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| EL4451C EL4451C Wideband Variable-Gain Amplifier Gain of 2 Features Complete variable-gain amplifier with output amplifier requires no extra components Excellent linearity of 0 2% 70 MHz signal bandwidth Operates on g5V to g15V supplies All inputs are differential 400V ms slew rate l 70dB attenuation 4 MHz General Description The EL4451C is a complete variable gain circuit It offers wide bandwidth and excellent linearity while including a powerful output voltage amplifier drawing modest supply current The EL4451C operates on g5V to g15V supplies and has an analog input range of g2V making it ideal for video signal processing AC characteristics do not change appreciably over the g5V to g15V supply range The circuit has an operational temperature range of b 40 C to a 85 C and is packaged in plastic 14-pin DIP and 14-lead SO The EL4451C is fabricated with Elantec's proprietary complementary bipolar process which provides excellent signal symmetry and is free from latch up Applications Leveling of varying inputs Variable filters Fading Text insertion into video Connection Diagram Outline MDP0031 MDP0027 Ordering Information Part No Temp Range Package EL4451CN b 40 C to a 85 C 14-Pin P-DIP EL4451CS b 40 C to a 85 C 14-Lead SO 4451-1 October 1994 Rev A 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 1994 Elantec Inc EL4451C Wideband Variable-Gain Amplifier Gain of 2 Absolute Maximum Ratings (TA e 25 C) Va VS VIN DVIN IIN Positive Supply Voltage V a to Vb Supply Voltage Voltage at any Input or Feedback Difference between Pairs of Inputs or Feedback Current into any Input or Feedback Pin 16 5V 33V V a to Vb 6V 4mA IOUT PD TA TS Continuous Output Current Maximum Power Dissipation Operating Temperature Range Storage Temperature Range 30mA See Curves b 40 C to a 85 C b 60 C to 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 TJ e TC e TA Test Level I II III IV V Test Procedure 100% production tested and QA sample tested per QA test plan QCX0002 100% production tested at TA e 25 C and QA sample tested at TA e 25 C TMAX and TMIN per QA test plan QCX0002 QA sample tested per QA test plan QCX0002 Parameter is guaranteed (but not tested) by Design and Characterization Data Parameter is typical value at TA e 25 C for information purposes only Open-Loop DC Electrical Characteristics Power Supplies at g5V Parameter VDIFF VCM VOS VOS FB VG 100% VG 0% VG 1V IB IOS NL Ft RIN VIN RIN FB RIN RGAIN Description Signal input differential input voltage - Clipping 0 2% nonlinearity Common-mode range of VIN VDIFF e 0 Vs e g5V Vs e g15V Input offset voltage Output offset voltage Extrapolated voltage for 100% gain Extrapolated voltage for 0% gain Gain at VGAIN e 1V Input bias current (all inputs) Input offset current between VIN a and VINb Gain a and Gainb FB and Ref Nonlinearity VIN between b1V and a 1V VG e 1V Signal feedthrough VG e b1V Input resistance VIN Input resistance FB Input resistance gain input 100 200 50 19 b 0 16 TA e 25 C RL e 500X Max Test Level I V I V 25 25 22 0 06 1 15 0 4 05 b 70 Min 18 g2 0 Typ 20 13 g2 8 g12 8 Units V V V V mV mV V V VV mA mA % dB TD is 3 3in KX KX KX 7 8 21 b 0 06 I I I I I I I I I I V I 0 95 b 20 1 05 b9 02 02 b 100 230 460 100 2 EL4451C Wideband Variable-Gain Amplifier Gain of 2 Open-Loop DC Electrical Characteristics Power Supplies at g5V TA e 25 C RL e 500X Parameter CMRR PSRR VO ISC IS Description Common-mode rejection ratio of VIN Power supply rejection ratio of VOS FB VS e g5V to g15V Output voltage swing VS e g5V (VIN e 0 VREF varied) VS e g15V Output short-circuit current Supply current VS e g15V Min 70 50 g2 5 g12 5 Contd Typ 90 60 g2 8 g12 8 Max Test Level I I I I Units dB dB V mA mA 40 85 15 5 18 I Closed-Loop AC Electrical Characteristics Power supplies at g12V TA e 25 C RL e 500X CL e 15pF VG e 1V Parameter BW b3dB BW g0 1dB Peaking BW gain SR VN dG di Description b 3dB small-signal bandwidth signal input Min Typ 70 10 06 70 400 110 09 02 Max Test Level V V V V V V V V Units MHz MHz dB MHz V ms TD is 1 8in nV 0 1dB flatness bandwidth signal input Frequency response peaking b 3dB small-signal bandwidth gain input Slew rate VOUT between b2V and a 2V RF e RG e 500X Input referred noise voltage density Differential gain error Voffset between b0 7V and a 0 7V Differential phase error Voffset between b0 7V and a 0 7V SHz % Test Circuit 4451 - 3 Note For typical performance curves RF e 0 RG e % VGAIN e 1V RL e 500X and CL e 15 pF unless otherwise noted 3 TD is 1 8in EL4451C Wideband Variable-Gain Amplifier Gain of 2 Typical Performance Curves Frequency