 Figure 5. 8-Lead MSOP Table 3. Pin Function Descriptions Mnemonic OUT1 -IN1 +IN1 V- +IN2 -IN2 OUT2 V+ AD8002 V- 4 Figure 4. 8-Lead SOIC Pin No. 1 2 3 4 5 6 7 8 -IN1 2 Description Output 1 Inverting Input 1 Noninverting Input 1 VEE or Negative Supply Noninverting Input 2 Inverting Input 2 Output 2 VCC or Positive Supply Rev. E | Page 6 of 21 01044-101 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS Data Sheet AD8002 TYPICAL PERFORMANCE CHARACTERISTICS SIDE 1 SIDE 1 G = +1 100mV STEP G = +2 100mV STEP SIDE 2 5ns 01044-008 20mV 01044-005 SIDE 2 20mV 5ns Figure 9. 1 V Step Response, G = +2 Figure 6. 100 mV Step Response, G = +1 5ns -2 -3 0.1 SIDE 1 0 -4 -5 -0.1 SIDE 2 -0.2 01044-006 SIDE 2 -1 SIDE 2 -6 -0.3 -7 -0.4 -8 -0.5 1M -9 1G 10M 100M FREQUENCY (Hz) 01044-009 G = +1 1V STEP 20mV G = +2 RL = 100 VIN = 50mV NORMALIZED FLATNESS (dB) SIDE 1 NORMALIZED FREQUENCY RESPONSE (dB) 1 0 SIDE 1 Figure 10. Frequency Response and Flatness, G = +2 (See Figure 41) Figure 7. 1 V Step Response, G = +1 -50 G = +2 RL = 100 -60 G = +2 100mV STEP DISTORTION (dBc) SIDE 1 -70 SECOND HARMONIC -80 THIRD HARMONIC -90 -100 5ns -110 10k 100k 1M FREQUENCY (Hz) 10M Figure 11. Distortion vs. Frequency, G = +2, RL = 100 Figure 8. 100 mV Step Response, G = +2 Rev. E | Page 7 of 21 100M 01044-010 20mV 01044-007 SIDE 2 AD8002 Data Sheet -60 -80 SECOND HARMONIC THIRD HARMONIC -100 100k 1M FREQUENCY (Hz) -0.01 10M 100M G = +2 RF = 750 NTSC 0.08 0.06 0.04 1 BACK TERMINATED LOAD (150) 0.02 0 1 2 3 4 5 6 IRE 7 VIN = -4dBV RL = 100 VS = 5.0V G = +2 RF = 750 VIN = 50mV G = +1 RF = 953 RL = 100 1 OUTPUT SIDE 1 9 10 11 SIDE 1 0 -50 SIDE 2 -60 -1 OUTPUT SIDE 2 GAIN (V) CROSSTALK (dB) 8 2 -20 -40 2 BACK TERMINATED LOADS (75) Figure 15. Differential Gain and Differential Phase (per Amplifier) Figure 12. Distortion vs. Frequency, G = +2, RL = 1 k -30 1 BACK TERMINATED LOAD (150) -0.02 01044-011 -110 -120 10k 0 DIFFERENTIAL PHASE (Degrees) -90 2 BACK TERMINATED LOADS (75) 0.01 01044-014 -70 -70 -80 -2 -3 -90 -4 -100 -5 -110 10M FREQUENCY (Hz) 100M -6 1M 10M 100M FREQUENCY (Hz) 01044-015 1M 01044-012 -120 100k 1G Figure 16. Gain vs. Frequency Response, G = +1 (See Figure 42) Figure 13. Crosstalk (Output to Output) vs. Frequency -40 G = +1 RL = 100 VOUT = 2V p-p -50 DISTORTION (dBc) SIDE 1 G = +2 RF = 750 RC = 75 RL = 100 SIDE 2 -60 -70 SECOND HARMONIC -80 THIRD HARMONIC -90 -100 10k SIDE 1: VIN = 0V; 8mV/DIV RTO SIDE 2: 1V STEP RTO; 400mV/DIV 01044-013 5ns 100k 1M FREQUENCY (Hz) 10M 100M Figure 17. Distortion vs. Frequency, G = +1, RL = 100 Figure 14. Pulse Crosstalk, Worst Case, 1 V Step Rev. E | Page 8 of 21 01044-016 DISTORTION (dBc) DIFFERENTIAL GAIN (%) 0.02 G = +2 RL = 1k VOUT = 2V p-p Data Sheet AD8002 -40 45 G = +1 RL = 1k -50 40 VS = 5.0V RL = 100 -60 30 SECOND HARMONIC GAIN (dB) DISTORTION (dBc) 35 -70 THIRD HARMONIC -80 G = +100 RF = 1000 25 20 G = +10 RF = 499 15 10 -90 5 -100 1M FREQUENCY (Hz) 10M 100M 01044-017 100k -5 1M -3 3 -6 0 -9 -3 -12 -6 -15 -9 G = +2 RF = 681 VS = 5V RL = 100 ERROR, (0.05%/DIV) -15 INPUT -18 -24 1M 10M FREQUENCY (Hz) 100M -21 500M 400mV 01044-018 -27 10ns 01044-021 -21 -12 G = +2 2V STEP RF = 750 RC = 75 OUTPUT OUTPUT LEVEL (dBV) 6 -18 1G Figure 21. Frequency Response, G = +10, G = +100 0 Figure 22. Short Term Settling Time