Programmable Gain Precision Difference Amplifier AD8271 FUNCTIONAL BLOCK DIAGRAM With no external resistors Difference amplifier, gains of 1/2, 1, or 2 Single-ended amplifier: over 40 different gains Set reference voltage at midsupply Excellent ac specifications 15 MHz bandwidth 30 V/s slew rate High accuracy dc performance 0.08% maximum gain error 10 ppm/C maximum gain drift 80 dB minimum CMRR (gain of 2) 10-lead MSOP package Supply current: 2.6 mA Supply range: 2.5 V to 18 V 10k 10k P1 1 10 10k 10k 2 9 N2 P2 P3 3 P4 4 N3 10k 20k 8 OUT 20k -VS 5 N1 7 AD8271 6 +VS 07363-001 FEATURES Figure 1. APPLICATIONS ADC driver Instrumentation amplifier building blocks Level translators Automatic test equipment High performance audio Sine/cosine encoders GENERAL DESCRIPTION Table 1. Difference Amplifiers by Category The AD8271 is a low distortion, precision difference amplifier with internal gain setting resistors. With no external components, it can be configured as a high performance difference amplifier with gains of 1/2, 1, or 2. It can also be configured in over 40 singleended configurations, with gains ranging from -2 to +3. High Speed AD8270 AD8273 AD8274 AMP03 The AD8271 comes in a 10-lead MSOP package. The AD8271 operates on both single and dual supplies and requires only a 2.6 mA maximum supply current. It is specified over the industrial temperature range of -40C to +85C and is fully RoHS compliant. High Voltage AD628 AD629 Single-Supply Unidirectional AD8202 AD8203 Single-Supply Bidirectional AD8205 AD8206 AD8216 For a dual channel version of the AD8271, see the AD8270 data sheet. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2009 Analog Devices, Inc. All rights reserved. AD8271 TABLE OF CONTENTS Features .............................................................................................. 1 Circuit Information.................................................................... 15 Applications ....................................................................................... 1 Driving the AD8271................................................................... 15 Functional Block Diagram .............................................................. 1 Power Supplies ............................................................................ 15 General Description ......................................................................... 1 Input Voltage Range ................................................................... 15 Revision History ............................................................................... 2 Applications Information .............................................................. 16 Specifications..................................................................................... 3 Difference Amplifier Configurations ...................................... 16 Difference Amplifier Configurations ........................................ 3 Single-Ended Configurations ................................................... 17 Absolute Maximum Ratings............................................................ 6 Kelvin Measurement .................................................................. 18 Thermal Resistance ...................................................................... 6 Instrumentation Amplifier........................................................ 18 Maximum Power Dissipation ..................................................... 6 Driving Cabling .......................................................................... 19 ESD Caution .................................................................................. 6 Driving an ADC ......................................................................... 19 Pin Configuration and Function Description .............................. 7 Outline Dimensions ....................................................................... 20 Typical Performance Characteristics ............................................. 8 Ordering Guide .......................................................................... 20 Operational Amplifier Plots ...................................................... 14 Theory of Operation ...................................................................... 