Precision, Very Low Noise, Low Input Bias Current Operational Amplifiers AD8671/AD8672/AD8674 Data Sheet FEATURES PIN CONFIGURATIONS Very low noise: 2.8 nV/√Hz, 77 nV p-p Wide bandwidth: 10 MHz Low input bias current: 12 nA max Low offset voltage: 75 μV max High open-loop gain: 120 dB min Low supply current: 3 mA typ per amplifier Dual-supply operation: ±5 V to ±15 V Unity-gain stable No phase reversal NC 1 8 AD8671 NC V+ TOP VIEW 6 OUT (Not to Scale) V– 4 5 NC –IN 2 7 NC = NO CONNECT 03718-B-001 +IN 3 Figure 1. 8-Lead SOIC_N (R-8) and 8-Lead MSOP (RM-8) 8 AD8672 V+ OUT B TOP VIEW 6 –IN B (Not to Scale) V– 4 5 +IN B –IN A 2 APPLICATIONS 7 +IN A 3 PLL filters Filters for GPS Instrumentation Sensors and controls Professional quality audio 03718-B-003 OUT A 1 Figure 2. 8-Lead SOIC-N (R-8) and 8-Lead MSOP (RM-8) OUT A 1 14 OUT D –IN A 2 13 –IN D 12 +IN D +IN A 3 GENERAL DESCRIPTION AD8674 TOP VIEW 11 V– +IN B 5 (Not to Scale) 10 +IN C The AD8671/AD8672/AD8674 are very high precision amplifiers featuring very low noise, very low offset voltage and drift, low input bias current, 10 MHz bandwidth, and low power consumption. Outputs are stable with capacitive loads of over 1000 pF. Supply current is less than 3 mA per amplifier at 30 V. The AD8671/AD8672/AD8674’s combination of ultralow noise, high precision, speed, and stability is unmatched. The MSOP version of the AD8671/AD8672 requires only half the board space of comparable amplifiers. Applications for these amplifiers include high quality PLL filters, precision filters, medical and analytical instrumentation, precision power supply controls, ATE, data acquisition, and precision controls as well as professional quality audio. –IN B 6 9 –IN C OUT B 7 8 OUT C 03718-B-005 V+ 4 Figure 3. 14-Lead SOIC_N (R-14) and 14-Lead TSSOP (RU-14) The AD8671, AD8672, and AD8674 are members of a growing series of low noise op amps offered by Analog Devices, Inc. Table 1. Voltage Noise Package Single Dual Quad 0.9 nV AD797 1.1 nV AD8597 AD8599 1.8 nV ADA4004-1 ADA4004-2 ADA4004-4 2.8 nV AD8675 AD8676 3.8 nV AD8671 AD8672 AD8674 The AD8671/AD8672 are specified over the extended industrial temperature range (−40°C to +125°C), and the AD8674 is specified over the industrial temperature range (−40°C to +85°C). The AD8671/AD8672 are available in the 8-lead SOIC and 8-lead MSOP packages. The AD8674 is available in 14-lead SOIC and 14-lead TSSOP packages. Surface-mount devices in MSOP packages are available in tape and reel only. Rev. F Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 ©2004–2013 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com AD8671/AD8672/AD8674 Data Sheet TABLE OF CONTENTS Specifications..................................................................................... 3 Output Phase Reversal ............................................................... 12 Electrical Characteristics, ±5.0 V ............................................... 3 Total Noise vs. Source Resistance............................................. 12 Electrical Characteristics, ±15 V ................................................ 4 Total Harmonic Distortion (THD) and Noise ....................... 13 Absolute Maximum Ratings ............................................................ 5 Driving Capacitive Loads .......................................................... 