Figure 19. Large Signal Frequency Response, G = +2 3.4 RL = 100 G = +1 RF = 1.21 6 3.3 3 RL = 150 3.2 OUTPUT SWING (V) 0 -3 -6 -9 -12 VS = 5V 500M 01044-019 2.6 100M RL = 50 2.8 -18 10M FREQUENCY (Hz) |-VOUT| 2.9 2.7 1M +VOUT 3.0 -15 -21 VS = 5V 3.1 2.5 -55 +VOUT |-VOUT| -35 -15 5 25 45 65 85 105 JUNCTION TEMPERATURE (C) Figure 23. Output Swing vs. Junction Temperature Figure 20. Large Signal Frequency Response, G = +1 (See Figure 43) Rev. E | Page 9 of 21 125 01044-022 9 INPUT/OUTPUT LEVEL (dBV) INPUT LEVEL (dBV) Figure 18. Distortion vs. Frequency, G = +1, RL = 1 k 10M 100M FREQUENCY (Hz) 01044-020 0 -110 10k AD8002 Data Sheet 11.5 5 4 1 0 -1 +IN -2 -3 -55 -35 -15 5 25 45 65 85 JUNCTION TEMPERATURE (C) 105 125 10.5 VS = 5V 10.0 9.5 9.0 -55 -35 -15 5 25 45 65 85 105 125 JUNCTION TEMPERATURE (C) Figure 24. Input Bias Current vs. Junction Temperature 01044-026 TOTAL SUPPLY CURRENT (mA) 2 11.0 01044-023 INPUT BIAS CURRENT (A) -IN 3 Figure 27. Total Supply Current vs. Junction Temperature 120 G = +2 2V STEP RF = 750 RC = 75 RL = 100 SHORT-CIRCUIT CURRENT (mA) 115 ERROR, (0.05%/DIV) OUTPUT INPUT 110 105 100 |SINK ISC| SOURCE ISC 95 90 85 80 2s Figure 25. Long Term Settling Time -35 -15 5 25 45 65 85 JUNCTION TEMPERATURE (C) 105 125 01044-027 400mV 01044-024 75 70 -55 Figure 28. Short-Circuit Current vs. Junction Temperature 100 100 4 DEVICE 1 1 DEVICE 2 0 DEVICE 3 -1 INVERTING CURRENT VS = 5V 10 10 NONINVERTING CURRENT V S = 5V NOISE CURRENT ( pA/Hz) NOISE VOLTAGE (nV/Hz) 2 VOLTAGE NOISE VS = 5V -3 -55 -35 -15 5 25 45 65 85 105 JUNCTION TEMPERATURE (C) 125 Figure 26. Input Offset Voltage vs. Junction Temperature 1 10 100 1k FREQUENCY (Hz) 10k Figure 29. Noise Voltage vs. Frequency Rev. E | Page 10 of 21 1 100k 01044-028 -2 01044-025 INPUT OFFSET VOLTAGE (mV) 3 Data Sheet AD8002 -48 -50.0 -49 -52.5 -PSRR -55.0 -50 -57.5 PSRR (dB) CMRR (dB) -CMRR -51 +CMRR -52 -53 2V SPAN CURVES ARE FOR WORSTCASE CONDITION WHERE ONE SUPPLY IS VARIED WHILE THE OTHER IS HELD CONSTANT. -60.0 -62.5 -65.0 -67.5 -54 -70.0 +PSRR -55 -35 -15 5 25 45 65 85 JUNCTION TEMPERATURE (C) 105 125 -75.0 -55 01044-029 -56 -55 -35 -15 5 25 45 65 85 105 125 JUNCTION TEMPERATURE (C) Figure 30. Common-Mode Rejection Ratio (CMRR) vs. Junction Temperature Figure 33. Power Supply Rejection Ration (PSRR) vs. Junction Temperature 0 RbT = 50 1 -20 RbT = 0 -30 -40 SIDE 1 0.1 -50 VS = 5.0V RL = 100 VIN = 200mV SIDE 2 0.01 100k 100M 1M 10M FREQUENCY (Hz) 1G 01044-030 -60 10k 1M 10M 100M FREQUENCY (Hz) 1G Figure 34. CMRR vs. Frequency (See Figure 45) Figure 31. Output Resistance vs. Frequency 1 -2 0.1 SIDE 1 0.1dB FLATNESS 0 -3 -4 -0.1 -0.3 VS = 5.0V VIN = 50mV G = -1 RL = 100 RF = 549 SIDE 2 SIDE 1 -5 -6 -7 -8 1M G = -1 RF = 576 RG = 576 RC = 50 10M 100M FREQUENCY (Hz) -9 1G SIDE 2 Figure 32. -3 dB Bandwidth vs. Frequency, G = -1 400mV 5ns Figure 35. 2 V Step Response, G = -1 Rev. E | Page 11 of 21 01044-034 -0.2 0 -1 01044-031 NORMALIZED FLATNESS (dB) SIDE 1 SIDE 2 0.2 OUTPUT VOLTAGE (dB) -3dB BANDWIDTH 01044-033 10 -10 RF = 750 RC = 75 VS = 5.0V POWER = 0dBm (223.6mV rms) G = +2 CMRR (dB) OUTPUT RESISTANCE () 100 01044-032 -72.5 AD8002 Data Sheet SIDE 1 SIDE 1 G = -2 2V STEP RF = 549 SIDE 2 SIDE 2 5ns 400mV 5ns 01044-037 20mV 01044-035 G = -1 RF = 576 RG = 576 RC = 50 RL = 100 Figure 38. 