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LM6182IN
Datasheet (NSC)
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Datasheet LM6182IN, LM6182IMX, LM6182IM, LM6182AIN Datasheet (NSC)

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Page 1
LM6182 Dual 100 mA Output, 100 MHz Current Feedback Amplifier
General Description
The LM6182 dual current feedback amplifier offers an unpar­alleled combination of bandwidth, slew-rate, and output cur­rent. Each amplifier can directly drive a 2V signal into a 50Ω or 75Ω back-terminated coax cable system over the full in­dustrial temperature range. This represents a radical en­hancement in output drive capability for a dual 8-pin high-speed amplifier making it ideal for video applications.
Built on National’s advanced high-speed VIP II
™
(Vertically Integrated PNP) process, the LM6182 employs current-feedback providing bandwidth that does not vary dramatically with gain; 100 MHz at Av=−1, 60 MHz at Av
=
−10. With a slew rate of 2000 V/µsec, 2nd harmonic distor­tion of −50 dBc at 10 MHz and settling time of 50 ns (0.1%), the two independent amplifiers of the LM6182 offer perfor­mance that is ideal for data acquisition, high-speed ATE,and precision pulse amplifier applications.
See the LM6181 data sheet for a single amplifier with these same features.
Features
(Typical unless otherwise noted)
n Slew Rate: 2000 V/µs n Closed Loop Bandwidth: 100 MHz n Settling Time (0.1%): 50 ns n Low Differential Gain and Phase Error: 0.05%, 0.04˚
R
L
=
150Ω
n Low Offset Voltage: 2 mV n High Output Drive:
±
10V into 150Ω
n Characterized for Supply Ranges:
±
5V and±15V
n Improved Performance over OP260 and LT1229
Applications
n Coax Cable Driver n Professional Studio Video Equipment n Flash ADC Buffer n PC and Workstation Video Boards n Facsimile and Imaging Systems
Typical Application
VIP II™is a trademark ofNational Semiconductor Corporation.
DS011926-1
DS011926-2
April 1994
LM6182 Dual 100 mA Output, 100 MHz Current Feedback Amplifier
© 1999 National Semiconductor Corporation DS011926 www.national.com
Page 2
Connection Diagrams
Dual-In-Line Package (J)
DS011926-51
Order Number LM6182AMJ/883 See NS Package Number J14A
Small Outline Package (M)
DS011926-4
*
Heat Sinking Pins (Note 3)
Order Number LM6182IM or LM6182AIM
See NS Package Number M16A
Dual-In-Line Package (N)
DS011926-3
Order Number LM6182IN, LM6182AIN or LM6182AMN
See NS Package Number N08E
www.national.com 2
Page 3
Absolute Maximum Ratings (Note 1)
Supply Voltage
±
18V
Differential Input Voltage
±
6V
Input Voltage
±
Supply Voltage Inverting Input Current 15 mA Output Short Circuit (Note 4)
Soldering Information
Dual-In-Line Package (N)
Soldering (10s) 260˚C
Small Outline Package (M)
Vapor Phase (60s) 215˚C Infrared (15s) 220˚C
Storage Temperature Range −65˚C ≤ T
J
≤ +150˚C Junction Temperature 150˚C ESD Rating (Note 2)
±
2000V
Operating Ratings
Supply Voltage Range 7V to 32V
Junction Temperature Range (Note 3)
LM6182AM −55˚C ≤ T
J
≤ +125˚C
LM6182AI, LM6182I −40˚C ≤ T
J
≤ +85˚C
±
15V DC Electrical Characteristics
The following specifications apply for supply voltage
=
±
15V, Vcm=V
O
=
0V, R
f
=
820Ω, and R
L
=
1kΩunless otherwise
noted. Boldface limits apply at the temperature extremes; all other limits T
J
=
25˚C.
