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LT1812 3mA, 100MHz, 750V/s Operational Amplifier with Shutdown
FEATURES
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DESCRIPTIO
100MHz Gain Bandwidth 750V/s Slew Rate 3.6mA Maximum Supply Current 50A Supply Current in Shutdown 8nV/Hz Input Noise Voltage Unity-Gain Stable 1.5mV Maximum Input Offset Voltage 4A Maximum Input Bias Current 400nA Maximum Input Offset Current 40mA Minimum Output Current, VOUT = 3V 3.5V Minimum Input CMR, VS = 5V 30ns Settling Time to 0.1%, 5V Step Specified at 5V, Single 5V Supplies Operating Temperature Range: - 40C to 85C
The LT(R)1812 is a low power, high speed, very high slew rate operational amplifier with excellent DC performance. The LT1812 features reduced supply current, lower input offset voltage, lower input bias current and higher DC gain than other devices with comparable bandwidth. A power saving shutdown feature reduces supply current to 50A. The circuit topology is a voltage feedback amplifier with the slewing characteristics of a current feedback amplifier. The output drives a 100 load to 3.5V with 5V supplies. On a single 5V supply, the output swings from 1.1V to 3.9V with a 100 load connected to 2.5V. The amplifier is stable with a 1000pF capacitive load which makes it useful in buffer and cable driver applications. The LT1812 is manufactured on Linear Technology's advanced low voltage complementary bipolar process. The dual version is the LT1813. For higher supply voltage single, dual and quad operational amplifiers with up to 70MHz gain bandwidth, see the LT1351 through LT1365 data sheets.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATIO S
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Wideband Amplifiers Buffers Active Filters Video and RF Amplification Cable Drivers Data Acquisition Systems
TYPICAL APPLICATIO
4MHz, 4th Order Butterworth Filter
232 274 47pF
VOLTAGE GAIN (dB)
10 0 -10 -20 -30 -40 -50 -60 -70 -80
1812 TA01
VIN 220pF
LT1812
470pF
+
-
+
-
232
665
274
562
22pF
LT1812
VOUT
-90 0.1
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Filter Frequency Response
VS = 5V VIN = 600mVP-P PEAKING < 0.12dB 1 10 FREQUENCY (MHz) 100
1812 TA02
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LT1812
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW NC 1 -IN 2 +IN 3 V- 4 8 7 6 5 SHDN V+ VOUT NC
Total Supply Voltage (V + to V -) ............................. 12.6V Differential Input Voltage (Transient Only, Note 2) ... 3V Input Voltage ........................................................... VS Output Short-Circuit Duration (Note 3) ............ Indefinite Operating Temperature Range (Note 8) ... - 40C to 85C Specified Temperature Range (Note 8) .............................................. - 40C to 85C Maximum Junction Temperature ......................... 150C Storage Temperature Range .................. - 65C to 150C Lead Temperature (Soldering, 10 sec)................... 300C
ORDER PART NUMBER LT1812CS8 LT1812IS8 S8 PART MARKING 1812 1812I
S8 PACKAGE 8-LEAD PLASTIC SO
TJMAX = 150C, JA = 80C/ W (NOTE 9)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL VOS IOS IB en in RIN CIN VCM CMRR PSRR AVOL VOUT IOUT ISC SR FPBW GBW tr, tf OS tPD ts THD PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Noise Voltage Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range (Positive) Input Voltage Range (Negative) Common Mode Rejection Ratio Minimum Supply Voltage Power Supply Rejection Ratio Large-Signal Voltage Gain Maximum Output Swing Maximum Output Current Output Short-Circuit Current Slew Rate Full Power Bandwidth Gain Bandwidth Product Rise Time, Fall Time Overshoot Propagation Delay Settling Time Total Harmonic Distortion Differential Gain Differential Phase ROUT Output Resistance (Note 4)
TA = 25C, VS = 5V, VCM = 0V unless otherwise noted.
