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LT1361/LT1362 Dual and Quad 50MHz, 800V/s Op Amps
FEATURES
s s s s s s s s s s s s s s s s
DESCRIPTION
The LT1361/LT1362 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 13V with 15V supplies and a 150 load to 3.2V on 5V supplies. The amplifiers are stable with any capacitive load making them useful in buffer or cable driving applications. The LT1361/LT1362 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 LT1361/LT1362 see the LT1360 data sheet. For higher bandwidth devices with higher supply currents see the LT1363 through LT1365 data sheets. For lower supply current amplifiers see the LT1354 to LT1359 data sheets. Singles, duals, and quads of each amplifier are available.
C-Load is a trademark of Linear Technology Corporation
50MHz Gain-Bandwidth 800V/s Slew Rate 5mA Maximum Supply Current per Amplifier Unity-Gain Stable C-LoadTM Op Amp Drives All Capacitive Loads 9nV/Hz Input Noise Voltage 1mV Maximum Input Offset Voltage 1A Maximum Input Bias Current 250nA Maximum Input Offset Current 13V Minimum Output Swing into 500 3.2V Minimum Output Swing into 150 4.5V/mV Minimum DC Gain, RL=1k 60ns Settling Time to 0.1%, 10V Step 0.2% Differential Gain, AV=2, RL=150 0.3 Differential Phase, AV=2, RL=150 Specified at 2.5V, 5V, and 15V
APPLICATIONS
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Wideband Amplifiers Buffers Active Filters Video and RF Amplification Cable Drivers Data Acquisition Systems
TYPICAL APPLICATION
Cable Driver Frequency Response
2
AV = -1 Large-Signal Response
0
GAIN (dB)
-2
IN
VS = 15V VS = 10V VS = 2.5V VS = 5V
+ 1/2 LT1361 - 510
510 OUT 75
-4
75
-6
-8 1 10 FREQUENCY (MHz) 100
1361/1362 TA02
1361/1362 TA01
U
U
U
1
LT1361/LT1362
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 LT1361CN8
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
LT1362CN
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 (Note 2)
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 80 0.3 9 0.9 20 50 5 3 MAX 1.0 1.0 1.2 250 1.0 UNITS mV mV mV nA A 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 LT1361CS8 S8 PART MARKING 1361 ORDER PART NUMBER LT1362CS
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
LT1361/LT1362
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 3.4 1.1 -13.2 -3.2 -0.9 86 79 68 93 15V 15V 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 15V 5V 15V 5V 15V 5V 15V 5V 15V 15V 15V 5V 100 35 25 4.5 3.0 3.0 1.5 2.5 13.5 13.0 3.5 3.2 1.3 26 21 40 600 250 92 84 74 105 9.0 6.5 6.4 4.2 5.2 13.9 13.6 4.0 3.8 1.7 34 29 54 800 350 12.7 18.6 50 37 32 3.1 4.3 35 27 5.2 6.4 60 90 65 0.20 0.20 0.04 0.02 0.40 0.30 0.07 0.26 1.4 113 4.0 3.8 5.0 4.8 -12.0 -2.5 -0.5 MAX UNITS V V V V V V dB dB dB dB 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 % % % % Deg Deg 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, 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 = 13V VOUT = 3.2V VOUT = 0V, VIN = 3V AV = - 2, (Note 3) 10V Peak, (Note 4) 3V Peak, (Note 4) f = 200kHz
