Datasheet

© 2009 Microchip Technology Inc. DS22196A-page 5
MCP6286
1.2 Test Circuits
The circuit used for most DC and AC tests is shown in
Figure 1-1. It independently sets V
CM
and V
OUT
; see
Equation 1-1. The circuit’s common mode voltage is
(V
P
+V
M
)/2, not V
CM
. V
OST
includes V
OS
plus the
effects of temperature, CMRR, PSRR and A
OL
.
EQUATION 1-1:
FIGURE 1-1: AC and DC Test Circuit for
Most Specifications.
G
DM
R
F
R
G
⁄ =
V
CM
V
P
11G
N
⁄–()V
REF
1 G
N
⁄()+=
V
OUT
V
REF
V
P
V
M
–()G
DM
V
OST
G
N
++=
Where:
G
DM
= Differential Mode Gain (V/V)
G
N
= Noise Gain (V/V)
V
CM
= Op Amp’s Common Mode
Input Voltage
(V)
V
OST
= Op Amp’s Total Input Offset
Voltage
(mV)
V
OST
V
IN–
V
IN+
–=
G
N
1 G
DM
+=
V
DD
MCP6286
R
G
R
F
V
OUT
V
M
C
B2
C
L
R
L
V
L
C
B1
100 kΩ
100 kΩ
R
G
R
F
V
REF
= V
DD
/2
V
P
100 kΩ
100 kΩ
60 pF
10 kΩ
1µF100 nF
V
IN–
V
IN+
C
F
6.8 pF
C
F
6.8 pF