Datasheet

© 2009-2011 Microchip Technology Inc. DS22188C-page 7
MCP621/1S/2/3/4/5/9
1.4 Test Circuits
The circuit used for most DC and AC tests is shown in
Figure 1-2. This circuit can independently set V
CM
and
V
OUT
; see Equation 1-1. Note that V
CM
is not the
circuit’s Common mode voltage ((V
P
+V
M
)/2), and that
V
OST
includes V
OS
plus the effects (on the input offset
error, V
OST
) of temperature, CMRR, PSRR and A
OL
.
EQUATION 1-1:
FIGURE 1-2: AC and DC Test Circuit for
Most Specifications.
G
DM
R
F
R
G
⁄ =
V
CM
V
P
V
DD
2 ⁄ +()2 ⁄ =
V
OUT
V
DD
2 ⁄ ()V
P
V
M
–()V
OST
1G
DM
+()++=
Where:
G
DM
= Differential Mode 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+
–=
V
DD
R
G
R
F
V
OUT
V
M
C
B2
C
L
R
L
V
L
C
B1
10 kΩ
10 kΩ
R
G
R
F
V
DD
/2
V
P
10 kΩ
10 kΩ
50 pF
2kΩ
2.2 µF100 nF
V
IN–
V
IN+
C
F
6.8 pF
C
F
6.8 pF
MCP62X