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 f = 3.58MHz, AV = 2, RL = 150 f = 3.58MHz, AV = 2, RL = 1k
ts
Settling Time
Differential Gain
Differential Phase
f = 3.58MHz, AV = 2, RL = 150 f = 3.58MHz, AV = 2, RL = 1k
RO IS
Output Resistance Channel Separation Supply Current
AV = 1, f = 1MHz VOUT = 10V, RL = 500 Each Amplifier Each Amplifier
3
LT1361/LT1362
ELECTRICAL CHARACTERISTICS
SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS (Note 2)
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
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 A dB dB dB dB 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 5)
9
12 350 1.5
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 = 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 = 12.8V VOUT = 3.1V VOUT = 0V, VIN = 3V AV = - 2, (Note 3) f = 200kHz VOUT = 10V, RL = 500 Each Amplifier Each Amplifier
15V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 5V 15V 15V 5V 15V 5V 15V 15V 5V
84 77 66 91 3.6 2.4 2.4 1.0 2.0 13.4 12.8 3.4 3.1 1.2 25 20 32 475 185 31 22 98 5.8 5.6
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
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 (Note 2)
-40C TA 85C, VCM = 0V unless otherwise noted. (Note 6)
V SUPPLY 15V 5V 2.5V 2.5V to 15V 2.5V to 15V 2.5V to 15V
q q q q q q q q q q
MIN
TYP
MAX 2.0 2.0 2.2
UNITS mV mV mV V/C nA A dB dB dB dB
Input VOS Drift IOS IB CMRR Input Offset Current Input Bias Current Common-Mode Rejection Ratio
(Note 5)
9
12 400 1.8
VCM = 12V VCM = 2.5V VCM = 0.5V VS = 2.5V to 15V
15V 5V 2.5V
84 77 66 90
PSRR
Power Supply Rejection Ratio
4
LT1361/LT1362
ELECTRICAL CHARACTERISTICS
SYMBOL AVOL PARAMETER Large-Signal Voltage Gain
-40C TA 85C, VCM = 0V unless otherwise noted. (Note 6)
V SUPPLY 15V 15V 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
CONDITIONS VOUT = 12V, RL = 1k VOUT = 10V, RL = 500 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 = 12.0V VOUT = 3.0V VOUT = 0V, VIN = 3V AV = - 2, (Note 3) f = 200kHz VOUT = 10V, RL = 500 Each Amplifier Each Amplifier
MIN 2.5 1.5 1.5 0.6 1.3 13.4 12.0 3.4 3.0 1.2 24 20 30 450 175 30 20 98
TYP
MAX
UNITS 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
6.0 5.8
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: Input offset voltage is pulse tested and is exclusive of warm-up drift. 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/2VP. Note 5: This parameter is not 100% tested. Note 6: The LT1361/LT1362 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
6
V+ -0.5
COMMON-MODE RANGE (V)
125C 4 25C
-1.5 -2.0
INPUT BIAS CURRENT (A)
5
SUPPLY CURRENT (mA)
3 -55C 2
1 0 5 10 15 SUPPLY VOLTAGE (V) 20
1361/1362 G01
UW
Input Common-Mode Range vs Supply Voltage
0.6
TA = 25C VOS < 1mV
Input Bias Current vs Input Common-Mode Voltage
VS = 15V TA = 25C IB+ + IB- IB = -------- 2
-1.0
0.5 0.4 0.3 0.2 0.1 0 -15
2.0 1.5 1.0 0.5 V- 0 5 10 15 SUPPLY VOLTAGE (V) 20
1361/1362 G02
