LMC6001 Datasheet, PDF (20/25 Pages) National Semiconductor (TI) – Ultra Ultra-Low Input Current Amplifier

LMC6001
SNOS694I – MARCH 1995 – REVISED SEPTEMBER 2015
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Layout Guidelines (continued)
The designer should be aware that when it is inappropriate to lay out a PCB for the sake of just a few circuits,
there is another technique which is even better than a guard ring on a PCB: Do not insert the input pin of the
amplifier into the board at all, but bend it up in the air and use only air as an insulator. Air is an excellent
insulator. In this case you may have to forego some of the advantages of PCB construction, but the advantages
are sometimes well worth the effort of using point-to-point up-in-the-air wiring. See Figure 29.
(Input pins are lifted out of PCB and soldered directly to components. All other pins connected to PCB).
Figure 29. Air Wiring
Another potential source of leakage that might be overlooked is the device package. When the LMC6001 is
manufactured, the device is always handled with conductive finger cots. This is to assure that salts and skin oils
do not cause leakage paths on the surface of the package. We recommend that these same precautions be
adhered to, during all phases of inspection, test and assembly.
10.2 Layout Example
Figure 30. Examples Of Guard
Ring In PCB Layout
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