analog devices fax-on-demand hotline - page 2 ~ analog w devices i features . open-loop gain... . 10,ooo,ooov/v mln . low input offset voltage. .. . .. .. . .. . . .. . . .. 25pv max . low input bias current 5namax . excellent tcvos """"""""""'" o.3pv/oc max . high cmrr 126db min . h/ghpsrr """"""""""""""'" 126dbm/n . low noise , 5.5nvl'l/hz @f=10hz 4.5nv/j'hz@f=1khz . high output current """""""""""'" :t50ma . drives capacitive loads up to 10nf . on-board thermal shutdown circuit . available in die form pin connections 14-pin hermetic dip (v-suffix) note, no internal connection to pins 3. 4. ano i. simplified schematic high-output -current operational amplifier (~ > 51 op-50 ordering informationt t... = 2s.c vos max (in) 25 100 25 100 package ceroip 14-pin op-50ay' op-50by- OP-50EY op-50fy operating temperature range mil mil ind ind . fofdevices processetj in lotal compliance to mil-sto.b83. add/bb3 after part number. consult factory for 883 data smet. t burn.in is available on commercial and industriallemperature range parts in card!p. plastic dip, and to.can packages. general description the or-50 eliminates the need for an output buffer in appli- cations which require high load-driving capability coupled with premium amplifier performance. the output stage can drive :t50ma into son loads. in addition, the output is stable with capacitive loads of up to 10nf. this load driving ability makes the op-50 ideal for amplifying small signals for trans- mission through long cables. the amplifier features open- loop voltage gain of over 10 million with common-mode rejection and power supply rejection of greater than 126db (ale grades). m____- external compensation r'~-ih i i comp lcom! v. ohset ,.- null ~ "--~ --, i va null + 2sof! -in 250f! -in i i l__----------- v- manufactured under the following patents: 4.471.321 and 4.503.381. --- ---- ~- 'yo. l i i i i i i i i i output i i i i j i i i i i i ~-~ ~~ -vop' 'note separate supplies for output stage. -1- ~~ obsolete
rnrlog devices frx-on-denrnd hotline - page 3 op-50 the or-50 is stable for closed-loop gains above 50. and can be externally compensated for closed-loop gains in the range of 5 to 50. the amplifier is designed for use in high-gain and/or high-output-current applications. for example, an o~-o7 coupled with an output buffer can be replaced by a single or-50 amplifier. ion-implanted superbeta transistors, combined with a pat- ented input bias current cancellation circuit, provide an input bias current of only 5na and input offset current of 1 na. over the full military temperature range, input bias current and input offset current for an a-grade device does not exceed bna and 3na. respectively. input offset voltages are trimmed to a maximum of 2spv (ale grades) and 1o0llv (b/f grades) using pml's zener-zapping technique. this low offset elimi- nates the need for an offset trimpot in most applications. low voltage-noise, typically 4.snv i jhz at 1 khz, is achieved in the or-so with minimum sacrifice of input protection. overload protection is provided by input resistors of 2s0n and emitter-base diodes. the input resistors provide current limit protection against differential inputs of up to j:10v; and the diodes prevent avalanche breakdown which could degrade the 18. 