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LM7171
SNOS760C – MAY 1999 – REVISED SEPTEMBER 2014
LM7171 Very High Speed, High Output Current, Voltage Feedback Amplifier
1 Features
3 Description
•
•
•
•
•
•
•
•
•
•
The LM7171 is a high speed voltage feedback
amplifier that has the slewing characteristic of a
current feedback amplifier, yet it can be used in all
traditional voltage feedback amplifier configurations.
The LM7171 is stable for gains as low as +2 or −1. It
provides a very high slew rate at 4100V/μs and a
wide unity-gain bandwidth of 200 MHz while
consuming only 6.5 mA of supply current. It is ideal
for video and high speed signal processing
applications such as HDSL and pulse amplifiers. With
100 mA output current, the LM7171 can be used for
video distribution, as a transformer driver or as a
laser diode driver.
1
(Typical Unless Otherwise Noted)
Easy-to-Use Voltage Feedback Topology
Very High Slew Rate: 4100 V/μs
Wide Unity-Gain Bandwidth: 200 MHz
−3 dB Frequency @ AV = +2: 220 MHz
Low Supply Current: 6.5 mA
High Open Loop Gain: 85 dB
High Output Current: 100 mA
Differential Gain and Phase: 0.01%, 0.02°
Specified for ±15V and ±5V Operation
2 Applications
•
•
•
•
•
•
•
•
HDSL and ADSL Drivers
Multimedia Broadcast Systems
Professional Video Cameras
Video Amplifiers
Copiers/Scanners/Fax
HDTV Amplifiers
Pulse Amplifiers and Peak Detectors
CATV/Fiber Optics Signal Processing
Operation on ±15 V power supplies allows for large
signal swings and provides greater dynamic range
and signal-to-noise ratio. The LM7171 offers low
SFDR and THD, ideal for ADC/DAC systems. In
addition, the LM7171 is specified for ±5 V operation
for portable applications.
The LM7171 is built on TI's advanced VIP™ III
(Vertically integrated PNP) complementary bipolar
process.
Device Information(1)
PART NUMBER
PACKAGE
BODY SIZE (NOM)
LM7171
SOIC (8)
4.90 mm × 3.91 mm
LM7171
PDIP (8)
9.81 mm × 6.35 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Simplified Schematic Diagram
Large Signal Pulse Response
AV = +2, VS = ±15V
Note: M1 and M2 are current mirrors.
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM7171
SNOS760C – MAY 1999 – REVISED SEPTEMBER 2014
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
4
4
4
4
5
6
7
8
9
Absolute Maximum Ratings ......................................
Handling Ratings.......................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
±15V DC Electrical Characteristics ..........................
±15V AC Electrical Characteristics ..........................
±5V DC Electrical Characteristics ............................
±5V AC Electrical Characteristics ............................
Typical Performance Characteristics ........................
Application and Implementation ........................ 18
7.1 Application Information............................................ 18
7.2
7.3
7.4
7.5
7.6
8
18
18
18
19
19
Power Supply Recommendations...................... 21
8.1
8.2
8.3
8.4
9
Circuit Operation .....................................................
Slew Rate Characteristic.........................................
Slew Rate Limitation ...............................................
Compensation For Input Capacitance ....................
Application Circuit ...................................................
Power Supply Bypassing ........................................
Termination .............................................................
Driving Capacitive Loads ........................................
Power Dissipation ...................................................