Symbol Parameter Conditions Typical
(Note 5)
LM6182AM LM6182AI LM6182I Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
V
OS
Input Offset Voltage 2.0 3.0 3.0 5.0 mV
4.0 3.5 5.5 max
TCV
OS
Input Offset Voltage Drift 5.0 µV/˚C
I
B
Inverting Input Bias Current 2.0 5.0 5.0 10.0 µA
max
12.0 12.0 17.0
Non-Inverting Input Bias Current 0.75 2.0 2.0 3.0
4.0 4.0 5.0
TCI
B
Inverting Input Bias Current Drift 30 nA/˚C Non-Inverting Input Bias Current Drift 10
I
B
Inverting Input Bias Current
±
4.5V ≤ VS≤±16V 0.1 0.5 0.5 0.75 µA/V max
PSR Power Supply Rejection 3.0 3.0 4.5
Non-Inverting Input Bias Current
±
4.5V ≤ VS≤±16V 0.05 0.5 0.5 0.5
Power Supply Rejection 1.5 1.5 3.0
I
B
Inverting Input Bias Current −10V ≤ VCM≤ +10V 0.15 0.5 0.5 0.75
CMR Common Mode Rejection 1.0 1.0 1.5
Non-Inverting Input Bias Current −10V ≤ V
CM
≤ +10V 0.1 0.5 0.5 0.5
Common Mode Rejection 1.0 1.0 1.5
CMRR Common Mode Rejection Ratio −10V ≤ V
CM
≤ +10V 60 50 50 50 dB
47 47 47 min
PSRR Power Supply Rejection Ratio
±
4.5V ≤ VS≤±16V 80 70 70 70 dB
67 67 65 min
R
O
Output Resistance A
V
=
−1 0.2 Ω
f=300 kHz
R
IN
Non-Inverting Input Resistance 10 MΩ
V
O
Output Voltage Swing R
L
=
1kΩ 12 11 11 11 V
min
10 10 10
R
L
=
150Ω 11 9.5 9.5 9.5
5.6 6.0 6.0
I
SC
Output Short Circuit Current 100 70 70 70 mA
37.5 40 40 min
www.national.com3
Page 4
±
15V DC Electrical Characteristics (Continued)
The following specifications apply for supply voltage
=
±
15V, Vcm=V
O
=
0V, R
f
=
820Ω, and R
L
=
1kΩunless otherwise
noted. Boldface limits apply at the temperature extremes; all other limits T
J
=
25˚C.
Symbol Parameter Conditions Typical
(Note 5)
LM6182AM LM6182AI LM6182I Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
Z
T
Transimpedance R
L
=
1kΩ 1.8 1.0 1.0 0.8 MΩ
min
0.4 0.5 0.4
R
L
=
150Ω 1.4 0.8 0.8 0.7
0.3 0.35 0.3
I
S
Supply Current No Load, V
IN
=
0V 15 20 20 20 mA
Both Amplifiers 22 22 22 max
V
CM
Input Common Mode Voltage Range V+−1.7V V
V
−
+1.7V
±
15V AC Electrical Characteristics
The following specifications apply for supply voltage
=
±
15V, Vcm=V
O
=
0V, R
f
=
820Ω, and R
L
=
1kΩunless otherwise
noted. Boldface limits apply at the temperature extremes; all other limits T
J
=
25˚C.
Symbol Parameter Conditions Typical
(Note 5)
LM6182AM LM6182AI LM6182I Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6) Xt Crosstalk Rejection (Note 7) 93 dB BW Closed Loop Bandwidth −3 dB A
V
=
+2 100 MHz
A
V
=
+10 75
A
V
=
−1 100
A
V
=
−10 60
Closed Loop Bandwidth A
V
=
+2, R
L
=
150Ω 35
0.1 dB Flat, R
SOURCE
=
200Ω
PBW Power Bandwidth A
V
=
−1, V
O
=
5V
PP
60
SR Slew Rate Overdriven 2000 V/µs
min
A
V
=
−1, V
O
=
±
10V 1400 1000 1000 1000
R
L
=
150Ω, (Note 8)
t
s
Settling Time (0.1%)A
V
=
−1, V
O
=
±
5V 50 ns
R
L
=
150Ω
t
r,tf
Rise and Fall Time V
O
=
1V
PP
5
t
p
Propagation Delay Time V
O
=
1V
PP
6
in(+) Non-Inverting Input Noise
Current Density
f=1 kHz 3 pA/
√
Hz
in(−) Inverting Input Noise
Current Density
f=1 kHz 16 pA/
√
Hz
e
n
Input Noise Voltage Density f=1 kHz 4 nV/√Hz Second Harmonic Distortion V
O
=
2V
PP
,f=10 MHz -50 dBc
A
V
=
+2
Third Harmonic Distortion V
O
=
2V
PP
,f=10 MHz -55
A
V
=
+2
Differential Gain R
L
=
150Ω 0.05
%
A
V
=
+2, NTSC
Differential Phase R
L
=
150Ω 0.04 Deg
A
V
=
+2, NTSC
THD Total Harmonic Distortion V
O
=
2V
PP,AV
=
+2, 0.58
%
f=10 MHz, R
L
=
150Ω
www.national.com 4
Page 5
±
5V DC Electrical Characteristics
The following specifications apply for supply voltage
=
±
5V, Vcm=V
O
=
0V, R
f
=
820Ω, and R
L
=
1kΩunless otherwise
noted. Boldface limits apply at the temperature extremes; all other limits T
J
=
25˚C.
