The low power consumption of the OPAx596 causes minimal self-heating even in a small SOT23-5 package as

given by Equation 5. In a loaded condition, PD is equal to addition of the quiescent power, PDQ and the power

dissipated by the output stage, PDL. The worst-case condition is given when the output voltage is equal to ½

of either supply rail (assuming symmetrical supplies, V+ and V-). In a worst-case condition, PDL is given by

Equation 6.

PDL= V+ 24×RL

(6)

For example, assume the OPAx596 is powered with bipolar ±42.5V power supplies and drives a 5kΩ load, RL, to

ground. The maximum increase in TJ is expected to be about 22°C as given by Equation 7. In this example, to

keep the op amp within the Absolute Maximum Ratings, operate in TA well under 128°C to account for different

factors. The calculation for a 5kΩ load is depicted visually in Figure 7-8.

∆TJ= 41.7mW+90.3mW ×165.4°CW

(7)

For high-voltage amplifiers such as the OPAx596, the junction temperature can easily be tens of degrees

higher than the ambient temperature in a quiescent (unloaded) condition. As shown by Equation 3, the junction

temperature depends on the thermal properties of the package, as expressed by the junction-to-ambient thermal

resistance (RϴJA). If the device then begins to drive a heavy load, the junction temperature can rise and trip

the thermal-shutdown circuit. Figure 7-8 shows the maximum output voltage versus ambient temperature to

avoid exceeding the Absolute Maximum Ratings in both loaded and unloaded conditions for the SOT23-5

package version of the OPA596. The curve assumes a typical quiescent current and does not account for any

temperature variation of quiescent current.

Ambient Temperature ( C)

85

95

105

115

125

135

145

0

10

20

30

40

50

60

70

80

90

100

Unloaded

Loaded (2k )

Loaded (10k )

Figure 7-8. OPA596 (SOT23-5) Thermal Safe Operating Area

OPA596

SBOSA42A – JUNE 2024 – REVISED FEBRUARY 2025

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