13 ESD Caution .................................................................................. 5 GPS Receiver ............................................................................... 14 Typical Performance Characteristics ............................................. 6 Band-Pass Filter .......................................................................... 14 Applications ..................................................................................... 11 PLL Synthesizers and Loop Filters ........................................... 14 Power Dissipation Calculations ................................................ 11 Outline Dimensions ....................................................................... 15 Unity-Gain Follower Applications ........................................... 11 Ordering Guide .......................................................................... 17 REVISION HISTORY 3/13—Rev. E to Rev. F 4/04—Rev. A to Rev. B Added Figure 7.............................................................................. 6 Updated Outline Dimensions ................................................... 15 Changes to Ordering Guide ...................................................... 17 Changes to Figure 32.................................................................. 11 Changes to Figures 36, 37, and 38 ............................................ 12 6/10—Rev. D to Rev. E 1/04—Rev. 0 to Rev. A Added Table 1 and Preceding Sentence ..................................... 1 Added AD8672 and AD8674 parts .............................. Universal Changes to Specifications .............................................................3 Deleted Figure 3.............................................................................6 Changes to Figures 7, 8, and 9 .....................................................6 Changes to Figure 37.................................................................. 12 Added new Figure 32 ................................................................. 10 12/09—Rev. C to Rev. D Changes to Features and General Description Sections.......... 1 Changes to Absolute Maximum Ratings Section, Table 3, and Table 4 ................................................................................ 5 Added Power Dissipation Calculations Section ..................... 11 Updated Outline Dimensions ................................................... 15 Changes to Ordering Guide ...................................................... 17 6/05—Rev. B to Rev. C Changes to Figure 6 ...................................................................... 1 Updated Outline Dimensions ................................................... 14 Changes to Ordering Guide ...................................................... 16 Rev. F | Page 2 of 20 Data Sheet AD8671/AD8672/AD8674 SPECIFICATIONS ELECTRICAL CHARACTERISTICS, ±5.0 V VS = ±5.0 V, VCM = 0 V, TA = 25°C, unless otherwise noted. Table 2. Parameter INPUT CHARACTERISTICS Offset Voltage Offset Voltage Drift AD8671 AD8672/AD8674 Input Bias Current Symbol Conditions VOS ∆VOS/∆T –40°C < TA < +125°C –40°C < TA < +125°C IB +25°C < TA < +125°C –40°C < TA < +125°C Input Offset Current IOS +25°C < TA < +125°C –40°C < TA < +125°C Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Input Capacitance, Common Mode Input Capacitance, Differential Mode Input Resistance, Common Mode Input