LMC6492 Datasheet, PDF (13/18 Pages) National Semiconductor (TI) – CMOS Rail-to-Rail Input and Output Operational Amplifier

Application Notes (Continued)
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FIGURE 6. Examples of Guard
Ring in PC Board Layout
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Inverting Amplifier
Non-Inverting Amplifier
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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
Application Circuits
DC Summing Amplifier (V_IN ≥ 0V_DC and V_O ≥ V_DC
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Follower
FIGURE 7. Typical Connections of Guard Rings
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.
Where: V₀ = V₁ + V₂ − V₃ – V₄
(V₁ + V₂ ≥ (V₃ + V₄) to keep V₀ > 0V_DC
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