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LT1355/LT1356 Dual and Quad 12MHz, 400V/s Op Amps FEATURES s s s s s s s s s s s s s s s DESCRIPTION The LT1355/LT1356 are dual and quad low power high speed operational amplifiers with outstanding AC and DC performance. The amplifiers feature much lower supply current and higher slew rate than devices with comparable bandwidth. The circuit topology is a voltage feedback amplifier with matched high impedance inputs and the slewing performance of a current feedback amplifier. The high slew rate and single stage design provide excellent settling characteristics which make the circuit an ideal choice for data acquisition systems. Each output drives a 500 load to 12.5V with 15V supplies and a 150 load to 3V on 5V supplies. The amplifiers are stable with any capacitive load making them useful in buffer applications. The LT1355/LT1356 are members of a family of fast, high performance amplifiers using this unique topology and employing Linear Technology Corporation's advanced bipolar complementary processing. For a single amplifier version of the LT1355/LT1356 see the LT1354 data sheet. For higher bandwidth devices with higher supply currents see the LT1357 through LT1365 data sheets. Bandwidths of 25MHz, 50MHz, and 70MHz are available with 2mA, 4mA, and 6mA of supply current per amplifier. Singles, duals, and quads of each amplifier are available. C-Load is a trademark of Linear Technology Corporation 12MHz Gain-Bandwidth 400V/s Slew Rate 1.25mA Maximum Supply Current per Amplifier Unity Gain Stable C-LoadTM Op Amp Drives All Capacitive Loads 10nV/Hz Input Noise Voltage 800V Maximum Input Offset Voltage 300nA Maximum Input Bias Current 70nA Maximum Input Offset Current 12V/mV Minimum DC Gain, RL=1k 230ns Settling Time to 0.1%, 10V Step 280ns Settling Time to 0.01%, 10V Step 12.5V Minimum Output Swing into 500 3V Minimum Output Swing into 150 Specified at 2.5V, 5V, and 15V APPLICATIONS s s s s s Wideband Amplifiers Buffers Active Filters Data Acquisition Systems Photodiode Amplifiers TYPICAL APPLICATION 100kHz, 4th Order Butterworth Filter AV = -1 Large-Signal Response 6.81k 100pF 5.23k 47pF 6.81k VIN 11.3k 330pF - 1/2 LT1355 5.23k 10.2k 1000pF - 1/2 LT1355 VOUT + + 1355/1356 TA01 U U U 1355/1356 TA02 1 LT1355/LT1356 ABSOLUTE MAXIMUM RATINGS Total Supply Voltage (V+ to V -) ............................... 36V Differential Input Voltage ....................................... 10V Input Voltage ............................................................VS Output Short-Circuit Duration (Note 1) ............ Indefinite Operating Temperature Range ................ -40C to 85C Specified Temperature Range ................. -40C to 85C Maximum Junction Temperature (See Below) Plastic Package ................................................ 