Response for Various Feedback Divider Ratios Frequency Response for Various RL CL VS e g5V Frequency Response for Various RL CL VS e g15V 4451 - 4 4451 - 5 4451 - 6 Gain b 3 dB Bandwidth and Peaking vs Load Resistance b 3 dB Bandwidth and Peaking vs Supply Voltage b 3 dB Bandwidth and Peaking vs Die Temperature 4451 - 7 4451 - 8 4451 - 9 Frequency Response for Various Gain Settings Slew Rate vs Supply Voltage Slew Rate vs Die Temperature 4451 - 10 4451 - 11 4451 - 12 4 EL4451C Wideband Variable-Gain Amplifier Gain of 2 Typical Performance Curves Common-Mode Rejection Ratio vs Frequency Contd Input Voltage Noise vs Frequency Nonlinearity vs Input Signal 4451 - 13 4451 - 14 4451 - 15 Differential Gain Error vs Input Offset Voltage VS e g5V or g12V Differential Phase Error vs Input Offset Voltage VS e g5V Differential Phase Error vs Input Offset Voltage VS e g12V 4451 - 16 4451 - 17 4451 - 18 Differential Gain and Phase Errors vs Gain Setting Differential Gain and Phase Errors vs Load Resistance 4451 - 19 4451 - 20 5 EL4451C Wideband Variable-Gain Amplifier Gain of 2 Typical Performance Curves Contd VG 0% and VG 100% vs Supply Voltage Gain vs VGAIN Change in VG 100% and VG 0% vs Die Temperature 4451 - 21 4451 - 22 4451 - 23 Offset Voltage vs Die Temperature Bias Current vs Die Temperature Common Mode Input Range vs Supply Voltage 4451 - 24 4451 - 25 4451 - 26 Supply Current vs Die Temperature Supply Current vs Supply Voltage 14-Pin Package Power Dissipation vs Ambient Temperature 4451 - 27 4451 - 28 4451 - 29 6 EL4451C Wideband Variable-Gain Amplifier Gain of 2 Applications Information The EL4451 is a complete two-quadrant multiplier gain control with 70 MHz bandwidth It has three sets of inputs a differential signal input VIN a differential gain-controlling input VGAIN and another differential input which is used to complete a feedback loop with the output Here is a typical connection 360X or less Alternatively a small capacitor across RF can be used to create more of a frequency-compensated divider The value of the capacitor should scale with the parasitic capacitance at the FB input It is also practical to place small capacitors across both the feedback and the gain resistors (whose values maintain the desired gain) to swamp out parasitics For instance two 10pF capacitors across equal divider resistors for a maximum gain of 4 will dominate parasitic effects and allow a higher divider resistance The REF pin can be used as the output's ground reference for DC offsetting of the output or it can be used to sum in another signal Gain-Control Characteristics The quantity VGAIN in the above equations is bounded as 0 s VGAIN s 2 even though the externally applied voltages exceed this range Actually the gain transfer function around 0 and 2V is ``soft'' that is the gain does not clip abruptly below the 0%-VGAIN voltage nor above the 100%-VGAIN level An overdrive of 0 3V must be applied to VGAIN to obtain truly 0% or 100% Because the 0%- or 100%- VGAIN levels cannot be precisely determined they are extrapolated from two points measured inside the slope of the gain transfer curve Generally an applied VGAIN range of b 0 5V to a 2 5V will assure the full numerical span of 0 s VGAIN s 2 The gain control has a small-signal bandwidth equal to the VIN channel bandwidth and overload recovery resolves in about 20 nsec 4451-2 The gain of the feedback divider is He RG RG a RF The transfer function of the part is VOUT e AO c (((VIN a ) b (VIN b )) c ((VGAIN a ) b (VGAIN b )) a (VREF b VFB)) VFB is connected to VOUT through a feedback network so VFB e H c VOUT AO is the openloop gain of the amplifier and is approximately 600 The large value of AO drives ((VIN a ) b (VIN b )) c ((VGAIN a ) b (VGAIN b )) a (VREF b VFB) x0 Rearranging and substituting for VFB VOUT e (((VIN a ) b (VIN b )) c ((VGAIN a ) b (VGAIN)) a VREF) H or VOUT e (VIN c VGAIN a VREF) H Input Connections The input transistors can be driven from resistive and capacitive sources but are capable of oscillation when presented with an inductive input It takes about 80nH of series inductance to make the inputs actually oscillate equivalent to four inches of unshielded wiring or 6 of unterminated input transmission line The oscillation has a characteristic frequency of 500 MHz Often placing one's finger (via a metal probe) or an oscilloscope probe on the input will kill the oscillation Normal high-frequency construction obviates any such problems where the input source is reasonably close to the input If this is not possible one can insert series resistors of around 51X to de-Q the inputs 7 Thus the