TL K 8628
LH4001
Wideband
Current
Buffer
February 1995
LH4001 Wideband Current Buffer
General Description
The LH4001 is a high speed unity gain buffer designed to
provide high current drive capability at frequencies from DC
to over 25 MHz It is capable of providing a continuous out-
put current of
g
100 mA and a peak of
g
200 mA
The LH4001 is designed to fulfill a wide range of applica-
tions such as impedance transformation high impedance
input buffers for A D converters and comparators as well
as high speed line drivers It is also suitable for use in cur-
rent booster applications within an op amp loop This allows
the output current capability of existing op amps to be in-
creased to
g
100 mA
Features
Y
DC to 25 MHz bandwidth
Y
125 V ms slew rate
Y
Drives
g
10V into 50X
Y
Operates from
g
5 to
g
20V supplies
Y
Output swing approaches supply voltage
Applications
Y
Boost op amp output
Y
Buffer amplifiers
Y
Isolate capacitive loads
Y
Drive long cables
Typical Applications and Connection Diagram
TL K 8628 1
Dual-In-Line Package
TL K 8628 2
Top View
Note
Electrically connected internally No connection should be made to these pins
Order Number LH4001CN
See NS Package Number N10A
C1995 National Semiconductor Corporation
RRD-B30M115 Printed in U S A
Absolute Maximum Ratings
If Military Aerospace specified devices are required
please contact the National Semiconductor Sales
Office Distributors for availability and specifications
Supply Voltage V
S
g
22V
Continuous Output Current I
O
g
100 mA
Peak Output Current I
O(peak)
(50 ms On 1 Sec Off)
g
200 mA
Input Voltage Range V
IN
g
V
S
Power Dissipation
500 mW
Storage Temperature Range T
STG
b
65 C to
a
150 C
Junction Temperature T
J
150 C
Lead Temp (Soldering
k
10 seconds)
260 C
ESD rating is to be determined
Operating Ratings
Temperature Range T
A
0 C to
a
70 C
Thermal Resistance i
JA
120 C W
Electrical Characteristics
(Note 1)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
A
V
Voltage Gain
R
S
e
10 kX R
L
e
1 kX
0 95
0 97
1
V V
V
IN
e
g
10V
R
IN
Input Impedance
R
S
e
200 kX R
L
e
1 kX
180
400
kX
V
IN
e
g
1 0V
R
OUT
Output Impedance
R
S
e
10 kX R
L
e
50X
6
10
X
V
IN
e
g
1 0V
V
O
Output Swing
V
S
e
g
15V R
S
e
50X
g
10
g
11
V
R
L
e
100X V
IN
e
g
12V
I
B
Input Bias Current
R
S
e
10 kX R
L
e
1 kX
g
10
g
50
m
A
t
r
Rise Time
R
L
e
100X DV
IN
e
100 mV
7
ns
SR
Slew Rate
V
IN
e
g
5V R
L
e
100X
125
V ms
I
S
Supply Current
R
S
e
10 kX
g
6
g
10
mA
V
OS
Offset Voltage
R
S
e
300X R
L
e
1 kX
g
10
g
50
mV
Note 1
Specification applies for T
A
e
25 C with
a
12V on Pins 1
2
b
12V on Pins 4
5 unless otherwise specified
Typical Performance Characteristics
Input Offset Current
Frequency Response
Supply Current
TL K 8628 3
Pulse Response
TL K 8628 10
V
IN
e g
2 5V R
S
e
R
L
e
50X
2
Applications Information
Figure 1 shows a simple implementation of a non-inverting
buffer amplifier of unity gain Popular industry standard op-
erational amplifiers such as LF156 LF351 LF411 LF441
LM11 LM741 etc can be used in this configuration Due to
the high bandwidth of the LH4001 it is suitable for use with
most monolithic op amps
Figure 2 shows an implementation of an inverting amplifier
with output current capability in excess of
g
100 mA The
gain of this amplifier is determined by the values of R
F
and
R
IN
The resistor between the non-inverting input and
ground is used to minimize the output offset voltage result-
ing from the input bias current
Because of its high current drive capability the LH4001
buffer amplifier is suitable for driving terminated or untermi-
nated co-axial cables and high current or reactive loads
Figure 3 shows a co-axial cable drive circuit The 43X resis-
tor matches the driving source to the cable however its
inclusion rarely will result in substantial improvement in
pulse response into a terminated cable If the 43X resistor
is included the output voltage to the load is about half what
it would be without the near end termination
Figure 4 shows a non-inverting amplifier with gain and out-
put current capability in excess of
g
100 mA It is capable of
providing
g
10 mA into a 1 kX load or
g
100 mA into a
100X load (
g
10V swing)
Figures 5 and 6 show two differ-
ent methods of providing current limit or short circuit protec-
tion for the LH4001 In
Figure 6 the 10X resistor limits the
output current to approximately 70 mA This circuit is highly
recommended if there is a potential for a short circuit to
occur
TL K 8628 4
FIGURE 1 Non-Inverting Buffer Amplifier
V
OUT
V
IN
e b
R
F
R
IN
TL K 8628 6
FIGURE 2 Inverting Buffer Amplifier with Current Limit
3
Applications Information
(Continued)
R
LIM
e
100X 1W
TL K 8628 7
FIGURE 3 Coaxial Cable Drive Circuit
TL K 8628 5
V
OUT
e
V
IN
1
a
R2
R1
J
FIGURE 4 Non-Inverting Buffer Amplifier with Gain
TL K 8628 8
FIGURE 5 LH4001 Using Resistor Current Limiting
Q
1
Q
2
e
2N2905
Q
3
Q
4
e
2N2219
TL K 8628 9
FIGURE 6 Current Limit Using Current Sources
4
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