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_______________general description the MAX477 is a ?v wide-bandwidth, fast-settling, unity-gain-stable op amp featuring low noise, low differ- ential gain and phase errors, high slew rate, high preci- sion, and high output current. the MAX477? archi- tecture uses a standard voltage-feedback topology that can be configured into any desired gain setting, as with other general-purpose op amps. unlike high-speed amplifiers using current-mode feed- back architectures, the MAX477 has a unique input stage that combines the benefits of the voltage-feed- back design (flexibility in choice of feedback resistor, two high-impedance inputs) with those of the current- feedback design (high slew rate and full-power band- width). it also has the precision of voltage-feedback amplifiers, characterized by low input-offset voltage and bias current, low noise, and high common-mode and power-supply rejection. the MAX477 is ideally suited for driving 50 or 75 loads. available in dip, so, space-saving ?ax, and sot23 packages. ________________________applications broadcast and high-definition tv systems video switching and routing communications medical imaging precision dac/adc buffer ____________________________features ? high speed: 300mhz -3db bandwidth (a v = +1) 200mhz full-power bandwidth (a v = +1, v o = 2vp-p) 1100v/? slew rate 130mhz 0.1db gain flatness ? drives 100pf capacitive loads without oscillation ? low differential phase/gain error: 0.01?0.01% ? 8ma quiescent current ? low input-referred voltage noise: 5nv/ h h z z ? low input-referred current noise: 2pa/ h h z z ? low input offset voltage: 0.5mv ? 8000v esd protection ? voltage-feedback topology for simple design configurations ? short-circuit protected ? available in space-saving sot23 package MAX477 300mhz high-speed op amp ________________________________________________________________ maxim integrated products 1 19-0467; rev 2; 5/97 part MAX477epa MAX477esa MAX477eua -40? to +85? -40? to +85? -40? to +85? temp. range pin- package 8 plastic dip 8 so 8 ?ax evaluation kit manual available ______________ordering information out in+ n.c. v ee 1 2 8 7 n.c. v cc in- n.c. dip/so/ m max top view 3 4 6 5 v ee in- in+ 15 v cc out MAX477 MAX477 sot23-5 2 34 __________________pin configuration v in video/rf cable driver 500 w 500 w 75 w 75 w v out 75 w MAX477 __________typical operating circuit MAX477mja -55? to +125? 8 cerdip MAX477euk-t -40? to +85? 5 sot23 sot top mark abyw for free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. for small orders, phone 408-737-7600 ext. 3468.
open-loop voltage gain MAX477 300mhz high-speed op amp 2 _______________________________________________________________________________________ absolute maximum ratings dc electrical characteristics (v cc = +5v, v ee = -5v, v out = 0v, r l = , t a = t min to t max, unless otherwise noted. typical values are at t a = +25 c.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. supply voltage (v cc to v ee ) .................................................. 12v differential input voltage .................. (v cc + 0.3v) to (v ee - 0.3v) common-mode input voltage .......... (v cc + 0.3v) to (v ee - 0.3v) output short-circuit duration to gnd ........................ continuous continuous power dissipation (t a = +70 c) plastic dip (derate 9.09mw/ c above +70 c) .............. 