output is equal to the difference of the VIN's times the difference of VGAIN'S and offset by VREF all gained up by the feedback divider ratio The EL4451 is stable for a direct connection between VOUT and FB and the divider may be used for higher output gain although with the traditional loss of bandwidth It is important to keep the feedback divider's impedance at the FB terminal low so that stray capacitance does not diminish the loop's phase margin The pole caused by the parallel impedance of the feedback resistors and stray capacitance should be at least 150 MHz typical strays of 3 pF thus require a feedback impedance of EL4451C Wideband Variable-Gain Amplifier Gain of 2 Applications Information Signal Amplitudes Signal input common-mode voltage must be between (V b ) a 3V and (V a ) b 3V to ensure linearity Additionally the differential voltage on any input stage must be limited to g6V to prevent damage The differential signal range is g2V in the EL4451 The input range is substantially constant with temperature Contd For instance the EL4451 draws a maximum of % and the 18mA With light loading RPAR dissipation with g5V supplies is 180 mW The maximum supply voltage that the device can run on for a given PD and other parameters is x VS max e (PD a VO2 RPAR) (2IS a VO RPAR) The maximum dissipation a package can offer is PD max e (TJ max b TA max) iJA The Ground Pin The ground pin draws only 6mA maximum DC current and may be biased anywhere between (V b ) a 2 5V and (V a ) b 3 5V The ground pin is connected to the IC's substrate and frequency compensation components It serves as a shield within the IC and enhances input stage CMRR and feedthrough over frequency and if connected to a potential other than ground it must be bypassed Where TJ max is the maximum die temperature 150 C for reliability less to retain optimum electrical performance TA max is the ambient temperature 70 C for commercial and 85 C for industrial range iJA is the thermal resistance of the mounted package obtained from data sheet dissipation curves Power Supplies The EL4451 works with any supplies from g3V to g15V The supplies may be of different voltages as long as the requirements of the ground pin are observed (see the Ground Pin section) The supplies should be bypassed close to the device with short leads 4 7mF tantalum capacitors are very good and no smaller bypasses need be placed in parallel Capacitors as small as 0 01mF can be used if small load currents flow Single-polarity supplies such as a 12V with a 5V can be used where the ground pin is connected to a 5V and V b to ground The inputs and outputs will have to have their levels shifted above ground to accommodate the lack of negative supply The power dissipation of the EL4451 increases with power supply voltage and this must be compatible with the package chosen This is a close estimate for the dissipation of a circuit PD e 2 c VS c IS max a (VS b VO) c VO RPAR The more difficult case is the SO-14 package With a maximum die temperature of 150 C and a maximum ambient temperature of 85 C the 65 C temperature rise and package thermal resistance of 120 C W gives a dissipation of 542 mW at 85 C This allows the full maximum operating supply voltage unloaded but reduced if loaded Output Loading The output stage of the EL4451 is very powerful It typically can source 80mA and sink 120mA Of course this is too much current to sustain and the part will eventually be destroyed by excessive dissipation or by metal traces on the die opening The metal traces are completely reliable while delivering the 30mA continuous output given in the Absolute Maximum Ratings table in this data sheet or higher purely transient currents Gain changes only 0 2% from no load to 100X load Heavy resistive loading will degrade frequency response and video distortion for loads k 100X Capacitive loads will cause peaking in the frequency response If capacitive loads must be driven a small-valued series resistor can be used to isolate it 12X to 51X should suffice A 22X series resistor will limit peaking to 2 5 dB with even a 220pF load where IS max is the maximum supply current VS is the g supply voltage (assumed equal) VO is the output voltage RPAR is the parallel of all resistors loading the output 8 EL4451C Wideband Variable-Gain Amplifier Gain of 2 Applications Information Leveling Circuits Often a variable-gain control is used to normalize an input signal to a standard amplitude from a modest range of possible input amplitude A good example is in video systems where an unterminated cable will yield a twice-sized standard video amplitude and