-10 -5 0 5 10 INPUT COMMON-MODE VOLTAGE (V)
15
1361/1362 G03
5
LT1361/LT1362 TYPICAL PERFORMANCE CHARACTERISTICS
Input Bias Current vs Temperature
0.7 0.6 VS = 15V IB+ + IB- IB = -------- 2 100
INPUT VOLTAGE NOISE (nV/Hz)
INPUT BIAS CURRENT (A)
0.5 0.4 0.3 0.2 0.1 0 - 50
OPEN-LOOP GAIN (dB)
-25
0 25 50 75 TEMPERATURE (C)
Open-Loop Gain vs Temperature
81 80 79 VS = 15V VO = 12V RL = 1k
V+ -1
OUTPUT VOLTAGE SWING (V)
OUTPUT VOLTAGE SWING (V)
OPEN-LOOP GAIN (dB)
78 77 76 75 74 73 72 - 50 -25 0 25 50 75 TEMPERATURE (C) 100 125
Output Short-Circuit Current vs Temperature
70
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 5V
65 60 55 SOURCE 50 SINK 45 40 35 - 50
OUTPUT STEP (V)
2 0 -2 -4 10mV -6 -8 -10 1mV
OUTPUT STEP (V)
-25
0 25 50 75 TEMPERATURE (C)
6
UW
100
1361/1362 G04 1361/1362 G07
Input Noise Spectral Density
10 VS = 15V TA = 25C AV = 101 RS = 100k in en 1
Open-Loop Gain vs Resistive Load
85 TA = 25C
INPUT CURRENT NOISE (pA/Hz)
VS = 15V
80 VS = 5V
75
10
70
65
1 125 10 100 1k 10k FREQUENCY (Hz)
0.1 100k
1361/1362 G05
60 10 1k 100 LOAD RESISTANCE () 10k
1361/1362 G06
Output Voltage Swing vs Supply Voltage
V+
Output Voltage Swing vs Load Current
RL = 1k
- 0.5 -1.0 -1.5 -2.0 - 40C VS = 5V VIN = 100mV 85C 25C
TA = 25C
-2 -3 3 2 1 V- 0
RL = 500
2.0 1.5 1.0 25C
- 40C
RL = 500 RL = 1k
5 10 15 SUPPLY VOLTAGE (V)
20
1361/1362 G08
85C 0.5 V- - 50 - 40 -30 -20 -10 0 10 20 30 40 50 OUTPUT CURRENT (mA)
1361/1362 G09
Settling Time vs Output Step (Noninverting)
10 8 6 4 VS = 15V AV = 1 RL = 1k 10mV 1mV 10 8 6 4 2 0 -2 -4
Settling Time vs Output Step (Inverting)
VS = 15V AV = -1 RF = 1k CF = 3pF
10mV 1mV
10mV -6 -8 -10 100 0 20 1mV
100
125
0
20
40 60 80 SETTLING TIME (ns)
40 60 80 SETTLING TIME (ns)
100
1361/1362 G10
1361/1362 G11
1361/1362 G12
LT1361/LT1362 TYPICAL PERFORMANCE CHARACTERISTICS
Output Impedance vs Frequency
100 AV = 10 70 60 50 GAIN AV = 1 1 PHASE VS = 15V VS = 15V VS = 5V VS = 5V
OUTPUT IMPEDANCE ()
10
AV = 100
GAIN (dB)
40 30 20 10
60 40 20 0 TA = 25C AV = -1 RF = RG = 1k 100k 1M 10M FREQUENCY (Hz) 100M
1361/1362 G14
CROSSTALK (dB)
0.1 VS = 15V TA = 25C 0.01 10k 100k 1M 10M FREQUENCY (Hz) 100M
1361/1362 G13
Gain-Bandwidth and Phase Margin vs Temperature
80 PHASE MARGIN VS = 5V PHASE MARGIN VS = 15V 60 GAIN-BANDWIDTH VS = 15V GAIN-BANDWIDTH VS = 5V 50 45 40 5 4 3
VOLTAGE MAGNITUDE (dB)
GAIN-BANDWIDTH (MHz)
70
GAIN (dB)
50
40
30 - 50
-25
0 25 50 75 TEMPERATURE (C)
Gain-Bandwidth and Phase Margin vs Supply Voltage
80 TA = 25C 70 50 48 46 100
COMMON-MODE REJECTION RATIO (dB)
POWER SUPPLY REJECTION RATIO (dB)
GAIN-BANDWIDTH (MHz)
PHASE MARGIN
60
50
40
GAIN-BANDWIDTH
30 0 5 10 15 SUPPLY VOLTAGE (V) 20
1361/1362 G15
UW
100
1361/1362 G16
Gain and Phase vs Frequency
120 100 -20 -30 -40 -50 -60 -70 -80 -90
Crosstalk vs Frequency
TA = 25C AV = 1 VIN = 0dBm
PHASE (DEG)
80
VS = 15V RL = 1k VS = 5V RL = 500
-100 -110 -120 100k
0 -10 10k
10M 1M FREQUENCY (Hz)
100M
1361/1362 G21
Frequency Response vs Supply Voltage (AV = 1)