727mw so (derate 5.88mw/ c above +70 c) .......................... 471mw max (derate 4.1mw/ c above +70 c) ....................... 330mw cerdip (derate 8.00mw/ c above +70 c) .................. 640mw sot23 (derate 7.1mw/ c above +70 c) ...................... 571mw operating temperature ranges MAX477e_a ...................................................... -40 c to +85 c MAX477euk ..................................................... -40 c to +85 c MAX477mja ................................................... -55 c to +125 c storage temperature range ............................. -65 c to +160 c lead temperature (soldering, 10sec) ............................. +300 c MAX477esa/epa/eua/mja MAX477mja, t a = t min to t max MAX477e_ _, t a = t min to t max t a = +25 c v out = 0, f = dc t a = t min to t max t a = +25 c short to ground either input t a = +25 c t a = +25 c conditions ma 14 i sy quiescent supply current 12 ma 8 10 0.1 r out open-loop output resistance ma 150 i sc short-circuit output current v 2.5 v out output voltage swing 3.0 3.5 3.9 0.5 2.0 v 2.5 v cm common-mode input voltage range 3.0 3.5 m 1 r in(dm) differential-mode input resistance v/ c 2 tcv os input offset-voltage drift 1 3 units min typ max symbol parameter t a = +25 c 0.2 1.0 t a = +25 c db 60 cmrr common-mode rejection ratio 70 90 v s = 4.5v to 5.5v db psrr power-supply rejection ratio 70 85 55 65 t a = -40 c to +85 c ma 70 100 i out minimum output current t a = t min to t max MAX477euk 0.5 2.0 mv a 5.0 t a = t min to t max i b input bias current input offset current i os t a = t min to t max 2.0 a v cm = 3v v cm = 2.5v r l = r l = 100 r l = 50 t a = t min to t max MAX477esa/epa/eua/mja input offset voltage v os MAX477euk 5.0 3.0 t a = +25 c t a = t min to t max v out = 2.0v, v cm = 0v, r l = 50 db 50 65 a vol open-loop voltage gain MAX477euk MAX477e_a/477mja
MAX477 300mhz high-speed op amp _______________________________________________________________________________________ 3 ac electrical characteristics (v cc = +5v, v ee = -5v, r l = 100 , a vcl = +1, t a = +25 c, unless otherwise noted.) note 1: specifications for the MAX477euk (sot23 package) are 100% tested at t a = +25 c, and guaranteed by design over temperature. note 2: maximum ac specifications are guaranteed by sample test on the MAX477esa only. note 3: tested with a 3.58mhz video test signal with an amplitude of 40ire superimposed on a linear ramp (0 to 100ire). an ire is a unit of video-signal amplitude developed by the institute of radio engineers. 140ire = 1v. conditions 220 300 units min typ max symbol parameter 30 130 small-signal, 0.1db gain flatness (note 2) f = 10mhz v out = 2v step v out = 2v step nv/ hz 5 e n input voltage noise density ns 2 t r , t f v out = 2vp-p rise time, fall time 12 v out = 2vp-p t s settling time ns 10 v/ s 700 1100 sr slew rate (note 2) mhz 200 fpbw full-power bandwidth f = 3.58mhz f = 10mhz, either input % 0.01 dg differential gain (note 3) pa/ hz 2 i n input current noise density either input f = 3.58mhz pf 1 c in(dm) differential-mode input capacitance degrees 0.01 dp differential phase (note 3) f c = 10mhz, v out = 2vp-p f = 10mhz db -58 thd total harmonic distortion 2.5 z out output impedance to 0.1% to 0.01% f = 10mhz, v out = 2vp-p f = 5mhz, v out = 2vp-p dbm 36 ip3 third-order intercept dbc -74 sfdr spurious-free dynamic range __________________________________________ t ypical operating characteristics (v cc = +5v, v ee = -5v, r l = 100 , c l = 0pf, t a = +25 c, unless otherwise noted.) 