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dual/quad low power, high speed jfet operational amplifiers ad8682/ad8684 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 ?2006 analog devices, inc. all rights reserved. features low supply current: 250 a/amp maximum high slew rate: 9 v/s bandwidth: 3.5 mhz typical low offset voltage: 1 mv maximum @ 25c low input bias current: 20 pa maximum @ 25c cmrr: 90 db typical fast settling time unity gain stable applications portable telecommunication low power industrial and instrumentation loop filters active and precision filters integrators strain gauge amplifiers portable medical instrumentation supply current monitoring pin configurations out a 1 ?in a 2 +in a 3 v? 4 v+ 8 out b 7 ?in b 6 +in b 5 ad8682 top view (not to scale) 0 6278-001 figure 1. 8-lead soic_n and 8-lead msop out a 1 ?in a 2 +in a 3 v+ 4 out d 14 ?in d 13 +in d 12 v? 11 +in b 5 +in c 10 ?in b 6 ?in c 9 out b 7 out c 8 ad8684 top view (not to scale) 06278-002 figure 2. 14-lead soic_n and 14-lead tssop general description the ad8682 and ad8684 are dual and quad low power, precision (1 mv) jfet amplifiers featuring excellent speed at low supply currents. the slew rate is typically 9 v/s with a supply current under 250 a per amplifier. these unity-gain stable amplifiers have a typical gain bandwidth of 3.5 mhz. the jfet input stage ensures bias current is typically a few picoamps and below 125 pa maximum over the full temperature operating range. the devices are ideal for portable, low power applications, especially with high source impedance. the devices are unity gain stable and can drive higher capacity loads (g = 1, noninverting), as an example of their excellent dynamic response over a wide range of conditions, delivering dc precision performance at low quiescent currents.
ad8682/ad8684 rev. 0 | page 2 of 16 table of contents features .............................................................................................. 1 applications....................................................................................... 1 pin configurations ........................................................................... 1 general description ......................................................................... 1 revision history ............................................................................... 2 specifications..................................................................................... 3 electrical characteristics............................................................. 3 absolute maximum ratings............................................................ 4 thermal resistance ...................................................................... 4 esd caution...................................................................................4 typical performance characteristic................................................5 applications information .............................................................. 10 high-side signal conditioning ................................................ 10 phase inversion........................................................................... 10 active filters ............................................................................... 10 programmable state variable filter ......................................... 11 outline dimensions ....................................................................... 12 ordering guide .......................................................................... 13 revision history 10/06revision 0: initial version