Resistance, Differential Mode OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Voltage High Output Voltage Low Output Current POWER SUPPLY Power Supply Rejection Ratio AD8671/AD8672 AD8674 Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product NOISE PERFORMANCE Peak-to-Peak Noise Voltage Noise Density Current Noise Density Channel Separation AD8672/AD8674 Min CMRR AVO CINCM CINDM RIN RINDM VCM = –2.5 V to +2.5 V RL = 2 kΩ, VO = –3 V to +3 V VOH VOL VOH VOL IOUT RL = 2 kΩ, –40°C to +125°C RL = 2 kΩ, –40°C to +125°C RL = 600 Ω RL = 600 Ω PSRR VS = ±4 V to ±18 V –12 –20 –40 –12 –20 –40 –2.5 100 1000 +3.8 +3.7 110 106 Typ Max Unit 20 30 75 125 µV µV 0.3 0.3 +3 +5 +8 +6 +6 +8 0.5 0.8 +12 +20 +40 +12 +20 +40 +2.5 µV/°C µV/°C nA nA nA nA nA nA V dB V/mV pF pF GΩ MΩ 120 6000 6.25 7.5 3.5 15 +4.0 –3.9 +3.9 –3.8 ±10 130 115 3 ISY VO = 0 V –40°C < TA < +125°C SR tS RL = 2 kΩ To 0.1% (4 V step, G = 1) To 0.01% (4 V step, G = 1) 4 1.4 5.1 10 en p-p en in 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz 77 2.8 0.3 CS f = 1 kHz f = 10 kHz –130 –105 GBP Rev. F | Page 3 of 20 –3.8 –3.7 3.5 4.2 V V V V mA dB dB mA mA V/µs µs µs MHz 100 3.8 nV p-p nV/√Hz pA/√Hz dB dB AD8671/AD8672/AD8674 Data Sheet ELECTRICAL CHARACTERISTICS, ±15 V VS = ±15 V, VCM = 0 V, TA = 25°C, unless otherwise noted. Table 3. Parameter INPUT CHARACTERISTICS Offset Voltage Offset Voltage Drift AD8671 AD8672/AD8674 Input Bias Current Symbol Conditions VOS ∆VOS/∆T –40°C < TA < +125°C –40°C < TA < +125°C IB +25°C < TA < +125°C –40°C < TA < +125°C Input Offset Current IOS +25°C < TA < +125°C –40°C < TA < +125°C Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Input Capacitance, Common Mode Input Capacitance, Differential Mode Input Resistance, Common Mode Input Resistance, Differential Mode OUTPUT CHARACTERISTICS Output Voltage High Output Voltage Low Output Voltage High Output Voltage Low Output Current Short Circuit Current POWER SUPPLY Power Supply Rejection Ratio AD8671/AD8672 AD8674 Supply Current/Amplifier DYNAMIC PERFORMANCE Slew Rate Settling Time Gain Bandwidth Product NOISE PERFORMANCE Peak-to-Peak Noise Voltage Noise Density Current Noise Density Channel Separation AD8672/AD8674 Min CMRR AVO CINCM CINDM RIN RINDM VCM = –12 V to +12 V RL = 2 kΩ, VO = –10 V to +10 V VOH VOL VOH VOL IOUT ISC RL = 2 kΩ, –40°C to +125°C RL = 2 kΩ, –40°C to +125°C RL = 600 Ω RL = 600 Ω PSRR VS = ±4 V to ±18 V –12 –20 –40 –12 –20 –40 –12 100 1000 +13.2 +11 110 106 Typ Max Unit 20 30 75 125 µV µV 0.3 0.3 +3 +5 +8 +6 +6 +8 0.5 0.8 +12 +20 +40 +12 +20 +40 +12 µV/°C µV/°C nA nA nA nA nA nA V dB V/mV pF pF GΩ MΩ 120 6000 6.25 7.5 3.5 15 +13.8 –13.8 +12.3 –12.4 ±20 ±30 130 115 3 ISY VO = 0 V –40°C <TA < +125°C SR tS RL = 2 kΩ To 0.1% (10 V step, G = 1) To 0.01% (10 V step, G = 1) 4 2.2 6.3 10 en p-p en in 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz 77 2.8 0.3 CS f = 1 kHz f = 10 kHz –130 –105 GBP Rev. F | Page 4 of 20 –13.2 –11 3.5 4.2 V V V V mA mA dB dB mA mA V/µs µs µs MHz 100 3.8 nV p-p nV/√Hz pA/√Hz dB dB Data Sheet AD8671/AD8672/AD8674 ABSOLUTE MAXIMUM RATINGS Table 4. 1 Parameter Supply Voltage Input Voltage Differential Input Voltage Output Short-Circuit Duration Storage Temperature Range All Packages Operating Temperature Range 8-Lead Packages 14-Lead Packages Junction Temperature Range All Packages Lead Temperature Range (Soldering, 60 sec) 1 Rating 36 V VS– to VS+ ±0.7 V Indefinite –65°C to +150°C –40°C to +125°C –40°C to +85°C –65°C to +150°C 300°C Absolute maximum ratings apply at 25°C, unless otherwise noted. 