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EL2120c january 1996 rev e EL2120c 100 mhz current feedback amplifier note: all information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication; however, this data sheet cannot be a ``controlled document''. current revisions, if any, to these specifications are maintained at the factory and are available upon your request. we recommend checking the revision level before finalization of your design documentation. ? 1991 elantec, inc. features # excellent differential gain and phase on g 5v to g 15v supplies # 100 mhz b 3 db bandwidth from gains of g 1to g 10 # 700 v/ m s slew rate # 0.1 db flatness to 20 mhz # output disable in 50 ns - remains high impedance even when driven with large slew rates # single a 5v supply operation # ac characteristics are lot and temperature stable # available in small so-8 package applications # video gain block # residue amplifier # multiplexer # current to voltage converter # coax cable driver with gain of 2 # adc driver ordering information part no. temp. range package outline y EL2120cn 0 cto a 75 c 8-pin p-dip mdp0031 EL2120cs 0 cto a 75 c 8-lead so mdp0027 connection diagrams p-dip 2120 1 so 2120 2 top view general description the EL2120c is a wideband current feedback amplifier opti- mized for video performance. its 0.01% differential gain and 0.03 degree differential phase performance when at g 5v sup- plies exceeds the performance of other amplifiers running on g 15v supplies. operating on g 8to g 15v supplies reduces dis- tortions to 0.01% and 0.01 degrees and below. the EL2120c can operate with supplies as low as g 2.5v or a single a 5v supply. being a current feedback design, bandwidth is a relatively con- stant 100 mhz over the g 1to g 10 gain range. the EL2120c has been optimized for flat gain over frequency and all charac- teristics are maintained at positive unity gain. because the in- put slew rate is similar to the 700 v/ m s output slew rate the part makes an excellent high-speed buffer. the EL2120c has a superior output disable function. time to enable or disable is 50 ns and does not change markedly with temperature. furthermore, in disable mode the output does not draw excessive currents when driven with 1000 v/ m s slew rates. the output appears a sa3pf load when disabled. simplified schematic 2120 21
EL2120c 100 mhz current feedback amplifier absolute maximum ratings (t a e 25 c) voltage between v a and v b 33v voltage at a in, b in, v out (v b ) b 0.5v to (v a ) a 0.5v voltage between a in and b in g 5v voltage at /disable (v a ) b 10v to (v a ) a 0.5v current into a in, b in, and /disable g 5ma output current g 50 ma internal power dissipation see curves operating ambient temperature range 0 to 75 c operating junction temperature p-dip or so 150 c storage temperature range b 65 cto a 150 c important note: all parameters having min/max specifications are guaranteed. the test level column indicates the specific device testing actually performed during production and quality inspection. elantec performs most electrical tests using modern high-speed automatic test equipment, specifically the ltx77 series system. unless otherwise noted, all tests are pulsed tests, therefore t j e t c e t a . test level test procedure i 100% production tested and qa sample tested per qa test plan qcx0002. ii 100% production tested at t a e 25 c and qa sample tested at t a e 25 c, t max and t min per qa test plan qcx0002. iii qa sample tested per qa test plan qcx0002. iv parameter is guaranteed (but not tested) by design and characterization data. v parameter is typical value at t a e 25 c for information purposes only. open loop dc electrical characteristics v s e g 5v; r l e 150 x ,t a e 25 c unless otherwise specified parameter description temp min typ max test units level v os input offset voltage full 4 20 ii mv v s e g 15v full 2 25 ii mv d v os / d t input offset drift full 20 v m v/ c i b a a v in input bias current full 5 15 ii m a i b b b v in input bias current full 10 50 ii m a cmrr common-mode rejection full 50 55 ii db (note 1) b icmr b input current common-mode full 8 20 ii m a/v rejection (note 1) psrr power supply rejection full 65 80 ii db (note 2) a ipsr a input current power supply 25 c 0.03 v m a/v rejection (note 2) b ipsr b input current power supply full 0.6 5 ii m a/v rejection (note 2) r ol transimpedance full 70 140 ii k x a vol voltage gain full 58 66 ii db a r in a v in input impedance 25 c2 vm x 2 td is 3.2in