Symbol Parameter Conditions Typical
(Note 5)
LM6182AM LM6182AI LM6182I Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
V
OS
Input Offset Voltage 1.0 2.0 2.0 3.0 mV
3.0 2.5 3.5 max
TCV
OS
Input Offset Voltage Drift 2.5 µV/˚C
I
B
Inverting Input Bias Current 5.0 10 10 17.5 µA
max
22 22 27.0
Non-Inverting Input Bias Current 0.25 1.5 1.5 3.0
3.0 3.0 5.0
TCI
B
Inverting Input Bias Current Drift 50 nA/˚C Non-Inverting Input Bias Current Drift 3.0
I
B
Inverting Input Bias Current
±
4V ≤ VS≤±6V 0.3 0.5 0.5 0.75 µA/V
max
PSR Power Supply Rejection 1.0 1.0 1.5
Non-Inverting Input Bias Current
±
4V ≤ VS≤±6V 0.05 0.5 0.5 0.5
Power Supply Rejection 1.0 1.0 1.5
I
B
Inverting Input Bias Current −2.5V ≤ VCM≤ +2.5V 0.3 0.5 0.5 1.0
CMR Common Mode Rejection 1.0 1.0 1.5
Non-Inverting Input Bias Current −2.5V ≤ V
CM
≤ +2.5V 0.12 0.5 0.5 0.5
Common Mode Rejection 1.0 1.0 1.5
CMRR Common Mode Rejection Ratio −2.5V ≤ V
CM
≤ +2.5V 57 50 50 50 dB
min
47 47 47
PSRR Power Supply Rejection Ratio
±
4V ≤ VS≤±6V 80 70 70 64
67 67 60
R
O
Output Resistance A
V
=
−1 0.25 Ω
f=300 kHz
R
IN
Non-Inverting Input Resistance 8 MΩ
V
O
Output Voltage Swing R
L
=
1kΩ 2.6 2.25 2.25 2.25 V
min
2.0 2.0 2.0
R
L
=
150Ω 2.2 2.0 2.0 2.0
1.8 1.8 1.8
I
SC
Output Short Circuit Current 100 65 65 65 mA
35 40 40 min
Z
T
Transimpedance R
L
=
1kΩ 1.4 0.75 0.75 0.6 MΩ
min
0.3 0.35 0.3
R
L
=
150Ω 1.0 0.5 0.5 0.4
0.2 0.25 0.2
I
S
Supply Current No Load, V
IN
=
0V 13 17 17 17 mA
Both Amplifiers 18.5 18.5 18.5 max
V
CM
Input Common Mode Voltage Range V+−1.7V V
V
−
+1.7V
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Page 6
±
5V AC Electrical Characteristics
The following specifications apply for supply voltage
=
±
5V, Vcm=V
O
=
0V, R
f
=
820Ω, and R
L
=
1kΩunless otherwise
noted. Boldface limits apply at the temperature extremes; all other limits T
J
=
25˚C.
Symbol Parameter Conditions Typical
(Note 5)
LM6182AM LM6182AI LM6182I Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6) Xt Crosstalk Rejection (Note 7) 92 dB BW Closed Loop Bandwidth −3 dB A
V
=
+2 50 MHz
A
V
=
+10 40
A
V
=
−1 55
A
V
=
−10 35
Closed Loop Bandwidth A
V
=
+2, R
L
=
150Ω 15
0.1 dB Flat, R
SOURCE
=
200Ω
PBW Power Bandwidth A
V
=
−1, V
O
=
4V
PP
40
SR Slew Rate A
V
=
−1, V
O
=
±
2V 500 375 375 375 V/µs
R
L
=
150Ω, (Note 8) min
t
s
Settling Time (0.1%)A
V
=
−1, V
O
=
±
2V 50 ns
R
L
=
150Ω
t
r,tf
Rise and Fall Time V
O
=
1V
PP
8.5
t
p
Propagation Delay Time V
O
=
1V
PP
8
in(+) Non-Inverting Input Noise
Current Density
f=1 kHz 3 pA/
√
Hz
in(−) Inverting Input Noise
Current Density
f=1 kHz 16 pA/
√
Hz
e
n
Input Noise Voltage Density f=1 kHz 4 nV/√Hz Second Harmonic Distortion V
O
=
2V
PP
,f=10 MHz -45 dBc
A
V
=
+2
Third Harmonic Distortion V
O
=
2V
PP
,f=10 MHz -55
A
V
=
+2
Differential Gain R
L
=
150Ω 0.06
%
A
V
=
+2, NTSC
Differential Phase R
L
=
150Ω 0.16 Deg
A
V
=
+2, NTSC
THD Total Harmonic Distortion V
O
=
2V
PP,AV
=
+2, 0.36
%
f=5 MHz, R
L
=
150Ω
Note 1: 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 device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Human body model 100 pF and 1.5 kΩ. Note 3: The typical junction-to-ambient thermal resistance of the molded plastic DIP(N) soldered directly into a PC board is 95˚C/W. The junction-to-ambient thermal
resistance of the S.O. surface mount (M) package mounted flush to the PC board is 70˚C/W when pins 1,4,8,9 and 16 are soldered to a total of 2 in
2
1 oz copper
trace. The S.O. (M) package must have pin 4 and at least one of pins 1,8,9, or 16 connected to V− for proper operation. Note 4: Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowable junction temperature of 150˚C. Each am-
plifier of the LM6182 is short circuit current limited to 100 mA typical.
