lmp8602mmx National Semiconductor Corporation, lmp8602mmx Datasheet - Page 17

• Manufacturer Part Number: lmp8602mmx
• Description: 60v Common Mode, Fixed Gain, Bidirectional Precision Current Sensing Amplifier
• Manufacturer: National Semiconductor Corporation

For the LMP8603:
Given a desired value of the reduced gain G
tion the required value for R
LMP8602 with:
and for the LMP8603 with:
Increase Gain
Figure 4 shows the configuration that can be used to increase
the gain of the LMP8602/LMP8603.
R
of the buffer amplifier. The positive feedback increases the
gain. The increased gain G
i
creates positive feedback from the output pin to the input
i
for the LMP8602 becomes:
r
can be calculated for the
r
, using this equa-
FIGURE 4. Increase Gain
17
and for the LMP8603:
From this equation, for a desired value of the gain, the re-
quired value of R
and for the LMP8603 with:
It should be noted from the equation for the gain G
large gains R
nator in the equation becomes close to zero. In practice, for
large gains the denominator will be determined by tolerances
in the value of the external resistor R
kΩ resistor. In this case, the gain becomes very inaccurate. If
the denominator becomes equal to zero, the system will even
become instable. It is recommended to limit the application of
this technique to gain increases of a factor 2.5 or smaller.
i
approaches 100 kΩ. In this case, the denomi-
i
can be calculated for the LMP8602 with:
30083457
i
and the internal 100
www.national.com
i
that for