MIN TYP 0.4 30 - 0.9 MAX 1.5 400 4 UNITS mV nA A nV/Hz pA/Hz M M pF - 3.5 2 V V dB V dB V/mV V/mV V V mA mA V/s MHz MHz ns % ns ns dB % DEG
CONDITIONS
f = 10kHz f = 10kHz VCM = 3.5V Differential 3
8 1 10 1.5 2 3.5 4.2 - 4.2 85 1.25 97 3.0 2.5 4.0 3.5 60 110 750 40 75 100 2 25 2.8 30 -76 0.12 0.07 0.4
VCM = 3.5V VS = 2V to 5.5V VOUT = 3V, RL = 500 VOUT = 3V, RL = 100 RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive VOUT = 3V, 30mV Overdrive VOUT = 0V, 1V Overdrive (Note 3) AV = - 1 (Note 5) 3V Peak (Note 6) f = 200kHz AV = 1, 10% to 90%, 0.1V, RL = 100 AV = 1, 0.1V, RL = 100 AV = 1, 50% VIN to 50% VOUT, 0.1V, RL = 100 5V Step, 0.1%, AV = - 1 f = 1MHz, VOUT = 2VP-P, AV = 2, RL = 500 VOUT = 2VP-P, AV = 2, RL = 150 VOUT = 2VP-P, AV = 2, RL = 150 AV = 1, f = 1MHz
75 78 1.5 1.0 3.80 3.35 40 75 500
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LT1812
ELECTRICAL CHARACTERISTICS
SYMBOL ISHDN IS PARAMETER SHDN Pin Current Supply Current
TA = 25C, VS = 5V, VCM = 0V unless otherwise noted.
MIN -100 TYP 0 - 50 3 50 MAX 1 3.6 100 UNITS A A mA A + 2.0V (On) + 0.4V (Off)
CONDITIONS SHDN > V - SHDN < V -
SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off)
TA = 25C, VS = 5V, VCM = 2.5V, RL to 2.5V unless otherwise noted.
SYMBOL VOS IOS IB en in RIN CIN VCM CMRR AVOL VOUT PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Noise Voltage Density Input Noise Current Density Input Resistance Input Capacitance Input Voltage Range (Positive) Input Voltage Range (Negative) Common Mode Rejection Ratio Large-Signal Voltage Gain Maximum Output Swing (Positive) Maximum Output Swing (Negative) IOUT ISC SR FPBW GBW tr, tf OS tPD ts THD Maximum Output Current Output Short-Circuit Current Slew Rate Full Power Bandwidth Gain Bandwidth Product Rise Time, Fall Time Overshoot Propagation Delay Settling Time Total Harmonic Distortion Differential Gain Differential Phase Output Resistance SHDN Pin Current Supply Current CONDITIONS (Note 4) MIN TYP 0.5 30 - 1.0 8 1 10 1.5 2 4 1 82 2.0 1.5 4.1 3.9 0.9 1.1 40 80 350 55 94 2.1 25 3 30 -75 0.22 0.21 0.45 0 - 20 2.7 20 MAX 2.0 400 4 UNITS mV nA A nV/Hz pA/Hz M M pF V V dB V/mV V/mV V V V V mA mA V/s MHz MHz ns % ns ns dB % DEG A A mA A
f = 10kHz f = 10kHz VCM = 1.5V to 3.5V Differential
3
3.5 VCM = 1.5V to 3.5V VOUT = 1.5V to 3.5V, RL = 500 VOUT = 1.5V to 3.5V, RL = 100 RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive VOUT = 3.5V or 1.5V, 30mV Overdrive VOUT = 2.5V, 1V Overdrive (Note 3) AV = - 1 (Note 5) 1V Peak (Note 6) f = 200kHz AV = 1, 10% to 90%, 0.1V, RL = 100 AV = 1, 0.1V, RL = 100 AV = 1, 50% VIN to 50% VOUT, 0.1V, RL = 100 2V Step, 0.1%, AV = - 1 f = 1MHz, VOUT = 2VP-P, AV = 2, RL = 500 VOUT = 2VP-P, AV = 2, RL = 150 VOUT = 2VP-P, AV = 2, RL = 150 AV = 1, f = 1MHz SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) 73 1.0 0.7 3.9 3.7
1.5
1.1 1.3
25 55 200 65
ROUT ISHDN IS
1 3.6 50
- 50
0C TA 70C, VS = 5V, VCM = 0V unless otherwise noted.
