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tm 3-1 HFA1113 850mhz, low distortion, output limiting, programmable gain, buffer ampli?r the HFA1113 is a high speed buffer featuring user programmable gain and output limiting coupled with ultra high speed performance. this buffer is the ideal choice for high frequency applications requiring output limiting, especially those needing ultra fast overload recovery times. the output limiting function allows the designer to set the maximum positive and negative output levels, thereby protecting later stages from damage or input saturation. the sub-nanosecond overdrive recovery time quickly returns the ampli?r to linear operation following an overdrive condition. a unique feature of the pinout allows the user to select a voltage gain of +1, -1, or +2, without the use of any external components, as described in the ?pplication information section. compatibility with existing op amp pinouts provides ?xibility to upgrade low gain ampli?rs, while decreasing component count. unlike most buffers, the standard pinout provides an upgrade path should a higher closed loop gain be needed at a future date. component and composite video systems will also bene? from this buffer s performance, as indicated by the excellent gain ?tness, and 0.02%/0.04 degree differential gain/phase speci?ations (r l = 150 ? ). for military product, refer to the HFA1113/883 data sheet. pinout HFA1113 (soic) top view features user programmable output voltage limiting user programmable for closed-loop gains of +1, -1 or +2 without use of external resistors wide -3db bandwidth. . . . . . . . . . . . . . . . . . . . . . 850mhz excellent gain flatness (to 100mhz). . . . . . . . . . 0.07db low differential gain and phase . . . 0.02%/0.04 degrees low distortion (hd3, 30mhz). . . . . . . . . . . . . . . . . -73dbc very fast slew rate . . . . . . . . . . . . . . . . . . . . . 2400v/ s fast settling time (0.1%) . . . . . . . . . . . . . . . . . . . . . 13ns high output current . . . . . . . . . . . . . . . . . . . . . . . . . 60ma excellent gain accuracy . . . . . . . . . . . . . . . . . . . 0.99v/v overdrive recovery . . . . . . . . . . . . . . . . . . . . . . . . . <1ns standard operational ampli?r pinout applications rf/if processors driving flash a/d converters high-speed communications impedance transformation line driving video switching and routing radar systems medical imaging systems ordering information part number (brand) temp. range ( o c) package pkg. no. HFA1113ib (h1113i) -40 to 85 8 ld soic m8.15 hfa11xxeval dip ev aluation board for high speed op amps nc -in +in v- 1 2 3 4 8 7 6 5 v h v+ out v l + 300 300 - pin descriptions name pin number description nc 1 no connection -in 2 inverting input +in 3 non-inverting input v- 4 negative supply v l 5 lower output limit out 6 output v+ 7 positive supply v h 8 upper output limit data sheet february 1999 file number 1342.5 caution: these devices are sensitive to electrostatic discharge; follow proper ic handling procedures. 1-888-intersil or 321-724-7143 | intersil and design is a trademark of intersil corporation. | copyright intersil corporation 2000
3-2 absolute maximum ratings thermal information voltage between v+ and v- . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12v dc input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v supply voltage at v h or v l terminal . . . . . . . . . . . . . . (v+) + 2v to (v-) - 2v output current (50% duty cycle) . . . . . . . . . . . . . . . . . . . . . . 60ma operating conditions temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . -40 o c to 85 o c thermal resistance (typical, note 1) ja ( o c/w) soic package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 maximum junction temperature (plastic package) . . . . . . . .150 o c maximum storage temperature range . . . . . . . . . . -65 o c to 150 o c maximum lead temperature (soldering 10s) . . . . . . . . . . . . 300 o c (soic - lead tips only) caution: stresses above those listed in ?bsolute maximum ratings may cause permanent damage to the device. this is a stress only rating and operatio n of the device at these or any other conditions above those indicated in the operational sections of this speci?ation is not implied. note: 1. ja is measured with the component mounted on an evaluation pc board in free air. electrical speci?ations v supply = 5v, a v = +1, r l = 100 ? , unless otherwise speci?d parameter test conditions temp. ( o c) min typ max units input characteristics output offset voltage 25 - 8 25 mv full - - 35 mv output offset voltage drift full - 10 - v/ o c psrr 25 39 45 - db full 35 - - db input noise voltage (note 3) 100khz 25 - 9 - nv/ hz +input noise current (note 3) 100khz 25 - 37 - pa/ hz non-inverting input bias current 25 - 25 40 a full - - 65 a non-inverting input resistance 25 25 50 - k ? inverting input resistance (note 2) 25 240 300 360 ? input capacitance 25 - 2 - pf input common mode range full 2.5 2.8 - v transfer characteristics gain a v = +1, v in = +2v 25 0.980 0.990 1.020 v/v full 0.975 - 1.025 v/v a v = +2, v in = +1v 25 1.96 1.98 2.04 v/v full 1.95 - 2.05 v/v dc non-linearity (note 3) a v = +2, 2v full scale 25 - 0.02 - % output characteristics output voltage (note 3) a v = -1 25 3.0 3.3 - v full 2.5 3.0 - v output current (note 3) r l = 50 ? 