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LT1226 Low Noise Very High Speed Operational Amplifier
FEATURES
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DESCRIPTIO
Gain of 25 Stable 1GHz Gain Bandwidth 400V/s Slew Rate 2.6nV/Hz Input Noise Voltage 50V/mV Minimum DC Gain, RL = 500 1mV Maximum Input Offset Voltage 12V Minimum Output Swing into 500 Wide Supply Range 2.5V to 15V 7mA Supply Current 100ns Settling Time to 0.1%, 10V Step Drives All Capacitive Loads
The LT1226 is a low noise, very high speed operational amplifier with excellent DC performance. The LT1226 features low input offset voltage and high DC gain. The circuit is a single gain stage with outstanding settling characteristics. The fast settling time makes the circuit an ideal choice for data acquisition systems. The output is capable of driving a 500 load to 12V with 15V supplies and a 150 load to 3V on 5V supplies. The circuit is also capable of driving large capacitive loads which makes it useful in buffer or cable driver applications. The LT1226 is a member of a family of fast, high performance amplifiers that employ Linear Technology Corporation's advanced bipolar complementary processing.
APPLICATI
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Wideband Amplifiers Buffers Active Filters Video and RF Amplification Cable Drivers Data Acquisition Systems
TYPICAL APPLICATI
V+
Photodiode Preamplifier, AV = 5.1k, BW = 15MHz
Gain of +25 Pulse Response
+
51 LT1226
-
5.1k
51
LT1226 TA01
U
LT1226 TA02
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1
LT1226 ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW NULL -IN +IN V- 1 2 3 4 8 7 6 5 NULL V+ OUT NC
Total Supply Voltage (V+ to V -) ............................... 36V Differential Input Voltage ......................................... 6V Input Voltage ............................................................VS Output Short Circuit Duration (Note 1) ............ Indefinite Operating Temperature Range LT1226C ................................................ 0C to 70C Maximum Junction Temperature Plastic Package .............................................. 150C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec.)................. 300C
ORDER PART NUMBER LT1226CN8 LT1226CS8 S8 PART MARKING 1226
N8 PACKAGE S8 PACKAGE 8-LEAD PLASTIC DIP 8-LEAD PLASTIC SOIC
LT1226 PO01
ELECTRICAL CHARACTERISTICS
SYMBOL VOS IOS IB en in RIN CIN PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Noise Voltage Input Noise Current Input Resistance Input Capacitance Input Voltage Range + Input Voltage Range - CMRR PSRR AVOL VOUT IOUT SR GBW tr, tf Common-Mode Rejection Ratio Power Supply Rejection Ratio Large Signal Voltage Gain Output Swing Output Current Slew Rate Full Power Bandwidth Gain Bandwidth Rise Time, Fall Time Overshoot Propagation Delay ts Settling Time Differential Gain Differential Phase RO IS Output Resistance Supply Current
VS = 15V, TA = 25C, VCM = 0V unless otherwise noted.
MIN TYP 0.3 100 4 MAX 1.0 400 8 UNITS mV nA A nV/Hz pA/Hz M k pF V - 12 V dB dB V/mV V mA V/s MHz GHz ns % ns ns % Deg 9 mA
CONDITIONS (Note 2)
f = 10kHz f = 10kHz VCM = 12V Differential 24
2.6 1.5 40 15 2 12 14 - 13 103 110 150 13.3 40 400 6.4 1 5.5 35 5.5 100 0.7 0.6 3.1 7
VCM = 12V VS = 5V to 15V VOUT = 10V, RL = 500 RL = 500 VOUT = 12V (Note 3) 10V Peak, (Note 4) f = 1MHz AVCL = + 25,10% to 90%, 0.1V AVCL = +25, 0.1V 50% VIN to 50% VOUT 10V Step, 0.1%, AV = - 25 f = 3.58MHz, AV = +25, RL = 150 f = 3.58MHz, AV = +25, RL = 150 AVCL = +25, f = 1MHz
94 94 50 12.0 24 250
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LT1226
ELECTRICAL CHARACTERISTICS VS = 5V, TA = 25C, VCM = 0V unless otherwise noted.