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. See the Applications section for a related discussion on power. Table 5. Package Characteristics Package Type 8-Lead MSOP (RM) 8-Lead SOIC_N (R) 14-Lead SOIC_N (R) 14-Lead TSSOP (RU) 1 θJA 1 142 120 90 112 θJC 44 43 36 35 Unit °C/W °C/W °C/W °C/W θJA is specified for the worst-case conditions, that is., θJA is specified for the device soldered on a 4-layer circuit board for surface-mount packages. 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 20 AD8671/AD8672/AD8674 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS 10 32 28 CURRENT NOISE DENSITY (pA/√Hz) VOLTAGE NOISE DENSITY (nV/√Hz) VS = ±15V 24 20 16 12 8 1 0 10 20 30 60 50 40 FREQUENCY (Hz) 70 80 90 100 0.1 1 1k 10k Figure 7. Current Noise Density VS = ±15 V 45 31.5 VS = ±15V 40 27.0 VS = ±5V TA = 25°C 35 NUMBER OF AMPLIFIERS 22.5 18.0 13.5 9.0 4.5 30 25 20 15 10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FREQUENCY (kHz) 0 5 10 15 20 25 30 35 40 45 VOS (µV) Figure 5. Voltage Noise Density vs. Frequency Figure 8. Input Offset Voltage Distribution 17.5 35 VS = ±15V VS = ±15V TA = 25°C 15.0 30 NUMBER OF AMPLIFIERS 12.5 10.0 7.5 5.0 2.5 25 20 15 10 5 0 1 2 3 4 5 6 7 8 FREQUENCY (kHz) 9 10 03718-B-009 0 –35 –30 –25 –20 –15 –10 –5 0 03718-B-010 0 03718-B-008 5 0 –35 –30 –25 –20 –15 –10 –5 0 5 10 15 20 25 30 35 40 45 50 VOS (µV) Figure 9. Input Offset Voltage Distribution Figure 6. Voltage Noise Density vs. Frequency Rev. F | Page 6 of 20 03718-B-011 VOLTAGE NOISE DENSITY (nV/√Hz) 100 FREQUENCY (Hz) Figure 4. Voltage Noise Density vs. Frequency VOLTAGE NOISE DENSITY (nV/√Hz) 10 03718-112 0 03718-B-007 4 Data Sheet AD8671/AD8672/AD8674 16 4.0 15 3.8 14 3.6 12 ISY (mA) VOS (µV) 13 11 10 3.4 3.2 3.0 VS = ±5V VS = ±15V 9 2.8 8 VS = ±15V 2.6 7 125 TEMPERATURE (°C) 03718-B-012 85 25 2.4 –40 25 85 03718-B-015 VS = ±5V 6 –40 125 TEMPERATURE (°C) Figure 10. Input Offset Voltage vs. Temperature Figure 13. Supply Current vs. Temperature 5.0 14.5 VS = ±5V VS = ±15V RL = 2kΩ 4.5 14.0 4.0 +IB 13.5 OUTPUT VOLTAGE (V) 3.5 2.5 2.0 –IB 1.5 1.0 13.0 RL = 600Ω 12.5 12.0 11.5 11.0 0.5 25 85 125 TEMPERATURE (°C) 03718-B-013 10.5 0 –40 10.0 –40 25 85 125 TEMPERATURE (°C) Figure 11. Input Bias Current vs. Temperature 03718-B-016 IB (nA) 3.0 Figure 14. Output Voltage High vs. Temperature 2.5 –11.0 VS = ±15V VS = ±15V 2.0 –11.5 –IB OUTPUT VOLTAGE (V) 1.0 0.5 +IB 0 –0.5 –12.5 RL = 600Ω –13.0 –13.5 RL = 2kΩ 25 85 TEMPERATURE (°C) 125 Figure 12. Input Bias Current vs. Temperature –14.5 –40 25 85 TEMPERATURE (°C) Figure 15. Output Voltage Low vs. Temperature Rev. F | Page 7 of 20 125 03718-B-017 –1.0 –40 –12.0 –14.0 03718-B-014 IB (nA) 1.5 AD8671/AD8672/AD8674 Data Sheet GAIN 225 90 180 80 135 30 90 20 PHASE 10 45 0 0 70 60 50 –10 –45 –20 –90 20 –30 –135 10 30 –180 –40 100k 1M FREQUENCY (Hz) AVO = 10 40 0 100 03718-B-018 OPEN-LOOP GAIN (dB) 40 100 10M AVO = 100 1k 10k AVO = 1 100k 1M 10M 100M FREQUENCY (Hz) Figure 19. Output Impedance vs. Frequency Figure 16. Open-Loop Gain and Phase Shift vs. Frequency VSY = ±15V VIN = 4V RL = 2kΩ 30000 ±5V VOLTAGE (1V/DIV) 25000 15000 ±15V 10000 25 85 125 TEMPERATURE (°C) TIME (100µs/DIV) 03718-B-019 0 –40 Figure 20. Large Signal Transient Response Figure 