a 270 MHz, 400 A Current Feedback Amplifier AD8005 FUNCTIONAL BLOCK DIAGRAM FEATURES Ultralow Power 400 A Power Supply Current (4 mW on 5 VS) Specified for Single Supply Operation High Speed 270 MHz, -3 dB Bandwidth (G = +1) 170 MHz, -3 dB Bandwidth (G = +2) 280 V/s Slew Rate (G = +2) 28 ns Settling Time to 0.1%, 2 V Step (G = +2) Low Distortion/Noise -63 dBc @ 1 MHz, V O = 2 V p-p -50 dBc @ 10 MHz, VO = 2 V p-p 4.0 nV/Hz Input Voltage Noise @ 10 MHz Good Video Specifications (RL = 1 k, G = +2) Gain Flatness 0.1 dB to 30 MHz 0.11% Differential Gain Error 0.4 Differential Phase Error 8-Lead Plastic DIP and SOIC NC 1 PRODUCT DESCRIPTION The AD8005 is an ultralow power, high-speed amplifier with a wide signal bandwidth of 170 MHz and slew rate of 280 V/s. This performance is achieved while consuming only 400 A of quiescent supply current. These features increase the operating time of high-speed battery-powered systems without reducing dynamic performance. 6 OUT -VS 4 5 NC 5-Lead SOT-23 5 +VS OUT 1 -VS 2 +IN 4 -IN 3 The current feedback design results in gain flatness of 0.1 dB to 30 MHz while offering differential gain and phase errors of 0.11% and 0.4. Harmonic distortion is low over a wide bandwidth with THDs of -63 dBc at 1 MHz and -50 dBc at 10 MHz. Ideal features for a signal conditioning amplifier or buffer to a high-speed A-to-D converter in portable video, medical or communication systems. The AD8005 is characterized for +5 V and 5 V supplies and will operate over the industrial temperature range of -40C to +85C. The amplifier is supplied in 8-lead plastic DIP, 8-lead SOIC and 5-lead SOT-23 packages. -40 G = +2 VOUT = 200mV p-p RL = 1kV 2ND G = +2 VOUT = 2V p-p RL = 1kV -50 3RD 0 -1 DISTORTION - dBc NORMALIZED GAIN - dB 7 +VS +IN 3 NC = NO CONNECT 3 1 8 NC AD8005 APPLICATIONS Signal Conditioning A/D Buffer Power-Sensitive, High-Speed Systems Battery Powered Equipment Loop/Remote Power Systems Communication or Video Test Systems Portable Medical Instruments 2 AD8005 -IN 2 VS = 5V -2 -3 -60 3RD -70 2ND -80 VS = +5V -4 -90 -5 -6 0.1 1 10 FREQUENCY - MHz 100 500 Figure 1. Frequency Response; G = +2, VS = +5 V or 5 V -100 1 10 20 FREQUENCY - MHz Figure 2. Distortion vs. Frequency; VS = 5 V REV. A 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 1999 AD8005-SPECIFICATIONS 5 V SUPPLIES (@ T = +25C, V = 5 V, R = 1 k unless otherwise noted) A S L Parameter Conditions DYNAMIC PERFORMANCE RF = 3.01 k for "N" Package or RF = 2.49 k for "R" Package or RF = 2.10 k for "RT" Package G = +1, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p G = +10, VO = 4 V p-p, RF = 499 G = +2, VO = 4 V Step G = -1, VO = 4 V Step, RF = 1.5 k G = +2, VO = 2 V Step -3 dB Small Signal Bandwidth Bandwidth for 0.1 dB Flatness Large Signal Bandwidth Slew Rate (Rising Edge) Settling Time to 0.1% DISTORTION/NOISE PERFORMANCE Total Harmonic Distortion Differential Gain Differential Phase Input Voltage Noise Input Current Noise Min 225 140 10 RF = 3.01 k for "N" Package