'os' and matching of the input stage transis- tors. external resistors can be added to the input to guard against higher input voltages; however. the added resistors will degrade noise voltage performance. when minimum noise voltage is required, source resistance should be kept below a few hundred ohms. separate output-stage power supply pins are provided on the op-50 to allow control of device power dissipation and out- put voltage swing. the maximum voltage which may be applied across the power supply pins is j:18v. the guaran- teed specifications are based on operating both stages at j:1sv; however. there is minimal effect on dc performance when the main amplifier is operated at :t15v and the output stage is operated at a reduced voltage. when operating both the main amplifier and the output stage at the same voltages. the corresponding power supply pins may be tied together. decoupling capacitors are recommended between the power supply pins and analog ground. it is necessary to use decou- piing capacitors on each power supply pin when operating the output stage at supply voltages less than the amplifier supply voltage. do not operate the output-stage negative power supply pin at a more negative voltage than the nega- tive supply pin (v-). a thermally-symmetric die layout, which differs from other op amp designs by the positioning of more devices along the center line. provides the op-50 with a thermal drift of less than o.3ilv/oc. this layout feature is critical to the mainte- nance of high open-loop gain when driving large-current loads and dissipating hundreds of milliwatts in the device. the use of a heatsink is recommended to reduce internal temperature rise when operating at high output power levels. the use of standard dual-in-line package heatsinks will help to dissipate heat to the environment. other techniques. such as the use of external voltage-dropping resistors. allow heat to be dissipated outside of the package. see figure 5, "driving soh loads", in the applications section. a thermal-shutdown circliit protects the op-sofrom overdis- sipation. when the die temperature reaches approximately 165c. the output stage automatically shuts down. the amplifier input stage remains fully operational. thereby pro- tecting the signal source from any loading changes caused by a complete shutdown. compensation for gains between 5 and 50 the or-50 can be compensated for inverting gains between 5 and 50 using a series resistor and capacitor. these values can be adjusted to minimize overshoot for a given applica- tion. the recommended compensation is: gain range ac cc 56011 4.7nf ~3kn lnf no compensation required 5 ~ avcl :, 20 20 $ avcl$ 50 avcl ~ 50 compensation absolute maximum ratings (note 1) supply voltage (note 2) :1: 18v input voltage supply voltage differential input voltage (note 3) :t 1 ov differential input current (note 3) :t:20ma output short.circuit duration indefinite storage temperature range 6s.c to +1s0.c operating temperature range op-soa, b s5.c to +12s.c op-50e. f 2s.c to +8s.c lead temperature (soldering, 60 sec) 300.c junction temperature (tj) 6s.c to +150c package type a'a (note 4) a,c units 14.pin hennetic dip m 99 12 'c/w notes' 1. absolute rallngs apply to both dice and packaged parts. unless otherwise noted. 2. supply voltage rating applies to aupower supply pins. no device pins should be connectedtoa voltage more negative than the supply to v-. pin 5. 3. the op.so's inputs are protected by 2500 series resistors and protedlon diodes. if the differential input voltage exceeds s 1 ov, the input current must be limited to _2orna. 4. 81a is specirled for worst case mounting conditions. i.e.. ala is specified for device in sockot for cerdip packago. -2- --- obsolete