21
22
23
24
Layout ................................................................... 25
9.1 Layout Guidelines ................................................... 25
10 Device and Documentation Support ................. 26
10.1 Trademarks ........................................................... 26
10.2 Electrostatic Discharge Caution ............................ 26
10.3 Glossary ................................................................ 26
11 Mechanical, Packaging, and Orderable
Information ........................................................... 26
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision B (March 2013) to Revision C
Page
•
Changed data sheet flow and layout to conform with new TI standards. Added the following sections: Device
Information Table, Application and Implementation; Layout; Device and Documentation Support; Mechanical,
Packaging, and Ordering Information .................................................................................................................................... 1
•
Changed "Junction Temperature Range" to " Operating Temperature Range" and deleted TJ ............................................ 4
•
Deleted TJ = 25°C for Electrical Characteristics tables .......................................................................................................... 5
Changes from Revision A (March 2013) to Revision B
•
2
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 20
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5 Pin Configuration and Functions
8-Pin
Package D
(Top View)
Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
N/C
1
–
No Connection
-IN
2
I
Inverting Power Supply
+IN
3
I
Non-inverting Power Supply
V-
4
I
Supply Voltage
N/C
5
–
No Connection
OUTPUT
6
O
Output
V+
7
I
Supply Voltage
N/C
8
–
No Connection
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1)
MIN
MAX
UNIT
36
V
±10
V
Supply Voltage (V+–V−)
Differential Input Voltage
(2)
Output Short Circuit to Ground
(3)
Maximum Junction Temperature
(1)
(2)
(3)
(4)
Continuous
(4)
150
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Input differential voltage is applied at VS = ±15V.
Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in
exceeding the maximum allowed junction temperature of 150°C.
The maximum power dissipation is a function of TJ(MAX), RθJA, and TA. The maximum allowable power dissipation at any ambient
temperature is PD = (TJ(MAX)–TA)/RθJA. All numbers apply for packages soldered directly into a PC board.
6.2 Handling Ratings
Tstg
Storage temperature range
V(ESD)
(1)
(2)
Electrostatic discharge
(1)
MIN
MAX
UNIT
−65
+150
°C
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins (2)
2500
V
Human body model, 1.5 kΩ in series with 100 pF.
JEDEC document JEP155 states that 2500-V HBM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions (1)
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
UNIT
+85
°C
5.5V ≤ VS ≤ 36
Supply Voltage
−40
Operating Temperature Range: LM7171AI, LM7171BI
(1)
TYP
V
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not specified. For ensured specifications and the test
conditions, see the Electrical Characteristics.
6.4 Thermal Information
THERMAL METRIC (1)
RθJA
(1)
4
Junction-to-ambient thermal resistance
P (PDIP)
D (SOIC)
8 PINS
8 PINS
108°
172°
UNIT
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.5 ±15V DC Electrical Characteristics
Unless otherwise noted, all limits are specified for V+ = +15 V, V− = –15 V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at
the temperature extremes
PARAMETER
VOS
TEST CONDITIONS
Input Offset Voltage
TYP
(1)
LM7171AI
LIMIT (2)
LM7171BI
LIMIT (2)
0.2
1
3
mV
4
7
max
TC VOS
Input Offset Voltage Average
Drift
35
IB
Input Bias Current
2.7
IOS
Input Offset Current
RIN
Input Resistance
RO
Open Loop Output
Resistance
CMRR
Common Mode Rejection
Ratio
PSRR
0.1
Common Mode
40
Differential Mode
3.3
VCM = ±10V
105
Power Supply Rejection Ratio VS = ±15V to ±5V
Input Common-Mode Voltage
Range
AV
Large Signal Voltage Gain
(3)
CMRR > 60 dB
90
RL = 1 kΩ
85
Output Swing
81
RL = 1 kΩ
13.3
−13.2
RL = 100Ω
11.8
−10.5
Output Current (Open Loop)
(4)
IS
(1)
(2)
(3)
(4)
10
10
μA
12
12
max
4
4
μA
6
6
max
MΩ
Ω
85
75
dB
80
70
min
85
75
dB
80
70
min
±13.35
RL = 100Ω
ISC
μV/°C
15
VCM
VO
UNIT
Sourcing, RL = 100Ω
118
Sinking, RL = 100Ω
105
Output Current (in Linear
Region)
Sourcing, RL = 100Ω
100
Sinking, RL = 100Ω
100
Output Short Circuit Current
Sourcing
140
Sinking
135
Supply Current
6.5
V
80
75
dB
75
70
min
75
70
dB
70
66
min
13
13
12.7
12.7
V
min
−13
−13
−12.7
−12.7
10.5
10.5
V
9.5
9.5
min
−9.5
−9.5
−9
−9
max
105
105
mA
95
95
min
95
95
mA
90
90
max
V
max
V
mA
mA
8.5
8.5
mA
9.5
9.5
max
Typical values represent the most likely parametric norm.