2 V Step Response, G = -2 Figure 36. 100 mV Step Response, G = -1 0 -10 VIN = 200mV G = +2 SIDE 1 -20 G = -1 100mV STEP RF = 549 -40 -PSRR SIDE 2 -50 +PSRR -60 -70 -90 60k 100k 1M 10M FREQUENCY (Hz) 100M 400M Figure 37. PSRR vs. Frequency 20mV 5ns Figure 39. 100 mV Step Response, G = -1 Rev. E | Page 12 of 21 01044-038 -80 01044-036 PSRR (dB) -30 Data Sheet AD8002 TEST CIRCUITS 750 953 10F 10F +5V 0.1F 0.1F 750 8 2 PULSE GENERATOR tR/tF = 250ps 75 RL = 100 0.1F 3 AD8002 75 VIN 4 50 2 1 PULSE GENERATOR 10F 01044-039 VIN AD8002 8 -5V 3 RL = 100 4 50 10F tR/tF = 250ps Figure 40. Test Circuit, Gain = +1 1 0.1F 01044-040 +5V -5V Figure 44. Test Circuit, Gain = +2 VIN 604 50 604 681 01044-041 50 RF 681 57.6 154 50 154 0.1F -5V Figure 41. Frequency Response and Flatness Test Circuit (See Figure 10) 01044-044 75 Figure 45. CMRR Test Circuit (See Figure 34) 576 576 50 953 50 54.9 01044-042 50 01044-045 75 50 Figure 42. Frequency Response Test Circuit (See Figure 16) Figure 46. 100 mV Step Response, G = -1 549 274 50 1.21k 50 61.9 01044-043 50 50 Figure 43. Large Signal Frequency Response Test Circuit (See Figure 20) Rev. E | Page 13 of 21 01044-046 75 Figure 47. 100 mV Step Response, G = -2 AD8002 Data Sheet THEORY OF OPERATION PRINTED CIRCUIT BOARD (PCB) LAYOUT CONSIDERATIONS An analysis of the AD8002 can put the operation in familiar terms. The open-loop behavior of the AD8002 is expressed as transimpedance, VOUT/I-INx, or TZ. The open-loop transimpedance behaves just as the open-loop voltage gain of a voltage feedback amplifier, that is, it has a large dc value and decreases at roughly 6 dB/octave in frequency. Because the value of RIN is proportional to 1/gm, the equivalent voltage gain is just TZ x gm, where the gm in question is the transconductance of the input stage. This results in a low openloop input impedance at the inverting input. Using this amplifier as a follower with gain (see Figure 48) basic analysis yields the following result: VOUT TZ (s) =Gx VIN TZ (s) + G x RIN + R1 POWER SUPPLY BYPASSING where: TZ(s) implies the transimpedance as a function of the frequency. G = 1 + R1/R2. RIN = 1/gm 50 . R1 R2 VOUT Adequate power supply bypassing can be critical when optimizing the performance of a high frequency circuit. Inductance in the power supply leads can form resonant circuits that produce peaking in the response of the amplifier. In addition, if large current transients must be delivered to the load, bypass capacitors (typically greater than 1 F) are required to provide the best settling time and lowest distortion. A parallel combination of 4.7 F and 0.1 F is recommended. Some brands of electrolytic capacitors require a small series damping resistor 4.7 for optimum results. DC ERRORS AND NOISE Figure 48. Small Signal Schematic Recognizing that G x RIN << R1 for low gains, the amplifier can be seen to the first-order that the bandwidth for it is independent of gain (G). Considering that additional poles contribute excess phase at high frequencies, there is a minimum feedback resistance below which peaking or oscillation may result. This fact is used to determine the optimum feedback resistance, RF. In practice, parasitic capacitance at the inverting input terminal also adds phase in the feedback