Precision, Very Low Noise, Low Input Bias Current Operational Amplifiers

Data Sheet Precision, Very Low Noise, Low Input Bias Current Operational Amplifiers AD8671/AD8672/AD8674 FEATURES Very low noise: 2.8 nv/ Hz, 77 nv p-p Wide bandwidth: 1 MHz Low input bias current: 12 na max Low offset voltage: 75 μv max High open-loop gain: 12 db min Low supply current: 3 ma typ per amplifier Dual-supply operation: ±5 V to ±15 V Unity-gain stable No phase reversal APPLICATIONS PLL filters Filters for GPS Instrumentation Sensors and controls Professional quality audio GENERAL DESCRIPTION The AD8671/AD8672/AD8674 are very high precision amplifiers featuring very low noise, very low offset voltage and drift, low input bias current, 1 MHz bandwidth, and low power consumption. Outputs are stable with capacitive loads of over 1 pf. Supply current is less than 3 ma per amplifier at 3 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. The AD8671/AD8672 are specified over the extended industrial temperature range ( 4 C to +125 C), and the AD8674 is specified over the industrial temperature range ( 4 C to +85 C). PIN CONFIGURATIONS NC 1 IN 2 +IN 3 V 4 AD8671 TOP VIEW (Not to Scale) NC = NO CONNECT 8 NC 7 V+ 6 OUT 5 NC Figure 1. 8-Lead SOIC_N (R-8) and 8-Lead MSOP (RM-8) OUT A 1 IN A 2 +IN A 3 V 4 AD8672 TOP VIEW (Not to Scale) 3718-B-1 8 V+ 7 OUT B 6 IN B 5 +IN B Figure 2. 8-Lead SOIC-N (R-8) and 8-Lead MSOP (RM-8) OUT A 1 IN A 2 +IN A 3 V+ 4 +IN B 5 IN B 6 OUT B 7 AD8674 TOP VIEW (Not to Scale) 14 OUT D 13 IN D 12 +IN D 11 V 1 +IN C 9 IN C 8 OUT C 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.9 nv 1.1 nv 1.8 nv 2.8 nv 3.8 nv Single AD797 AD8597 ADA44-1 AD8675 AD8671 Dual AD8599 ADA44-2 AD8676 AD8672 Quad ADA44-4 AD8674 3718-B-3 3718-B-5 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 916, Norwood, MA 262-916, U.S.A. Tel: 781.329.47 24 213 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com

AD8671/AD8672/AD8674 TABLE OF CONTENTS Specifications... 3 Electrical Characteristics, ±5. V... 3 Electrical Characteristics, ±15 V... 4 Absolute Maximum Ratings... 5 ESD Caution... 5 Typical Performance Characteristics... 6 Applications... 11 Power Dissipation Calculations... 11 Unity-Gain Follower Applications... 11 Data Sheet Output Phase Reversal... 12 Total Noise vs. Source Resistance... 12 Total Harmonic Distortion (THD) and Noise... 13 Driving Capacitive Loads... 13 GPS Receiver... 14 Band-Pass Filter... 14 PLL Synthesizers and Loop Filters... 14 Outline Dimensions... 15 Ordering Guide... 17 REVISION HISTORY 3/13 Rev. E to Rev. F Added Figure 7... 6 Updated Outline Dimensions... 15 Changes to Ordering Guide... 17 6/1 Rev. D to Rev. E Added Table 1 and Preceding Sentence... 1 12/9 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 4/4 Rev. A to Rev. B Changes to Figure 32... 11 Changes to Figures 36, 37, and 38... 12 1/4 Rev. to Rev. A 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... 1 6/5 Rev. B to Rev. C Changes to Figure 6... 1 Updated Outline Dimensions... 14 Changes to Ordering Guide... 16 Rev. F Page 2 of 2

