LM7171AIN [NSC]
Very High Speed, High Output Current, Voltage Feedback Amplifier; 超高速，高输出电流，电压反馈放大器
| 型号： | LM7171AIN |
| 厂家： | 
National Semiconductor |
| 描述： | Very High Speed, High Output Current, Voltage Feedback Amplifier |
| 文件： | 总20页 (文件大小：617K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
May 1999
LM7171
Very High Speed, High Output Current, Voltage
Feedback Amplifier
n Easy-To-Use Voltage Feedback Topology
n Very High Slew Rate: 4100V/µs
The LM7171 is a high speed voltage feedback amplifier that
n Wide Unity-Gain Bandwidth: 200 MHz
General Description
has the slewing characteristic of a current feedback ampli-
=
@
n −3 dB Frequency AV +2: 220 MHz
fier; yet it can be used in all traditional voltage feedback am-
plifier 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 consum-
ing 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.
n Low Supply Current: 6.5 mA
n High Open Loop Gain: 85 dB
n High Output Current: 100 mA
n Differential Gain and Phase: 0.01%, 0.02˚
±
±
n Specified for 15V and 5V Operation
Applications
n HDSL and ADSL Drivers
n Multimedia Broadcast Systems
n Professional Video Cameras
n Video Amplifiers
±
Operation on 15V 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 5V operation for portable applications.
n Copiers/Scanners/Fax
n HDTV Amplifiers
™
The LM7171 is built on National’s advanced VIP III (Verti-
cally integrated PNP) complementary bipolar process.
n Pulse Amplifiers and Peak Detectors
n CATV/Fiber Optics Signal Processing
Features
(Typical Unless Otherwise Noted)
Typical Performance
Connection Diagrams
Large Signal Pulse Response
8-Pin DIP/SO
=
=
±
AV +2, VS
15V
DS012385-2
Top View
16-Pin Wide Body SO
DS012385-1
DS012385-3
Top View
™
VIP is a trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS012385
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Ordering Information
Package
Temperature Range
Industrial
Transport
Media
NSC
Drawing
Military
−40˚C to +85˚C
−55˚C to +125˚C
8-Pin DIP
LM7171AIN, LM7171BIN
Rails
Rails
N08E
J08A
8-Pin CDIP
LM7171AMJ-QML
LM7171AMJ-QMLV
5962-95536
5962-95536
10-Pin Ceramic
SOIC
LM7171AMWG-QML
LM7171AMWG-QMLV
Trays
WG10A
M08A
8-Pin
LM7171AIM, LM7171BIM
LM7171AIMX, LM7171BIMX
LM7171AIWM, LM7171BIWM
LM7171AWMX, LM7171BWMX
Rails
Small Outline
16-Pin
Tape and Reel
Rails
M16B
Small Outline
Tape and Reel
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2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Junction Temperature
(Note 4)
150˚C
Operating Ratings (Note 1)
ESD Tolerance (Note 2)
Supply Voltage (V+–V−)
Differential Input Voltage (Note 11)
Output Short Circuit to Ground
(Note 3)
2.5 kV
36V
Supply Voltage
5.5V ≤ VS ≤ 36V
Junction Temperature Range
LM7171AI, LM7171BI
±
10V
−40˚C ≤ TJ ≤ +85˚C
Thermal Resistance (θJA
)
Continuous
N Package, 8-Pin Molded DIP
M Package, 8-Pin Surface Mount
M Package, 16-Pin Surface Mount
108˚C/W
172˚C/W
95˚C/W
Storage Temperature Range
