Low Cost, General-Purpose High Speed JFET Amplifier AD825 APPLICATIONS CCDs Low distortion filters Mixed gain stages Audio amplifiers Photo detector interfaces ADC input buffers DAC output buffers NC 1 NC 8 AD825 -IN 2 +VS TOP VIEW 6 OUTPUT (Not to Scale) -VS 4 5 NC 7 +IN 3 NC = NO CONNECT 00876-E-001 High speed 41 MHz, -3 dB bandwidth 125 V/s slew rate 80 ns settling time Input bias current of 20 pA and noise current of 10 fA/Hz Input voltage noise of 12 nV/Hz Fully specified power supplies: 5 V to 15 V Low distortion: -76 dB at 1 MHz High output drive capability Drives unlimited capacitance load 50 mA min output current No phase reversal when input is at rail Available in 8-lead SOIC CONNECTION DIAGRAMS Figure 1. 8-Lead Plastic SOIC (R) Package NC 1 16 NC NC 2 15 NC NC 3 -INPUT 4 14 NC AD825 13 +VS TOP VIEW +INPUT 5 (Not to Scale) 12 OUTPUT 11 NC -VS 6 NC 7 10 NC NC 8 9 00876-E-002 FEATURES NC NC = NO CONNECT Figure 2. 16-Lead Plastic SOIC (R-16) Package GENERAL DESCRIPTION The unique input stage has ultralow input bias current and input current noise. Signals that go to either rail on this high performance input do not cause phase reversals at the output. These features make the AD825 a good choice as a buffer for MUX outputs, creating minimal offset and gain errors. The AD825 is fully specified for operation with dual 5 V and 15 V supplies. This power supply flexibility, and the low supply current of 6.5 mA with excellent ac characteristics under all supply conditions, makes the AD825 well-suited for many demanding applications. 10V 200ns 10V 00876-E-003 The AD825 is a superbly optimized operational amplifier for high speed, low cost, and dc parameters, making it ideally suited for a broad range of signal conditioning and data acquisition applications. The ac performance, gain, bandwidth, slew rate, and drive capability are all very stable over temperature. The AD825 also maintains stable gain under varying load conditions. Figure 3. Performance with Rail-to-Rail Input Signals Rev. F Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 (c) 2004 Analog Devices, Inc. All rights reserved. AD825 TABLE OF CONTENTS Specifications..................................................................................... 3 REVISION HISTORY Absolute Maximum Ratings............................................................ 5 10/04--Data Sheet Changed from Rev. E to Rev. F Changes to Figure 1......................................................................... 1 Changes to Figure 4......................................................................... 5 Changes to Figure 21....................................................................... 8 Pin Configurations ........................................................................... 5 ESD Caution.................................................................................. 5 Typical Performance Characteristics ............................................. 6 Driving Capacitive Loads .............................................................. 10 Theory of Operation ...................................................................... 10 Input Consideration................................................................... 10 Grounding and Bypassing ......................................................... 10 Second-Order Low-Pass Filter.................................................. 11 Outline Dimensions ....................................................................... 12 Ordering Guide........................................................................... 