analog devices fax-on-demand hotline - p age ~ v" '"" - ,., .. ., op-50 electrical characteristics at vt = tvop = +15v. v- = -vop = -15v. ta = 25c. no compensation. unless otherwise noted. parameter input ollset voltage -- input bias current symbol vos ie conditions :t3.8 :':2.8 op-50b/f mth typ max units input offset current input voltage range output voltage swing -'-" los ivr va v oulput voltage swing slew rate -....-.. common-mode rejection ratio vo sr ...---.......---- cmrr psrr power supply rejection ratio large-signal voltage gain gain-bandwidth product cmrr 2 l00db ri ~ soon rl? 500 (note i) v+ = +vop = +5v. v- '" -yap = -5v rl = soon al = son rl;" 2kn rc = soon cc=4.7nf +3.5 12.5 "'-'-'--"""'-' ""-"""""---'" . .."'---'-""--,,-,,, m___' 2.5 3.0 vii's vcm = ;tiov 110 120 db '-"'-- enp.p en inp.p ayo gbw vs = :!:5v io:!:'isv 0.5 in iv vo=:!:10v.rl=lko 7.5 15 v/"v """"' """-""""""" '..-.- ayel -- 50 (nola 2) is 25 mhz offset voltage range adjust input noise voltage noise voltage density noise current """"'-"""""'--"""'-""'- rr= lookn :tl.0 :':2.5 mv ..-.-----.-- f=0.lhztol0hz 0.12 0.12 "vp..p f = 10hz (note 3) f = 1khz 5,5 45 8,5 6.0 5.5 4.5 8.5 6.0 nvi.,jtfz ,-.---...-.........-.-...................-.-....-...... in isv +isc isc rind r'ncia cl ts not!s: ,. guaranteed by current limit tests, 2. guaranteed by design, 3. sample tested, -- t =o.1hz to 10hz 2 pap.p ' '.."""'" """"""-"'-' """"""" noise current density , = 100hz i = 1khz 0.3 0.23 pa/y"hz quiescent supply current no load 3.3 2.6 3.3 ma ma positive current limit negative current limit ditferential-mode input resistance output shorted to ground oulput shorted to ground 120 60 95 120 ma ----_......-- 120 60 85 120 """"""""'-""'-' 2 mil common-mode input resislance capacitive load capabmty ,. settling-time 20 g{! --.............. ayel 2: 5 rc ~ 5600 (nole 2) cc - 4.7nf settling to 0.01%, vo ~ 20vp_p ayel = 500 aycl = 1000 10 10 nf 30 60 30 60 1'5 --- -.--- 50 100 "v .--"-- :!:1 !o10 na .. - .............- 0.1 3 na --_.- :!:12 - - v ;t13 :!:13.4 - v :t2.5 1:4.0 - "-"""'-- op-50a/e mih typ max 10 25 il is 0.1 - i12 - -- =13 i13.4 :t2.5 ::4.0 ,3_5 +3.8 i2.5 =2.8 2.5 3.0 126 140 .-.-- 0.1 0.5 10 20 is 25 -- il.o :t2.5 2 - 0.3 0.23 - 2.6 60 9s 60 85 - 2 - 20 obsolete
analog oevices fax-on-oemand hotline - page 5 ." ~- , . op-50 electrical characteristics at v+ -- +vop-- +15v. v- -- -vop---15v. -25c:s ta:5 +s5c. no compensation. unless otherwise noted. notes: ,. tcvos tested on e grade. guaranteed by design on f grade specification. 2. guaranteed by design. electrical characteristics at vi = ivop =115v. v = -vop = "'15v. -55c ~ ta~ +125c. no compensation. unless otherwise noted. parameter symbol conditions op-soa min typ max op-sob min typ max units "-"""' '-' """"""..- input offset voltage ... input offset voltage crift vos input bias current input offset current 50 200 i'v tcvos 0.3 jiovicc ie '05 :t2 :!:20 na 0.5 12 na 0'"""",, 0'-"'--""-""'--"" input offset current croft tclos 3 5 pa/cc input bias current drllt tcla 20 50 pa/cc ....