LT1357 25MHz, 600V/µs Op Amp U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ The LT ®1357 is a high speed, very high slew rate operational amplifier with outstanding AC and DC performance. The LT1357 has much lower supply current, lower input offset voltage, lower input bias current, and higher DC gain than devices with comparable bandwidth. The circuit topology is a voltage feedback amplifier with the slewing characteristics of a current feedback amplifier. The amplifier is a single gain stage with outstanding settling characteristics which makes the circuit an ideal choice for data acquisition systems. The output drives a 500Ω load to ±12V with ±15V supplies and a 150Ω load to ±2.5V on ±5V supplies. The amplifier is also stable with any capacitive load which makes it useful in buffer or cable driver applications. 25MHz Gain Bandwidth 600V/µs Slew Rate 2.5mA Maximum Supply Current Unity-Gain Stable C-LoadTM Op Amp Drives All Capacitive Loads 8nV/√Hz Input Noise Voltage 600µV Maximum Input Offset Voltage 500nA Maximum Input Bias Current 120nA Maximum Input Offset Current 20V/mV Minimum DC Gain, RL=1k 115ns Settling Time to 0.1%, 10V Step 220ns Settling Time to 0.01%, 10V Step ±12V Minimum Output Swing into 500Ω ±2.5V Minimum Output Swing into 150Ω Specified at ±2.5V, ±5V, and ±15V The LT1357 is a member of a family of fast, high performance amplifiers using this unique topology and employing Linear Technology Corporation’s advanced bipolar complementary processing. For dual and quad amplifier versions of the LT1357 see the LT1358/LT1359 data sheet. For higher bandwidth devices with higher supply current see the LT1360 through LT1365 data sheets. For lower supply current amplifiers see the LT1354 and LT1355/ LT1356 data sheets. Singles, duals, and quads of each amplifier are available. U APPLICATIONS ■ ■ ■ ■ ■ Wideband Amplifiers Buffers Active Filters Data Acquisition Systems Photodiode Amplifiers , LTC and LT are registered trademarks of Linear Technology Corporation. C-Load is a trademark of Linear Technology Corporation U TYPICAL APPLICATION AV = –1 Large-Signal Response DAC I-to-V Converter 6pF DAC INPUTS 12 5k – 565A-TYPE LT1357 VOUT + 0.1µF 5k ( ) V VOS + IOS 5kΩ + OUT < 1LSB A VOL 1357 TA01 1357 TA02 1 LT1357 W W U W ABSOLUTE MAXIMUM RATINGS Total Supply Voltage (V + to V –) ............................... 36V Differential Input Voltage (Transient Only, Note 1) ... ±10V Input Voltage ............................................................ ±VS Output Short-Circuit Duration (Note 2) ............ Indefinite Operating Temperature Range ................ –40°C to 85°C Specified Temperature Range (Note 6) ... –40°C to 85°C Maximum Junction Temperature (See Below) Plastic Package ................................................ 