or RF = 2.49 k for "R" Package or RF = 2.10 k for "RT" Package fC = 1 MHz, VO = 2 V p-p, G = +2 fC = 10 MHz, VO = 2 V p-p, G = +2 NTSC, G = +2 NTSC, G = +2 f = 10 MHz f = 10 MHz, +IIN -IIN DC PERFORMANCE Input Offset Voltage AD8005A Typ Max 270 170 30 40 280 1500 28 MHz MHz MHz MHz V/s V/s ns -63 -50 0.11 0.4 4.0 1.1 9.1 dBc dBc % Degrees nV/Hz pA/Hz pA/Hz 400 6 1000 mV mV V/C A A A A nA/C k VCM = 2.5 V 46 90 260 1.6 3.8 54 M pF V dB Positive Negative RL = 50 +3.7 5 TMIN to TMAX Offset Drift +Input Bias Current 40 0.5 TMIN to TMAX -Input Bias Current 5 TMIN to TMAX Input Bias Current Drift ( ) Open-Loop Transimpedance INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Output Current Short Circuit Current +Input -Input +Input POWER SUPPLY Quiescent Current Power Supply Rejection Ratio Units +3.90 -3.90 10 60 400 TMIN to TMAX VS = 4 V to 6 V OPERATING TEMPERATURE RANGE 56 -40 30 50 1 2 10 12 -3.7 V V mA mA 475 560 A A dB +85 C 66 Specifications subject to change without notice. -2- REV. A AD8005 +5 V SUPPLY (@ T = +25C, V = +5 V, R = 1 k to 2.5 V unless otherwise noted) A S L Parameter Conditions DYNAMIC PERFORMANCE RF = 3.01 k for "N" Package or RF = 2.49 k for "R" Package or RF = 2.10 k for "RT" Package G = +1, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p G = +2, VO = 0.2 V p-p G = +10, VO = 2 V p-p, RF = 499 G = +2, VO = 2 V Step G = -1, VO = 2 V Step, RF = 1.5 k G = +2, VO = 2 V Step -3 dB Small Signal Bandwidth Bandwidth for 0.1 dB Flatness Large Signal Bandwidth Slew Rate (Rising Edge) Settling Time to 0.1% DISTORTION/NOISE PERFORMANCE Total Harmonic Distortion Differential Gain Differential Phase Input Voltage Noise Input Current Noise Min 190 110 10 RF = 3.01 k for "N" Package or RF = 2.49 k for "R" Package or RF = 2.10 k for "RT" Package fC = 1 MHz, VO = 2 V p-p, G = +2 fC = 10 MHz, VO = 2 V p-p, G = +2 NTSC, G = +2, RL to 1.5 V NTSC, G = +2, RL to 1.5 V f = 10 MHz f = 10 MHz, +IIN -IIN DC PERFORMANCE Input Offset Voltage AD8005A Typ MHz MHz MHz MHz V/s V/s ns -60 -50 0.14 0.70 4.0 1.1 9.1 dBc dBc % Degrees nV/Hz pA/Hz pA/Hz 50 8 500 mV mV V/C A A A A nA/C k 48 120 300 1.6 1.5 to 3.5 54 M pF V dB 0.95 to 4.05 10 30 V mA mA 5 Offset Drift +Input Bias Current 40 0.5 TMIN to TMAX -Input Bias Current 5 TMIN to TMAX INPUT CHARACTERISTICS Input Resistance Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Output Voltage Swing Output Current Short Circuit Current +Input -Input +Input VCM = 1.5 V to 3.5 V 1.1 to 3.9 RL = 50 POWER SUPPLY Quiescent Current Power Supply Rejection Ratio 350 TMIN to TMAX VS = +4 V to +6 V 56 OPERATING TEMPERATURE RANGE -40 Specifications subject to change without notice. REV. A -3- Units 225 130 30 45 260 775 30 TMIN to TMAX Input Bias Current Drift ( ) Open-Loop Transimpedance Max 35 50 1 2 10 11 425 475 A A dB +85 C 66 AD8005 ABSOLUTE MAXIMUM RATINGS 1 MAXIMUM POWER DISSIPATION Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.6 V Internal Power Dissipation2 Plastic DIP Package (N) . . . . . . . . . . . . . . . . . . . . 