Datasheet

LMC6022
www.ti.com SNOS622D –NOVEMBER 1994–REVISED MARCH 2013
(a) Inverting Amplifier Guard Ring Connections (b) Non-Inverting Amplifier Guard Ring Connections
(c) Follower Guard Ring Connections (d) Howland Current Pump Guard Ring Connections
Figure 30. Guard Ring Connections
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 insulator. Air is an
excellent insulator. In this case you may have to forego some of the advantages of PC board construction, but
the advantages are sometimes well worth the effort of using point-to-point up-in-the-air wiring. See Figure 31.
(Input pins are lifted out of PC board and soldered directly to components. All other pins connected to PC board.)
Figure 31. Air Wiring
BIAS CURRENT TESTING
The test method of Figure 32 is appropriate for bench-testing bias current with reasonable accuracy. To
understand its operation, first close switch S2 momentarily. When S2 is opened, then
(1)
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