EL2120c 100 mhz current feedback amplifier open loop dc electrical characteristics e contd. v s e g 5v; r l e 150 x ,t a e 25 c unless otherwise specified parameter description temp min typ max test units level v in a v in range full g 3.0 g 3.5 ii v v o output voltage swing full g 3.0 g 3.5 ii v i sc output short-circuit 25 c 100 ii ma current i o,dis output current, disabled full 5 50 ii m a v dis,on disable pin voltage for full (v a ) b 1iiv output enabled v dis,off disable pin voltage for full (v a ) b 4ii v output disabled i dis,on disable pin current for full 5 ii m a output enabled i dis,off disable pin current for full 1.0 ii ma output disabled i s supply current (v s e g 15v) full 17 20 ii ma note 1: the input is moved from b 3v to a 3v. note 2: the supplies are moved from g 5v to g 15v. closed loop ac electrical characteristics v s e g 15v; a v ea 2(r f e r g e 270 x ); r l e 150 x ;c l e 7 pf; c in b e 2 pf; t a e 25 c parameter description min typ max test units level sr slew rate; v out from b 3v to a 3v measured at b 2v and a 2v v s e g 15v 750 v v/ m s v s e g 5v 550 v v/ m s t s settling time to 0.25% of a 0to a 10v swing; a v ea 1 with r f e 270 x ,r g e % , and r l e 400 x 50 v ns bw bandwidth b 3 db 95 v mhz g 1 db 50 v mhz g 0.1 db 16 v mhz bw @ 2.5v bandwidth at b 3 db 75 v mhz v s e g 2.5v g 1 db 35 v mhz g 0.1 db 11 v mhz peaking 0.5 v db 3 td is 2.7in td is 2.4in
EL2120c 100 mhz current feedback amplifier closed loop ac electrical characteristics e contd. v s e g 15v; a v ea 2(r f e r g e 270 x ); r l e 150 x ;c l e 7 pf; c in b e 2 pf; t a e 25 c parameter description min typ max test units level dg differential gain; dc offset from b 0.7v through a 0.7v, ac amplitude 286 mvp p v s e g 15v, f e 3.58 mhz k 0.01 v % v s e g 15v, f e 30 mhz 0.1 v % v s e g 5v, f e 3.58 mhz 0.01 v % d i differential phase; dc offset from b 0.7v through a 0.7v, ac amplitude 286 mvp p v s e g 15v, f e 3.58 mhz 0.01 v v s e g 15v, f e 30 mhz 0.1 v v s e g 5v, f e 3.58 mhz 0.06 v typical performance curves ac test circuit 2120 3 frequency response vs r f 2120 4 frequency response vs gain 2120 5 frequency response vs load 2120 6 4 td is 2.0in
EL2120c 100 mhz current feedback amplifier typical performance curves e contd. gain flatness vs r f gain flatness vs c in b at v s g 15v and peaking vs temperature b 3 db bandwidth, 0.1 db bandwidth, at v s g 5v and peaking vs temperature b 3 db bandwidth, 0.1 db bandwidth, peaking vs supply voltage 0.1 db bandwidth, and b 3 db bandwidth, phase vs frequency deviation from linear 2120 7 5
EL2120c 100 mhz current feedback amplifier typical performance curves e contd. at 3.58 mhz dc input offset differential gain vs at 3.58 mhz dc input offset differential phase vs at 30 mhz dc input offset differential gain vs at 30 mhz dc input offset differential phase vs (v in ,dcfrom0to a 0.7v) vs supply voltage differential gain and phase and current input noise voltage 2120 8 6
EL2120c 100 mhz current feedback amplifier typical performance curves e contd. swing vs frequency undistorted output slew rate vs temperature 2120 9 small-signal transient response 2120 10 a v ea 2, r f e r g e 270 x , r l e 150 x large-signal transient response 2120 11 a v ea 2, r f e r g e 270 x , r l e 150 x ,v s e g 15v settling time vs swing long term settling error 2120 12 7
EL2120c 100 mhz current feedback amplifier typical performance curves e contd. enable response for a family of inputs 2120 13 a v ea 2, r l e 150 x , v s e g 5v disable response for a family of inputs a v ea 2, r l e 150 x , 2120 14 v s e g 5v supply voltage supply current vs maximum power dissipation 8-pin plastic dip vs ambient temperature 8-lead so vs ambient temperature maximum power dissipation 2120 15 8