12 3/04--Data Sheet Changed from Rev. D to Rev. E Changes to Specifications............................................................... 3 Addition of 16-Lead SOIC Pin Configuration ............................ 5 Changes to Figure 27....................................................................... 9 Updated Outline Dimensions...................................................... 12 Updated Ordering Guide.............................................................. 12 2/01--Data Sheet Changed from Rev. C to Rev. D Addition of 16-lead SOIC package (R-16) Connection Diagram ...................................................................... 4 Addition to Absolute Maximum Ratings ..................................... 4 Addition to Ordering Guide (R-16).............................................. 4 Addition of 16-lead SOIC package (R-16) Outline Dimensions ...................................................................... 11 Rev. F | Page 2 of 12 AD825 SPECIFICATIONS All limits are determined to be at least four standard deviations away from mean value. At TA = 25C, VS = 15 V, unless otherwise noted. Table 1. Parameter DYNAMIC PERFORMANCE Unity Gain Bandwidth Bandwidth for 0.1 dB Flatness -3 dB Bandwidth Slew Rate Settling Time to 0.1% to 0.1% Total Harmonic Distortion Differential Gain Error (RLOAD = 150 ) Differential Phase Error (RLOAD = 150 ) INPUT OFFSET VOLTAGE Conditions Gain = +1 Gain = +1 RLOAD = 1 k, G = +1 0 V to 10 V Step, AV = -1 0 V to 10 V Step, AV = -1 FC = 1 MHz, G = -1 NTSC Gain = +2 NTSC Gain = +2 VS Min 15 V 15 V 15 V 15 V 15 V 15 V 15 V 15 V 23 18 44 125 AD825A Typ 26 21 46 140 150 180 -77 1.3 2.1 15 V 1 15 V 10 15 40 20 700 30 TMIN TMAX 15 V COMMON-MODE REJECTION INPUT VOLTAGE NOISE TMIN TMAX VOUT = 10 V RLOAD = 1 k VOUT = 7.5 V RLOAD = 1 k VOUT = 7.5 V RLOAD = 150 k (50 mA Output) VCM = 10 f = 10 kHz 15 V 15 V INPUT CURRENT NOISE f = 10 kHz 15 V INPUT COMMON-MODE VOLTAGE RANGE OUTPUT VOLTAGE SWING Output Current Short-Circuit Current INPUT RESISTANCE INPUT CAPACITANCE OUTPUT RESISTANCE POWER SUPPLY Quiescent Current RLOAD = 1 k RLOAD = 500 2 5 5 Rev. F | Page 3 of 12 MHz MHz MHz V/s ns ns dB % 440 mV mV V/C pA pA pA pA pA pA 15 V 70 76 dB 70 76 dB 68 71 74 80 12 dB dB 15 V 15 V 15 V 15 V 15 V 15 V 15 V Open Loop TMIN to TMAX Unit Degrees 5 INPUT OFFSET CURRENT OPEN-LOOP GAIN 180 220 15 V TMIN to TMAX Offset Drift INPUT BIAS CURRENT Max 15 V 15 V nV/Hz fA/Hz 10 13 12.9 50 13.5 13.3 13.2 V V V mA mA pF 100 5 x1011 6 8 6.5 7.2 7.5 mA mA AD825 All limits are determined to be at least four standard deviations away from mean value. At TA = 25C, VS = 5 V unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE Unity Gain Bandwidth Bandwidth for 0.1 dB Flatness -3 dB Bandwidth Slew Rate Settling Time to 0.1% to 0.01% Total Harmonic Distortion Differential Gain Error (RLOAD = 150 ) Differential Phase Error (RLOAD = 150 ) INPUT OFFSET VOLTAGE Conditions Gain = +1 Gain = +1 RLOAD = 1 k, G = -1 -2.5 V to +2.5 V -2.5 V to +2.5 V FC = 1 MHz, G = -1 NTSC Gain = +2 NTSC Gain = +2 VS Min 5 V 5 V 5 V 5 V 5 V 5 V 5 V 5 V 18 8 34 115 AD825A Typ 21 10 37 130 75 90 -76 1.2 1.4 5 V 1 5 V 10 10 30 15 600 25 TMIN TMAX INPUT OFFSET CURRENT 5 V COMMON-MODE REJECTION INPUT VOLTAGE NOISE 5 V 5 V INPUT CURRENT NOISE f = 10 kHz 5 V INPUT COMMON-MODE VOLTAGE RANGE OUTPUT VOLTAGE SWING Output Current Short-Circuit Current INPUT RESISTANCE INPUT CAPACITANCE OUTPUT RESISTANCE POWER SUPPLY Quiescent Current POWER SUPPLY REJECTION Rev. F | Page 4 of 12 MHz MHz MHz V/s ns ns dB % 280 mV mV V/C pA pA pA pA pA pA 5 V 64 64 69 5 V 5 V 66 66 80 12 dB dB dB nV/Hz fA/Hz 10 +3.2 +3.1 50 3.5 3.4 3.2 V V V mA mA pF 80 5 x1011 6 8 Open