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rev. c a ad8610/AD8620 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. no license is granted by implication or otherwise under any patent or patent rights of analog devices. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781/329-4700 www.analog.com fax: 781/326-8703 ? analog devices, inc., 2002 precision, very low noise, low input bias current, wide bandwidth jfet operational amplifier functional block diagrams 8-lead msop and soic (rm-8 and r-8 suffixes) in in v v out null nc 1 45 8 ad8610 null nc = no connect 8-lead soic (r-8 suffix) ina ina v outb inb inb v 1 45 8 AD8620 outa features low noise 6 nv/ hz low offset voltage: 100 v max low input bias current 10 pa max fast settling: 600 ns to 0.01% low distortion unity gain stable no phase reversal dual-supply operation: 5 v to 13 v applications photodiode amplifier ate instrumentation sensors and controls high-performance filters fast precision integrators high-performance audio general description the ad8610/AD8620 is a very high precision jfet input amplifier featuring ultralow offset voltage and drift, very low input voltage and current noise, very low input bias current, and wide bandwidth. unlike many jfet amplifiers, the ad8610/AD8620 input bias current is low over the entire operating temperature range. the ad8610/AD8620 is stable with capacitive loads of over 1000 pf in noninverting unity gain; much larger capacitive loads can be driven easily at higher noise gains. the ad8610/AD8620 swings to within 1.2 v of the supplies even with a 1 k w load, maximizing dynamic range even with limited supply voltages. outputs slew at 50 v/ m s in either inverting or noninverting gain configurations, and settle to 0.01% accuracy in less than 600 ns. combined with the high input impedance, great precision, and very high output drive, the ad8610/AD8620 is an ideal amplifier for driving high performance a/d inputs and buffering d/a converter outputs. applications for the ad8610/AD8620 include electronic instru- ments; ate amplification, buffering, and integrator circuits; cat/m ri/ultrasound medical instrumentation; instrumentation quality photodiode amplification; fast precision filters (including pll filters); and high quality audio. the ad8610/AD8620 is fully specified over the extended industrial (?0 c to +125 c) temperature range. the ad8610 is available in the narrow 8-lead soic and the tiny msop8 surface-mount packages. the AD8620 is available in the narrow 8-lead soic package. msop8 packaged devices are available only in tape and reel.
rev. c ? ad8610/AD8620?pecifications parameter symbol conditions min typ max unit input characteristics offset voltage (ad8610b) v os 45 100 m v C 40 c < t a < +125 c80 200 m v offset voltage (AD8620b) v os 45 150 m v C 40 c < t a < +125 c80 300 m v offset voltage (ad8610a/AD8620a) v os 85 250 m v +25 c < t a < 125 c90 350 m v C 40 c < t a < +125 c 150 850 m v input bias current i b C 10 +2 +10 pa C 40 c < t a < +85 c C 250 +130 +250 pa C 40 c < t a < +125 c C 2.5 +1.5 +2.5 na input offset current i os C 10 +1 +10 pa C 40 c < t a < +85 c C 75 +20 +75 pa C 40 c < t a < +125 c C 150 +40 +150 pa input voltage range C 2+3v common-mode rejection ratio cmrr v cm = C 2.5 v to +1.5 v 90 95 db large signal voltage gain a vo r l = 1 k w , v o = C 3 v to +3 v 100 180 v/mv offset voltage drift (ad8610b) d v os / d t C 40 c < t a < +125 c 0.5 1 m v/ c offset voltage drift (AD8620b) d v os / d t C 40 c < t a < +125 c 0.5 1.5 m v/ c offset voltage drift (ad8610a/AD8620a) d v os / d t C 40 c < t a < +125 c 0.8 3.5 m v/ c output characteristics output voltage high v oh r l = 1 k w , C 40 c < t a < +125 c 3.8 4 v output voltage low v ol r l = 1 k w , C 40 c < t a < +125 c C 4 C 3.8 v output current i out v out > 2 v 30 ma power supply power supply rejection ratio psrr v s = 5 v to 13 v 100 110 db supply current/amplifier i sy v o = 0 v 2,500 3,000 m a C 40 c < t a < +125 c 3,000 3,500 m a dynamic performance slew rate sr r l = 2 k w 40 50 v/ m s gain bandwidth product gbp 25 mhz settling time t s a v = +1, 4 v step, to 0.01% 350 ns noise performance voltage noise e n p-p 0.1 hz to 10 hz 1.8 m v p-p voltage noise density e n f = 1 khz 6 nv/ hz current noise density i n f = 1 khz 5 fa/ hz input capacitance c in differential 8pf common-mode 15 pf channel separation c s f = 10 khz 137 db f = 300 khz 120 db specifications subject to change without notice. (@ v s = 5.0 v, v cm = 0 v, t a = 25 c, unless otherwise noted.)