Note 5: Typical values represent the most likely parametric norm. Note 6: All limits are guaranteed at room temperature (standard type face) or at operating temperature extremes (boldface type). Note 7: Each amp excited in turn with 100 kHz to produce Vo=2 Vpp. Results are input referred. Note 8: Measured from +25%to +75%of output waveform. Note 9: Also available per the Standard Military Drawing, 5962-9460301MCA. Note 10: For guaranteed military specifications see military datasheet MNLM6182AM-X.
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Page 7
±
5V AC Electrical Characteristics (Continued)
Simplified Schematic 1/2 LM6182
DS011926-6
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Page 8
Typical Performance Characteristics MAXIMUM POWER DERATING CURVES
TYPICAL PERFORMANCE TEST CIRCUITS
N-Package
DS011926-7
M-Package
DS011926-8
*
θ
ja
=
Thermal Resistance with 2 square inches of 1 ounce copper tied to
pins 1, 8, 9 and 16
Non-Inverting: Small Signal Pulse Response, Slew Rate, −3 dB Bandwidth
DS011926-9
Inverting: Small Signal Pulse Response, Slew Rate, −3 dB Bandwidth
DS011926-10
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Page 9
TYPICAL PERFORMANCE TEST CIRCUITS (Continued)
Amplifier-to-Amplifier Isolation
DS011926-11
Input Voltage Noise
DS011926-12
CMRR
DS011926-13
PSRR (VS+)
DS011926-14
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Page 10
Typical Performance Characteristics V
S
=
±
15V and T
A
=
25˚C unless otherwise noted.
Inverting Gain Frequency Response V
S
=
±
15V, A
V
=
−1, R
f
=
820Ω
DS011926-52
Inverting Gain Frequency Response V
S
=
±
5V, A
V
=
−1, R
f
=
820Ω
DS011926-53
Non-Inverting Gain Frequency Response V
S
=
±
15V, A
V
=
+2, R
f
=
820Ω
DS011926-54
Non-Inverting Gain Frequency Response V
S
=
±
5V, A
V
=
+2, R
f
=
820Ω
DS011926-55
−3 dB Bandwidth vs R
f
and Rs,A
V
=
+2
DS011926-56
Inverting Gain vs
−3 dB Bandwidth R
f
=
820Ω
DS011926-57
Non-Inverting Gain vs
−3 dB Bandwidth R
f
=
820Ω
DS011926-58
−3 dB Bandwidth vs Supply Voltage A
V
=
−1
DS011926-59
Transimpedance vs Frequency R
L
=
1kΩ
DS011926-60
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Page 11
Typical Performance Characteristics V
S
=
±
15V and T
A
=
25˚C unless otherwise
noted. (Continued)
Transimpedance vs Frequency R
L
=
150Ω
DS011926-61
Settling Response V
S
=
±
15V, R
L
=
150Ω
A
V
=
−1, V
O
=
±
5V
DS011926-62
Settling Response V
S
=
±
5V, R
L
=
150Ω
A
V
=
−1, V
O
=
±
2V
DS011926-63
Long Term Settling Time Response V
S
=
±
15V,
R
L
=
150Ω,A
V
=
−1, V
O
=
±
5V
DS011926-64
Suggested Rfand R
s
for CL,A
V
=
−1
DS011926-65
Suggested Rfand R
s
for CL,A
V
=
+2
DS011926-66
Output Impedance vs Frequency A
V
=
−1, R
L
=
820Ω
DS011926-67
PSRR (VS+)vs Frequency, A
V
=
2,
R
f
=
R
s
=
820Ω
DS011926-68
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Page 12
Typical Performance Characteristics V
S
=
±
15V and T
A
=
25˚C unless otherwise
noted. (Continued)
PSRR (V
S−
)vs
Frequency, A
V
=
2,
R
f
=
R
s
=
820Ω
DS011926-69
CMRR vs Frequency R