17. Open-Loop Gain vs. Temperature VSY = ±15V VIN = 200mV p-p RL = 2kΩ 50 30 20 VOLTAGE (50mV/DIV) 40 VSY = ±15V VIN = 10mV RL = ∞ CL = 20pF AV = 100 03718-B-022 5000 AV = 10 10 AV = 1 0 –10 –20 –40 –50 1k 10k 100k 1M 10M FREQUENCY (Hz) 100M TIME (10ms/DIV) Figure 21. Small Signal Transient Response Figure 18. Closed-Loop Gain vs. Frequency Rev. F | Page 8 of 20 03718-B-023 –30 03718-B-020 CLOSED-LOOP GAIN (dB) AVO (V/mV) 20000 03718-B-021 50 270 IMPEDANCE (Ω) VSY = ±15V RL = 10kΩ CL = 20pF FM = 59° OPEN-LOOP PHASE (dB) 60 Data Sheet AD8671/AD8672/AD8674 160 60 VSY = ±15V 140 50 120 –OS 100 40 CMRR (dB) 30 20 80 60 40 20 0 10 +OS 1k 10k CAPACITANCE (pF) 03718-B-024 –20 0 100 –40 10 100 10k 1k 100k 1M 10M 100M FREQUENCY (Hz) 03718-B-027 SMALL SIGNAL OVERSHOOT (%) VS = ±15 Figure 22. Small Signal Overshoot vs. Load Capacitance Figure 25. CMRR vs. Frequency VSY = ±15V 140 120 0V 100 VIN PSRR (dB) VOLTAGE (200mV/DIV) 160 VS = ±15V VIN = 200mV p-p AV = –100 RL = 10k 80 60 –PSRR 40 +PSRR 20 VOUT 0 0V TIME (4s/DIV) –40 10 100 1k 10k 100k 1M 10M FREQUENCY (Hz) 03718-B-028 03718-B-025 –20 Figure 26. PSRR vs. Frequency Figure 23. Positive Overdrive Recovery 135 VIN 134 133 PSRR (dB) 0V 132 131 130 0V 129 VOUT TIME (4s/DIV) 127 –40 25 85 TEMPERATURE (°C) Figure 27. PSRR vs. Temperature Figure 24. Negative Overdrive Recovery Rev. F | Page 9 of 20 125 03718-B-029 128 03718-B-026 VOLTAGE (200mV/DIV) VS = ±2.5V TO ±18V VSY = ±15V VIN = 200mV p-p AV = –100 RL = 10k AD8671/AD8672/AD8674 Data Sheet 0 VS = ±15V VS = ±15V, ±5V CHANNEL SEPARATION (dB) VOLTAGE NOISE (50nV/DIV) –20 –40 –60 –80 –100 –140 100 1k 10k 100k 1M FREQUENCY (Hz) Figure 29. Channel Separation Figure 28. 0.1 Hz to 10 Hz Input Voltage Noise Rev. F | Page 10 of 20 10M 100M 03718-B-031 TIME (1µs/DIV) 03718-B-030 –120 Data Sheet AD8671/AD8672/AD8674 APPLICATIONS POWER DISSIPATION CALCULATIONS Therefore, the rise above ambient temperature is To achieve low voltage noise in a bipolar op amp, the current must be increased. The emitter-base theoretical voltage noise is approximately 504 mW × 112°C/W = 56°C e n = 10 9 kT 2 nV/ Hz qI C With an ambient temperature of 50°C, the junction temperature is 106°C. This is less than the specified absolute maximum junction temperature, but for systems with long product lifetimes (years), this should be considered carefully. To achieve the low voltage noise of 2.8 nV/√Hz, the input stage current is higher than most op amps with an equivalent gain bandwidth product. The thermal noise of a 1 kΩ resistor is 4 nV/√Hz, which is higher than the voltage noise of AD8671 family. Low voltage noise requires using low values of resistors, so low voltage noise op amps should have good drive capability, such as a 600 Ω load. This means that the second stage and output stage are also biased at higher currents. As a result, the supply current of a single op amp is 3.5 mA maximum at room temperature. Note that these calculations do not include the additional dissipation caused by the load current on each op amp. Possible solutions to reduce junction temperature include system level considerations such as fans, Peltier thermoelectric coolers, and heat pipes. Board considerations include operation on lower voltages, such as ±12 V or ±5 V, and using two dual op amps instead of one quad op amp. If the extremely low voltage noise and high gain bandwidth is not required, using