LM6171 High Speed Low Power Low Distortion Voltage Feedback Amplifier General Description Features The LM6171 is a high speed unity-gain stable voltage feedback amplifier. It offers a high slew rate of 3600V/µs and a unity-gain bandwidth of 100 MHz while consuming only 2.5 mA of supply current. The LM6171 has very impressive AC and DC performance which is a great benefit for high speed signal processing and video applications. The ± 15V power supplies allow for large signal swings and give greater dynamic range and signal-to-noise ratio. The LM6171 has high output current drive, low SFDR and THD, ideal for ADC/DAC systems. The LM6171 is specified for ± 5V operation for portable applications. The LM6171 is built on National’s advanced VIP™ III (Vertically Integrated PNP) complementary bipolar process. (Typical Unless Otherwise Noted) n Easy-To-Use Voltage Feedback Topology n Very High Slew Rate: 3600V/µs n Wide Unity-Gain-Bandwidth Product: 100 MHz n −3 dB Frequency @ AV = +2: 62 MHz n Low Supply Current: 2.5 mA n High CMRR: 110 dB n High Open Loop Gain: 90 dB n Specified for ± 15V and ± 5V Operation Applications n n n n n n n n n Multimedia Broadcast Systems Line Drivers, Switchers Video Amplifiers NTSC, PAL ® and SECAM Systems ADC/DAC Buffers HDTV Amplifiers Pulse Amplifiers and Peak Detectors Instrumentation Amplifier Active Filters Typical Performance Characteristics Closed Loop Frequency Response vs Supply Voltage (AV = +1) Large Signal Pulse Response AV = +1, VS = ± 15 DS012336-5 DS012336-9 VIP™ is a trademark of National Semiconductor Corporation. PAL ® is a registered trademark of and used under licence from Advanced Micro Devices, Inc. © 1999 National Semiconductor Corporation DS012336 www.national.com LM6171 High Speed Low Power Low Distortion Voltage Feedback Amplifier May 1998 Connection Diagram 8-Pin DIP/SO DS012336-1 Top View Ordering Information Package Temperature Range Industrial Transport Media NSC Drawing Rails N08E Rails M08A −40˚C to +85˚C 8-Pin LM6171AIN Molded DIP LM6171BIN 8-Pin LM6171AIM, LM6171BIM Small Outline LM6171AIMX, LM6171BIMX www.national.com Tape and Reel 2 Absolute Maximum Ratings (Note 1) Storage Temperature Range Maximum Junction Temperature (Note 4) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 2) Supply Voltage (V+–V−) Differential Input Voltage (Note 11) Common-Mode Voltage Range Output Short Circuit to Ground (Note 3) −65˚C to +150˚C 150˚C Operating Ratings (Note 1) 2.5 kV 36V Supply Voltage Junction Temperature Range LM6171AI, LM6171BI Thermal Resistance (θJA) N Package, 8-Pin Molded DIP M Package, 8-Pin Surface Mount ± 10V V+ −1.4V to V− + 1.4V 2.75V ≤ V+ ≤ 18V −40˚C ≤ TJ ≤ +85˚C 108˚C/W 172˚C/W Continuous ± 15V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +15V, V− = −15V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol VOS Parameter Conditions Input Offset Voltage Typ LM6171AI (Note 5) Limit Limit (Note 6) (Note 6) 3 6 mV 5 8 max 3 3 µA 4 4 max 2 2 µA 3 3 max 1.5 TC VOS Input Offset Voltage Average Drift 6 IB Input Bias Current 1 IOS RIN RO Input Offset Current Input Resistance 0.03 Common Mode 40 Differential Mode 4.9 Open Loop LM6171BI Units µV/˚C MΩ Ω 14 Output Resistance CMRR Common Mode VCM = ± 10V 110 Rejection Ratio PSRR Power Supply VS = ± 15V to ± 5V 95 Rejection Ratio VCM Input Common-Mode CMRR ≥ 60 dB 80 75 dB 75 70 min 85 80 dB 80 75 min ± 13.5 V Voltage Range AV Large Signal Voltage RL = 1 kΩ 90 Gain (Note 7) RL = 100Ω VO Output Swing 83 RL = 1 kΩ 13.3 −13.3 RL = 100Ω 11.6 −10.5 Continuous Output Current Sourcing, RL = 100Ω 116 (Open Loop) (Note 8) Sinking, RL = 100Ω 3 105 80 80 dB 70 70 min 70 70 dB 60 60 min 12.5 12.5 V 12 12 min −12.5 −12.5 V −12 −12 max 9 9 V 8.5 8.5 min −9 −9 V −8.5 −8.5 max 90 90 mA 85 85 min 90 90 mA 85 85 max www.national.com ± 15V DC Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +15V, V− = −15V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol Parameter IS Typ LM6171AI (Note 5) Limit LM6171BI Limit (Note 6) (Note 6) Units Sourcing, RL = 10Ω Sinking, RL = 10Ω 100 mA (in Linear Region) 80 mA Output Short Sourcing 135 mA Circuit