Loop TMIN to TMAX VS = 5 V to 15 V 2 5 5 5 V RLOAD = 500 RLOAD = 150 Unit Degrees 5 TMIN TMAX VOUT = 2.5 RLOAD = 500 RLOAD = 150 VCM = 2 V f = 10 kHz Offset Current Drift OPEN-LOOP GAIN 90 110 5 V TMIN to TMAX Offset Drift INPUT BIAS CURRENT Max 5 V 5 V 6.2 76 88 6.8 7.5 mA mA dB AD825 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATIONS Table 3. NC 1 Rating 18 V NC 8 AD825 -IN 2 +VS TOP VIEW 6 OUTPUT (Not to Scale) -VS 4 5 NC 7 See Figure 6 VS VS See Figure 6 -65C to +125C -40C to +85C 300C NC = NO CONNECT 00876-E-001 +IN 3 Figure 4. 8-Lead SOIC NC 1 16 NC NC 2 15 NC NC 3 14 NC -INPUT 4 AD825 +VS TOP VIEW +INPUT 5 (Not to Scale) 12 OUTPUT 11 NC -VS 6 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. 13 NC 7 10 NC NC 8 9 NC NC = NO CONNECT 00876-E-002 Parameter Supply Voltage Internal Power Dissipation1 Small Outline (R) Input Voltage (Common Mode) Differential Input Voltage Output Short-Circuit Duration Storage Temperature Range (R, R-16) Operating Temperature Range Lead Temperature Range (Soldering 10 sec) Figure 5. 16-Lead SOIC Specification is for device in free air: 8-lead SOIC package: JA = 155C/W 16-lead SOIC package: JA = 85C/W TJ = 150C 2.0 16-LEAD SOIC PACKAGE 1.5 1.0 0.5 8-LEAD SOIC PACKAGE 0 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 AMBIENT TEMPERATURE (C) Figure 6. Maximum Power Dissipation vs. Temperature 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. F | Page 5 of 12 00876-E-004 1 MAXIMUM POWER DISSIPATION (W) 2.5 AD825 TYPICAL PERFORMANCE CHARACTERISTICS 100 20 15 5 RL = 150 10 OUTPUT IMPEDANCE () OUTPUT SWING (V) 10 RL = 1k 0 -5 -10 1 0.1 4 2 6 8 10 12 SUPPLY VOLTAGE (V) 14 16 18 0.01 100 10M 80 35 15 BANDWIDTH 30 UNITY GAIN BANDWIDTH (MHz) 10 VS = 15V 5 VS = 5V 0 -5 VS = 15V -10 25 60 20 PHASE MARGIN 15 40 10 0 100 200 300 400 500 600 700 LOAD RESISTANCE () 800 900 1000 00876-E-006 5 0 -60 -40 -20 0 60 20 40 80 TEMPERATURE (C) 100 120 00876-E-009 OUTPUT SWING (V) 1M Figure 10. Closed-Loop Output Impedance vs. Frequency Figure 7. Output Voltage Swing vs. Supply Voltage -15 10k 100k FREQUENCY (Hz) 1k 00876-E-008 0 PHASE MARGIN (C) -20 00876-E-005 -15 20 140 Figure 11. Unity Gain Bandwidth and Phase Margin vs. Temperature Figure 8. Output Voltage Swing vs. Load Resistance 80 7.0 180 VS = 15V OPEN-LOOP GAIN (dB) +85 6.0 VS = 5V 60 90 50 45 40 0 30 20 5.5 5.0 0 2 4 6 8 10 12 14 SUPPLY VOLTAGE (V) 16 18 20 0 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M Figure 12. Open-Loop Gain and Phase Margin vs. Frequency Figure 9. Quiescent Supply Current vs. Supply Voltage for Various Temperatures Rev. F | Page 6 of 12 00876-E-010 10 00876-E-007 SUPPLY CURRENT (mA) 6.5 OPEN-LOOP PHASE (Degrees) 135 70 -40 +25 AD825 30 80 OPEN-LOOP GAIN (dB) 75 VS = 15V 70 VS = 5V 60 10 1k 10k LOAD RESISTANCE () 00876-E-011 65 20 RL = 150 10 0 10k 100k 1M FREQUENCY (Hz) 00876-E-014 OUTPUT VOLTAGE (V p-p) RL = 1k 10M Figure 16. Large Signal Frequency Response; G = +2 Figure 13. Open-Loop Gain vs. Load Resistance 10 200 0 180 160 -10 -PSRR -30 +PSRR -40 -50 -60 140 0.01% 100 0.1% 60 -80 20 100k 1M FREQUENCY (Hz) 10M 00876-E-012 40 10k 0.1% 80 -70 -90 0.01% 120 0 10 8 6 4 2 0 -2 -4 OUTPUT SWING (0 to V) -6 -8 -10 00876-E-015 SETTLING TIME (ns) PSR (dB) -20 Figure 17. Output Swing and Error vs. Settling Time Figure 14. Power Supply Rejection vs. Frequency 130 -50 120 -55 110 -60 DISTORTION (dB) 100 90 80 VS = 5V 70 60 SECOND -65 THIRD -70 -75 50 -80 30 10 100 1k 10k 100k FREQUENCY (Hz) 1M 10M -85 100k Figure 15. Common-Mode Rejection vs. Frequency 1M FREQUENCY (Hz) Figure 18. Harmonic Distortion vs. Frequency Rev. F | Page 7 of 12 10M 00876-E-016 40 