Chapter 4 Linear Power Amplifier Integrated Circuits 160 4.1 OPA548 Operational Amplifier IC The OPA548 is a high voltage/high current operational amplifier made by Burr-Brown. 159 4 Linear Power Amplifier Integrated Circuits Introduction The most convenient way to control power to a load is with a power op amp. These op amps have characteristics that are very similar to the low power ICs. However, they may be powered by over 50 V at 5 A. Working with this much voltage and current requires that you accurately

The most convenient way to control power to a load is with a power op amp. These op amps have characteristics that are very similar to the low power ICs. However, they may be powered by over 50 V at 5 A. Working with this much voltage and current requires that you accurately anticipate the power delivered to the load, the power provided by the dc supplies and the power that the op amp itself must dissipate. The power that the op amp dissipates is converted to heat. To move that heat from the silicon wafer requires effective heat sinking. Should a failure occur (by breakdown of a component, or because you botched the heat sink design), thermal shutdown allows the op amp to turn itself off. On- chip current limiting also allows you to set the maximum current the IC delivers to the load. This protects the load during a failure. Audio power ICs have several special problems. Often you must run them from a single battery. Noise and total harmonic distortion are critical issues, as are circuit features such as bass or treble boost. You will see a low power tabletop amplifier IC and a 56 W boomer IC. Objectives By the end of this chapter, you will be able to: • Determine the gain setting resistors and decoupling capacitors needed by a high voltage, high current, op amp based amplifier. • Calculate the power delivered to the load, provided by the supply and dissipated by the IC. • Calculate the IC and the case temperature and select the heat sink. • Set the short circuit current limiting. • Define special audio amplifier concerns and parameters. • Properly apply a desktop amp, and a high power audio amplifier IC.

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