1 2 0 -1 -2 1m 10m 100m 1g small-signal gain vs. frequency (a vcl = +1v/v) -6 -7 -8 -3 -4 -5 MAX477-01 frequency (hz) gain (db) 6 7 8 5 4 3 1m 10m 100m 1g small-signal gain vs. frequency (a vcl = +2v/v) -1 -2 2 1 0 MAX477-02 frequency (hz) gain (db) 20 21 22 19 18 17 100k 1m 10m 100m small-signal gain vs. frequency (a vcl = +10v/v) 13 12 16 15 14 MAX477-03 frequency (hz) gain (db) v out 0.1vp-p mhz bw -3db small-signal, -3db bandwidth (note 2) bw 0.1db v out 0.1vp-p mhz
MAX477 300mhz high-speed op amp 4 _______________________________________________________________________________________ ____________________________ t ypical operating characteristics (continued) (v cc = +5v, v ee = -5v, r l = 100 , c l = 0pf, t a = +25 c, unless otherwise noted.) 0 0.1 0.2 -0.1 -0.2 -0.3 1m 10m 100m 1g gain flatness vs. frequency (a vcl = +1v/v) -0.4 -0.5 -0.6 MAX477-04 frequency (hz) gain (db) 1 2 3 0 -1 -2 1m 10m 100m 1g large-signal gain vs. frequency (a vcl = +1v/v) -3 -4 -5 -6 MAX477-05 frequency (hz) gain (db) small-signal pulse response (a vcl = +1v/v) time (10ns/div) voltage (100mv/div) gnd gnd in out small-signal pulse response (a vcl = +2v/v) time (10ns/div) voltage gnd gnd in (50mv/ div) out (100mv/ div) large-signal pulse response (a vcl = +2v/v) time (10ns/div) voltage gnd gnd in (1v/div) out (2v/div) small-signal pulse response (a vcl = +10v/v) time (50ns/div) voltage gnd gnd in (50mv/ div) out (500mv/ div) large-signal pulse response (a vcl = +1v/v) time (10ns/div) voltage (2v/div) gnd gnd in out large-signal pulse response (a vcl = +10v/v) time (50ns/div) voltage gnd gnd in (200mv/ div) out (2v/div) small-signal pulse response (a vcl = +1v/v, c l = 50pf) time (20ns/div) voltage (100mv/div) gnd gnd in out
MAX477 300mhz high-speed op amp _______________________________________________________________________________________ 5 small-signal pulse response (a vcl = +1v/v, c l = 100pf) time (20ns/div) voltage (100mv/div) gnd gnd in out large-signal pulse response (a vcl = +1v/v, c l = 50pf) time (20ns/div) voltage (2v/div) gnd gnd in out large-signal pulse response (a vcl = +1v/v, c l = 100pf) time (20ns/div) voltage (2v/div) gnd gnd in out -50 input bias current (i b ) vs. temperature MAX477-19 temperature (?c) input bias current (?) 0.5 0 1.0 1.5 2.0 2.5 3.0 3.5 -25 0 25 50 75 125 100 v cm = 0v -50 input offset voltage (v os ) vs. temperature MAX477-17 temperature (?c) input offset voltage (?) -200 -300 -100 0 100 200 300 400 -25 0 25 50 75 125 100 v cm = 0v -50 quiescent supply current (i sy ) vs. temperature MAX477-18 temperature (?c) quiescent supply current (ma) 2 0 4 6 8 10 12 14 -25 0 25 50 75 125 100 -50 output voltage swing vs. temperature MAX477-20 temperature (?c) output voltage swing (?) 3.0 2.5 3.5 4.0 -25 0 25 50 75 125 100 r l = r l = 100 w r l = 50 w 8 -50 input common-mode range (v cm ) vs. temperature MAX477-21 temperature (?c) common-mode range (?) 3.2 3.8 3.6 3.4 3.0 2.8 4.0 4.2 -25 0 25 50 75 125 100 ____________________________ t ypical operating characteristics (continued) (v cc = +5v, v ee = -5v, r l = 100 , c l = 0pf, t a = +25 c, unless otherwise noted.)