Data Sheet AD8671/AD8672/AD8674 SPECIFICATIONS ELECTRICAL CHARACTERISTICS, ±5. V VS = ±5. V, VCM = V, T A = 25 C, unless otherwise noted. Table 2. Parameter Symbol Conditions Min Typ Max Unit INPUT CHARACTERISTICS Offset Voltage VOS 2 75 µv 4 C < TA < +125 C 3 125 µv Offset Voltage Drift VOS/ T 4 C < TA < +125 C AD8671.3.5 µv/ C AD8672/AD8674.3.8 µv/ C Input Bias Current IB 12 +3 +12 na +25 C < TA < +125 C 2 +5 +2 na 4 C < TA < +125 C 4 +8 +4 na Input Offset Current IOS 12 +6 +12 na +25 C < TA < +125 C 2 +6 +2 na 4 C < TA < +125 C 4 +8 +4 na Input Voltage Range 2.5 +2.5 V Common-Mode Rejection Ratio CMRR VCM = 2.5 V to +2.5 V 1 12 db Large Signal Voltage Gain AVO RL = 2 kω, VO = 3 V to +3 V 1 6 V/mV Input Capacitance, Common Mode CINCM 6.25 pf Input Capacitance, Differential Mode CINDM 7.5 pf Input Resistance, Common Mode RIN 3.5 GΩ Input Resistance, Differential Mode RINDM 15 MΩ OUTPUT CHARACTERISTICS Output Voltage High VOH RL = 2 kω, 4 C to +125 C +3.8 +4. V Output Voltage Low VOL RL = 2 kω, 4 C to +125 C 3.9 3.8 V Output Voltage High VOH RL = 6 Ω +3.7 +3.9 V Output Voltage Low VOL RL = 6 Ω 3.8 3.7 V Output Current IOUT ±1 ma POWER SUPPLY Power Supply Rejection Ratio PSRR VS = ±4 V to ±18 V AD8671/AD8672 11 13 db AD8674 16 115 db Supply Current/Amplifier ISY VO = V 3 3.5 ma 4 C < TA < +125 C 4.2 ma DYNAMIC PERFORMANCE Slew Rate SR RL = 2 kω 4 V/µs Settling Time ts To.1% (4 V step, G = 1) 1.4 µs To.1% (4 V step, G = 1) 5.1 µs Gain Bandwidth Product GBP 1 MHz NOISE PERFORMANCE Peak-to-Peak Noise en p-p.1 Hz to 1 Hz 77 1 nv p-p Voltage Noise Density en f = 1 khz 2.8 3.8 nv/ Hz Current Noise Density in f = 1 khz.3 pa/ Hz Channel Separation AD8672/AD8674 CS f = 1 khz 13 db f = 1 khz 15 db Rev. F Page 3 of 2

