Texas Instruments THS4503EVM manual

Circuit pathways should be made as symmetrical as possible for both feedback pathways to minimize second and other even-harmonic content.

The printed-circuit board used with PowerPAD packages must have features included in the design to remove the heat from the package efficiently. As a minimum, there must be an area of solder-tinned-copper underneath the PowerPAD package. This area is called the thermal land. The thermal land varies in size depending on the PowerPAD package being used, the PCB construction and the amount of heat that needs to be removed. In addition, this thermal land may or may not contain thermal vias depending on PCB construction. The requirements for thermal lands and thermal vias are detailed in http://www−s.ti.com/sc/techlit/slma002 and http://www−s.ti.com/sc/techlit/slma004.

Finally, all inputs and outputs must be properly terminated, either in the layout or in the load instrumentation. Unterminated lines, such as coaxial cable, can appear to be a reactive load to the amplifier. By terminating a transmission line with its characteristic impedance, the amplifier’s load then appears to be purely resistive, and reflections are absorbed at each end of the line. Another advantage of using an output termination resistor is that capacitive loads are isolated from the amplifier output. This isolation helps minimize the reduction in the amplifier’s phase-margin and improves the amplifier stability resulting in reduced peaking and settling times.

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