---.... input vollage range output voltage swing iva cmrr ?. 100d6 :t1'.s :t1'.5 v vo at 0> soon :!12 :!.c13.2 :!.c12 !13.2 v ""--' "--'--"--'. common-mode aejec1ion ratio power supply rejection ratio cmaa vcm'" !10v 120 130 105 120 db "" mm-____---........--......- ""--""-'" 0.5 1.25 0.5 1.25 i'v/v ...-- quiescent supply current 2..8 4 2.8 4 ma .-.--...---.......-- open-loop gain 4 10 4 10 v/"v note, ,. tested at +125'c. guaranteed by design at -55.c. -- op.soe op-sof parametf.r symbol conditions min typ max min typ max units input offset voltage vas - 20 45 - 50 150 "v ." ..- input offset tcvos (note 1) - 0..15 0.3 - 0..3 1 "v/cc voltage drift ,....... ......,....................-.. ........-,--.....--..-..-.......................-.... ..... ......., input bias current 18 2 z7 2 25 na input offset current los - 0.2 2.5 - 0.2 20 na input offsat tclos - 3 - 5 pa/cc current drift - - -...........,.-- ._... ...-.- ..........,...- input bias tcio - 20 - 50 pa/.c current drift - - -_.-._--- input voltage aange ivr cmra:;: 100da .il'.s - - :t1'.s - v -.-................,.--.. '----' .,-.... output voltage swing vo ai. ? soon 12 13.4 - 1:12 :!:13.4 --.. v .-...........-..- -_. -.....""""""'-"- common-mode cmrr vci.! = 1:10v 120 130 105 reiection ratio - 120 - db power supply psrr vs - .."!:5v to :!:15v - 0.5 1.25 - 0.5 1.25 "v/y rejection ratio ._- '...........-.... ....-............- ...--- quiescent supply isy no load - 2.8 4 - 2.8 4 ma current - --. open-loop gain ayo your = :t10y. (note 2) 4 15 -. 4 15 - v/"v rl = 1kl! 20 55 0.15 0.3 :t2 :t8 0.5 3 psrr vs = :tsv to :t15v isy no load .- ayo vo =:t10v. (note 1) at. -1kh obsolete
analog devices fax-on-demand hotline - page 6 op-50 dice characteristics die size 0.149 x 0.111 inch, 16,539 sq. mils (3.78 x 2.82 mm, 10.66 sq. mm) 1. noninverting input 2. inverting input 5. v'- 6. output 7. "vop 9. v+ 10. +vop 11. compensation 12. compensation 13. null 14. null 15. v- (optional bonding pad)" wafer test limits at v+ '" +vop = +15v, v- = -vop = -15v. ta = 25c. no compensation, unless otherwise noted. ..--.-.-..-. parameter conditions symbol input offset voltage input bias curren! vas 18 ...---...---............. .......--..---- input offset current output voltage swing 105 vo .._----------.- output voltage swing vo rl ~ soon v.. = +vop'" +sv. v-", -vop" ..sv rl = soon rl = sou _._--- common-mode rejection ratio _.- power supply rejection ratio cmrr vcm = i10v ""---"'--"'-'- psra vs = !5v 10 ::15v """",--,,"'-"""""'-""'---- large-signal voltage gain avo v()=!10v.r,"i~n ----- positive 5:~rrent limit ~ ?~itpljr shorted _t::,._glound negative currenl limit output shorled to gruund -isc- ---..---. -..-----...--- quiescent supply current i&v no load "--"""'---- op-sog limit units 100 pv max .. ' '-- . ..' ' '-- :t10 na max " 3 oa max :':13 v min :13.5 j:2.5 vmin 110 db min ~viv max 7.5 vlpv min ...---. ....-........................-..............- ., "",,""'........- 60 60 mamin mamin ------------...---.. .........----.............--. 3.3 ma max --.-.----- note: electrical tesls arc performed at wafer probe to the limits shown. due to lianations in assembly methods and normal yield loss. yield after packaging is nor guaranteed lor standard product dice. consult factory to negotiate specifications based on dice lot qualification through sample lot assembly and testing. -5- -- obsolete