AD8671/AD8672/AD8674 Data Sheet ELECTRICAL CHARACTERISTICS, ±15 V VS = ±15 V, VCM = V, T A = 25 C, unless otherwise noted. Table 3. Parameter Symbol Conditions Min Typ Max Unit INPUT CHARACTERISTICS Offset Voltage VOS 2 75 µv 4 C < TA < +125 C 3 125 µv Offset Voltage Drift VOS/ T 4 C < TA < +125 C AD8671.3.5 µv/ C AD8672/AD8674.3.8 µv/ C Input Bias Current IB 12 +3 +12 na +25 C < TA < +125 C 2 +5 +2 na 4 C < TA < +125 C 4 +8 +4 na Input Offset Current IOS 12 +6 +12 na +25 C < TA < +125 C 2 +6 +2 na 4 C < TA < +125 C 4 +8 +4 na Input Voltage Range 12 +12 V Common-Mode Rejection Ratio CMRR VCM = 12 V to +12 V 1 12 db Large Signal Voltage Gain AVO RL = 2 kω, VO = 1 V to +1 V 1 6 V/mV Input Capacitance, Common Mode CINCM 6.25 pf Input Capacitance, Differential Mode CINDM 7.5 pf Input Resistance, Common Mode RIN 3.5 GΩ Input Resistance, Differential Mode RINDM 15 MΩ OUTPUT CHARACTERISTICS Output Voltage High VOH RL = 2 kω, 4 C to +125 C +13.2 +13.8 V Output Voltage Low VOL RL = 2 kω, 4 C to +125 C 13.8 13.2 V Output Voltage High VOH RL = 6 Ω +11 +12.3 V Output Voltage Low VOL RL = 6 Ω 12.4 11 V Output Current IOUT ±2 ma Short Circuit Current ISC ±3 ma POWER SUPPLY Power Supply Rejection Ratio PSRR VS = ±4 V to ±18 V AD8671/AD8672 11 13 db AD8674 16 115 db Supply Current/Amplifier ISY VO = V 3 3.5 ma 4 C <TA < +125 C 4.2 ma DYNAMIC PERFORMANCE Slew Rate SR RL = 2 kω 4 V/µs Settling Time ts To.1% (1 V step, G = 1) 2.2 µs To.1% (1 V step, G = 1) 6.3 µs Gain Bandwidth Product GBP 1 MHz NOISE PERFORMANCE Peak-to-Peak Noise en p-p.1 Hz to 1 Hz 77 1 nv p-p Voltage Noise Density en f = 1 khz 2.8 3.8 nv/ Hz Current Noise Density in f = 1 khz.3 pa/ Hz Channel Separation AD8672/AD8674 CS f = 1 khz 13 db f = 1 khz 15 db Rev. F Page 4 of 2

Data Sheet ABSOLUTE MAXIMUM RATINGS Table 4. 1 Parameter Rating Supply Voltage 36 V Input Voltage VS to VS+ Differential Input Voltage ±.7 V Output Short-Circuit Duration Indefinite Storage Temperature Range All Packages 65 C to +15 C Operating Temperature Range 8-Lead Packages 4 C to +125 C 14-Lead Packages 4 C to +85 C Junction Temperature Range All Packages 65 C to +15 C Lead Temperature Range (Soldering, 6 sec) 3 C 1 Absolute maximum ratings apply at 25 C, unless otherwise noted. AD8671/AD8672/AD8674 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 θja 1 θjc Unit 8-Lead MSOP (RM) 142 44 C/W 8-Lead SOIC_N (R) 12 43 C/W 14-Lead SOIC_N (R) 9 36 C/W 14-Lead TSSOP (RU) 112 35 C/W 1 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 4 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 2

AD8671/AD8672/AD8674 Data Sheet TYPICAL PERFORMANCE CHARACTERISTICS VOLTAGE NOISE DENSITY (nv/ Hz) 32 28 24 2 16 12 8 4 CURRENT NOISE DENSITY (pa/ Hz) 1 1 1 2 3 4 5 6 7 8 9 1 FREQUENCY (Hz) 3718-B-7.1 1 1 1 1k 1k FREQUENCY (Hz) 3718-112 Figure 4. Voltage Noise Density vs. Frequency Figure 7. Current Noise Density VS = ±15 V VOLTAGE NOISE DENSITY (nv/ Hz) 31.5 27. 22.5 18. 13.5 9. 4.5 NUMBER OF AMPLIFIERS 45 4 35 3 25 2 15 1 5 V S = ±5V T A = 25 C.1.2.3.4.5.6.7.8.9 1. FREQUENCY (khz) 3718-B-8 35 3 25 2 15 1 5 5 1 15 2 25 3 35 4 45 V OS (µv) 3718-B-1 Figure 5. Voltage Noise Density vs. Frequency Figure 8. Input Offset Voltage Distribution VOLTAGE NOISE DENSITY (nv/ Hz) 17.5 15. 12.5 1. 7.5 5. 2.5 NUMBER OF AMPLIFIERS 35 3 25 2 15 1 5 T A = 25 C 1 2 3 4 5 6 7 8 9 1 FREQUENCY (khz) 3718-B-9 35 3 25 2 15 1 5 5 1 15 2 25 3 35 4 45 5 V OS (µv) 3718-B-11 Figure 6. Voltage Noise Density vs. Frequency Figure 9. Input Offset Voltage Distribution Rev. F Page 6 of 2