Current Sinking 135 Continuous Output Current ISC Conditions Supply Current mA 2.5 4 4 mA 4.5 4.5 max ± 15V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +15V, V− = −15V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol SR GBW Parameter Slew Rate (Note 9) Conditions AV = +2, VIN = 13 VPP AV = +2, VIN = 10 VPP Unity Gain-Bandwidth Product −3 dB Frequency φm Phase Margin ts Settling Time (0.1%) Propagation Delay AV = +1 AV = +2 AV = −1, VOUT = ± 5V RL = 500Ω VIN = ± 5V, RL = 500Ω, Typ LM6171AI (Note 5) Limit LM6171BI Limit (Note 6) (Note 6) Units 3600 V/µs 3000 100 MHz 160 MHz 62 MHz 40 deg 48 ns 6 ns AV = −2 AD Differential Gain (Note 10) 0.03 % φD Differential Phase (Note 10) 0.5 deg en Input-Referred f = 1 kHz 12 f = 1 kHz 1 Voltage Noise in Input-Referred Current Noise ± 5V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +5V, V− = −5V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol VOS TC VOS Parameter Conditions Input Offset Voltage Typ LM6171AI (Note 5) Limit Limit (Note 6) (Note 6) 3 6 mV 5 8 max 1.2 Input Offset Voltage LM6171BI 4 Units µV/˚C Average Drift IB IOS www.national.com Input Bias Current 1 Input Offset Current 0.03 4 2.5 2.5 µA 3.5 3.5 max 1.5 1.5 µA 2.2 2.2 max ± 5V DC Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +5V, V− = −5V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol RIN RO Parameter Input Resistance Conditions Typ LM6171AI (Note 5) Limit Limit (Note 6) (Note 6) Common Mode 40 Differential Mode 4.9 Open Loop LM6171BI Units MΩ Ω 14 Output Resistance CMRR Common Mode VCM = ± 2.5V 105 Rejection Ratio PSRR Power Supply VS = ± 15V to ± 5V 95 Rejection Ratio VCM Input Common-Mode CMRR ≥ 60 dB 80 75 dB 75 70 min 85 80 dB 80 75 min ± 3.7 V Voltage Range AV Large Signal Voltage RL = 1 kΩ 84 Gain (Note 7) RL = 100Ω VO Output Swing 80 RL = 1 kΩ 3.5 −3.4 RL = 100Ω 3.2 −3.0 Continuous Output Current Sourcing, RL = 100Ω 32 (Open Loop) (Note 8) Sinking, RL = 100Ω ISC IS 30 Output Short Sourcing 130 Circuit Current Sinking 100 Supply Current 2.3 75 75 dB 65 65 min 70 70 dB 60 60 min 3.2 3.2 V 3 3 min −3.2 −3.2 V −3 −3 max 2.8 2.8 V 2.5 2.5 min −2.8 −2.8 V −2.5 −2.5 max 28 28 mA 25 25 min 28 28 mA 25 25 max mA mA 3 3 mA 3.5 3.5 max ± 5V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +5V, V− = −5V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol Parameter SR Slew Rate (Note 9) GBW Unity Gain-Bandwidth Conditions AV = +2, VIN = 3.5 VPP Typ LM6171AI (Note 5) Limit LM6171BI Limit (Note 6) (Note 6) Units 750 V/µs 70 MHz AV = +1 AV = +2 130 MHz 57 deg AV = −1, VOUT = +1V, RL = 500Ω VIN = ± 1V, RL = 500Ω, 60 ns 8 ns Product −3 dB Frequency φm Phase Margin ts Settling Time (0.1%) Propagation Delay 45 5 www.national.com ± 5V AC Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for TJ = 25˚C, V+ = +5V, V− = −5V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the temperature extremes Symbol Parameter Conditions Typ LM6171AI (Note 5) Limit LM6171BI Limit (Note 6) (Note 6) Units AV = −2 AD Differential Gain (Note 10) 0.04 % φD Differential Phase (Note 10) 0.7 deg en Input-Referred f = 1 kHz 11 f = 1 kHz 1 Voltage Noise in Input-Referred Current Noise Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics. Note 2: Human body model, 1.5 kΩ in series with 100 pF. Note 3: Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150˚C. Note 4: The maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(max) − TA)/θJA. All numbers apply for packages soldered directly into a PC board. Note 5: Typical Values represent the most likely parametric norm. Note 6: All limits are guaranteed by testing or statistical analysis. Note 7: Large signal voltage gain is the total output swing divided by the input signal required to produce that swing. For VS = ± 15V, VOUT = ± 5V. For VS = +5V, VOUT = ± 1V. Note 8: The open loop output current is the output swing with the 100Ω load resistor divided by that resistor. Note 9: Slew rate is the average of the rising and falling slew rates. Note 10: Differential gain and phase are measured with AV = +2, VIN = 1 VPP at 3.58 MHz and both input and output 75Ω terminated. Note 