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EL2020C
EL2020C
50 MHz Current Feedback Amplifier
Features
Slew rate 500 V ms g33 mA output current Drives g2 4V into 75X Differential phase k 0 1 Differential gain k 0 1% V supply g5V to g18V Output short circuit protected Uses current mode feedback 1% settling time of 50 ns for 10V step Low cost 9 mA supply current 8-pin mini-dip
General Description
The EL2020 is a fast settling wide bandwidth amplifier optimized for gains between b 10 and a 10 Built using the Elantec monolithic Complementary Bipolar process this amplifier uses current mode feedback to achieve more bandwidth at a given gain then a conventional voltage feedback operational amplifier The EL2020 will drive two double terminated 75X coax cables to video levels with low distortion Since it is a closed loop device the EL2020 provides better gain accuracy and lower distortion than an open loop buffer The device includes output short circuit protection and input offset adjust capability The bandwidth and slew rate of the EL2020 are relatively independent of the closed loop gain taken The 50 MHz bandwidth at unity gain only reduces to 30 MHz at a gain of 10 The EL2020 may be used in most applications where a conventional op amp is used with a big improvement in speed power product Elantec products and facilities comply with Elantec document QRA-1 Processing-Monolithic Products
Applications
Video gain block Residue amplifier Radar systems Current to voltage converter Coax cable driver with gain of 2
Connection Diagrams
SOL
Ordering Information
Part No EL2020CN EL2020CM Temp Range Pkg Outline
b 40 C to a 85 C P-DIP MDP0031 b 40 C to a 85 C 20-Lead MDP0027
SOL
2020 - 2
DIP
December 1995 Rev G
2020 - 1
Manufactured under U S Patent No 4 893 091
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
1989 Elantec Inc
EL2020C
50 MHz Current Feedback Amplifier
Absolute Maximum Ratings (25 C)
VS VIN DVIN IIN IINS PD IOP Supply Voltage Input Voltage Differential Input Voltage Input Current (Pins 2 or 3) Input Current (Pins 1 5 or 8) Maximum Power Dissipation (See Curves) Peak Output Current Output Short Circuit Duration (Note 2)
g18V or 36V g15V or VS g10V g10 mA g5 mA
TA TJ TST
Operating Temperature Range Operating Junction Temperature Plastic Package SOL Storage Temperature
b 40 C to a 85 C
150 C
b 65 C to a 150 C
1 25W Short Circuit Protected Continuous
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 Characteristics VS e g15V
Parameter VOS (Note 1) Description Input Offset Voltage Temp Min 25 C TMIN TMAX DVOS DT CMRR (Note 3) PSRR (Note 4) Offset Voltage Drift Common Mode Rejection Ratio Power Supply Rejection Ratio ALL 25 C TMIN TMAX
a IIN b 10 b 15 b 30
Limits Typ 3 Max
a 10 a 15
Test Level I III V II I III
Units mV mV mV C dB dB dB mA mA MX mA V TD is 2 8in mA V mA mA
50 65 60
b 15 b 25
60 75
Non-inverting Input Current
25 C TMAX TMIN
5
a 15 a 25
II III II
a RIN a IPSR (Note 4)
Non-Inverting Input Resistance Non-Inverting Input Current Power Supply Rejection
b Input Current
ALL 25 C TMAX TMIN 25 C TMAX TMIN
1
5 0 05 05 10
II III II III
b IIN (Note 1)
b 40 b 50
10
a 40 a 50
2
EL2020C
50 MHz Current Feedback Amplifier
Open Loop Characteristics VS e g15V
Parameter
b ICMR (Note 3)
Contd
Temp Min 25 C TMAX TMIN 25 C TMAX TMIN 25 C TMAX TMIN 25 C TMAX TMIN 25 C TMAX TMIN 25 C TMAX TMIN 25 C TMAX TMIN 25 C TMIN TMAX 300 50 70 60 60 55
g12 g11 g30 g27 5 g32 5 g13
Description
b Input Current Common Mode Rejection b Input Current Power Supply Rejection
Limits Typ 05 Max 20 40 0 05 05 10 1000
Test Level II III II III II III
Units mA V mA V mA V mA V V mA V mA dB dB dB dB V V mA mA mA mA mA TD is 4 1in mA mA mA
b IPSR (Note 4)
Rol
Transimpedence (DVOUT D(bIIN)) RL e 400X VOUT e g10V Open Loop DC Voltage Gain RL e 400X VOUT e g10V Open Loop DC Voltage Gain RL e 100X VOUT e g2 5V Output Voltage Swing RL e 400X Output Current RL e 400X Quiescent Supply Current
AVOL1
80
II III
AVOL2
70
II III II III II III
VO
IOUT
Is
9
12 15
I III II II II II
Is off Ilogic ID Ie