Data Sheet AD8671/AD8672/AD8674 16 4. 15 3.8 14 13 3.6 V OS (µv) 12 11 I SY (ma) 3.4 3.2 1 V S = ±5V 9 8 7 6 4 25 85 125 TEMPERATURE ( C) 3718-B-12 3. 2.8 2.6 V S = ±5V 2.4 4 25 85 125 TEMPERATURE ( C) 3718-B-15 Figure 1. Input Offset Voltage vs. Temperature Figure 13. Supply Current vs. Temperature I B (na) 5. 4.5 4. 3.5 3. 2.5 2. 1.5 I B +I B V S = ±5V OUTPUT VOLTAGE (V) 14.5 14. 13.5 13. 12.5 12. 11.5 R L = 2kΩ R L = 6Ω 1. 11..5 1.5 4 25 85 125 TEMPERATURE ( C) 3718-B-13 1. 4 25 85 125 TEMPERATURE ( C) 3718-B-16 Figure 11. Input Bias Current vs. Temperature Figure 14. Output Voltage High vs. Temperature 2.5 2. 11. 11.5 I B (na) 1.5 1..5 +I B I B OUTPUT VOLTAGE (V) 12. 12.5 13. 13.5 R L = 2kΩ R L = 6Ω.5 14. 1. 4 25 85 125 TEMPERATURE ( C) Figure 12. Input Bias Current vs. Temperature 3718-B-14 14.5 4 25 85 125 TEMPERATURE ( C) Figure 15. Output Voltage Low vs. Temperature 3718-B-17 Rev. F Page 7 of 2

AD8671/AD8672/AD8674 Data Sheet 6 27 5 V SY = ±15V R L = 1kΩ 225 4 GAIN C L = 2pF F M = 59 18 1 9 8 OPEN-LOOP GAIN (db) 3 2 1 1 PHASE 135 9 45 45 OPEN-LOOP PHASE (db) IMPEDANCE (Ω) 7 6 5 4 3 A VO = 1 2 3 9 135 2 1 A VO = 1 A VO = 1 4 1k 1M FREQUENCY (Hz) 1M 18 3718-B-18 1 1k 1k 1k 1M FREQUENCY (Hz) 1M 1M 3718-B-21 Figure 16. Open-Loop Gain and Phase Shift vs. Frequency Figure 19. Output Impedance vs. Frequency 3 25 ±5V V SY = ±15V V IN = 4V R L = 2kΩ A VO (V/mV) 2 15 1 ±15V VOLTAGE (1V/DIV) 5 4 25 85 125 TEMPERATURE ( C) 3718-B-19 TIME (1µs/DIV) 3718-B-22 Figure 17. Open-Loop Gain vs. Temperature Figure 2. Large Signal Transient Response CLOSED-LOOP GAIN (db) 5 4 3 2 1 1 2 3 A V = 1 A V = 1 A V = 1 V SY = ±15V V IN = 1mV R L = C L = 2pF VOLTAGE (5mV/DIV) V SY = ±15V V IN = 2mV p-p R L = 2kΩ 4 5 1k 1k 1k 1M FREQUENCY (Hz) 1M 1M 3718-B-2 TIME (1ms/DIV) 3718-B-23 Figure 18. Closed-Loop Gain vs. Frequency Figure 21. Small Signal Transient Response Rev. F Page 8 of 2