1.3 Watts Small Outline Package (R) . . . . . . . . . . . . . . . . . . 0.75 Watts SOT-23-5 Package (RT) . . . . . . . . . . . . . . . . . . . 0.5 Watts Input Voltage (Common Mode) . . . . . . . . . . . . . . . VS 1 V Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . 3.5 V Output Short Circuit Duration . . . . . . . . . . . . . . . . . . . . . . . Observe Power Derating Curves Storage Temperature Range N, R & RT Package . . . . . . . . . . . . . . . . . -65C to +125C Operating Temperature Range (A Grade) . . . -40C to +85C Lead Temperature Range (Soldering 10 sec) . . . . . . . . +300C The maximum power that can be safely dissipated by the AD8005 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. While the AD8005 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 shown in Figure 3. NOTES 1 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. 2 Specification is for device in free air: 8-Lead Plastic DIP Package: JA = 90C/W 8-Lead SOIC Package: JA = 155C/W 5-Lead SOT-23 Package: JA = 240C/W MAXIMUM POWER DISSIPATION - Watts 2.0 TJ = +150C 8-LEAD PLASTIC-DIP PACKAGE 1.5 8-LEAD SOIC PACKAGE 1.0 0.5 5-LEAD SOT-23 PACKAGE 0 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 AMBIENT TEMPERATURE - C 70 80 90 Figure 3. Maximum Power Dissipation vs. Temperature ORDERING GUIDE Model Temperature Range Package Description Package Option AD8005AN AD8005AR AD8005AR-REEL AD8005ART-REEL AD8005AR-REEL7 AD8005ART-REEL7 -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C 8-Lead Plastic DIP 8-Lead Plastic SOIC 13" Tape and Reel 13" Tape and Reel 7" Tape and Reel 7" Tape and Reel N-8 SO-8 SO-8 RT-5 SO-8 RT-5 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 the AD8005 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. -4- Brand Code H1A H1A WARNING! ESD SENSITIVE DEVICE REV. A Typical Characteristics-AD8005 5 NORMALIZED GAIN - dB 3 2 5 3 1 0 G = +2 -1 G = +10 RF = 499V -2 2 1 0 -2 -3 -4 -4 10 FREQUENCY - MHz 100 -5 500 Figure 4. Frequency Response; G = +1, +2, +10; VS = 5 V G = -1 RF = 1.5kV -1 -3 -5 1 VS = 65V VOUT = 200mV p-p RL = 1kV 4 G = +1 VS = 65V VOUT = 200mV p-p RL = 1kV NORMALIZED GAIN - dB 4 G = -10 RF = 1kV 1 10 FREQUENCY - MHz 100 500 Figure 7. Frequency Response; G = -1, -10; VS = 5 V 6.2 6.1 140 0 120 -40 6.0 G = +2 VOUT = 200mV p-p RL = 1kV 5.5 -80 -120 80 GAIN 60 -160 40 -200 20 -240 PHASE - Degrees 5.6 GAIN - dB GAIN - dB 5.8 5.7 PHASE 100 5.9 5.4 5.3 5.2 0.1 1 10 FREQUENCY - MHz 100 0 1k 500 Figure 5. Gain Flatness; G = +2; VS = 5 V or +5 V 10 6 9 PEAK-TO-PEAK OUTPUT VOLTAGE ( 1%THD) - Volts 7 GAIN - dB 4 VS = 65V VOUT = 4V p-p 3 VS = 65V VOUT = 2V p-p 2 1 0 -1 -2 100k 1M 10M FREQUENCY - Hz 100M -280 1G Figure 8. Transimpedance Gain and Phase vs. Frequency 5 8 7 6 5 4 VS = +5V G = +2 RL = 1kV 3 2 1 1 10 100 FREQUENCY - MHz 0 0.5 500 1 10 FREQUENCY - MHz 100 Figure 9. Output Swing vs. Frequency; VS = 5 V Figure 6. Large Signal Frequency Response; G = +2, RL = 1 k REV. A 10k -5- AD8005-Typical