Supply Current Disabled V8 e 0V Pin 8 Current Pin 8 e 0V Min Pin 8 Current to Disable Max Pin 8 Current to Enable
ALL ALL ALL ALL
55 11 120
75 15 250 30
3
EL2020C
50 MHz Current Feedback Amplifier
AC Closed Loop Characteristics EL2020C VS e g15V
Parameter Description Closed Loop Gain of 1 V V (0 dB) RF e 1 kX Slew Rate Rl e 400X VO e g10V test at VO e g5V Full Power Bandwidth (Note 5) Rise Time Rl e 100X VOUT e 1V 10% to 90% Fall Time Rl e 100X VOUT e 1V 10% to 90% Propagation Delay Rl e 100X VOUT e 1V 50% Points Closed Loop Gain of 1 V V (0 dB) RF e 820X b 3 dB Small Signal Bandwidth Rl e 100X VO e 100 mV 1% Settling Time Rl e 400X VO e 10V 0 1% Settling Time Rl e 400X VO e 10V Closed Loop Gain of 10 V V (20 dB) RF e 1 kX RG e 111X Slew Rate Rl e 400X VO e g10V Test at VO e g5V Full Power Bandwidth (Note 5) Rise Time Rl e 100X VOUT e 1V 10% to 90% Fall Time Rl e 100X VOUT e 1V 10% to 90% Propagation Delay Rl e 100X VOUT e 1V 50% points Closed Loop Gain of 10 V V (20 dB) RF e 680X RG e 76X b 3 dB Small Signal Bandwidth Rl e 100X VO e 100 mV 1% Settling Time Rl e 400 X VO e 10V 0 1% Settling Time Rl e 400X VO e 10V 300 4 77 Min TA e 25 C Typ Max Test Level I I V V V V V V I I V V V V V V Units
SR1 FPBW1 tr1 tf1 tp1 BW ts ts SR10 FPBW10 tr10 tf10 tp10 BW ts ts
300 4 77
500 7 95 6 6 8 50 50 90 500 7 95 25 25 12 30 55 280
V ms MHz ns ns ns MHz ns ns V ms MHz ns ns ns MHz ns ns TD is 3 2in
Note 1 The offset voltage and inverting input current can be adjusted with an external 10 kX pot between pins 1 and 5 with the wiper connected to VCC (Pin 7) to make the output offset voltage zero Note 2 A heat sink is required to keep the junction temperature below the absolute maximum when the output is short circuited Note 3 VCM e g10V Note 4 g4 5V s VS s g18V Note 5 Full Power Bandwidth is guaranteed based on Slew Rate measurement FPBW e SR 2qVpeak
4
EL2020C
50 MHz Current Feedback Amplifier
Typical Performance Curves Non-Inverting Gain of One
AVCL e a 1 Gain vs Frequency Phase Shift vs Frequency
Settling Time vs Output Swing
b 3 dB Bandwidth vs Supply Voltage
Rise Time and Prop Delay vs Temperature
Slew Rate vs Supply Voltage
Slew Rate vs Temperature
2020 - 4
5
EL2020C
50 MHz Current Feedback Amplifier
Typical Performance Curves
AVCL e b 1
Contd
Inverting Gain of One
Phase Shift vs Frequency
Gain vs Frequency
Settling Time vs Output Swing
b 3 dB Bandwidth vs Supply Voltage
Rise Time and Prop Delay vs Temperature
Slew Rate vs Supply Voltage
Slew Rate vs Temperature
2020 - 5
6
EL2020C
50 MHz Current Feedback Amplifier
Typical Performance Curves
AVCL e a 2
Contd
Non-Inverting Gain of Two
Phase Shift vs Frequency
Gain vs Frequency
Settling Time vs Output Swing
b 3 dB Bandwidth vs
Supply Voltage
Rise Time and Prop Delay vs Temperature
Slew Rate vs Supply Voltage
Slew Rate vs Temperature
2020 - 6
7
EL2020C
50 MHz Current Feedback Amplifier
Typical Performance Curves
AVCL e a 10
Contd
Non-Inverting Gain of Ten
Phase Shift vs Frequency
Gain vs Frequency
Settling Time vs Output Swing
b 3 dB Bandwidth vs Supply Voltage
Rise Time and Prop Delay vs Temperature
Slew Rate vs Supply Voltage
Slew Rate vs Temperature
2020 - 7
8
EL2020C
50 MHz Current Feedback Amplifier
Typical Performance Curves
Maximum Undistorted Output Voltage vs Frequency
Contd
Input Resistance vs Temperature
PSRR vs Frequency
Voltage Noise vs Frequency
Current Noise vs Frequency
Output Impedance vs Frequency
Supply Current vs Supply Voltage
8-Lead Plastic DIP Maximum Power Dissipation vs Ambient Temperature
20-Lead SOL Maximum Power Dissipation vs Ambient Temperature
2020 - 8
9
EL2020C
50 MHz Current Feedback Amplifier
Application Information
Theory of Operation
