OPA454_16 Datasheet, PDF (37/47 Pages) Texas Instruments – High-Voltage (100-V), High-Current (50-mA) Operational Amplifiers

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Power Dissipation (continued)
OPA454
SBOS391B – DECEMBER 2007 – REVISED MARCH 2016
R₁
100kW
V₁
R3
100kW
V₂
R₂
10kW
+50V
-IN
V+
OPA454
+IN
V_OUT
V-
R₄
-50V ^9.9kW
R₅
100W
I_L
R_L
I_L = [(V₂ - V₁)/R₅] (R₂/R₁)
= (V₂ - V₁)/1kW
Compliance Voltage Range = +47V, -48V
NOTE: R₁ = R₃ and R₂ = R₄ + R₅.
Figure 87. Precision Voltage-to-Current Converter With Differential Inputs
12.5 Heatsinking
Power dissipated in the OPA454 causes the junction temperature to rise. For reliable operation, junction
temperature must be limited to 125°C, maximum. Maintaining a lower junction temperature always results in
higher reliability. Some applications require a heatsink to assure that the maximum operating junction
temperature is not exceeded. Junction temperature can be determined according to Equation 3:
T =T +P q
J
A
D JA
(3)
Package thermal resistance, θ_JA, is affected by mounting techniques and environments. Poor air circulation and
use of sockets can significantly increase thermal resistance to the ambient environment. Many op amps placed
closely together also increase the surrounding temperature. Best thermal performance is achieved by soldering
the op amp onto a circuit board with wide printed circuit traces to allow greater conduction through the op amp
leads. Increasing circuit board copper area to approximately 0.5 in² decreases thermal resistance; however,
minimal improvement occurs beyond 0.5 in², as shown in Figure 88.
For additional information on determining heatsink requirements, consult Application Bulletin SBOA021 (available
for download at www.ti.com).
60
50
40
30
20
10
0
0
0.5
1.0
1.5
2.0
2.5
3.0
Copper Area (inches²), 2 oz
Figure 88. Thermal Resistance vs Circuit Board Copper Area
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