15 REVISION HISTORY 1/09--Revision 0: Initial Version Rev. 0 | Page 2 of 20 AD8271 SPECIFICATIONS DIFFERENCE AMPLIFIER CONFIGURATIONS VS = 5 to 15 V, VREF = 0 V, G = 1, RLOAD = 2 k, TA = 25C, specifications referred to input (RTI), unless otherwise noted. Table 2. Parameter DYNAMIC PERFORMANCE Bandwidth Slew Rate Settling Time to 0.01% Settling Time to 0.001% NOISE/DISTORTION Harmonic Distortion + Noise Voltage Noise 1 GAIN Gain Error Gain Drift Gain Nonlinearity INPUT CHARACTERISTICS Offset 2 Average Temperature Drift Common-Mode Rejection Ratio Power Supply Rejection Ratio Input Voltage Range 3 Common-Mode Resistance 4 Bias Current OUTPUT CHARACTERISTICS Output Swing Short-Circuit Current Limit Conditions Min B Grade Typ Max 15 30 700 550 750 600 VS = 15, 10 V step on output VS = 5, 5 V step on output VS = 15, 10 V step on output VS = 5, 5 V step on output VS = 15, f = 1 kHz, VOUT = 10 V p-p, RLOAD = 600 VS = 5, f = 1 kHz, VOUT = 10 V p-p, RLOAD = 600 f = 0.1 Hz to 10 Hz f = 1 kHz A Grade Typ Max 15 30 700 550 750 600 800 650 900 750 dB 141 141 dB 1.5 38 1.5 38 V p-p nV/Hz TA = -40C to +85C DC to 1 kHz 300 2 92 2 -VS - 0.4 0.02 2 1 1 600 74 10 +VS + 0.4 Inputs grounded 300 2 92 2 -VS - 0.4 10 -13.8 -13.7 -4 -3.9 +13.8 +13.7 +4 +3.9 100 60 2.3 TA = -40C to +85C 1 0.05 10 % ppm/C ppm 1000 V V/C dB V/V V k nA 10 +VS + 0.4 10 500 POWER SUPPLY Supply Current MHz V/s ns ns ns ns 110 1 1 VS = 15 VS = 15, TA = -40C to +85C VS = 5 VS = 5, TA = -40C to +85C Sourcing Sinking 800 650 900 750 Unit 110 VOUT = 10 V p-p TA = -40C to +85C VOUT = 10 V p-p, RLOAD = 10 k, 2 k, 600 80 Min 500 -13.8 -13.7 -4 -3.9 +13.8 +13.7 +4 +3.9 V V V V mA mA 2.6 3.2 mA mA 100 60 2.6 3.2 2.3 Includes amplifier voltage and current noise, as well as noise of internal resistors. Includes input bias and offset errors. 3 At voltages beyond the rails, internal ESD diodes begin to turn on. In some configurations, the input voltage range may be limited by the internal op amp (see the Input Voltage Range section for details). 4 Internal resistors, trimmed to be ratio matched, have 20% absolute accuracy. Common-mode resistance was calculated with both inputs in parallel. The commonmode impedance at only one input is 2x the resistance listed. 2 Rev. 0 | Page 3 of 20 AD8271 VS = 5 to 15 V, VREF = 0 V, G = 1/2, RLOAD = 2 k, TA = 25C, specifications referred to input (RTI), unless otherwise noted. Table 3. Parameter DYNAMIC PERFORMANCE Bandwidth Slew Rate Settling Time to 0.01% Settling Time to 0.001% NOISE/DISTORTION Harmonic Distortion + Noise Voltage Noise 1 GAIN Gain Error Gain Drift Gain Nonlinearity INPUT CHARACTERISTICS Offset 2 Average Temperature Drift Common-Mode Rejection Ratio Power Supply Rejection Ratio Input Voltage Range 3 Common-Mode Resistance 4 Bias Current OUTPUT CHARACTERISTICS Output Swing Short-Circuit Current Limit Conditions Min B Grade Typ Max 20 30 700 550 750 600 VS = 15, 10 V step on output VS = 5, 5 V step on output VS = 15, 10 V step on output VS = 5, 5 V step on output VS = 15, f = 1 kHz, VOUT = 10 V p-p, RLOAD = 600 VS = 5, f = 1 kHz, VOUT = 10 V p-p, RLOAD = 600 f = 0.1 Hz to 10 Hz f = 1 kHz A Grade Typ Max 20 30 700 550 750 600 800 650 900 750 dB 101 101 dB 2 52 2 52 V p-p nV/Hz TA = -40C to +85C DC to 1 kHz 450 3 86 2 -VS - 0.4 0.04 2 1 200 1000 70 10 +VS + 0.4 Inputs grounded 450 3 86 2 -VS - 0.4 7.5 -13.8 -13.7 -4 -3.9 +13.8 +13.7 +4 +3.9 100 60 2.3 TA = -40C to +85C 1 0.08 10 % ppm/C ppm 1500 V V/C dB V/V V k nA 10 +VS + 0.4 7.5 500 POWER SUPPLY Supply Current MHz V/s ns ns ns ns 74 0.5 200 VS = 15 VS = 15, TA = -40C to +85C VS = 5 VS = 5, TA = -40C to +85C Sourcing Sinking 800 650 900 750 Unit 74 VOUT = 10 V p-p TA = -40C to +85C VOUT = 10 V p-p, RLOAD = 10 k, 2 k, 600 74 Min 500 -13.8 -13.7 -4 -3.9 +13.8 +13.7 +4 +3.9 V V V V mA mA 2.6 3.2 mA mA 100 60 2.6 3.2 2.3 Includes amplifier voltage and current noise, as well as noise of internal resistors. Includes input bias and offset errors. 3 At voltages beyond the rails, internal ESD diodes begin to turn on. In some configurations, the input voltage range may be limited by the internal op amp (see the Input Voltage Range section for details). 4 Internal resistors, trimmed to be ratio matched, have 20% absolute accuracy. Common-mode resistance was calculated with both inputs in parallel. The commonmode impedance at only one input is 2x the resistance listed. 