The EL2020 has a unity gain buffer similar to the EL2003 from the non-inverting input to the inverting input The error signal of the EL2020 is a current flowing into (or out of) the inverting input A very small change in current flowing through the inverting input will cause a large change in the output voltage This current amplification is the transresistance (ROL) of the EL2020 VOUT e ROL IINV Since ROL is very large ( 106) the current flowing into the inverting input in the steady state (non-slewing) condition is very small Therefore we can still use op-amp assumptions as a first order approximation for circuit analysis namely that 1 The voltage across the inputs 0 and 2 The current into the inputs is 0
Simplified Block Diagram of EL2020
in a lower b 3 dB frequency Attenuation at high frequency is limited by a zero in the closed loop transfer function which results from stray capacitance between the inverting input and ground
Power Supplies
The EL2020 may be operated with single or split power supplies as low as g3V (6V total) to as high as g18V (36V total) The slew rate degrades significantly for supply voltages less than g5V (10V total) but the bandwidth only changes 25% for supplies from g3V to g18V It is not necessary to use equal value split power supplies i e b 5V and a 12V would be excellent for 0V to 1V video signals Bypass capacitors from each supply pin to a ground plane are recommended The EL2020 will not oscillate even with minimal bypassing however the supply will ring excessively with inadequate capacitance To eliminate supply ringing and the errors it might cause a 4 7 mF tantalum capacitor with short leads is recommended for both supplies Inadequate supply bypassing can also result in lower slew rate and longer settling times
Non-Inverting Amplifier
2020 - 10
Resistor Value Selection and Optimization
The value of the feedback resistor (and an internal capacitor) sets the AC dynamics of the EL2020 A nominal value for the feedback resistor is 1 kX which is the value used for production testing This value guarantees stability For a given gain the bandwidth may be increased by decreasing the feedback resistor and conversely the bandwidth will be decreased by increasing the feedback resistor Reducing the feedback resistor too much will result in overshoot and ringing and eventually oscillations Increasing the feedback resistor results
EL2020 Typical Non-Inverting Amplifier Characteristics
AV RF RG Bandwidth
2020 - 11
10V Settling Time 1% 0 1% 90 ns 100 ns 200 ns 280 ns
a1 a2 a5 a 10
820X 750X 680X 680X
None 750X 170X 76X
50 MHz 50 MHz 50 MHz 30 MHz
50 ns 50 ns 50 ns 55 ns
10
EL2020C
50 MHz Current Feedback Amplifier
Application Information
Summing Amplifier
Contd
pling Inductive sources may cause oscillations a 1 kX resistor in series with the input lead will usually eliminate problems without sacrificing too much speed
Current Limit
The EL2020 has internal current limits that protect the output transistors The current limit goes down with junction temperature rise At a junction temperature of a 175 C the current limits are at about 50 mA If the EL2020 output is shorted to ground when operating on g15V supplies the power dissipation could be as great as 1 1W A heat sink is required in order for the EL2020 to survive an indefinite short Recovery time to come out of current limit is about 50 ns
2020 - 12
EL2020 Typical Inverting Amplifier Characteristics
AV RF R1 R2 Bandwidth 10V Settling Time 1%
b1 b2 b5 b 10
0 1% 130 ns 160 ns 160 ns 170 ns
Using the 2020 with Output Buffers
When more output current is required a wideband buffer amplifier can be included in the feedback loop of the EL2020 With the EL2003 the subsystem overshoots about 10% due to the phase lag of the EL2003 With the EL2004 in the loop the overshoot is less than 2% For even more output current several buffers can be paralleled
EL2020 Buffered with an EL2004
750X 750X 680X 680X
750X 375X 130X 68X
40 MHz 40 MHz 40 MHz 30 MHz
50 ns 55 ns 55 ns 70 ns
Input Range