f
=
R
s
=
820Ω
DS011926-70
Input Voltage Noise vs Frequency
DS011926-71
Input Current Noise vs Frequency
DS011926-72
Slew Rate vs Temperature A
V
=
−1, R
L
=
150Ω
DS011926-73
Slew Rate vs Supply Voltage A
V
=
−1, R
L
=
150Ω
DS011926-74
Distortion vs Frequency V
S
=
±
15V, A
V
=
+2,
R
L
=
150Ω,V
O
=
2Vp-p
DS011926-75
Distortion vs Frequency V
S
=
±
15V, A
V
=
−1,
R
L
=
150Ω,V
O
=
2Vp-p
DS011926-76
Distortion vs Frequency V
S
=
±
5V, A
V
=
+2,
R
L
=
150Ω,V
O
=
2Vp-p
DS011926-77
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Page 13
Typical Performance Characteristics V
S
=
±
15V and T
A
=
25˚C unless otherwise
noted. (Continued)
Distortion vs Frequency V
S
=
±
5V, A
V
=
−1,
R
L
=
150Ω,V
O
=
2Vp-p
DS011926-78
Crosstalk Rejection vs Frequency
DS011926-79
Maximum Output Voltage Swing vs Frequency (THD ≤ 1%)
DS011926-80
−3 dB Bandwidth vs Temperature, A
V
=
−1
DS011926-81
−3 dB Bandwidth vs Temperature, A
V
=
+2
DS011926-82
Small Signal Pulse Response vs Temperature, A
V
=
−1,
V
S
=
±
15V, R
L
=
1kΩ
DS011926-83
Small Signal Pulse Response vs Temperature, A
V
=
−1,
V
S
=
±
15V, R
L
=
150Ω
DS011926-84
Small Signal Pulse Response vs Temperature, A
V
=
+2,
V
S
=
±
15V, R
L
=
1kΩ
DS011926-85
Small Signal Pulse Response vs Temperature, A
V
=
+2,
V
S
=
±
15V, R
L
=
150Ω
DS011926-86
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Page 14
Typical Performance Characteristics V
S
=
±
15V and T
A
=
25˚C unless otherwise
noted. (Continued)
Settling Time vs Output Step, R
F
=
820Ω
R
L
=
150Ω,A
V
=
−1
DS011926-87
Settling Time vs Output Step, R
F
=
820Ω
R
L
=
150Ω,A
V
=
−1
DS011926-88
Small Signal Pulse Response vs Closed-Loop Gain R
L
=
1k
DS011926-89
Small Signal Pulse Response vs Closed-Loop Gain R
L
=
150Ω
DS011926-90
Small Signal Pulse Response vs Supply Voltage A
V
=
+2, R
L
=
1k
DS011926-91
VOSvs Temperature
DS011926-92
Ztvs Temperature
DS011926-93
Ztvs Temperature
DS011926-94
Isvs Temperature
DS011926-95
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Page 15
Typical Performance Characteristics V
S
=
±
15V and T
A
=
25˚C unless otherwise
noted. (Continued)
PSRR vs Temperature
DS011926-96
CMRR vs Temperature
DS011926-97
Ib(+) vs Temperature
DS011926-98
Ib(−) vs Temperature
DS011926-99
Ib(+) PSR vs Temperature
DS011926-A0
Ib(−) PSR vs Temperature
DS011926-A1
Ib(+) CMR vs Temperature
DS011926-A2
Ib(−) CMR vs Temperature
DS011926-A3
Isc(±) vs Temperature
DS011926-A4
Output Swing vs Temperature
DS011926-A5
Output Swing vs Temperature
DS011926-A6
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Page 16
Typical Applications
CURRENT FEEDBACK TOPOLOGY
For a conventional voltage feedback amplifier the resulting small-signal bandwidth is inversely proportional to the de­sired gain to a first order approximation based on the gain-bandwidth concept. In contrast, the current feedback amplifier topology,such as the LM6182, transcends this limi­tation to offer a signal bandwidth that is relatively indepen­dent of the closed loop gain.