2 Rev. 0 | Page 4 of 20 AD8271 VS = 5 to 15 V, VREF = 0 V, G = 2, RLOAD = 2 k, TA = 25C, specifications referred to input (RTI), unless otherwise noted. Table 4. Parameter DYNAMIC PERFORMANCE Bandwidth Slew Rate Settling Time to 0.01% Settling Time to 0.001% NOISE/DISTORTION Harmonic Distortion + Noise Voltage Noise 1 GAIN Gain Error Gain Drift Gain Nonlinearity INPUT CHARACTERISTICS Offset 2 Average Temperature Drift Common-Mode Rejection Ratio Power Supply Rejection Ratio Input Voltage Range 3 Common-Mode Resistance 4 Bias Current OUTPUT CHARACTERISTICS Output Swing Short-Circuit Current Limit Conditions Min B Grade Typ Max 10 30 700 550 750 600 VS = 15, 10 V step on output VS = 5, 5 V step on output VS = 15, 10 V step on output VS = 5, 5 V step on output VS = 15, f = 1 kHz, VOUT = 10 V p-p, RLOAD = 600 VS = 5, f = 1 kHz, VOUT = 10 V p-p, RLOAD = 600 f = 0.1 Hz to 10 Hz f = 1 kHz A Grade Typ Max 10 30 700 550 750 600 800 650 900 750 dB 112 112 dB 1 26 1 26 V p-p nV/Hz TA = -40C to +85C DC to 1 kHz 225 1.5 98 2 -VS - 0.4 0.04 2 1 50 500 78 10 +VS + 0.4 Inputs grounded 225 1.5 98 2 -VS - 0.4 7.5 -13.8 -13.7 -4 -3.9 +13.8 +13.7 +4 +3.9 100 60 2.3 TA = -40C to +85C 1 0.08 10 % ppm/C ppm 750 V V/C dB V/V V k nA 10 +VS + 0.4 7.5 500 POWER SUPPLY Supply Current MHz V/s ns ns ns ns 86 0.5 50 VS = 15 VS = 15, TA = -40C to +85C VS = 5 VS = 5, TA = -40C to +85C Sourcing Sinking 800 650 900 750 Unit 86 VOUT = 10 V p-p TA = -40C to +85C VOUT = 10 V p-p, RLOAD = 10 k, 2 k, 600 84 Min 500 -13.8 -13.7 -4 -3.9 +13.8 +13.7 +4 +3.9 V V V V mA mA 2.6 3.2 mA mA 100 60 2.6 3.2 2.3 Includes amplifier voltage and current noise, as well as noise of internal resistors. Includes input bias and offset errors. 3 At voltages beyond the rails, internal ESD diodes begin to turn on. In some configurations, the input voltage range may be limited by the internal op amp (see the Input Voltage Range section for details). 4 Internal resistors, trimmed to be ratio matched, have 20% absolute accuracy. Common-mode resistance was calculated with both inputs in parallel. The commonmode impedance at only one input is 2x the resistance listed. 2 Rev. 0 | Page 5 of 20 AD8271 ABSOLUTE MAXIMUM RATINGS MAXIMUM POWER DISSIPATION Input Voltage Range Storage Temperature Range Specified Temperature Range Package Glass Transition Temperature (TG) ESD Human Body Model Charge Device Model Machine Model Rating 18 V See derating curve in Figure 2 +VS + 0.4 V to -VS - 0.4 V -65C to +130C -40C to +85C 150C 1 kV 1 kV 0.1 kV 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. The maximum safe power dissipation for the AD8271 is limited by the associated rise in junction temperature (TJ) on the die. At approximately 150C, which is the glass transition temperature, the properties of the plastic change. Even temporarily exceeding this temperature limit may change the stresses that the package exerts on the die, permanently shifting the parametric performance of the amplifiers. Exceeding a temperature of 150C for an extended period of time can cause changes in silicon devices, potentially resulting in a loss of functionality. The AD8271 has built-in short-circuit protection that limits the output current to approximately 100 mA (see Figure 22 for more information). Although the short-circuit condition itself does not damage the part, the heat generated by the condition can cause the part to exceed its maximum junction temperature, with corresponding negative effects on reliability. 1.6 THERMAL RESISTANCE Table 6. Thermal Resistance Package Type 10-Lead MSOP JA 141.9 JC 43.7 Unit C/W 1.2 1.0 0.8 0.6 0.4 0.2 0 -50 The JA values in Table 6 assume a 4-layer JEDEC standard board with zero airflow. TJ MAX = 150C 1.4 -25 0 25 50 75 AMBIENT TEMPERATURE (C) 100 125 07363-102 Parameter Supply Voltage Output Short-Circuit Current MAXIMUM POWER DISSIPATION (W) Table 5. Figure 2. Maximum Power Dissipation vs. Ambient Temperature ESD CAUTION Rev. 0 | Page 6 of 20 AD8271 P1 1 10 N3 P2 2 AD8271 9 N2 P3 3 TOP VIEW (Not to Scale) 8 N1 P4 4 -VS 5 7 OUT 6 +VS 07363-002 PIN CONFIGURATION AND FUNCTION DESCRIPTION Figure 3. Table 7. Pin Function Descriptions Pin No. 1 2 3 Mnemonic P1 P2 P3 4 P4 5 6 7 8 9 10 -VS +VS OUT N1 N2 N3 Description Noninverting Input. A 10 k resistor is connected to the noninverting (+) terminal of the op amp. Noninverting Input. A 10 k resistor is connected to the noninverting (+) terminal of the op amp. Noninverting Input. A 20 k resistor is connected to the noninverting (+) terminal of the op amp. This pin is used as a reference voltage input in many configurations. Noninverting Input. A 20 k resistor is connected to the noninverting (+) terminal of the op amp. This pin is used as a reference voltage input in many configurations. Negative Supply. Positive Supply. Output. Inverting Input. A 10 k resistor is connected to the inverting (-) terminal of the op amp. Inverting Input. A 10 k resistor is connected to the inverting (-) terminal of the op amp. Inverting Input. A 10 k resistor is connected to the inverting (-) terminal of the op amp. Rev. 0 | Page 7 of 20 AD8271 TYPICAL PERFORMANCE CHARACTERISTICS VS = 15 V, TA = 25C, difference amplifier configuration, unless otherwise noted. 