00876-E-013 CMR (dB) VS = 15V AD825 +VS 160 10F 15V 0.01F 5V 120 2 7 HP PULSE (LS) AD825 VIN OR 3 4 FUNCTION (SS) GENERATOR 50 100 80 -VS 6 VOUT TEKTRONIX P6204 FET PROBE TEKTRONIX 7A24 PREAMP 0.01F 00876-E-020 SLEW RATE (V/s) 140 RL 10F 60 Figure 22. Noninverting Amplifier Connection 40 0 -60 -40 -20 60 20 40 80 TEMPERATURE (C) 0 100 120 00876-E-017 20 140 Figure 19. Slew Rate vs. Temperature 2 5V 1 100ns 0 -2 -3 -4 VOUT VIN -5 VS -6 5V 10MHz 15V 21MHz 0.1dB FLATNESS -7 00876-E-021 GAIN (dB) -1 10k 100k 1M 10M FREQUENCY (Hz) 00876-E-018 5V -8 1k Figure 23. Noninverting Large Signal Pulse Response, RL = 1 k Figure 20. Closed-Loop Gain vs. Frequency, Gain = +1 2 200mV 50ns 1 0 -2 -3 VIN 1k 1k -4 VOUT -5 VS -7 5V 7.7MHz 15V 9.8MHz -8 1k 10k 200mV 100k 1M FREQUENCY (Hz) 10M 00876-E-022 0.1dB FLATNESS -6 00876-E-019 GAIN (dB) -1 Figure 24. Noninverting Small Signal Pulse Response, RL = 1 k Figure 21. Closed-Loop Gain vs. Frequency, Gain = -1 Rev. F | Page 8 of 12 AD825 00876-E-023 5V 5V Figure 25. Noninverting Large Signal Pulse Response, RL = 150 Figure 28. Inverting Large Signal Pulse Response, RL = 1 k 50ns 200mV 00876-E-024 200mV 200mV 200mV Figure 26. Noninverting Small Signal Pulse Response, RL = 150 Figure 29. Inverting Small Signal Pulse Response, RL = 1 k 1k +VS 10F 0.01F HP PULSE VIN GENERATOR RIN 1k 7 2 AD825 6 3 VOUT TEKTRONIX P6204 FET PROBE TEKTRONIX 7A24 PREAMP 0.01F -VS RL 10F 00876-E-025 4 50 50ns Figure 27. Inverting Amplifier Connection Rev. F | Page 9 of 12 00876-E-027 5V 100ns 00876-E-026 100ns 5V AD825 DRIVING CAPACITIVE LOADS VPOS The internal compensation of the AD825, together with its high output current drive, permits excellent large signal performance while driving extremely high capacitive loads. NEG 1k +VS POS 10F 0.01F HP PULSE VIN GENERATOR RIN 1k CF 7 2 AD825 6 3 VOUT TEKTRONIX P6204 FET PROBE VOUT TEKTRONIX 7A24 PREAMP -VS CL 00876-E-028 0.01F 50 10F VNEG Figure 30. Inverting Amplifier Driving a Capacitive Load 00876-E-030 4 Figure 32. Simplified Schematic 5V 500ns The capacitor, CF, in the output stage, enables the AD825 to drive heavy capacitive loads. For light loads, the gain of the output buffer is close to unity, CF is bootstrapped, and not much happens. As the capacitive load is increased, the gain of the output buffer is decreased and the bandwidth of the amplifier is reduced through a portion of CF adding to the dominant pole. As the capacitive load is further increased, the amplifier's bandwidth continues to drop, maintaining the stability of the AD825. OUTPUT 5V 00876-E-029 INPUT Figure 31. Inverting Amplifier Pulse Response While Driving a 400 pF Capacitive Load THEORY OF OPERATION INPUT CONSIDERATION The AD825 with its unique input stage ensures no phase reversal for signals as large as or even larger than the supply voltages. Also, layout considerations of the input transistors ensure functionality even with a large differential signal. The AD825 is a low cost, wideband, high performance FET input operational amplifier. With its unique input stage design, the AD825 ensures no phase reversal, even for inputs that exceed the power supply voltages, and its output stage is designed to drive heavy capacitive or resistive loads with small changes relative to no load conditions. The need for a low noise input stage calls for a larger FET transistor. One should consider the additional capacitance that is added to ensure stability. When filters are designed with the AD825, one needs to consider the input capacitance (5 pF to 6 pF) of the AD825 as part of the passive network. The AD825 (Figure 32) consists of common-drain, commonbase FET input