−65˚C to +150˚C
±
15V DC Electrical Characteristics
+
−
=
=
= = =
−15V, VCM 0V, and RL 1 kΩ. Boldface
Unless otherwise specified, all limits guaranteed for TJ 25˚C, V
limits apply at the temperature extremes
+15V, V
Symbol
Parameter
Conditions
Typ
(Note 5)
LM7171AI
LM7171BI
Units
Limit
Limit
(Note 6)
(Note 6)
VOS
Input Offset Voltage
0.2
35
1
3
mV
max
4
7
TC VOS
Input Offset Voltage
Average Drift
µV/˚C
IB
Input Bias Current
2.7
0.1
10
12
4
10
12
4
µA
max
µA
IOS
Input Offset Current
Input Resistance
6
6
max
MΩ
RIN
Common Mode
40
3.3
15
Differential Mode
RO
Open Loop Output
Resistance
Ω
=
±
CMRR
PSRR
VCM
AV
Common Mode
Rejection Ratio
Power Supply
VCM
10V
105
90
85
80
85
80
75
70
75
70
dB
min
dB
min
V
=
±
±
15V to 5V
VS
Rejection Ratio
Input Common-Mode
Voltage Range
Large Signal Voltage
Gain (Note 7)
>
±
CMRR 60 dB
13.35
85
=
RL 1 kΩ
80
75
75
70
dB
min
dB
=
RL 100Ω
81
75
70
70
66
min
V
=
VO
Output Swing
RL 1 kΩ
13.3
13
13
12.7
−13
−12.7
10.5
9.5
−9.5
−9
12.7
−13
−12.7
10.5
9.5
−9.5
−9
min
V
−13.2
11.8
−10.5
118
max
V
=
RL 100Ω
min
V
max
mA
min
mA
max
=
Output Current
(Open Loop)
(Note 8)
Sourcing, RL 100Ω
105
95
105
95
=
Sinking, RL 100Ω
105
95
95
90
90
3
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±
15V DC Electrical Characteristics (Continued)
+
−
=
=
= = =
−15V, VCM 0V, and RL 1 kΩ. Boldface
Unless otherwise specified, all limits guaranteed for TJ 25˚C, V
limits apply at the temperature extremes
+15V, V
Symbol
Parameter
Conditions
Typ
(Note 5)
LM7171AI
Limit
LM7171BI
Limit
Units
(Note 6)
(Note 6)
=
Output Current
Sourcing, RL 100Ω
100
100
140
135
6.5
mA
mA
=
(in Linear Region)
Output Short Circuit
Current
Sinking, RL 100Ω
ISC
Sourcing
Sinking
IS
Supply Current
8.5
8.5
mA
9.5
9.5
max
±
15V AC Electrical Characteristics
+
−
=
=
= = =
−15V, VCM 0V, and RL 1 kΩ.
Unless otherwise specified, TJ 25˚C, V
+15V, V
Typ
LM7171AI
LM7171BI
Limit
Symbol
Parameter
Conditions
(Note 5)
Limit
Units
(Note 6)
(Note 6)
=
=
SR
Slew Rate (Note 9)
AV +2, VIN 13 VPP
4100
3100
200
220
50
V/µs
=
=
AV +2, VIN 10 VPP
Unity-Gain Bandwidth
−3 dB Frequency
Phase Margin
MHz
MHz
Deg
ns
=
AV +2
φm
=
=
±
ts
Settling Time (0.1%)
AV −1, VO
5V
42
=
RL 500Ω
=
=
±
tp
Propagation Delay
AV −2, VIN
5V,
5
ns
=
RL 500Ω
AD
Differential Gain (Note 10)
Differential Phase (Note 10)
Second Harmonic (Note 12)
0.01
0.02
−110
−75
−115
−55
14
%
φD
Deg
dBc
dBc
dBc
dBc
=
fIN 10 kHz
=
fIN 5 MHz
=
fIN 10 kHz
Third Harmonic (Note 12)
=
fIN 5 MHz
=
en
Input-Referred
Voltage Noise
Input-Referred
Current Noise
f
f
10 kHz
=
in
10 kHz
1.5
±
5V DC Electrical Characteristics
+
−
=
=
= = =
−5V, VCM 0V, and RL 1 kΩ. Boldface lim-
Unless otherwise specified, all limits guaranteed for TJ 25˚C, V
its apply at the temperature extremes
+5V, V
Typ
LM7171AI
Limit
(Note 6)
1.5
LM7171BI
Limit
(Note 6)
3.5
Symbol
VOS
Parameter
Conditions
(Note 5)
0.3
Units
Input Offset Voltage
mV
max
4
7
TC VOS
Input Offset Voltage