other quad op amps, such as ADA4091-4, OP4177, ADA4004-4, OP497, or AD704 can be considered. Junction temperature has a direct affect on reliability. For more information, visit the following Analog Devices, Inc., website: http://www.analog.com/en/quality-and-reliability/reliabilitydata/content/index.html UNITY-GAIN FOLLOWER APPLICATIONS MTTF and FIT calculations can be done based on the junction temperature and IC process. Use the following equation to determine the junction temperature: TJ = TA + PD × θJA For the AD8671 single in the 8-lead MSOP package, the thermal resistance, θJA, is 142°C/W. If the ambient temperature is 30°C and the supply voltages are ±12 V, the power dissipation is 24 V × 3.5 mA = 84 mW When large transient pulses (>1 V) are applied at the positive terminal of amplifiers (such as the OP27, LT1007, OPA227, and AD8671) with back-to-back diodes at the input stage, the use of a resistor in the feedback loop is recommended to avoid having the amplifier load the signal generator. The feedback resistor, RF, should be at least 500 Ω. However, if large values must be used for RF, a small capacitor, CF, should be inserted in parallel with RF to compensate for the pole introduced by the input capacitance and RF. Figure 30 shows the uncompensated output response with a 10 kΩ resistor in the feedback and the compensated response with CF = 15 pF. OUTPUT UNCOMPENSATED Therefore, the rise above ambient temperature is OUTPUT COMPENSATED 84 mW × 142°C/W = 12°C 30 V × 4.2 mA × four op amps = 504 mW Rev. F | Page 11 of 20 CH2 +OVER 7.885% TIME (100ns/DIV) Figure 30. Transient Output Response 03718-B-032 For the AD8674 single in the 14-Lead TSSOP package, the thermal resistance, θJA, is 112°C/W. Although θJA is lower than it is for the 8-lead package, the four op amps are powered simultaneously. If the ambient temperature is 50°C and the supply voltages are ±15 V, the power dissipation is REF1 +OVER 23.23% VOLTAGE (1V/DIV) If the ambient temperature is 30°C, the junction temperature is 42°C. The previously mentioned website that details the effect of the junction temperature on reliability has a calculator that requires only the part number and the junction temperature to determine the process technology. AD8671/AD8672/AD8674 Data Sheet OUTPUT PHASE REVERSAL TOTAL NOISE VS. SOURCE RESISTANCE Phase reversal is a change of polarity in the amplifier transfer function that occurs when the input voltage exceeds the supply voltage. The AD8671/AD8672/AD8674 do not exhibit phase reversal even when the input voltage is 1 V beyond the supplies. The low input voltage noise of the AD8671/AD8672/AD8674 makes them a great choice for applications with low source resistance. However, because they have low input current noise, they can also be used in circuits with substantial source resistance. VSY = ±15V Figure 32 shows the voltage noise, current noise, thermal noise, and total rms noise of the AD8671 as a function of the source resistance. VOLTAGE (1V/DIV) VIN For RS < 475 Ω, the input voltage noise, en, dominates. For 475 Ω < RS < 412 kΩ, thermal noise dominates. For RS > 412 kΩ, the input current noise dominates. VOUT TIME (10s/DIV) Figure 31. Output Phase Reversal C 100 in 10 en_t (4kR ST)1/2 1 10 100 en B A 1k 10k 100k SOURCE RESISTANCE () Figure 32. Noise vs. Source Resistance Rev. F | Page 12 of 20 1M 03718-B-034 TOTAL NOISE (nV/Hz) 03718-B-033 1000 Data Sheet AD8671/AD8672/AD8674 TOTAL HARMONIC DISTORTION (THD) AND NOISE 0.1000 VSY = ±15V RL = 2kΩ CL = 1nF VIN = 100mV AV = +1 VOLTAGE (500mV/DIV) The AD8671/AD8672/AD8674 exhibit low total harmonic distortion (THD) over the entire audio frequency range. This makes them suitable for applications with high closed-loop gains, including audio applications. Figure 33 shows approximately 0.0006% of THD + N in a positive unity gain, the worst-case configuration for distortion. CH2 +OVER 39.80% CH2 –OVER 39.80% 03718-B-036 VS = ±5V VIN = 2.5V RL = 600Ω 0.0500 0.0200 TIME (10ms/DIV) Figure 34. AD8671 Capacitive Load Drive 0.0050 RF 0.0020 LT1007 500Ω 0.0010 0.0005 RG AD8671 500Ω VCC CF 220pF 0.0002 RS 50 100 200 500 1k 2k 5k 10k 20k Hz 03718-B-035 0.0001 20 10Ω CL 1nF RL 2kΩ VIN VEE Figure 33. Total Harmonic Distortion and Noise 03718-B-037 PERCENTAGE 0.0100 Figure 35. Recommended Capacitive Load Circuit DRIVING CAPACITIVE LOADS The AD8671/AD8672/AD8674 can drive large capacitive loads without causing instability. However, when configured in unity gain, driving very large loads can cause unwanted ringing or instability. VOLTAGE (100mV/DIV) CH2 –OVER 6.061% TIME (10ms/DIV) Figure 36. Compensated Load Drive The output response of the circuit is shown in Figure 36. Rev. F | Page 13 of 20 CH2 +OVER 5.051% 03718-B-038 Figure 34 shows the output of the AD8671 with a capacitive load of 1 nF. If heavier loads are used in low closed-loop gain or unity-gain configurations, it is recommended to use external compensation as shown in the circuit in Figure 35. This technique reduces the overshoot and prevents the op amp from oscillation. The trade-off of this circuit is a reduction in output swing. However, a great added benefit stems from the fact that the input signal and the op amp’s noise are filtered, and thus the overall output noise is kept to a minimum. VSY = ±15V RL = 2kΩ CL = 1nF CF = 220pF VIN = 100mV AV = +2 AD8671/AD8672/AD8674 Data Sheet ADC LOW NOISE OP AMP MIXER VGA AD8671 AD831 AD8671 DEMODULATOR LOW-PASS FILTER AD630 AD8610 AD10200 AD8369 03718-B-039 BAND-PASS FILTER CODE GENERATOR Figure 37. Simplified Block Diagram of a GPS Receiver GPS RECEIVER The band-pass response is shown in Figure 39. GPS receivers require low noise to minimize RF effects. The precision of the AD8671 makes it an excellent choice for such applications. Its very low noise and wide bandwidth make it suitable for band-pass and low-pass filters without the penalty of high power consumption. 200µV/DIV VS = ±15V Figure 37 shows a simplified block diagram of a GPS receiver. The next section details the design equations. Filters are useful in many applications; for example, band-pass filters are used in GPS systems, as discussed in the previous section. Figure 38 shows a second-order band-pass KRC filter. 100 1k 10k 100k 2.25kΩ VCC Figure 39. Band-Pass Response PLL SYNTHESIZERS AND LOOP FILTERS C2 C2 1nF Phase-lock loop filters are used in AM/FM modulation. 1nF R2 2.25kΩ RB 18kΩ RA 10kΩ 03718-B-040 VEE Figure 38. Band-Pass KRC Filter The equal component topology yields a center frequency fo = 2 2πRC and Q = Loop filters in PLL design require accuracy and care in their implementation. The AD8671/AD8672/AD8674 are ideal candidates for such filter design; the low offset voltage and low input bias current minimize the output error. In addition to the excellent dc specifications, the AD8671/AD8672/AD8674 have a unique performance at high frequencies; the high open-loop gain and wide bandwidth allow the user to design a filter with a high closed-loop gain if desirable. To optimize the filter design, it is recommended to use small value resistors to minimize the thermal noise. A simple example is shown in Figure 40. 