OPA454 Datasheet, PDF (17/36 Pages) Texas Instruments – High-Voltage (100V), High-Current (50mA) OPERATIONAL AMPLIFIERS, G = 1 Stable

OPA454
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INCREASING OUTPUT CURRENT
The OPA454 drives an output current of a few
milliamps to greater than 50mA while maintaining
good op amp performance. See Figure 7 for
open-loop gain versus temperature at various output
current levels.
In applications where the 25mA output current is not
sufficient to drive the required load, the output current
can be increased by connecting two or more
OPA454s in parallel, as Figure 59 shows. Amplifier
A1 is the master amplifier and may be configured in
virtually any op amp circuit. Amplifier A2, the slave, is
configured as a unity-gain buffer. Alternatively,
external output transistors can be used to boost
output current. The circuit in Figure 60 is capable of
supplying output currents up to 1A, with the
transistors shown.
UNITY-GAIN NONINVERTING
CONFIGURATION
When in the noninverting unity-gain configuration, the
OPA454 has more gain peaking with increasing
positive common-mode voltage and increasing
temperature. It has less gain peaking with more
negative common-mode voltage. As with all op amps,
gain peaking increases with increasing capacitive
load. A resistor and small capacitor placed in the
feedback path can reduce gain peaking and increase
stability.
R₁
R₂
+50V
R₁
V_IN
SBOS391 – DECEMBER 2007
R₂
MASTER
A1 OPA454
R_S(1)
10W
A2 OPA454
SLAVE
R_S(1)
10W
R_L
(1) R_S resistors minimize the circulating current that always flows
between the two devices because of V_OS errors.
Figure 59. Parallel Amplifiers Increase Output
Current Capability
NPN
TIP29C, MJL21194,
C_F
MJE15003, MJL3281
R₄
-IN
V+
V_OUT(2)
R₃₍₁₎
20W
0.2W
OPA454
+IN
V_IN
V-
R₅
0.2W
V_O(3) = V_OUT - I_LR_L
R_L I_L
PNP
TIP30C, MJL21193,
MJE15004, MJL1302A
-50V
(1) Provides current limit for OPA454 and allows the amplifier to drive the load when the output is between +0.7V and –0.7V.
(2) Op amp V_OUT swings from +47V to –48V.
(3) V_O swings from +44.1V to –45.1V at I_L = 1A.
Figure 60. External Output Transistors Boost Output Current Greater Than 1A
Copyright © 2007, Texas Instruments Incorporated
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