EL2120c 100 mhz current feedback amplifier applications information the EL2120c represents the third generation of current-feedback amplifier design. it is designed to provide good high-frequency performance over wide supply voltage, load impedance, gain, tem- perature, and manufacturing lot variations. it is a well-behaved amplifier in spite of its 100 mhz bandwidth, but a few precautions should be tak- en to obtain maximum performance. the power supply pins must be well bypassed. 0.01 m f ceramic capacitors are adequate, but lead length should be kept below (/4 and a ground plane is recommended. bypassing with 4.7 m f tantalum capacitors can improve settling charac- teristics, and smaller capacitors in parallel will not be needed. the lead length of sockets general- ly deteriorates the amplifier's frequency response by exaggerating peaking and increasing ringing in response to transients. short sockets cause lit- tle degradation. load capacitance also increases ringing and peaking. capacitance greater than 35 pf should be isolated with a series resistor. capacitance at the v in b terminal has a similar effect, and should be kept below 5 pf. often, the inductance of the leads of a load capacitance will be self-reso- nant at frequencies from 40 mhz to 200 mhz and can cause oscillations. a resonant load can be de-q'ed with a small series or parallel resistor. a ``snubber'' can sometimes be used to reduce reso- nances. this is a resistor and capacitor in series connected from output to ground. values of 68 x and 33 pf are typical. increasing the feedback resistor can also improve frequency flatness. the v in a pin can oscillate in the 200 mhz to 500 mhz realm if presented with a resonant or inductive source impedance. a series 27 x to 68 x resistor right on the v in a pin will suppress such oscillations without affecting frequency response. b 3 db bandwidth is inversely proportional to the value of feedback resistor r f . the EL2120c will tolerate values as low as 180 x for a maxi- mum bandwidth of about 140 mhz, but peaking will increase and tolerance to stray capacitance will reduce. at gains greater than 5, b 3 db band- width begins to reduce, and a smaller r f can be used to maximize frequency response. the greatest frequency response flatness (to 0.1 db, for instance) occurs with r f e 300 x to 330 x . even the moderate peaking caused by low- er values of r f will cause the gain to peak out of the 0.1 db window, and higher values of r f will cause an overcompensated response where the gain falls below the 0.1 db level. parasitic capaci- tances will generally degrade the frequency flat- ness. the EL2120c should not output a continuous current above 50 ma, as stated in the abso- lute maximum ratings table. the out- put current limit is set to 120 ma at a die temper- ature of 25 c and reduces to 85 ma at a die tem- perature of 150 c. this large current is needed to slew load capacitance and drive low impedance loads with low distortion but cannot be support- ed continuously. furthermore, package dissipa- tion capabilities cannot be met under short-cir- cuit conditions. current limit should not occur longer than a few seconds. the output disable function of the EL2120c is optimized for video performance. while in dis- able mode, the feedthrough of the circuit can be modeled as a 0.2 pf capacitor from v in a to the output. no more than g 5v can be placed be- tween v in a and v in b in disable mode, but this is compatible with common video signal levels. in disabled state the output can withstand about 1000 v/ m s slew rate signals impressed on it with- out the output transistors turning on. the /disable pin logic level is referred to v a . with g 5v supplies, a cmos or ttl driver with pull-up resistor will suffice. g 15v supplies re- quire a a 14/ a 11v drive span, or a 15/ a 10v nominally. open-collector ttl with a tapped pull-up resistor can provide these spans. the im- pedance of the divider should be 1k or less for optimum enable/disable speed. the EL2120c enables in 50 ns or less. when v in e 0, only a small switching glitch occurs at the output. when v in is some other value, the out- put overshoots by about 0.7v when settling toward its new enabled value. 9