rev. c ? ad8610/AD8620 electrical specifications (@ v s = 13 v, v cm = 0 v, t a = 25 c, unless otherwise noted.) parameter symbol conditions min typ max unit input characteristics offset voltage (ad8610b) v os 45 100 m v C 40 c < t a < +125 c80 200 m v offset voltage (AD8620b) v os 45 150 m v C 40 c < t a < +125 c80 300 m v offset voltage (ad8610a /AD8620a) v os 85 250 m v +25 c < t a < 125 c90 350 m v C 40 c < t a < +125 c 150 850 m v input bias current i b C 10 +3 +10 pa C 40 c < t a < +85 c C 250 +130 +250 pa C 40 c < t a < +125 c C 3.5 +3.5 na input offset current i os C 10 +1.5 +10 pa C 40 c < t a < +85 c C 75 +20 +75 pa C 40 c < t a < +125 c C 150 +40 +150 pa input voltage range C 10.5 +10.5 v common-mode rejection ratio cmrr v cm = C 10 v to +10 v 90 110 db large signal voltage gain a vo r l = 1 k w , v o = C 10 v to +10 v 100 200 v/mv offset voltage drift (ad8610b) d v os / d t C 40 c < t a < +125 c 0.5 1 m v/ c offset voltage drift (AD8620b) d v os / d t C 40 c < t a < +125 c 0.5 1.5 m v/ c offset voltage drift (ad8610a/AD8620a) d v os / d t C 40 c < t a < +125 c 0.8 3.5 m v/ c output characteristics output voltage high v oh r l = 1 k w , C 40 c < t a < +125 c +11.75 +11.84 v output voltage low v ol r l = 1 k w , C 40 c < t a < +125 c C 11.84 C 11.75 v output current i out v out > 10 v 45 ma short circuit current i sc 65 ma power supply power supply rejection ratio psrr v s = 5 v to 13 v 100 110 db supply current/amplifier i sy v o = 0 v 3,000 3,500 m a C 40 c < t a < +125 c 3,500 4,000 m a dynamic performance slew rate sr r l = 2 k w 40 60 v/ m s gain bandwidth product gbp 25 mhz settling time t s a v = 1, 10 v step, to 0.01% 600 ns noise performance voltage noise e n p-p 0.1 hz to 10 hz 1.8 m v p-p voltage noise density e n f = 1 khz 6 nv/ hz current noise density i n f = 1 khz 5 fa/ hz input capacitance c in differential 8pf common-mode 15 pf channel separation c s f = 10 khz 137 db f = 300 khz 120 db specifications subject to change without notice.
rev. c ad8610/AD8620 ? ordering guide temperature package package branding model range description option information ad8610arm C 40 c to +125 c 8-lead msop rm-8 b0a ad8610ar C 40 c to +125 c 8-lead soic rn-8 ad8610br C 40 c to +125 c 8-lead soic rn-8 AD8620ar C 40 c to +125 c 8-lead soic rn-8 AD8620br C 40 c to +125 c 8-lead soic rn-8 absolute maximum ratings * supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.3 v input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v s C C to v s+ differential input voltage . . . . . . . . . . . . . . supply voltage output short-circuit duration to gnd . . . . . . . . . indefinite storage temperature range r, rm packages . . . . . . . . . . . . . . . . . . . . C 65 c to +150 c operating temperature range ad8610/AD8620 . . . . . . . . . . . . . . . . . . . C 40 c to +125 c junction temperature range r, rm packages . . . . . . . . . . . . . . . . . . . . C 65 c to +150 c lead temperature range (soldering, 10 sec) . . . . . . . 300 c * 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 listed in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. package type ja * jc unit 8-lead msop (rm) 190 44 c/w 8-lead soic (rn) 158 43 c/w * q ja is specified for worst-case conditions; i.e., q ja is specified for a device soldered in circuit board for surface-mount packages. 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 the ad8610/AD8620 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. warning! esd sensitive device
rev. c ? ad8610/AD8620 input offset voltage ? v 14 8 6 4 2 10 12 0 250 250 150 50 150 50 number of amplifiers v s = 13v tpc 1. input offset voltage at 13 v input offset voltage ? v 600 400 600 200 0 200 400 temperature ? c 40 25 85 125 v s = 5v tpc 4. input offset voltage vs. temperature at 5 v (300 amplifiers) supply voltage ? v 3.0 1.5 0 2.5 1.0 0.5 2.0 013 12 3 456789101112 supply current ? ma tpc 7. supply current vs. supply voltage input offset voltage ? v 600 400 600 200 0 200 400 v s = 13v temperature ? c 40 25 85 125 tpc 2. input offset voltage vs. temperature at 13 v (300 amplifiers) t c v os ? v/ c 14 0 12 10 8 6 4 2 00.2 0.6 1 .0 1.4 1.8 2.2 2.6 number of amplifiers v s = 5v or 13v tpc 5. input offset voltage drift v s = 13v temperature ? c 2.55 3.05 2.85 2.65 2.95 2.75 supply current ? ma 40 25 85 125 tpc 8. supply current vs. temperature at 13 v v s = 5v input offset voltage ? v 14 8 6 4 2 10 12 0 16 18 250 250 150 50 150 50 number of amplifiers tpc 3. input offset voltage at 5 v common-mode voltage ? v 3.6 3.4 2.0 2.8 2.6 2.4 2.2 3.2 3.0 10 5 0510 input bias current ? pa v s = 13v tpc 6. input bias current vs. common- mode voltage temperature ? c 2.30 2.65 2.60 2.40 2.50 2.55 2.45 2.35 supply current ? ma v s = 5v 40 25 85 125 tpc 9. supply current vs. temperature at 5 v t ypical performance characteristics