11: Differential input voltage is measured at VS = ± 15V. Typical Performance Characteristics Supply Current vs Supply Voltage Unless otherwise noted, TA = 25˚C Supply Current vs Temperature DS012336-20 Input Bias Current vs Temperature DS012336-21 Input Offset Voltage vs Common Mode Voltage DS012336-23 www.national.com Input Offset Voltage vs Temperature Short Circuit Current vs Temperature (Sourcing) DS012336-24 6 DS012336-22 DS012336-25 Typical Performance Characteristics Short Circuit Current vs Temperature (Sinking) Unless otherwise noted, TA = 25˚C (Continued) Output Voltage vs Output Current Output Voltage vs Output Current DS012336-26 CMRR vs Frequency DS012336-27 PSRR vs Frequency DS012336-29 Open Loop Frequency Response DS012336-28 PSRR vs Frequency DS012336-30 Open Loop Frequency Response DS012336-32 Gain Bandwidth Product vs Supply Voltage DS012336-33 7 DS012336-31 DS012336-34 www.national.com Typical Performance Characteristics Gain Bandwidth Product vs Load Capacitance Unless otherwise noted, TA = 25˚C (Continued) Large Signal Voltage Gain vs Load Large Signal Voltage Gain vs Load DS012336-35 Input Voltage Noise vs Frequency DS012336-36 Input Voltage Noise vs Frequency DS012336-38 Input Current Noise vs Frequency Input Current Noise vs Frequency DS012336-39 Slew Rate vs Supply Voltage DS012336-40 Slew Rate vs Input Voltage DS012336-42 DS012336-41 www.national.com DS012336-37 8 DS012336-43 Typical Performance Characteristics Slew Rate vs Load Capacitance Unless otherwise noted, TA = 25˚C (Continued) Open Loop Output Impedance vs Frequency DS012336-44 Large Signal Pulse Response AV = −1, VS = ± 15V Open Loop Output Impedance vs Frequency DS012336-45 Large Signal Pulse Response AV = −1, VS = ± 5V DS012336-47 Large Signal Pulse Response AV = +1, VS = ± 5V DS012336-46 Large Signal Pulse Response AV = +1, VS = ± 15V DS012336-48 Large Signal Pulse Response AV = +2, VS = ± 15V DS012336-50 Large Signal Pulse Response AV = +2, VS = ± 5V DS012336-51 9 DS012336-49 DS012336-52 www.national.com Typical Performance Characteristics Small Signal Pulse Response AV = −1, VS = ± 15V Unless otherwise noted, TA = 25˚C (Continued) Small Signal Pulse Response AV = −1, VS = ± 5V DS012336-53 Small Signal Pulse Response AV = +1, VS = ± 5V DS012336-54 Small Signal Pulse Response AV = +2, VS = ± 15V DS012336-56 Closed Loop Frequency Response vs Supply Voltage (AV = +1) DS012336-55 Small Signal Pulse Response AV = +2, VS = ± 5V DS012336-57 Closed Loop Frequency Response vs Supply Voltage (AV = +2) DS012336-59 www.national.com Small Signal Pulse Response AV = +1, VS = ± 15V Closed Loop Frequency Response vs Capacitive Load (AV = +1) DS012336-60 10 DS012336-58 DS012336-61 Typical Performance Characteristics Closed Loop Frequency Response vs Capacitive Load (AV = +1) Unless otherwise noted, TA = 25˚C (Continued) Closed Loop Frequency Response vs Capacitive Load (AV = +2) Closed Loop Frequency Response vs Capacitive Load (AV = +2) DS012336-62 DS012336-63 Total Harmonic Distortion vs Frequency Total Harmonic Distortion vs Frequency DS012336-65 Total Harmonic Distortion vs Frequency DS012336-64 Total Harmonic Distortion vs Frequency DS012336-66 Undistorted Output Swing vs Frequency DS012336-68 Undistorted Output Swing vs Frequency DS012336-69 11 DS012336-67 DS012336-70 www.national.com Typical Performance Characteristics Undistorted Output Swing vs Frequency Unless otherwise noted, TA = 25˚C (Continued) Undistorted Output Swing vs Frequency DS012336-71 Total Power Dissipation vs Ambient Temperature DS012336-72 DS012336-73 LM6171 Simplified Schematic DS012336-10 Application Information LM6171 Circuit Operation The class AB input stage in LM6171 is fully symmetrical and has a similar slewing characteristic to the current feedback amplifiers. In the LM6171 Simplfied Schematic, Q1 through Q4 form the equivalent of the current feedback input buffer, RE the equivalent of the feedback resistor, and stage A buffers the inverting input. The triple-buffered output stage isolates the gain stage from the load to provide low output impedance. LM6171 Performance