150°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C U W U PACKAGE/ORDER INFORMATION TOP VIEW NULL 1 8 NULL –IN 2 7 V+ +IN 3 6 VOUT V– 4 5 NC ORDER PART NUMBER LT1357CN8 ORDER PART NUMBER TOP VIEW NULL 1 8 NULL –IN 2 7 V+ +IN 3 6 VOUT V– 4 5 NC N8 PACKAGE, 8-LEAD PLASTIC DIP S8 PACKAGE, 8-LEAD PLASTIC SOIC TJMAX = 150°C, θJA = 130°C/ W TJMAX = 150°C, θJA = 190°C/ W LT1357CS8 S8 PART MARKING 1357 Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS TA = 25°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VOS Input Offset Voltage ±15V ±5V ±2.5V IOS Input Offset Current ±2.5V to ±15V IB Input Bias Current ±2.5V to ±15V en Input Noise Voltage f = 10kHz ±2.5V to ±15V 8 nV/√Hz in Input Noise Current f = 10kHz ±2.5V to ±15V 0.8 pA/√Hz RIN Input Resistance VCM = ±12V Differential ±15V ±15V 35 80 6 MΩ MΩ CIN Input Capacitance ±15V 3 pF Input Voltage Range + ±15V ±5V ±2.5V 12.0 2.5 0.5 13.4 3.5 1.1 V V V Input Voltage Range – ±15V ±5V ±2.5V CMRR Common Mode Rejection Ratio VCM = ±12V VCM = ±2.5V VCM = ±0.5V PSRR Power Supply Rejection Ratio VS = ±2.5V to ±15V AVOL Large-Signal Voltage Gain VOUT = ±12V, RL = 1k VOUT = ±10V, RL = 500Ω VOUT = ±2.5V, RL = 1k VOUT = ±2.5V, RL = 500Ω VOUT = ±2.5V, RL = 150Ω VOUT = ±1V, RL = 500Ω 2 VSUPPLY ±15V ±5V ±2.5V ±15V ±15V ±5V ±5V ±5V ±2.5V MIN TYP MAX UNITS 0.2 0.2 0.3 0.6 0.6 0.8 mV mV mV 40 120 nA 120 500 nA –13.2 –12.0 – 3.3 – 2.5 – 0.9 – 0.5 V V V 80 78 68 97 84 75 dB dB dB 92 106 dB 20.0 7.0 20.0 7.0 1.5 7.0 65 25 45 25 6 30 V/mV V/mV V/mV V/mV V/mV V/mV LT1357 ELECTRICAL CHARACTERISTICS TA = 25°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VSUPPLY MIN TYP MAX UNITS VOUT Output Swing RL = 1k, VIN = ±40mV RL = 500Ω, VIN = ±40mV RL = 500Ω, VIN = ±40mV RL = 150Ω, VIN = ±40mV RL = 500Ω, VIN = ±40mV ±15V ±15V ±5V ±5V ±2.5V 13.3 12.0 3.5 2.5 1.3 13.8 12.8 4.0 3.3 1.7 ±V ±V ±V ±V ±V IOUT Output Current VOUT = ±12V VOUT = ±2.5V ±15V ±5V 24.0 16.7 30 25 mA mA ISC Short-Circuit Current VOUT = 0V, VIN = ±3V ±15V 30 42 mA SR Slew Rate AV = –2, (Note 3) ±15V ±5V 300 150 600 220 V/µs V/µs Full Power Bandwidth 10V Peak, (Note 4) 3V Peak, (Note 4) ±15V ±5V 9.6 11.7 MHz MHz GBW Gain Bandwidth f = 200kHz, RL = 2k ±15V ±5V ±2.5V 25 22 20 MHz MHz MHz tr , tf Rise Time, Fall Time AV = 1, 10%-90%, 0.1V ±15V ±5V 8 9 ns ns Overshoot AV = 1, 0.1V ±15V ±5V 27 27 % % Propagation Delay 50% VIN to 50% VOUT, 0.1V ±15V ±5V 9 11 ns ns Settling Time 10V Step, 0.1%, AV = –1 10V Step, 0.01%, AV = –1 5V Step, 0.1%, AV = –1 5V Step, 0.01%, AV = –1 ±15V ±15V ±5V ±5V 115 220 110 380 ns ns ns ns Differential Gain f = 3.58MHz, AV = 2, RL = 1k ±15V ±5V 0.1 0.1 % % Differential Phase f = 3.58MHz, AV = 2, RL = 1k ±15V ±5V 0.50 0.35 RO Output Resistance AV = 1, f = 100kHz ±15V 0.3 IS Supply Current ±15V ±5V 2.0 1.9 2.5 2.4 mA mA TYP MAX UNITS 0.8 0.8 1.0 mV mV mV ts 18 15 Deg Deg Ω 0°C ≤ TA ≤ 70°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER VOS Input Offset Voltage Input VOS Drift IOS CONDITIONS (Note 5) Input Offset Current IB Input Bias Current CMRR Common Mode Rejection Ratio VCM = ±12V VCM = ±2.5V VCM = ±0.5V PSRR Power Supply Rejection Ratio