70 180 150 60 50 40 120 CMRR (V/V) 90 60 30 +0.6V/V/C 20 10 0 -0.1V/V/C -10 -20 07363-107 30 0 -200 -100 0 100 REPRESENTATIVE SAMPLES -30 -40 -50 200 CMMR (V/V) Figure 4. Typical Distribution of CMRR, Gain = 1 -30 -10 10 30 50 70 TEMPERATURE (C) 90 110 130 07363-004 NUMBER OF UNITS GAIN = 1 N = 989 MEAN = -29 SD = 43 Figure 7. CMRR vs. Temperature, Normalized at 25C, Gain = 1 300 GAIN = 1 NUMBER OF UNITS 150 120 90 60 2.2V/C 100 0 -100 -1000 -500 0 500 2.8V/C -200 07363-108 30 0 200 SYSTEM OFFSET VOLTAGE (V) N = 989 MEAN = -306 SD = 229 REPRESENTATIVE SAMPLES -300 -50 1000 SYSTEM OFFSET VOLTAGE (V) -30 -10 10 30 50 70 TEMPERATURE (C) 90 110 130 07363-005 180 Figure 8. System Offset vs. Temperature, Normalized at 25C, Referred to Output, Gain = 1 Figure 5. Typical Distribution of System Offset, Gain = 1 200 240 GAIN = 1 N = 1006 MEAN = 0.003 SD = 0.005 150 GAIN ERROR (V/V) 180 150 120 90 60 07363-109 30 0 -0.04 -0.02 0 0.02 1.7ppm/C 100 50 0 -50 0.5ppm/C -100 REPRESENTATIVE SAMPLES -150 -50 0.04 GAIN ERROR (%) Figure 6. Typical Distribution of Gain Error, Gain = 1 -30 -10 10 30 50 70 TEMPERATURE (C) 90 110 130 Figure 9. Gain Error vs. Temperature, Normalized at 25C, Gain = 1 Rev. 0 | Page 8 of 20 07363-006 NUMBER OF UNITS 210 AD8271 VS = 15 V, TA = 25C, difference amplifier configuration, unless otherwise noted. 6 20 (0, +5) 15 (-7.5, +7.5) (+7.5, +7.5) 5 0 -5 -10 (-7.5, -7.5) (+7.5, -7.5) -15 4 (-4.3, +2.85) (+4.3, +2.85) (0, +2.5) 2 (-1.6, +1.7) 0 OUTPUT VOLTAGE (V) (-1.6, -1.7) -2 10 (0, -2.5) -2.85) -4 (-4.3, +2.85) -6 -5 Figure 10. Common-Mode Input Voltage vs. Output Voltage, Gain = 1/2, 15 V Supplies (+4.3, -2.85) -4 -3 -2 -1 0 1 2 OUTPUT VOLTAGE (V) COMMON-MODE INPUT VOLTAGE (V) (+2.5, +2.5) (0, +2.5) (-1.25, -1.25) (+1.25, +1.25) VS = 2.5 VS = 5 0 (-1.25, -1.25) -2 (+1.25, -1.25) (0, -2.5) (-2.5, -2.5) (+2.5, -2.5) (-14.3, +11.4) (+14.3, +11.4) (-14.3, -11.4) (+14.3, -11.4) 10 5 0 -5 -10 -15 (0, -15) (0, -5) -1 0 1 OUTPUT VOLTAGE (V) 2 3 07363-008 -2 -20 -20 Figure 11. Common-Mode Input Voltage vs. Output Voltage, Gain = 1/2, 5 V and 2.5 V Supplies -15 -10 -5 0 5 OUTPUT VOLTAGE (V) 10 15 20 07363-011 2 15 Figure 14. Common-Mode Input Voltage vs. Output Voltage, Gain = 2, 15 V Supplies 6 20 (0, +5) (0, +15) (-14.3, +7.85) COMMON-MODE INPUT VOLTAGE (V) 15 (+14.3, +7.85) 5 0 -5 (-14.3, -7.85) (+14.3, -7.85) -15 (-4, +4) (+4, +4) 4 (0, +2.5) (-1.6, +2.1) VS = 2.5 -2 (-1.6, -2.1) -10 -5 0 5 OUTPUT VOLTAGE (V) (+1.6, -2.1) (0, -2.5) -4 (-4, -4) (+4, -4) (0, -5) 10 15 20 -6 -5 07363-009 -15 VS = 5 0 (0, -15) -20 -20 (+1.6, +2.1) 2 Figure 12. Common-Mode Input Voltage vs. Output Voltage, Gain =1, 15 V Supplies -4 -3 -2 -1 0 1 2 OUTPUT VOLTAGE (V) 3 4 5 Figure 15. Common-Mode Input Voltage vs. Output Voltage, Gain = 2, 5 V and 2.5 V Supplies Rev. 0 | Page 9 of 20 07363-012 COMMON-MODE INPUT VOLTAGE (V) (-2.5, +2.5) -6 -3 COMMON-MODE INPUT VOLTAGE (V) 5 (0, +15) 4 -10 4 20 (0, +5) 10 3 Figure 13. Common-Mode Input Voltage vs. Output Voltage, Gain = 1, 5 V and 2.5 V Supplies 6 -4 (+1.6, -1.7) (0, -5) 5 07363-007 -5 VS = 5 0 (0, -15) -20 -10 (+1.6, +1.7) VS = 2.5 07363-010 10 COMMON-MODE INPUT VOLTAGE (V) COMMON-MODE INPUT VOLTAGE (V) (0, +15) AD8271 VS = 15 V, TA = 25C, difference amplifier configuration, unless otherwise noted. 10 140 GAIN = 2, 1/2 GAIN = 2 120 5 POSITIVE PSRR (dB) GAIN = 1 GAIN = 1/2 -5 -10 -15 GAIN = 1 80 60 40 20 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 0 10 07363-018 -20 100 100 100 100k 1M Figure 19. Positive PSRR vs. Frequency Figure 16. Gain vs. Frequency 140 100 90 1k 10k FREQUENCY (Hz) 07363-015 GAIN (dB) 0 GAIN = 2, 1/2 GAIN = 2, 1/2 120 GAIN = 1 NEGATIVE PSRR (dB) 80 CMRR (dB) 70 60 50 40 30 100 GAIN = 1 80 60 40 20 20 1k 10k 100k FREQUENCY (Hz) 1M 10M 0 10 100 Figure 17. CMRR vs. Frequency 1M 10 4 VS = 15V 3 NONLINEARITY (1ppm/DIV) 28 OUTPUT VOLTAGE SWING (V p-p) 100k Figure 20. Negative PSRR vs. Frequency 32 24 20 16 12 VS = 5V 8 10V p-p INPUT GAIN = 1 RLOAD = 10k, 2k, 600 2 1 0 -1 -2 -3 4 1k 10k 100k FREQUENCY (Hz) 1M 10M -4 -10 07363-017 0 100 1k 10k FREQUENCY (Hz) 07363-016 100 07363-019 0 10 07363-136 10 Figure 18. Output Voltage Swing vs. Large-Signal Frequency Response Rev. 0 | Page 10 of 20 -8 -6 -4 -2 0 2 4 TEMPERATURE (C) 6 Figure 21. Gain Nonlinearity, Gain = 1 8 AD8271 VS = 15 V, TA = 25C, difference amplifier configuration, unless otherwise noted. 