rev. c ad8610/AD8620 ? output voltage to supply rail? v resistance load ? 100m 10m 1m 100k 10k 1k 100 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 v s = 13v tpc 10. output voltage to supply rail vs. load 12.05 11.80 12.00 11.95 11.90 11.85 output voltage high ? v v s = 13v r l = 1k temperature ? c 40 25 85 125 tpc 13. output voltage high vs. temperature at 13 v frequency ? hz 10k 100k 1m 1k 10m 100m closed-loop gain ? db 40 20 0 20 60 40 g = 100 g = 10 g = 1 v s = 13v r l = 2k c l = 20pf tpc 16. closed-loop gain vs. frequency temperature ? c 4.25 4.20 3.95 4.15 4.10 4.05 4.00 40 25 85 125 output voltage high ? v v s = 5v r l = 1k tpc 11. output voltage high vs. temperature at 5 v temperature ? c 11.80 12.05 11.85 11.90 11.95 12.00 40 25 85 125 output voltage low ? v v s = 13v r l = 1k tpc 14. output voltage low vs. temperature at 13 v temperature ? c 260 100 40 25 85 125 a vo ? v/mv 220 180 140 v s = 13v v o = 10v r l = 1k 240 200 160 120 tpc 17. a vo vs. temperature at 13 v temperature ? c 3.95 4.05 4.30 4.10 4.15 4.20 4.25 4.00 output voltage low ? v v s = 5v r l = 1k 40 25 85 125 tpc 12. output voltage low vs. temperature at 5 v gain ? db 40 20 0 60 80 100 120 20 40 60 80 frequency ? mhz 200 100 10 1 phase ? degrees v s = 13v r l = 1k marker at 27mhz m = 69.5 c l = 20pf 90 45 0 135 180 225 270 45 90 135 180 tpc 15. open-loop gain and phase vs. frequency temperature ? c 190 100 180 160 140 120 170 150 130 110 40 25 85 125 a vo ? v/mv v s = 5v v o = 3v r l = 1k tpc 18. a vo vs. temperature at 5 v
rev. c ? ad8610/AD8620 psrr ? db ?40 100 80 60 40 0 120 ?20 20 160 140 frequency ? hz 60m 10k 100k 1m 10m 100 1k v s = 13v + psrr ?psrr tpc 19. psrr vs. frequency at 13 v cmrr ? db frequency ? hz 10 60m 10k 100k 1m 10m 100 1k v s = 13v 140 0 100 80 60 40 20 120 tpc 22. cmrr vs. frequency time ? 1s/div p-p voltage noise ? 1 v/div v s = 13v v in p-p = 1.8 v tpc 25. 0.1 hz to 10 hz input voltage noise psrr ? db 122 121 116 120 119 118 117 temperature ? c 40 25 85 125 tpc 21. psrr vs. temperature v s = 13v v in = 300mv p-p a v = 100 r l = 10k c l = 0pf time ? 4 s/div vo lta ge ? 300mv/div v in 0v 0v v out ch 2 = 5v/div tpc 24. negative overvoltage recovery gain = 10 v s = 13v frequency ? hz 1k 100m 10k 100k 1m 10m z out ? 100 90 0 80 70 60 50 40 30 20 10 gain = 100 gain = 1 tpc 27. z out vs. frequency tpc 20. psrr vs. frequency at 5 v v s = 13v v in = 300mv p-p a v = 100 r l = 10k time ? 4 s/div vo ltag e ? 300mv/div v in 0v 0v v out ch 2 = 5v/div tpc 23. positive overvoltage recovery frequency ? hz 1,000 100 1 10 11m 100 10k 10 1k 100k vo lta ge noise density ? nv/ hz v sy = 13v tpc 26. input voltage noise vs. frequency
rev. c ad8610/AD8620 ? gain = 100 gain = 1 v s = 5v frequency ? hz 1k 100m 10k 100k 1m 10m z out ? 100 90 0 80 70 60 50 40 30 20 10 gain = 10 tpc 28. z out vs. frequency capacitance ? pf 40 35 0 30 25 5 20 15 10 110k 10 100 1k small signal overshoot ? % v s = 5v r l = 2k v in = 100mv +os os tpc 31. small signal overshoot vs. load capacitance time ? 400ns/div vo lta ge ? 5v/div v s = 13v v in p-p = 20v a v = +1 r l = 2k c l = 20pf tpc 34. +sr at g = +1 temperature ? c i b ? pa 3000 2500 0 025 85 125 2000 1500 1000 500 tpc 29. input bias current vs. temperature time ? 400 s/div vo lta ge ? 5v/div v s = 13v v in = 14v a v = +1 freq = 0.5khz v in v out tpc 32. no phase reversal time ? 400ns/div vo lta ge ? 5v/div v s = 13v v in p-p = 20v a v = +1 r l = 2k c l = 20pf tpc 35. ?r at g = +1 capacitance ? p f 40 35 0 30 25 5 20 15 10 110k 10 100 1k small signal overshoot ? % v s = 13v r l = 2k v in = 100mv p-p +os os tpc 30. small signal overshoot vs. load capacitance time ? 1 s/div vo lta ge ? 5v/div v s = 13v v in p-p = 20v a v = +1 r l = 2k c l = 20pf tpc 33. large signal response at g = +1 time ? 1 s/div vo lta ge ? 5v/div v s = 13v v in p-p = 20v a v = 1 r l = 2k c l = 20pf tpc 36. large signal response at g = ?
