250A, 3MHz, 200V/s
Operational Amplifier
U
FEATURES DESCRIPTIO
C-LoadTM Op Amp Drives All Capacitive Loads
Unity-Gain Stable
Power Saving Shutdown Feature
Maximum Input Offset Voltage: 600V
Maximum Input Bias Current: 50nA
Maximum Input Offset Current: 15nA
Minimum DC Gain, RL = 2k: 30V/mV
Input Noise Voltage: 14nV/Hz
Settling Time to 0.1%, 10V Step: 700ns
Settling Time to 0.01%, 10V Step: 1.25s
Minimum Output Swing into 1k: 13V
Minimum Output Swing into 500: 3.4V
Specified at 2.5V, 5V and 15V
APPLICATIO S
Battery-Powered Systems
Wideband Amplifiers
Buffers
Active Filters
Data Acquisition Systems
Photodiode Amplifiers
U
TYPICAL APPLICATIO
The LT®1351 is a low power, high speed, high slew rate operational amplifier with outstanding AC and DC perfor- mance. The LT1351 features lower supply current, lower input offset voltage, lower input bias current and higher DC gain than devices with comparable bandwidth. The circuit combines the slewing performance of a current feedback amplifier in a true operational amplifier with matched high impedance inputs. The high slew rate en- sures that the large-signal bandwidth is not degraded. The amplifier is a single gain stage with outstanding settling characteristics which make the circuit an ideal choice for data acquisition systems. The output drives a 1k load to
13Vwith 15Vsuppliesanda 500loadto 3.4Von 5V
supplies. The amplifier is also stable with any capacitive load which makes it useful in buffer or cable driver applications.
The LT1351 is a member of a family of fast, high perfor- mance amplifiers using this unique topology and employ- ing Linear Technology Corporation’s advanced complementary bipolar processing. For dual and quad amplifier versions of the LT1351 see the LT1352/LT1353 data sheet. For higher bandwidth devices with higher supply current see the LT1354 through LT1365 data sheets. Singles, duals and quads of each amplifier are available.
, LTC and LT are registered trademarks of Linear Technology Corporation.
C-Load is a trademark of Linear Technology Corporation.
R1
50k
R2 R5
5k 1.1k
R4
50k
–
R3
5k
LT1351 –
– +
VIN
+
LT1351
+
VOUT
GAIN = [R4/R3][1 + (1/2)(R2/R1 + R3/R4) + (R2 + R3)/R5] = 102 TRIM R5 FOR GAIN
TRIM R1 FOR COMMON MODE REJECTION BW = 30kHz
1351 TA01 AV = –1 1351 TA02
Total Supply Voltage (V+ to V –) .............................. 36V
Differential Input Voltage (Transient Only, Note 1) ... 10V Input Voltage .......................................................... VS
Output Short-Circuit Duration (Note 2) ........... Indefinite
Operating Temperature Range ................ – 40C to 85C
Specified Temperature Range (Note 6) .....– 40C to 85C Maximum Junction Temperature (See Below)
Plastic Package ................................................ 150C
Storage Temperature Range ................. – 65C to 150C
Lead Temperature (Soldering, 10 sec) .................. 300C
TOP VIEW NULL 1 8 NULL –IN 2 7 V+ +IN 3 6 VOUT V– 4 5 SHDN MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 250C/ W | ORDER PART NUMBER | TOP VIEW NULL 1 8 NULL – IN 2 7 V+ +IN 3 6 VOUT V– 4 5 SHDN N8 PACKAGE S8 PACKAGE 8-LEAD PDIP 8-LEAD PLASTIC SO TJMAX = 150C, JA = 130C/ W (N8) TJMAX = 150C, JA = 190C/ W (S) | ORDER PART NUMBER |
LT1351CMS8 | LT1351CN8 LT1351CS8 | ||
MS8 PART MARKING | S8 PART MARKING | ||
LTBT | 1351 |
Consult factory for Industrial and Military grade parts.
