AD815ARB-24

a FEATURES Flexible Configuration Differential Input and Output Driver or Two Single-Ended Drivers Industrial Temperature Range High Output Power Thermally Enhanced SOIC 400 mA Minimum Output Drive/Amp, RL = 10 Low Distortion –66 dB @ 1 MHz THD, RL = 200 , V OUT = 40 V p-p 0.05% and 0.45 Differential Gain and Phase, R L = 25 (6 Back-Terminated Video Loads) High Speed 120 MHz Bandwidth (–3 dB) 900 V/ s Differential Slew Rate 70 ns Settling Time to 0.1% Thermal Shutdown APPLICATIONS ADSL, HDSL, and VDSL Line Interface Driver Coil or Transformer Driver CRT Convergence and Astigmatism Adjustment Video Distribution Amp Twisted Pair Cable Driver GENERAL DESCRIPTION High Output Current Differential Driver AD815 FUNCTIONAL BLOCK DIAGRAM NC 1 NC 2 NC 3 NC 4 5 THERMAL HEAT TABS +VS* 6 24 NC 23 NC 22 NC 21 NC AD815 20 THERMAL HEAT TABS +VS* TOP VIEW 19 7 (Not to Scale) 18 8 17 +IN1 9 –IN1 10 OUT1 11 –VS 12 16 +IN2 15 –IN2 14 OUT2 13 +VS NC = NO CONNECT *HEAT TABS ARE CONNECTED TO THE POSITIVE SUPPLY. combined with the wide bandwidth and high current drive make the differential driver ideal for communication applications such as subscriber line interfaces for ADSL, HDSL and VDSL. The AD815 differential slew rate of 900 V/µs and high load drive are suitable for fast dynamic control of coils or transformers, and the video performance of 0.05% and 0.45° differential gain and phase into a load of 25 Ω enable up to 12 back-terminated loads to be driven. The 24-lead SOIC (RB) is capable of driving 26 dBm for full rate ADSL with proper heat sinking. +15V 100 The AD815 consists of two high speed amplifiers capable of supplying a minimum of 500 mA. They are typically configured as a differential driver enabling an output signal of 40 V p-p on ± 15 V supplies. This can be increased further with the use of a coupling transformer with a greater than 1:1 turns ratio. The low harmonic distortion of –66 dB @ 1 MHz into 200 Ω –40 TOTAL HARMONIC DISTORTION – dBc –50 –60 –70 –80 –90 –100 RL = 50 (DIFFERENTIAL) VS = 15V G = +10 VOUT = 40V p-p 1/2 AD815 AMP1 499 R1 = 15 VIN = 4Vp-p 110 G = +10 499 VD = 40Vp-p RL 120 VOUT = 40Vp-p 100 AMP2 1/2 AD815 –15V R2 = 15 1:2 TRANSFORMER RL = 200 (DIFFERENTIAL) Figure 2. Subscriber Line Differential Driver –110 100 1k 10k 100k FREQUENCY – Hz 1M 10M Figure 1. Total Harmonic Distortion vs. Frequency REV. C 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. 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 © 2005 Analog Devices, Inc. All rights reserved. AD815–SPECIFICATIONS (@ T = +25 C, V = A S 15 V dc, RFB = 1 k and RLOAD = 100 VS ± 15 ±5 ± 15 ±5 ± 15 ± 15 ± 15 ± 5, ± 15 ± 5, ± 15 ± 5, ± 15 ± 15 ± 15 ±5 ± 15 Min 100 90 unless otherwise noted) AD815A Typ Max 120 110 40 10 900 70 –66 1.85 1.8 19 0.05 0.45 5 10 20 0.5 0.5 10 10 2 10 8 15 30 2 4 5 90 150 5 5 75 100 Units MHz MHz MHz MHz V/µs ns dBc nV/√Hz pA/√Hz pA/√Hz % Degrees