rev. c ad8610/AD8620 ? time ? 400ns/div vo ltag e ? 5v/div v s = 13v v in p-p = 20v a v = 1 r l = 2k sr = 55v/ s c l = 20pf tpc 37. +sr at g = ? time ? 400ns/div vo ltag e ? 5v/div v s = 13v v in p-p = 20v a v = 1 r l = 2k sr = 50v/ s c l = 20pf tpc 38. ?r at g = ? + ? v in 20v p-p 0 3 2 u1 +13v ?13v 2k r4 2k 0 0 2k r1 20k r2 0 0 u2 5 6 7 v+ v? v? v+ cs(db) = 20 log (v out / 10 v in ) figure 1. channel separation test circuit functional description the ad8610/AD8620 is manufactured on analog devices propri- etary xfcb (extra fast complementary bipolar) process. xfcb is fully dielectrically isolated (di), and used in conjunction with n-channel jfet technology and trimmable thin-film resistors to create the world s most precise jfet input amplifier. dielectrically isolated npn and pnp transistors fabricated on xfcb have f t greater than 3 ghz. low t c thin film resistors enable very accurate offset voltage and offset voltage tempco trimming. these process breakthroughs allowed analog devices world class ic designers to create an amplifier with faster slew rate and more than 50% higher bandwidth at half of the current consumed by its closest competition. the ad8610 is unconditionally stable in all gains, even with capacitive loads well in excess of 1 nf. the ad8610b achieves less than 100 m v of offset and 1 m v/ c of offset drift, numbers usually associated with very high precision bipolar input amplifiers. the ad8610 is offered in the tiny 8-lead msop as well as narrow 8-lead soic surface-mount packages and is fully specified with supply voltages from 5 v to 13 v. the very wide specified temperature range, up to 125 c, guarantees superior operation in systems with little or no active cooling. the unique input architecture of the ad8610 features extremely low input bias currents and very low input offset voltage. low power consumption minimizes the die temperature and maintains the very low input bias current. unlike many competitive jfet amplifiers, the ad8610/AD8620 input bias currents are low even at elevated temperatures. typical bias currents are less than 200 pa at 85 c. the gate current of a jfet doubles every 10 c resulting in a similar increase in input bias current over temperature. special care should be given to the pc board layout to minimize leakage currents between pcb traces. improper layout and board handling generates leakage current that exceeds the bias current of the ad8610/AD8620. frequency ? khz 0350 50 100 150 200 250 300 138 136 120 128 126 124 122 132 130 134 cs ? db figure 2. AD8620 channel separation graph power consumption a major advantage of the ad8610/AD8620 in new designs is the saving of power. lower power consumption of the ad8610 makes it much more attractive for portable instrumentation and for high-density systems, simplifying thermal management, and reducing power supply performance requirements. com pare the power c onsumption of the ad8610/AD8620 versus the opa627 in figure 3. temperature ? c 8 7 6 5 4 3 2 ?75 125 ?50 supply current ? ma ?25 0 25 50 75 100 opa627 ad8610 figure 3. supply current vs. temperature
rev. c ad8610/AD8620 ?0 driving large capacitive loads the ad8610 has excellent capacitive load driving capability and can safely drive up to 10 nf when operating with 5 v supply. figures 4 and 5 compare the ad8610/AD8620 against the opa627 in the noninverting gain configuration driving a 10 k w resistor and 10,000 pf capacitor placed in parallel on its output, with a square wave input set to a frequency of 200 khz. the ad8610 has much less ringing than the opa627 with heavy capacitive loads. time ? 2 s/div vo ltag e ? 20mv/div v s = 5v c l = 10,000pf r l = 10k figure 4. opa627 driving c l = 10,000pf time ? 2 s/div vo ltag e ? 