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LT1360 50MHz, 800V/s Op Amp
FEATURES
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DESCRIPTION
The LT1360 is a high speed, very high slew rate operational amplifier with excellent DC performance. The LT1360 features reduced 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 500 load to 13V with 15V supplies and a 150 load to 3.2V on 5V supplies. The amplifier is also capable of driving any capacitive load which makes it useful in buffer or cable driver applications. The LT1360 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 LT1360 see the LT1361/1362 data sheet. For 70MHz amplifiers with 6mA of supply current per amplifier see the LT1363 and LT1364/1365 data sheets. For lower supply current amplifiers with bandwidths of 12MHz and 25MHz see the LT1354 through 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 9nV/Hz Input Noise Voltage Unity Gain Stable C-LoadTM Op Amp Drives All Capacitive Loads 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
Two Op Amp Instrumentation Amplifier
R5 220 R1 10k R2 1k R4 10k
AV = -1 Large-Signal Response
-
LT1360
R3 1k
-
LT1360 VOUT
-
VIN
+ +
+
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

1360 TA02
1360 TA01
U
U
U
1
LT1360
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 NULL -IN +IN V- 1 2 3 4 8 7 6 5 NULL V+ VOUT NC
ORDER PART NUMBER LT1360CN8
N8 PACKAGE, 8-LEAD PLASTIC DIP
TJMAX = 150C, JA = 130C/ 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.
VSUPPLY 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 12.0 2.5 0.5 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 4.5 3.0 3.0 1.5 2.5 13.5 13.0 3.5 3.2 1.3 92 84 74 105 9.0 6.5 6.4 4.2 5.2 13.9 13.6 4.0 3.8 1.7 -12.0 -2.5 -0.5 MAX 1.0 1.0 1.2 250 1.0 UNITS mV mV mV nA A nV/Hz pA/Hz M M pF 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
IOS IB en in RIN CIN
Input Offset Current Input Bias Current Input Noise Voltage Input Noise Current Input Resistance Input Resistance Input Capacitance Input Voltage Range + f = 10kHz f = 10kHz VCM = 12V Differential
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
PSRR AVOL
Power Supply Rejection Ratio Large-Signal Voltage Gain
VOUT
Output Swing
2
U
U
W
WW U
W
TOP VIEW NULL -IN +IN V- 1 2 3 4 8 7 6 5 NULL V+ VOUT NC
ORDER PART NUMBER LT1360CS8 S8 PART MARKING 1360
S8 PACKAGE, 8-LEAD PLASTIC SOIC
TJMAX = 150C, JA = 190C/ W
2.5V to 15V 2.5V to 15V 15V 15V 15V 15V 5V 2.5V 15V 5V 2.5V 15V 5V 2.5V
LT1360
ELECTRICAL CHARACTERISTICS
SYMBOL IOUT ISC SR PARAMETER Output Current Short-Circuit Current Slew Rate Full Power Bandwidth GBW Gain-Bandwidth CONDITIONS VOUT = 13V VOUT = 3.2V VOUT = 0V, V IN = 3V AV = -2, (Note 3) 10V Peak, (Note 4) 3V Peak, (Note 4) f = 1MHz
TA = 25C, VCM = 0V unless otherwise noted.
VSUPPLY 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 5V MIN 26 21 40 600 250 TYP 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 4.0 3.8 5.0 4.8 MAX UNITS mA mA mA V/s V/s MHz MHz MHz MHz MHz ns ns % % ns ns ns ns ns % % % % Deg Deg Deg Deg mA mA
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 Supply Current
AV = 1, f = 1MHz
ELECTRICAL CHARACTERISTICS
SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS (Note 2)
0C TA 70C, VCM = 0V unless otherwise noted.
VSUPPLY 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
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
15V 5V 2.5V 15V 15V 5V 5V 2.5V
84 77 66 91 3.6 2.4 2.4 1.0 2.0
PSRR AVOL
Power Supply Rejection Ratio Large-Signal Voltage Gain
q q q q q
3
LT1360
ELECTRICAL CHARACTERISTICS
SYMBOL VOUT PARAMETER Output Swing CONDITIONS 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, V IN = 3V AV = -2, (Note 3)
0C TA 70C, VCM = 0V unless otherwise noted.