150C Storage Temperature Range ................. -65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C PACKAGE/ORDER INFORMATION TOP VIEW OUT A -IN A +IN A V- 1 2 A 3 4 B 6 5 -IN B +IN B 8 7 V + ORDER PART NUMBER LT1355CN8 OUT B N8 PACKAGE 8-LEAD PLASTIC DIP TJMAX = 150C, JA = 130C/ W TOP VIEW OUT A ORDER PART NUMBER 14 OUT D 13 -IN D 1 2 3 4 5 6 7 B C A D -IN A +IN A V+ +IN B -IN B OUT B LT1356CN 12 +IN D 11 V - 10 +IN C 9 8 -IN C OUT C N PACKAGE 14-LEAD PLASTIC DIP TJMAX = 150C, JA = 110C/ W Consult factory for Industrial and Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS TA = 25C, VCM = 0V unless otherwise noted. V SUPPLY 15V 5V 2.5V 2.5V to 15V 2.5V to 15V MIN TYP 0.3 0.3 0.4 20 80 10 0.6 70 160 11 3 MAX 0.8 0.8 1.0 70 300 UNITS mV mV mV nA nA nV/Hz pA/Hz M M pF IOS IB en in RIN CIN Input Offset Current Input Bias Current Input Noise Voltage Input Noise Current Input Resistance Input Resistance Input Capacitance f = 10kHz f = 10kHz VCM = 12V Differential 2 U U W WW U W TOP VIEW OUT A -IN A +IN A V- 1 2 A 3 4 B 6 5 -IN B +IN B 8 7 V+ OUT B ORDER PART NUMBER LT1355CS8 S8 PART MARKING 1355 ORDER PART NUMBER LT1356CS S8 PACKAGE 8-LEAD PLASTIC SOIC TJMAX = 150C, JA = 190C/ W TOP VIEW OUT A 1 2 3 4 5 6 7 8 B C A D 16 OUT D 15 -IN D 14 +IN D 13 V - 12 +IN C 11 -IN C 10 OUT C 9 NC -IN A +IN A V+ +IN B -IN B OUT B NC S PACKAGE 16-LEAD PLASTIC SOIC TJMAX = 150C, JA = 150C/ W 2.5V to 15V 2.5V to 15V 15V 15V 15V LT1355/LT1356 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER Input Voltage Range + TA = 25C, VCM = 0V unless otherwise noted. V SUPPLY 15V 5V 2.5V 15V 5V 2.5V MIN 12.0 2.5 0.5 TYP 13.4 3.5 1.1 -13.2 -12.0 -3.4 -2.5 -0.9 -0.5 83 78 68 92 15V 15V 5V 5V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 5V 15V 15V 5V 15V 5V 15V 5V 2.5V 15V 5V 15V 5V 15V 5V 15V 15V 5V 5V 15V 5V 15V 5V 15V 15V 15V 5V 100 9.0 7.5 12 5 12 5 1 5 13.3 12.5 3.5 3.0 1.3 25 20 30 200 70 97 84 75 106 36 15 36 15 4 20 13.8 13.0 4.0 3.3 1.7 30 25 42 400 120 6.4 6.4 12.0 10.5 9.0 14 17 20 18 16 19 230 280 240 380 2.2 2.1 3.1 3.1 0.7 113 1.0 0.9 1.25 1.20 MAX UNITS V V V V V V dB dB dB dB V/mV V/mV V/mV V/mV V/mV V/mV V V V V V mA mA mA V/s V/s MHz MHz MHz MHz MHz ns ns % % ns ns ns ns ns ns % % Deg Deg dB mA mA CONDITIONS Input Voltage Range - CMRR Common-Mode Rejection Ratio VCM = 12V VCM = 2.5V VCM = 0.5V VS = 2.5V to 15V VOUT = 12V, RL = 1k VOUT = 10V, RL = 500 VOUT = 2.5V, R L = 1k VOUT = 2.5V, R L = 500 VOUT = 2.5V, R L = 150 VOUT = 1V, RL = 500 RL = 1k, VIN = 40mV RL = 500, VIN = 40mV RL = 500, VIN = 40mV RL = 150, VIN = 40mV RL = 500, VIN = 40mV VOUT = 12.5V VOUT = 3V VOUT = 0V, VIN = 3V AV = - 2, (Note 2) 10V Peak, (Note 3) 3V Peak, (Note 3) f = 200kHz, RL = 2k 15V 5V 2.5V PSRR AVOL Power Supply Rejection Ratio Large-Signal Voltage Gain VOUT Output Swing IOUT ISC SR Output Current Short-Circuit Current Slew Rate Full Power Bandwidth GBW Gain-Bandwidth tr, tf Rise Time, Fall Time Overshoot Propagation Delay AV = 1, 10%-90%, 0.1V AV = 1, 0.1V 50% VIN to 50% VOUT, 0.1V 10V Step, 0.1%, AV = -1 10V Step, 0.01%, AV = -1 