SYMBOL VOS VOS/T IOS IB PARAMETER Input Offset Voltage Input Offset Voltage Drift Input Offset Current Input Bias Current CONDITIONS (Note 4) (Note 7) MIN TYP 10 MAX 2 15 500 5 UNITS mV V/C nA A
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LT1812
ELECTRICAL CHARACTERISTICS
SYMBOL VCM CMRR PSRR AVOL VOUT IOUT ISC SR GBW ISHDN IS PARAMETER Input Voltage Range (Positive) Input Voltage Range (Negative) Common Mode Rejection Ratio Minimum Supply Voltage Power Supply Rejection Ratio Large-Signal Voltage Gain Maximum Output Swing Maximum Output Current Output Short-Circuit Current Slew Rate Gain Bandwidth Product SHDN Pin Current Supply Current
0C TA 70C. VS = 5V, VCM = 0V unless otherwise noted.
MIN 3.5 73 2 76 1.0 0.7 3.70 3.25 35 60 400 65 1.5 -150 4.6 150 TYP MAX - 3.5 UNITS V V dB V dB V/mV V/mV V V mA mA V/s MHz A A mA A
CONDITIONS
VCM = 3.5V VS = 2V to 5.5V VOUT = 3V, RL = 500 VOUT = 3V, RL = 100 RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive VOUT = 3V, 30mV Overdrive VOUT = 0V, 1V Overdrive (Note 3) AV = - 1 (Note 5) f = 200kHz SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off)
0C TA 70C, VS = 5V, VCM = 2.5V, RL to 2.5V unless otherwise noted.
VOS VOS/T IOS IB VCM CMRR AVOL VOUT Input Offset Voltage Input Offset Voltage Drift Input Offset Current Input Bias Current Input Voltage Range (Positive) Input Voltage Range (Negative) Common Mode Rejection Ratio Large-Signal Voltage Gain Maximum Output Swing (Positive) Maximum Output Swing (Negative) IOUT ISC SR GBW ISHDN IS Maximum Output Current Output Short-Circuit Current Slew Rate Gain Bandwidth Product SHDN Pin Current Supply Current (Note 4) (Note 7) 10 2.5 15 500 5 1.5 VCM = 1.5V to 3.5V VOUT = 1.5V to 3.5V, RL = 500 VOUT = 1.5V to 3.5V, RL = 100 RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive VOUT = 3.5V or 1.5V, 30mV Overdrive VOUT = 2.5V, 1V Overdrive (Note 3) AV = - 1 (Note 5) f = 200kHz SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) 71 0.7 0.5 3.8 3.6 1.2 1.4 20 45 150 55 1.5 - 75 4.5 75 mV V/C nA A V V dB V/mV V/mV V V V V mA mA V/s MHz A A mA A
3.5
- 40C TA 85C. VS = 5V, VCM = 0V unless otherwise noted (Note 8).
SYMBOL VOS VOS/T IOS IB VCM CMRR PARAMETER Input Offset Voltage Input Offset Voltage Drift Input Offset Current Input Bias Current Input Voltage Range (Positive) Input Voltage Range (Negative) Common Mode Rejection Ratio CONDITIONS (Note 4) (Note 7) MIN TYP 10 MAX 3 30 600 6 - 3.5 VCM = 3.5V 72 UNITS mV V/C nA A V V dB
3.5
4
LT1812
ELECTRICAL CHARACTERISTICS - 40C TA 85C. VS = 5V, VCM = 0V unless otherwise noted (Note 8).
SYMBOL PSRR AVOL VOUT IOUT ISC SR GBW ISHDN IS PARAMETER Minimum Supply Voltage Power Supply Rejection Ratio Large-Signal Voltage Gain Maximum Output Swing Maximum Output Current Output Short-Circuit Current Slew Rate Gain Bandwidth Product SHDN Pin Current Supply Current CONDITIONS VS = 2V to 5.5V VOUT = 3V, RL = 500 VOUT = 3V, RL = 100 RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive VOUT = 3V, 30mV Overdrive VOUT = 0V, 1V Overdrive (Note 3) AV = - 1 (Note 5) f = 200kHz SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) MIN 75 0.8 0.6 3.60 3.15 30 55 350 60 2 - 200 5 200 TYP MAX 2 UNITS V dB V/mV V/mV V V mA mA V/s MHz A A mA A
- 40C TA 85C, VS = 5V, VCM = 2.5V, RL to 2.5V unless otherwise noted (Note 8).