analog devices fax-on-demand hotline . page 7 op-50 typical electrical characteristics at v+ = +vop= +15v, v- = vop=15v, t a == 25c. no compensation, unless otherwise noted. parameter symbol conditions -.--........--.- rl" 2kn ac ~ 56011 cc " ~'.~- op-sog typical units ---,,"""-',,""""-"""-',"""',,'..-----. slew rate sa 3 vii's "..~~ ,,'--"'-"" ...--.--..--..--......--....-- "--"'-"" "-""""--" noise voltage density en f -,,10hz 1= 1khz 5.5 4.5 nvi ,,!"hz ..n n n nn nn--n "" n n__---___- input noise voltage 9np.p r~o.1hzto10hz ,.- 10hz 1..- tkhz ........--......----.-- 0,12 0.2 0.15 -,-,,-_.,,_..,,~':.:~- -"' "'_n"n."-"""""'---'"",,, , noise current density in pa/\ihz " , ,....-- c1ipacitive load capability cl avcl ~ 5 rc ~ 560n cc" 4.7nf 10 nf ,..'..",- m ,.............. noise test circuit (0.1 to 10hz) 0_1.' , i- look!'! l00kf!. -15v 2kll 4.3k!j to hp 3582 spectrum anal yzer 12.35"f -lsv ion i"~ -15v ":' -15v burn.in circuit offset nulling circuit ,18v v. 101<" 10kl1 ou1pu1 j -18v rp 100 vb alt hf analog devices fam-on-denand hotline - page b 01'."50.7 . op-50 typical performance characteristics input offset voltage vi temperature 40 30 ~ 20 0 ~ 10 ... 0 ~ 0 :'i: ::: -10 0 .... ~ -20 ! -30 - ~ - - n ~ ~ n ~ ~ temperature i'ci input offset current vi temperature 0.6 0.5 ~ -= z 0,' .. a: a: :> :: 0:1 =: ::: 0 0,2 ~ .. ~ 0,1 0 -15 -so -25 0 25 so 76 100 ," temperature i'ci slew rate vi capacitive load ~ 2.0 ~ ~ " 1.5 :< ~ :: .. 1.0 0.5 i 10 100 caracitive load (nfi 1000 input bias current vi supply voltage 3.0 " 1a -;/!j'c i " . - 20 z ... ir ir a 1.5 ,. '" .. ;; 1.0 i ! i i ---t-- i i ; 0.5 0.5 "0 "5 120 suppl v vol 1 age {vol 1s1 slew rate vi temperature 5.0 h a~cl - 20 vs. t15v ac . 3.3kh i cc. tnf i . rl - ikn . ,'" cl" 100000f , i ! ! 4.0 ~ ~ 3.5 0; 1: ... 0: 3d 'sa _~r i 2.6 2,0 -15 -so -25 50 25 75 100 125 rempera1ure '"ct cmrr vi frequency ~ 130 z 2'20 ti ~ 110 0; g 100 a z !io i ! 80 u iii! !ii! 70 60 i 100 'k frequencv ihd iok 10 note; tl1e symbol ::tvs is used 10 indicate ihe supply voltages when the main amplifier and the output stage are being operated at the same voltages. --- input bias current vi common-mode voltage 3.0 vs' '15v 2.5 1 z 2,0 ... '" '" a 1,5 :'l ;; i 1.0 ! 0.' .\25 0 -10 10 -5 common-mooe voltage 'vol tst slew rate vs temperature 5-0 4.5 4.0 3.5 t i 3.0 a . id iit--r--+--i is t ~~:~~~, i! t'---r-t"'l 1.0 ~ : ~:t;f i '--r"--r"-'r . ""'-t . ---1 o.sl +-,,1,.1 cl" 1000pf i i . ! i 0 -15 -50 -25 0 2. 50 ,. 100 125 temperature "ci psrr vs frequency z 0 120 ;: ~ 110 ~ 100~- ~ ~ 90 '" '" 80 ~ 10 iincompfnsatfo ta'25'c vs' "&v avcl' 1000 -psrr 60 "'srr look so i 1m 100 ik tok frequency (hz) 10 100ii ----- vs" ,isv ...... "' ....... """" ....... "" " obsolete
analog devices fax-on-demand hotline - page 3 . op-50 typical performance characteristics short-circuit current ys temperature 160 140 i 120 2 ;: 100 '" " v ... 80 a '" if 60 :;: ~ 00 20 0 -7~ -50 -15 0 75 50 15 7fmperature i'ci 100 125 total harmonic distortion vs frequency 0,06 vs8t15v - rl = soon !! a.db ~ vo" love-e ~ ~ 0.04 1 i !ii i q i ~ 0.03 t- z ! ~ i '" ~ 0.02 ;i g 0,01 0 100 .. freouency 11101 --- supply current vs temperature 4.0 j.s - 30 " -~ ,.. 7.5 z .. 0: ~ 2.0 '"' >- ~ 1.5 ~ .. 