5V Step, 0.1%, AV = -1 5V Step, 0.01%, AV = -1 f = 3.58MHz, AV = 2, RL = 1k f = 3.58MHz, AV = 2, RL = 1k AV = 1, f = 100kHz VOUT = 10V, RL = 500 Each Amplifier Each Amplifier ts Settling Time Differential Gain Differential Phase RO IS Output Resistance Channel Separation Supply Current 3 LT1355/LT1356 ELECTRICAL CHARACTERISTICS SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS 0C TA 70C, VCM = 0V unless otherwise noted. V SUPPLY 15V 5V 2.5V 2.5V to 15V 2.5V to 15V 2.5V to 15V MIN q q q q q q q q q q TYP MAX 1.0 1.0 1.2 8 100 450 UNITS mV mV mV V/C nA nA dB dB dB dB V/mV V/mV V/mV V/mV V/mV V/mV V V V V V mA mA mA V/s V/s MHz MHz dB Input VOS Drift IOS IB CMRR Input Offset Current Input Bias Current Common-Mode Rejection Ratio (Note 4) 5 VCM = 12V VCM = 2.5V VCM = 0.5V VS = 2.5V to 15V VOUT = 12V, RL = 1k VOUT = 10V, RL = 500 VOUT = 2.5V, RL = 1k VOUT = 2.5V, RL = 500 VOUT = 2.5V, RL = 150 VOUT = 1V, RL = 500 RL = 1k, VIN = 40mV RL = 500, VIN = 40mV RL = 500, VIN = 40mV RL = 150, VIN = 40mV RL = 500, VIN = 40mV VOUT = 12V VOUT = 2.8V VOUT = 0V, VIN = 3V AV = - 2, (Note 2) f = 200kHz, RL = 2k VOUT = 10V, RL = 500 Each Amplifier Each Amplifier 15V 5V 2.5V 15V 15V 5V 5V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 5V 15V 15V 5V 15V 5V 15V 15V 5V 81 77 67 90 10.0 3.3 10.0 3.3 0.6 3.3 13.2 12.0 3.4 2.8 1.2 24.0 18.7 24 150 60 7.5 6.0 98 1.45 1.40 PSRR AVOL Power Supply Rejection Ratio Large-Signal Voltage Gain q q q q q q q q q q q q q q q q q q q q q VOUT Output Swing IOUT ISC SR GBW Output Current Short-Circuit Current Slew Rate Gain-Bandwidth Channel Separation IS Supply Current mA mA ELECTRICAL CHARACTERISTICS SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS -40C TA 85C, VCM = 0V unless otherwise noted. (Note 5) V SUPPLY 15V 5V 2.5V q q q q q q q q q q MIN TYP MAX 1.5 1.5 1.7 UNITS mV mV mV V/C nA nA dB dB dB dB Input VOS Drift IOS IB CMRR Input Offset Current Input Bias Current Common-Mode Rejection Ratio (Note 4) 2.5V to 15V 2.5V to 15V 2.5V to 15V 5 8 200 550 VCM = 12V VCM = 2.5V VCM = 0.5V VS = 2.5V to 15V 15V 5V 2.5V 80 76 66 90 PSRR Power Supply Rejection Ratio 4 LT1355/LT1356 ELECTRICAL CHARACTERISTICS SYMBOL AVOL PARAMETER Large-Signal Voltage Gain -40C TA 85C, VCM = 0V unless otherwise noted. (Note 5) V SUPPLY 15V 15V 5V 5V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 5V 15V 15V 5V 15V 5V 15V 15V 5V q q q q q q q q q q q q q q q q q q q q q CONDITIONS VOUT = 12V, RL = 1k VOUT = 10V, RL = 500 VOUT = 2.5V, RL = 1k VOUT = 2.5V, RL = 500 VOUT = 2.5V, RL = 150 VOUT = 1V, RL = 500 RL = 1k, VIN = 40mV RL = 500, VIN = 40mV RL = 500, VIN = 40mV RL = 150, VIN = 40mV RL = 500, VIN = 40mV VOUT = 11.5V VOUT = 2.6V VOUT = 0V, VIN = 3V AV = - 2, (Note 2) f = 200kHz, RL = 2k VOUT = 10V, RL = 500 Each Amplifier Each Amplifier MIN 7.0 1.7 7.0 1.7 0.4 1.7 13.0 11.5 3.4 2.6 1.2 23.0 17.3 23 120 50 7.0 5.5 98 TYP MAX UNITS V/mV V/mV V/mV V/mV V/mV V/mV V V V V V mA mA mA V/s