mV mV mV µV/°C mV mV mV µV/°C µA µA µA µA µA µA MΩ MΩ MΩ Ω pF ±V ±V dB dB ±V ±V ±V ±V mA A Ω dB ± 18 30 40 40 55 V mA mA mA mA dB Model DYNAMIC PERFORMANCE Small Signal Bandwidth (–3 dB) Bandwidth (0.1 dB) Differential Slew Rate Settling Time to 0.1% NOISE/HARMONIC PERFORMANCE Total Harmonic Distortion Input Voltage Noise Input Current Noise (+I IN) Input Current Noise (–I IN) Differential Gain Error Differential Phase Error DC PERFORMANCE Input Offset Voltage Conditions G = +1 G = +1 G = +2 G = +2 VOUT = 20 V p-p, G = +2 10 V Step, G = +2 f = 1 MHz, RLOAD = 200 Ω, VOUT = 40 V p-p f = 10 kHz, G = +2 (Single Ended) f = 10 kHz, G = +2 f = 10 kHz, G = +2 NTSC, G = +2, RLOAD = 25 Ω NTSC, G = +2, RLOAD = 25 Ω 800 TMIN – TMAX Input Offset Voltage Drift Differential Offset Voltage TMIN – TMAX Differential Offset Voltage Drift –Input Bias Current TMIN – TMAX +Input Bias Current TMIN – TMAX Differential Input Bias Current TMIN – TMAX Open-Loop Transresistance TMIN – TMAX INPUT CHARACTERISTICS Differential Input Resistance Differential Input Capacitance Input Common-Mode Voltage Range Common-Mode Rejection Ratio Differential Common-Mode Rejection Ratio OUTPUT CHARACTERISTICS Voltage Swing TMIN – TMAX TMIN – TMAX Single Ended, R LOAD = 25 Ω Differential, R LOAD = 50 Ω TMIN – TMAX RLOAD = 10 Ω +Input –Input ± 15 ± 15 ± 15 ±5 ± 5, ± 15 ± 5, ± 15 ± 15 ±5 ± 15 ± 15 ± 15 ± 15 ± 15 ± 15 ±5 ± 15 ±5 ± 15 ± 5, ± 15 ± 5, ± 15 ± 5, ± 15 ± 5, ± 15 ± 5, ± 15 1.0 0.5 ±5 ± 15 5.0 57 80 11.0 1.1 21 22.5 400 7 15 1.4 13.5 3.5 65 100 11.7 1.8 23 24.5 500 1.0 13 –65 Output Current1 RB-24 Short Circuit Current Output Resistance MATCHING CHARACTERISTICS Crosstalk POWER SUPPLY Operating Range2 Quiescent Current f = 1 MHz TMIN – TMAX TMIN – TMAX 23 30 Power Supply Rejection Ratio TMIN – TMAX –55 –66 NOTES 1 Output current is limited in the 24-lead SOIC package to the maximum power dissipation. See absolute maximum ratings and derating curves. 2 Observe derating curves for maximum junction temperature. Specifications subject to change without notice. –2– REV. C AD815 ABSOLUTE MAXIMUM RATINGS 1 MAXIMUM POWER DISSIPATION Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V Total Internal Power Dissipation2 Small Outline (RB) . . 2.4 Watts (Observe Derating Curves) Input Voltage (Common Mode) . . . . . . . . . . . . . . . . . . . . ± VS Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . ± 6 V Output Short Circuit Duration . . . . . . . . . . . . . . . . . . . . . . Observe Power Derating Curves Can Only Short to Ground Storage Temperature Range RB Package . . . . . . . . . . . . . . . . . . . . . . . –65°C to +125°C Operating Temperature Range AD815A . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C Lead Temperature Range (Soldering, 10 sec) . . . . . . . . 