loop; thus selecting an optimum value for RF can be difficult. Achieving and maintaining gain flatness of better than 0.1 dB at frequencies above 10 MHz requires careful consideration of several issues discussed in the following sections. CHOICE OF FEEDBACK AND GAIN RESISTORS There are three major noise and offset terms to consider in a current feedback amplifier. For offset errors, refer to Equation 1. For noise error, the terms are root-sum-squared to give a net output error. In Figure 49, the terms are input offset (VIO), which appears at the output multiplied by the noise gain of the circuit (1 + RF/RI), noninverting input current (IBN x RN), also multiplied by the noise gain, and the inverting input current, which when divided between RF and RI and subsequently multiplied by the noise gain, always appears at the output as IBN x RF. The input voltage noise of the AD8002 is a low 2 nV/Hz. At low gains, though, the inverting input current noise times RF is the dominant noise source. Careful layout and device matching contribute to a better offset and drift specifications for the AD8002.Use the typical performance curves in conjunction with Equation 1 to predict the performance of the AD8002 in any application. The fine scale gain flatness varies to some extent with feedback resistance. Therefore, it is recommended that as soon as optimum resistor values are determined, use 1% tolerance values if it is desired to maintain flatness over a wide range of production lots. In addition, resistors of different construction have different associated parasitic capacitance of the characterization. It is not recommended to use leaded components with the AD8002. R VOUT = VIO x 1 + F I BN x RN RI R x 1 + F x I BI x RF (1) RI RF RI RN IBI IBN Figure 49. Output Offset Voltage Rev. E | Page 14 of 21 VOUT 01044-048 VIN 01044-047 RIN As expected for a wideband amplifier, PCB parasitics can affect the overall closed-loop performance. Of concern are stray capacitances at the output and the inverting input nodes. If a ground plane is to be used on the same side of the board as the signal traces, leave a space (5 mm minimum) around the signal lines to minimize coupling. Additionally, make signal lines connecting the feedback and gain resistors short enough so that their associated inductance does not cause high frequency gain errors. Line lengths of less than 5 mm are recommended. If long runs of coaxial cable are being driven, dispersion and loss must be considered. Data Sheet AD8002 DRIVING CAPACITIVE LOADS -45 The AD8002 was designed primarily to drive nonreactive loads. If driving loads with a capacitive component is desired, the best frequency response is obtained by the addition of a small series resistance as shown in Figure 50. THIRD-ORDER IMD (dBc) 909 RSERIES -60 2 f1 - f2 -65 -70 -75 01044-049 CL -80 -8 -7 Figure 50. Driving Capacitive Loads -6 -5 -3 -4 40 30 20 20 2 3 4 5 25 6 75 75 CABLE 750 VOUT 1 75 4.7F + 01044-050 15 CL (pF) 1 The AD8002 has been designed to offer good performance as a video line driver. The important specifications of differential gain (0.01%) and differential phase (0.02) meet the most exacting HDTV demands for driving one video load with each amplifier. The AD8002 also drives four back terminated loads (two each), as shown in Figure 53, with equally impressive performance (0.01%, 0.07). Another important consideration is isolation between loads in a multiple load application. The AD8002 has more than 40 dB of isolation at 5 MHz when driving two 75 back terminated loads. +VS 0 10 0 OPERATION AS A VIDEO LINE DRIVER 750 5 -1 Figure 52. Third-Order IMD vs. Input Power; f1 = 10 MHz, f2 = 12 MHz 10 0 -2 INPUT POWER (dBm) Figure 51 shows the optimum value for RSERIES vs. capacitive load (CL). It is worth noting that the frequency response of the circuit when driving large capacitive loads is dominated by the passive roll-off of RSERIES and CL. RSERIES (V) 2 f2 - f1 0.1F Figure 51. Recommended RSERIES vs. Capacitive Load 8 2 1/2 AD8002 COMMUNICATIONS Distortion is a key specification in communications applications. Intermodulation distortion (IMD) is a measure of the ability of an amplifier to pass complex signals without the generation of spurious harmonics. Third-order products are usually the most problematic because several of them fall near the fundamentals and do not lend themselves to filtering. Theory predicts that the third-order harmonic distortion components increase in power at three times the rate of the fundamental tones. The specification of the third-order intercept as the virtual point where fundamental and harmonic power are equal is one standard measure of distortion performance. Op amps used in closed-loop applications do not always obey this simple theory. Figure 52 shows the AD8002 performance summarized at a gain of +2. Here, the worst third-order products are plotted vs. input power. The third-order intercept of the AD8002 is 33 dBm at 10 MHz. 3 4 75 CABLE 75 VOUT 2 75 0.1F -VS + 5 750 75 CABLE 4.7F VIN Rev. E | Page 15 of 21 1 75 1/2 AD8002 75 75 CABLE VOUT 3 7 75 6 750 75 75 CABLE VOUT 4 75 Figure 53. Video Line Driver 01044-052 RL 500 -55 01044-051 IN G = +2 f1 = 10MHz f2 = 12MHz -50 AD8002 Data Sheet DRIVING ADCs amps, the overall architecture yields a circuit with attributes normally associated with voltage feedback amplifiers, yet offers the speed advantages inherent in current feedback amplifiers. In addition, the gain of the circuit can be changed by varying a single resistor, RF, which is often not possible in a dual op amp differential driver. The AD8002 is well suited for driving high speed analog-todigital converters, such as the AD9058. The AD9058 is a dual, 8-bit, 50 MSPS ADC. In Figure 55, the AD8002 drives the inputs of the AD9058, which are configured for 0 V to 2 V ranges. Bipolar input signals are buffered, amplified (-2x), and offset (by 1.0 V) into the proper input range of the ADC. Using the internal 2 V reference of the AD9058 connected to both ADCs (as shown in Figure 55) reduces the number of external components required to create a complete data acquisition system. The 20 resistors in series with the ADC inputs help the ADCs drive the 10 pF ADC input capacitance. The AD8002 adds only 100 mW to the power consumption, while not limiting the performance of the circuit. CC = 0.5pF TO 1.5pF RF 511 RG 511 VIN OP AMP 1 RA 511 Figure 54. Differential Line Driver 274 6 10pF 50 36 ENCODE -VREF +VS -VREF 5, 9, 22, 24, 37, 41 +5V 0.1F RZ1 AIN D0 (LSB) 18 17 AD8597 0.1F 20k 20k 0.1F 3 43 15 +VINT 14 +VREF 13 1.1k 11 RZ2 AD9058 (J-LEAD) D0 (LSB) 274 28 29 30 50 1/2 AD8002 20 40 74ACT 273 ANALOG IN B 0.5V 31 AIN 32 33 1 8 34 COMP 0.1F D7 (MSB) -VS RZ1, RZ2 = 2,000 SIP (8-PKG) 35 7, 20, 26, 39 0.1F 4,19, 21 8 12 +VREF D7 (MSB) 549 74ACT 273 16 2 -2V 25, 27, 42 Figure 55. AD8002 Driving a Dual ADC Rev. E | Page 16 of 21 -5V CLOCK 1N4001 01044-053 8 38 1.1k 1k 74ACT04 10 20 OUTPUT 2 OP AMP 2 ENCODE 1/2 AD8002 50 1/2 AD8002 ENCODE 50 RB 511 RA 511 01044-054 RB 511 The two halves of an AD8002 can be configured to create a single-ended-to-differential high speed driver with a -3 dB bandwidth in excess of 200 MHz, as shown in Figure 54. Although the individual op amps are each current feedback op ANALOG IN A 0.5V OUTPUT 1 AD8002 SINGLE-ENDED-TO-DIFFERENTIAL DRIVER USING AN AD8002 549 50 1/2 Data Sheet AD8002 The current feedback nature of the op amps, in addition to enabling the wide bandwidth, provides an output drive of more than 3 V p-p into a 20 load for each output at 20 MHz. Conversely, the voltage feedback nature provides symmetrical high impedance inputs and allows the use of reactive components in the feedback network. The resulting architecture offers several advantages. First, the gain can be changed by changing a single resistor. Changing either RF or RG changes the gain as in an inverting op amp circuit. For most types of differential circuits, more than one resistor must be changed to change gain and still maintain good common-mode rejection (CMR). The circuit consists of the two op amps, each configured as a unity-gain follower by the 511 RA feedback resistors between the output and inverting input of each op amp. The output of each op amp has a 511 RB resistor to the inverting input of the other op amp. Thus, each output drives the other op amp through a unity-gain inverter configuration. By connecting the two amplifiers as cross-coupled inverters, the outputs of the amplifiers are freed to be equal and opposite, assuring zero output common-mode voltage. Reactive elements can be used in the feedback network. This is in contrast to current feedback amplifiers that restrict the use of reactive elements in the feedback op amp. The circuit described requires about 0.9 pF of capacitance in shunt across RF to optimize peaking and realize a -3 dB bandwidth of more than 200 MHz. Looking at this configuration overall, there are two high impedance inputs (the +IN1, +IN2 of each op amp), two low impedance outputs, and a high open-loop gain. The two noninverting inputs and the output of the Op Amp 2 structure looks like a voltage feedback op amp having two symmetrical, high impedance inputs and one output. The +IN1, +IN2 to Op Amp 2 is the noninverting input (it has the same polarity as OUT2) and the +IN1, +IN2 to Op Amp 1 is the inverting input (opposite polarity of Output 2). The shunt capacitor type selection is also critical. A good microwave type chip capacitor with high Q was found to yield best performance. The device selected for this circuit was a Murata Erie MA280R9B. The distortion was measured at 20 MHz with a 3 V p-p input and a 100 load on each output. For OUT1, the distortion is -37 dBc and -41 dBc for the second and third harmonics, respectively. For OUT2, the second harmonic is -35 dBc and the third harmonic is -43 dBc. With a feedback resistor, RF, an input resistor, RG, and the grounding of the +IN1, +IN2 of Op Amp 2, a feedback amplifier is formed. This configuration is similar to a voltage feedback amplifier in an inverting configuration if only OUT2 is considered. The addition of OUT1 makes the amplifier a differential output. 