V/s MHz MHz dB VOUT Output Swing IOUT ISC SR GBW Output Current Short-Circuit Current Slew Rate Gain-Bandwidth Channel Separation IS Supply Current 1.50 1.45 mA mA The q denotes specifications that apply over the full operating temperature range. Note 1: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted indefinitely. Note 2: 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 3: Full power bandwidth is calculated from the slew rate measurement: FPBW = (SR)/2VP. Note 4: This parameter is not 100% tested. Note 5: The LT1355/LT1356 are not tested and are not quality-assurance sampled at - 40C and at 85C. These specifications are guaranteed by design, correlation, and/or inference from 0C, 25C, and/or 70C tests. TYPICAL PERFORMANCE CHARACTERISTICS Supply Current vs Supply Voltage and Temperature 1.4 V+ -0.5 COMMON-MODE RANGE (V) SUPPLY CURRENT (mA) 125C 1.0 25C -1.5 -2.0 INPUT BIAS CURRENT (nA) 1.2 0.8 -55C 0.6 0.4 0 5 10 15 SUPPLY VOLTAGE (V) 20 1355/1356 G01 UW Input Common-Mode Range vs Supply Voltage 200 TA = 25C VOS < 1mV Input Bias Current vs Input Common-Mode Voltage VS = 15V TA = 25C IB+ + IB- IB = -------- 2 -1.0 150 100 2.0 1.5 1.0 0.5 V- 0 5 10 15 SUPPLY VOLTAGE (V) 20 1355/1356 G02 50 0 -50 -15 -10 -5 0 5 10 INPUT COMMON-MODE VOLTAGE (V) 15 1355/1356 G03 5 LT1355/LT1356 TYPICAL PERFORMANCE CHARACTERISTICS Input Bias Current vs Temperature 200 175 VS = 15V IB+ + IB- IB = -------- 2 INPUT VOLTAGE NOISE (nV/Hz) INPUT BIAS CURRENT (nA) 125 100 75 50 25 0 - 50 -25 0 25 50 75 TEMPERATURE (C) 100 125 OPEN-LOOP GAIN (dB) 150 Open-Loop Gain vs Temperature 97 96 95 VS = 15V RL = 1k VO = 12V OUTPUT VOLTAGE SWING (V) OUTPUT VOLTAGE SWING (V) OPEN-LOOP GAIN (dB) 94 93 92 91 90 89 88 - 50 -25 0 25 50 75 TEMPERATURE (C) 100 125 Output Short-Circuit Current vs Temperature 65 OUTPUT SHORT-CIRCUIT CURRENT (mA) 60 55 50 45 SINK 40 35 30 25 20 - 50 -25 SOURCE VS = 5V OUTPUT SWING (V) 2 0 -2 -4 10mV -6 -8 -10 1mV OUTPUT SWING (V) 0 25 50 75 TEMPERATURE (C) 6 UW 1355/1356 G04 1355/1356 G07 Input Noise Spectral Density 100 VS = 15V TA = 25C AV = 101 RS = 100k in en 1 10 INPUT CURRENT NOISE (pA/Hz) Open-Loop Gain vs Resistive Load 100 TA = 25C 90 VS = 15V VS = 5V 80 10 70 60 1 10 100 1k 10k FREQUENCY (Hz) 0.1 100k 1355/1356 G05 50 10 100 1k LOAD RESISTANCE () 10k 1355/1356 G06 Output Voltage Swing vs Supply Voltage V+ TA = 25C -1 -2 RL = 500 -3 3 2 1 V- 0 5 10 15 SUPPLY VOLTAGE (V) 20 1355/1356 G08 Output Voltage Swing vs Load Current V +-0.5 -1.0 -1.5 -2.0 -2.5 85C 2.5 2.0 1.5 1.0 V - + 0.5 -50 -40 -30 -20 -10 0 10 20 30 40 50 OUTPUT CURRENT (mA) 1355/1356 G09 RL = 1k VS = 5V VIN = 100mV -40C 85C 25C RL = 500 25C -40C RL = 1k Settling Time vs Output Step (Noninverting) 10 8 6 4 10mV VS = 15V AV = 1 10 8 6 4 2 0 -2 -4 -6 -8 -10 50 100 150 200 250 SETTLING TIME (ns) 300 350 Settling Time vs Output Step (Inverting) VS = 15V AV = -1 10mV 1mV 1mV 10mV 1mV 100 125 50 100 150 200 250 SETTLING TIME (ns) 300 350 