All limits are specified by testing or statistical analysis.
Large signal voltage gain is the total output swing divided by the input signal required to produce that swing. For VS = ±15V, VOUT =
±5V. For VS = ±5V, VOUT = ±1V.
The open loop output current is specified, by the measurement of the open loop output voltage swing, using 100Ω output load.
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6.6 ±15V AC Electrical Characteristics
Unless otherwise noted, all limits are specified for V+ = +15V, V− = −15V, VCM = 0V, and RL = 1 kΩ.
PARAMETER
SR
Slew Rate
(3)
CONDITIONS
TYP (1)
AV = +2, VIN = 13 VPP
4100
AV = +2, VIN = 10 VPP
3100
Unity-Gain Bandwidth
−3 dB Frequency
AV = +2
LM7171AI
LIMIT (2)
LM7171BI
LIMIT (2)
UNIT
V/μs
200
MHz
220
MHz
50
Deg
φm
Phase Margin
ts
Settling Time (0.1%)
AV = −1, VO = ±5V
RL = 500Ω
42
ns
tp
Propagation Delay
AV = −2, VIN = ±5V,
RL = 500Ω
5
ns
AD
Differential Gain
φD
(4)
Differential Phase
0.01%
(4)
Second Harmonic Distortion (5)
Third Harmonic Distortion
(5)
0.02
Deg
fIN = 10 kHz
−110
dBc
fIN = 5 MHz
−75
dBc
fIN = 10 kHz
−115
dBc
fIN = 5 MHz
−55
dBc
en
Input-Referred Voltage Noise
f = 10 kHz
14
nV/√Hz
in
Input-Referred Current Noise
f = 10 kHz
1.5
pA/√Hz
(1)
(2)
(3)
(4)
(5)
6
Typical values represent the most likely parametric norm.
All limits are specified by testing or statistical analysis.
Slew Rate is the average of the raising and falling slew rates.
Differential gain and phase are measured with AV = +2, VIN = 1 VPP at 3.58 MHz and both input and output 75Ω terminated.
Harmonics are measured with VIN = 1 VPP, AV = +2 and RL = 100Ω.
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6.7 ±5V DC Electrical Characteristics
Unless otherwise noted, all limits are specified for V+ = +5V, V− = −5V, VCM = 0V, and RL = 1 kΩ. Boldface limits apply at the
temperature extremes
PARAMETER
VOS
TEST CONDITIONS
Input Offset Voltage
TYP (1)
LM7171AI
LIMIT (2)
LM7171BI
LIMIT (2)
0.3
1.5
3.5
mV
4
7
max
TC VOS
Input Offset Voltage Average
Drift
35
IB
Input Bias Current
3.3
IOS
Input Offset Current
RIN
Input Resistance
0.1
Common Mode
40
Differential Mode
3.3
RO
Output Resistance
CMRR
Common Mode Rejection
Ratio
VCM = ±2.5V
PSRR
Power Supply Rejection Ratio
VS = ±15V to ±5V
VCM
Input Common-Mode Voltage
Range
CMRR > 60 dB
AV
Large Signal Voltage Gain
(3)
RL = 1 kΩ
Output Swing
RL = 1 kΩ
RL = 100Ω
104
90
Output Current (Open Loop)
(4)
Sourcing, RL = 100Ω
Sinking, RL = 100Ω
ISC
Output Short Circuit Current
IS
Supply Current
(4)
10
10
μA
12
12
max
4
4
μA
6
6
max
MΩ
Ω
80
70
dB
75
65
min
85
75
dB
80
70
min
±3.2
78
V
75
70
dB
70
65
min
72
68
dB
67
63
min
3.2
3.2
3
3
−3.4
−3.2
−3.2
−3
−3
3.1
2.9
2.9
V
2.8
2.8
min
−2.9
−2.9
V
−2.8
−2.8
max
29
29
mA
28
28
min
29
29
mA
28
28
max
76
3.4
−3.0
(1)
(2)
(3)
μV/°C
15
RL = 100Ω
VO
UNIT
31
30
Sourcing
135
Sinking
100
6.2
V
min
V
max
mA
8
8
mA
9
9
max
Typical values represent the most likely parametric norm.
