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Op Amps for Everyone - The Repeater Builder's Technical ...

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References<br />

17.8.4 Routing<br />

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17.8.5 Bypass<br />

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Keep analog circuitry close to the power connector of the board.<br />

Never route digital traces through analog sections of the board, or vice versa.<br />

Make sure that traces to the inverting input of the op amp are short.<br />

Make sure that traces to the inverting and noninverting inputs of the op amp do not<br />

parallel each other <strong>for</strong> any significant length.<br />

It is better to avoid vias, but the self-inductance of vias is small enough that a few<br />

should cause few problems.<br />

Do not use right angle traces, use curves if at all possible.<br />

Use the correct type of capacitor to reject the conducted frequency range.<br />

Use tantalum capacitors at power input connectors <strong>for</strong> filtering power supply ripple.<br />

Use ceramic capacitors at power input connectors <strong>for</strong> high frequency conducted<br />

noise.<br />

Use ceramic capacitors at the power connections of every op amp IC package. More<br />

than one capacitor may be necessary to cover different frequency ranges.<br />

Change the capacitor to a smaller value — not larger — if oscillation occurs.<br />

Add series inductors or resistors <strong>for</strong> stubborn cases.<br />

Bypass analog power only to analog return, never to digital return.<br />

17.9 References<br />

1. Analog Dialog 30 th Anniversary Issue, Analog Devices, Ask the Applications Engineer<br />

–10, James Bryant<br />

2. High-Speed <strong>Op</strong>erational Amplifier Layout Made Easy, Texas Instruments, Andy Hahn,<br />

SLOA046<br />

Circuit Board Layout Techniques<br />

17-29

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