12 TA = 25C AV = 1 RL = 1k 15V 10 8 6 4 2 0 -2 -4 -6 100M
1361/1362 G17
Frequency Response vs Capacitive Load
VS = 15V TA = 25C AV = -1 C = 1000pF C = 500pF C = 100pF C = 50pF C=0
PHASE MARGIN (DEG)
35 30 25 20 15 10 5 0 125
2 1 0 -1 -2 -3 -4 -5 100k 10M 1M FREQUENCY (Hz) 2.5V 5V
-8 1M
10M FREQUENCY (Hz)
100M
1361/1362 G18
Power Supply Rejection Ratio vs Frequency
120
+PSRR 80 - PSRR VS = 15V TA = 25C
Common-Mode Rejection Ratio vs Frequency
VS = 15V TA = 25C
100 80 60 40 20 0
PHASE MARGIN (DEG)
44 42 40 38 36 34 32 30
60
40
20
0 100
1k
10k 100k 1M FREQUENCY (Hz)
10M
100M
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
1361/1362 G19
1361/1362 G20
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LT1361/LT1362 TYPICAL PERFORMANCE CHARACTERISTICS
Slew Rate vs Supply Voltage
2000 1800 1600
SLEW RATE (V/s)
SLEW RATE (V/s)
1200 1000 800 600 400 200 0 0 5 10 SUPPLY VOLTAGE (V) 15
1361/1362 G22
700 600 500 400 300 200 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 VS = 5V VS = 15V
SLEW RATE (V/s)
1400
TA = 25C AV = -1 RF = RG = 1k SR+ + SR - SR = ---------- 2
Total Harmonic Distortion vs Frequency
0.01 30 TA = 25C VO = 3VRMS RL = 500
TOTAL HARMONIC DISTORTION (%)
OUTPUT VOLTAGE (VP-P)
20 15 10 5 VS = 15V RL = 1k AV = 1, 1% MAX DISTORTION AV = -1, 2% MAX DISTORTION 1M FREQUENCY (Hz) 10M
1361/1362 G26
OUTPUT VOLTAGE (VP-P)
0.001
AV = -1 AV = 1
0.0001 10
100
1k 10k FREQUENCY (Hz)
2nd and 3rd Harmonic Distortion vs Frequency
-30 -40 -50
DIFFERENTIAL PHASE (DEG)
HARMONIC DISTORTION (dB)
VS = 15V VO = 2VP-P RL = 500 AV = 2
3RD HARMONIC
0.40
OVERSHOOT (%)
-60 -70 2ND HARMONIC -80 -90 100k 200k
400k 1M 2M FREQUENCY (Hz)
8
UW
1361/1362 G25
Slew Rate vs Temperature
1000 AV = -2 900 800 SR + + SR - SR = ---------- 2 2000 1800 1600 1400 1200 1000 800 600 400 200 0
Slew Rate vs Input Level
TA = 25C VS = 15V AV = -1 RF = RG = 1k SR + + SR - SR = ---------- 2
0
2
4
6 8 10 12 14 16 18 20 INPUT LEVEL (VP-P)
1361/1362 G24
1361/1362 G23
Undistorted Output Swing vs Frequency (15V)
10 AV = -1 25 8
Undistorted Output Swing vs Frequency (5V)
AV = -1
6
AV = 1
AV = 1
4
2
VS = 5V RL = 1k 2% MAX DISTORTION 1M FREQUENCY (Hz) 10M
1361/1362 G27
100k
0 100k
0 100k
Differential Gain and Phase vs Supply Voltage
0.50
Capacitive Load Handling
100 TA = 25C VS = 15V
DIFFERENTIAL GAIN (%)
0.25 DIFFERENTIAL GAIN 0
AV = -1 50
0.36 DIFFERENTIAL PHASE 0.32 AV = 2 RL = 150 TA = 25C 5 10 SUPPLY VOLTAGE (V) 15
1361/1362 G29
AV = 1 0 10p
0.28
4M
10M
100p
1000p 0.01 0.1 CAPACITIVE LOAD (F)
1
1361/1362 G28
1361/1362 G30
LT1361/LT1362 TYPICAL PERFORMANCE CHARACTERISTICS
Small-Signal Transient (AV = 1) Small-Signal Transient (AV = -1) Small-Signal Transient (AV = -1, CL = 500pF)
1361/1362 TA31
Large-Signal Transient (AV = 1)
1361/1362 TA34
APPLICATIONS INFORMATION
Layout and Passive Components The LT1361/LT1362 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. Input Considerations Each of the LT1361/LT1362 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.