Discussion The LM6171 is a high speed, unity-gain stable voltage feedback amplifier. It consumes only 2.5 mA supply current while providing a gain-bandwidth product of 100 MHz and a slew rate of 3600V/µs. It also has other great features such as low differential gain and phase and high output current. The LM6171 is a good choice in high speed circuits. The LM6171 is a true voltage feedback amplifier. Unlike current feedback amplifiers (CFAs) with a low inverting input impedance and a high non-inverting input impedance, both inputs of voltage feedback amplifiers (VFAs) have high impedance nodes. The low impedance inverting input in CFAs will couple with feedback capacitor and cause oscillation. As a result, CFAs cannot be used in traditional op amp circuits such as photodiode amplifiers, I-to-V converters and integrators. www.national.com LM6171 Slew Rate Characteristic The slew rate of LM6171 is determined by the current available to charge and discharge an internal high impedance node capacitor. The current is the differential input voltage divided by the total degeneration resistor RE. Therefore, the 12 Application Information (Continued) slew rate is proportional to the input voltage level, and the higher slew rates are achievable in the lower gain configurations. When a very fast large signal pulse is applied to the input of an amplifier, some overshoot or undershoot occurs. By placing an external series resistor such as 1 kΩ to the input of LM6171, the bandwidth is reduced to help lower the overshoot. DS012336-11 Layout Consideration FIGURE 1. Compensating for Input Capacitance PRINTED CIRCUIT BOARDS AND HIGH SPEED OP AMPS There are many things to consider when designing PC boards for high speed op amps. Without proper caution, it is very easy and frustrating to have excessive ringing, oscillation and other degraded AC performance in high speed circuits. As a rule, the signal traces should be short and wide to provide low inductance and low impedance paths. Any unused board space needs to be grounded to reduce stray signal pickup. Critical components should also be grounded at a common point to eliminate voltage drop. Sockets add capacitance to the board and can affect frequency performance. It is better to solder the amplifier directly into the PC board without using any socket. Power Supply Bypassing Bypassing the power supply is necessary to maintain low power supply impedance across frequency. Both positive and negative power supplies should be bypassed individually by placing 0.01 µF ceramic capacitors directly to power supply pins and 2.2 µF tantalum capacitors close to the power supply pins. USING PROBES Active (FET) probes are ideal for taking high frequency measurements because they have wide bandwidth, high input impedance and low input capacitance. However, the probe ground leads provide a long ground loop that will produce errors in measurement. Instead, the probes can be grounded directly by removing the ground leads and probe jackets and using scope probe jacks. COMPONENTS SELECTION AND FEEDBACK RESISTOR It is important in high speed applications to keep all component leads short because wires are inductive at high frequency. For discrete components, choose carbon composition-type resistors and mica-type capacitors. Surface mount components are preferred over discrete components for minimum inductive effect. Large values of feedback resistors can couple with parasitic capacitance and cause undesirable effects such as ringing or oscillation in high speed amplifiers. For LM6171, a feedback resistor of 510Ω gives optimal performance. DS012336-12 FIGURE 2. Power Supply Bypassing Termination In high frequency applications, reflections occur if signals are not properly terminated. Figure 3 shows a properly terminated signal while Figure 4 shows an improperly terminated signal. Compensation for Input Capacitance The combination of an amplifier’s input capacitance with the gain setting resistors adds a pole that can cause peaking or oscillation. To solve this problem, a feedback capacitor with a value CF > (RG x CIN)/RF can