SYMBOL VOS VOS/T IOS IB VCM CMRR AVOL VOUT PARAMETER Input Offset Voltage Input Offset Voltage Drift Input Offset Current Input Bias Current Input Voltage Range (Positive) Input Voltage Range (Negative) Common Mode Rejection Ratio Large-Signal Voltage Gain Maximum Output Swing (Positive) Maximum Output Swing (Negative) IOUT ISC SR GBW ISHDN IS Maximum Output Current Output Short-Circuit Current Slew Rate Gain Bandwidth Product SHDN Pin Current Supply Current CONDITIONS (Note 4) (Note 7) MIN TYP 10 MAX 3.5 30 600 6 1.5 VCM = 1.5V to 3.5V VOUT = 1.5V to 3.5V, RL = 500 VOUT = 2.0V to 3.0V, RL = 100 RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive RL = 500, 30mV Overdrive RL = 100, 30mV Overdrive VOUT = 3.5V or 1.5V, 30mV Overdrive VOUT = 2.5V, 1V Overdrive (Note 3) AV = - 1 (Note 5) f = 200kHz SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) SHDN > V - + 2.0V (On) SHDN < V - + 0.4V (Off) 70 0.6 0.4 3.7 3.5 1.3 1.5 17 40 125 50 2 - 100 5 100 UNITS mV V/C nA A V V dB V/mV V/mV V V V V mA mA V/s MHz A A mA A
3.5
Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Differential inputs of 3V are appropriate for transient operation only, such as during slewing. Large sustained differential inputs can cause excessive power dissipation and may damage the part. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum when the output is shorted indefinitely. Note 4: Input offset voltage is pulse tested and is exclusive of warm-up drift. Note 5: Slew rate is measured between 2V on the output with 3V input for 5V supplies and 2VP-P on the output with a 3VP-P input for single 5V supplies.
Note 6: Full power bandwidth is calculated from the slew rate: FPBW = SR/2VP. Note 7: This parameter is not 100% tested. Note 8: The LT1812C is guaranteed to meet specified performance from 0C to 70C. The LT1812C is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LT1812I is guaranteed to meet specified performance from -40C to 85C. Note 9: JA is specified for a 2500mm2 board covered with 2 oz copper on both sides. Thermal resistance varies, depending upon the amount of PC board metal attached to the device. For this package in particular, power is dissipated primarily through Pin 4, which should therefore, have a good thermal connection to a copper plane.
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LT1812 TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Temperature
5
INPUT COMMON MODE RANGE (V)
INPUT BIAS CURRENT (A)
4
SUPPLY CURRENT (mA)
VS = 5V 3 VS = 2.5V 2
1
0 -50 -25
50 25 0 75 TEMPERATURE (C)
Input Bias Current vs Temperature
0
INPUT VOLTAGE NOISE (nV/Hz)
-0.2
INPUT BIAS CURRENT (A)
-0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -50 -25 VS = 5V VS = 2.5V
OPEN-LOOP GAIN (dB)
50 25 75 0 TEMPERATURE (C)
Open-Loop Gain vs Temperature
75.0 72.5 VS = 5V VO = 3V V+ - 0.5
OUTPUT VOLTAGE SWING (V)
-1.0 -1.5 - 2.0 RL = 100
OUTPUT VOLTAGE SWING (V)
OPEN-LOOP GAIN (dB)
70.0 67.5 65.0 62.5 60.0 -50 -25
RL = 500
RL = 100
50 25 75 0 TEMPERATURE (C)
6
UW
100
1812 G01
Input Common Mode Range vs Supply Voltage
V+ - 0.5 -1.0 -1.5 - 2.0 TA = 25C VOS < 1mV 2.0 1.5 1.0 0.5 V- 125 0 1 4 3 2 5 SUPPLY VOLTAGE ( V) 6 7
1812 G02
Input Bias Current vs Common Mode Voltage
0 TA = 25C VS = 5V
- 0.5
-1.0
-1.5
- 2.0 - 5.0
0 2.5 - 2.5 INPUT COMMON MODE VOLTAGE (V)
5.0
1812 G03
Input Noise Spectral Density
100 TA = 25C VS = 5V AV = 101 RS = 10k 10
INPUT CURRENT NOISE (pA/Hz) 75.0 72.5 70.0
Open-Loop Gain vs Resistive Load
TA = 25C
in 10 en 1
VS = 5V 67.5 VS = 2.5V 65.0 62.5 60 100
1
100 125
10
100
1k 10k FREQUENCY (Hz)
0.1 100k
1812 G05
1k LOAD RESISTANCE ()
10k