Characteristics -40 -40 -50 3RD -60 3RD -70 2ND -80 -90 3RD -60 3RD -70 2ND -80 -90 -100 10 1 -100 20 10 1 FREQUENCY - MHz Figure 13. Distortion vs. Frequency VS = +5 V MIN = -0.06 MAX = 0.03 p-p/MAX = 0.09 MIN = -0.08 MAX = 0.04 p-p/MAX = 0.12 0.10 VS = 5V RL = 1kV G = +2 0.05 DIFF GAIN - % DIFF GAIN - % 0.10 0.00 -0.05 -0.10 VS = +5V RL = 1kV TO +1.5V G = +2 0.05 0.00 -0.05 -0.10 MIN = -0.01 MAX = 0.39 p-p = 0.40 MIN = 0.00 MAX = 0.70 p-p = 0.70 DIFF PHASE - Degrees 0.06 0.04 0.02 0.00 VS = 5V RL = 1kV G = +2 -0.02 -0.04 -0.06 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th MODULATING RAMP LEVEL - IRE Figure 11. Differential Gain and Phase, VS = 5 V 0.5 0.0 -1.0 8 8 VS = 65V 6 5 4 3 VS = +5V 7 2nd 3rd 4th 5th 6th 7th 8th 9th 10th 11th MODULATING RAMP LEVEL - IRE 5 4 3 2 1 0 10 0 3 10k Figure 12. Output Voltage Swing vs. Load f = 5MHz G = +2 RL = 1kV 6 1 100 1k LOAD RESISTANCE - V 1st Figure 14. Differential Gain and Phase, VS = +5 V 9 2 VS = +5V RL = 1kV TO +1.5V G = +2 -0.5 PEAK-TO-PEAK OUTPUT AT 5MHz ( 0.5% THD) - Volts SWING - V p-p 1.0 9 7 20 FREQUENCY - MHz Figure 10. Distortion vs. Frequency; VS = 5 V DIFF PHASE - Degrees 2ND G = +2 VOUT = 2V p-p RL = 1kV -50 DISTORTION - dBc DISTORTION - dBc 2ND G = +2 VOUT = 2V p-p RL = 1kV 4 5 6 7 8 9 TOTAL SUPPLY VOLTAGE - Volts 10 11 Figure 15. Output Swing vs. Supply -6- REV. A AD8005 -5 12.5 -15 INPUT VOLTAGE NOISE - nV/ Hz VS = +5V OR 65V G = +2 RL = 1kV -10 CMRR - dB -20 -25 -30 -35 -40 -45 10.0 7.5 5.0 2.5 -50 -55 0.03 1 10 FREQUENCY - MHz 0.1 0 100 Figure 16. CMRR vs. Frequency; VS = +5 V or 5 V 10 100 1k 10k 100k FREQUENCY - Hz 1M 10M Figure 19. Noise vs. Frequency; VS = +5 V or 5 V 62.5 10 INPUT CURRENT NOISE - pA/ Hz OUTPUT RESISTANCE - V 100 VS = +5V AND 65V RL = 1kV G = +2 VS = +5V VS = 65V 1 0.03 50.0 37.5 25.0 12.5 INVERTING CURRENT NONINVERTING CURRENT 0.1 1 10 FREQUENCY - MHz 100 0 500 10 100 1k 10k 100k FREQUENCY - Hz 1M 10M Figure 20. Noise vs. Frequency; VS = +5 V or 5 V Figure 17. Output Resistance vs. Frequency; VS = 5 V and +5 V 10 0 -10 VS = +5V OR 65V G = +2 RL = 1kV -PSRR -20 PSRR - dB VOUT 100 90 +PSRR VIN -30 VS = 65V G = +6 RL = 1kV -40 -50 10 -60 0% -70 -80 0.03 1V 0.1 1 10 FREQUENCY - MHz 100 150ns 500 Figure 18. PSRR vs. Frequency; VS = +5 V or 5 V REV. A 2V Figure 21. Overdrive Recovery, VS = 5 V, VIN = 2 V Step -7- AD8005-Typical Characteristics RG RF RL 1kV CPROBE VIN 1.5kV VOUT 1.5kV VIN 51.1V RL 1kV CPROBE +VS 50V 0.01mF 10mF 0.01mF 10mF VOUT +VS 0.01mF 10mF 0.01mF 10mF -VS -VS PROBE : TEK P6137 CLOAD = 10pF NOMINAL PROBE : TEK P6137 CLOAD = 10pF NOMINAL Figure 22. Test Circuit; G = +2; RF = RG = 3.01 k for N Package; RF = RG = 2.49 k for R and RT Packages Figure 25. Test Circuit; G = -1, RF = RG = 1.5 k for N, R and RT Packages 100 90 100 90 10 10 0% 0% 50mV 10ns 50mV Figure 23. 200 mV Step Response; G = +2, VS = 2.5 V or 5 V 10ns Figure 26. 