All limits are specified by testing or statistical analysis.
Large signal voltage gain is the total output swing divided by the input signal required to produce that swing. For VS = ±15V, VOUT =
±5V. For VS = ±5V, VOUT = ±1V.
The open loop output current is specified, by the measurement of the open loop output voltage swing, using 100Ω output load.
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6.8 ±5V AC Electrical Characteristics
Unless otherwise noted, all limits are specified for V+ = +5V, V− = −5V, VCM = 0V, and RL = 1 kΩ.
PARAMETER
SR
Slew Rate
TEST CONDITIONS
(3)
AV = +2, VIN = 3.5 VPP
Unity-Gain Bandwidth
−3 dB Frequency
AV = +2
TYP (1)
LM7171AI
LIMIT (2)
LM7171BI
LIMIT (2)
UNIT
950
V/μs
125
MHz
140
MHz
φm
Phase Margin
57
Deg
ts
Settling Time (0.1%)
AV = −1, VO = ±1V,
RL = 500Ω
56
ns
tp
Propagation Delay
AV = −2, VIN = ±1V,
RL = 500Ω
6
ns
(4)
AD
Differential Gain
φD
Differential Phase
0.02%
(5)
Second Harmonic Distortion
(6)
Third Harmonic Distortion (6)
0.03
Deg
fIN = 10 kHz
−102
dBc
fIN = 5 MHz
−70
dBc
fIN = 10 kHz
−110
dBc
fIN = 5 MHz
−51
dBc
en
Input-Referred Voltage Noise
f = 10 kHz
14
nV/√Hz
in
Input-Referred Current Noise
f = 10 kHz
1.8
pA/√Hz
(1)
(2)
(3)
(4)
(5)
(6)
8
Typical values represent the most likely parametric norm.
All limits are specified by testing or statistical analysis.
Slew Rate is the average of the raising and falling slew rates.
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not specified. For ensured specifications and the test
conditions, see the Electrical Characteristics.
Differential gain and phase are measured with AV = +2, VIN = 1 VPP at 3.58 MHz and both input and output 75Ω terminated.
Harmonics are measured with VIN = 1 VPP, AV = +2 and RL = 100Ω.