1812 G06
1812 G04
Output Voltage Swing vs Supply Voltage
TA = 25C VIN = 30mV V+ RL = 500 - 0.5 -1.0 -1.5 - 2.0
Output Voltage Swing vs Load Current
VS = 5V VIN = 30mV 85C 25C - 40C
2.0 1.5 1.0 0.5 V- RL = 500 0 1 4 3 2 5 SUPPLY VOLTAGE ( V) 6 7
1812 G08
2.0 1.5 1.0 0.5 V- -60 -40 0 20 40 -20 OUTPUT CURRENT (mA) 60
1812 G09
RL = 100
100
125
1812 G07
LT1812 TYPICAL PERFOR A CE CHARACTERISTICS
Output Short-Circuit Current vs Temperature
120
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 5V
SOURCE
115 110 SINK 105 100 95 90 -50 -25
OUTPUT STEP (V)
OUTPUT IMPEDANCE ()
50 25 75 0 TEMPERATURE (C)
Gain and Phase vs Frequency
70 60 50 GAIN
GAIN (dB)
SHUTDOWN SUPPLY CURRENT (A)
TA = 25C AV = -1 RF = RG = 500 PHASE
GAIN BANDWIDTH (MHz)
40 30 2.5V 20 10 0 2.5V 5V 5V
-10 10k
100k
1M 10M FREQUENCY (Hz)
100M
Gain vs Frequency
6 4 2 0 TA = 25C AV = 1 NO RL VS = 2.5V VS = 5V 8 6 4
GAIN (dB)
GAIN (dB)
2 VS = 2.5V 0 -2 VS = 5V
GAIN (dB)
-2 -4 -6 -8 -10 -12 -14 1M
10M 100M FREQUENCY (Hz)
UW
100
1812 G10
1812 G13
1812 G16
Settling Time vs Output Step
5 4 3 2 1 0 -1 -2 -3 -4 -5 125 0 TA = 25C VS = 5V AV = -1 RF = 500 CF = 3pF 0.1% SETTLING 5 20 15 10 25 SETTLING TIME (ns) 30 35
10 100
Output Impedance vs Frequency
AV = 100 AV = 10
1
AV = 1
0.1
0.01 TA = 25C VS = 5V 100k 1M 10M FREQUENCY (Hz) 100M
1812 G12
0.001 10k
1812 G11
Shutdown Supply Current vs Temperature
120 100 80
PHASE (DEG)
70 60 50 40 30 20 10 0 -50 -25 VS = 2.5V VSHDN = V - + 0.4V VS = 5V
Gain Bandwidth and Phase Margin vs Temperature
115 RL = 500 GBW VS = 5V GBW VS = 2.5V
105
PHASE MARGIN (DEG)
60 40 20 0
95
85
PHASE MARGIN VS = 5V PHASE MARGIN VS = 2.5V
40
38
-20 -40 1000M
50 25 75 0 TEMPERATURE (C)
100
125
-50 -25
50 25 0 75 TEMPERATURE (C)
100
36 125
1812 G14
1812 G15
Gain vs Frequency
12 TA = 25C AV = 2 RL = 100
Gain vs Frequency
TA = 25C AV = -1 V = 5V 8S RF = RG = 500 NO RL 4 CL= 1000pF CL= 500pF CL= 200pF CL= 100pF CL= 50pF CL= 0
0
-4 -4 -6 1M -8 10M 100M FREQUENCY (Hz) 500M
1812 G17
500M
1
10M FREQUENCY (Hz)
100M 200M
1812 G18
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LT1812 TYPICAL PERFOR A CE CHARACTERISTICS
Gain Bandwidth and Phase Margin vs Supply Voltage
110
100
POWER SUPPLY REJECTION RATIO (dB)
80 -PSRR +PSRR 40
COMMON MODE REJECTION RATIO (dB)
TA = 25C
GBW RL = 500
PHASE MARGIN (DEG)
GAIN BANDWIDTH (MHz)
90 GBW RL = 100 70 PHASE MARGIN RL = 100 40 PHASE MARGIN RL = 500 0 1 5 4 3 SUPPLY VOLTAGE (V) 2 6 7
1812 G19
Slew Rate vs Supply Voltage
1200 TA =25C 1100 AV = -1 /2 V =V 1000 RIN= R S(TOTAL)500 F G = RL = 900 800 700 600 500 400 300 200 0 1 4 3 2 5 SUPPLY VOLTAGE (V) 6 7
1812 G22
SLEW RATE (V/s)
SLEW RATE (V/s)
SR - SR +
SR - 400 SR + 300
SLEW RATE (V/s)
Slew Rate vs Temperature
TOTAL HARMONIC DISTORTION + NOISE (%)
1200 1000 SR- VS = 5V
SLEW RATE (V/s)
800 600 400 200 0 -50 -25 SR+ VS = 2.5V
0.005 AV = 1
OUTPUT VOLTAGE (VP-P)
SR - VS = 2.5V
50 25 75 0 TEMPERATURE (C)
8
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SR+ VS = 5V 100
1812 G25
Power Supply Rejection Ratio vs Frequency
TA = 25C AV = 1 VS = 5V 100
Common Mode Rejection Ratio vs Frequency
TA = 25C VS = 5V
80
60
60
45
40
20
20
35
0 1k 10k 1M 100k FREQUENCY (Hz) 10M 100M
1812 G20
0 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M
1812 G21
Slew Rate vs Supply Voltage
600 TA =25C AV = -1 VIN = 1V 500 RF = RG = RL = 500
1200
Slew Rate vs Input Level
TA =25C AV = -1 V = 5V 1000 RS = R = R = 500 F G L 800
SR - SR +
600
400
200 0 1 4 3 2 5 SUPPLY VOLTAGE (V) 6 7
1812 G23
200 0 1 2 4 3 5 6 INPUT LEVEL (VP-P) 7 8
1812 G24
Total Harmonic Distortion + Noise vs Frequency
0.01
9 8
Undistorted Output Swing vs Frequency
