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OPA2541

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pation (total of both amplifiers) times the appropriate ther-

mal resistance—

∆ T

Sufficient heat sinking must be provided to keep the case

temperature within safe limits for the maximum ambient

temperature and power dissipation. The thermal resistance

of the heat sink required may be calculated by:

θ

Commercially available heat sinks usually specify thermal

resistance. These ratings are often suspect, however, since

they depend greatly on the mounting environment and air

flow conditions. Actual thermal performance should be

verified by measurement of case temperature under the

required load and environmental conditions.

No insulating hardware is required when using the OPA2541.

Since mica and other similar insulators typically add

0.7

°C/W thermal resistance, this is a significant advantage.

See Burr-Brown Application Note AN-83 for further details

on heat sinking.

SAFE OPERATING AREA

The Safe Operating Area (SOA) curve provides comprehen-

sive information on the power handling abilities of the

OPA2541. It shows the allowable output current as a func-

tion of the voltage across the conducting output transistor

(see Figure 1). This voltage is equal to the power supply

voltage minus the output voltage. For example, as the

amplifier output swings near the positive power supply

voltage, the voltage across the output transistor decreases

and the device can safely provide large output currents

demanded by the load.

INSTALLATION

INSTRUCTIONS

POWER SUPPLIES

The OPA2541 is specified for operation from power sup-

plies up to

±40V. It can also be operated from an unbalanced

or a single power supply so long as the total power supply

voltage does not exceed 80V (70V for “AM” grade). The

power supplies should be bypassed with low series imped-

ance capacitors such as ceramic or tantalum. These should

be located as near as practical to the amplifier’s power

supply pins. Good power amplifier circuit layout is, in

general, like good high-frequency layout. Consider the path

of large power supply and output currents. Avoid routing

these connections near low-level input circuitry to avoid

waveform distortion and instability.

Signal dependent load current can modulate the power

supply voltage with inadequate power supply bypassing.

This can affect both amplifiers’ outputs. Since the second

amplifier’s signal may not be related to the first, this will

degrade the inherent channel separation of the OPA2541.

HEAT SINKING

Most applications will require a heat sink to prevent junction

temperatures from exceeding the 150

°C maximum rating.

The type of heat sink required will depend on the output

signals, power dissipation of each amplifier, and ambient

temperature. The thermal resistance from junction-to-case,

θ

the amplifier die.

DC output concentrates the power dissipation in one output

transistor. AC output distributes the power dissipation equally

between the two output transistors and therefore has lower

thermal resistance. Similarly, the power dissipation may be

all in one amplifier (worst case) or equally distributed

between the two amplifiers (best case). Thermal resistances

are provided for each of these possibilities. The case-to-

junction temperature rise is the product of the power dissi-

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