EL2120c 100 mhz current feedback amplifier applications information e contd. when the EL2120c disables, it turns off very rapidly for inputs of g 1v or less, and the output sags more slowly for inputs larger than this. for inputs as large as g 2.5v the output current can be absorbed by another EL2120c simultaneously enabled. under these conditions, switching will be prop- erly completed in 50 ns or less. the greater thermal resistance of the so-8 package requires that the EL2120c be operated from g 10v supplies or less to maintain the 150 c maximum die temperature over the commercial temperature range. the p-dip package allows the full g 16.5v supply operation. typical applications circuitea high quality two-input multiplexer dual EL2120c multiplexer 2120 16 channel-to-channel isolation of dual EL2120c multiplexer 2120 17 dual EL2120c multiplexer switching channels: uncorrelated sinewave switched to a family of dc levels 2120 18 dual EL2120c multiplexer switching channels: a family of dc levels switched to an uncorrelated sinewave 2120 19 10
EL2120c 100 mhz current feedback amplifier the EL2120c macromodel this macromodel has been developed to assist the user in simulating the EL2120c with surrounding circuitry. it was developed for the pspice simulator (copywritten by the microsim corporation), and may need to be rearranged for other simulators, particularly the h operator. it approximates frequency response and small-signal transients as well, although the effects of load capacitance does not show. this model is slightly more complicated than the models used for low-frequency op-amps, but is much more accurate for ac. the model does not simulate these characteristics accurately: noise non-linearities slew rate limitations temperature effects settling time manufacturing variations input or output resonances cmrr and psrr * revision a. march 1992 * enhancements include psrr, cmrr, and slew rate limiting * connections: a input * l b input * ll a vsupply * lll b vsupply * llll output * lllll .subckt m2120 3 2746 * * input stage * * q141819qp e1100301.0 q271820qn vis1090v q371921qn h2912vxx1.0 q442022qp r121125 r72164 l1 11 12 20nh r8 22 6 4 iinp3010 m a ios1 7 19 2.5ma iinm205 m a ios2 20 4 2.5ma r12 3 0 2meg * ** supply * slew rate limiting * * ips 7 4 10ma h1 13 0 vis 600 * r2 13 14 1k * error terms d1 14 0 dclamp * s2 0 14 dclamp ivos 0 23 5ma * vxx 23 0 0v * high frequency pole e4 2 40601.0 * e5250701.0 e2 30 0 14 0 0.00166666666 e6 2 60401.0 15 30 17 1 m h r92423562 c5 17 0 0.5pf r10 25 23 10k r5 17 0 600 r11 26 23 10k ** * transimpedance stage * models ** g1 0 18 17 0 1.0 .model qn npn (is e 5e b 15 bf e 500 tf e 0.1ns) rol 18 0 140k .model qp pnp (is e 5e b 15 bf e 500 tf e 0.1ns) cdp 18 0 7.9pf .model dclamp d(is e 1e b 30 ibv e 0.02 bv e 4n e 4) * .ends * output stage 11 tab wide td is 3.8in td
EL2120c january 1996 rev e EL2120c 100 mhz current feedback amplifier the EL2120c macromodel e contd. 2120 20 EL2120 macromodel general disclaimer specifications contained in this data sheet are in effect as of the publication date shown. elantec, inc. reserves the right to make changes in the circuitry or specifications contained herein at any time without notice. elantec, inc. assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. elantec, inc. 1996 tarob court milpitas, ca 95035 telephone: (408) 945-1323 (800) 333-6314 fax: (408) 945-9305 european office: 44-71-482-4596 warning e life support policy elantec, inc. products are not authorized for and should not be used within life support systems without the specific written consent of elantec, inc. life support systems are equipment in- tended to support or sustain life and whose failure to perform when properly used in accordance with instructions provided can be reasonably expected to result in significant personal injury or death. users contemplating application of elantec, inc. products in life support systems are requested to contact elantec, inc. factory headquarters to establish suitable terms & conditions for these applications. elantec, inc.'s warranty is limited to replace- ment of defective components and does not cover injury to per- sons or property or other consequential damages. printed in u.s.a. 12

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