Average Drift
35
µV/˚C
IB
Input Bias Current
3.3
10
12
4
10
12
4
µA
max
µA
IOS
Input Offset Current
0.1
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4
±
5V DC Electrical Characteristics (Continued)
+
−
=
=
= = =
−5V, VCM 0V, and RL 1 kΩ. Boldface lim-
Unless otherwise specified, all limits guaranteed for TJ 25˚C, V
its apply at the temperature extremes
+5V, V
Typ
LM7171AI
Limit
LM7171BI
Limit
Symbol
Parameter
Conditions
(Note 5)
Units
(Note 6)
6
(Note 6)
6
max
RIN
Input Resistance
Common Mode
40
3.3
15
MΩ
Differential Mode
RO
Output Resistance
Common Mode
Rejection Ratio
Power Supply
Ω
dB
min
dB
min
V
=
±
CMRR
VCM
2.5V
104
80
75
85
80
70
65
75
70
=
±
±
PSRR
VCM
AV
VS
15V to 5V
90
Rejection Ratio
Input Common-Mode
Voltage Range
>
±
3.2
CMRR 60 dB
=
Large Signal Voltage
Gain (Note 7)
RL 1 kΩ
78
76
75
70
70
65
dB
min
dB
=
RL 100Ω
72
68
67
63
min
V
=
VO
Output Swing
RL 1 kΩ
3.4
−3.4
3.1
−3.0
31
3.2
3
3.2
3
min
V
−3.2
−3
−3.2
−3
max
V
=
RL 100Ω
2.9
2.8
−2.9
−2.8
29
2.9
2.8
−2.9
−2.8
29
min
V
max
mA
min
mA
max
mA
=
Sourcing, RL 100Ω
Output Current
(Open Loop) (Note 8)
28
28
=
Sinking, RL 100Ω
30
29
29
28
28
ISC
Output Short Circuit
Current
Sourcing
Sinking
135
100
6.2
IS
Supply Current
8
8
mA
9
9
max
±
5V AC Electrical Characteristics
+
−
=
=
=
=
=
Unless otherwise specified, TJ 25˚C, V
+5V, V
−5V, VCM 0V, and RL 1 kΩ.
Typ
LM7171AI LM7171BI
Symbol
Parameter
Conditions
(Note 5)
Limit
Limit
Units
(Note 6)
(Note 6)
=
=
SR
Slew Rate (Note 9)
Unity-Gain Bandwidth
−3 dB Frequency
Phase Margin
AV +2, VIN 3.5 VPP
950
125
140
57
V/µs
MHz
MHz
Deg
ns
=
AV +2
φm
=
=
±
ts
Settling Time (0.1%)
AV −1, VO
1V,
56
=
RL 500Ω
=
=
±
tp
Propagation Delay
AV −2, VIN
1V,
6
ns
%
=
RL 500Ω
AD
Differential Gain (Note 1)
0.02
5
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±
5V AC Electrical Characteristics (Continued)
+
−
=
=
=
=
=
Unless otherwise specified, TJ 25˚C, V
+5V, V
−5V, VCM 0V, and RL 1 kΩ.
Typ
LM7171AI LM7171BI
Symbol
Parameter
Conditions
(Note 5)
Limit
Limit
Units
(Note 6)
(Note 6)
φD
Differential Phase (Note 10)
Second Harmonic (Note 12)
0.03
−102
−70
−110
−51
14
Deg
dBc
dBc
dBc
dBc
=
fIN 10 kHz
=
fIN 5 MHz
=
fIN 10 kHz
Third Harmonic (Note 12)
=
fIN 5 MHz
=
en
Input-Referred
Voltage Noise
Input-Referred
Current Noise
f
f
10 kHz
=
in
10 kHz
1.8
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in-
tended to be functional, but specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5 kΩ in series with 100 pF.
Note 3: 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.
=
Note 4: The maximum power dissipation is a function of T
, θ , and T . The maximum allowable power dissipation at any ambient temperature is P
A D
J(max) JA
(T
–T )/θ . All numbers apply for packages soldered directly into a PC board.
JA
J(max)
A
Note 5: Typifcal values represent the most likely parametric norm.
Note 6: All limits are guaranteed by testing or statistical analysis.
