Datasheet

MCP6H91/2/4
DS25138B-page 20  2012 Microchip Technology Inc.
4.7.2 ACTIVE FULL-WAVE RECTIFIER
The MCP6H91/2/4 family of amplifiers can be used in
applications such as an active full-wave rectifier, as
shown in Figure 4-9. The amplifier and feedback loops
in this active voltage rectifier circuit eliminate the diode
drop problem that exists in a passive voltage rectifier.
This circuit behaves as a voltage 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 with a
Gain = -1V/V. Therefore, the output voltage will always
be above the reference voltage, regardless of the input
signal. The reference voltage (V
REF
) is supplied by a
low-impedance source. In single-supply applications,
V
REF
is typically V
DD
/2.
FIGURE 4-9: Active Full-Wave Rectifier.
4.7.3 LOSSY NON-INVERTING
INTEGRATOR
The non-inverting integrator shown in Figure 4-10 is
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
F
makes this a lossy integrator (it has
finite gain at DC), and makes this integrator stable by
itself. To ensure proper operation, the op amp Common
mode input voltage must be kept within the allowed
range.
FIGURE 4-10: Non-Inverting Integrator.
–
+
–
+
V
IN
V
OUT
V
REF
V
REF
R
R
R
R/2
R
Op Amp A
Op Amp B
D
1
D
2
V
REF
V
REF
time time
Input
Output
1/2
MCP6H92
1/2
MCP6H92
+
_
C
1
C
2
R
1
R
2
V
IN
V
OUT
R
F
V
OUT
V
IN
-------------
1
sR
1
C
1

-------------------- f
1
2
 R
1
C
1
1
R
F
R
2
------+


-------------------------------------------

MCP6H91
R
F
R
2

R
1
C
1
R
2
||R
F
C
2
=
C
2