200 mV Step Response; G = -1, VS = 2.5 V or 5 V 100 100 90 90 10 10 0% 0% 1V 1V 10ns Figure 24. Step Response; G = +2, VS = 5 V 10ns Figure 27. Step Response; G = -1, VS = 5 V -8- REV. A AD8005 Single-Supply Level Shifter APPLICATIONS Driving Capacitive Loads Capacitive loads interact with an op amp's output impedance to create an extra delay in the feedback path. This reduces circuit stability, and can cause unwanted ringing and oscillation. A given value of capacitance causes much less ringing when the amplifier is used with a higher noise gain. The capacitive load drive of the AD8005 can be increased by adding a low valued resistor in series with the capacitive load. Introducing a series resistor tends to isolate the capacitive load from the feedback loop thereby diminishing its influence. Figure 29 shows the effects of a series resistor on capacitive drive for varying voltage gains. As the closed-loop gain is increased, the larger phase margin allows for larger capacitive loads with less overshoot. Adding a series resistor at lower closed-loop gains accomplishes the same effect. For large capacitive loads, the frequency response of the amplifier will be dominated by the roll-off of the series resistor and capacitive load. In addition to providing buffering, many systems require that an op amp provide level shifting. A common example is the level shifting that is required to move a bipolar signal into the unipolar range of many modern analog-to-digital converters (ADCs). In general, single supply ADCs have input ranges that are referenced neither to ground nor supply. Instead the reference level is some point in between, usually halfway between ground and supply (+2.5 V for a single supply 5 V ADC). Because highspeed ADCs typically have input voltage ranges of 1 V to 2 V, the op amp driving it must be single supply but not necessarily rail-to-rail. R2 1.5kV +5V R1 1.5kV 0.01mF 10mF VIN AD8005 R3 30.1kV RG VOUT VREF +5V RF AD8005 R4 10kV RS RL 1kV 0.1mF CL Figure 30. Bipolar to Unipolar Level Shifter Figure 30 shows a level shifter circuit that can move a bipolar signal into a unipolar range. A positive reference voltage, derived from the +5 V supply, sets a bias level of +1.25 V at the noninverting terminal of the op amp. In ac applications, the accuracy of this voltage level is not important. Noise is however a serious consideration. A 0.1 F capacitor provides useful decoupling of this noise. Figure 28. Driving Capacitive Loads 80 VS = 65V 2V OUTPUT STEP WITH 30% OVERSHOOT CAPACITIVE LOAD - pF 70 60 RS = 10V The bias level on the noninverting terminal sets the input commonmode voltage to +1.25 V. Because the output will always be positive, the op amp may therefore be powered with a single +5 V power supply. 