25, 85 50 60 - ma -40 35 50 - ma closed loop output impedance dc, a v = +2 25 - 0.3 - ? power supply characteristics supply voltage range full 4.5 - 5.5 v supply current (note 3) 25 - 21 26 ma full - - 33 ma HFA1113 3-3 ac characteristics -3db bandwidth (v out = 0.2v p-p , notes 2, 3) a v = -1 25 450 800 - mhz a v = +1 25 500 850 - mhz a v = +2 25 350 550 - mhz slew rate (v out = 5v p-p , note 2) a v = -1 25 1500 2400 - v/ s a v = +1 25 800 1500 - v/ s a v = +2 25 1100 1900 - v/ s full power bandwidth (v out = 5v p-p , note 3) a v = -1 25 - 300 - mhz a v = +1 25 - 150 - mhz a v = +2 25 - 220 - mhz gain flatness (to 30mhz, notes 2, 3) a v = -1 25 - 0.02 - db a v = +1 25 - 0.1 - db a v = +2 25 - 0.015 0.04 db gain flatness (to 50mhz, notes 2, 3) a v = -1 25 - 0.05 - db a v = +1 25 - 0.2 - db a v = +2 25 - 0.036 0.08 db gain flatness (to 100mhz, notes 2, 3) a v = -1 25 - 0.10 - db a v = +2 25 - 0.07 0.22 db linear phase deviation (to 100mhz, note 3) a v = -1 25 - 0.13 - degrees a v = +1 25 - 0.83 - degrees a v = +2 25 - 0.05 - degrees 2nd harmonic distortion (30mhz, v out = 2v p-p , notes 2, 3) a v = -1 25 - -52 - dbc a v = +1 25 - -57 - dbc a v = +2 25 - -52 -45 dbc 3rd harmonic distortion (30mhz, v out = 2v p-p , notes 2, 3) a v = -1 25 - -71 - dbc a v = +1 25 - -73 - dbc a v = +2 25 - -72 -65 dbc 2nd harmonic distortion (50mhz, v out = 2v p-p , notes 2, 3) a v = -1 25 - -47 - dbc a v = +1 25 - -53 - dbc a v = +2 25 - -47 -40 dbc 3rd harmonic distortion (50mhz, v out = 2v p-p , notes 2, 3) a v = -1 25 - -63 - dbc a v = +1 25 - -68 - dbc a v = +2 25 - -65 -55 dbc 2nd harmonic distortion (100mhz, v out = 2v p-p , notes 2, 3) a v = -1 25 - -41 - dbc a v = +1 25 - -50 - dbc a v = +2 25 - -42 -35 dbc 3rd harmonic distortion (100mhz, v out = 2v p-p , notes 2, 3) a v = -1 25 - -55 - dbc a v = +1 25 - -49 - dbc a v = +2 25 - -62 -45 dbc electrical speci?ations v supply = 5v, a v = +1, r l = 100 ? , unless otherwise speci?d (continued) parameter test conditions temp. ( o c) min typ max units HFA1113 3-4 3rd order intercept (a v = +2, note 3) 100mhz 25 - 28 - dbm 300mhz 25 - 13 - dbm 1db compression (a v = +2, note 3) 100mhz 25 - 19 - dbm 300mhz 25 - 12 - dbm reverse isolation (s 12 , note 3) 40mhz 25 - -70 - db 100mhz 25 - -60 - db 600mhz 25 - -32 - db transient characteristics rise time (v out = 0.5v step, note 2) a v = -1 25 - 500 800 ps a v = +1 25 - 480 750 ps a v = +2 25 - 700 1000 ps rise time (v out = 2v step) a v = -1 25 - 0.82 - ns a v = +1 25 - 1.06 - ns a v = +2 25 - 1.00 - ns overshoot (v out = 0.5v step, input t r /t f = 200ps, notes 2, 3, 4) a v = -1 25 - 12 30 % a v = +1 25 - 45 65 % a v = +2 25 - 6 20 % 0.1% settling time (note 3) v out = 2v to 0v 25 - 13 20 ns 0.05% settling time v out = 2v to 0v 25 - 20 33 ns differential gain a v = +1, 3.58mhz, r l = 150 ? 25 - 0.03 - % a v = +2, 3.58mhz, r l = 150 ? 25 - 0.02 - % differential phase a v = +1, 3.58mhz, r l = 150 ? 25 - 0.05 - degrees a v = +2, 3.58mhz, r l = 150 ? 25 - 0.04 - degrees output limiting characteristics a v = +2, v h = +1v, v l = -1v, unless otherwise speci?d clamp accuracy (note 3) v in = 1.6v, a v = -1 25 - 100 150 mv full - - 200 mv clamp overshoot v in = 1v, input t r /t f = 500ps 25 - 7 - % overdrive recovery time (note 3) v in = 1v 25 - 0.75 1.5 ns negative clamp range 25 - -5.0 to +2.0 -v positive clamp range 25 - -2.0 to +5.0 -v clamp input bias current (note 3) 25 - 50 200 a full - - 300 a clamp input bandwidth (note 3) v h or v l = 100mv p-p 25 - 500 - mhz notes: 2. this parameter is not tested. the limits are guaranteed based on lab characterization, and reflect lot-to-lot variation. 3. see typical performance curves for more information. 