Data Sheet AD8671/AD8672/AD8674 SMALL SIGNAL OVERSHOOT (%) 6 5 4 3 2 1 +OS OS V S =±15 CMRR (db) 16 14 12 1 8 6 4 2 2 V SY = ±15V 1 1k 1k CAPACITANCE (pf) 3718-B-24 4 1 1 1k 1k 1k FREQUENCY (Hz) 1M 1M 1M 3718-B-27 Figure 22. Small Signal Overshoot vs. Load Capacitance Figure 25. CMRR vs. Frequency VOLTAGE (2mV/DIV) V IN = 2mV p-p A V = 1 R L = 1k V OUT V IN V PSRR (db) 16 14 12 1 8 6 4 2 V SY = ±15V PSRR +PSRR V 2 TIME (4 s/div) 3718-B-25 4 1 1 1k 1k 1k FREQUENCY (Hz) 1M 1M 3718-B-28 Figure 23. Positive Overdrive Recovery Figure 26. PSRR vs. Frequency V IN V SY = ±15V V IN = 2mV p-p A V = 1 R L = 1k 135 134 133 V S = ±2.5V TO ±18V VOLTAGE (2mV/DIV) V OUT V V PSRR (db) 132 131 13 129 128 TIME (4 s/div) 3718-B-26 127 4 25 85 125 TEMPERATURE ( C) 3718-B-29 Figure 24. Negative Overdrive Recovery Figure 27. PSRR vs. Temperature Rev. F Page 9 of 2

AD8671/AD8672/AD8674 Data Sheet 2, ±5V VOLTAGE NOISE (5nV/DIV) CHANNEL SEPARATION (db) 4 6 8 1 12 TIME (1µs/DIV) 3718-B-3 14 1 1k 1k 1k 1M FREQUENCY (Hz) 1M 1M 3718-B-31 Figure 29. Channel Separation Figure 28..1 Hz to 1 Hz Input Voltage Noise Rev. F Page 1 of 2

Data Sheet APPLICATIONS POWER DISSIPATION CALCULATIONS To achieve low voltage noise in a bipolar op amp, the current must be increased. The emitter-base theoretical voltage noise is approximately e = n 2 qi 1 9 kt C nv/ Hz 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 6 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. 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 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 3 C and the supply voltages are ±12 V, the power dissipation is 24 V 3.5 ma = 84 mw AD8671/AD8672/AD8674 Therefore, the rise above ambient temperature is 54 mw 112 C/W = 56 C With an ambient temperature of 5 C, the junction temperature is 16 C. This is less than the specified absolute maximum junction temperature, but for systems with long product lifetimes (years), this should be considered carefully. 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 ADA491-4, OP4177, ADA44-4, OP497, or AD74 can be considered. UNITY-GAIN FOLLOWER APPLICATIONS When large transient pulses (>1 V) are applied at the positive terminal of amplifiers (such as the OP27, LT17, 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 5 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 3 shows the uncompensated output response with a 1 kω resistor in the feedback and the compensated response with CF = 15 pf. Therefore, the rise above ambient temperature is 84 mw 142 C/W = 12 C If the ambient temperature is 3 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. VOLTAGE (1V/DIV) OUTPUT UNCOMPENSATED OUTPUT COMPENSATED REF1 +OVER 23.23% CH2 +OVER 7.885% 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 5 C and the supply voltages are ±15 V, the power dissipation is 3 V 4.2 ma four op amps = 54 mw TIME (1ns/DIV) Figure 3. Transient Output Response 3718-B-32 Rev. F Page 11 of 2

AD8671/AD8672/AD8674 OUTPUT PHASE REVERSAL 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. VOLTAGE (1V/DIV) V IN V OUT V SY = ±15V Data Sheet TOTAL NOISE VS. SOURCE RESISTANCE 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. Figure 32 shows the voltage noise, current noise, thermal noise, and total rms noise of the AD8671 as a function of the source resistance. 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. 1 TIME (1 s/div) Figure 31. Output Phase Reversal 3718-B-33 TOTAL NOISE (nv/ Hz) 1 1 C i n e n_t A (4kR S T) 1/2 B e n 1 1 1 1k 1k SOURCE RESISTANCE ( ) 1k 1M 3718-B-34 Figure 32. Noise vs. Source Resistance Rev. F Page 12 of 2