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6.9 Typical Performance Characteristics
unless otherwise noted, TA= 25°C
Figure 1. Supply Current vs. Supply Voltage
Figure 2. Supply Current vs. Temperature
Figure 3. Input Offset Voltage vs. Temperature
Figure 4. Input Bias Current vs. Temperature
Figure 5. Short Circuit Current vs. Temperature (Sourcing)
Figure 6. Short Circuit Current vs. Temperature (Sinking)
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
10
Figure 7. Output Voltage vs. Output Current
Figure 8. Output Voltage vs. Output Current
Figure 9. CMRR vs. Frequency
Figure 10. PSRR vs. Frequency
Figure 11. PSRR vs. Frequency
Figure 12. Open Loop Frequency Response
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
Figure 13. Open Loop Frequency Response
Figure 14. Gain-Bandwidth Product vs. Supply Voltage
Figure 15. Gain-Bandwidth Product vs. Load Capacitance
Figure 16. Large Signal Voltage Gain vs. Load
Figure 17. Large Signal Voltage Gain vs. Load
Figure 18. Input Voltage Noise vs. Frequency
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
12
Figure 19. Input Voltage Noise vs. Frequency
Figure 20. Input Current Noise vs. Frequency
Figure 21. Input Current Noise vs. Frequency
Figure 22. Slew Rate vs. Supply Voltage
Figure 23. Slew Rate vs. Input Voltage
Figure 24. Slew Rate vs. Load Capacitance
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
Figure 25. Open Loop Output Impedance vs. Frequency
Figure 26. Open Loop Output Impedance vs Frequency
Figure 27. Large Signal Pulse Response AV = −1, VS = ±15V
Figure 28. Large Signal Pulse Response AV = −1, VS = ±5V
Figure 29. Large Signal Pulse Response AV = +2, VS = ±15V
Figure 30. Large Signal Pulse Response AV = +2, VS = ±5V
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
14
Figure 31. Small Signal Pulse Response AV = −1, VS = ±15V
Figure 32. Small Signal Pulse Response AV = −1, VS = ±5V
Figure 33. Small Signal Pulse Response AV = +2, VS = ±15V
Figure 34. Small Signal Pulse Response AV = +2, VS = ±5V
Figure 35. Closed Loop Frequency Response vs. Supply
Voltage (AV = +2)
Figure 36. Closed Loop Frequency Response vs. Capacitive
Load (AV = +2)
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
Figure 37. Closed Loop Frequency Response vs. Capacitive
Load (AV = +2)
Figure 38. Closed Loop Frequency Response vs. Input
Signal Level (AV = +2)
Figure 39. Closed Loop Frequency Response vs. Input
Signal Level (AV = +2)
Figure 40. Closed Loop Frequency Response vs. Input
Signal Level (AV = +2)
Figure 41. Closed Loop Frequency Response vs. Input
Signal Level (AV = +2)
Figure 42. Closed Loop Frequency Response vs. Input
Signal Level (AV = +4)
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
Figure 43. Closed Loop Frequency Response vs. Input
Signal Level (AV = +4)
Figure 44. Closed Loop Frequency Response vs. Input
Signal Level (AV = +4)
Figure 45. Closed Loop Frequency Response vs. Input
Signal Level (AV = +4)
Figure 46. Total Harmonic Distortion vs. Frequency
Figure 47. Total Harmonic Distortion vs. Frequency
(1)
(1)
16
(1)
(1)
Figure 48. Undistorted Output Swing vs. Frequency
The THD measurement at low frequency is limited by the test instrument.
The THD measurement at low frequency is limited by the test instrument.
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Typical Performance Characteristics (continued)
unless otherwise noted, TA= 25°C
Figure 49. Undistorted Output Swing vs. Frequency
Figure 51. Harmonic Distortion vs. Frequency
(1)
Figure 50. Undistorted Output Swing vs. Frequency
Figure 52. Harmonic Distortion vs. Frequency
(1)
Figure 53. Maximum Power Dissipation vs. Ambient Temperature
(1)
(1)
The THD measurement at low frequency is limited by the test instrument.
The THD measurement at low frequency is limited by the test instrument.
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7 Application and Implementation
7.1 Application Information
The LM7171 is a very high speed, voltage feedback amplifier. It consumes only 6.5 mA supply current while
providing a unity-gain bandwidth of 200 MHz and a slew rate of 4100V/μs. It also has other great features such
as low differential gain and phase and high output current.
The LM7171 is a true voltage feedback amplifier. Unlike current feedback amplifiers (CFAs) with a low inverting
input impedance and a high non-inverting input impedance, both inputs of voltage feedback amplifiers (VFAs)
have high impedance nodes. The low impedance inverting input in CFAs and a feedback capacitor create an
additional pole that will lead to instability. As a result, CFAs cannot be used in traditional op amp circuits such as
photodiode amplifiers, I-to-V converters and integrators where a feedback capacitor is required.