ad8682/ad8684 rev. 0 | page 3 of 16 specifications electrical characteristics v s = 15.0 v, t a = 25c, v cm = 0 v, unless otherwise noted. table 1. parameter symbol conditions min typ max unit input characteristics offset voltage v os 0.35 1 mv ad8682: +25c t a +85c 2.5 mv ad8684: +25c t a +85c 3.5 mv ad8682: ?40c t a +25c 3 mv ad8684: ?40c t a +25c 4 mv input bias current i b 6 20 pa ?40c t a +85c 125 pa input offset current i os 20 pa ?40c t a +85c 100 pa input voltage range ?11 +15 v common-mode rejection ratio cmrr ?11 v v cm +15 v, ?40c t a +85c 70 90 db large signal voltage gain a vo r l = 10 k 20 v/mv r l = 10 k, ?40c t a +85c 15 v/mv offset voltage drift v os /t 10 v/c bias current drift i b /t 8 pa/c output characteristics output voltage high v oh r l = 10 k +13.5 +13.9 v output voltage low v ol r l = 10 k ?13.9 ?13.5 v short-circuit limit i sc source 3 10 ma sink ?12 ?8 ma open-loop output impedance z out f = 1 mhz 200 power supply power supply rejection ratio psrr v s = 4.5 v to 18 v, ?40c t a +85c 92 114 db supply current/amplifier i sy v o = 0 v, ?40c t a +85c 210 250 a supply voltage range v s 4.5 18 v dynamic performance slew rate sr r l = 10 k 7 9 v/s full-power bandwidth bw p 1% distortion 125 khz settling time t s to 0.01% 1.6 s gain bandwidth product gbp 3.5 mhz phase margin ? o 55 degrees noise performance voltage noise e n p-p 0.1 hz to 10 hz 1.3 v p-p voltage noise density e n f = 1 khz 36 nv/hz current noise density i n 0.01 pa/hz
ad8682/ad8684 rev. 0 | page 4 of 16 absolute maximum ratings table 2. parameter rating supply voltage 18 v input voltage 18 v differential input voltage 1 36 v output short-circuit duration indefinite storage temperature range ?65c to +150c operating temperature range ?40c to +85c junction temperature range ?65c to +150c lead temperature (soldering, 60 sec) 300c 1 for supply voltages less than 18 v, the absolute maximum input voltage is equal to the supply voltage. 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. thermal resistance table 3. package type ja jc unit 8-lead msop [rm-8] 210 45 c/w 8-lead soic_n [r-8] 158 43 c/w 14-lead tssop [ru-14] 180 35 c/w 14-lead soic [r-14] 120 36 c/w esd caution
ad8682/ad8684 rev. 0 | page 5 of 16 typical performance characteristic frequency (hz) open-loop gain (db) 1k ?40 ?20 60 80 10k 1m 10m 100k 20 40 0 v s = 15v t a = 25c phase (degree) ?45 135 45 90 0 ?90 180 06278-003 figure 3. ad8682 open-loop gain and phase vs. frequency temperature (c) open-loop gain (v/mv) ?75 0 5 35 45 ?25 100 125 25 15 25 10 20 30 40 75 50 0 ?50 v s = 15v r l = 10k ? 06278-004 figure 4. ad8682 open-loop gain vs. temperature load capacitance (pf) overshoot (%) 0 0 10 70 80 200 400 500 30 50 20 40 60 300 100 v s = 15v r l = 2k ? v in = 100mv p-p a vcl = 1 t a = 25c +os ?os 06278-005 figure 5. small signal overshoot vs. load capacitance frequency (hz) closed-loop gain (db) 1k ?30 ?20 60 70 10k 1m 10m 100k 20 40 0 v s = 15v t a = 25c ?10 50 10 30 a vcl = 100 a vcl = 10 a vcl = 1 06278-006 figure 6. ad8682 closed-loop gain vs. frequency temperature (c) slew r a te (v/s) ?75 0 5 30 ?25 100 125 25 15 25 10 v s = 15v r l = 10k ? c l = 50pf 20 7550 0 ?50 ?sr +sr 06278-007 figure 7. slew rate vs. temperature temperature (c) input bias current (pa) ?75 0.1 1000 ?25 100 125 25 1 100 10 7550 0 ?50 v s = 15v v cm = 0v 06278-008 figure 8. ad8682 input bias current vs. temperature