be used to cancel that pole. For LM6171, a feedback capacitor of 2 pF is recommended. Figure 1 illustrates the compensation circuit. DS012336-14 FIGURE 3. Properly Terminated Signal 13 www.national.com Application Information (Continued) DS012336-13 FIGURE 5. Isolation Resistor Used to Drive Capacitive Load DS012336-15 FIGURE 4. Improperly Terminated Signal To minimize reflection, coaxial cable with matching characteristic impedance to the signal source should be used. The other end of the cable should be terminated with the same value terminator or resistor. For the commonly used cables, RG59 has 75Ω characteristic impedance, and RG58 has 50Ω characteristic impedance. Driving Capacitive Loads Amplifiers driving capacitive loads can oscillate or have ringing at the output. To eliminate oscillation or reduce ringing, an isolation resistor can be placed as shown below in Figure 5. The combination of the isolation resistor and the load capacitor forms a pole to increase stablility by adding more phase margin to the overall system. The desired performance depends on the value of the isolation resistor; the bigger the isolation resistor, the more damped the pulse response becomes. For LM6171, a 50Ω isolation resistor is recommended for initial evaluation. Figure 6 shows the LM6171 driving a 200 pF load with the 50Ω isolation resistor. www.national.com DS012336-16 FIGURE 6. The LM6171 Driving a 200 pF Load with a 50Ω Isolation Resistor Power Dissipation The maximum power allowed to dissipate in a device is defined as: PD = (TJ(max) − TA)/θJA Where PD is the power dissipation in a device TJ(max) is the maximum junction temperature TA is the ambient temperature θJA is the thermal resistance of a particular package For example, for the LM6171 in a SO-8 package, the maximum power dissipation at 25˚C ambient temperature is 730 mW. Thermal resistance, θJA, depends on parameters such as die size, package size and package material. The smaller the die size and package, the higher θJA becomes. The 8-pin DIP package has a lower thermal resistance (108˚C/W) than that of 8-pin SO (172˚C/W). Therefore, for higher dissipation capability, use an 8-pin DIP package. 14 Application Information (Continued) Multivibrator The total power dissipated in a device can be calculated as: PD = PQ + PL PQ is the quiescent power dissipated in a device with no load connected at the output. PL is the power dissipated in the device with a load connected at the output; it is not the power dissipated by the load. Furthermore, PQ = supply current x total supply voltage with no load PL = output current x (voltage difference between supply voltage and output voltage of the same supply) For example, the total power dissipated by the LM6171 with VS = ± 15V and output voltage of 10V into 1 kΩ load resistor (one end tied to ground) is PD = PQ + PL = (2.5 mA) x (30V) + (10 mA) x (15V − 10V) = 75 mW + 50 mW = 125 mW DS012336-18 Application Circuits Pulse Width Modulator Fast Instrumentation Amplifier DS012336-19 Design Kit A design kit is available for the LM6171. The design kit contains: DS012336-17 • • • • High Speed Evaluation Board LM6171 in 8-pin DIP Package LM6171 Datasheet Pspice Macromodel Diskette With the LM6171 Macromodel • An Amplifier Selection Guide Pitch Pack A pitch pack is available for the LM6171. The pitch pack contains: • • • • High Speed Evaluation Board LM6171 in 8-pin DIP Package LM6171 Datasheet Pspice Macromodel Diskette With the LM6171 Macromodel Contact your local National Semiconductor sales office to obtain a pitch pack. 15 www.national.com Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin Small Outline Package NS Package Number M08A 8-Pin Molded DIP Package NS Package Number N08E www.national.com 16 LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. National Semiconductor Corporation Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: [email protected] www.national.com National Semiconductor Europe Fax: +49 (0) 1 80-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. LM6171 High Speed Low Power Low Distortion Voltage Feedback Amplifier Notes