SYMBOL | PARAMETER | CONDITIONS | VSUPPLY | MIN | TYP | MAX | UNITS |
VOS | Input Offset Voltage | 15V 5V | 0.2 0.2 | 0.6 0.6 | mV mV | ||
2.5V | 0.3 | 0.8 | mV | ||||
IOS | Input Offset Current | 2.5V to 15V | 5 | 15 | nA | ||
IB | Input Bias Current | 2.5V to 15V | 20 | 50 | nA | ||
en | Input Noise Voltage | f = 10kHz | 2.5V to 15V | 14 | nV/Hz | ||
in | Input Noise Current | f = 10kHz | 2.5V to 15V | 0.5 | pA/Hz | ||
RIN | Input Resistance | VCM = 12V Differential | 15V 15V | 300 | 600 20 | M M | |
CIN | Input Capacitance | 15V | 3 | pF | |||
Positive Input Voltage Range | 15V | 12.0 | 13.5 | V | |||
5V | 2.5 | 3.5 | V | ||||
2.5V | 0.5 | 1.0 | V | ||||
Negative Input Voltage Range | 15V | – 13.5 | – 12.0 | V | |||
5V | – 3.5 | – 2.5 | V | ||||
2.5V | – 1.0 | – 0.5 | V | ||||
CMRR | Common Mode Rejection Ratio | VCM = 12V VCM = 2.5V VCM = 0.5V | 15V 5V 2.5V | 80 78 68 | 94 86 77 | dB dB dB | |
PSRR | Power Supply Rejection Ratio | VS = 2.5V to 15V | 90 | 106 | dB |
SYMBOL | PARAMETER | CONDITIONS | VSUPPLY | MIN | TYP MAX | UNITS |
AVOL | Large-Signal Voltage Gain | VOUT = 12V, RL = 5k VOUT = 10V, RL = 2k VOUT = 10V, RL = 1k VOUT = 2.5V, RL = 5k VOUT = 2 .5V, RL = 2k VOUT = 2.5V, RL = 1k VOUT = 1V, RL = 5k | 15V 15V 15V 5V 5V 5V 2.5V | 40 30 20 30 25 15 20 | 80 60 40 60 50 30 40 | V/mV V/mV V/mV V/mV V/mV V/mV V/mV |
VOUT | Output Swing | RL = 5k, VIN = 10mV RL = 2k, VIN = 10mV RL = 1k, VIN = 10mV RL = 1k, VIN = 10mV RL= 500, VIN = 10mV RL = 5k, VIN = 10mV | 15V 15V 15V 5V 5V 2.5V | 13.5 13.4 13.0 3.5 3.4 1.3 | 14.0 13.8 13.4 4.0 3.8 1.7 | V V V V V V |
IOUT | Output Current | VOUT = 13V VOUT = 3.4V | 15V 5V | 13.0 6.8 | 13.4 7.6 | mA mA |
ISC | Short-Circuit Current | VOUT = 0V, VIN = 3V | 15V | 30 | 45 | mA |
SR | Slew Rate | AV = – 1, RL = 5k (Note 3) | 15V 5V | 120 30 | 200 50 | V/s V/s |
Full-Power Bandwidth | 10V Peak (Note 4) 3V Peak (Note 4) | 15V 5V | 3.2 2.6 | MHz MHz | ||
GBW | Gain Bandwidth | f = 200kHz, RL = 10k | 15V 5V 2.5V | 2.0 1.8 | 3.0 2.7 2.5 | MHz MHz MHz |
tr, tf | Rise Time, Fall Time | AV = 1, 10% to 90%, 0.1V | 15V 5V | 46 53 | ns ns | |
Overshoot | AV = 1, 0.1V | 15V 5V | 13 16 | % % | ||
Propagation Delay | 50% VIN to 50% VOUT, 0.1V | 15V 5V | 41 52 | ns ns | ||
ts | Settling Time | 10V Step, 0.1%, AV = – 1 10V Step, 0.01%, AV = – 1 5V Step, 0.1%, AV = – 1 5V Step, 0.01%, AV = – 1 | 15V 15V 5V 5V | 700 1250 950 1400 | ns ns ns ns | |
RO | Output Resistance | AV = 1, f = 20kHz | 15V | 1.5 | | |
ISHDN | Shutdown Input Current | SHDN = VEE + 0.1V SHDN = VCC | 15V 15V | – 10 0.1 2 | A A | |
IS | Supply Current | SHDN = VEE + 0.1V | 15V 5V 5V | 250 330 220 300 10 | A A A |
SYMBOL | PARAMETER | CONDITIONS | VSUPPLY | MIN TYP MAX | UNITS |
VOS | Input Offset Voltage | 15V 5V 2.5V | 0.8 0.8 1.0 | mV mV mV | |
Input VOS Drift | (Note 5) | 2.5V to 15V | 3 8 | V/C | |
