LF355 datasheet(34/47 Pages) TI2

34 / 47 page

LF155, LF156, LF256, LF257

LF355, LF356, LF357

SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015

www.ti.com

Layout Guidelines (continued)

Figure 60. Typical Connections Of Guard Rings

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 61.

(Input pins are lifted out of PCB and soldered directly to components. All other pins connected to PCB).

Figure 61. Air Wiring

Another potential source of leakage that might be overlooked is the device package. When the LFx5x 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 62. Examples Of Guard

Ring In PCB Layout

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LF355 Datasheet(PDF) 34 Page - Texas Instruments