20mv/div v s = 5v c l = 10,000pf r l = 10k figure 5. ad8610/AD8620 driving c l = 10,000pf the ad8610/AD8620 can drive much larger capacitances without an y external compensation. although the ad8610/AD8620 is stable with very large capacitive loads, remember that this capacitive loading will limit the bandwidth of the amplifier. heavy capacitive loads will also increase the amount of overshoot and ringing at the output. figures 7 and 8 show the ad8610/AD8620 and the opa627 in a noninverting gain of 2 driving 2 m f of capacitance load. the ringing on the opa627 is much larger in magnitude and continues more than 10 times longer than the ad8610. v in = 50mv 2k 2k ?5v +5v 2 f 3 2 7 4 figure 6. capacitive load drive test circuit time ? 20 s/div vo ltag e ? 50mv/div v s = 5v r l = 10k c l = 2 f figure 7. opa627 capacitive load drive, a v = +2 time ? 20 s/div vo ltag e ? 50mv/div v s = 5v r l = 10k c l = 2 f figure 8. ad8610/AD8620 capacitive load drive, a v = +2 slew rate (unity gain inverting vs. noninverting) amplifiers generally have a faster slew rate in an inverting unity gain configuration due to the absence of the differential input capacitance. f igures 9 through 12 show the performance of the ad8610 configured in a gain of C 1 compared to the opa627. the ad8610 slew rate is more symmetrical, and both the positive and negative transitions are much cleaner than in the opa627.
rev. c ad8610/AD8620 ?1 time ? 400ns/div vo ltag e ? 5v/div v s = 13v r l = 2k g = ?1 sr = 54v/ s figure 9. (+sr) of ad8610/AD8620 in unity gain of ? time ? 400ns/div vo ltag e ? 5v/div v s = 13v r l = 2k g = ?1 sr = 42.1v/ s figure 10. (+sr) of opa627 in unity gain of ? time ? 400ns/div vo ltag e ? 5v/div v s = 13v r l = 2k g = ?1 sr = 54v/ s figure 11. (?r) of ad8610/AD8620 in unity gain of ? time ? 400ns/div vo ltag e ? 5v/div v s = 13v r l = 2k g = ?1 sr = 56v/ s figure 12. (?r) of opa627 in unity gain of ? the ad8610 has a very fast slew rate of 60 v/ m s even when config- ured in a noninverting gain of +1. this is the toughest condition to impose on any amplifier since the input common-mode capacitance of the amplifier generally makes its sr appear worse. the slew rate of an amplifier varies according to the voltage difference between its two inputs. to observe the maximum sr as specified in the ad8610 data sheet, a difference voltage of about 2 v between the inputs must be ensured. this will be required for virtually any jfet op amp so that one side of the op amp input circuit is com- pletely off, maximizing the current available to charge and discharge the internal compensation capacitance. lower differential drive voltages will produce lower slew rate readings. a jfet- input op amp with a slew rate of 60 v/ m s at unity gain with v in = 10 v might slew at 20 v/ m s if it is operated at a gain of +100 with v in = 100 mv. the slew rate of the ad8610/AD8620 is double that of the opa627 when configured in a unity gain of +1 (see figures 13 and 14). time ? 400ns/div vo lta ge ? 5v/div v s = 13v r l = 2k g = +1 sr = 85v/ s figure 13. (+sr) of ad8610/AD8620 in unity gain of +1
rev. c ad8610/AD8620 ?2 diodes greatly interfere with many application circuits such as precision rectifiers and comparators. the ad8610 is free from these limitations. v1 ?13v 3 2 7 4 +13v 14v 0 6 ad8610 figure 16. unity gain follower no phase reversal many amplifiers misbehave when one or both of the inputs are forced beyond the input common-mode voltage range. phase reversal is typified by the transfer function of the amplifier, effectively reversing its transfer polarity. in some cases, this can cause lockup and even equipment damage in servo systems, and may cause permanent damage or nonrecoverable parameter shifts to the amplifier itself. many amplifiers feature compensation circuitry to combat these effects, but some are only effective for the inverting input. the ad8610/AD8620 is designed to prevent phase reversal when one or both inputs are forced beyond their input common-mode voltage range. time ? 400 s/div 0 vo lta ge ? 5v/div v in v out figure 17. no phase reversal thd readings vs. common-mode voltage total harmonic distortion of the ad8610/AD8620 is well below 0.0006% with any load down to 600 w . the ad8610/AD8620 outperforms the opa627 for distortion, especially at frequen- cies above 20 khz. frequency ? hz 0.01 0.0001 10 80k thd+n ? % 0.001 0.1 100 1k 10k opa627 ad8610 v sy = 13v v in = 5v rms bw = 80khz figure 18. ad8610 vs. opa627 thd + noise @ v cm = 0 v time ? 