IOS | Input Offset Current | 2.5V to 15V | 20 | nA | |
IB | Input Bias Current | 2.5V to 15V | 75 | nA |
SYMBOL | PARAMETER | CONDITIONS | VSUPPLY | MIN | TYP | MAX | UNITS |
CMRR | Common Mode Rejection Ratio | VCM = 12V VCM = 2.5V VCM = 0.5V | 15V 5V 2.5V | 78 77 67 | dB dB dB | ||
PSRR | Power Supply Rejection Ratio | VS = 2.5V to 15V | 89 | dB | |||
AVOL | Large-Signal Voltage Gain | VOUT = 12V, RL = 5k VOUT = 10V, RL = 2k | 15V 15V 5V 5V 5V 2.5V | 25 20 20 15 10 15 | V/mV V/mV V/mV V/mV V/mV V/mV | ||
VOUT = 2.5V, RL = 5k | |||||||
VOUT = 2 .5V, RL = 2k | |||||||
VOUT = 2.5V, RL = 1k | |||||||
VOUT = 1V, RL = 5k | |||||||
VOUT | Output Swing | RL = 5k, VIN = 10mV RL = 2k, VIN = 10mV | 15V 15V 15V 5V 5V 2.5V | 13.4 13.3 12.0 3.4 3.3 1.2 | V V V V V V | ||
RL = 1k, VIN = 10mV | |||||||
RL = 1k, VIN = 10mV | |||||||
RL= 500, VIN = 10mV | |||||||
RL = 5k, VIN = 10mV | |||||||
IOUT | Output Current | VOUT = 12V VOUT = 3.3V | 15V 5V | 12.0 6.6 | mA mA | ||
ISC | Short-Circuit Current | VOUT = 0V, VIN = 3V | 15V | 24 | mA | ||
SR | Slew Rate | AV = – 1, RL = 5k (Note 3) | 15V | 100 | V/s | ||
5V | 21 | V/s | |||||
GBW | Gain Bandwidth | f = 200kHz, RL = 10k | 15V | 1.8 | MHz | ||
5V | 1.6 | MHz | |||||
ISHDN | Shutdown Input Current | SHDN = VEE + 0.1V SHDN = VCC | 15V 15V | – 20 | 3 | A A | |
IS | Supply Current | 15V 5V | 380 355 | A A | |||
SHDN = VEE + 0.1V | 5V | 20 | A |
SYMBOL | PARAMETER | CONDITIONS | VSUPPLY | MI | N TYP | MAX | UNITS |
VOS | Input Offset Voltage | 15V 5V | 1.0 1.0 | mV mV | |||
2.5V | 1.2 | mV | |||||
Input VOS Drift | (Note 5) | 2.5V to 15V | 3 | 8 | V/C | ||
IOS | Input Offset Current | 2.5V to 15V | 30 | nA | |||
IB | Input Bias Current | 2.5V to 15V | 100 | nA | |||
CMRR | Common Mode Rejection Ratio | VCM = 12V | 15V 5V 2.5V | 76 76 66 | dB dB dB | ||
VCM = 2.5V | |||||||
VCM = 0.5V | |||||||
PSRR | Power Supply Rejection Ratio | VS = 2.5V to 15V | 87 | dB | |||
AVOL | Large-Signal Voltage Gain | VOUT = 12V, RL = 5k VOUT = 10V, RL = 2k | 15V 15V 5V 5V 5V 2.5V | 20 15 15 10 8 10 | V/mV V/mV V/mV V/mV V/mV V/mV | ||
VOUT = 2.5V, RL = 5k | |||||||
VOUT = 2 .5V, RL = 2k | |||||||
VOUT = 2.5V, RL = 1k | |||||||
VOUT = 1V, RL = 5k |
SYMBOL | PARAMETER | CONDITIONS | VSUPPLY | MIN | TYP | MAX | UNITS |
VOUT | Output Swing | RL = 5k, VIN = 10mV RL = 2k, VIN = 10mV | 15V 15V 15V 5V 5V 2.5V | 13.3 13.2 10.0 3.3 3.2 1.1 | V V V V V V | ||
RL = 1k, VIN = 10mV | |||||||
RL = 1k, VIN = 10mV | |||||||
RL= 500, VIN = 10mV | |||||||
RL = 5k, VIN = 10mV | |||||||
IOUT | Output Current | VOUT = 10V VOUT = 3.2V | 15V 5V | 10.0 6.4 | mA mA | ||
ISC | Short-Circuit Current | VOUT = 0V, VIN = 3V | 15V | 20 | mA | ||
SR | Slew Rate | AV = – 1, RL = 5k (Note 3) | 15V | 50 | V/s | ||
5V | 15 | V/s | |||||
