The designer should be aware that when it is inappropriate

to lay out a PC board for the sake of just a few circuits, there

is another technique which is even better than a guard ring

on a PC board: Don’t insert the amplifier’s input pin into the

board at all, but bend it up in the air and use only air as an in-

sulator. Air is an excellent insulator. In this case you may

have to forego some of the advantages of PC board con-

struction, but the advantages are sometimes well worth the

effort of using point-to-point up-in-the-air wiring. See

Figure

9.

DS011227-8

FIGURE 4. Example of Guard Ring in P.C. Board Layout, Using the LPC660

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FIGURE 5. Inverting Amplifier

Guard Ring Connections

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FIGURE 6. Non-Inverting Amplifier

Guard Ring Connections

DS011227-11

FIGURE 7. Follower

Guard Ring Connections

DS011227-12

FIGURE 8. Howland Current Pump

Guard Ring Connections

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