=
=
=
±
5V. For V
S
±
±
Note 7: Large signal voltage gain is the total output swing divided by the input signal required to produce that swing. For V
15V, V
OUT
5V,
S
=
±
V
1V.
OUT
Note 8: The open loop output current is guaranteed, by the measurement of the open loop output voltage swing, using 100Ω output load.
Note 9: Slew Rate is the average of the raising and falling slew rates.
=
=
1 V at 3.58 MHz and both input and output 75Ω terminated.
Note 10: Differential gain and phase are measured with A
+2, V
IN
V
PP
=
±
Note 11: Input differential voltage is applied at V
15V.
S
=
=
=
+2 and R 100Ω.
L
Note 12: Harmonics are measured with V
IN
1 V , A
PP
V
Typical Performance Characteristics unless otherwise noted, TA= 25˚C
Supply Current
vs Supply Voltage
Supply Current
vs Temperature
Input Offset Voltage
vs Temperature
DS012385-63
DS012385-64
DS012385-65
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6
Typical Performance Characteristics unless otherwise noted, TA= 25˚C (Continued)
Input Bias Current
vs Temperature
Short Circuit Current
vs Temperature (Sourcing)
Short Circuit Current
vs Temperature (Sinking)
DS012385-66
DS012385-67
DS012385-68
Output Voltage
Output Voltage
CMRR vs Frequency
vs Output Current
vs Output Current
DS012385-71
DS012385-69
DS012385-70
PSRR vs Frequency
PSRR vs Frequency
DS012385-72
DS012385-73
Open Loop Frequency
Response
Open Loop Frequency
Response
Gain-Bandwidth Product
vs Supply Voltage
DS012385-51
DS012385-52
DS012385-53
7
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Typical Performance Characteristics unless otherwise noted, TA= 25˚C (Continued)
Gain-Bandwidth Product
vs Load Capacitance
Large Signal Voltage Gain
vs Load
Large Signal Voltage Gain
vs Load
DS012385-55
DS012385-56
DS012385-54
DS012385-57
DS012385-60
Input Voltage Noise
vs Frequency
Input Voltage Noise
vs Frequency
Input Current Noise
vs Frequency
DS012385-58
DS012385-59
Input Current Noise
vs Frequency
Slew Rate
vs Supply Voltage
Slew Rate
vs Input Voltage
DS012385-61
DS012385-62
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Typical Performance Characteristics unless otherwise noted, TA= 25˚C (Continued)
Slew Rate
Open Loop Output
Open Loop Output
vs Load Capacitance
Impedance vs Frequency
Impedance vs Frequency
DS012385-23
DS012385-25
DS012385-26
Large Signal Pulse
Large Signal Pulse
Large Signal Pulse
=
Response AV −1,
=
Response AV −1,
=
Response AV +2,
=
±
VS
15V
=
±
VS
5V
=
±
VS
15V
DS012385-27
DS012385-28
DS012385-29
Large Signal Pulse
Small Signal Pulse
Small Signal Pulse
=
Response AV +2,
=
Response AV −1,
=
Response AV −1,
=
±
VS
5V
=
±
VS
15V
=
±
VS
5V
DS012385-30
DS012385-31
DS012385-32
9
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Typical Performance Characteristics unless otherwise noted, TA= 25˚C (Continued)
Small Signal Pulse
Small Signal Pulse
Closed Loop Frequency
Response vs Supply
=
Response AV +2,
=
Response AV +2,
=
±
VS
15V
=
±
VS
5V
=
Voltage (AV +2)
DS012385-33
DS012385-34
DS012385-35
DS012385-38
DS012385-40
Closed Loop Frequency
Response vs Capacitive
Closed Loop Frequency
Response vs Capacitive
Closed Loop Frequency
Response vs Input Signal
=
Load (AV +2)
=
Load (AV +2)
=
Level (AV +2)
DS012385-36
DS012385-37
Closed Loop Frequency
Response vs Input Signal
Closed Loop Frequency
Response vs Input Signal
Closed Loop Frequency
Response vs Input Signal
=
Level (AV +2)
=
Level (AV +2)
=
Level (AV +2)
DS012385-43
DS012385-39
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10
Typical Performance Characteristics unless otherwise noted, TA= 25˚C (Continued)
Closed Loop Frequency
Response vs Input Signal
Closed Loop Frequency
Response vs Input Signal
Closed Loop Frequency
Response vs Input Signal
=
Level (AV +4)
=
Level (AV +4)
=
Level (AV +4)
DS012385-44
DS012385-45
DS012385-41
Closed Loop Frequency
Response vs Input Signal
Total Harmonic Distortion
vs Frequency (Note 13)
Total Harmonic Distortion
vs Frequency (Note 13)
=
Level (AV +4)
DS012385-46
DS012385-47
DS012385-42
Undistorted Output Swing
vs Frequency
Undistorted Output Swing
vs Frequency
Undistorted Output Swing
vs Frequency
DS012385-48
DS012385-49
DS012385-50
11
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Typical Performance Characteristics unless otherwise noted, TA= 25˚C (Continued)
Harmonic Distortion
vs Frequency
Harmonic Distortion
vs Frequency
Maximum Power Dissipation
vs Ambient Temperature
DS012385-74
DS012385-75
DS012385-20
Note 13: The THD measurement at low frequency is limited by the test instrument.