GBW | Gain Bandwidth | f = 200kHz, RL = 10k | 15V | 1.6 | MHz | ||
5V | 1.4 | MHz | |||||
ISHDN | Shutdown Input Current | SHDN = VEE + 0.1V SHDN = VCC | 15V 15V | – 30 | 5 | A A | |
IS | Supply Current | 15V 5V | 390 380 | A A | |||
SHDN = VEE + 0.1V | 5V | 30 | A |
Note 1: Differential inputs of 10V are appropriate for transient operation only, such as during slewing. Large, sustained differential inputs will cause excessive power dissipation and may damage the part. See Input Considerations in the Applications Information section of this data sheet for more details.
Note 3: Slew rate is measured between 8V on the output with 12V input for 15V supplies and 2V on the output with 3V input for 5V supplies.
Note 4: Full-power bandwidth is calculated from the slew rate measurement: FPBW = (Slew Rate)/2VP.
Note 6: The LT1351 is designed, characterized and expected to meet these extended temperature limits, but is not tested at – 40C and at 85C. Guaranteed I grade parts are available; consult factory.
350
125C
300
V+
–0.5
COMMON MODE RANGE (V)
–1.0
30
TA = 25C VS = 15V
INPUT BIAS CURRENT (nA)
20 I + + I –
SUPPLY CURRENT (A)
250
–1.5
–2.0
IB =
10
B B
2
–55C
25C
200
150
100
0
5 10 15 20
2.0
TA = 25C | |||
VOS = 1mV | |||
1.5
1.0
0.5
V–
0
5 10 15 20
0
–10
–20
–15
–10 –5 0 5
10 15
SUPPLY VOLTAGE (V)
1351 G01
SUPPLY VOLTAGE (V)
1351 G02
INPUT COMMON MODE VOLTAGE (V)
1351 G03
VS = 15V | ||||||
IB = | I + + I – B B 2 | |||||
40
36
INPUT BIAS CURRENT (nA)
32
28
24
20
16
12
8
4
0
100
INPUT VOLTAGE NOISE (nV/Hz)
10
1
TA = 25C VS = 15V AV = 101 RS = 100k
en
in
10
1
0.1
110
INPUT CURRENT NOISE (pA/Hz)
OPEN-LOOP GAIN (dB)
100
90
80
70
60
TA = 25C
VS = 15V
VS = 5V
–50
–25 0
25 50 75
100 125
1 10 100
1k 10k
10 100 1k 10k
TEMPERATURE (C)
1351 G04
FREQUENCY (Hz)
1351 G05
LOAD RESISTANCE ()
1351 G06
100
V+
V+
– 0.5
VS = 5V
85C
OUTPUT VOLTAGE SWING (V)
VS = 15V VO = 12V RL = 5k | ||||||
99 –1
OPEN-LOOP GAIN (dB)
98 –2
–3
97
3
TA = 25C VIN = 10mV
RL = 1k
RL = 2k
–1.0
OUTPUT VOLTAGE SWING (V)
–1.5
–2.0
2.0
VIN = 10mV
25C
85C
25C
–40C
25C
–40C 85C
96
95
94
–50
–25 0
25 50
75 100 125
2
1
V–
0 5 10
RL = 1k RL = 2k
15 20
1.5 –40C
1.0
0.5
V–
–20 –15
–10
–40C
25C
85C
– 5 0 5
10 15 20
TEMPERATURE (C)
OUTPUT SHORT-CIRCUIT CURRENT (mA)
VS = 15V | ||||||
SINK | ||||||
SOURCE | ||||||
60
55
50
45
40
35
30
25
1351 G07
10
8
6
OUTPUT STEP (V)
4
2
0
–2
–4
–6
–8
–10
SUPPLY VOLTAGE (V)
10mV | 1mV | |||||||
1 | 0mV | 1mV | VS = 15V AV = 1 OUTPUT FILTER: 1.6MHz LPF | |||||
1351 G08
10
8
6
OUTPUT STEP (V)
4
2
0
–2
–4
–6
–8
–10
OUTPUT CURRENT (mA)
10mV | 1mV | ||||||||
10mV | 1mV | ||||||||
VS = 15V AV = –1 RG = RF = 2k CF = 5pF RL = 2k | |||||||||
1351 G09
–50
–25 0
25 50
75 100 125
0.7 0.8
0.9 1
1.1 1.2
1.3 1.4 1.5
1.6
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
TEMPERATURE (C)
1351 G10
SETTLING TIME (s)
1351 G11
SETTLING TIME (s)
