MCP6N16
1.5.3
DIFFERENTIAL GAIN ERROR AND
NONLINEARITY
The differential errors are extracted from differential
gain measurements (see Section 1.4.2 “Differential
Gain Test Circuit”), based on Equation 1-2. These
errors are the differential gain error (gE) and the input
offset error (VE, which changes nonlinearly with VDM):
EQUATION 1-8:
GDM = 1 + RF RG
VM = GDM1 + gEVDM + VE
These errors are adjusted for the expected output, then
referred back to the input, giving the differential input
error (VED) as a function of VDM:
EQUATION 1-9:
VED = VM GDM – VDM
Figure 1-10 shows VED vs. VDM, as well as a linear fit
line (VED_LIN) based on VED and gE. The INA is in
standard conditions (∆VOUT = 0, etc.). VDM is swept
from VDML to VDMH.
VED, VED_LIN (V)
V3
V2
VED_LIN
VED
EQUATION 1-11:
INLDMH = maxVED VDMH – VDML
INLDML = minVED VDMH – VDML
INLDM = INLDMH INLDMH INLDML
= INLDML otherwise
Where:
VED = VED – VED_LIN
V1
VED
VDML
0
VDMH
VDM (V)
FIGURE 1-10:
Differential Input Error vs.
Differential Input Voltage.
Based on the measured VED data, we obtain the
following linear fit:
EQUATION 1-10:
VED_LIN = 1 + gEVE + gEVDM
Where:
gE = V3 – V1 VDMH – VDML – 1
VE = V2 1 + gE
Note that the VE value measured here is not as
accurate as the one obtained in Section 1.5.1 “Input
Offset Related Errors”.
The remaining error (∆VED) is described by the
Differential Nonlinearity spec:
DS20005318A-page 16
2014 Microchip Technology Inc.