4. overshoot decreases as input transition times increase, especially for a v = +1. please refer to typical performance curves. electrical speci?ations v supply = 5v, a v = +1, r l = 100 ? , unless otherwise speci?d (continued) parameter test conditions temp. ( o c) min typ max units HFA1113 3-5 application information closed loop gain selection the HFA1113 features a novel design which allows the user to select from three closed loop gains, without any external components. the result is a more ?xible product, fewer part types in inventory, and more ef?ient use of board space. this ?uffer?operates in closed loop gains of -1, +1, or +2, and gain selection is accomplished via connections to the inputs. applying the input signal to +in and floating -in selects a gain of +1, while grounding -in selects a gain of +2. a gain of -1 is obtained by applying the input signal to -in with +in grounded. the table below summarizes these connections: pc board layout the frequency response of this ampli?r depends greatly on the amount of care taken in designing the pc board. the use of low inductance components such as chip resistors and chip capacitors is strongly recommended, while a solid ground plane is a must! attention should be given to decoupling the power supplies. a large value (10 f) tantalum in parallel with a small value chip (0.1 f) capacitor works well in most cases. terminated microstrip signal lines are recommended at the input and output of the device. capacitance directly on the output must be minimized, or isolated as discussed in the next section. for unity gain applications, care must also be taken to minimize the capacitance to ground seen by the ampli?r s inverting input. at higher frequencies this capacitance will tend to short the -input to gnd, resulting in a closed loop gain which increases with frequency. this will cause excessive high frequency peaking and potentially other problems as well. an example of a good high frequency layout is the evaluation board shown in figure 3. driving capacitive loads capacitive loads, such as an a/d input, or an improperly terminated transmission line will degrade the ampli?r s phase margin resulting in frequency response peaking and possible oscillations. in most cases, the oscillation can be avoided by placing a resistor (r s ) in series with the output prior to the capacitance. figure 1 details starting points for the selection of this resistor. the points on the curve indicate the r s and c l combinations for the optimum bandwidth, stability, and settling time, but experimental ?e tuning is recommended. picking a point above or to the right of the curve yields an overdamped response, while points below or left of the curve indicate areas of underdamped performance. r s and c l form a low pass network at the output, thus limiting system bandwidth well below the ampli?r bandwidth of 850mhz. by decreasing r s as c l increases (as illustrated in the curves), the maximum bandwidth is obtained without sacri?ing stability. even so, bandwidth does decrease as you move to the right along the curve. for example, at a v = +1, r s = 50 ? , c l = 30pf, the overall bandwidth is limited to 300mhz, and bandwidth drops to 100mhz at a v = +1, r s = 5 ? , c l = 340pf. evaluation board the performance of the HFA1113 may be evaluated using the hfa11xx evaluation board, slightly modi?d as follows: 1. remove the 500 ? feedback resistor (r 2 ), and leave the connection open. 2. a. for a v = +1 evaluation, remove the 500 ? gain setting resistor (r 1 ), and leave pin 2 ?ating. b. for a v = +2, replace the 500 ? gain setting resistor with a 0 ? resistor to gnd. the modi?d schematic and layout of the board are shown in figures 2 and 3. to order evaluation boards (part number hfa11xxeval), please contact your local sales of?e. note: the soic version may be evaluated in the dip board by using a soic-to-dip adapter such as aries electronics part number 08-350000-10. gain (a cl ) connections +input (pin 3) -input (pin 2) -1 gnd input +1 input nc (floating) +2 input gnd r s ( ? ) load capacitance (pf) 50 45 40 35 30 25 20 15 10 5 0 0 40 80 120 160 200 240 280 320 360 400 a v = +1 a v = +2 figure 1. recommended series resistor vs load capacitance HFA1113 3-6 . limiting operation general the HFA1113 features user programmable output clamps to limit output voltage excursions. clamping action is obtained by applying voltages to the v h and v l terminals (pins 8 and 5) of the ampli?r. v h sets the upper output limit, while v l sets the lower clamp level. if the ampli?r tries to drive the output above v h , or below v l , the clamp circuitry limits the output voltage at v h or v l ( the clamp accuracy), respectively. the low input bias currents of the clamp pins allow them to be driven by simple resistive divider circuits, or active elements such as ampli?rs or dacs. clamp circuitry figure 4 shows a simpli?d schematic of the HFA1113 input stage, and