120 VS = 15V 100 0pF 60 18pF 100pF 40 50mV/DIV SHORT-CIRCUIT CURRENT (mA) ISHORT+ 80 20 0 -20 ISHORT- -40 -60 -10 10 30 50 70 TEMPERATURE (C) 90 110 130 1s/DIV Figure 22. Short-Circuit Current vs. Temperature Figure 25. Small-Signal Step Response, Gain = 1/2 +125C VS = 15V +VS - 2 -40C +25C 220pF +85C 0pF 33pF +VS - 4 50mV/DIV OUTPUT VOLTAGE SWING (V) +VS 07363-024 -30 07363-118 -80 -100 -50 0 +125C +85C -VS + 4 +25C 1k RLOAD () 10k 07363-022 -40C -VS 200 1s/DIV Figure 23. Output Voltage Swing vs. RLOAD Figure 26. Small-Signal Step Response, Gain = 1 -40C +25C VS = 15V +VS - 3 470pF 0pF 100pF +125C 50ms/DIV +VS - 6 +85C 0 +125C -VS + 6 +85C +25C -40C -VS 0 20 40 60 80 CURRENT (mA) 100 1s/DIV Figure 27. Small-Signal Step Response, Gain = 2 Figure 24. Output Voltage Swing vs. Current (IOUT) Rev. 0 | Page 11 of 20 07363-026 -VS + 3 07363-023 OUTPUT VOLTAGE SWING (V) +VS 07363-025 -VS + 2 AD8271 VS = 15 V, TA = 25C, difference amplifier configuration, unless otherwise noted. 160 GAIN = 1/2 140 VS = 5V OVERSHOOT (%) 120 VS = 10V VS = 2.5V 2V/DIV 100 80 60 VS = 18V 40 07363-127 VS = 15V 0 0 10 20 30 40 50 60 70 CAPACITIVE LOAD (pF) 80 90 100 07363-030 20 1s/DIV Figure 28. Small-Signal Overshoot vs. Capacitive Load, Gain = 1/2 Figure 31. Large-Signal Pulse Response, Gain = 1/2 80 GAIN = 1 70 VS = 10V VS = 5V 50 VS = 2.5V 2V/DIV OVERSHOOT (%) 60 40 30 VS = 18V 20 07363-128 VS = 15V 0 0 50 100 150 CAPACITIVE LOAD (pF) 200 07363-031 10 1s/DIV Figure 29. Small-Signal Overshoot vs. Capacitive Load, Gain = 1 Figure 32. Large-Signal Pulse Response, Gain = 1 80 GAIN = 2 70 50 2V/DIV OVERSHOOT (%) 60 VS = 10V 40 VS = 5V 30 VS = 2.5V 20 07363-129 VS = 18V 10 0 50 100 150 200 250 300 350 CAPACITIVE LOAD (pF) 400 450 07363-132 VS = 15V 0 1s/DIV Figure 30. Small-Signal Overshoot vs. Capacitive Load, Gain = 2 Figure 33. Large-Signal Pulse Response, Gain = 2 Rev. 0 | Page 12 of 20 AD8271 VS = 15 V, TA = 25C, difference amplifier configuration, unless otherwise noted. 0.1 45 RLOAD = 100k RLOAD = 2k RLOAD = 600 GAIN = 1/2 35 +SR 0.01 30 THD + N (%) 25 -SR 20 15 GAIN = 2 0.001 10 GAIN = 1 125 0.0001 10 07363-130 115 95 105 85 75 65 55 45 35 25 5 15 -15 -25 -35 -45 0 -5 5 07363-133 OUTPUT SLEW RATE (V/s) 40 100 1k 10k 100k FREQUENCY (Hz) TEMPERATURE (C) Figure 37. THD + N vs. Frequency Figure 34. Output Slew Rate vs. Temperature 1 GAIN = 1 f = 1kHz RLOAD = 600 RLOAD = 2k RLOAD = 100k 0.1 THDN + N (%) GAIN = 2 100 GAIN = 1 0.01 0.001 10 100 1k FREQUENCY (Hz) 10k 100k 0.0001 5 0 Figure 35. Voltage Noise Spectral Density vs. Frequency, Referred to Output 0.1 1V/DIV 1s/DIV AMPLITUDE (% OF FUNDAMENTAL) 07363-042 GAIN = 1/2 20 25 Figure 38. THD + N vs. Output Amplitude, Gain = 1 GAIN = 2 GAIN = 1 10 15 OUTPUT AMPLITUDE (dBu) 0.01 HD2, HD2, HD2, HD3, HD3, HD3, RLOAD RLOAD RLOAD RLOAD RLOAD RLOAD = 100k = 2k = 600 = 100k = 2k = 600 GAIN = 1 VOUT = 10V p-p 0.001 0.0001 0.00001 10 100 1k 10k 100k FREQUENCY (Hz) Figure 39. Harmonic Distortion Products vs. Frequency, Gain = 1 Figure 36. 0.1 Hz to 10 Hz Voltage Noise, Referred to Output Rev. 0 | Page 13 of 20 07363-135 1 07363-134 GAIN = 1/2 10 07363-041 VOLTAGE NOISE SPECTRAL DENSITY (nV/Hz) 1k AD8271 OPERATIONAL AMPLIFIER PLOTS VS = 15 V, TA = 25C, unless otherwise noted. 1 2 3 4 5 6 TIME (sec) 7 8 9 10 0.1 07363-044 0 1 Figure 40. Change in Op Amp Offset Voltage vs. Warm-Up Time 1s/DIV 10 100 1k FREQUENCY (Hz) 10k Figure 42. Current Noise Spectral Density vs. Frequency 07363-028 50pA/DIV 1 Figure 41. 0.1 Hz to 10 Hz Current Noise Rev. 0 | Page 14 of 20 100k 07363-029 OFFSET (10V/DIV) CURRENT NOISE SPECTRAL DENSITY (pA/Hz) 10 AD8271 THEORY OF OPERATION P4 4 -VS 5 9 N2 of the AD8271 depend on the matching of its resistors. Even source resistance of a few ohms can have a substantial effect on these specifications. 10k 10k 20k 10k 8 N1 POWER SUPPLIES 20k 7 OUT AD8271 6 +VS Figure 43. Functional Block Diagram CIRCUIT INFORMATION The AD8271 consists of a high precision, low distortion op amp and seven trimmed resistors. These resistors can be connected to create a wide variety of amplifier configurations, including difference, noninverting, and inverting configurations. The resistors on the chip can be connected in parallel for a wider range of options. Using the on-chip resistors of the AD8271 provides the designer with several advantages over a discrete design. DC Performance Much of the dc performance of op amp circuits depends on the accuracy of the surrounding resistors. The resistors on the AD8271 are laid out to be tightly matched. The resistors