1351 G12
70
TA = 25C
120
1000
TA = 25C
10
OUTPUT IMPEDANCE ()
8 TA = 25C
60 PHASE
50
VS = 15V
AV = –1
RF = RG = 5k
PHASE (DEG)
VS = 15V
100
80
100
VS = 15V
AV = 100
AV = 10 AV = 1
VS = 15V
6 AV = –1
4 RFB = RG = 5k C = 500pF
C = 100pF
C = 5000pF
C = 1000pF
GAIN (dB)
40
30
20
10
0
–10
VS = 5V VS = 5V GAIN
60
40
20
0
–20
–40
10
1
0.1
0.01
2
GAIN (dB)
0
–2
–4
–6
–8
–10
C = 10pF
1k 10k 100k 1M FREQUENCY (Hz)
10M
100M
1351 G13
1k 10k
100k 1M 10M FREQUENCY (Hz)
1351 G14
10k
100k 1M 10M FREQUENCY (Hz)
1351 G15
4.50
4.25
GAIN BANDWIDTH (MHz)
4.00
3.75
3.50
3.25
3.00
2.75
50
VS = 15V 48
VS = 5V 46
PHASE MARGIN (DEG)
PHASE MARGIN 44
42
GAIN BANDWIDTH 40
38
VS = 15V 36
5
TA = 25C
4 AV = 1
3 RL = 5k
2
GAIN (dB)
1
0
–1
–2 15V
5
TA = 25C
4 AV = –1
3 RL = RG = 5k
2
GAIN (dB)
1
0
–1
–2
2.50
2.25
2.00
VS = 5V
34 –3
32 –4
30 –5
5V
2.5V 3
–4
–5
15V
5V
2.5V
–50
–25 0
25 50 75
100 125
10k
100k 1M 10M
10k
100k 1M 10M
TEMPERATURE (C)
1351 G16
FREQUENCY (Hz)
1351 G17
FREQUENCY (Hz)
1351 G18
4.50
4.25
GAIN BANDWIDTH (MHz)
4.00
3.75
3.50
3.25
3.00
2.75
2.50
2.25
2.00
TA = 25C | |||
PHASE MARGIN | |||
GAIN BANDWIDTH | |||
50
48
46
44
42
40
38
36
34
32
30
120
POWER SUPPLY REJECTION RATIO (dB)
100
PHASE MARGIN (DEG)
80
60
40
20
0
TA = 25C VS = 15V | |||||
– PSRR = +PSRR | |||||
COMMON MODE REJECTION RATIO (dB)
120
100
80
60
40
20
0
TA = 25C VS = 15V
0 5 10 15 20
10 100 1k 10k 100k
1M 10M
100
1k 10k 100k 1M
10M
SUPPLY VOLTAGE (V)
FREQUENCY (Hz)
FREQUENCY (Hz)
1351 G19
1351 G20
1351 G21
200
TA = 25C
250
TA = 25C VS = 15V AV = –1 RFB = RG = 5k SR = (SR+ + SR–)/2 | ||||||
200
AV = –1
SLEW RATE (V/s)
150
100
50
0
AV = –1
RF = RG = 5k
SR = (SR+ + SR–)/2
200
SLEW RATE (V/s)
150
100
50
0
VS = 15V
VS = 5V
RF = RG = RL = 5k SR = (SR+ + SR–)/2
175
SLEW RATE (V/s)
150
125
100
75
50
25
0
0 5 10 15
–50 –25 0
25 50 75
100 125
0 4 8
12 16
20 24
SUPPLY VOLTAGE (V)
1
TOTAL HARMONIC DISTORTION (%)
TA = 25C VS = 15V
1351 G22
TEMPERATURE (C)
30
1351 G23
AV = –1
INPUT LEVEL (VP-P)
10
9
1351 G24
0.1
0.01
0.001
RL = 5k
VO = 2VP-P
AV = –1
AV = 1
25
OUTPUT VOLTAGE (VP-P)
20
15
10
5 VS = 15V RL = 5k THD = 1%
0
AV = 1
8
AV = 1
OUTPUT VOLTAGE (VP-P)
7
AV = –1
6
5
4
3
2 VS = 5V
1 RL = 5k THD = 1%
0
10 100 1k 10k 100k FREQUENCY (Hz)
1351 G25
10k
100k 1M
FREQUENCY (Hz)
1351 G26
10k
100k 1M
FREQUENCY (Hz)
1351 G27
–30
100
TA = 25C VS = 15V RL = 5k | ||||||||||||||
AV = 1 | ||||||||||||||
AV = –1 | ||||||||||||||
100
HARMONIC DISTORTION (dB)
–40
–50
–60
–70
–80
VS = 15V AV = 1 RL = 5k VO = 2VP-P | ||||||||
3RD HARMONIC | ||||||||
2ND HARMONIC | ||||||||
–90
90 VS = 15V 90
SUPPLY CURRENT (A)
80 80
VSHDN = VEE + 0.2
OVERSHOOT (%)
70 70
60 60
1
50 VSHDN = VEE + 0. 50
40 40
30 30
EE
20 VSHDN = V 20
10 10
0 0
100k
1M 50
–25 0
25 50 75
100 125
10p
100p 1n 10n 0.1 1
FREQUENCY (Hz)
1351 G28
TEMPERATURE (C)
1351 G29
CAPACITIVE LOAD (F)