VSUPPLY 15V 15V 5V 5V 2.5V 15V 5V 15V 15V 5V 15V 5V
q q q q q q q q q q q q
MIN 13.4 12.8 3.4 3.1 1.2 25 20 32 475 185
TYP
MAX
UNITS V V V V V mA mA mA V/s V/s
IOUT ISC SR IS
Output Current Short-Circuit Current Slew Rate Supply Current
5.8 5.6
mA mA
ELECTRICAL CHARACTERISTICS
SYMBOL VOS PARAMETER Input Offset Voltage CONDITIONS (Note 2)
-40C TA 85C, VCM = 0V unless otherwise noted. (Note 6)
VSUPPLY 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 V/mV V/mV V/mV V/mV V/mV V V V V V mA mA mA V/s V/s
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 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, V IN = 3V AV = -2, (Note 3)
15V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 15V 5V 5V 2.5V 15V 5V 15V 15V 5V 15V 5V
84 77 66 90 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 6.0 5.8
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
VOUT
Output Swing
IOUT ISC SR IS
Output Current Short-Circuit Current Slew Rate Supply Current
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 2V 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 LT1360 is not tested and is 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.
4
LT1360
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
1360 G01
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 RL = 1k VO = 12V VS = 15V
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
UW
100
1360 G04 1360 G07
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
1360 G02
-10 -5 0 5 10 INPUT COMMON-MODE VOLTAGE (V)
15
1360 G03
Input Noise Spectral Density
10 VS = 15V TA = 25C AV = 101 RS = 100k in en 1 85
Open-Loop Gain vs Resistive Load
TA = 25C VS = 15V
INPUT CURRENT NOISE (pA/Hz)
80 VS = 5V
75
10
70
65
1 125 10 100 1k 10k FREQUENCY (Hz)
0.1 100k
1360 G05
60 10 100 1k LOAD RESISTANCE () 10k
1360 G06
Output Voltage Swing vs Supply Voltage
V+ TA = 25C -1 -2 -3 3 2 1 V- 0 5 10 15 SUPPLY VOLTAGE (V) 20
1360 G08
Output Voltage Swing vs Load Current
V+
RL = 1k RL = 500
-0.5 -1.0 -1.5 -2.0
VS = 5V VIN = 100mV
85C 25C -40C
2.0 1.5 1.0 25C
-40C
RL = 500 RL = 1k
85C 0.5 V- -50 -40 -30 -20 -10 0 10 20 30 40 50 OUTPUT CURRENT (mA)
1360 G09
5
LT1360
TYPICAL PERFORMANCE CHARACTERISTICS
Output Short-Circuit Current vs Temperature
70
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 5V
65
OUTPUT IMPEDANCE ()
60 55 SOURCE 50 SINK 45 40 35 -50
GAIN (dB)
-25
0 25 50 75 TEMPERATURE (C)
Settling Time vs Output Step (Noninverting)
10 8 6
OUTPUT STEP (V)
VS = 15V AV = 1 RL = 1k
10mV 1mV
GAIN-BANDWIDTH (MHz)
OUTPUT STEP (V)
4 2 0 -2 -4 10mV -6 -8 -10 0 20 40 60 80 SETTLING TIME (ns) 100
1360 G12
1mV
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 PHASE MARGIN (DEG) 35 30 25 20 15 10 5 30 -50 -25 0 25 50 75 TEMPERATURE (C) 100 0 125 5 4 3 2
GAIN-BANDWIDTH (MHz)
70
GAIN (dB)
0 -1 -2 -3 -4 -5 100k 10M 1M FREQUENCY (Hz) 2.5V 100M
1360 G17
GAIN (dB)
50
40
6
UW
100
1360 G10 1360 G16
Output Impedance vs Frequency
100 AV = 10 70 60 10 AV = 100 50
Gain and Phase vs Frequency
120 PHASE VS = 15V GAIN 40 30 20 10 VS = 15V TA = 25C 0 -10 10k TA = 25C AV = -1 RF = RG = 1k 100k 1M 10M FREQUENCY (Hz) VS = 5V VS = 5V VS = 15V 100