an erroneously twice-terminated cable gives a 2 3-sized input Here is a g6 dB range preamplifier Linearized Leveling Amplifier 4451 - 31 Contd EL4451 Leveler Circuit Attenuation Ratio e 1 5 EL4451 Leveler Circuit Attenuation Ratio e 2 4451 - 30 In this arrangement the EL4451 outputs a mixture of the signal routed through the multiplier and the REF terminal The multiplier port produces the most distortion and needs to handle a fraction of an oversized video input whereas the REF port is just like an op-amp input summing into the output Thus for oversized inputs the gain will be decreased and the majority of the signal is routed through the linear REF terminal For undersized inputs the gain is increased and the multiplier's contribution added to the output Here are some component values for two designs Attenuation Ratio 15 2 RF RG R1 R2 R3 b 3 dB 4451 - 32 With the higher attenuation ratio the multiplier sees a smaller input amplitude and distorts less however the higher output gain reduces circuit bandwidth As seen in the next curves the peak differential gain error is 0 47% for the attenuation ratio of 1 5 but only 0 27% with the gain of 2 constants To maintain bandwidth an external op amp can be used instead of the RF - RG divider to boost the EL4451's output by the attenuation ratio Sinewave Oscillators Generating a stable low distortion sinewave has long been a difficult task Because a linear oscillator's output tends to grow or diminish continuously either a clipping circuit or automatic gain control (AGC) is needed Clipping circuits generate severe distortion which needs subsequent filtering and AGC's can be complicated 9 Bandwidth 47 MHz 28 MHz 200X 400X 300X 100X 200X 400X 400X 500X 100X 200X EL4451C Wideband Variable-Gain Amplifier Gain of 2 Applications Information Contd Here is the EL4451 used as an oscillator with simple AGC Low-Distortion Sinewave Oscillator 4451 - 33 The oscillation frequency is set by the resonance of a series-tuned circuit which may be an L-C combination or a crystal At resonance the series impedance of the tuned circuit drops and its phase lag is 0 so the EL4451 needs a gain just over unity to sustain oscillation The VGAIN b terminal is initially at b 0 7V and the VGAIN a terminal at about a 2 1V setting the maximum gain in the EL4451 At such high gain the loop oscillates and output amplitude grows until D1 rectifies more positive voltage at VGAIN b ultimately reducing gain until a stable 0 5Vrms output is produced Using a 2 MHz crystal output distortion was b 53 dBc or 0 22% Sideband modulation was only 14 Hz wide at b 90 dBc limited by the filter of the spectrum analyzer used The circuit works up to 30 MHz A parallel-tuned circuit can replace the 510X resistor and the 510X resistor moved in place of the series-tuned element to allow grounding of the tuned components Filters The EL4451 can be connected to act as a voltagevariable integrator as shown EL4451 Connected As Variable Integrator 4451 - 34 The input RC cancels a zero produced by the output op-amp feedback connection at 0 e 1 RC With the input RC connected VOUT VIN e 1 sRC without it VOUT VIN e (1 a sRC) sRC This variable integrator may be used in networks such as the Bi-quad In some applications the input RC may be omitted If a negative gain is required the VIN a and VIN b terminals can be exchanged 10 EL4451C Wideband Variable-Gain Amplifier Gain of 2 Applications Information Contd A voltage-controlled equalizer and cable driver can be constructed so Equalization and Line Driver Amplifier The main signal path is via the REF pin This ensures maximum signal linearity while the multiplier input is used to allow a variable amount of frequency-shaped input from R1 R2 and C For optimum linearity the multiplier input is attenuated by R1 and R2 This may not be necessary depending on input signal amplitude and R1 might be set to 0 R1and R2 should be set to provide sufficient peaking depending on cable highfrequency losses at maximum gain RF and RG are chosen to provide the desired circuit gain including backmatch resistor loss 4451 - 35 11 EL4451C EL4451C Wideband Variable-Gain Amplifier Gain of 2 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 WARNING Life Support Policy October 1994 Rev A 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 12 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 intended 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 replacement of defective components and does not cover injury to persons or property or other consequential damages Printed in U S A |
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