1351 G30
1351 G31
1351 G32
1351 G33
1351 G34
1351 G35
1351 G36
The LT1351 may be inserted directly into many high speed amplifier applications improving both DC and AC performance, provided that the nulling circuitry is re- moved. The suggested nulling circuit for the LT1351 is shown in Figure 1.
V+
0.1F
The LT1351 amplifier is easy to apply and tolerant of less than ideal layouts. For maximum performance (for ex- ample 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). For details see Design Note 50.
3 +
2 –
LT1351
7 6
4
The parallel combination of the feedback resistor and gain setting resistor on the inverting input can combine with
8
1
100k
V–
0.1F
1351 F01
the input capacitance to form a pole which can cause peaking or even oscillations. For feedback resistors greater than 10k, 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 one and a large feedback resistor is used, CF should be greater than or equal to CIN. An example would bean I-to-V converter asshowninthe Typical Applications section.
The LT1351 is 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. Graphs of Fre- quency Response vs Capacitive Load, Capacitive Load Handling and the transient response photos clearly show these effects.
Each of the LT1351 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 NPN/PNP 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 transient differential input volt- ages up to 10V without damage and need no clamping or source resistance for protection. Differential inputs, how- ever, generate large supply currents (tens of mA) as required for high slew rates. If the device is used with sustained differential inputs, the average supply current will increase, excessive power dissipation will result and the part may be damaged. The part should not be used as a comparator, peak detector or other open-loop applica- tion with large, sustained differential inputs. Under normal, closed-loop operation, an increase of power dissipation is only noticeable in applications with large slewing outputs and is proportional to the magnitude of the differential input voltage and the percent of the time that the inputs are apart. Measure the average supply current for the application in order to calculate the power dissipation.
The LT1351 has a Shutdown pin for conserving power. When this pin is open or 2V above the negative supply the part operates normally. When pulled down to V– the supply current will drop to about 10A. The current out of the Shutdown pin is also typically 10A. In shutdown the
amplifier output is not isolated from the inputs so the LT1351 cannot be used in multiplexing applications using the shutdown feature.
A level shift application is shown in the Typical Applica- tions section so that a ground-referenced logic signal can control the Shutdown pin.
