LMC6081AIM National Semiconductor, LMC6081AIM Datasheet - Page 8

• Manufacturer Part Number: LMC6081AIM
• Description: Operational Amplifier (Op-Amp) IC
• Manufacturer: National Semiconductor

Specifications of LMC6081AIM

• No. Of Amplifiers: 1
• Slew Rate: 1.5V/µs
• No. Of Pins: 8
• Peak Reflow Compatible (260 C): No
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Package / Case: 8-NSOIC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Applications Hints
ure 4 . To have a significant effect, guard rings should be
placed on both the top and bottom of the PC board. This PC
foil must then be connected to a voltage which is at the same
voltage as the amplifier inputs, since no leakage current can
flow between two points at the same potential. For example,
a PC board trace-to-pad resistance of 10
mally considered a very large resistance, could leak 5 pA if
the trace were a 5V bus adjacent to the pad of the input. This
would cause a 100 times degradation from the LMC6081’s
actual performance. However, if a guard ring is held within
5 mV of the inputs, then even a resistance of 10
cause only 0.05 pA of leakage current. See Figure 5 for typi-
cal connections of guard rings for standard op-amp
configurations.
FIGURE 4. Example of Guard Ring in P.C. Board
Layout
(Continued)
12
, which is nor-
11
DS011423-6
would
8
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
See Figure 6 .
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board).
Latchup
CMOS devices tend to be susceptible to latchup due to their
internal parasitic SCR effects. The (I/O) input and output pins
look similar to the gate of the SCR. There is a minimum cur-
FIGURE 5. Typical Connections of Guard Rings
of
using
Non-Inverting Amplifier
FIGURE 6. Air Wiring
Inverting Amplifier
point-to-point
Follower
up-in-the-air
DS011423-9
DS011423-7
DS011423-8
DS011423-10
wiring.