Figure 1A
and
Figure 1B
illus­trate that for closed loop gains of −1 and −5 the resulting pulse fidelity suggests quite similiar bandwidths for both configurations.
FEEDBACK RESISTOR SELECTION: R
f
Selecting the feedback resistor, Rf, is a dominant factor in compensating the LM6182. For general applications the LM6182 will maintain specified performance with an 820Ω feedback resistor.The closed-loop bandwidth of the LM6182 depends on the feedback resistance, R
f
. Therefore, Rs, and
not R
f
, is varied to adjust for the desired closed-loop gain as
demonstrated in
Figure 2
.
Although this R
f
value will provide good results for most ap­plications, it may be advantageous to adjust this value slightly.Consider, for instance, the effect on pulse responses with two different configurations where both the closed-loop gains are +2 and the feedback resistors are 820Ω, and 1640Ω, respectively.
Figure 3A
and
Figure 3B
illustrate the
effect of increasing R
f
while maintaining the same closed-loop gain – the amplifier bandwidth decreases. Ac­cordingly, larger feedback resistors can be used to slow down the LM6182 and reduce overshoot in the time domain response. Conversely, smaller feedback resistance values than 820Ω can be used to compensate for the reduction of bandwidth at high closed-loop gains, due to 2nd order ef­fects. For example
Figure 4A
and
Figure 4B
illustrate reduc-
ing R
f
to 500Ω to establish the desired small signal response
in an amplifier configured for a closed-loop gain of +25.
DS011926-20
1A. A
V
=
−1
DS011926-21
1B. A
V
=
−5
FIGURE 1. Variation of Closed-Loop Gain from −1 to −5
Yields Similar Responses.
DS011926-22
FIGURE 2. RfSets Amplifier Bandwidth and Rsis
Adjusted to Obtain the Desired Closed-Loop Gain, A
V
.
DS011926-23
3A. R
f
=
820Ω
DS011926-24
3B. R
f
=
1640Ω
FIGURE 3. Increase Compensation by Increasing
R
f,AV
=
+2
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Page 17
Typical Applications (Continued)
The extent of the amplifier’s dependence on R
f
is displayed
in
Figure 5
for one particular closed-loop gain.
CAPACITIVE FEEDBACK
Current feedback amplifiers rely on feedback impedance for proper compensation. Even in unity gain current feedback amplifiers require a feedback resistor. LM6182 performance is specified for a feedback resistance of 820Ω. Decreasing the feedback impedance below 820Ω extends the amplifier’s
bandwidth leading to possible instability. Capacitive feed­back should therefore not be used because the impedance of a capacitor decreases with increasing frequency.
For voltage feedback amplifiers it is quite common to place a small lead compensation capacitor in parallel with feedback resistance, R
f
. This compensation serves to reduce the am­plifier’s peaking. One application of the lead compensation capacitor is to counteract the effects of stray capacitance from the inverting input to ground in circuit board layouts. The LM6182 current feedback amplifier does not require this lead compensation capacitor and has an even simpler, more elegant solution.
To limit the bandwidth and peaking of the LM6182 current feedback amplifier, do not use a capacitor across R
f
as in
Figure 7
. This actually has the opposite effect and extends the bandwidth of the amplifier leading to possible instability. Instead, simply increase the value of the feedback resistor as shown in
Figure 3
.
Non-inverting applications can also reduce peaking and limit bandwidth by adding an RC circuit as illustrated in
Figure 8
.
DS011926-25
4A. R
f
=
820Ω
DS011926-26
4B. R
f
=
500Ω
FIGURE 4. , 4B. Reducing R
f
to Increase Bandwidth for
Large Closed-Loop Gains, A
V
=
+25
DS011926-27
FIGURE 5. −3 dB Bandwidth Is Determined By
Selecting R
f
.
DS011926-28
FIGURE 6. Current Feedback Amplifiers are Unstable
with Capacitive Feedback
DS011926-29
FIGURE 7. Compensation Capacitors Are Not Used
with the LM6182, Instead Simply Increase R
f
to
Compensate
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Page 18
Typical Applications (Continued)
SLEW RATE CONSIDERATIONS
DRIVING CAPACITIVE LOADS
The LM6182 can drive significantly larger capacitive loads than many current feedback amplifiers. This is extremely valuable for simplifying the design of coax-cable drivers. Al­though the LM6182 can directly drive as much as 100 pF of load capacitance without oscillating, the resulting response will be a function of the feedback resistor value.