AV = - 1 AV = 1
AV = -1
7 6 5 4 3 2 1
0.002 TA = 25C VS = 5V VO = 2VP-P RL = 500 100 1k 10k FREQUENCY (Hz) 100k
1812 G26
125
0.001 10
0 100k
TA = 25C VS = 5V RL = 100 2% MAX DISTORTION 1M 10M FREQUENCY (Hz) 100M
1812 G27
LT1812 TYPICAL PERFOR A CE CHARACTERISTICS
2nd and 3rd Harmonic Distortion vs Frequency
-30 -40 HARMONIC DISTORTION (dB) -50 -60 -70 -80 3RD HARMONIC -90 -100 100k 2ND HARMONIC RL = 500 1M FREQUENCY (Hz) 10M
1812 G28
DIFFERENTIAL PHASE (DEG)
TA = 25C AV = 2 VS = 5V VO = 2VP-P 2ND HARMONIC 3RD HARMONIC RL = 100
DIFFERENTIAL GAIN RL = 1k 0.25 0.20 0.15 0.10 0.05 0 TA = 25C 4 10 8 6 TOTAL SUPPLY VOLTAGE (V) 12
1812 G29
OVERSHOOT (%)
Small-Signal Transient, AV = -1
Large-Signal Transient, AV = -1
UW
1812 G31 1812 G34
Differential Gain and Phase vs Supply Voltage
0.25 DIFFERENTIAL GAIN RL = 150 0.20 0.15
Capacitive Load Handling
100 90 80 DIFFERENTIAL GAIN (%) 70 60 50 40 30 20 10 0 10 100 1000 CAPACITIVE LOAD (pF) 10000
1812 G30
TA = 25C VS = 5V AV = 1
0.10 0.05 0
DIFFERENTIAL PHASE RL = 150 DIFFERENTIAL PHASE RL = 1k
AV = -1
Small-Signal Transient, AV = 1
Small-Signal Transient, AV = 1, CL = 1000pF
1812 G32
1812 G33
Large-Signal Transient, AV = 1
Large-Signal Transient, AV = 1, CL = 1000pF
1812 G35
1812 G36
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LT1812
APPLICATIO S I FOR ATIO
Layout and Passive Components
The LT1812 amplifier is more tolerant of less than ideal layouts than other high speed amplifiers. For maximum performance (for example, fast 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 that can cause peaking or even oscillations. If feedback resistors greater than 2k are used, a parallel capacitor of value CF > RG * CIN/RF should be used to cancel the input pole and optimize dynamic performance. For applications where the DC noise gain is 1 and a large feedback resistor is used, CF should be greater than or equal to CIN. An example would be an I-to-V converter. Input Considerations Each of the LT1812 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 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 3V without damage and need no clamping or source resistance for protection. The device should not be used as a comparator because with sustained differential inputs, excessive power dissipation may result. Capacitive Loading The LT1812 is stable with a 1000pF capacitive load, which is outstanding for a 100MHz amplifier. This is accomplished by sensing the load induced output pole and adding compensation at the amplifier gain node. As the
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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. Slew Rate The slew rate is proportional to the differential input voltage. Highest slew rates are therefore seen in the lowest gain configurations. For example, a 5V output step in a gain of 10 has a 0.5V input step, whereas in unity gain there is a 5V input step. The LT1812 is tested for slew rate in a gain of - 1. Lower slew rates occur in higher gain configurations. Shutdown The LT1812 has a shutdown pin (SHDN, Pin 8) for conserving power. When this pin is open or biased at least 2V above the negative supply, the part operates normally. When pulled down to V -, the supply current drops to about 50A. Typically, the turn-off delay is 1s and the turn-on delay 0.5s. The current out of the SHDN pin is also typically 50A. In shutdown mode, the amplifier output is not isolated from the inputs, so the LT1812 shutdown feature cannot be used for multiplexing applications. The 50A typical shutdown current is exclusive of any output (load) current. In order to prevent