The non-inverting input to the EL2020 looks like a high resistance in parallel with a few picofarads in addition to a DC bias current The input characteristics change very little with output loading even when the amplifier is in current limit The input charactersitics also change when the input voltage exceeds either supply by 0 5V This happens because the input transistor's base-collector junctions forward bias If the input exceeds the supply by LESS than 0 5V and then returns to the normal input range the output will recover in less than 10 ns However if the input exceeds the supply by MORE than 0 5V the recovery time can be 100's of nanoseconds For this reason it is recommended that Schottky diode clamps from input to supply be used if a fast recovery from large input overloads is required
2020 - 13
Capacitive Loads
The EL2020 is like most high speed feedback amplifiers in that it does not like capacitive loads between 50 pF and 1000 pF The output resistance works with the capacitive load to form a second non-dominate pole in the loop This results in excessive peaking and overshoot and can lead to oscillations Standard resistive isolation techniques used with other op amps work well to isolate capacitive loads from the EL2020
Source Impedance
The EL2020 is fairly tolerant of variations in source impedances Capacitive sources cause no problems at all resistive sources up to 100 kX present no problems as long as care is used in board layout to minimize output to input cou-
11
EL2020C
50 MHz Current Feedback Amplifier
Application Information
Offset Adjust
To calculate the amplifier system offset voltage from input to output we use the equation Output Offset Voltage e VOS (RF RG a 1) g IBIAS (RF) The EL2020 output offset can be nulled by using a 10 kX potentiometer from pins 1 to 5 with the slider tied to pin 7 ( a VCC) This adjusts both the offset voltage and the inverting input bias current The typical adjustment range is g80 mV at the output Contd
Driving Cables
The EL2020 was designed with driving coaxial cables in mind With 30 mA of output drive and low output impedance driving one to three 75X double terminated coax cables with one EL2020 is practical Since it is easy to set up a gain of a 2 the double matched method is the best way to drive coax cables because the impedance match on both ends of the cable will suppress reflections For a discussion on some of the other ways to drive cables see the section on driving cables in the EL2003 data sheet
Video Performance Characteristics
The EL2020 makes an excellent gain block for video systems both RS-170 (NTSC) and faster It is capable of driving 3 double terminated 75X cables with distortion levels acceptable to broadcasters A common video application is to drive a 75X double terminated coax with a gain of 2 To measure the video performance of the EL2020 in the non-inverting gain of 2 configuration 5 identical gain-of-two circuits were cascaded (with a divide by two 75X attenuator between each stage) to increase the errors The results shown in the photos indicate the entire system of 5 gain-of-two stages has a differential gain of 0 5% and a differential phase of 0 5 This implies each device has a differential gain phase of 0 1% and 0 1 but these are too small to measure on single devices
Differential Phase of 5 Cascaded Gain-Of-Two Stages Differential Gain of 5 Cascaded Gain-Of-Two Stages
Compensation
The EL2020 is internally compensated to work with external feedback resistors for optimum bandwidth over a wide range of closed loop gain The part is designed for a nominal 1 kX of feedback resistance although it is possible to get more bandwidth by decreasing the feedback resistance The EL2020 becomes less stable by adding capacitance in parallel with the feedback resistor so feedback capacitance is not recommended The EL2020 is also sensitive to stray capacitance from the inverting input to ground so the board should be laid out to keep the physical size of this node small with ground plane kept away from this node
Active Filters
The EL2020's low phase lag at high frequencies makes it an excellent choice for high performance active filters The filter response more closely approaches the theoritical response than with conventional op amps due to the EL2020's smaller propagation delay Because the internal compensation of the EL2020 depends on resistive feedback the EL2020 should be set up as a gain block