Figure 9B
il­lustrates the small-signal pulse response of the LM6182 while driving a 50 pF load. Ringing persists for approximately 100 ns. To achieve pulse responses with less ringing either the feedback resistor can be increased (see Typical Perfor­mance Characteristics “Suggested R
f
and Rs for CL”), or re­sistive isolation can be used (10Ω–51Ω typically works well). Either technique, however, results in lowering the system bandwidth.
Figure 10B
illustrates the improvement obtained by using a
47Ω isolation resistor.
DS011926-30
8A
DS011926-31
8B
FIGURE 8. RC Limits Amplifier Bandwidth to 50 MHz, Eliminating Peaking in the Resulting Pulse Response
as Compared to
Figure 3A
DS011926-32
9A
DS011926-33
9B
FIGURE 9. A
V
=
−1, LM6182 Can Directly Drive 50 pF of
Load Capacitance with 100 ns of Ringing Resulting in
Pulse Response
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Page 19
Typical Applications (Continued)
POWER SUPPLY BYPASSING AND LAYOUT CONSIDERATIONS
A fundamental requirement for high-speed amplifier design is adequate bypassing of the power supply. It is critical to maintain a wideband low-impedance to ground at the ampli­fiers supply pins to insure the fidelity of high speed amplifier transient signals. 0.1 µF ceramic bypass capacitors at each supply pin are sufficient for many applications. Typically 10 µF tantalum capacitors are also required if large current transients are delivered to the load. The bypass capacitors should be placed as close to the amplifier pins as possible, such as 0.5" or less.
Applications requiring high output power, cable drivers for example, cause increased internal power dissipation. Inter­nal power dissipation can be minimized by operating at re­duced power supply voltages, such as
±
5V.
Optimum heat dissipation is achieved by using wide circuit board traces and soldering the part directly onto the board. Large power supply and ground planes will improve power dissipation. Safe Operating Area (S.O.A.) is determined us­ing the Maximum Power Derating Curves.
The 16-pin small outline package (M) has 5 V− heat sinking pins that enable a junction-to-ambient thermal resistance of 70˚C/W when soldered to 2 in
2
1 oz. copper trace. A V− heat sinking pin is located on each corner of the package for ease of layout. This allows high output power and/or operation at elevated ambient temperatures without the additional cost of an integrated circuit heat sink. If the heat sinking capabilities
of the S.O. package are not needed, pin 4 and at least one of pins 1,8,9, or 16 must be connected to V− for proper op­eration.
Figure 11
shows recommended copper patterns used to dis-
sipate heat from the LM6182.
CROSSTALK REJECTION
The LM6182 has an excellant crosstalk rejection value of 62 dB at 10 MHz. This value is made possible because the LM6182 amplifiers share no common circuitry other than the supply. High frequency crosstalk that does appear is prima­rily caused by the magnetic and capacitive coupling of the in­ternal bond wires. Bond wires connect the die to the package lead frame. The amount of current flowing through the bond wires is proportional to the amount of crosstalk. Therefore, crosstalk rejection ratings will degrade when driving heavy loads.
Figure 12
and shows a 10 dB difference for two differ-
ent loads.
DS011926-34
10A
DS011926-35
10B
FIGURE 10. Resistive Isolation of C
L
Provides Higher
Fidelity Pulse Response. R
f
and Rs Could Also Be
Increased to Maintain A
V
=
−1 and Improve Pulse
Response Characteristics.
DS011926-36
8-pin DIP (N)
DS011926-37
16-pin S.O. (M)
FIGURE 11. Copper Heatsink Layouts
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Page 20
Typical Applications (Continued)
The LM6182 crosstalk effect is minimized in applications that cascade the amplifiers by preceding amplifier A with ampli­fier B.
START-UP TIME
Using the circuit in
Figure 13
, the LM6182 demonstrated a
start-up time of 50 ns.
OVERDRIVE RECOVERY
The LM6182 is an excellent choice for high speed applica­tions needing fast overdrive recovery. Nanosecond recovery times allow the LM6182 to protect subsequent stages from excessive input saturation and possible damage.
When the output or input voltage range of a high speed am­plifier is exceeded, the amplifier must recover from an over­drive condition. The non-linear output voltage remains as long as the overdrive condition persists. Linear operation re­sumes after the overdrive condition is removed. Overdrive recovery time is the delay before an amplifier returns to lin­ear operation. The typical recovery times for exceeding open loop, closed loop, and input commom-mode voltage ranges are illustrated in
Figures 14, 15, 16
.