of each part are laser trimmed and tested for their matching accuracy. Because of this trimming and testing, the AD8271 can guarantee high accuracy for specifications, such as gain drift, common-mode rejection, and gain error. A stable dc voltage should be used to power the AD8271. Noise on the supply pins can adversely affect performance. A bypass capacitor of 0.1 F should be placed between each supply pin and ground, as close as possible to each supply pin. A tantalum capacitor of 10 F should also be used between each supply and ground. It can be farther away from the supply pins and, typically, it can be shared by other precision integrated circuits. The AD8271 is specified at 15 V and 5 V, but it can be used with unbalanced supplies, as well. For example, -VS = 0 V, +VS = 20 V. The difference between the two supplies must be kept below 36 V. INPUT VOLTAGE RANGE The AD8271 has a true rail-to-rail input range for the majority of applications. Because most AD8271 configurations divide down the voltage before they reach the internal op amp, the op amp sees only a fraction of the input voltage. Figure 44 shows an example of how the voltage division works in the difference amplifier configuration. R2 (V ) R1 + R2 +IN R4 R3 R1 AC Performance Because feature size is much smaller in an integrated circuit than on a printed circuit board (PCB), the corresponding parasitics are also smaller. The smaller feature size helps the ac performance of the AD8271. For example, the positive and negative input terminals of the AD8271 op amp are not pinned out intentionally. By not connecting these nodes to the traces on the PCB, the capacitance remains low, resulting in both improved loop stability and common-mode rejection over frequency. Production Costs Because one part, rather than several discrete components, is placed on the PCB, the board can be built more quickly and efficiently. Size The AD8271 fits an op amp and seven resistors in one MSOP package. DRIVING THE AD8271 The AD8271 is easy to drive, with all configurations presenting at least several kilohms (k) of input resistance. The AD8271 should be driven with a low impedance source: for example, another amplifier. The gain accuracy and common-mode rejection R2 R2 (V ) R1 + R2 +IN 07363-033 P3 3 N3 07363-032 P2 2 10 10k 10k P1 1 Figure 44. Voltage Division in the Difference Amplifier Configuration The internal op amp voltage range may be relevant in the following applications, and calculating the voltage at the internal op amp is advised. * * * Difference amplifier configurations using supply voltages of less than 4.5 V Difference amplifier configurations with a reference voltage near the rail Single-ended amplifier configurations For correct operation, the input voltages at the internal op amp must stay within 1.5 V of either supply rail. Voltages beyond the supply rails should not be applied to the part. The part contains ESD diodes at the input pins, which conduct if voltages beyond the rails are applied. Currents greater than 5 mA may damage these diodes and the part. For a similar part that can operate with voltages beyond the rails, see the AD8274 data sheet. Rev. 0 | Page 15 of 20 AD8271 APPLICATIONS INFORMATION The AD8271 can also be referred to a combination of reference voltages. For example, the reference can be set at 2.5 V, using just 5 V and GND. Some of the possible configurations are shown in Figure 48 through Figure 50. Note that the output is not internally tied to a feedback path, so any of the 10 k resistors on the inverting input can be used in the feedback network. This flexibility allows for more efficient board layout options. DIFFERENCE AMPLIFIER CONFIGURATIONS The AD8271 can be placed in difference amplifier configurations with gains of 1/2, 1, and 2. Figure 45 through Figure 47 show sample difference amplifier configurations referenced to ground. N3 10k 10k 2 9 -IN P3 3 P4 GND = 8 +IN 10k 3 +VS 5k GND OUT +IN 1 P2 2 NC P3 3 GND P4 4 9 NC +IN OUT 8 OUT 20k -IN = N1 10k 20k +IN 10k N2 10k 10k 10k NC 10k 10k 10k P4 P2 2 3 GND P4 4 N1 10k = 8 +IN OUT 20k 5k NC -IN = N1 8 +IN OUT 20k 10k P2 10k 10k 7 2 N3 10k 10 10k P3 -VS 3 P4 +VS GND 10k OUT N2 10k 10k +IN 9 -IN 5k 10k OUT 10k N2 9 2 OUT 7 AD8271 20k 10k 1 +IN 9 20k 10k 10k 07363-054 P1 10k -IN P3 4 -IN 10 Figure 49. Gain = 1 Difference Amplifier, Referenced to Midsupply 10 -IN N3 10k +VS + -VS N3 N2 2 AD8271 07363-055 1 +IN 3 +VS Figure 46. Gain = 1 Difference Amplifier, Referenced to Ground 10k 5k +VS + -VS 2 -VS 10k 7 10k 10k OUT 10k P3 GND P1 +IN OUT 7 1 