2020 - 14
12
EL2020C
50 MHz Current Feedback Amplifier
Application Information
Video Distribution Amplifier
The distribution amplifier shown below features a difference input to reject common mode signals on the 75X coax cable input Common mode rejection is often necessary to help to eliminate 60 Hz noise found in production environments
Video Distribution Amplifier with Difference Input
Contd
Using the EL2020 as a Multiplexer
An interesting use of the enable feature is to combine several amplifiers in parallel with their outputs common This combination then acts similar to a MUX in front of an amplifier A typical circuit is shown When the EL2020 is disabled the DC output impedance is very high over 10 kX However there is also an output capacitance that is non-linear For signals of less than 5V peak to peak the output capacitance looks like a simple 15 pF capacitor However for larger signals the output capacitance becomes much larger and non-linear The example multiplexer will switch between amplifiers in 5 ms for signals of less than g2V on the outputs For full output signals of 20V peak to peak the selection time becomes 25 ms The disabled outputs also present a capacitive load and therefore only three amplifiers can have their outputs shorted together However an unlimited number can sum together if a small resistor (25X) is inserted in series with each output to isolate it from the ``bus'' There will be a small gain loss due to the resistors of course
Using the EL2020 as a Multiplexer
2020 - 15
EL2020 Disable Enable Operation
The EL2020 has an enable disable control input at pin 8 The device is enabled and operates normally when pin 8 is left open or returned to pin 7 VCC When more than 250 mA is pulled from pin 8 the EL2020 is disabled The output becomes a high impedance the inverting input is no longer driven to the positive input voltage and the supply current is halved To make it easy to use this feature there is an internal resistor to limit the current to a safe level ( E 1 1 mA) if pin 8 is grounded To draw current out of pin 8 an ``open collector output'' logic gate or a discrete NPN transistor can be used This logic interface method has the advantage of level shifting the logic signal from 5V supplies to whatever supply the EL2020 is operating on without any additional components
2020 - 16
13
EL2020C
50 MHz Current Feedback Amplifier
Burn-In Circuit
2020 - 17
Pin numbers are for DIP Packages All Packages Use the Same Schematic
Equivalent Circuit
2020 - 18
14
EL2020C
50 MHz Current Feedback Amplifier
EL2020 Macromodel
Revision A March 1992 Enhancements include PSRR CMRR and Slew Rate Limiting a input Connections b input l a Vsupply l l b Vsupply l l l output l l l l
TAB WIDE
l
subckt M2020 Input Stage e1 10 0 3 0 1 0 vis 10 9 0V h2 9 12 vxx 1 0 r1 2 11 50 l1 11 12 29nH iinp 3 0 10mA iinm 2 0 5mA Slew Rate Limiting h1 13 0 vis 600 r2 13 14 1K d1 14 0 dclamp d2 0 14 dclamp High Frequency Pole 3
l
2
l
7
l
4
l
6
e2 30 0 14 0 0 00166666666 15 30 17 1 5mH c5 17 0 1pF r5 17 0 500 Transimpedance Stage g1 0 18 17 0 1 0 rol 18 0 1Meg cdp 18 0 5pF Output Stage q1 4 18 19 qp q2 7 18 20 qn q3 7 19 21 qn q4 4 20 22 qp r7 21 6 4 r8 22 6 4
15
TD is 6 4in
EL2020C
50 MHz Current Feedback Amplifier
EL2020 Macromodel
ios1 7 19 2 5mA ios2 20 4 2 5mA Supply ips 7 4 3mA Error Terms ivos 0 23 5mA vxx 23 0 0V e4 24 0 6 0 1 0 e5 25 0 7 0 1 0 e6 26 0 4 0 1 0 r9 24 23 1K r10 25 23 1K r11 26 23 1K Models model qn npn (is e 5eb15 bf e 100 tf e 0 2nS) model qp pnp (is e 5eb15 bf e 100 tf e 0 2nS) model dclamp d(is e 1eb30 ibv e 0 266 bv e 1 67 n e 4) ends TD is 3 1in 16
Contd
EL2020C
50 MHz Current Feedback Amplifier
EL2020 Macromodel
2020 - 22
17
BLANK
18
BLANK
19
EL2020C
EL2020C
50 MHz Current Feedback Amplifier
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
December 1995 Rev G
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
20
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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