part itself, adding its own high frequency properties to the

overall performance of the circuit. It is good practice to have

at least one ground plane on a PCB giving a low impedance

path for all decoupling and other ground connections. In

order to achieve high immunity for unwanted signals from

outside, it is important to place the components as flat as

possible on the PCB. Be aware that a long lead can act as

an inductor, a capacitor or an antenna. A pair of leads can

even form a transformer. Careful design of the PCB avoids

oscillations or other unwanted behavior. Another important

issue is the value of components, which also determines the

sensitivity to pick-up unwanted signals. Choose the value of

resistors as low as possible, but avoid using values that

causes a significant increase in power consumption, while

loading inputs or outputs to heavily.

NSC suggests the following evaluation board as a guide for

high frequency layout and as an aid in device testing and

characterization.

Device

Package

Evaluation Board

PN

LMV115

SC70-6

LMV115/117 Eval

Board

This free evaluation board is shipped when a device sample

request is placed with National Semiconductor.

www.national.com

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