6 CC = 0.9pF 4 2 0 OUTPUT (dB) Using this circuit configuration, the common-mode signal of the outputs is reduced. If one output increases slightly, the negative input to the other op amp drives its output slightly lower and thus preserves the symmetry of the complementary outputs, which reduces the common-mode signal. The commonmode output signal was measured as -50 dB at 1 MHz. The peaking exhibited by the circuit is very sensitive to the value of this capacitor. Parasitics in the board layout on the order of tenths of picofarads influences the frequency response and the value required for the feedback capacitor, thus a good layout is essential. -2 -4 -6 OUT+ -8 -10 OUT- The differential gain of this circuit is -14 1M R R G = F x 1 + A RG RB 10M 100M FREQUENCY (Hz) Figure 56. Differential Driver Frequency Response where: RF/RG is the gain of the overall op amp configuration and is the same as for an inverting op amp except for the polarity. If OUT1 is used as the output reference, the gain is positive. 1 + RA/RB is the noise gain of each individual op amp in its noninverting configuration. Rev. E | Page 17 of 21 1G 01044-055 -12 AD8002 Data Sheet APPLICATIONS INFORMATION LAYOUT CONSIDERATIONS RF The specified high speed performance of the AD8002 requires careful attention to board layout and component selection. Proper RF design techniques and low parasitic component selection are mandatory. +VS RG IN RBT OUT RS Use a ground plane to cover all unused portions of the component side of the board to provide a low impedance ground path. Remove the ground plane from the area near the input pins to reduce stray capacitance. 01044-056 RT -VS Figure 57. Inverting Configuration Use chip capacitors for supply bypassing (see Figure 58). Connect one end to the ground plane and the other within inch of each power pin. Connect an additional large tantalum electrolytic capacitor (4.7 F to 10 F) in parallel, but not necessarily so close, to supply current for fast, large signal changes at the output. C1 0.1F C3 10F C2 0.1F C4 10F -VS 01044-057 +VS Figure 58. Supply Bypassing RF Locate the feedback resistor close to the inverting input pin to keep the stray capacitance at this node to a minimum. Capacitance variations of less than 1 pF at the inverting input significantly affects high speed performance. +VS RG RBT OUT RC RT Use stripline design techniques for long signal traces (greater than about 1 inch). Design these with a characteristic impedance of 50 or 75 and ensure they are properly terminated at each end. 01044-058 IN -VS Figure 59. Noninverting Configuration Table 4 and Table 5 show the recommended component values. Table 4. AD8002AR (SOIC) Recommended Component Values1 Component RF RG RBT (Nominal) RC2 RS RT (Nominal) Small Signal Bandwidth 0.1 dB Flatness 1 2 -10 499 49.9 49.9 N/A 49.9 N/A 250 50 -2 499 249 49.9 N/A 49.9 61.9 410 100 -1 549 549 49.9 N/A 49.9 54.9 410 100 Gain +1 953 