PHASE (DEG)
80 60 40 20 0
AV = 1 1
0.1
125
0.01 10k
100k
1M 10M FREQUENCY (Hz)
100M
1360 G11
100M
1360 G14
Settling Time vs Output Step (Inverting)
10 8 6 4 2 0 -2 -4 10mV -6 -8 -10 0 20 40 60 80 SETTLING TIME (ns) 100
1360 G13
Gain-Bandwidth and Phase Margin vs Supply Voltage
80 50 TA = 25C 70 PHASE MARGIN 48 46
VS = 15V AV = -1 RF = 1k CF = 3pF
10mV 1mV
PHASE MARGIN (DEG)
44 60 42 40 50 38 36 40 GAIN-BANDWIDTH 34 32 30 0 5 10 15 SUPPLY VOLTAGE (V) 20
1360 G15
1mV
30
Frequency Response vs Supply Voltage (AV = 1)
5 TA = 25C AV = 1 RL = 1k 15V 4 3 2 1 0 -1 -2 -3 -4
Frequency Response vs Supply Voltage (AV = -1)
TA = 25C AV = -1 RF = RG = 1k 15V 5V
1
5V
2.5V
-5 100k
10M 1M FREQUENCY (Hz)
100M
1360 G18
LT1360
TYPICAL PERFORMANCE CHARACTERISTICS
Frequency Response vs Capacitive Load
12 10
POWER SUPPLY REJECTION RATIO (dB)
COMMON-MODE REJECTION RATIO (dB)
VOLTAGE MAGNITUDE (dB)
8 6 4 2 0 -2 -4 -6 -8 1M
VS = 15V TA = 25C AV = -1
C = 1000pF C = 500pF C = 100pF C = 50pF C=0
10M FREQUENCY (Hz)
Slew Rate vs Supply Voltage
2000 1800 1600 TA = 25C AV = -1 RF = RG = 1k SR+ + SR - SR = ---------- 2 1000 900 800
SLEW RATE (V/s)
SLEW RATE (V/s)
1200 1000 800 600 400 200 0 0 5 10 SUPPLY VOLTAGE (V) 15
1360 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
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
1360 G26
OUTPUT VOLTAGE (VP-P)
0.001
AV = -1 AV = 1
0.0001 10
100
1k 10k FREQUENCY (Hz)
UW
1360 G19 1360 G25
Power Supply Rejection Ratio vs Frequency
100 +PSRR 80 -PSRR VS = 15V TA = 25C 120 100 80 60 40 20 0 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M
1360 G20
Common-Mode Rejection Ratio vs Frequency
VS = 15V TA = 25C
60
40
20
100M
0 100
1k
10k
100k 1M FREQUENCY (Hz)
10M
100M
1360 G21
Slew Rate vs Temperature
2000 AV = -2 SR + + SR - SR = ---------- 2 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)
1360 G24
1360 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
1360 G27
100k
0 100k
0 100k
7
LT1360
TYPICAL PERFORMANCE CHARACTERISTICS
2nd and 3rd Harmonic Distortion vs Frequency
-30 -40 -50 VS = 15V VO = 2VP-P RL = 500 AV = 2
HARMONIC DISTORTION (dB)
3RD HARMONIC
OVERSHOOT (%)
DIFFERENTIAL PHASE (DEG)
-60 -70 2ND HARMONIC -80 -90 100k 200k
400k 1M 2M FREQUENCY (Hz)
Small-Signal Transient (AV = 1)
Large-Signal Transient (AV = 1)
8
UW
4M
1360 G28 1360 TA31 1360 TA34
Differential Gain and Phase vs Supply Voltage
0.50
Capacitive Load Handling
100 VS = 15V TA = 25C AV = -1 50
DIFFERENTIAL GAIN (%)
0.25 DIFFERENTIAL GAIN 0.40 0
0.36 DIFFERENTIAL PHASE 0.32 AV = 2 RL = 150 TA = 25C 5 10 SUPPLY VOLTAGE (V) 15
1360 G29
AV = 1 0 10p
10M
0.28
100p
1000p 0.01 0.1 CAPACITIVE LOAD (F)
1
1360 G30
Small-Signal Transient (AV = -1)
Small-Signal Transient (AV = -1, CL = 500pF)
1360 TA32
1360 TA33
Large-Signal Transient (AV = -1)
Large-Signal Transient (AV = 1, CL = 10,000pF)
1360 TA35
1360 TA36
LT1360
APPLICATIONS INFORMATION
The LT1360 may be inserted directly into AD817, AD847, EL2020, EL2044, and LM6361 applications improving both DC and AC performance, provided that the nulling circuitry is removed. The suggested nulling circuit for the LT1360 is shown below.