SYMBOL VOS IOS IB PARAMETER Input Offset Voltage Input Offset Current Input Bias Current Input Voltage Range + Input Voltage Range - CMRR AVOL VOUT IOUT SR GBW tr, tf Common-Mode Rejection Ratio Large Signal Voltage Gain Output Voltage Output Current Slew Rate Full Power Bandwidth Gain Bandwidth Rise Time, Fall Time Overshoot Propagation Delay ts IS Settling Time Supply Current VCM = 2.5V VOUT = 2.5V, RL = 500 VOUT = 2.5V, RL = 150 RL = 500 RL = 150 VOUT = 3V (Note 3) 3V Peak, (Note 4) f = 1MHz AVCL = +25, 10% to 90%, 0.1V AVCL = +25, 0.1V 50% VIN to 50% VOUT - 2.5V to 2.5V, 0.1%, AV = - 24 94 50 3.0 3.0 20 2.5 CONDITIONS (Note 2) MIN TYP 1.0 100 4 4 -3 103 100 75 3.7 3.3 40 250 13.3 700 8 25 8 60 7 9 -2.5 MAX 1.4 400 8 UNITS mV nA A V V dB V/mV V/mV V V mA V/s MHz MHz ns % ns ns mA
ELECTRICAL CHARACTERISTICS
SYMBOL VOS PARAMETER Input Offset Voltage Input VOS Drift IOS IB CMRR PSRR AVOL VOUT IOUT SR IS Input Offset Current Input Bias Current Common-Mode Rejection Ratio Power Supply Rejection Ratio Large Signal Voltage Gain Output Swing Output Current Slew Rate Supply Current CONDITIONS
0C TA 70C, VCM = 0V unless otherwise noted.
MIN TYP 0.3 1.0 6 100 4 92 92 35 35 12.0 3.0 24 20 250 103 110 150 100 13.3 3.3 40 40 400 7 10.5 MAX 1.3 1.8 600 9 UNITS mV mV V/C nA A dB dB V/mV V/mV V V mA mA V/s mA
VS = 15V, (Note 2) VS = 5V, (Note 2) VS = 15V and VS = 5V VS = 15V and VS = 5V VS = 15V, VCM = 12V and VS = 5V, VCM = 2.5V VS = 5V to 15V VS = 15V, VOUT = 10V, RL = 500 VS = 5V, VOUT = 2.5V, RL = 500 VS = 15V, RL = 500 VS = 5V, RL = 500 or 150 VS = 15V, VOUT = 12V VS = 5V, VOUT = 3V VS = 15V, (Note 3) VS = 15V and VS = 5V
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 tested with automated test equipment in <1 second.
Note 3: Slew rate is measured between 10V on an output swing of 12V on 15V supplies, and 2V on an output swing of 3.5V on 5V supplies. Note 4: Full power bandwidth is calculated from the slew rate measurement: FPBW = SR/2Vp.
3
LT1226
TYPICAL PERFOR A CE CHARACTERISTICS
Input Common Mode Range vs Supply Voltage
20
MAGNITUDE OF INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
15
7.5
OUTPUT VOLTAGE SWING (V)
TA = 25C VOS < 1mV
10 +VCM 5 -VCM
0 0 5 10 15 20
LT1226 TPC01
SUPPLY VOLTAGE (V)
Output Voltage Swing vs Resistive Load
30
OUTPUT VOLTAGE SWING (Vp-p)
25 20 15 10 5 0 10
TA = 25C VOS = 30mV
INPUT BIAS CURRENT (A)
VS = 15V
OPEN LOOP GAIN (dB)
VS = 5V
100
1k
LOAD RESISTANCE ()
LT1226 TPC04
Supply Current vs Temperature
10 VS = 15V 9 4.75 5.0
OUTPUT SHORT CIRCUIT CURRENT (mA)
INPUT BIAS CURRENT (A)
SUPPLY CURRENT (mA)
8 7 6 5 4 -50
-25
0
25
50
75
TEMPERATURE (C)
LT1226 TPC07
4
UW
100
Supply Current vs Supply Voltage
8.0 TA = 25C 15 20
Output Voltage Swing vs Supply Voltage
TA = 25C RL = 500 VOS = 30mV
+VSW 10 -VSW 5
7.0
6.5
6.0 0 5 10 15 20
LT1226 TPC02
0 0 5 10 15 20
LT1226 TPC03
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Input Bias Current vs Input Common Mode Voltage
5.0 VS = 15V TA = 25C IB+ + IB- IB = 2 120
Open Loop Gain vs Resistive Load
TA = 25C 110 VS = 15V
4.5
100
4.0
VS = 5V
90
3.5
80
10k
3.0 -15
70 -10 -5 0 5 10 15 10 100 1k 10k
LT1226 TPC06
INPUT COMMON MODE VOLTAGE (V)
LT1226 TPC05
LOAD RESISTANCE ()
Input Bias Current vs Temperature
55 VS = 15V I +I IB = B+ B-
2
Output Short Circuit Current vs Temperature
VS = 5V 50 45 40 SOURCE 35 30 25 -50 SINK
4.5 4.25 4.0 3.75 3.5 -50
125
-25
0
25
50
75