1355/1356 G10 1355/1356 G11 1355/1356 G12 LT1355/LT1356 TYPICAL PERFORMANCE CHARACTERISTICS Output Impedance vs Frequency 1k AV = 100 VS = 15V TA = 25C VOLTAGE MAGNITUDE (dB) OUTPUT IMPEDANCE () 100 GAIN-BANDWIDTH (MHz) 10 AV = 10 1 AV = 1 0.1 0.01 10k 100k 1M 10M FREQUENCY (Hz) Gain-Bandwidth and Phase Margin vs Temperature 18 17 PHASE MARGIN VS = 15V PHASE MARGIN VS = 5V 52 50 48 5 4 3 GAIN-BANDWIDTH (MHz) 16 15 14 13 12 11 10 9 GAIN-BANDWIDTH VS = 5V -25 GAIN-BANDWIDTH VS = 15V 42 40 38 36 34 GAIN (dB) GAIN (dB) 8 - 50 0 25 50 75 TEMPERATURE (C) Gain and Phase vs Frequency 70 60 50 PHASE VS = 15V VS = 15V GAIN 30 20 10 0 -10 10k VS = 5V TA = 25C AV = -1 RF = RG = 2k 100k 1M 10M FREQUENCY (Hz) VS = 5V 120 100 80 60 40 20 0 100 COMMON-MODE REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) GAIN (dB) 40 UW 1355/1356 G13 Frequency Response vs Capacitive Load 10 8 6 4 2 0 -2 -4 -6 -8 100M 18 Gain-Bandwidth and Phase Margin vs Supply Voltage 50 48 PHASE MARGIN 46 17 VS = 15V TA = 25C AV = -1 C = 1000pF C = 500pF C = 100pF C = 50pF C=0 16 15 14 13 12 11 10 9 8 PHASE MARGIN (DEG) 44 42 40 38 GAIN-BANDWIDTH 36 34 TA = 25C 0 5 10 15 SUPPLY VOLTAGE (V) 20 1355/1356 G15 32 30 -10 100k 1M 10M FREQUENCY (Hz) 100M 1355/1356 G19 Frequency Response vs Supply Voltage (AV = 1) 5 TA = 25C AV = 1 RL = 2k 4 3 2 15V 1 0 -1 -2 2.5V -3 -4 100M 1355/1356 G17 Frequency Response vs Supply Voltage (AV = -1) TA = 25C AV = -1 RF = RG = 2k PHASE MARGIN (DEG) 46 44 2 1 0 -1 -2 -3 -4 -5 100k 5V 5V 15V 100M 1355/1356 G18 2.5V 10M 1M FREQUENCY (Hz) 100 32 125 10M 1M FREQUENCY (Hz) -5 100k 1355/1356 G16 Power Supply Rejection Ratio vs Frequency 120 VS = 15V TA = 25C 80 +PSRR - PSRR 60 100 80 60 40 20 0 Common-Mode Rejection Ratio vs Frequency VS = 15V TA = 25C PHASE (DEG) 40 20 100M 1355/1356 G14 0 100 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 1355/1356 G20 1355/1356 G21 7 LT1355/LT1356 TYPICAL PERFORMANCE CHARACTERISTICS Slew Rate vs Supply Voltage 600 500 SLEW RATE (V/s) SLEW RATE (V/s) 400 300 200 100 0 0 250 200 150 100 50 -50 AV = -2 SR+ + SR- SR = ---------- 2 SLEW RATE (V/s) TA = 25C AV = -1 RF = RG = 2k SR+ + SR- SR = ---------- 2 5 10 SUPPLY VOLTAGE (V) Total Harmonic Distortion vs Frequency 0.1 30 TA = 25C VO = 3VRMS RL = 2k 0.01 25 OUTPUT VOLTAGE (VP-P) 20 TOTAL HARMONIC DISTORTION (%) OUTPUT VOLTAGE (VP-P) AV = -1 0.001 AV = 1 0.0001 10 100 1k 10k FREQUENCY (Hz) 2nd and 3rd Harmonic Distortion vs Frequency - 20 - 30 - 40 3RD HARMONIC - 50 - 60 2ND HARMONIC -70 - 80 100k 200k VS = 15V VO = 2VP-P RL = 2k AV = 2 CROSSTALK (dB) HARMONIC DISTORTION (dB) -70 -80 -90 OVERSHOOT (%) 400k 1M 2M FREQUENCY (Hz) 8 UW 1355/1356 G22 1355/1356 G25 Slew Rate vs Temperature 350 300 VS = 15V 500 Slew Rate vs Input Level TA = 25C VS = 15V AV = -1 RF = RG = 2k SR+ + SR- SR = ---------- 2 400 300 200 VS = 5V 100 0 -25 0 25 50 75 TEMPERATURE (C) 100 125 0 2 4 6 8 10 12 14 16 18 20 INPUT LEVEL (VP-P) 1355/1356 G24 15 