Simplified Schematic Diagram
DS012385-9
Note: M1 and M2 are current mirrors.
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.
Application Notes
LM7171 Performance Discussion
The LM7171 is a very high speed, voltage feedback ampli-
fier. 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.
LM7171 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,
The LM7171 is a true voltage feedback amplifier. Unlike cur-
rent feedback amplifiers (CFAs) with a low inverting input im-
pedance and a high non-inverting input impedance, both in-
puts of voltage feedback amplifiers (VFAs) have high
impedance nodes. The low impedance inverting input in
RE the equivalent of the feedback resistor, and stage A buff-
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12
COMPONENT SELECTION AND FEEDBACK RESISTOR
LM7171 Circuit Operation (Continued)
It is important in high speed applications to keep all compo-
nent leads short. For discrete components, choose carbon
composition-type resistors and mica-type capacitors. Sur-
face mount components are preferred over discrete compo-
nents for minimum inductive effect.
ers the inverting input. The triple-buffered output stage iso-
lates the gain stage from the load to provide low output im-
pedance.
LM7171 Slew Rate Characteristic
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 feed-
back resistor of 510Ω gives optimal performance.
The slew rate of LM7171 is determined by the current avail-
able 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 configura-
tions. A curve of slew rate versus input voltage level is pro-
vided in the “Typical Performance Characteristics”.
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
When a very fast large signal pulse is applied to the input of
an amplifier, some overshoot or undershoot occurs. By plac-
ing an external resistor such as 1 kΩ in series with the input
of LM7171, the bandwidth is reduced to help lower the over-
shoot.
>
CF (RG x CIN)/RF
can be used to cancel that pole. For LM7171, a feedback ca-
pacitor of 2 pF is recommended. Figure 1 illustrates the com-
pensation circuit.
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 the “Typical Performance Characteristics” section, there
=
=
are several curves of AV +2 and AV +4 versus input sig-
=
nal 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.
DS012385-10
=
For the AV
+2 curves, with slight peaking occurs. This
FIGURE 1. Compensating for Input Capacitance
>
peaking at high frequency ( 100 MHz) is caused by a large
input signal at high enough frequency that exceeds the am-
plifier’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.
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 individu-
ally by placing 0.01 µF ceramic capacitors directly to power
supply pins and 2.2 µF tantalum capacitors close to the
power supply pins.
Layout Consideration
PRINTED CIRCUIT BOARDS 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 de-
graded AC performance in high speed circuits. As a rule, the
signal traces should be short and wide to provide low induc-
tance 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 us-
ing any socket.
USING PROBES
DS012385-11
Active (FET) probes are ideal for taking high frequency mea-
surements 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 er-
rors in measurement. Instead, the probes can be grounded
directly by removing the ground leads and probe jackets and
using scope probe jacks.
FIGURE 2. Power Supply Bypassing
Termination
In high frequency applications, reflections occur if signals
are not properly terminated. Figure 3 shows a properly termi-
nated signal while Figure 4 shows an improperly terminated
signal.