VS = ±2.5V to ±15V AVOL Large-Signal Voltage Gain VOUT = ±12V, RL = 1k VOUT = ±10V, RL = 500Ω VOUT = ±2.5V, RL = 1k VOUT = ±2.5V, RL = 500Ω VOUT = ±2.5V, RL = 150Ω VOUT = ±1V, RL = 500Ω VSUPPLY MIN ±15V ±5V ±2.5V ● ● ● ±2.5V to ±15V ● ±2.5V to ±15V ● ±2.5V to ±15V ● ±15V ±5V ±2.5V ● ● ● 79 77 67 dB dB dB ● 90 dB ● ● ● ● ● ● 15 5 15 5 1 5 V/mV V/mV V/mV V/mV V/mV V/mV ±15V ±15V ±5V ±5V ±5V ±2.5V 5 8 µV/°C 180 nA 750 nA 3 LT1357 ELECTRICAL CHARACTERISTICS 0°C ≤ TA ≤ 70°C, VCM = 0V unless otherwise noted. SYMBOL PARAMETER CONDITIONS VSUPPLY MIN TYP MAX UNITS VOUT Output Swing RL = 1k, VIN = ±40mV RL = 500Ω, VIN = ±40mV RL = 500Ω, VIN = ±40mV RL = 150Ω, VIN = ±40mV RL = 500Ω, VIN = ±40mV ±15V ±15V ±5V ±5V ±2.5V ● ● ● ● ● 13.2 11.5 3.4 2.3 1.2 ±V ±V ±V ±V ±V IOUT Output Current VOUT = ±11.5V VOUT = ±2.3V ±15V ±5V ● ● 23.0 15.3 mA mA ISC Short-Circuit Current VOUT = 0V, VIN = ±3V ±15V ● 25 mA SR Slew Rate AV = –2, (Note 3) ±15V ±5V ● ● 225 125 V/µs V/µs GBW Gain-Bandwidth f = 200kHz,RL = 2k ±15V ±5V ● ● 15 12 MHz MHz IS Supply Current ±15V ±5V ● ● VSUPPLY ±15V ±5V ±2.5V ● ● ● ±2.5V to ±15V ● 2.9 2.8 mA mA TYP MAX 1.3 1.3 1.5 UNITS mV mV mV 5 8 µV/°C –40°C ≤ TA ≤ 85°C, VCM = 0V unless otherwise noted. (Note 6) SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS Input VOS Drift (Note 5) MIN IOS Input Offset Current ±2.5V to ±15V ● 300 nA IB Input Bias Current ±2.5V to ±15V ● 900 nA CMRR Common Mode Rejection Ratio VCM = ±12V VCM = ±2.5V VCM = ±0.5V ±15V ±5V ±2.5V ● ● ● PSRR Power Supply Rejection Ratio VS = ±2.5V to ±15V ● 90 dB AVOL Large-Signal Voltage Gain VOUT = ±12V, RL = 1k VOUT = ±10V, RL = 500Ω VOUT = ±2.5V, RL = 1k VOUT = ±2.5V, RL = 500Ω VOUT = ±2.5V, RL = 150Ω VOUT = ±1V, RL = 500Ω ±15V ±15V ±5V ±5V ±5V ±2.5V ● ● ● ● ● ● 10.0 2.5 10.0 2.5 0.6 2.5 V/mV V/mV V/mV V/mV V/mV V/mV VOUT Output Swing RL = 1k, VIN = ±40mV RL = 500Ω, VIN = ±40mV RL = 500Ω, VIN = ±40mV RL = 150Ω, VIN = ±40mV RL = 500Ω, VIN = ±40mV ±15V ±15V ±5V ±5V ±2.5V ● ● ● ● ● 13.0 11.0 3.4 2.1 1.2 ±V ±V ±V ±V ±V IOUT Output Current VOUT = ±11V VOUT = ±2.1V ±15V ±5V ● ● 22 14 mA mA ISC Short-Circuit Current VOUT = 0V, VIN = ±3V ±15V ● 24 mA SR Slew Rate AV = –2, (Note 3) ±15V ±5V ● ● 180 100 V/µs V/µs GBW Gain-Bandwith f = 200kHz, RL = 2k ±15V ±5V ● ● 14 11 MHz MHz IS Supply Current ±15V ±5V ● ● 4 78 76 66 dB dB dB 3.0 2.9 mA mA LT1357 ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the full specified temperature range. Note 1: Differential inputs of ±10V are appropriate for transient operation only, such as during slewing. Large, sustained differential inputs will cause excessive power dissipation and may damage the part. See Input Considerations in the Applications Information section of this data sheet for more details. Note 2: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted indefinitely. Note 3: Slew rate is measured between ±10V on the output with ±6V input for ±15V supplies and ±1V on the output with ±1.75V input