50 RS = 5V 40 30 RS = 0V The overall gain function is given by the equation: 20 R2 R4 R2 V OUT = - V IN + 1+ V REF R1 R3 + R4 R1 10 0 1 2 3 4 CLOSED-LOOP GAIN - V/V 5 In the above example, the equation simplifies to V OUT = -V IN + 2.5V Figure 29. Capacitive Load Drive vs. Closed-Loop Gain REV. A -9- AD8005 Single-Ended-to-Differential Conversion RF RG VOUT RT +5V 2.49kV BIPOLAR SIGNAL 60.5V 0.1mF +5V 0.1mF RIN 1kV RO VIN Many single supply ADCs have differential inputs. In such cases, the ideal common-mode operating point is usually halfway between supply and ground. Figure 31 shows how to convert a single-ended bipolar signal into a differential signal with a common-mode level of 2.5 V. C1 0.01mF C3 10mF C2 0.01mF C4 10mF +VS -VS INVERTING CONFIGURATION RG RF RO VOUT AD8005 2.49kV RF1 2.49kV RG 619V RF2 3.09kV VIN RT VOUT +5V C1 0.01mF C3 10mF C2 0.01mF C4 10mF -VS 0.1mF NONINVERTING CONFIGURATION +5V Figure 32. Inverting and Noninverting Configurations AD8005 2.49kV 2.49kV +VS Chip capacitors have low parasitic resistance and inductance and are suitable for supply bypassing (see Figure 32). Make sure that one end of the capacitor is within 1/8 inch of each power pin with the other end connected to the ground plane. An additional large (0.47 F-10 F) tantalum electrolytic capacitor should also be connected in parallel. This capacitor supplies current for fast, large signal changes at the output. It must not necessarily be as close to the power pin as the smaller capacitor. 0.1mF Figure 31. Single-Ended-to-Differential Converter Amp 1 has its +input driven with the ac-coupled input signal while the +input of Amp 2 is connected to a bias level of +2.5 V. Thus the -input of Amp 2 is driven to virtual +2.5 V by its output. Therefore, Amp 1 is configured for a noninverting gain of five, (1 + RF1/RG), because RG is connected to the virtual +2.5 V of Amp 2's -input. When the +input of Amp 1 is driven with a signal, the same signal appears at the -input of Amp 1. This signal serves as an input to Amp 2 configured for a gain of -5, (-RF2/RG). Thus the two outputs move in opposite directions with the same gain and create a balanced differential signal. This circuit can be simplified to create a bipolar in/bipolar out single-ended to differential converter. Obviously, a single supply is no longer adequate and the -VS pins must now be powered with -5 V. The +input to Amp 2 is tied to ground. The ac coupling on the +input of Amp 1 is removed and the signal can be fed directly into Amp 1. Locate the feedback resistor close to the inverting input pin in order to keep the stray capacitance at this node to a minimum. Capacitance variations of less than 1.5 pF at the inverting input will significantly affect high-speed performance. Use stripline design techniques for long signal traces (i.e., greater than about 1 inch). Striplines should have a characteristic impedance of either 50 or 75 . For the Stripline to be effective, correct termination at both ends of the line is necessary. Table I. Typical Bandwidth vs. Gain Setting Resistors Gain RF RG RT Small Signal -3 dB BW (MHz), VS = 5 V -1 -10 +1 +2 +10 1.49 k 1 k 2.49 k 2.49 k 499 1.49 k 100 2.49 k 56.2 52.3 100 49.9 49.9 49.9 120 MHz 60 MHz 270 MHz 170 MHz 40 MHz Layout Considerations In order to achieve the specified high-speed performance of the AD8005 you