13
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Termination (Continued)
DS012385-12
FIGURE 5. Isolation Resistor Used
to Drive Capacitive Load
DS012385-17
FIGURE 3. Properly Terminated Signal
DS012385-13
FIGURE 6. The LM7171 Driving a 150 pF Load
with a 50Ω Isolation Resistor
Power Dissipation
The maximum power allowed to dissipate in a device is de-
fined as:
DS012385-18
FIGURE 4. Improperly Terminated Signal
=
PD (TJ(max) − TA)/θJA
To minimize reflection, coaxial cable with matching charac-
teristic 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.
Where
PD
is the power dissipation in a device
is the maximum junction temperature
is the ambient temperature
TJ(max)
TA
θJA
is the thermal resistance of a particular package
For example, for the LM7171 in a SO-8 package, the maxi-
mum power dissipation at 25˚C ambient temperature is
730 mW.
Driving Capacitive Loads
Amplifiers driving capacitive loads can oscillate or have ring-
ing at the output. To eliminate oscillation or reduce ringing,
an isolation resistor can be placed as shown below in Figure
5 The combination of the isolation resistor and the load ca-
pacitor forms a pole to increase stability by adding more
phase margin to the overall system. The desired perfor-
mance depends on the value of the isolation resistor; the big-
ger the isolation resistor, the more damped the pulse re-
sponse becomes. For LM7171, a 50Ω isolation resistor is
Thermal resistance, θJA, depends on parameters such as
die size, package size and package material. The smaller
the die size and package, the higher θJA becomes. The 8-pin
DIP package has a lower thermal resistance (108˚C/W) than
that of 8-pin SO (172˚C/W). Therefore, for higher dissipation
capability, use an 8-pin DIP package.
The total power dissipated in a device can be calculated as:
=
PD PQ + PL
recommended for initial evaluation. Figure
6 shows the
PQ is the quiescent power dissipated in a device with no load
connected at the output. PL is the power dissipated in the de-
vice with a load connected at the output; it is not the power
dissipated by the load.
LM7171 driving a 150 pF load with the 50Ω isolation resistor.
Furthermore,
=
PQ
:
supply current x total supply voltage with no load
output current (voltage difference between
=
PL:
x
supply voltage and output voltage of the same
side of supply voltage)
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14
Power Dissipation (Continued)
Application Circuit
For example, the total power dissipated by the LM7171 with
Fast Instrumentation Amplifier
=
±
VS
15V and output voltage of 10V into 1 kΩ is
=
=
=
=
PD
PQ + PL
(6.5 mA) x (30V) + (10 mA) x (15V − 10V)
195 mW + 50 mW
245 mW
DS012385-14
DS012385-80
Multivibrator
DS012385-81
DS012385-15
Pulse Width Modulator
DS012385-16
15
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Application Circuit (Continued)
Video Line Driver
DS012385-21
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16
Design Kit
A design kit is available for the LM7171. The design kit con-
tains:
Pitch Pack
A pitch pack is available for the LM7171. The pitch pack con-
tains:
•
•
•
•
High Speed Evaluation Board
LM7171 in 8-pin DIP Package
LM7171 Datasheet
•
•
•
LM7171 in 8-pin DIP Package
LM7171 Datasheet
Pspice Macromodel DIskette With The LM7171 Macro-
model
Pspice Macromodel DIskette With The LM7171 Macro-
model
•
Amplifier Selection Guide
•
Amplifier Selection Guide
Contact your local National Semiconductor sales office to
obtain a pitch pack and design kit.
17
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LM7171AIM, LM7171BIM,
LM7171AIMX or LM7171BIMX
8-Lead (0.150" Wide) Molded Small Outline Package, JEDEC
NS Package Number M08A
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18
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM7171AIWM, LM7171BIWM,
LM7171AIWMX or LM7171BIWMX
16-Lead (0.300" Wide) Molded Small Outline Package, JEDEC
NS Package Number M16B
Order Number LM7171AIN or LM7171BIN
8-Lead (0.300" Wide) Molded Dual-In-Line Package, JEDEC
NS Package Number N08E
19
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number 5962-9553601QPA
8-Lead Dual-In-Line Package
NS Package Number J08A
NSID is LM7171AMJ/883
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