Application Information

GENERAL

Twenty five years ago the operational amplifier was a spe-

cialized design tool used primarily for analog computation.

However, the availability of low cost IC op amps in the late

1960’s prompted their use in rather mundane applications,

replacing a few discrete components. Once a few basic prin-

ciples are mastered, op amps can be used to give exception-

ally good results in a wide range of applications while mini-

mizing both cost and design effort.

The availability of a monolithic power op amp now promises

to extend these advantages to high-power designs. Some

conventional applications are given here to illustrate op amp

design principles as they relate to power circuitry. The inevi-

table fall in prices, as the economies of volume production

are realized, will prompt their use in applications that might

now seem trivial. Replacing single power transistors with an

op amp will become economical because of improved per-

formance, simplification of attendant circuitry, vastly im-

proved fault protection, greater reliability and the reduction of

design time.

Power op amps introduce new factors into the design equa-

tion. With current transients above 10A, both the inductance

and resistance of wire interconnects become important in a

number of ways. Further, power ratings are a crucial factor in

determining performance. But the power capability of the IC

cannot be realized unless it is properly mounted to an ad-

equate heat sink. Thus, thermal design is of major impor-

tance with power op amps.

This application summary starts off by identifying the origin

of strange problems observed while using the LM12 in a

Frequency Response

DS008704-43

Output Impedance

DS008704-44

Power Supply Rejection

DS008704-45

Input Bias Current

DS008704-46

Input Noise Voltage

DS008704-47

Common Mode Rejection

DS008704-48

Supply Current

DS008704-49

Supply Current

DS008704-50

Cross-Supply Current

DS008704-51

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