U
W
UW
1361/1362 TA32
1361/1362 TA33
Large-Signal Transient (AV = -1)
Large-Signal Transient (AV = 1, CL = 10,000pF)
1361/1362 TA35
1361/1362 TA36
U
U
9
LT1361/LT1362
APPLICATIONS INFORMATION
Capacitive Loading The LT1361/LT1362 are 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 500pF load shows 60% peaking. The large signal response shows the output slew rate being limited to 5V/s 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., 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. Circuit Operation The LT1361/LT1362 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 500 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 LT1361/LT1362 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 LT1361/LT1362 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: LT1361CN8: LT1361CS8: LT1362CN: LT1362CS: 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: LT1362 in S16 at 70C, VS = 5V, RL = 100 PDMAX = (10V)(5.6mA) + (2.5V)2/100 = 119mW TJMAX = 70C + (4 x 119mW)(150C/W) = 141C
LT1361/LT1362
TYPICAL APPLICATIONS
Two Op Amp Instrumentation Amplifier
R5 220 R1 10k R2 1k R4 10k
VIN
909 VIN
SI PLIFIED SCHE ATIC
V+
-IN C
V-
1361/1362 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 LT1361
R3 1k
-
1/2 LT1361 VOUT
- +
+
+
R4 1 R2 R3 R2 + R3 + GAIN = 1 + + R5 R3 2 R1 R4 TRIM R5 FOR GAIN TRIM R1 FOR COMMON-MODE REJECTION BW = 500kHz
(
) = 102

1361/1362 TA03
1MHz, 4th Order Butterworth Filter
909 47pF 22pF 2.67k 220pF 1.1k
-
1/2 LT1361
1.1k
2.21k 470pF
-
1/2 LT1361 VOUT
+
+
1361/1362 TA04
W
W
R1 500
+IN
RC
CC OUT
11
LT1361/LT1362
PACKAGE DESCRIPTION
0.300 - 0.320 (7.620 - 8.128)
0.009 - 0.015 (0.229 - 0.381)
0.065 (1.651) TYP 0.125 (3.175) MIN 0.020 (0.508) MIN
(
+0.025 0.325 -0.015 8.255 +0.635 -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 8.255 +0.635 -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
0.250 0.010 (6.350 0.254)
1
2
3
4
0.018 0.003 (0.457 0.076)
S8 Package 8-Lead Plastic SOIC
0.189 - 0.197* (4.801 - 5.004) 0.053 - 0.069 (1.346 - 1.752) 8 0.004 - 0.010 (0.101 - 0.254) 0.228 - 0.244 (5.791 - 6.197) 0.150 - 0.157* (3.810 - 3.988) 7 6 5
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) BSC
1
2
3
4
N Package 14-Lead Plastic DIP
0.045 - 0.065 (1.143 - 1.651) 0.770 (19.558) MAX 14 13 12 11 10 9 8
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)
0.260 0.010 (6.604 0.254)
1
2
3
4
5
6
7
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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