2 4−K PHASE DETECTOR where: K =1+ R1 C1 10kΩ VCC 1nF CHARGE PUMP RB RA VCO D VEE IN Figure 40. PLL Filter Simplified Block Diagram Rev. F | Page 14 of 20 03718-B-042 2.25kΩ VIN 10M 1M Hz R3 R1 03718-B-041 BAND-PASS FILTER Data Sheet AD8671/AD8672/AD8674 OUTLINE DIMENSIONS 5.00 (0.1968) 4.80 (0.1890) 8 4.00 (0.1574) 3.80 (0.1497) 5 1 6.20 (0.2441) 5.80 (0.2284) 4 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) 1.75 (0.0688) 1.35 (0.0532) 0.51 (0.0201) 0.31 (0.0122) COPLANARITY 0.10 SEATING PLANE 0.50 (0.0196) 0.25 (0.0099) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 012407-A COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. Figure 41. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 3.20 3.00 2.80 8 3.20 3.00 2.80 1 5.15 4.90 4.65 5 4 PIN 1 IDENTIFIER 0.65 BSC 0.95 0.85 0.75 15° MAX 1.10 MAX 0.40 0.25 6° 0° 0.23 0.09 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 42. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters Rev. F | Page 15 of 20 0.80 0.55 0.40 10-07-2009-B 0.15 0.05 COPLANARITY 0.10 AD8671/AD8672/AD8674 Data Sheet 8.75 (0.3445) 8.55 (0.3366) 4.00 (0.1575) 3.80 (0.1496) 8 14 1 7 6.20 (0.2441) 5.80 (0.2283) 1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0039) COPLANARITY 0.10 0.50 (0.0197) 0.25 (0.0098) 1.75 (0.0689) 1.35 (0.0531) SEATING PLANE 0.51 (0.0201) 0.31 (0.0122) 45° 8° 0° 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 060606-A COMPLIANT TO JEDEC STANDARDS MS-012-AB 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 43. 14-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-14) Dimensions shown in millimeters and (inches) 5.10 5.00 4.90 14 8 4.50 4.40 4.30 6.40 BSC 1 7 PIN 1 0.65 BSC 1.20 MAX 0.15 0.05 COPLANARITY 0.10 0.30 0.19 0.20 0.09 SEATING PLANE 8° 0° COMPLIANT TO JEDEC STANDARDS MO-153-AB-1 Figure 44. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters Rev. F | Page 16 of 20 0.75 0.60 0.45 061908-A 1.05 1.00 0.80 Data Sheet AD8671/AD8672/AD8674 ORDERING GUIDE Model 1 AD8671ARZ AD8671ARZ-REEL AD8671ARZ-REEL7 AD8671ARMZ AD8671ARMZ-REEL AD8672AR AD8672AR-REEL AD8672AR-REEL7 AD8672ARZ AD8672ARZ-REEL AD8672ARZ-REEL7 AD8672ARMZ AD8672ARMZ-REEL AD8674ARZ AD8674ARZ-REEL AD8674ARZ-REEL7 AD8674ARU AD8674ARUZ AD8674ARUZ-REEL 1 Temperature Range –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +125°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C Package Description 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead MSOP 8-Lead MSOP 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead SOIC_N 14-Lead TSSOP 14-Lead TSSOP 14-Lead TSSOP Z = RoHS Compliant Part. Rev. F | Page 17 of 20 Package Option R-8 R-8 R-8 RM-8 RM-8 R-8 R-8 R-8 R-8 R-8 R-8 RM-8 RM-8 R-14 R-14 R-14 RU-14 RU-14 RU-14 Branding A0V A0V A0W A0W AD8671/AD8672/AD8674 Data Sheet NOTES Rev. F | Page 18 of 20 Data Sheet AD8671/AD8672/AD8674 NOTES Rev. F | Page 19 of 20 AD8671/AD8672/AD8674 Data Sheet NOTES ©2004–2013 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D03718–0–3/13(F) Rev. F | Page 20 of 20