for ±5V supplies. Note 4: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2πVP. Note 5: This parameter is not 100% tested. Note 6: The LT1357 is designed, characterized and expected to meet these extended temperature limits, but is not tested at – 40°C and at 85°C. Guaranteed I grade parts are available; consult factory. U W TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Supply Voltage and Temperature V+ 3.0 400 TA = 25°C ∆VOS < 1mV –0.5 125°C 2.0 25°C –55°C 1.5 1.0 VS = ±15V TA = 25°C IB+ + IB– IB = ———— 2 300 –1.0 INPUT BIAS CURRENT (nA) COMMON-MODE RANGE (V) 2.5 SUPPLY CURRENT (mA) Input Bias Current vs Input Common-Mode Voltage Input Common-Mode Range vs Supply Voltage –1.5 –2.0 2.0 1.5 1.0 200 100 0 –100 0.5 V– 0.5 5 10 15 SUPPLY VOLTAGE (±V) 20 0 5 10 15 SUPPLY VOLTAGE (±V) 1357 G01 100 300 250 200 150 100 INPUT VOLTAGE NOISE (nV/√Hz) 350 Open-Loop Gain vs Resistive Load 100 10 VS = ±15V TA = 25°C AV = 101 RS = 100k TA = 25°C en 10 1 in INPUT CURRENT NOISE (pA/√Hz) INPUT BIAS CURRENT (nA) 400 15 1357 G03 Input Noise Spectral Density VS = ±15V IB+ + IB– IB = ———— 2 –10 –5 0 5 10 INPUT COMMON-MODE VOLTAGE (V) 1357 G02 Input Bias Current vs Temperature 450 –200 –15 20 VS = ±15V VS = ±5V 90 OPEN-LOOP GAIN (dB) 0 80 70 60 50 0 –50 1 –25 0 25 50 75 TEMPERATURE (°C) 100 125 1358/1359 G04 10 100 1k 10k FREQUENCY (Hz) 0.1 100k 1357 G05 50 10 100 1k LOAD RESISTANCE (Ω) 10k 1357 G06 5 LT1357 U W TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage Swing vs Supply Voltage Open-Loop Gain vs Temperature V + –0.5 V+ TA = 25°C RL = 1k VO = ±12V VS = ±15V 99 98 97 96 95 –2 RL = 500Ω –3 3 RL = 500Ω 2 1 94 93 –50 V –25 0 25 50 75 TEMPERATURE (°C) 100 0 2.5 –40°C 1.5 V – +0.5 –50 –40 –30 –20 –10 0 10 20 30 40 50 OUTPUT CURRENT (mA) 20 1357 G09 Settling Time vs Output Step (Inverting) 10 8 6 50 45 SINK 40 SOURCE 35 1mV 4 2 0 –2 –4 –8 10mV 50 100 150 200 SETTLING TIME (ns) GAIN (dB) 60 40 VS = ±5V 20 20 0 10 0.1 0 100M 1357 G13 6 –10 10k 34 80 VS = ±5V AV = –1 RF = RG = 2k TA = 25°C 100k 1M 10M FREQUENCY (Hz) 48 TA = 25°C 46 PHASE MARGIN 32 44 30 42 28 40 26 38 24 36 22 34 GAIN-BANDWIDTH 20 100M 1357 G14 32 18 0 5 10 15 SUPPLY VOLTAGE (±V) 30 20 1357 G15 PHASE MARGIN (DEG) 1 30 GAIN 50 36 100 PHASE (DEG) AV = 1 40 VS = ±15V VS = ±15V AV = 10 250 38 GAIN-BANDWIDTH (MHz) PHASE 50 10 100 150 200 SETTLING TIME (ns) 1357 G12 120 60 1M 10M FREQUENCY (Hz) 50 Gain-Bandwidth and Phase Margin vs Supply Voltage 70 AV = 100 100k 250 Gain and Phase vs Frequency VS = ±15V TA = 25°C 0.01 10k –10 1357 G11 Output Impedance vs Frequency 100 10mV –4 –8 125 VS = ±15V AV = –1 0 –2 –6 1357 G10 1k 2 1mV –10 100 1mV 4 1mV –6 30 10mV 6 OUTPUT SWING (V) 55 0 25 50 75 TEMPERATURE (°C) 85°C 2.0 VS = ±15V AV = 1 10mV 8 60 –25 25°C 25°C 10 OUTPUT SWING (V) OUTPUT SHORT-CIRCUIT CURRENT (mA) –2.5 Settling Time vs Output Step (Noninverting) VS = ±5V 25 –50 OUTPUT IMPEDANCE (Ω) –2.0 1357 G08 Output Short-Circuit Current vs Temperature 