MAX477 300mhz high-speed op amp 6 _______________________________________________________________________________________ ____________________________ t ypical operating characteristics (continued) (v cc = +5v, v ee = -5v, r l = 100 , c l = 0pf, t a = +25 c, unless otherwise noted.) -30 -20 -110 -50 -70 -90 30k 100k 1m 10m 100m power-supply rejection vs. frequency -100 MAX477-22 frequency (hz) power supply rejectjion ( db ) -80 -60 -40 1k 0.1 100k 1m 10m 100m 500m output impedance vs. frequency 1 MAX477-23 frequency (hz) output impedance ( w ) 10 100 -20 -100 1k 10k 1m 10m 100k 100m harmonic distortion vs. frequency -80 MAX477-24 frequency (hz) distortion (db) -60 -40 total harmonic distortion second harmonic third harmonic 50m open-loop gain and phase vs. frequency MAX477-16 frequency (hz) open-loop gain (db) phase (degrees) -8 -10 -4 0 4 8 6 2 -2 -6 10 360 180 0 -180 -360 100m 500m gain phase 0.004 0.002 0.000 0.006 -0.004 0 100 0 100 differential gain and phase (a vcl = +1, r l = 150 w ) 0.000 -0.002 -0.002 -0.004 ire ire diff phase (deg) diff gain (%) 0.006 0.004 0.002 MAX477-25 0.000 -0.004 0.004 0 100 0 100 differential gain and phase (a vcl = +2, r l = 150 w ) 0.000 -0.001 -0.002 -0.008 -0.012 ire ire diff phase (deg) diff gain (%) 0.003 0.002 0.001 MAX477-26
MAX477 300mhz high-speed op amp _______________________________________________________________________________________ 7 _______________ detailed description the MAX477 allows the flexibility and ease of a classic voltage-feedback architecture while maintaining the high-speed benefits of current-mode feedback (cmf) amplifiers. although the MAX477 is a voltage-feedback op amp, its internal architecture provides an 1100v/ s slew rate and a low 8ma supply current. cmf ampli - fiers offer high slew rates while maintaining low supply current, but use the feedback and load resistors as part of the amplifier? frequency compensation network. in addition, they have only one input with high imped - ance. the MAX477 has speed and power specifications like those of current-feedback amplifiers, but has high input impedance at both input terminals. like other voltage- feedback op amps, its frequency compensation is independent of the feedback and load resistors, and it exhibits a constant gain-bandwidth product. however, unlike standard voltage-feedback amplifiers, its large- signal slew rate is not limited by an internal current source, so the MAX477 exhibits a very high full-power bandwidth. output short-circuit protection under short-circuit conditions, the output current is typi - cally limited to 150ma. this is low enough that a short to ground of any duration will not cause permanent dam - age to the chip. however, a short to either supply will significantly increase the power dissipation and may cause permanent damage. the high output- current capability is an advantage in systems that trans - mit a signal to several loads. see high-performance video distribution amplifier in the applications information section. __________ applications infor mation grounding, bypassing, and pc board layout to obtain the MAX477? full 300mhz bandwidth, micro- strip and stripline techniques are recommended in most cases. to ensure the pc board does not degrade the amplifier? performance, design the board for a fre - quency greater than 1ghz. even with very short traces, use these techniques at critical points, such as inputs and outputs. whether you use a constant-impedance board or not, observe the following guidelines when designing the board: do not use wire-wrap boards. they are too inductive. do not use ic sockets. they increase parasitic capacitance and inductance. in general, surface-mount components have shorter leads and lower parasitic reactance, giving better high-frequency performance than through-hole com - ponents. the pc board should have at least two layers, with one side a signal layer and the other a ground plane. keep signal lines as short and straight as possible. do not make 90 turns; round all corners. the ground plane should be as free from voids as possible. _____________________ pin description MAX477 v out = -(r f /r g ) v in v out v in r f r g figure 1a. inverting gain configuration MAX477 v out = [1 + (r f /r g )] v in v out v in r f r g figure 1b. noninverting gain configuration amplifier output 1 6 positive power supply 5 7 negative power supply 2 4 noninverting input 3 3 pin so/ max/dip inverting input 4 2 no connect. not inter - nally connected. 1, 5, 8 function sot23 out v cc v ee in+ in- n.c. name