Data Sheet AD8671/AD8672/AD8674 TOTAL HARMONIC DISTORTION (THD) AND NOISE 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.6% of THD + N in a positive unity gain, the worst-case configuration for distortion. PERCENTAGE.1.5.2.1.5.2.1.5.2 LT17 V S = ±5V V IN = 2.5V R L = 6Ω AD8671 VOLTAGE (5mV/DIV) R G 5Ω TIME (1ms/DIV) V SY = ±15V R L = 2kΩ C L = 1nF V IN = 1mV A V = +1 Figure 34. AD8671 Capacitive Load Drive C F 22pF R F 5Ω V CC R S CH2 +OVER 39.8% CH2 OVER 39.8% 3718-B-36.1 2 5 1 2 5 1k 2k 5k 1k Hz Figure 33. Total Harmonic Distortion and Noise 2k 3718-B-35 V IN VEE 1Ω C L 1nF R L 2kΩ 3718-B-37 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. 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. The output response of the circuit is shown in Figure 36. VOLTAGE (1mV/DIV) Figure 35. Recommended Capacitive Load Circuit TIME (1ms/DIV) V SY = ±15V R L = 2kΩ C L = 1nF C F = 22pF V IN = 1mV A V = +2 Figure 36. Compensated Load Drive CH2 +OVER 5.51% CH2 OVER 6.61% 3718-B-38 Rev. F Page 13 of 2

AD8671/AD8672/AD8674 Data Sheet BAND-PASS FILTER LOW NOISE OP AMP MIXER DEMODULATOR LOW-PASS FILTER VGA ADC AD8671 AD8671 AD831 AD63 AD861 AD8369 AD12 CODE GENERATOR 3718-B-39 Figure 37. Simplified Block Diagram of a GPS Receiver GPS RECEIVER 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. Figure 37 shows a simplified block diagram of a GPS receiver. The next section details the design equations. BAND-PASS FILTER 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. V IN R1 2.25kΩ C2 1nF C2 1nF 2.25kΩ R2 R3 2.25kΩ V CC V EE Figure 38. Band-Pass KRC Filter R B R A 18kΩ 1kΩ The equal component topology yields a center frequency where: 2 fo = 2 πrc 2 and Q = 4 K 3718-B-4 The band-pass response is shown in Figure 39. 2µV/DIV 1 1k 1k 1k 1M Hz Figure 39. Band-Pass Response 1M PLL SYNTHESIZERS AND LOOP FILTERS Phase-lock loop filters are used in AM/FM modulation. 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 4. PHASE DETECTOR CHARGE PUMP R1 1kΩ V CC C1 1nF VCO 3718-B-41 K = 1 + R R B A IN D V EE 3718-B-42 Figure 4. PLL Filter Simplified Block Diagram Rev. F Page 14 of 2

Data Sheet AD8671/AD8672/AD8674 OUTLINE DIMENSIONS 5. (.1968) 4.8 (.189) 4. (.1574) 3.8 (.1497) 8 5 1 4 6.2 (.2441) 5.8 (.2284).25 (.98).1 (.4) COPLANARITY.1 SEATING PLANE 1.27 (.5) BSC 1.75 (.688) 1.35 (.532).51 (.21).31 (.122) 8.25 (.98).17 (.67).5 (.196).25 (.99) 1.27 (.5).4 (.157) 45 COMPLIANT TO JEDEC STANDARDS MS-12-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. 1247-A Figure 41. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) Dimensions shown in millimeters and (inches) 3.2 3. 2.8 3.2 3. 2.8 8 1 5 4 5.15 4.9 4.65 PIN 1 IDENTIFIER.95.85.75.15.5 COPLANARITY.1.65 BSC.4.25 1.1 MAX 6 15 MAX.23.9 COMPLIANT TO JEDEC STANDARDS MO-187-AA Figure 42. 8-Lead Mini Small Outline Package [MSOP] (RM-8) Dimensions shown in millimeters.8.55.4 1-7-29-B Rev. F Page 15 of 2