65 –40°C 1.0 5 10 15 SUPPLY VOLTAGE (±V) 1357 G07 85°C –1.5 RL = 1k + 125 VS = ±5V VIN = 100mV –1.0 RL = 1k –1 OUTPUT VOLTAGE SWING (V) 100 OUTPUT VOLTAGE SWING (V) 101 OPEN-LOOP GAIN (dB) Output Voltage Swing vs Load Current LT1357 U W TYPICAL PERFORMANCE CHARACTERISTICS Gain-Bandwidth and Phase Margin vs Temperature PHASE MARGIN VS = ±5V 4 46 3 44 42 30 40 28 GAIN-BANDWIDTH VS = ±15V 26 24 22 GAIN-BANDWIDTH VS = ±5V 20 18 –50 –25 0 25 50 75 TEMPERATURE (°C) 100 38 36 5 TA = 25°C AV = 1 RL = 2k 2 1 0 –1 ±5V –2 –3 32 –4 30 125 3 ±15V 2 34 ±2.5V C = 100pF 2 0 C = 50pF –2 –4 C=0 –6 –8 –10 100k 1M 10M FREQUENCY (Hz) VS = ±15V TA = 25°C – PSRR 80 60 40 20 Slew Rate vs Supply Voltage 10k 100k 1M FREQUENCY (Hz) 10M 80 60 40 20 100M 1k 400 10M 100M 1000 VS = ±15V AV = –1 RF = RG = 2k SR+ + SR – SR = ————— 2 TA = 25°C 900 VS = ±15V 500 200 100k 1M FREQUENCY (Hz) Slew Rate vs Input Level Slew Rate vs Temperature 400 10k 1357 G21 600 SLEW RATE (V/µs) SLEW RATE (V/µs) 100 1357 G20 1000 600 VS = ±15V TA = 25°C 0 1k 1358/1359 G19 800 100M Common-Mode Rejection Ratio vs Frequency 120 +PSRR 0 100 100M AV = –1 RF = RG = 2k SR+ + SR– SR = ————— 2 TA = 25°C 10M 1M FREQUENCY (Hz) 1357 G18 800 SR+ + SR– SR = ————— 2 AV = –2 SLEW RATE (V/µs) VOLTAGE MAGNITUDE (dB) C = 500pF POWER SUPPLY REJECTION RATIO (dB) 100 4 –5 100k 100M Power Supply Rejection Ratio vs Frequency C = 1000pF ±2.5V –4 10M 1M FREQUENCY (Hz) ±15V ±5V 1357 G17 10 6 0 –1 –3 –5 100k Frequency Response vs Capacitive Load 8 1 –2 1357 G16 VS = ±15V TA = 25°C AV = –1 TA = 25°C AV = –1 RF = RG = 2k 4 COMMON-MODE REJECTION RATIO (dB) 32 5 48 PHASE MARGIN (DEG) GAIN-BANDWIDTH (MHz) 34 50 GAIN (dB) PHASE MARGIN VS = ±15V GAIN (dB) 38 36 Frequency Response vs Supply Voltage (AV = –1) Frequency Response vs Supply Voltage (AV = 1) 300 200 VS = ±5V 700 600 500 400 300 200 100 100 0 0 5 10 SUPPLY VOLTAGE (±V) 15 1357 G22 0 –50 0 –25 0 25 50 75 TEMPERATURE (°C) 100 125 1357 G23 0 2 4 6 8 10 12 14 16 18 20 INPUT LEVEL (VP-P) 1357 G24 7 LT1357 U W TYPICAL PERFORMANCE CHARACTERISTICS 0.01 30 0.001 AV = 1 AV = 1 20 15 10 5 1k 10k FREQUENCY (Hz) VS = ±15V RL = 2k AV = 1, 1% MAX DISTORTION AV = –1, 2% MAX DISTORTION 0 100k 100k 1M FREQUENCY (Hz) DIFFERENTIAL PHASE (DEGREES) HARMONIC DISTORTION (dB) –60 –70 2ND HARMONIC –80 –90 100k 200k 400k 1M 2M FREQUENCY (Hz) 4M 10M DIFFERENTIAL GAIN 0.10 0.05 0.50 DIFFERENTIAL PHASE 0.45 0.40 0.35 AV = 2 RL = 1k TA = 25°C ±5 ±10 SUPPLY VOLTAGE (V) 1357 G28 1357 TA31 8 ±15 VS = ±15V TA = 25°C AV = 1 50 AV = –1 0 10p 100p 1000p 0.01µ 0.1µ CAPACITIVE LOAD (F) 1µ 1357 G30 1354 G29 Small-Signal Transient (AV = –1) Small-Signal Transient (AV = 1) 10M Capacitive Load Handling DIFFERENTIAL GAIN (PERCENT) –50 1M FREQUENCY (Hz) 100 0.15 3RD HARMONIC VS = ±5V RL = 2k 2% MAX DISTORTION 1357 G27 Differential Gain and Phase vs Supply Voltage –30 –40 4 1357 G26 2nd and 3rd Harmonic Distortion vs Frequency VS = ±15V VO = 2VP-P RL = 2k AV = 2 AV = 1 6 0 100k 