400ns/div vo lta ge ? 5v/div v s = 13v r l = 2k g = +1 sr = 23v/ s figure 14. (+sr) of opa627 in unity gain of +1 the slew rate of an amplifier determines the maximum frequency at which it can respond to a large signal input. this frequency (known as full power b andwidth, or fpbw) can be calculated from the equation: fpbw sr v peak = () 2 p for a given distortion (e.g., 1%). vo lta ge ? 10v/div 0v ch 2 = 19.4v p-p 0v ch 1 = 20.8v p-p time ? 400ns/div figure 15. ad8610 fpbw input overvoltage protection when the input of an amplifier is driven below v ee or above v cc by more than one v be , large currents will flow from the substrate through the negative supply (v C ) or the positive supply (v+), respectively, to the input pins, which can destroy the device. if the input source can deliver larger currents than the maximum forward current of the diode (>5 ma), a series resistor can be added to protect the inputs. with its very low input bias and offset current, a large series resistor can be placed in front of the ad8610 inputs to limit current to below damaging levels. s eries resistance of 10 k w will generate less than 25 m v of offset. this 10 k w will allow input voltages more than 5 v beyond either power supply. thermal noise generated by the resistor will add 7.5 nv/ hz to the noise of the ad8610. for the ad8610/AD8620, differential voltages e qual to the supply voltage will not cause any problem (see f igure 15). in this context, it should also be noted that the high breakdown voltage of the input fets eliminates the need to include clamp diodes between the inputs of the amplifier, a practice that is mandatory on many precision op amps. unfortunately, clamp
rev. c ad8610/AD8620 ?3 4v rms 6v rms 2v rms v sy = 13v r l = 600 frequency ? hz 0.01 0.001 10 20k thd + n ? % 0.1 100 1k 10k figure 19. thd + n oise vs. frequency noise vs. common-mode voltage ad8610 noise density varies only 10% over the input range as shown in table i. table i. noise vs. common-mode voltage v cm at f = 1 khz (v) noise reading (nv/ hz ) C 10 7.21 C 56.89 06.73 +5 6.41 +10 7.21 settling time the ad8610 has a very fast settling time, even to a very tight error band, as can be seen from figure 20. the ad8610 is configured in an inverting gain of +1 with 2 k w input and feedback resistors. the output is monitored with a 10 , 10 m, 11.2 pf scope probe. error band ? % 1.2k 0 0.001 10 0.01 settling time ? ns 0.1 1 800 400 1.0k 600 200 figure 20. ad8610 settling time vs. error band error band ? % 1.2k 1.0k 0 0.001 10 0.01 settling time ? ns 0.1 1 800 600 200 400 opa627 figure 21. opa627 settling time vs. error band the ad8610/AD8620 maintains this fast settling when loaded with large capacitive loads as shown in figure 22. c l ? pf 0 2000 500 settling time ? s 1000 1500 error band 0.01% 3.0 2.0 0.0 1.0 2.5 1.5 0.5 figure 22. ad8610 settling time vs. load capacitance c l ? pf 3.0 2.0 0.0 1.0 2.5 1.5 0.5 02 000 500 settling time ? s 1000 1500 error band 0.01% figure 23. opa627 settling time vs. load capacitance output current capability t he ad8610 can drive very heavy loads due to its high output current. it is capable of sourcing or sinking 45 ma at 10 v output. the short circuit current is quite high and the part is capable of sinking about 95 ma and sourcing over 60 ma while operating with
rev. c ad8610/AD8620 ?4 supplies of 5 v. figures 24 and 25 compare the l oad current v ersus o utput voltage of ad8610/AD8620 and opa627. load current ? a 10 0.1 0.00001 1 delta from respective rail ? v 1 0.0001 0.001 0.01 0.1 v ee v cc figure 24. ad8610 dropout from 13 v vs. load current load current ? a 10 0.1 0.00001 1 delta from respective rail ? v 1 0.0001 0.001 0.01 0.1 v ee v cc figure 25. opa627 dropout from 15 v vs. load current although operating conditions imposed on the ad8610 ( 13 v) are less favorable than the opa627 ( 15 v), it can be seen that the ad8610 has much better drive capability (lower headroom to the supply) for a given load current. operating with supplies greater than 13 v the ad8610 maximum operating voltage is specified at 13 v. when 13 v is not readily available, an inexpensive ldo can provide 12 v from a nominal 