100
125
-25
0
25
50
75
100
125
TEMPERATURE (C)
LT1226 TPC08
TEMPERATURE (C)
LT1226 TPC09
LT1226
TYPICAL PERFOR A CE CHARACTERISTICS
Input Noise Spectral Density
1000 10
POWER SUPPLY REJECTION RATIO (dB)
COMMON MODE REJECTION RATIO (dB)
INPUT VOLTAGE NOISE (nV/Hz)
in 100
VS = 15V TA = 25C AV = +101 RS = 100k 1.0
10 en 1 10 100 1k FREQUENCY (Hz)
LT1226 TPC10
10k
Voltage Gain and Phase vs Frequency
110 VS = 15V 90 80 VS = 5V 70 VS = 5V VS = 15V 60 100
10 8 6
OUTPUT SWING (V)
VOLTAGE GAIN (dB)
4 2 0 -2 -4 -6 -8
AV = -25
AV = +25
VOLTAGE MAGNITUDE (dB)
50
30 TA = 25C 10 100 10k 100k 1M 1k FREQUENCY (Hz)
Closed Loop Output Impedance vs Frequency
100 VS = 15V TA = 25C AV = +25
GAIN BANDWIDTH (MHz)
OUTPUT IMPEDANCE ()
10
1.05 1.0 0.95 0.90
SLEW RATE (V/s)
1
0.1
0.01 10k
100k
1M FREQUENCY (Hz)
10M
UW
10M
LT1226 TPC13 LT1226 TPC16
Power Supply Rejection Ratio vs Frequency
120 VS = 15V TA = 25C 100
Common Mode Rejection Ratio vs Frequency
120 100 80 60 40 20 0 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M VS = 15V TA = 25C
INPUT VOLTAGE NOISE (nV/Hz)
PHASE MARGIN (DEGREES)
80 -PSRR 60 +PSRR
0.1
40
0.01 100k
0 100
1k
10k 100k 1M FREQUENCY (Hz)
10M
100M
LT1226 TPC11
LT1226 TPC12
Output Swing vs Settling Time
38
VS = 15 TA = 25C 10mV SETTLING
Frequency Response vs Capacitive Load
36 34 32 30 28 26 24 22 20 18 C = 1000pF C = 500pF VS = 15V TA = 25C AV = -25 C = 100pF C = 50pF C = 0pF
40
20
AV = -25 AV = +25
0 100M
-10
0
20
60 80 40 SETTLING TIME (ns)
100
120
1M
10M FREQUENCY (HZ)
100M
LT1226 TPC15
LTC1226 TPC14
Gain Bandwidth vs Temperature
1.15 VS = 15V 1.10 450 400 500
Slew Rate vs Temperature
VS = 15V AV = -25 -SR
+SR 350 300 250 200 -50 -25
100M
0.85 -50 -25
50 25 75 0 TEMPERATURE (C)
100
125
50 25 75 0 TEMPERATURE (C)
100
125
LT1226 TPC17
LT1226 TPC18
5
LT1226
APPLICATI S I FOR ATIO U
Small Signal, AV = +25 Small Signal, AV = - 25
LT1226 AI02
The LT1226 may be inserted directly into HA2541, HA2544, AD847, EL2020 and LM6361 applications, provided that the amplifier configuration is a noise gain of 25 or greater, and the nulling circuitry is removed. The suggested nulling circuit for the LT1226 is shown below.
Offset Nulling
V+ 5k 1 3
+ -
8 7 LT1226 4 0.1F V-
LT1226 AI01
6
2
Layout and Passive Components As with any high speed operational amplifier, care must be taken in board layout in order to obtain maximum performance. Key layout issues include: use of a ground plane, minimization of stray capacitance at the input pins, short lead lengths, RF-quality bypass capacitors located close to the device (typically 0.01F to 0.1F), and use of low ESR bypass capacitors for high drive current applications (typically 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. Feedback resistors greater than 5k are not recommended because a pole is formed with the input capacitance which can cause peaking. If feedback resistors greater than 5k are used, a parallel capacitor of 5pF to 10pF should be used to cancel the input pole and optimize dynamic performance. Transient Response The LT1226 gain bandwidth is 1GHz when measured at 1MHz. The actual frequency response in a gain of +25 is considerably higher than 40MHz due to peaking caused by a second pole beyond the gain of 25 crossover point. This is reflected in the small signal transient response. Higher noise gain configurations exhibit less overshoot as seen in the inverting gain of 25 response.