The open-loop circuit of
Figure 14
generates an overdrive re-
sponse by allowing the
±
0.5V input to exceed the linear in­put range of the amplifier.Typical positive and negative over­drive recovery times are 5 ns and 30 ns, respectively.
The large closed-loop gain configuration in
Figure 15
forces the amplifier output into overdrive. The typical recovery time to a linear output value is 15 ns.
DS011926-38
FIGURE 12. Crosstalk Rejection
DS011926-39
FIGURE 13. Start-Up Test Circuit
DS011926-41
DS011926-42
FIGURE 14. Open Loop Overdrive Recovery Times of
5 ns and 30 ns
DS011926-43
DS011926-44
FIGURE 15. 15 ns Closed Loop Output Overdrive
Recovery Time Generated by Saturating the Output
Stage of the LM6182
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Page 21
Typical Applications (Continued)
The common-mode input range of a unity-gain circuit is ex­ceeded by a 4V pulse resulting in a typical recovery time of 20 ns shown in
Figure 16
.
SPICE MACROMODEL
A spice macromodel is available for the LM6182. Contact your local National Semiconductor sales office to obtain an operational amplifier spice model library disk.
Typical Application Circuits
UNITY GAIN AMPLIFIER
The LM6182 current feedback amplifier is unity gain stable. The feedback resistor, R
f
, is required to maintain the
LM6182’s dynamic performance.
NON-INVERTING GAIN AMPLIFIER
Current feedback amplifiers can be used in non-inverting gain and level shifting functions. The same basic closed-loop gain equation used for voltage feedback amplifiers applies to current feedback amplifiers:1+R
f
/Rs.
INVERTING GAIN AMPLIFIER
The inverting closed loop gain equation used with voltage feedback amplifiers also applies to current feedback amplifiers.
SUMMING AMPLIFIER
The current feedback topology of the LM6182 provides sig­nificant performance advantages over a conventional volt­age feedback amplifier used in a standard summing circuit. Using a voltage feedback amplifier, the bandwidth of the summing circuit in
Figure 20
is limited by the highest gain needed for either signal V1 or V2. If the LM6182 amplifier is used instead, wide circuit bandwidth can be maintained rela­tively independent of gain requirements.
DS011926-45
DS011926-46
FIGURE 16. Output Recovery from an Input that
Exceeds the Common-Mode Range
DS011926-47
FIGURE 17. LM6182 Is Unity Gain Stable
DS011926-48
FIGURE 18. Non-Inverting Closed Loop Gain is
Determined with the Same Equation Voltage Feedback
Amplifiers Use:1+R
f
/Rs
DS011926-49
FIGURE 19. Current Feedback Amplifiers Can Be Used
for Inverting Gains, Just Like a Voltage Feedback
Amplifier: −R
f
/Rs
DS011926-50
FIGURE 20. LM6182 Allows the Summing Circuit to
Meet the Requirements of Wide Bandwidth Systems
Independent of Signal Gain
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Page 22
Ordering Information
Package Temperature Range NSC
Drawing
Military Industrial
−55˚C to +125˚C −40˚C to +85˚C
8-pin LM6182AMN LM6182AIN Molded LM6182IN N08E DIP 16-pin LM6182AIM Small LM6182IM M16A Outline
If Military/Aerospace specified devices are required, contact the National Semiconductor Sales Office or Distributors for availability and specifications.
www.national.com 22
Page 23
Physical Dimensions inches (millimeters) unless otherwise noted
14-Lead Dual-In-Line Package (J)
Order Number LM6182AMJ/883
NS Package Number J14A
Small Outline Package (M)
Order Number LM6182IM or LM6182AIM
NS Package Number M16A
www.national.com23
Page 24
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
National Semiconductor Corporation
Americas Tel: 1-800-272-9959 Fax: 1-800-737-7018 Email: support@nsc.com
National Semiconductor Europe
Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com Deutsch Tel: +49 (0) 1 80-530 85 85 English Tel: +49 (0) 1 80-532 78 32 Français Tel: +49 (0) 1 80-532 93 58 Italiano Tel: +49 (0) 1 80-534 16 80
National Semiconductor Asia Pacific Customer Response Group
Tel: 65-2544466 Fax: 65-2504466 Email: sea.support@nsc.com
National Semiconductor Japan Ltd.
Tel: 81-3-5639-7560 Fax: 81-3-5639-7507
www.national.com
Dual-In-Line Package (N)
Order Number LM6182IN, LM6182AIN, or LM6182AMN
NS Package Number N08E
LM6182 Dual 100 mA Output, 100 MHz Current Feedback Amplifier
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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