300°C 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 with 0 ft/min air flow: 24-Lead Surface Mount: θJA = 52°C/W. The maximum power that can be safely dissipated by the AD815 is limited by the associated rise in junction temperature. The maximum safe junction temperature for the plastic encapsulated parts is determined by the glass transition temperature of the plastic, about 150°C. 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 175° C for an extended period can result in device failure. The AD815 has thermal shutdown protection, which guarantees that the maximum junction temperature of the die remains below a safe level, even when the output is shorted to ground. Shorting the output to either power supply will result in device failure. To ensure proper operation, it is important to observe the derating curves and refer to the section on power considerations. It must also be noted that in high (noninverting) gain configurations (with low values of gain resistor), a high level of input overdrive can result in a large input error current, which may result in a significant power dissipation in the input stage. This power must be included when computing the junction temperature rise due to total internal power. 14 13 12 11 10 9 8 7 6 5 4 3 2 1 TJ = 150 C PIN CONFIGURATION 24-Lead Thermally-Enhanced SOIC (RB-24) NC 1 NC 2 NC 3 NC 4 5 THERMAL HEAT TABS +VS* 6 24 NC 23 NC 22 NC 21 NC AD815 20 19 THERMAL HEAT TABS +VS* TOP VIEW 7 (Not to Scale) 18 8 17 +IN1 9 –IN1 10 OUT1 11 –VS 12 16 +IN2 15 –IN2 14 OUT2 13 +VS MAXIMUM POWER DISSIPATION – Watts θJA = 52 C/W (STILL AIR = 0 FT/MIN) NO HEAT SINK AD815ARB-24 70 80 90 NC = NO CONNECT *HEAT TABS ARE CONNECTED TO THE POSITIVE SUPPLY. 0 –50 –40 –30 –20 –10 0 10 20 30 40 50 60 AMBIENT TEMPERATURE – C Figure 3. Plot of Maximum Power Dissipation vs. Temperature ORDERING GUIDE Model Option AD815ARB-24 AD815ARB-24-REEL Temperature Range –40°C to +85°C –40°C to +85°C Package Description 24-Lead Thermally Enhanced SOIC 24-Lead Thermally Enhanced SOIC Package RB-24 RB-24 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 AD815 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. WARNING! ESD SENSITIVE DEVICE REV. C –3– AD815–Typical Performance Characteristics 20 36 34 VS = 15V 15 32 COMMON-MODE VOLTAGE RANGE – Volts SUPPLY CURRENT – mA 30 28 26 VS = 24 22 20 5V 10 5 0 0 5 10 SUPPLY VOLTAGE – 15 Volts 20 18 –40 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 Figure 4. Input Common-Mode Voltage Range vs. Supply Voltage Figure 7. Total Supply Current vs. Temperature 40 80 33 DIFFERENTIAL OUTPUT VOLTAGE – V p-p SINGLE-ENDED OUTPUT VOLTAGE – V p-p TOTAL SUPPLY CURRENT – mA TA = +25 C 30 30 NO LOAD 60 27 20 RL = 50 (DIFFERENTIAL) RL = 25 (SINGLE-ENDED) 40 24 10 20 21 0 0 5 10 SUPPLY VOLTAGE – 15 Volts 0 20 18 0 2 4 6 8 10 12 SUPPLY VOLTAGE – Volts 14 16 Figure 5. Output Voltage Swing vs. Supply Voltage Figure 8. Total Supply Current vs. Supply Voltage 30 SINGLE-ENDED OUTPUT VOLTAGE – Volts p-p 60 VS = 15V 50 DIFFERENTIAL OUTPUT VOLTAGE – Volts p-p 10 0 INPUT BIAS CURRENT – A SIDE A, B VS = 15V, +I B 5V 25 –10 –20 –30 –40 –50 –60 SIDE A –70 VS = –80 –40 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 SIDE B –I B 15V 100 VS = 5V 20 40 15 30 SIDE B –IB SIDE A 10 VS = 5 5V 20 10 0 10 100 LOAD RESISTANCE – (Differential – 1k ) (Single-Ended – 0 10k /2) Figure 6. Output Voltage Swing vs. Load Resistance Figure 9. Input Bias Current vs. Temperature –4– REV. C AD815 0 –2 80 TA = 25 C 60 40 VS = 15V VS = 10V VS = 5V VIN f = 0.1Hz 100 49.9 –40 1k –60 –2.0 –1.6 –1.2 0 –0.8 –0.4 0.4 0.8 LOAD CURRENT – Amps 1k INPUT OFFSET VOLTAGE – mV VS = –6 –8 –10 VS = –12 –14 –40 15V 5V RTI OFFSET – mV –4 20 0 –20 1/2 AD815 VOUT RL= 5 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 1.2 1.6 2.0 Figure 10. Input Offset Voltage vs. Temperature Figure 13. Thermal Nonlinearity vs. Output Current Drive 750 VS = 15V 100 SHORT CIRCUIT CURRENT – mA 700 SOURCE 650 CLOSED-LOOP OUTPUT RESISTANCE – 10 VS = 5V 600 SINK 550 1 VS = 15V 0.1 500 0.01 450 –60 –40 –20 0 20 40 60 80 100 JUNCTION TEMPERATURE – C 120 140 30k 100k 300k 1M 3M 10M FREQUENCY – Hz 30M 100M 300M Figure 11. Short Circuit Current vs. Temperature Figure 14. Closed-Loop Output Resistance vs. Frequency 15 TA = 25 C RL = 25 VS = RTI OFFSET – mV VS = 5V 10V VS = 15V DIFFERENTIAL OUTPUT VOLTAGE – V p-p 40 10 TA = 25 C VS = ±15V RL = 100 5 30 RL = 50 20 RL = 25 10 RL = 1 0 0 2 4 10 8 6 FREQUENCY – MHz 12 14 0 VIN f = 0.1Hz 100 49.9 –5 1/2 AD815 VOUT RL= 25 –10 1k –15 –20 1k –16 –12 –8 –4 0 4 VOUT – Volts 8 12 16 20 Figure 12. Gain Nonlinearity vs. Output Voltage Figure 15. Large Signal Frequency Response REV. C –5– AD815 100 100 120 110 VOLTAGE NOISE – nV/ √ Hz CURRENT NOISE – pA/ √ Hz TRANSIMPEDANCE TRANSIMPEDANCE – dB INVERTING INPUT CURRENT NOISE 100 90 80 70 60 50 40 PHASE 100 500 10 10 –50 –100 –150 –200 –250 1k 10k 100k 1M FREQUENCY – Hz 10M 100M NONINVERTING INPUT CURRENT NOISE 1 10 INPUT VOLTAGE NOISE 100 1k FREQUENCY – Hz 10k 30 1 100k 100 Figure 16. Input Current and Voltage Noise vs. Frequency Figure 19. Open-Loop Transimpedance vs. Frequency 90 –40 TOTAL HARMONIC DISTORTION – dBc –50 –60 –70 –80 –90 –100 –110 100 RL = 50 (DIFFERENTIAL) RL = 200 (DIFFERENTIAL) VS = 15V G = +10 VOUT = 40V p-p COMMON-MODE REJECTION – dB 80 VS = 70 60 50 40 30 20 10 10k 562 VIN 562 562 SIDE B SIDE A 562 VOUT 15V 1/2 AD815 100k 1M FREQUENCY – Hz 10M 100M 1k 10k 100k FREQUENCY – Hz 1M 10M Figure 17. Common-Mode Rejection vs. Frequency Figure 20. Total Harmonic Distortion vs. Frequency 0 OUTPUT SWING FROM ±V TO 0 – Volts 10 VS = 15V G = +2 RL = 100 8 1% 6 4 2 0 –2 –4 –6 1% –8 0 20 60 40 70 SETTLING TIME – ns 80 100 0.1% GAIN = +2 VS = 15V 0.1% –10 –20 –30 PSRR – dB –40 –PSRR –50 –60 –70 –80 –90 +PSRR –100 0.01 –10 0.1 1 10 FREQUENCY – MHz 100 300 Figure 18. Power Supply Rejection vs. Frequency Figure 21. Output Swing and Error vs. Settling Time –6– REV. C PHASE – Degrees 0 AD815 700 G = +10 SINGLE-ENDED SLEW RATE – V/ s (PER AMPLIFIER) DIFFERENTIAL SLEW RATE – V/ s 1400 1200 1000 G = +2 800 600 400 200 0 0 5 10 15 OUTPUT STEP SIZE – V p-p 20 25 OPEN-LOOP TRANSRESISTANCE – M 5 600 500 400 300 200 100 0 4 SIDE B 3 SIDE A 2 –TZ 1 SIDE B +TZ SIDE A 0 –40 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 Figure 22. Slew Rate vs. Output Step Size Figure 25. Open-Loop Transresistance vs. Temperature –85 VS = SIDE B –80 SIDE A –75 OUTPUT SWING – Volts +PSRR 15V 15 VS = 14 15V RL = 150 +VOUT | –VOUT | +VOUT 12 | –VOUT | 11 RL = 25 PSRR – dB 13 –70 SIDE A –65 SIDE B –PSRR –60 –40 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 10 –40 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 Figure 23. PSRR vs. Temperature Figure 26. Single-Ended Output Swing vs. Temperature –74 –73 27 26 OUTPUT SWING – Volts –72 VS = 15V RL = 50 25 –VOUT +VOUT 24 CMRR – dB –71 –70 –69 –CMRR –68 –67 –66 –40 +CMRR 23 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 22 –40 –20 0 20 40 60 JUNCTION TEMPERATURE – C 80 100 Figure 24. CMRR vs. Temperature Figure 27. Differential Output Swing vs. Temperature REV. C –7– AD815 DIFF PHASE – Degrees 6 BACK TERMINATED LOADS (25 ) 0.04 0.03 0.02 0.01 0.00 –0.01 –0.02 –0.03 –0.04 0.010 0.005 0.000 –0.005 –0.010 –0.015 –0.020 –0.025 –0.030 0.5 0.4 0.3 0.2 0.1 0.0 –0.1 –0.2 –0.3 0.12 0.10 0.08 0.06 0.04 0.02 0.00 –0.02 –0.04 DIFF GAIN – % 1 0 5V 0.1 NORMALIZED FLATNESS – dB NORMALIZED FREQUENCY RESPONSE – dB 15V PHASE G = +2 RF = 1k NTSC 15V –1 –2 B A A –3 –4 –5 0 –0.1 –0.2 –0.3 –0.4 –0.5 –0.6 –0.7 0.1 VIN 100 49.9 499 499 100 VOUT 5V B GAIN 1 2 3 4 5 6 7 8 9 10 11 DIFF GAIN – % PHASE GAIN G = +2 RF = 1k NTSC PHASE 3 4 5 6 7 8 9 10 11 DIFF PHASE – Degrees 2 BACK TERMINATED LOADS (75 ) –6 –7 –8 –9 300 GAIN 1 2 1 10 FREQUENCY – MHz 100 Figure 28. Differential Gain and Differential Phase (per Amplifier) Figure 31. Bandwidth vs. Frequency, G = +2 –10 1 NORMALIZED OUTPUT VOLTAGE – dB –20 –30 CROSSTALK – dB –40 –50 –60 –70 G = +2 RF = 499 VS = 15V, 5V VIN = 400mVrms RL = 100 SIDE B VS = 0 –1 –2 –3 VIN –4 15V SIDE A SIDE B 100 49.9 VOUT 100 SIDE A –80 –90 –5 –6 –7 0.1 124 499 –100 –110 0.03 0.1 1 10 FREQUENCY – MHz 100 300 1 10 FREQUENCY – MHz 100 300 Figure 29. Output-to-Output Crosstalk vs. Frequency Figure 32. –3 dB Bandwidth vs. Frequency, G = +5 2 1 0 VS = 15V VIN = 0 dBm SIDE A SIDE B 100 90 OUTPUT VOLTAGE – dB –1 –2 –3 –4 –5 –6 –7 –9 0.1 49.9 562 100 VIN 100 VOUT 10 0% 5V 1s 1 10 FREQUENCY – MHz 100 300 Figure 30. –3 dB Bandwidth vs. Frequency, G = +1 Figure 33. 40 V p-p Differential Sine Wave, RL = 50 Ω, f = 100 kHz –8– REV. C AD815 562 +15V 10 F 0.1 F 8 RF +15V 10 F 0.1 F RS 8 1/2 AD815 100 VIN PULSE GENERATOR TR/TF = 250ps 50 –15V 7 1/2 AD815 0.1 F RL = 100 VIN PULSE GENERATOR TR/TF = 250ps 100 7 0.1 F 10 F –15V RL = 100 10 F 50 Figure 34. Test Circuit, Gain = +1 SIDE A Figure 38. Test Circuit, Gain = 1 + R F /RS G = +1 RF = 698 RL = 100 SIDE A G = +5 RF = 562 RL = 100 RS = 140 SIDE B SIDE B 100mV 20ns 5V 100ns Figure 35. 