10M 1357 G25 AV = –1 8 2 OVERSHOOT (%) 100 OUTPUT VOLTAGE (VP-P) 25 AV = –1 0.0001 10 10 AV = –1 TA = 25°C VO = 3VRMS RL = 2k OUTPUT VOLTAGE (VP-P) TOTAL HARMONIC DISTORTION (%) Undistorted Output Swing vs Frequency (±5V) Undistorted Output Swing vs Frequency (±15V) Total Harmonic Distortion vs Frequency Small-Signal Transient (AV = –1, CL = 1000pF) 1357 TA32 1357 TA33 LT1357 U W TYPICAL PERFORMANCE CHARACTERISTICS Large-Signal Transient (AV = 1) Large-Signal Transient (AV = 1, CL = 10,000pF) Large-Signal Transient (AV = –1) 1357 TA34 1357 TA35 1357 TA36 U U W U APPLICATIONS INFORMATION The LT1357 may be inserted directly into many high speed amplifier applications improving both DC and AC performance, provided that the nulling circuitry is removed. The suggested nulling circuit for the LT1357 is shown below. Offset Nulling V 3 6 LT1357 2 4 – CF > (RG • CIN)/RF + 7 + The parallel combination of the feedback resistor and gain setting resistor on the inverting input can combine with the input capacitance to form a pole which can cause peaking or oscillations. For feedback resistors greater than 5kΩ, a parallel capacitor of value 8 1 10k should be used to cancel the input pole and optimize dynamic performance. For unity-gain applications where a large feedback resistor is used, CF should be greater than or equal to CIN. Capacitive Loading V– 1357 AI01 Layout and Passive Components The LT1357 amplifier is easy to apply and tolerant of less than ideal layouts. For maximum performance (for example, fast settling time) use a ground plane, short lead lengths and RF-quality bypass capacitors (0.01µF to 0.1µF). For high drive current applications use low ESR bypass capacitors (1µF to 10µF tantalum). Sockets should be avoided when maximum frequency performance is required, although low profile sockets can provide reasonable performance up to 50MHz. For more details see Design Note 50. The LT1357 is stable with any capacitive load. This is accomplished by sensing the load induced output pole and adding compensation at the amplifier gain node. As the capacitive load increases, both the bandwidth and phase margin decrease so there will be peaking in the frequency domain and in the transient response as shown in the typical performance curves.The photo of the small-signal response with 1000pF load shows 50% peaking. The large-signal response with a 10,000pF load shows the output slew rate being limited to 5V/µs by the short-circuit current. Coaxial cable can be driven directly, but for best pulse fidelity a resistor of value equal to the characteristic impedance of the cable (i.e., 75Ω) should be placed in 9 LT1357 U W U U APPLICATIONS INFORMATION series with the output. The other end of the cable should be terminated with the same value resistor to ground. Input Considerations Each of the LT1357 inputs is the base of an NPN and a PNP transistor whose base currents are of opposite polarity and provide first-order