Microchip Technology MCP6N16, Руководство пользователя, Страница: 23 / 36

Installation and Operation

2015 Microchip Technology Inc. DS50002365A-page 23
2.4.3.3 INA GAIN SELECTION
The evaluation board allows users to quickly set the gain on the MCP6N16 to either
101V/V or 301V/V by setting the jumper on J9 (labeled Gain Select) accordingly. Note
that the feedback resistors R11 and R16 are populated with a tolerance of only 0.1%
(instead of the standard 1%) to provide a higher gain accuracy. The gain is set with two
external resistors and follows the relationship shown in
Equation 2-3 .
EQUATION 2-3:
The transfer function of the MCP6N16 is given as shown in Equation 2-4 .
EQUATION 2-4:
Table 2-3 lists suggested resistor values for the feedback (R
F
) and gain resistors (R
G
),
using 1% standard resistor, for a desired gain. Large value resistors should be avoided
as they may start to contribute noise. To keep the output loading minimal and maintain
optimum linearity the selection of the gain setting resistors should take any additional
load resistance into account, according to
Equation 2-5 .
EQUATION 2-5:
Capacitor C11 in combination with R16 can be added to the feedback network to form
an additional low-pass filter of approximately 800 Hz (with C11 = 0.01 µF). This may be
used as an alternate filter option instead of the common/differential-mode RC filter at
the output of the MCP6N16 consisting of R8, R19, C8, C10, C12.
TABLE 2-3: SUGGESTED RESISTOR VALUES FOR VARIOUS GAINS
Gain
(V/V) R
F
(Ohm, 1%)
R
G
(Ohm, 1%)
MCP6N16-001 MCP6N16-010 MCP6N16-100
1 Short None Yes No No
2 10 k Ω 10 k Ω Yes No No
5 20 k Ω 4.99 k Ω Yes No No
10.1 9.09 k Ω 1 k Ω Yes Yes No
20.1 19.1 k Ω 1 k Ω Yes Yes No
49.7 24.3 k Ω 499 Ω Yes Yes No
101 10 k Ω 100 Ω Yes Yes Yes
301 30 k Ω 100 Ω Yes Yes Yes
500 24.9 k Ω 49.9 Ω Yes Yes Yes
1001 49.9 k Ω 49.9 Ω Yes Yes Yes
Note:
The MCP6N16-100 is internally compensated to be used for gains higher
or equal to 100. If lower gains are desired, consider using alternate models,
for example the MCP6N16-010 for gains higher or equal to 10, or the
MCP6N16-001 for gains higher or equal to 1.
G1 1
R11
R18
---------- 101 = + =
G2
1 R11 R16 +
 
+
R18
------------------------------------------ 301 = =
Differential Signal Gain:
V
OUT
= G (V
IP
- V
IM
) + V
REF
(R
F
+ R
G
)|| R
L
≥ 10 k Ω