1.0 0,5 0 -75 -so -25 0 25 50 75 100 125 temperature loci current noise density vi frequency 7.0 ~"ii i i i i ! ; i,s i ta' 25:~,' - vs""sv i 1.6 . -.i: " ;; 1,4 >- ... ;;; 1.2 ~ ~ 0 1.0 i o.s .,... .... ~ 06 8 0,0 v 0.2 ii! ~. ii . " i ! i i ! iplli i t--'.. *- ~ i , i i' , 1 ' i ' , , , i ol-j i b ii ! ., i 100 " 10 freouency ihzl total harmonic distortion vs load resistance 0.01 ~ ~ :< ~ 0 v 0.005 z i '" " :: -' " 0 ... lok 0 100 ik loao resistance (1)1 -- 101< 10k supply current vi supply voltage t a . 25"c i 5 f ; ;r ! 4 2 ~ ~ j u >- ~ 2 a ! l......--.- i ,5 !to ,15 ,20 suppl v voltage (vol ts, '25 voltage noise density vs frequency '4 ti 12 > ~ 10 >- '= ~ 9 ~ ~ 6 2; z \5 4 ~ ~ 2 nil ii l.. ' ill 0 i , 10 100 " frequency 1hz! 10' 0 to 1hz noise voltage density ohz 1hz 8o.0~v full scale io.o~vidiv vertical avcl " 10.000 -- psrr vi frequency 150 140 ;; !! '30 120 t- ::: 110 '" >- -, 100'" ! '" so 10 60 i 10 100 " 101< 1001< 1m frequency 1"0' vs' ,,'v " "' " ! """ ...... ""'- ! ....... , , i --r"""',- vs' :15v i i i ! i i i i ta=25'[ 1--- ..... ... . """""\ vs' '15v ! avcl' 100 .. ' f. ikh. i, vo' tp' .1 ......... ii \ ii 11 \ ii i i! 'i , 1 t ii i! i' , i i"-o-..i " ;' ' .. i' ii i i obsolete
analog devices fax-on-demand hotline - page 10 op-50 typical performance characteristics gain, phase shift vi frequency closed-loop gain vs frequency ik frequency 1",1 10k look frequency i"" 1m 10 output voltage swing vi load resistance 50 small-signal overshoot vi capacitive load - 9 " ~ ~- ~ el-, " z ~ 7 ~ ... 6 oj 0 > ... 5 g 3 3 100 " load resistance if!! 45 40 j5 ~ ... 3d ~ 25 vi ~ 20 0 15 10k 0 0,1 100d 10 100 ca~acitive load inf) output impedance vi frequency 0.001 10 100 1k 100 frequency (hzl look 1m -9- -- -- ------ 10m output voltage swing vs load resistance 15 - 14 ~ ,--i.-.' ~ 5 ~ 13 c z ~ 12 ...----- w " :: 11 oj 0 > ;; 10 l ; " 9 8 100 -ik load resistance i'" 10k maximum output swing vs frequency 30 , i t 1'111" avcl . 20 !i vs' "sv ii ta -, 2s'c i oc' 3-3>0 ! cc' lof ! rl' ikh ii t cl = loop, ii 1iii ! i!lli ~ 25 5 ~ w 20 ~ ::; ~ 15 .. " .. ~ 10 6 ... ,< .. ~ . i 1111 ; 0 100 1k 101< 1001< frequency 1..,1 1m --------- 140 120 100 ;; eo :!! z :( i!/i " 40 70 0 10 100 70 !fo 60 110 ;; a i 50 11/ 0 ;( 130;: c .. g 40 iso... oj ';l q ... :z: 3d 170 l :> 0 0,01 1== fa = 25'c vs' .isv == 1== ,i , , -1- i \1- -- j- -i --1 ii -- avcl - 1000 -- avcl 7 100 .. , - ; i i. i obsolete
analog devices fax-on-demand hotline - page 11 op-50 tcvos test circuit lookil 1%' ion 1"" h5v " 0.0'.' ~ ,on,lio' vo 1 -:- -isv 'vishav iv'e slltlk htsistors .."'..........._.... applications information high-sensitivity voltage comparator a comparator capable of resolving a submicrovolt difference signal is shown in figure 1. the op-so, operating without feedback, drives a second gain stage which generates a ttl- compatible output signal. schottky-clamp diodes prevent .t,o.,f 1.5hi 'unf figure 1: high-sensitivity voltage comparator - - --. ion' ceramic ~ overdriving of the long-tailed transistor pair and stop satura- tion of the output transistor. power supply voltage is set to ~5v to lower the quiescent power dissipation and minimize thermal feedback due to output stage dissipation. operating from :tsv supplies also reduces the op-so rise and fall times as the output slews over a reduced voltage range. this, in turn, reduces the output response time. it is common practice with