MCP6281 Microchip Technology, MCP6281 Datasheet - Page 13

• Manufacturer Part Number: MCP6281
• Description: 450 uA, 5 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 MCP6281/2/3/4/5 op amps can be used in active-
filter applications. Figure 4-7 shows a second-order
Sallen-Key high-pass filter with a gain of 1. The output
bias voltage is set by the V
be changed to any voltage within the output voltage
range.
FIGURE 4-7:
This filter, and others, can be designed using
Microchip’s FilterLab
our web site (www.microchip.com).
4.8.2
Analog integrators are used in filters, control loops and
measurement circuits. Figure 4-8 shows the most
common implementation, the inverting Miller integrator.
The non-inverting input is at V
properly biases up. The switch (SW) is used to zero the
output in some applications. Other applications use a
feedback loop to keep the output within its linear range
of operation.
FIGURE 4-8:
V
IN
V
IN
Application Circuits
C
V
MCP6281/2/3/4/5
SALLEN-KEY HIGH-PASS FILTER
1
INVERTING MILLER INTEGRATOR
DD
R
/2
V
R
DD
C
R
1
2
/2
2
®
MCP6281
+
–
Sallen-Key High-Pass Filter.
Miller Integrator.
software, which is available on
SW
C
DD
MCP6281
+
–
DD
/2 reference, which can
/2 so that the op amp
DS21811D-page 13
V
V
OUT
IN
V
OUT
=
sRC
V
1
OUT