must be attentive to board layout and component selection. Proper RF design techniques and selection of components with low parasitics are necessary. The PCB should have a ground plane that covers all unused portions of the component side of the board. This will provide a low impedance path for signals flowing to ground. The ground plane should be removed from the area under and around the chip (leave about 2 mm between the pin contacts and the ground plane). This helps to reduce stray capacitance. If both signal tracks and the ground plane are on the same side of the PCB, also leave a 2 mm gap between ground plane and track. -10- REV. A AD8005 Increasing Feedback Resistors Unlike conventional voltage feedback op amps, the choice of feedback resistor has a direct impact on the closed-loop bandwidth and stability of a current feedback op amp circuit. Reducing the resistance below the recommended value makes the amplifier more unstable. Increasing the size of the feedback resistor reduces the closed-loop bandwidth. 360mA (rms) 562V 4.99kV +5V AD8005 VIN In power-critical applications where some bandwidth can be sacrificed, increasing the size of the feedback resistor will yield significant power savings. A good example of this is the gain of +10 case. Operating from a bipolar supply ( 5 V), the quiescent current is 475 A (excluding the feedback network). The recommended feedback and gain resistors are 499 and 56.2 respectively. In order to drive an rms output voltage of 2 V, the output must deliver a current of 3.6 mA to the feedback network. Increasing the size of the resistor network by a factor of 10 as shown in Figure 33 will reduce this current to 360 A. The closed loop bandwidth will however decrease to 20 MHz. VOUT 2V (rms) QUIESCENT CURRENT 475mA (MAX) 0.2V (rms) -5V Figure 33. Saving Power by Increasing Feedback Resistor Network REV. A -11- AD8005 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Plastic DIP (N-8) 8 C2186a-0-8/99 0.430 (10.92) 0.348 (8.84) 5 0.280 (7.11) 0.240 (6.10) 1 4 0.060 (1.52) 0.015 (0.38) PIN 1 0.210 (5.33) MAX 0.325 (8.25) 0.300 (7.62) 0.195 (4.95) 0.115 (2.93) 0.130 (3.30) MIN 0.160 (4.06) 0.115 (2.93) 0.015 (0.381) 0.008 (0.204) SEATING PLANE 0.022 (0.558) 0.100 0.070 (1.77) 0.014 (0.356) (2.54) 0.045 (1.15) BSC 8-Lead Plastic SOIC (SO-8) 0.1968 (5.00) 0.1890 (4.80) 0.1574 (4.00) 0.1497 (3.80) 8 5 1 4 PIN 1 0.2440 (6.20) 0.2284 (5.80) 0.0688 (1.75) 0.0532 (1.35) 0.0098 (0.25) 0.0040 (0.10) 0.0500 0.0192 (0.49) (1.27) 0.0138 (0.35) BSC SEATING PLANE 0.0196 (0.50) x 45 0.0099 (0.25) 0.0098 (0.25) 0.0075 (0.19) 8 0 0.0500 (1.27) 0.0160 (0.41) 5-Lead Plastic SOT-23 (RT-5) 0.1181 (3.00) 0.1102 (2.80) 0.0669 (1.70) 0.0590 (1.50) 3 2 1 4 0.1181 (3.00) 0.1024 (2.60) 5 0.0748 (1.90) BSC 0.0512 (1.30) 0.0354 (0.90) 0.0059 (0.15) 0.0019 (0.05) 0.0079 (0.20) 0.0031 (0.08) 0.0571 (1.45) 0.0374 (0.95) 0.0197 (0.50) 0.0138 (0.35) SEATING PLANE -12- PRINTED IN U.S.A. 0.0374 (0.95) BSC 10 0 0.0217 (0.55) 0.0138 (0.35) REV. A