ad8682/ad8684 rev. 0 | page 6 of 16 frequency (hz) voltage noise density (nv/ hz) 10 1 1000 100 10k 1k 100 10 v s = 15v t a = 25c 06278-009 figure 9. voltage noise density vs. frequency common-mode voltage (v) input bias current (pa) ?15 0.1 1000 10 15 ?5 1 100 10 5 0 ?10 v s = 15v t a = 25c 06278-010 figure 10. input bias current vs. common-mode voltage supply voltage (v) supply current (a) 0 450 480 20 10 455 465 460 15 5 t a = 25c 470 475 06278-011 figure 11. ad8682 supply current vs. supply voltage supply voltage (v) output voltage swing (v) 0 ?20 20 20 10 ?15 ?5 ?10 15 5 t a = 25c r l = 10k ? 0 15 v oh v ol 5 10 06278-012 figure 12. output voltage swing vs. supply voltage frequency (hz) output impedance ( ? ) 1k 0.1 100 1000 10k 1m 100 100k 1 10 v s = 15v t a = 25c a vcl = 100 a vcl = 10 a vcl = 1 06278-013 figure 13. closed-loop output impedance vs. frequency temperature (c) supply current (a) ?50 450 480 125 25 455 75 0 460 475 465 470 ?25 50 100 06278-014 figure 14. ad8682 supply current vs. temperature
ad8682/ad8684 rev. 0 | page 7 of 16 load resistance ( ? ) absolute output voltage (v) 0 6 16 1k 10k 100 2 4 v s = 15v t a = 25c v ol v oh 12 8 10 14 06278-015 figure 15. absolute output voltage vs. load resistance frequency (hz) psrr (db) 1k ?60 40 140 10k 1m 100 100k 0 20 ?40 ?20 60 100 120 80 ?psrr +psrr v s = 15v t a = 25c 06278-016 figure 16. ad8682 psrr vs. frequency temperature (c) sho r t-circuit current (ma) ?50 0 14 125 25 4 75 0 6 12 8 10 ?25 50 100 2 sink source v s = 15v t a = 25c 06278-017 figure 17. ad8682 short-circuit current vs. temperature frequency (hz) maximum output swing (v p-p) 100 0 5 25 30 1k 100k 1m 10k 15 20 10 v s = 15v t a = 25c r l = 10k ? a vcl = 1 06278-018 figure 18. maximum output swing vs. frequency frequency (hz) cmrr (db) 1k ?60 40 140 10k 1m 100 100k 0 20 ?40 ?20 60 100 120 80 v s = 15v t a = 25c 06278-019 figure 19. ad8682 cmrr vs. frequency 20 18 16 14 12 10 8 6 4 2 0 units ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 v os (v) 06278-020 v s = 15v t a = 25c 100 ad8682 (200 op amps) figure 20. ad8682 v os distribution
ad8682/ad8684 rev. 0 | page 8 of 16 tcv os (v/c) units 0 0 400 20 80 16 120 160 40 28 32 36 24 200 280 320 360 240 41 2 8 v s = 15v 300 op282 (600 op amps) 06278-021 figure 21. ad8682 tcv os distribution soic_n package 50 45 40 35 30 25 20 15 10 5 0 open-loop gain (v/mv) ?50 ?25 0 25 50 75 100 125 temperature (c) 06278-022 figure 22. ad8684 open-loop gain vs. temperature frequency (hz) 1k 10k 100k 1m 100m 10m 60 closed-loop gain (db) 40 20 10 0 50 30 ?10 ?20 v s = 15v t a = 25c 06278-023 a vcl = 10 a vcl = 1 a vcl = 100 figure 23. ad8684 close d-loop gain vs. frequency 06278-024 1000 100 10 1 0.1 input bias current (pa) ?50 ?25 0 25 50 75 100 125 temperature (c) ?75 figure 24. ad8684 input bias current vs. temperature 06278-025 950 945 940 930 925 920 915 910 supply current (a) 01 02 03 0 supply voltage (v) 935 4 0 figure 25. ad8684 relative supply current vs. supply voltage 06278-026 950 945 940 935 930 925 920 915 910 ?50 ?25 0 25 50 75 100 125 supply current (a) temperature (c) figure 26. ad8684 supply current vs. temperature
ad8682/ad8684 rev. 0 | page 9 of 16 1k 10k 100k 1m 10m frequency (hz) psrr+ psrr? v s = 15v 140 120 100 80 60 40 20 0 psrr (db) 06278-027 figure 27. ad8684 psrr vs. frequency 14 12 10 8 6 4 2 0 short-circuit current (ma) ?50 ?25 0 25 50 75 100 temperature (c) 06278-028 125 sink source figure 28. ad8684 short-circuit current vs. temperature 1k 10k 100k 1m 10m frequency (hz) v s = 15v 140 120 100 80 60 40 20 0 cmrr (db) 06278-029 figure 29. ad8684 cmrr vs. frequency v s = 15v t a = 25c 100 ad8684 (400 op amps) 40 35 30 25 20 15 10 5 0 units ?1.0 ?0.8 ?0.6 1.0 v os (v) 06278-030 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 figure 30. ad8684 v os distribution package 06278-031 v s = 15v 300 op282 (1200 op amps) 800 700 600 500 400 300 200 100 0 units tcv os (v/c) 24 60 5652 48 4440 36 3228201612 840 figure 31. ad8684 tcv os distribution package
