MCP6272 Microchip Technology Inc., MCP6272 Datasheet - Page 15

• Manufacturer Part Number: MCP6272
• Description: 170 ?a, 2 Mhz Rail-to-rail Op Am
• Manufacturer: Microchip Technology Inc.

4.9
4.9.1
The MCP6271/1R/2/3/4/5 family of amplifiers can be
used in applications such as an Active Full-Wave
Rectifier or an Absolute Value circuit, as shown in
Figure
active voltage rectifier circuit eliminate the diode drop
problem that exists in a passive voltage rectifier. This
circuit behaves as a follower (the output follows the
input) as long as the input signal is more positive than
the reference voltage. If the input signal is more
negative than the reference voltage, however, the
circuit behaves as an inverting amplifier. Therefore, the
output voltage will always be above the reference
voltage, regardless of the input signal.
FIGURE 4-8:
The design equations give a gain of ±1 from V
V
© 2006 Microchip Technology Inc.
V
V
OUT
V
IN
REF
REF
, and produce rail-to-rail outputs.
4-8. The amplifier and feedback loops in this
R
Application Circuits
+
–
Op Amp A
3
Input
ACTIVE FULL-WAVE RECTIFIER
MCP6272
R
R
D
1
4
2
1/2
time
D
R
1
5
Active Full-wave Rectifier.
R
R
R
V
1
4
5
V
REF
Op Amp B
<
–
+
REF
=
=
R
R
R
R
------------
3
2R
MCP6272
⎛
⎝
2
2
2
1
R
Output
=
3
4
–
1/2
R
--------------------------- -
V
3
REF
V
D1
–
V
time
V
OUT
IN
SS
⎞
⎠
to
4.9.2
The non-inverting integrator shown in
easy to build. It saves one op amp over the typical
Miller integrator plus inverting amplifier configuration.
The phase accuracy of this integrator depends on the
matching of the input and feedback resistor-capacitor
time constants. R
finite gain at DC), and makes this integrator stable by
itself.
FIGURE 4-9:
V
R
R
V
-------------
MCP6271/1R/2/3/4/5
V
IN
F
1
OUT
C
IN
≈
1
R
=
≈
2
(
------------------- -
s R
R
R
(
LOSSY NON-INVERTING
INTEGRATOR
2
1
1
||R
1
C
F
1
)
)C
F
,
makes this a lossy integrator (it has
2
f
C
≈
Non-Inverting Integrator.
1
-------------------------------------------------- -
2πR
1
R
+
_
C
MCP6271
2
1
(
1
1
R
C
C
+
F
2
2
R
DS21810E-page 15
F
⁄
R
Figure 4-9
2
)
V
OUT
is