7.2 Circuit Operation
The class AB input stage in LM7171 is fully symmetrical and has a similar slewing characteristic to the current
feedback amplifiers. In the LM7171 Simplified Schematic, Q1 through Q4 form the equivalent of the current
feedback input buffer, RE the equivalent of the feedback resistor, and stage A buffers the inverting input. The
triple-buffered output stage isolates the gain stage from the load to provide low output impedance.
7.3 Slew Rate Characteristic
The slew rate of LM7171 is determined by the current available to charge and discharge an internal high
impedance node capacitor. This current is the differential input voltage divided by the total degeneration resistor
RE. Therefore, the slew rate is proportional to the input voltage level, and the higher slew rates are achievable in
the lower gain configurations. A curve of slew rate versus input voltage level is provided in Typical Performance
Characteristics
When a very fast large signal pulse is applied to the input of an amplifier, some overshoot or undershoot occurs.
By placing an external resistor such as 1 kΩ in series with the input of LM7171, the bandwidth is reduced to help
lower the overshoot.
7.4 Slew Rate Limitation
If the amplifier's input signal has too large of an amplitude at too high of a frequency, the amplifier is said to be
slew rate limited; this can cause ringing in time domain and peaking in frequency domain at the output of the
amplifier.
In Typical Performance Characteristics, there are several curves of AV = +2 and AV = +4 versus input signal
levels. For the AV = +4 curves, no peaking is present and the LM7171 responds identically to the different input
signal levels of 30 mV, 100 mV and 300 mV.
For the AV = +2 curves, with slight peaking occurs. This peaking at high frequency (>100 MHz) is caused by a
large input signal at high enough frequency that exceeds the amplifier's slew rate. The peaking in frequency
response does not limit the pulse response in time domain, and the LM7171 is stable with noise gain of ≥+2.
18
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7.5 Compensation For Input Capacitance
The combination of an amplifier's input capacitance with the gain setting resistors adds a pole that can cause
peaking or oscillation. To solve this problem, a feedback capacitor with a value
CF > (RG × CIN)/RF
(1)
can be used to cancel that pole. For LM7171, a feedback capacitor of 2 pF is recommended. Figure 54 illustrates
the compensation circuit.
Figure 54. Compensating for Input Capacitance
7.6 Application Circuit
Figure 55. Fast Instrumentation Amplifier
Figure 56. Multivibrator
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Application Circuit (continued)
Figure 57. Pulse Width Modulator
Figure 58. Video Line Driver
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8 Power Supply Recommendations
8.1 Power Supply Bypassing
Bypassing the power supply is necessary to maintain low power supply impedance across frequency. Both
positive and negative power supplies should be bypassed individually by placing 0.01 μF ceramic capacitors
directly to power supply pins and 2.2 μF tantalum capacitors close to the power supply pins.
Figure 59. Power Supply Bypassing
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8.2 Termination
In high frequency applications, reflections occur if signals are not properly terminated. Figure 60 shows a
properly terminated signal while Figure 61 shows an improperly terminated signal.
Figure 60. Properly Terminated Signal
Figure 61. Improperly Terminated Signal
To minimize reflection, coaxial cable with matching characteristic impedance to the signal source should be
used. The other end of the cable should be terminated with the same value terminator or resistor. For the
commonly used cables, RG59 has 75Ω characteristic impedance, and RG58 has 50Ω characteristic impedance.
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8.3 Driving Capacitive Loads
Amplifiers driving capacitive loads can oscillate or have ringing at the output. To eliminate oscillation or reduce
ringing, an isolation resistor can be placed as shown in Figure 62. The combination of the isolation resistor and
the load capacitor forms a pole to increase stability by adding more phase margin to the overall system. The
desired performance depends on the value of the isolation resistor; the bigger the isolation resistor, the more
damped the pulse response becomes. For LM7171, a 50Ω isolation resistor is recommended for initial
evaluation. Figure 63 shows the LM7171 driving a 150 pF load with the 50Ω isolation resistor.