15 v supply. input offset voltage adjustment o ffset of ad8610 is very small and normally does not require additional offset adjustment. however, t he offset adjust pins can be used as shown in figure 26 to further reduce the dc offset. by using resistors in the range of 50 k w , offset trim range is 3.3 mv. r1 2 3 7 5 +v s v out 4 6 ?v s 1 ad8610 figure 26. offset voltage nulling circuit programmable gain amplifier (pga) the combination of low noise, low input bias current, low input offset voltage, and low temperature drift make the ad8610 a perfect solution for programmable gain amplifiers. pgas are often used immediately after sensors to increase the dynamic range of the measurement circuit. historically, the large on resistance of switches, combined with the large i b c urrents of amplifiers, created a large dc offset in pgas. recent and improved monolithic switches and amplifiers completely remove these problems. a pga discrete circuit is shown in figure 27. in figure 27, when the 10 pa bias current of the ad8610 is dropped across the (<5 w ) r on of the switch, it results in a negligible offset error. when high precision resistors are used, as in the circuit of figure 27, the error introduced by the pga is within the 1/2 lsb requirement for a 16-bit system. y0 y1 y2 y3 g a b 5 in1 s1 d1 10k 10k 1k ?5v +5v in2 s2 d2 in3 s3 d3 in4 s4 d4 adg452 3 2 14 15 11 10 6 7 v l v dd 13 12 1 16 9 8 74hc139 v ss 4 gnd 5 v out 1k 100 11 5pf 100 v in g = 1 g = 10 g = 100 g = 1000 +5v +5v ad8610 u10 a0 a1 ?5v figure 27. high precision pga 1. room temperature error calculation due to r on and i b : dw d d vir pa pv total offset offset v total offset offset trimmed v total offset v pv v os b on os os = = = =+ =+ =+ @ 2510 8610 8610 5105 () (_ ) ad ad mm 2. full temperature error calculation due to r on and i b : d w vcicr c pa nv os b on ()()() . @@ @ 85 85 85 250 15 3 75 = = = 3. temperature coefficient of switch and ad8610/AD8620 combined is essentially the same as the t c v os of the ad8610: dd dd dd dd vt total v t v t i r vt total v c nv c v c os os os b on os /( ) /( ) /( ) /( ) . / . / . / =+ = + @ ad8610 05 006 05 mm
rev. c ad8610/AD8620 ?5 high-speed instrumentation amplifier (in amp) the three op amp instrumentation amplifiers shown in figure 28 can provide a range of gains from unity up to 1,000 or higher. the instrumentation amplifier configuration features high common- mode rejection, balanced differential inputs, and stable, accurately defined gain. low input bias currents and fast settling are achieved with the jfet input ad8610/AD8620. most instrumentation amplifiers cannot match the high-frequency performance of this circuit. the circuit bandwidth is 25 mhz at a gain of 1, and close to 5 mhz at a gain of 10. settling time for the entire circuit is 550 ns to 0.01% for a 10 v step (gain = 10). note that the resistors around the input pins need to be small enough in value so that the rc time constant they form in combination with stray circuit capacitance does not reduce circuit bandwidth. 1/2 AD8620 u 1 v in2 c2 10pf r2 1k r4 2k r7 2k c4 15pf v out r6 2k r8 2k v? v+ ad8610 u2 c3 15pf r5 2k v in1 v? v+ 1/2 AD8620 u1 c5 10pf r1 1k rg figure 28. high-speed instrumentation amplifier high-speed filters 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 ii. in active filter applications using operational amplifiers, the dc accuracy of the amplifier is critical to optimal filter performance. the amplifier s offset voltage and bias current contribute to output error. input offset voltage is passed by the filter, and may be amplified to produce excessive output offset. for low-frequency applications requiring large value input resistors, bias and offset currents flowing through these resistors will also generate an offset voltage. at higher frequencies, an amplifier s dynamic response must be carefully considered. in this case, slew rate, bandwidth, and open- loop gain play a major role in amplifier selection. the slew rate must be both fast and symmetrical to minimize distortion. the amplifier s bandwidth, in conjunction with the filter s gain , will dictate the frequency resp onse of the filter. the use of a high perfor- mance amplifier such as the