the high clamp (v h ) circuitry. as with all current feedback ampli?rs, there is a unity gain buffer (q x1 - q x2 ) between the positive and negative inputs. this buffer forces -in to track +in, and sets up a slewing current of: (v -in - v out )/r f + v -in /r g this current is mirrored onto the high impedance node (z) by q x3 -q x4 , where it is converted to a voltage and fed to the output via another unity gain buffer. if no clamping is utilized, the high impedance node may swing within the limits de?ed by q p4 and q n4 . note that when the output reaches its quiescent value, the current ?wing through -in is reduced to only that small current (-i bias ) required to keep the output at the ?al voltage. tracing the path from v h to z illustrates the effect of the clamp voltage on the high impedance node. v h decreases by 2v be (q n6 and q p6 ) to set up the base voltage on q p5 . q p5 begins to conduct whenever the high impedance node reaches a voltage equal to q p5 s base voltage + 2v be (q p5 and q n5 ). thus, q p5 clamps node z whenever z reaches v h . r 1 provides a pull-up network to ensure functionality with the clamp inputs ?ating. a similar description applies to the symmetrical low clamp circuitry controlled by v l . when the output is clamped, the negative input continues to source a slewing current (i clamp ) in an attempt to force the output to the quiescent voltage de?ed by the input. q p5 must sink this current while clamping, because the -in current is always mirrored onto the high impedance node. the clamping current is calculated as: i clamp = (v -in - v out clamped )/300 ? + v -in /r g . as an example, a unity gain circuit with v in = 2v, and v h =1v, would have i clamp = (2v - 1v)/300 ? + 2v/ = 3.33ma (r g = because -in is floated for unity gain applications). note that i cc will increase by i clamp when the output is clamp limited. 1 2 3 4 8 7 6 5 +5v 10 f 0.1 f v h 50 ? gnd gnd r 1 -5v 0.1 f 0 f 50 ? in out v l (a v = +1) or 0 ? (a v = +2) figure 2. modified evaluation board schematic v h +in v l v+ gnd 1 v- out top layout bottom layout figure 3. evaluation board layout +1 +in v- v+ q p1 q n1 v- q n3 q p3 q p4 q n2 q p2 q n4 q p5 q n5 z v+ -in v out i clamp r f = 300 ? (internal) q p6 q n6 v h r 1 50k (30k for v l ) 300 ? r g (internal) v -in 200 ? figure 4. HFA1113 simplified v h clamp circuitry HFA1113 3-7 clamp accuracy the clamped output voltage will not be exactly equal to the voltage applied to v h or v l . offset errors, mostly due to v be mismatches, necessitate a clamp accuracy parameter which is found in the device speci?ations. clamp accuracy is a function of the clamping conditions. referring again to figure 4, it can be seen that one component of clamp accuracy is the vbe mismatch between the q x6 transistors, and the q x5 transistors. if the transistors always ran at the same current level there would be no v be mismatch, and no contribution to the inaccuracy. the q x6 transistors are biased at a constant current, but as described earlier, the current through q x5 is equivalent to i clamp . v be increases as i clamp increases, causing the clamped output voltage to increase as well. i clamp is a function of the overdrive level (a vcl x v in - v out clamped ), so clamp accuracy degrades as the overdrive increases. as an example, the speci?d accuracy of 100mv (a v = -1, v h = 1v) for a 1.6x overdrive degrades to 240mv for a 3x (200%) overdrive, as shown in figure 43. consideration must also be given to the fact that the clamp voltages have an affect on ampli?r linearity. the ?onlinearity near clamp voltage?curve, figure 48, illustrates the impact of several clamp levels on linearity. clamp range unlike some competitor devices, both v h and v l have usable ranges that cross 0v. while v h must be more positive than v l , both may be positive or negative, within the range restrictions indicated in the speci?ations. for example, the HFA1113 could be limited to ecl output levels by setting v h = -0.8v and v l = -1.8v. v h and v l may be connected to the same voltage (gnd for instance) but the result won? be in a dc output voltage from an ac input signal. a 150mv - 200mv ac signal will still be present at the output. recovery from overdrive the output voltage remains at the clamp level as long as the overdrive condition remains. when the input voltage drops below the overdrive level (v clamp /a vcl ) the ampli?r will return to linear operation. a time delay, known as the overdrive recovery time, is required for this resumption of linear operation. the plots of ?nclamped performance and ?lamped performance?(figures 41 and 42) highlight the HFA1113 |