Figure 62. Isolation Resistor Used
to Drive Capacitive Load
Figure 63. The LM7171 Driving a 150 pF Load
with a 50 Ω Isolation Resistor
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8.4 Power Dissipation
The maximum power allowed to dissipate in a device is defined as:
PD = (TJ(MAX) − TA)/θJA
where
•
•
•
•
•
PD is the power dissipation in a device
TJ(max) is the maximum junction temperature
TA is the ambient temperature
RθJA is the thermal resistance of a particular package
(2)
For example, for the LM7171 in a SOIC-8 package, the maximum power dissipation at 25°C ambient
temperature is 730 mW.
Thermal resistance, R θJA, depends on parameters such as die size, package size and package material. The
smaller the die size and package, the higher RθJA becomes. The 8-pin DIP package has a lower thermal
resistance (108°C/W) than that of 8-pin SOIC (172°C/W). Therefore, for higher dissipation capability, use an 8pin DIP package.
The total power dissipated in a device can be calculated as:
PD = PQ + PL
where
•
PQ is the quiescent power dissipated in a device with no load connected at the output. PL is the power
dissipated in the device with a load connected at the output; it is not the power dissipated by the load.
Furthermore,
•
•
PQis the supply current × total supply voltage with no load
PL is the output current × (voltage difference between supply voltage and output voltage of the same side of
supply voltage)
(3)
For example, the total power dissipated by the LM7171 with VS = ±15V and output voltage of 10V into 1 kΩ is
PD= PQ + PL
= (6.5 mA) × (30V) + (10 mA) × (15V − 10V)
= 195 mW + 50 mW
= 245 mW
24
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(4)
(5)
(6)
(7)
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9 Layout
9.1 Layout Guidelines
9.1.1 Printed Circuit Board and High Speed Op Amps
There are many things to consider when designing PC boards for high speed op amps. Without proper caution, it
is very easy to have excessive ringing, oscillation and other degraded AC performance in high speed circuits. As
a rule, the signal traces should be short and wide to provide low inductance and low impedance paths. Any
unused board space needs to be grounded to reduce stray signal pickup. Critical components should also be
grounded at a common point to eliminate voltage drop. Sockets add capacitance to the board and can affect high
frequency performance. It is better to solder the amplifier directly into the PC board without using any socket.
9.1.2 Using Probes
Active (FET) probes are ideal for taking high frequency measurements because they have wide bandwidth, high
input impedance and low input capacitance. However, the probe ground leads provide a long ground loop that
will produce errors in measurement. Instead, the probes can be grounded directly by removing the ground leads
and probe jackets and using scope probe jacks.
9.1.3 Component Selection and Feedback Resistor
It is important in high speed applications to keep all component leads short. For discrete components, choose
carbon composition-type resistors and mica-type capacitors. Surface mount components are preferred over
discrete components for minimum inductive effect.
Large values of feedback resistors can couple with parasitic capacitance and cause undesirable effects such as
ringing or oscillation in high speed amplifiers. For LM7171, a feedback resistor of 510Ω gives optimal
performance.
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10 Device and Documentation Support
10.1 Trademarks
VIP is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
10.2 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
10.3 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
11 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
26
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PACKAGE OPTION ADDENDUM
www.ti.com
27-May-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
LM7171AIM
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 85
LM71
71AIM
LM7171AIM/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LM71
71AIM
Samples
LM7171AIMX/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LM71
71AIM
Samples
LM7171BIM
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 85
LM71
71BIM
LM7171BIM/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LM71
71BIM
Samples
LM7171BIMX/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LM71
71BIM
Samples
LM7171BIN/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 85
LM7171
BIN
Samples
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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