LT1010_15 Datasheet, PDF (12/20 Pages) Linear Technology – Fast 150mA Power Buffer

LT1010
APPLICATIONS INFORMATION
excellent matching of the feedback resistors is required to
get high output resistance. Output is bidirectional.
R1
100k
0.01%
V1
R2
100k
0.01%
I_OUT
=
R2(V2 – V1)
R1R4
R3
100k
0.01%
V2
–
A1
LT1012
+
A2
LT1010
R4
100k
0.01%
R4
10Ω
0.1%
I_OUT
1010 AI13
This circuit uses an instrumentation amplifier to eliminate
the matched resistors. The input is not high impedance
and must be driven from a low impedance source like
an op amp. Reversal of output sense can be obtained by
grounding Pin 7 of the LM163 and driving Pin 5.
A2
LT1010
I_OUT
=
V_IN
10R1
R1
V_IN
10Ω
7
2
0.1%
6
A1
I_OUT
LM163
×10 3
5
1010AI14
Output resistances of several megohms can be obtained
with both circuits. This is impressive considering the
±150mA output capability. High frequency output charac-
teristics will depend on the bandwidth and slew rate of the
amplifiers. Both these circuits have an equivalent output
capacitance of about 30nF.
Voltage/Current Regulator
This circuit regulates the output voltage at V_V until the load
current reaches a value programmed by V_I. For heavier
loads, it is a precision current regulator.
With output currents below the current limit, the current
regulator is disconnected from the loop by D1 with D2
keeping its output out of saturation. This output clamp
12
–
A1
+^LT118A
D1
1N457
R1
2k
C2
10pF
V_V
1V/V
R2
C1
2k
1nF
A2
LT1010
D2
1N457
A3
LT118A
R7
99.8k
0.1%
R3
2Ω
R4
2k
0.1%
OUTPUT
R5
2k
0.1%
R6
99.8k
0.1%
V_I
10mA/V
1010 AI15
enables the current regulator to get control of the output
current from the buffer current limit within a microsecond
for an instantaneous short.
In the voltage regulation mode, A1 and A2 act as a fast
voltage follower using the capacitive load isolation tech-
nique described earlier. Load transient recovery as well as
capacitive load stability are determined by C1. Recovery
from short circuit is clean.
Bidirectional current limit can be obtained by adding another
op amp connected as a complement to A3.
Supply Splitter
Dual supply op amps and comparators can be operated
from a single supply by creating an artificial ground at
half the supply voltage. The supply splitter shown here
can source or sink 150mA.
The output capacitor, C2, can be made as large as neces-
sary to absorb current transients. An input capacitor is
also used on the buffer to avoid high frequency instability
that can be caused by high source impedance.
R1
10k
C1 R2
1nF 10k
A1
LT1010
V⁺
C3
0.1µF
V⁺/2
C2
0.01µF
1010 AI16
1010fe