ad8682/ad8684 rev. 0 | page 10 of 16 applications information the ad8682 and ad8684 are dual and quad jfet op amps that are optimized for high speed at low power. this combination makes these amplifiers excellent choices for battery-powered or low power applications that require above average performance. applications benefiting from this performance combination include telecommunications, geophysical exploration, portable medical equipment, and navigational instrumentation. high-side signal conditioning there are many applications requiring the sensing of signals near the positive rail. the ad8682 and the ad8684 were tested and are guaranteed over a common-mode range (?11 v v cm +15 v) that includes the positive supply. the ad8682/ad8684 are commonly used in the sensing of power supply currents and in current sensing applications, such as the partial circuit shown in figure 32. in this circuit, the voltage drop across a low value resistor, such as the 0.1 shown here, is amplified and compared to 7.5 v. the output can then be used for current limiting. 1/2 ad8682 100k ? 500k ? 100k ? 500k ? 0.1 ? 15v r l 06278-042 figure 32. high-side signal conditioning phase inversion most jfet input amplifiers invert the phase of the input signal if either input exceeds the input common-mode range. for the ad8682/ad8684, negative signals in excess of approximately 14 v cause phase inversion. this is caused by saturation of the input stage leading to the forward-biasing of a drain-gate diode. a simple fix for this in noninverting applications is to place a resistor in series with the noninverting input. this limits the amount of current through the forward-biased diode and prevents shutting down of the output stage. for the ad8682/ad8684, a value of 200 k has been found to work; however, it adds a significant amount of noise. 15 10 5 0 ?5 ?10 ?15 v out 15 10 5 0 ?5 ?10 ?15 v in 06278-043 figure 33. ad8682 phase reversal active filters the wide bandwidth and high slew rates of the ad8682/ad8684 make either one an excellent choice for many filter applications. there are many active filter configurations, but the four most popular configurations are: butterworth, elliptical, bessel, and chebyshev. each type has a response that is optimized for a given characteristic, as shown in table 4. table 4. type selectivity overshoot phase amplitude (pass band) amplitude (stop band) butterworth moderate good maximum flat chebyshev good moderate nonlinear equal ripple elliptical best poor equal ripple equal ripple bessel (thompson) poor best linear
ad8682/ad8684 rev. 0 | page 11 of 16 programmable state variable filter the circuit shown in figure 34 can be used to accurately program the q; the cutoff frequency, f c ; and the gain of a 2-pole state variable filter. the ad8684 has been used in this design because of its high bandwidth, low power, and low noise. this circuit takes only three packages to build because of the quad configuration of the op amps and dacs. the dacs shown are used in voltage mode; therefore, many values are dependent on the accuracy of the dac only and not on the absolute values of the dac resistive ladders. as a result, this makes the circuit unusually accurate for a programmable filter. adjusting dac 1 changes the signal amplitude across