bias current cancellation. Because of variation in the matching of NPN and PNP beta, the polarity of the input bias current can be positive or negative. The offset current does not depend on NPN/PNP beta matching and is well controlled. The use of balanced source resistance at each input is recommended for applications where DC accuracy must be maximized. The inputs can withstand transient differential input voltages up to 10V without damage and need no clamping or source resistance for protection. Differential inputs, however, generate large supply currents (tens of mA) as required for high slew rates. If the device is used with sustained differential inputs, the average supply current will increase, excessive power dissipation will result and the part may be damaged. The part should not be used as a comparator, peak detector or other open-loop application with large, sustained differential inputs. Under normal, closed-loop operation, an increase of power dissipation is only noticeable in applications with large slewing outputs and is proportional to the magnitude of the differential input voltage and the percent of the time that the inputs are apart. Measure the average supply current for the application in order to calculate the power dissipation. Power Dissipation The LT1357 combines high speed and large output drive in a small package. Because of the wide supply voltage range, it is possible to exceed the maximum junction temperature under certain conditions. Maximum junction temperature (TJ) is calculated from the ambient temperature (TA) and power dissipation (PD) as follows: LT1357CN8: TJ = TA + (PD • 130°C/W) LT1357CS8: TJ = TA + (PD • 190°C/W) 10 Worst-case power dissipation occurs at the maximum supply current and when the output voltage is at 1/2 of either supply voltage (or the maximum swing if less than 1/2 supply voltage). Therefore PDMAX is: PDMAX = (V+ – V –)(ISMAX) + (V+/2)2/RL Example: LT1357CS8 at 70°C, VS = ±15V, RL = 120Ω (Note: the minimum short-circuit current at 70°C is 25mA, so the output swing is guaranteed only to 3V with 120Ω.) PDMAX = (30V • 2.9mA) + (15V–3V)(25mA) = 387mW TJMAX = 70°C + (387mW • 190°C/W) = 144°C Circuit Operation The LT1357 circuit topology is a true voltage feedback amplifier that has the slewing behavior of a current feedback amplifier. The operation of the circuit can be understood by referring to the simplified schematic. The inputs are buffered by complementary NPN and PNP emitter followers which drive a 500Ω resistor. The input voltage appears across the resistor generating currents which are mirrored into the high impedance node. Complementary followers form an output stage which buffers the gain node from the load. The bandwidth is set by the input resistor and the capacitance on the high impedance node. The slew rate is determined by the current available to charge the gain node capacitance. This current is the differential input voltage divided