voltage comparators to ground one input terminal and to use a single-ended input the historic reason is poor common-mode rejection on the input stage. in contrast, the op-so has very high common-mode rejection and is capable of detecting microvolt level differ- ences in the presence of large common-mode signals. the comparator is not fast, but it is very sensitive and can detect signal differences as low as o.3}lv. with large input overdrives, the circuit responds in approximately 311s. if sharp transitions are needed, the use of a ttl schmitt- trigger input is recommended. a table of response time vs. input overdrive is shown below. input overdrive positive output delay negative output delay 100l'v 3401'5 3801'5 10l'v 2.4ms 4.sms 10mv 51's sjls 1mv 401'5 soils 100mv 3.21'5 1.8jl5 .sv 2.2kn ttlcompatible oulplji 'n6263 2x 'n626j 82011 ov ":" 6v -10- ---- -- obsolete
analog devices fax-on-demand hotline - page 12 - op-50 integrator and unity-gain buffer figure 2 shows a method of obtaining unity-gain in a buffer configuration. the r1 and c1 network provides input com- pensation to circumvent the minimum gain requirement. figure 3 shows the same technique applied in the inverting mode to form a high precision integrator. ikj) ci voui ai v,n 0.1.' :1001'1 5ed!! figure 2: unity gain buffer c r vout v,n ci 0.1.' ai 10011 4.7n' 66011 ";' figure 3: integrator 20ma current source the 20ma current source exploits the high output current and high linearity capabilities of the op-50. five precision resistors and a trim potentiometer are required in this circuit configuration. known as the howland current pump. the trim potentiometer is used to balance the resistive feedback dividers. this maximizes the current-source output impe- dance. compensation is selected for a voltage gain of 10. compliance is better than:t1 1 v at an output current of 20ma and the trimmed output resistance is typically 2m!} with rl:5 500ft the transfer function is given by: v1n (dlff) x 10.1 amps 'out = 101 vin (dlffi is the differential input voltage. for the resistor values shown in figure 4. the maximum vin (diff) is 200mv. - ----- -- ------------ looin '01% 'out '...", i '010 ,on. 10k!! !.d.'" .i~v 10oon .0.1% z,!! rout trim howland current pump vol tagecompliance: ,,'.dv@jout'20ma output resistance, rout jat 'out' 20ma ano rl ",~,,), ~2mn stadle witt' atl vatues or capacitive load. figure 4: 20ma current source driving son loads the op-50can provide up to soma into a son load and up to 26ma into a soon load. the output is stable driving capacitive loads of up to 10nf. applications that make use of the high output current capa- bility of the op-50 will cause increased power dissipation in the amplifier. to reduce internal dissipation in these applica- tions. external voltage dropping resistors can be connected in series with the output-stage power supply pins. as shown in figure 5, 130h resistors can be attached to pin 7 (-vop) and to pin 10 (+vop). to maintain stability and specified perfor- mance levels, 0.047/lf decoupling capacitors should be used as indicated from pin 7 and pin 10 to ground. -in "~v vo -in !>on s load 5 '" i c3 ~h---1 non 0.047"1.c4 ~ ";' iii' 0.0""> -15v note: resistors ri and a2 reduce ic power dissipation. figure 5: driving son loads -- ---- obsolete
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