P2 AD8271 -IN = N1 8 20k P1 -IN 10 20k 10k 5k 10k Figure 48. Gain = 1/2 Difference Amplifier, Referenced to Midsupply N3 10k 10k 10k AD8271 Figure 45. Gain = 1/2 Difference Amplifier, Referenced to Ground P1 P4 4 AD8271 10k N2 9 P3 7 -IN 10 2 -VS 10k N3 10k 10k 1 P2 OUT 20k 4 N1 10k 20k +IN 5k N2 4 20k N1 10k = 8 +IN OUT 20k 5k 5k OUT 10k 7 +VS + -VS AD8271 Figure 47. Gain = 2 Difference Amplifier, Referenced to Ground 2 Figure 50. Gain = 2 Difference Amplifier, Referenced to Midsupply Table 8. Pin Connections for Difference Amplifier Configurations Gain and Reference Gain of 1/2, Referenced to Ground Gain of 1/2, Referenced to Midsupply Gain of 1, Referenced to Ground Gain of 1, Referenced to Midsupply Gain of 2, Referenced to Ground Gain of 2, Referenced to Midsupply Pin 1 (P1) +IN +IN +IN +IN +IN +IN Pin 2 (P2) GND -VS NC NC +IN +IN 07363-057 P2 P1 -IN 10 Pin 3 (P3) GND +VS GND -VS GND -VS Rev. 0 | Page 16 of 20 Configuration Pin 4 Pin 8 (P4) (N1) GND OUT +VS OUT GND OUT +VS OUT GND OUT +VS OUT Pin 9 (N2) OUT OUT NC NC -IN -IN Pin 10 (N3) -IN -IN -IN -IN -IN -IN 07363-058 10k 10k 1 07363-053 P1 +IN 07363-056 The resistors and connections provided on the AD8271 offer abundant versatility through the variety of configurations that are possible. AD8271 SINGLE-ENDED CONFIGURATIONS The AD8271 can be configured for a wide variety of single-ended configurations with gains ranging from -2 to +3 (see Table 9). Table 9. Selected Single-Ended Configurations Electrical Performance Signal Gain -2 -1.5 -1.4 -1.25 -1 -0.8 -0.667 -0.6 -0.5 -0.333 -0.25 -0.2 -0.125 +0.1 +0.2 +0.25 +0.3 +0.333 +0.375 +0.4 +0.5 +0.5 +0.6 +0.6 +0.625 +0.667 +0.7 +0.75 +0.75 +0.8 +0.9 +1 +1 +1 +1.125 +1.2 +1.2 +1.25 +1.333 +1.5 +1.5 +1.6 +1.667 +1.8 +2 +2.25 +2.4 +2.5 +3 1 2 3 Op Amp Closed-Loop Gain 3 3 3 3 3 3 2 2 2 2 1.5 1.5 1.5 1.5 2 1.5 1.5 2 1.5 2 3 1.5 3 1.5 1.5 2 1.5 3 1.5 2 1.5 1.5 1.5 3 1.5 3 1.5 1.5 2 3 1.5 2 2 3 2 3 3 3 3 Configuration Input Resistance 5 k 4.8 k 5 k 5.333 k 5 k 5.556 k 8 k 8.333 k 8.889 k 7.5 k 8 k 8.333 k 8.889 k 8.333 k 10 k 24 k 25 k 24 k 26.67 k 25 k 24 k 15 k 25 k 16.67 k 16 k 15 k 16.67 k 26.67 k 13.33 k 16.67 k 16.67 k 15 k >1 G >1 G 26.67 k 16.67 k 25 k 24 k 15 k 13.33 k >1 G 25 k 24 k 16.67 k >1 G 26.67 k 25 k 24 k >1 G Pin 10 1 IN IN IN IN IN IN IN IN IN IN OUT OUT OUT OUT IN OUT OUT GND OUT GND GND OUT GND OUT OUT GND OUT GND OUT GND OUT OUT OUT IN OUT GND OUT OUT GND GND OUT GND GND GND GND GND GND GND GND A 10 k resistor is connected to the inverting (-) terminal of the op amp. A 10 k resistor is connected to the noninverting (+) terminal of the op amp. A 20 k resistor is connected to the noninverting (+) terminal of the op amp. Rev. 0 | Page 17 of 20 Pin 91 IN IN IN IN IN IN NC NC NC NC IN IN IN IN NC GND GND NC GND NC GND GND GND GND IN NC IN GND GND NC GND GND IN IN GND GND GND GND NC GND GND NC NC GND NC GND GND GND GND Pin 81 OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT OUT Pin 1 2 GND GND GND GND GND IN GND GND GND GND GND GND GND IN GND GND GND GND GND GND GND GND GND IN NC GND IN GND GND IN GND IN IN IN NC IN IN IN IN GND IN IN IN GND IN NC IN IN IN Pin 22 GND GND GND NC GND GND GND GND NC GND GND GND NC GND IN GND GND GND NC GND GND GND GND GND IN GND IN NC IN GND IN IN IN IN IN GND IN IN IN IN IN IN IN IN IN IN IN IN IN Pin 3 3 GND GND NC GND IN NC GND NC GND IN GND NC GND NC NC GND NC GND GND NC GND IN NC NC IN IN NC GND GND NC NC GND IN IN IN NC NC IN GND GND IN NC IN NC IN IN NC IN IN Pin 43 GND IN IN IN IN GND IN IN IN IN IN IN IN GND IN IN IN IN IN IN IN IN IN GND GND IN GND IN IN GND IN GND IN IN GND GND GND GND GND IN IN GND GND IN IN GND GND GND IN AD8271 The AD8271 Specifications section and Typical Performance Characteristics section show the performance of the part primarily when it is in the difference amplifier configuration. To estimate the performance of the part in a single-ended configuration, refer to the difference amplifier configuration with the corresponding closed-loop gain (see Table 10). Table 10. Closed-Loop Gain of the Difference Amplifiers Closed-Loop Gain 1.5 2 3 +IN FORCE RL 1k 10k Figure 52. Connecting Both the Output and Feedback at the Load Minimizes Error Due to Wire Resistance INSTRUMENTATION AMPLIFIER The AD8271 can be used as a building block for high performance instrumentation amplifiers. For example, Figure 53 shows how to build an ultralow noise instrumentation amplifier using the AD8599 dual op amp. External resistors RG and RFx provide gain; therefore, the output is 2R VOUT = (V + IN - V - IN )1 + Fx RG (G