AD8671/AD8672/AD8674 Data Sheet 8.75 (.3445) 8.55 (.3366) 4. (.1575) 3.8 (.1496) 14 8 1 7 6.2 (.2441) 5.8 (.2283).25 (.98).1 (.39) COPLANARITY.1 1.27 (.5) BSC.51 (.21).31 (.122) 1.75 (.689) 1.35 (.531) SEATING PLANE 8.25 (.98).17 (.67).5 (.197).25 (.98) 1.27 (.5).4 (.157) 45 COMPLIANT TO JEDEC STANDARDS MS-12-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. 666-A Figure 43. 14-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-14) Dimensions shown in millimeters and (inches) 5.1 5. 4.9 14 8 4.5 4.4 4.3 6.4 BSC 1 7 PIN 1 1.5 1..8.65 BSC.15.5.3 COPLANARITY.19.1 1.2 MAX SEATING PLANE.2.9 8 COMPLIANT TO JEDEC STANDARDS MO-153-AB-1 Figure 44. 14-Lead Thin Shrink Small Outline Package [TSSOP] (RU-14) Dimensions shown in millimeters.75.6.45 6198-A Rev. F Page 16 of 2

Data Sheet AD8671/AD8672/AD8674 ORDERING GUIDE Model 1 Temperature Range Package Description Package Option Branding AD8671ARZ 4 C to +125 C 8-Lead SOIC_N R-8 AD8671ARZ-REEL 4 C to +125 C 8-Lead SOIC_N R-8 AD8671ARZ-REEL7 4 C to +125 C 8-Lead SOIC_N R-8 AD8671ARMZ 4 C to +125 C 8-Lead MSOP RM-8 AV AD8671ARMZ-REEL 4 C to +125 C 8-Lead MSOP RM-8 AV AD8672AR 4 C to +125 C 8-Lead SOIC_N R-8 AD8672AR-REEL 4 C to +125 C 8-Lead SOIC_N R-8 AD8672AR-REEL7 4 C to +125 C 8-Lead SOIC_N R-8 AD8672ARZ 4 C to +125 C 8-Lead SOIC_N R-8 AD8672ARZ-REEL 4 C to +125 C 8-Lead SOIC_N R-8 AD8672ARZ-REEL7 4 C to +125 C 8-Lead SOIC_N R-8 AD8672ARMZ 4 C to +125 C 8-Lead MSOP RM-8 AW AD8672ARMZ-REEL 4 C to +125 C 8-Lead MSOP RM-8 AW AD8674ARZ 4 C to +85 C 14-Lead SOIC_N R-14 AD8674ARZ-REEL 4 C to +85 C 14-Lead SOIC_N R-14 AD8674ARZ-REEL7 4 C to +85 C 14-Lead SOIC_N R-14 AD8674ARU 4 C to +85 C 14-Lead TSSOP RU-14 AD8674ARUZ 4 C to +85 C 14-Lead TSSOP RU-14 AD8674ARUZ-REEL 4 C to +85 C 14-Lead TSSOP RU-14 1 Z = RoHS Compliant Part. Rev. F Page 17 of 2

AD8671/AD8672/AD8674 Data Sheet NOTES Rev. F Page 18 of 2

Data Sheet AD8671/AD8672/AD8674 NOTES Rev. F Page 19 of 2

AD8671/AD8672/AD8674 Data Sheet NOTES 24 213 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D3718 3/13(F) Rev. F Page 2 of 2