MAX477 300mhz high-speed op amp 8 _______________________________________________________________________________________ setting gain the MAX477 can be configured as an inverting or non - inverting gain block in the same manner as any other voltage-feedback op amp. the gain is determined by the ratio of two resistors and does not affect amplifier frequency compensation. this is unlike cmf op amps, which have a limited range of feedback resistors, typi - cally one resistor value for each gain and load setting. this is because the -3db bandwidth of a cmf op amp is set by the feedback and load resistors. figure 1a shows the inverting gain configuration and its gain equation, while figure 1b shows the noninverting gain configuration. choosing resistor values the feedback and input resistor values are not critical in the inverting or noninverting gain configurations (as with current-feedback amplifiers). however, be sure to select resistors that are small and noninductive. surface-mount resistors are best for high-frequency cir - cuits. their material is similar to that of metal-film resis - tors, but to minimize inductance, it is deposited in a flat, linear manner using a thick film. their small size and lack of leads also minimize parasitic inductance and capacitance. the MAX477? input capacitance is approximately 1pf. in either the inverting or noninverting configuration, excess phase resulting from the pole frequency formed by r f || r g and c can degrade amplifier phase margin and cause oscillations (figure 2). table 1 shows the recommended resistor combinations and measured bandwidth for several gain values. dc and noise errors the standard voltage-feedback topology of the MAX477 allows dc error and noise calculations to be done in the usual way. the following analysis shows that the MAX477? voltage-feedback architecture pro - vides a precision amplifier with significantly lower dc errors and lower noise compared to cmf amplifiers. 1) in figure 3, total output offset error is given by: for the special case in which r s is arranged to be equal to r f || rg, the i b terms cancel out. note also, for i os (r s + (r f || rg) << v os , the i os term also drops out of the equation for total dc error. in prac - tice, high-speed configurations for the MAX477 necessitate the use of low-value resistors for r s , r f , and rg. in this case, the v os term is the dominant dc error source. 2) the MAX477? total input-referred noise in a closed- loop feedback configuration can be calculated by: where e n = input-referred noise voltage of the MAX477 (5nv hz ) i n = input-referred noise current of the MAX477 (2pa hz ) r eq = total equivalent source resistance at the two inputs, i.e., r eq = r s + r f || r g e r = resistor noise voltage due to r eq , i.e., MAX477 v out v in c r f r g r l figure 2. effect of high-feedback resistor values and parasitic capacitance on bandwidth table 1. resistor and bandwidth values for various closed-loop gain configurations v = 1 + r r out f g || || ? ? + ( ) + + ( ) ( ) ? ? v i r i r r i r r r os b s b f g os s f g e e e i r t n r n eq = + + ( ) ? ? 2 2 2 114 64 42 23 12 25 120 300 -3db bandwidth (mhz) 300 300 500 500 450 500 500 short r f ( ) 300 -1 150 -2 100 -5 50 -10 50 +10 125 +5 gain (v/v) 500 +2 open +1 r g ( ) e = 4kt r r eq
MAX477 300mhz high-speed op amp _______________________________________________________________________________________ 9 as an example, consider r s = 75 , r f = r g = 500 . then: 3) the MAX477? output-referred noise is simply total input-referred noise, e t , multiplied by the gain factor: in the above example, with e t = 5.5nv h z , and assum - ing a signal bandwidth of 300mhz (471mhz noise bandwidth), total output noise in this bandwidth is: note that for both dc and noise calculations, errors are dominated by offset voltage (v os ) and input noise volt - age (e n ). for a current-mode feedback amplifier with offset and noise errors significantly higher, the calcula - tions are very different. driving capacitive loads the MAX477 provides maximum ac performance with no output load capacitance. this is the case when the MAX477 is driving a correctly terminated transmission line (i.e., a back-terminated 75 cable). however, the MAX477 is capable of driving capacitive loads up to 100pf without oscillations, but with reduced ac perfor - mance. driving large capacitive loads increases the chance of oscillations in most amplifier circuits. this is especially true for circuits with high loop gain, such as voltage fol - lowers. the amplifier? output resistance and the load capacitor combine to add a pole and excess phase to the loop response. if the frequency of this pole is low enough and phase margin is degraded sufficiently, oscillations may occur. a second problem when driving capacitive loads results from the amplifier? output impedance, which looks inductive at high frequency. this