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

8.

Application Circuits

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FIGURE 6. Examples of Guard

Ring in PC Board Layout

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Inverting Amplifier

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Non-Inverting Amplifier

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Follower

FIGURE 7. Typical Connections of Guard Rings

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(Input pins are lifted out of PC board and soldered directly to components.

All other pins connected to PC board).

FIGURE 8. Air Wiring

DC Summing Amplifier (V

DS012049-18

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