load current (and maximize the power savings), either the load needs to be disconnected, or the input signal needs to be 0V. Even in shutdown mode, the LT1812 can still drive significant current into a load. For example, in an AV = 1 configuration, when driven with a 1V DC input, the LT1812 drives 2mA into a 100 load. It takes about 500s for the load current to reach this value. Power Dissipation The LT1812 combines high speed and large output drive in a small package. It is possible to exceed the maximum junction temperature under certain conditions. Maximum
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LT1812
APPLICATIO S I FOR ATIO
junction temperature (TJ) is calculated from the ambient temperature (TA) and power dissipation (PD) as follows: LT1812CS8: TJ = TA + (PD * 80C/W) (Note 9) Power dissipation is composed of two parts. The first is due to the quiescent supply current and the second is due to on-chip dissipation caused by the load current. The worst-case load induced power occurs 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 or PDMAX = (V + - V - )(ISMAX) + (V + - VOMAX)(VOMAX/RL) Example: LT1812CS8 at 70C, VS = 5V, RL = 100 PDMAX = (10V)(4.5mA) + (2.5V)2/100 = 108mW TJMAX = 70C + (108mW)(80C/W) = 79C Circuit Operation The LT1812 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 that drive a 300 resistor. The input voltage
SI PLIFIED SCHEMATIC
V+ RB
-IN C BIAS CONTROL SHDN V-
1812 SS
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.
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appears across the resistor generating currents that are mirrored into the high impedance node. Complementary followers form an output stage that 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. 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 capacitive loads (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 unitygain cross 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 the total phase lag does not exceed 180 degrees (zero phase margin) and the amplifier remains stable. In this way, the LT1812 is stable with up to 1000pF capacitive loads in unity gain, and even higher capacitive loads in higher closed-loop gain configurations.
R1 300 +IN RC CC OUT
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LT1812
TYPICAL APPLICATIO
VIN 2VP-P 2.5VDC
PACKAGE DESCRIPTION
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 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP 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) 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
0.016 - 0.050 (0.406 - 1.270)
RELATED PARTS
PART NUMBER LT1360/LT1361/LT1362 LT1363/LT1364/LT1365 LT1395/LT1396/LT1397 LT1398/LT1399 LT1813 DESCRIPTION Single/Dual/Quad 50MHz, 800V/s, C-Load Amplifiers Single/Dual/Quad 70MHz, 1000V/s C-Load Amplifiers Single/Dual/Quad 400MHz Current Feedback Amplifiers Dual/Triple 300MHz Current Feedback Amplifiers Dual 3mA, 100MHz, 750V/s Operational Amplifier
TM
C-Load is a trademark of Linear Technology Corporation.
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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Single 5V Supply 10MS/s 12-Bit ADC Buffer +
LT1812 68 LTC1420 12 BITS
-
470pF
1812 TA03
10MS/s
0.050 (1.270) BSC
SO8 1298
1
2
3
4
COMMENTS 4mA Supply Current, 1mV Max VOS, 1A Max IB 50mA Output Current, 1.5mV Max VOS, 2A Max IB 4.6mA Supply Current, 800V/s, 80mA Output Current 4.5mA Supply Current, 80mA Output Current, Shutdown Dual Version of the LT1812
1812f LT/TP 0200 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1999

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