ad8610/AD8620 will minimize both dc and ac errors in all active filter applications. second order low-pass filter figure 29 shows the ad8610 configured as a second order butterworth low-pass filter. with the values as shown, the corner frequency of the filter will be 1 mhz. the wide bandwidth of the ad8610/AD8620 allows a corner frequency up to tens of m egahertz. the following equations can be used for component selection: rr user selected typical values k k c fr c fr cutoff cutoff 12 10 100 1 1 414 21 2 0 707 21 == - () = ()( )() = ()( )() : . . ww p p where c 1 and c 2 are in farads. ?13v +13v 5 c2 11pf v in ad8610 u1 v out r2 10k r1 10k c1 22pf figure 29. second order low-pass filter table ii. filter types type sensitivity overshoot phase amplitude (pass band) butterworth moderate good max flat chebyshev good moderate nonlinear equal ripple elliptical best poor equal ripple bessel (thompson) poor best linear
rev. c ?6 c02730??0/02(c) printed in u.s.a. ad8610/AD8620 outline dimensions revision history location page 10/02 data sheet changed from rev. b to rev. c. updated ordering guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 edits to figure 15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 updated outline dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5/02 data sheet changed from rev. a to rev. b. addition of part number AD8620 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . universal addition of 8-lead soic (r-8 suffix) drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 changes to general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 additions to specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 change to electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 additions to ordering guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 replace tpc 29 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 add channel separation test circuit figure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 add channel separation graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 changes to figure 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 addition of high-speed, low noise differential driver section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 addition of figure 30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 high-speed, low noise differential driver the AD8620 is a perfect candidate as a low noise differential d river for many popular adcs. there are also other applications, such as balanced lines, that require differential drivers. the circuit of figure 30 is a unique line driver widely used in industrial applica- tions. with 13 v supplies, the line driver can deliver a differential signal of 23 v p-p into a 1 k w load. the high slew rate and wide bandwidth of the AD8620 combine to yield a full power bandwidth of 145 khz while the low noise front end produces a referred-to- input noise voltage spectral density of 6 nv/ hz . the design is a transformerless, balanced transmission system where output common-mode rejection of noise is of paramount importance. like the transformer-based design, either output can be shorted to ground for unbalanced line driver applications without changing the circuit gain of 1. this allows the design to be easily set to noninverting, inverting, or differential operation. 3 2 v? 3 2 v? v+ 5 6 1k r8 v+ r10 50 1/2 of AD8620 r1 1k 1k r9 1k r4 1k r3 ad8610 1/2 of AD8620 6 r2 1k 7 u3 u2 r13 1k r5 1k r6 10k r7 1k r12 1k r11 50 v o 2 v o 1 v? v+ 0 1 v o 2 ? v o 1 = v in 0 figure 30. differential driver 8-lead standard small outline package [soic] narrow body (rn-8) dimensions shown in millimeters and (inches) 0.25 (0.0098) 0.19 (0.0075) 1.27 (0.0500) 0.41 (0.0160) 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) 85 4 1 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) 0.33 (0.0130) coplanarity 0.10 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-012aa 8-lead msop package [msop] (rm-8) dimensions shown in millimeters 0.23 0.08 0.80 0.40 8 0 85 4 1 4.90 bsc pin 1 0.65 bsc 3.00 bsc seating plane 0.15 0.00 0.38 0.22 1.10 max 3.00 bsc compliant to jedec standards mo-187aa coplanarity 0.10

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