1355/1356 G23 Undistorted Output Swing vs Frequency (15V) 10 AV = -1 8 Undistorted Output Swing vs Frequency (5V) AV = -1 AV = 1 AV = 1 15 10 5 VS = 15V RL = 5k AV = 1, 1% MAX DISTORTION AV = -1, 4% MAX DISTORTION 1M FREQUENCY (Hz) 10M 1355/1356 G26 6 4 2 VS = 5V RL = 5k AV = 1, 2% MAX DISTORTION AV = -1, 3% MAX DISTORTION 1M FREQUENCY (Hz) 10M 1355/1356 G27 100k 0 100k 0 100k Crosstalk vs Frequency -40 -50 -60 TA = 25C VIN = 0dBm RL = 500 AV = 1 100 Capacitive Load Handling TA = 25C VS = 15V AV = 1 50 AV = -1 -100 -110 4M 10M -120 100k 1M 10M FREQUENCY (Hz) 100M 1355/1356 G29 0 10p 100p 1000p 0.01 0.1 CAPACITIVE LOAD (F) 1 1355/1356 G28 1355/1356 G30 LT1355/LT1356 TYPICAL PERFORMANCE CHARACTERISTICS Small-Signal Transient (AV = 1) Small-Signal Transient (AV = -1) Small- Signal Transient (AV = -1, CL = 1000pF) 1355/1356 G31 Large-Signal Transient (AV = 1) 1355/1356 G34 APPLICATIONS INFORMATION Layout and Passive Components The LT1355/LT1356 amplifiers are easy to use and tolerant of less than ideal layouts. For maximum performance (for example, fast 0.01% settling) use a ground plane, short lead lengths, and RF-quality bypass capacitors (0.01F to 0.1F). For high drive current applications use low ESR bypass capacitors (1F to 10F tantalum). The parallel combination of the feedback resistor and gain setting resistor on the inverting input combine with the input capacitance to form a pole which can cause peaking or oscillations. If feedback resistors greater than 5k are used, a parallel capacitor of value CF > RG x CIN/RF 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 The LT1355/LT1356 are stable with any capacitive load. 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. 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., 75) should be placed in series with the output. The other end of the cable should be terminated with the same value resistor to ground. U W UW 1355/1356 G32 1355/1356 G33 Large-Signal Transient (AV = -1) Large-Signal Transient (AV = 1, CL = 10,000pF) 1355/1356 G35 1355/1356 G36 U U 9 LT1355/LT1356 APPLICATIONS INFORMATION Input Considerations Each of the LT1355/LT1356 amplifier inputs is the base of an NPN and 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 current can be positive or negative. The offset current does not depend on 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 differential input voltages of up to 10V without damage and need no clamping or source resistance for protection. Circuit Operation The LT1355/LT1356 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 an 800 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 10 times greater input step. The curve of Slew Rate vs Input Level illustrates this relationship. The LT1355/ LT1356 are 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 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. Power Dissipation The LT1355/LT1356 combine high speed and large output drive in small packages. 