The LT1351 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 R1, a 1k resistor. The input voltage appears across the resistor generating currents which are mirrored into the high impedance node and
compensation capacitor CT. Complementary followers form an output stage which buffers the gain node from the load. The output devices Q19 and Q22 are connected to form a composite PNP and composite NPN.
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 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 outputstepinunitygainhasa 10 times greater input step. The curve of Slew Rate vs Input Level illustrates this relationship.
Capacitive load compensation is provided by the RC, CC network which is bootstrapped across the output stage. When the amplifier is driving a light load the network has no effect. 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 and a zero is created by the RC combination, both of
which improve the phase margin. The design ensures that even for very large load capacitances the total phase lag can never exceed 180 degrees (zero phase margin) and the amplifier remains stable.
V+
Q10
Q11
Q12
R2
C1 Q20
R3 Q21
Q7 R1
Q9
Q3
Q17
R6
Q19
CC
–IN
V–
Q5 Q6
1k
Q8 Q4
Q2 Q1
Q14
+IN
Q13
CT
Q15
RC
Q18
R7
Q16
C2
Q23
Q22
R4
Q24 R5
OUTPUT
1351 SS
VIN
4.64k
13.3k
4.64k
470pF
–
5.49k
11.3k
5.49k
220pF
2200pF
LT1351
+
4700pF
–
LT1351
+
VOUT
1351 TA03
3 +
LT1351 6
SHDN
1N4148
1M G
2 –
S SST177
D G
1M
5
S SST177 D
V – 1351 TA04
12
DAC
INPUTS
5k
565A TYPE
10pF
–
LT1351
+
VOUT
A
VOS + IOS (5k) + VOUT < 0.5LSB 5k
VOL
1351 TA05
(LTC DWG # 05-08-1660)
0.118 0.004*
8 7 6 5
(3.00 0.102)
0.192 0.004
(4.88 0.10)
0.118 0.004**
(3.00 0.102)
1 2 3 4
0.007
(0.18)
0 – 6 TYP
SEATING
0.040 0.006
(1.02 0.15)
0.034 0.004
(0.86 0.102)
0.021 0.006
PLANE
0.012
0.006 0.004
(0.53 0.015)
(0.30) REF
0.0256
(0.65) TYP
(0.15 0.102)
MSOP (MS8) 1197
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
(LTC DWG # 05-08-1510)
55 0.015* 77 0.381) | (10.160) MAX | ||||||||
8 | 7 | 6 | 5 | ||||||
1 | 2 | 3 | 4 |
0.2
(6.4
0.400*
0.300 – 0.325
(7.620 – 8.255)
0.045 – 0.065
(1.143 – 1.651)
0.130 0.005
(3.302 0.127)
0.009 – 0.015
(0.229 – 0.381)
0.325 +0.035
–0.381
8.255 +0.889
0.065
(1.651) TYP
–0.015
0.100 0.010
(2.540 0.254)
0.125
(3.175) MIN
0.018 0.003
(0.457 0.076)
0.020
(0.508) MIN
N8 1197
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
(LTC DWG # 05-08-1610)
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 2 3 4
0.010 – 0.020 45
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0– 8 TYP
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.016 – 0.050
0.406 – 1.270
0.014 – 0.019
(0.355 – 0.483)
0.050
(1.270) 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
SO8 0996
15
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 represen- tation that the interconnection of its circuits asdescribedherein will not infringe on existing patent rights.
VIN
LT1351
LTC201 LT1351
2000pF
VOUT
DROOP: 20nA/2000pF = 10mV/ms ACQUISITION TIME: 10V, 0.1% = 2s
CHARGE INJECTION ERROR: 8pC/2000pF = 4mV
1351 TA06
PART NUMBER | DESCRIPTION | COMMENTS |
LT1352/LT1353 | Dual/Quad 250A, 3MHz, 200V/s Op Amp | Good DC Precision, Stable with All Capacitive Loads |
LT1354 | 1mA, 12MHz, 400V/s Op Amp | Good DC Precision, Stable with All Capacitive Loads |
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900●FAX:(408) 434-0507 ●www.linear-tech.com
1351fa LT/TP 0498 REV A 2K • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1996
Mouser Electronics
Authorized Distributor
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