N/A 49.9 75 N/A 49.9 600 35 +2 681 681 49.9 75 N/A 49.9 500 90 +10 499 54.9 49.9 0 N/A 49.9 170 24 +100 1000 10 49.9 0 N/A 49.9 17 3 Unit MHz MHz +100 1000 10 49.9 0 N/A 49.9 19 3 Unit MHz MHz N/A means not applicable RC is recommended to reduce peaking, and minimizes input reflections at frequencies above 300 MHz. However, RC is not required. Table 5. AD8002ARM (MSOP) Recommended Component Values1 Component RF RG RBT (Nominal) RC2 RS RT (Nominal) Small Signal Bandwidth 0.1 dB Flatness 1 2 -10 499 49.9 49.9 N/A 49.9 N/A 270 60 -2 499 249 49.9 N/A 49.9 61.9 400 100 -1 590 590 49.9 N/A 49.9 49.9 410 100 Gain +1 1000 N/A 49.9 75 N/A 49.9 600 35 +2 681 681 49.9 75 N/A 49.9 450 70 +10 499 54.9 49.9 0 N/A 49.9 170 35 N/A means not applicable RC is recommended to reduce peaking, and minimizes input reflections at frequencies above 300 MHz. However, RC is not required. Rev. E | Page 18 of 21 AD8002 01044-062 01044-059 Data Sheet Figure 60. Inverter SOIC Board Layout (Silkscreen) 01044-060 01044-063 Figure 63. Noninverter MSOP Board Layout (Silkscreen) Figure 64. Inverter SOIC Board Layout (Component Layer) 01044-061 01044-064 Figure 61. Noninverter SOIC Board Layout (Silkscreen) Figure 62. Inverter MSOP Board Layout (Silkscreen) Figure 65. Noninverter SOIC Board Layout (Component Layer) Rev. E | Page 19 of 21 Data Sheet 01044-068 01044-065 AD8002 Figure 66. Inverter MSOP Board Layout (Component Layer) 01044-069 01044-066 Figure 69. Noninverter SOIC Board Layout (Solder Side) (Looking Through the Board) Figure 67. Noninverter MSOP Board Layout (Component Layer) 01044-070 01044-067 Figure 70. Inverter MSOP Board Layout (Solder Side) (Looking Through the Board) Figure 68. Inverter SOIC Board Layout (Solder Side) (Looking Through the Board) Figure 71. Noninverter MSOP Board Layout (Solder Side) (Looking Through the Board) Rev. E | Page 20 of 21 Data Sheet AD8002 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 4.00 (0.1574) 3.80 (0.1497) 5 1 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) COPLANARITY 0.10 SEATING PLANE 0.50 (0.0196) 0.25 (0.0099) 45 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 012407-A COMPLIANT TO JEDEC STANDARDS MS-012-AA 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. Figure 72. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15 MAX 1.10 MAX 0.40 0.25 6 0 0.23 0.09 0.80 0.55 0.40 COMPLIANT TO JEDEC STANDARDS MO-187-AA 10-07-2009-B 0.15 0.05 COPLANARITY 0.10 Figure 73. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters ORDERING GUIDE Model1 AD8002ARZ AD8002ARZ-R7 AD8002ARMZ AD8002ARMZ-REEL AD8002ARMZ-REEL7 AD8002AR-EBZ AD8002ARM-EBZ 1 Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 8-Lead Standard Small Outline Package [SOIC_N] 8-Lead Standard Small Outline Package [SOIC_N], 7" Reel 8-Lead Mini Small Outline Package [MSOP] 8-Lead Mini Small Outline Package [MSOP], 13" Reel 8-Lead Mini Small Outline Package [MSOP], 7" Reel Evaluation Board for 8-Lead SOIC Evaluation Board for 8-Lead MSOP Z = RoHS Compliant Part. (c)2015 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D01044-0-8/15(E) Rev. E | Page 21 of 21 Package Option R-8 R-8 RM-8 RM-8 RM-8 Branding Code HFA HFA HFA Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Analog Devices Inc.: AD8002AR-EBZ AD8002ARM-EBZ