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: LT1355CN8: LT1355CS8: LT1356CN: LT1356CS: TJ = TA + (PD x 130C/W) TJ = TA + (PD x 190C/W) TJ = TA + (PD x 110C/W) TJ = TA + (PD x 150C/W) 10 U W U U 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). For each amplifier PDMAX is: PDMAX = (V+ - V-)(ISMAX) + (V+/2)2/RL Example: LT1356 in S16 at 70C, VS = 15V, RL = 1k PDMAX = (30V)(1.45mA) + (7.5V)2/1kW = 99.8mW TJMAX = 70C + (4 x 99.8mW)(150C/W) = 130C LT1355/LT1356 TYPICAL APPLICATIONS Instrumentation Amplifier R5 432 R1 20k R2 2k R4 20k VIN VIN R1 2.87k R2 26.7k SI PLIFIED SCHE ATIC V+ -IN C CC V- 1355/1356 SS01 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. U - 1/2 LT1355 R3 2k - 1/2 LT1355 VOUT - + + + R4 R3 1 R2 R3 R2 + R3 1 + + + R5 = 104 2 R1 R4 TRIM R5 FOR GAIN TRIM R1 FOR COMMON-MODE REJECTION BW = 120kHz AV = 1355/1356 TA03 100kHz, 4th Order Butterworth Filter (Sallen-Key) C2 330pF C4 1000pF - - 1/2 LT1355 1/2 LT1355 VOUT + R3 2.43k R4 15.4k C3 68pF 1355/1356 TA04 + C1 100pF W W R1 800 +IN RC OUT 11 LT1355/LT1356 PACKAGE DESCRIPTION 0.300 - 0.320 (7.620 - 8.128) 0.009 - 0.015 (0.229 - 0.381) ( +0.025 0.325 -0.015 +0.635 8.255 -0.381 ) 0.045 0.015 (1.143 0.381) 0.100 0.010 (2.540 0.254) 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP 0.016 - 0.050 0.406 - 1.270 *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 0.300 - 0.325 (7.620 - 8.255) 0.130 0.005 (3.302 0.127) 0.015 (0.380) MIN 0.009 - 0.015 (0.229 - 0.381) +0.025 0.325 -0.015 +0.635 8.255 -0.381 ( ) 0.125 (3.175) MIN 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0.053 - 0.069 (1.346 - 1.752) 0 - 8 TYP 0.016 - 0.050 0.406 - 1.270 0.014 - 0.019 (0.355 - 0.483) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006 INCH (0.15mm). 12 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U Dimension in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.045 - 0.065 (1.143 - 1.651) 0.130 0.005 (3.302 0.127) 0.400 (10.160) MAX 8 7 6 5 0.065 (1.651) TYP 0.125 (3.175) MIN 0.020 (0.508) MIN 1 2 3 0.250 0.010 (6.350 0.254) 0.018 0.003 (0.457 0.076) 4 N8 0392 S8 Package 8-Lead Plastic SOIC 0.189 - 0.197 (4.801 - 5.004) 0.053 - 0.069 (1.346 - 1.752) 0.004 - 0.010 (0.101 - 0.254) 8 7 6 5 0.014 - 0.019 (0.355 - 0.483) 0.050 (1.270) BSC 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157 (3.810 - 3.988) 1 2 3 4 SO8 0294 N Package 14-Lead Plastic DIP 0.045 - 0.065 (1.143 - 1.651) 0.770 (19.558) MAX 14 0.065 (1.651) TYP 0.075 0.015 (1.905 0.381) 0.100 0.010 (2.540 0.254) 0.018 0.003 (0.457 0.076) 13 12 11 10 9 8 0.260 0.010 (6.604 0.254) 1 2 3 4 5 6 7 N14 0392 S Package 16-Lead Plastic SOIC 0.386 - 0.394* (9.804 - 10.008) 0.004 - 0.010 (0.101 - 0.254) 16 15 14 13 12 11 10 9 0.050 (1.270) TYP 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157* (3.810 - 3.988) 1 2 3 4 5 6 7 8 LT/GP 0494 10K * PRINTED IN USA (c) LINEAR TECHNOLOGY CORPORATION 1994 |
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