inductance forms an l-c resonant circuit with the capacitive load, which causes peaking in the frequency response and degrades the amplifier? gain margin. the MAX477 drives capacitive loads up to 100pf with - out oscillation. however, some peaking (in the frequen - cy domain) or ringing (in the time domain) may occur. this is shown in figure 4 and the in the small and large-signal pulse response graphs in the typical operating characteristics . to drive larger-capacitance loads or to reduce ringing, add an isolation resistor between the amplifier? output and the load, as shown in figure 5. the value of r iso depends on the circuit? gain and the capacitive load. figure 6 shows the bode plots that result when a 20 isolation resistor is used with a volt - age follower driving a range of capacitive loads. at the higher capacitor values, the bandwidth is dominated by the rc network, formed by r iso and c l ; the bandwidth of the amplifier itself is much higher. note that adding an isolation resistor degrades gain accuracy. the load and isolation resistor form a divider that decreases the voltage delivered to the load. r e kt x nv hz at c e nv nv pa x nv hz eq r t = + ( ) = = = = ( ) + ( ) + ( ) = 75 500 500 325 4 325 2 3 25 5 2 3 2 325 5 5 2 2 2 w w w w . / . . || e = 5.5nv x out 1 500 500 471 239 + ? ? = x mhz v rms m e = e 1 + r r out t f g ? ? MAX477 v out i b- i b+ r f r g r s v in figure 3. output offset voltage figure 4. effect of c load on frequency response (a vcl = +1v/v) 15 10 5 0 1m 10m 100m 1g -20 -5 -10 -15 frequency (hz) gain (db) c l = 100pf c l = 22pf c l = 41pf c l = 0pf
MAX477 300mhz high-speed op amp 10 ______________________________________________________________________________________ flash adc preamp the MAX477? high output-drive capability and ability to drive capacitive loads make it well suited for buffer - ing the low-impedance input of a high-speed flash adc. with its low output impedance, the MAX477 can drive the inputs of the adc while maintaining accuracy. figure 7 shows a preamp for digitizing video, using the 250msps max100 and the 500msps max101 flash adcs. both of these adcs have a 50 input resistance and a 1.2ghz input bandwidth. high-performance video distribution amplifier in a gain of +2 configuration, the MAX477 makes an excellent driver for back-terminated 75 video coaxial cables (figure 8). the high output-current drive allows the attachment of up to six 2vp-p, 150 loads to the MAX477 at +25 c. with the output limited to 1vp-p, the number of loads may double. the max4278 is a similar amplifier configured for a gain of +2 without the need for external gain-setting resistors. for multiple gain-of-2 video line drivers in a single package, see the max496/max497 data sheet. wide-bandwidth bessel filter two high-impedance inputs allow the MAX477 to be used in all standard active filter topologies. the filter design is straightforward because the component val - ues can be chosen independently of op amp bias. figure 9 shows a wide-bandwidth, second-order bessel filter using a multiple feedback topology. the compo - nent values are chosen for a gain of +2, a -3db band - width of 10mhz, and a 28ns delay. figure 10a shows a square-wave pulse response, and figure 10b shows the filter? frequency response and delay. notice the flat delay in the passband, which is characteristic of the bessel filter. MAX477 v out v in r iso c l r l figure 5. capacitive-load driving circuit MAX477 video in 75 w 500 w 500 w 75 w 75 w 75 w 75 w 75 w 75 w 75 w 75 w out1 out2 outn figure 8. high-performance video distribution amplifier MAX477 video in 500 w 500 w flash adc (max100/max101) figure 7. preamp for video digitizer figure 6. effect of c load on frequency response with isolation resistor 1 0 -1 -2 1m 10m 100m 1g -6 -3 -4 -5 frequency (hz) gain (db) c l = 0pf r iso = 20 w c l = 22pf c l = 47pf c l = 100pf
MAX477 300mhz high-speed op amp ______________________________________________________________________________________ 11 MAX477 v out v in 20pf 100pf 602 w 110 w 301 w figure 9. 8mhz bessel filter figure 10a. 5mhz square wave input time (50ns/div) voltage (v) gnd gnd in (100mv/div) -0.2v out (200mv/div) 0.2v figure 10b. gain and delay vs. frequency 1m 10m 100m frequency (mhz) gain (db) delay (ns) -8 0 4 -4 38 48 18 8 28 -2 -12 -22 -32 -42 -52 8 10 6 2 -2 -6 -10 delay gain ___________________ chip infor mation transistor count: 175 substrate connected to v ee
MAX477 300mhz high-speed op amp 12 ______________________________________________________________________________________ ________________________________________________________ package infor mation sot5l.eps 8lumaxd.eps

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