r1; therefore, the dac attenuation r1 determines the amount of signal current that charges the integrating capacitor, c1. this cutoff frequency can be expressed as ? ? ? ? ? ? = 256 2 1 d1 r1c1 fc where d1 is the digital code for the dac. the gain of this circuit is set by adjusting d3. the gain equation is ? ? ? ? ? ? = 256 d3 r5 r4 gain dac 2 is used to set the q of the circuit. adjusting this dac controls the amount of feedback from the band-pass node to the input summing node. note that the digital value of the dac is in the numerator; therefore, zero code is not a valid operating point. ? ? ? ? ? ? = d2r3 r2 q 256 1/4 ad8684 1/4 dac8408 r5 2k? r4 2k? 1/4 ad8684 1/4 ad8684 1/4 dac8408 r1 2k? c1 1000pf 1/4 ad8684 1/4 ad8684 1/4 dac8408 r1 2k? c1 1000pf 1/4 ad8684 1/4 dac8408 r2 2k? r3 2k? 1/4 ad8684 1/4 ad8684 r6 2k? high pass band pass low pass v in r7 2k? 06278-044 figure 34. programmable state variable filter
ad8682/ad8684 rev. 0 | page 12 of 16 outline dimensions controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design. compliant to jedec standards ms-012-a a 060506-a 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 0.50 (0.0196) 0.25 (0.0099) 45 8 0 1.75 (0.0688) 1.35 (0.0532) seating plane 0.25 (0.0098) 0.10 (0.0040) 4 1 85 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 1.27 (0.0500) bsc 6.20 (0.2440) 5.80 (0.2284) 0.51 (0.0201) 0.31 (0.0122) coplanarity 0.10 figure 35. 8-lead standard small outline package [soic_n] narrow body (r-8) dimensions shown in millimeters and (inches) compliant to jedec standards mo-187-aa 0.80 0.60 0.40 8 0 4 8 1 5 pin 1 0.65 bsc seating plane 0.38 0.22 1.10 max 3.20 3.00 2.80 coplanarity 0.10 0.23 0.08 3.20 3.00 2.80 5.15 4.90 4.65 0.15 0.00 0.95 0.85 0.75 figure 36. 8-lead mini small outline package [msop] (rm-8) dimensions shown in millimeters
ad8682/ad8684 rev. 0 | page 13 of 16 controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design. compliant to jedec standards ms-012-ab 060606-a 14 8 7 1 6.20 (0.2441) 5.80 (0.2283) 4.00 (0.1575) 3.80 (0.1496) 8.75 (0.3445) 8.55 (0.3366) 1.27 (0.0500) bsc seating plane 0.25 (0.0098) 0.10 (0.0039) 0.51 (0.0201) 0.31 (0.0122) 1.75 (0.0689) 1.35 (0.0531) 0.50 (0.0197) 0.25 (0.0098) 1.27 (0.0500) 0.40 (0.0157) 0.25 (0.0098) 0.17 (0.0067) coplanarity 0.10 8 0 45 figure 37. 14-lead standard small outline package [soic_n] narrow body (r-14) dimensions shown in millimeters and (inches) 4.50 4.40 4.30 14 8 7 1 6.40 bsc pin 1 5.10 5.00 4.90 0.65 bsc seating plane 0.15 0.05 0.30 0.19 1.20 max 1.05 1.00 0.80 0.20 0.09 8 0 0.75 0.60 0.45 coplanarity 0.10 compliant to jedec standards mo-153-ab-1 figure 38. 14-lead thin shrink small outline package [tssop] (ru-14) dimensions shown in millimeters ordering guide model temperature range package description package option branding ad8682arz 1 ?40c to +85c 8-lead soic_n r-8 ad8682arz-reel 1 ?40c to +85c 8-lead soic_n r-8 ad8682arz-reel7 1 ?40c to +85c 8-lead soic_n r-8 ad8682armz-r2 1 ?40c to +85c 8-lead msop rm-8 a1k ad8682armz-reel 1 ?40c to +85c 8-lead msop rm-8 a1k ad8684arz 1 ?40c to +85c 14-lead soic_n r-14 ad8684arz-reel 1 ?40c to +85c 14-lead soic_n r-14 ad8684arz-reel7 1 ?40c to +85c 14-lead soic_n r-14 AD8684ARUZ 1 ?40c to +85c 14-lead tssop ru-14 AD8684ARUZ_reel 1 ?40c to +85c 14-lead tssop ru-14 1 z= pb-free part.
ad8682/ad8684 rev. 0 | page 14 of 16 notes
ad8682/ad8684 rev. 0 | page 15 of 16 notes
ad8682/ad8684 rev. 0 | page 16 of 16 notes ?2006 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d06278-0-10/06(0)

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