MCP6271 Microchip Technology, MCP6271 Datasheet - Page 13

• Manufacturer Part Number: MCP6271
• Description: 170 uA, 2 MHz Rail-to-Rail Op Amp
• Manufacturer: Microchip Technology

FIGURE 4-6:
for Inverting Gain.
1.
2.
 2004 Microchip Technology Inc.
For
Amplifiers (convert current to voltage, such as
photo detectors):
a.
b.
Non-inverting Gain and Unity-Gain Buffer:
a.
b.
Connect the guard ring to the non-inverting
input pin (V
to the same reference voltage as the op
amp (e.g., V
Connect the inverting pin (V
with a wire that does not touch the PCB
surface.
Connect the non-inverting pin (V
input with a wire that does not touch the
PCB surface.
Connect the guard ring to the inverting input
pin (V
common mode input voltage.
Inverting
IN
–). This biases the guard ring to the
V
IN
IN
DD
Guard Ring
Gain
+). This biases the guard ring
Example Guard Ring Layout
–
/2 or ground).
and
V
IN
+
Transimpedance
IN
–) to the input
IN
V
SS
+) to the
4.8
4.8.1
The MCP6271/2/3/4/5 family of amplifiers can be used
in applications such as an Active Full-Wave Rectifier or
an Absolute Value circuit, as shown in Figure 4-7. 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 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 4-7:
The design equations give a gain of ±1 from V
V
V
OUT
V
V
R
REF
IN
REF
3
, and produce rail-to-rail outputs.
Application Circuits
Input
–
Op Amp A
+
MCP6271/2/3/4/5
ACTIVE FULL-WAVE RECTIFIER
time
MCP6272
R
R
D
1
4
2
1/2
R
5
Active Full-wave Rectifier.
D
1
R
R
R
V
1
4
5
REF
V
=
=
Op Amp B
–
+
REF
R
R
R
------------
3
2R


DS21810D-page 13
2
2
R
MCP6272
Output
1
R
2
3
=
4
–
1/2
--------------------------- -
V
R
time
3
REF
V
D1
–
V
V
OUT
SS
IN


to