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0.1F
The large signal response in both inverting and noninverting gain shows symmetrical slewing characteristics. Normally the noninverting response has a much faster rising edge due to the rapid change in input common mode voltage which affects the tail current of the input differential pair. Slew enhancement circuitry has been added to the LT1226 so that the falling edge slew rate is enhanced which balances the noninverting slew rate response.
Large Signal, AV = +25 Large Signal, AV = - 25
LT1226 AI03
Input Considerations Resistors in series with the inputs are recommended for the LT1226 in applications where the differential input voltage exceeds 6V continuously or on a transient basis. An example would be in noninverting configurations with high input slew rates or when driving heavy capacitive loads. The use of balanced source resistance at each input is recommended for applications where DC accuracy must be maximized. Capacitive Loading The LT1226 is stable with all capacitive loads. 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
LT1226
APPLICATI
S I FOR ATIO
frequency domain and in the transient response. The photo of the small signal response with 1000pF load shows 55% peaking. The large signal response with a 10,000pF load shows the output slew rate being limited by the short circuit current.
AV = -25, CL = 1000pF AV = +25, CL = 10,000pF
The LT1226 can drive coaxial cable directly, but for best pulse fidelity the cable should be doubly terminated with a resistor in series with the output. Compensation The LT1226 has a typical gain bandwidth product of 1GHz which allows it to have wide bandwidth in high gain
TYPICAL APPLICATI
+
200 330pF
S
VIN
Lag Compensation
VIN
LT1226
VOUT
R2 50
-
5k
LT1226 TA03
1k AV = +6, f < 2MHz
300k 1 300k 8 LT1226 VOUT 25k
Compensation for Lower Closed-Loop Gains
RF RIN VIN RC
-
LT1226 VOUT
+
LT1226 TA05
R AV = - F ; RF 24 x (RIN || RC) RIN
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 circuits as described herein will not infringe on existing patent rights.
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LT1226 AI04
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UO
configurations (i.e., in a gain of 1000 it will have a bandwidth of about 1MHz). The amplifier is stable in a noise gain of 25 so the ratio of the output signal to the inverting input must be 1/25 or less. Straightforward gain configurations of +25 or -24 are stable, but there are a few configurations that allow the amplifier to be stable for lower signal gains (the noise gain, however, remains 25 or more). One example is the inverting amplifier shown in the typical applications sections below. The input signal has a gain of -RF/RIN to the output, but it is easily seen that this configuration is equivalent to a gain of -24 as far as the amplifier is concerned. Lag compensation can also be used to give a low frequency gain less than 25 with a high frequency gain of 25 or greater. The example below has a DC gain of 6, but an AC gain of +31. The break frequency of the RC combination across the amplifier inputs should be at least a factor of 10 less than the gain bandwidth of the amplifier divided by the high frequency gain (in this case 1/10 of 1GHz/31 or 3MHz).
Cable Driving
+
LT1226
R3 75
75 CABLE VOUT R4 75
-
R1 1.2k
VOS Null Loop
LT1226 TA04
VIN
+ -
10k 10k
100pF
25
-
LT1097 100pF
+
AV = 1001
LT1226 TA06
7
LT1226
SI PLIFIED SCHE ATIC
V+ 7 NULL 1 8
+IN
3
V-
4
LT1226 SS
PACKAGE DESCRIPTIO
0.300 - 0.320 (7.620 - 8.128)
0.009 - 0.015 (0.229 - 0.381) +0.025 0.325 -0.015 0.045 0.015 (1.143 0.381) 0.100 0.010 (2.540 0.254)
(
+0.635 8.255 -0.381
)
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
0- 8 TYP
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
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BIAS 1
2 -IN
BIAS 2 6 OUT
Dimensions 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
0.065 (1.651) TYP
8
7
6
5
0.125 (3.175) MIN
0.020 (0.508) MIN
0.250 0.010 (6.350 0.254)
0.018 0.003 (0.457 0.076)
1
2
3
4
N8 1291
TJ MAX 150C
JA 130C/W
S8 Package 8-Lead Plastic SOIC
8 0.053 - 0.069 (1.346 - 1.753) 0.004 - 0.010 (0.102 - 0.254) 0.228 - 0.244 (5.791 - 6.198) 0.014 - 0.019 (0.356 - 0.483) 0.050 (1.270) BSC
0.189 - 0.197 (4.801 - 5.004) 7 6 5
0.150 - 0.157 (3.810 - 3.988)
TJ MAX 150C
JA 220C/W
1
2
3
4
S8 1291
LT/GP 0692 10K REV 0
(c) LINEAR TECHNOLOGY CORPORATION 1992

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