AD 8271 ) AD8599 -IN A2 10k RF1 10k 2k RG 20 OUT 10k AD8271 RF2 10k 2k REF KELVIN MEASUREMENT AD8599 +IN In the case where the output load is located remotely or at a distance from the AD8271, as shown in Figure 51, wire resistance can actually cause significant errors at the load. For optimal noise performance, it is desirable to have a high gain at the input stage using low value gain-setting resistors, as shown in this particular example. With less than 2 nV/Hz input-referred noise (see Figure 54) at ~10 mA supply current, the AD8271 and AD8599 combination offers an in-amp with a fine balance of critical specifications: a gain bandwidth product of 10 MHz, low bias current, low offset drift, high CMRR, and high slew rate. 07363-149 Figure 51. Wire Resistance Causes Errors at Load Voltage Since the output of the AD8271 is not internally tied to any of the feedback resistors, Kelvin type measurements are possible because the op amp output and feedback can both be connected closer to the load (Figure 52). The Kelvin sensing on the feedback minimizes error at the load caused by voltage drops across the wire resistance. This technique is most effective in reducing errors for loads less than 10 k. As the load resistance increases, the error due to the wire resistance becomes less significant. Because it adds the sense wire resistance to the feedback resistor, a trade-off of the Kelvin connection is that it can degrade commonmode rejection, especially over temperature. For sense wire resistance less than 1 , it is typically not an issue. If commonmode performance is critical, two amplifier stages can be used: the first stage removes common-mode interference, and the second stage performs the Kelvin drive. Rev. 0 | Page 18 of 20 10.0 9.0 8.0 7.0 6.0 5.0 4.0 G = 201 BANDWIDTH LIMIT 3.0 2.0 07363-151 10k +IN VOLTAGE NOISE SPECTRAL DENSITY (nV/Hz) RW (WIRE RESISTANCE) RL 1k VS = 15V A2 Figure 53.Ultralow Noise Instrumentation Amplifier Using AD8599 Configured for Gain = 201 10k 10k Rw 10k The AD8271 is designed to be stable for loop gains of 1.5 and greater. Because a typical voltage follower configuration has a loop gain of 1, it may be unstable. Several stable configurations for gain of 1 are listed in Table 9. 10k Rw 10k -IN Gain of 1 Configuration -IN SENSE 07363-153 Difference Amplifier Gain 0.5 1 2 10k 07363-150 Many signal gains have more than one configuration choice, which allows freedom in choosing the op amp closed-loop gain. In general, for designs that need to be stable with a large capacitive load on the output, choose a configuration with high loop gain. Otherwise, choose a configuration with low loop gain, because these configurations typically have lower noise, lower offset, and higher bandwidth. 1.0 0 1 10 100 1k FREQUENCY (Hz) 10k 100k Figure 54. Ultralow Noise In-Amp Voltage Noise Spectral Density vs. Frequency, Referred to Input AD8271 DRIVING CABLING DRIVING AN ADC Because the AD8271 can drive large voltages at high output currents and slew rates, it makes an excellent cable driver. It is good practice to put a small value resistor between the AD8271 output and cable, since capacitance in the cable can cause peaking or instability in the output response. A resistance of 20 or higher is recommended. The AD271 high slew rate and drive capability, combined with its dc accuracy, make it a good ADC driver. The AD8271 can drive single-ended input ADCs. Many converters require the output to be buffered with a small value resistor combined with a high quality ceramic capacitor. See the relevant converter data sheet for more details. AD8271 07363-148 (SINGLE OUT) Figure 55. Driving Cabling Rev. 0 | Page 19 of 20 AD8271 OUTLINE DIMENSIONS 3.10 3.00 2.90 10 3.10 3.00 2.90 1 6 5.15 4.90 4.65 5 PIN 1 0.50 BSC 0.95 0.85 0.75 0.15 0.05 1.10 MAX 0.33 0.17 SEATING PLANE 0.23 0.08 8 0 0.80 0.60 0.40 COPLANARITY 0.10 COMPLIANT TO JEDEC STANDARDS MO-187-BA Figure 56. 10-Lead Mini Small Outline Package [MSOP] (RM-10) Dimensions are shown in millimeters ORDERING GUIDE Model AD8271ARMZ 1 AD8271ARMZ-R71 AD8271ARMZ-RL1 AD8271BRMZ1 AD8271BRMZ-R71 AD8271BRMZ-RL1 1 Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package Description 10-Lead MSOP 10-Lead MSOP, 7" Tape and Reel 10-Lead MSOP, 13" Tape and Reel 10-Lead MSOP 10-Lead MSOP, 7" Tape and Reel 10-Lead MSOP, 13" Tape and Reel Z = RoHS Compliant Part. (c)2009 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07363-0-1/09(0) Rev. 0 | Page 20 of 20 Package Option RM-10 RM-10 RM-10 RM-10 RM-10 RM-10 Branding Y1E Y1E Y1E Y1G Y1G Y1G