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 6.

DS010547-19

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

DS010547-20

(a) Inverting Amplifier

DS010547-21

(b) Non-Inverting Amplifier

DS010547-22

(c) Follower

DS010547-23

(d) Howland Current Pump

FIGURE 5. Guard Ring Connections

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