by R1, so the slew rate is proportional to the input. Highest slew rates are therefore seen in the lowest gain configurations. For example, a 10V output step in a gain of 10 has only a 1V input step, whereas the same output step in unity-gain has a ten times greater input step. The curve of Slew Rate vs Input Level illustrates this relationship. The LT1357 is tested for slew rate in a gain of –2 so higher slew rates can be expected in gains of 1 and –1, and lower slew rates in higher gain configurations. The RC network across the output stage is bootstrapped when the amplifier is driving a light or moderate load and LT1357 U U W U APPLICATIONS INFORMATION has no effect under normal operation. When driving a capacitive load (or a low value resistive load) the network is incompletely bootstrapped and adds to the compensation at the high impedance node. The added capacitance slows down the amplifier which improves the phase margin by moving the unity-gain frequency away from the pole formed by the output impedance and the capacitive load. The zero created by the RC combination adds phase to ensure that even for very large load capacitances, the total phase lag can never exceed 180 degrees (zero phase margin) and the amplifier remains stable. W W SI PLIFIED SCHE ATIC V+ R1 500Ω +IN RC OUT –IN C CC V– 1357 SS01 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) 0.045 – 0.065 (1.143 – 1.651) 0.130 ± 0.005 (3.302 ± 0.127) 0.065 (1.651) TYP 0.100 ± 0.010 (2.540 ± 0.254) 0.400* (10.160) MAX 8 7 6 5 1 2 3 4 0.255 ± 0.015* (6.477 ± 0.381) 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) N8 1197 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 11 LT1357 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 0.010 – 0.020 × 45° (0.254 – 0.508) 8 0.053 – 0.069 (1.346 – 1.752) 0.008 – 0.010 (0.203 – 0.254) 5 6 0.004 – 0.010 (0.101 – 0.254) 0°– 8° TYP 0.016 – 0.050 0.406 – 1.270 7 0.014 – 0.019 (0.355 – 0.483) 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 0.050 (1.270) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 1 2 3 4 SO8 0996 U TYPICAL APPLICATIONS Instrumentation Amplifier R5 432Ω R1 20k R4 20k 3.4k R2 2k 2.61k 100pF 47pF R3 2k – LT1357 – 200kHz, 4th Order Butterworth Filter + 3.4k 5.62k VIN – LT1357 330pF VOUT – 2.61k + 1000pF + VIN 5.11k LT1357 – VOUT LT1357 + + 1357 TA04 R4 1 R2 R3 R2 + R3 1 + = 104 AV = + + R3 2 R1 R4 R5 TRIM R5 FOR GAIN TRIM R1 FOR COMMON MODE REJECTION BW = 250kHz 1357 TA03 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1358/LT1359 Dual/Quad 2mA, 25MHz, 600V/µs Op Amp Good DC Precision, Stable with All Capacitive Loads LT1360 4mA, 50MHz, 800V/µs Op Amp Good DC Precision, Stable with All Capacitive Loads LT1361/LT1362 Dual/Quad 4mA, 50MHz, 800V/µs Op Amp Good DC Precision, Stable with All Capacitive Loads 12 Linear Technology Corporation 1357fa LT/TP 0598 REV A 2K • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com LINEAR TECHNOLOGY CORPORATION 1994