500 mV Step Response, G = +1 Figure 39. 20 V Step Response, G = +5 SIDE A G = +1 RF = 562 RL = 100 562 +15V 10 F 0.1 F 562 VIN PULSE GENERATOR TR/TF = 250ps 55 100 7 8 SIDE B 1/2 AD815 0.1 F 10 F –15V RL = 100 1V 20ns Figure 36. 4 V Step Response, G = +1 Figure 40. Test Circuit, Gain = –1 SIDE A G = +1 RF = 562 RL = 100 SIDE A G = –1 RF = 562 RL = 100 SIDE B SIDE B 2V 50ns 100mV 20ns Figure 37. 10 V Step Response, G = +1 Figure 41. 500 mV Step Response, G = –1 REV. C –9– AD815 Choice of Feedback and Gain Resistors SIDE A G = –1 RF = 562 RL = 100 SIDE B The fine scale gain flatness will, to some extent, vary with feedback resistance. It therefore is recommended that once optimum resistor values have been determined, 1% tolerance values should be used if it is desired to maintain flatness over a wide range of production lots. Table I shows optimum values for several useful configurations. These should be used as starting point in any application. Table I. Resistor Values 1V 20ns RF ( ) G= +1 –1 +2 +5 +10 562 499 499 499 1k RG ( ) 499 499 125 110 Figure 42. 4 V Step Response, G = –1 THEORY OF OPERATION The AD815 is a dual current feedback amplifier with high (500 mA) output current capability. Being a current feedback amplifier, the AD815’s open-loop behavior is expressed as transimpedance, ∆ V O / ∆ I –IN , or T Z . 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. Since RIN is proportional to 1/gM, the equivalent voltage gain is just TZ × gM, where the gM in question is the transconductance of the input stage. Using this amplifier as a follower with gain, Figure 43, basic analysis yields the following result: T Z (S ) VO =G× VIN T Z (S ) + G × RIN + RF PRINTED CIRCUIT BOARD LAYOUT CONSIDERATIONS As to be expected for a wideband amplifier, PC board 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, a space (5 mm min) should be left around the signal lines to minimize coupling. POWER SUPPLY BYPASSING where: RF RG RIN = 1/gM ≈ 25 Ω G = 1+ RF RG RIN RN VIN 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 amplifier’s response. In addition, if large current transients must be delivered to the load, then bypass capacitors (typically greater than 1 µF) will be required to provide the best settling time and lowest distortion. A parallel combination of 10.0 µF and 0.1 µF is recommended. Under some low frequency applications, a bypass capacitance of greater than 10 µF may be necessary. Due to the large load currents delivered by the AD815, special consideration must be given to careful bypassing. The ground returns on both supply bypass capacitors as well as signal common must be “star” connected as shown in Figure 44. +VS +IN Figure 43. Current Feedback Amplifier Operation RF RG (OPTIONAL) RF +OUT Recognizing that G × RIN