stage driving a cascoded, common-base matched NPN gain stage. The output buffer stage uses emitter followers in a Class AB amplifier that can deliver large current to the load while maintaining low levels of distortion. The AD825 is a low input bias current FET amplifier. Its high frequency response makes it useful in applications, such as photodiode interfaces, filters, and audio circuits. When designing high frequency circuits, some special precautions are in order. Circuits must be built with short interconnects, and resistances should have low inductive paths to ground. Power supply leads should be bypassed to common as close as possible to the amplifier pins. Ceramic capacitors of 0.1 F are recommended. GROUNDING AND BYPASSING Rev. F | Page 10 of 12 AD825 SECOND-ORDER LOW-PASS FILTER C1 24pF A second-order Butterworth low-pass filter can be implemented using the AD825 as shown in Figure 33. The extremely low bias currents of the AD825 allow the use of large resistor values and, consequently, small capacitor values without concern for developing large offset errors. Low current noise is another factor in permitting the use of large resistors without having to worry about the resultant voltage noise. VIN R1 9.31k R2 9.31k C2 6pF +5V C3 0.1F VOUT AD825 00876-E-031 C4 0.1F -5V C1 = 1.414 2 f CUTOFF R1 0.707 C2 ( farads ) = 2 f CUTOFF R1 R1 = R2 = User Selected (Typically 10 k to 100 k ) Figure 33. Second-Order Butterworth Low-Pass Filter 0 HIGH FREQUENCY REJECTION (dB) With the values shown, the corner frequency will be 1 MHz. The equations for component selection are shown below. Note that the noninverting input (and the inverting input) has an input capacitance of 6 pF. As a result, the calculated value of C1 (12 pF) is reduced to 6 pF. -10 -20 -30 -40 -50 -60 -70 A plot of the filter frequency response is shown in Figure 34; better than 40 dB of high frequency rejection is provided. 10k 100k 1M FREQUENCY (Hz) 10M 100M Figure 34. Frequency Response of Second-Order Butterworth Filter Rev. F | Page 11 of 12 00876-E-032 -80 AD825 OUTLINE DIMENSIONS 10.50 (0.4134) 10.10 (0.3976) 5.00 (0.1968) 4.80 (0.1890) 8 5 4.00 (0.1574) 3.80 (0.1497) 1 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 9 16 7.60 (0.2992) 7.40 (0.2913) 6.20 (0.2440) 5.80 (0.2284) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE 8 1 1.27 (0.0500) BSC 0.50 (0.0196) x 45 0.25 (0.0099) 0.30 (0.0118) 0.10 (0.0039) 8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122) 10.65 (0.4193) 10.00 (0.3937) 2.65 (0.1043) 2.35 (0.0925) SEATING PLANE 0.75 (0.0295) x 45 0.25 (0.0098) 8 0.33 (0.0130) 0 0.20 (0.0079) 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 COMPLIANT TO JEDEC STANDARDS MS-013AA 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 35. 8-Lead Standard Small Outline Package [SOIC] Narrow Body (R-8) Dimensions shown in millimeters (inches) Figure 36. 16-Lead Standard Small Outline Package [SOIC] Wide Body (R-16) Dimensions shown in millimeters (inches) ORDERING GUIDE Model AD825AR AD825AR-REEL AD825AR-REEL7 AD825AR-16 AD825AR-16-REEL AD825AR-16-REEL7 AD825ARZ-161 AD825ARZ-16-REEL1 AD825ARZ-16-REEL71 AD825ACHIPS 1 1.27 (0.0500) 0.40 (0.0157) Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 8-Lead SOIC 8-Lead SOIC, 13" Tape and Reel 8-Lead SOIC, 7" Tape and Reel 16-Lead SOIC 16-Lead SOIC, 13" Tape and Reel 16-Lead SOIC, 7" Tape and Reel 16-Lead SOIC 16-Lead SOIC, 13" Tape and Reel 16-Lead SOIC, 7" Tape and Reel Die Z = Pb-free part. (c) 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C00876-0-10/04(F) Rev. F | Page 12 of 12 Package Option R-8 R-8 R-8 R-16 R-16 R-16 R-16 R-16 R-16