Offset Nulling
V+ 3
+ -
1 10k
7 LT1360 6 4 8
2
V-
1360 AI01
Layout and Passive Components The LT1360 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 (0.01F to 0.1F). For high drive current applications use low ESR bypass capacitors (1F to 10F 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 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 5k, 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.
2
GAIN (dB)
U
W
U
U
Capacitive Loading The LT1360 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 smallsignal response with 500pF load shows 60% peaking. The large-signal response with a 10,000pF load 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.
Cable Driver Frequency Response
AV = 2 RF = RG = 500 RL = 150 VS = 15V VS = 10V VS = 2.5V VS = 5V
IN
0
-2
-4
+
LT1360 - 510 510
75
OUT 75
-6
-8 1 10 FREQUENCY (MHz) 100
1360 AI02
Input Considerations Each of the LT1360 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 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.
9
LT1360
APPLICATIONS INFORMATION
Power Dissipation The LT1360 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: LT1360CN8: TJ = TA + (PD x 130C/W) LT1360CS8: TJ = TA + (PD x 190C/W) 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: LT1360CS8 at 70C, VS = 15V, RL = 250 PDMAX = (30V)(5.8mA) + (7.5V)2/250 = 399mW TJMAX = 70C + (399mW)(190C/W) = 146C Circuit Operation The LT1360 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 LT1360 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 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. Comparison to Current Feedback Amplifiers The LT1360 enjoys the high slew rates of Current Feedback Amplifiers (CFAs) while maintaining the characteristics of a true voltage feedback amplifier. The primary differences are that the LT1360 has two high impedance inputs and its closed loop bandwidth decreases as the gain increases. CFAs have a low impedance inverting input and maintain relatively constant bandwidth with increasing gain. The LT1360 can be used in all traditional op amp configurations including integrators and applications such as photodiode amplifiers and I-to-V converters where there may be significant capacitance on the inverting input. The frequency compensation is internal and not dependent on the value of the feedback resistor. For CFAs, the feedback resistance is fixed for a given bandwidth and capacitance on the inverting input can cause peaking or oscillations. The slew rate of the LT1360 in noninverting gain configurations is also superior in most cases.
10
U
W
U
U
LT1360
TYPICAL APPLICATIONS
Photodiode Preamp with AC Coupling Loop
iPD
SFH205 10k 1F
10k -5V
909 VIN
SI PLIFIED SCHE ATIC
V+
-IN C CC
V-
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
1pF 1N5712 10k 1N5712 VS = 5V f-3dB = 100KHz, 5.5MHz
-
LT1360 VOUT 2k 2k 300pF
+
-
1/2 LT1358
5.1k
-
1/2 LT1358
+
+
1360 TA03
1MHz, 4th Order Butterworth Filter
909 47pF 22pF 2.67k 220pF 1.1k
-
LT1360
1.1k
2.21k 470pF
-
LT1360 VOUT
+
+
1360 TA04
W
W
R1 500
+IN
RC OUT
1360 SS01
11
LT1360
PACKAGE DESCRIPTION U
Dimension in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP
0.400 (10.160) MAX 8 7 6 5
0.250 0.010 (6.350 0.254)
1
2
3
4
0.300 - 0.320 (7.620 - 8.128)
0.045 - 0.065 (1.143 - 1.651)
0.130 0.005 (3.302 0.127)
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 +0.635 8.255 -0.381
)
0.045 0.015 (1.143 0.381) 0.100 0.010 (2.540 0.254)
0.018 0.003 (0.457 0.076)
N8 0392
S8 Package 8-Lead Plastic SOIC
0.189 - 0.197 (4.801 - 5.004) 8 7 6 5
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157 (3.810 - 3.988)
1 0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0.016 - 0.050 0.406 - 1.270
2
3
4
0.053 - 0.069 (1.346 - 1.752) 0.004 - 0.010 (0.101 - 0.254)
0- 8 TYP
0.014 - 0.019 (0.355 - 0.483)
0.050 (1.270) BSC
SO8 0392
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
LT/GP 0494 10K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1994

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