MCP6034 MICROCHIP [Microchip Technology], MCP6034 Datasheet - Page 16

• Manufacturer Part Number: MCP6034
• Description: 0.9 uA, High Precision Op Amps
• Manufacturer: MICROCHIP [Microchip Technology]

MCP6031/2/3/4
4.6
With this family of operational amplifiers, the power
supply pin (V
bypass capacitor (i.e., 0.01 µF to 0.1 µF) within 2 mm
for good high-frequency performance. It also needs a
bulk capacitor (i.e., 1 µF or larger) within 100 mm to
provide large, slow currents. This bulk capacitor can be
shared with other analog parts.
4.7
An unused op amp in a quad package (MCP6034)
should be configured as shown in
circuits prevent the output from toggling and causing
crosstalk. Circuit A can use any reference voltage
between the supplies, provides a buffered DC
voltage,and minimizes the supply current draw of the
unused op amp. Circuit B uses fewer components and
operates as a comparator; it may draw more current.
FIGURE 4-5:
4.8
In applications where low input bias current is critical,
Printed Circuit Board (PCB) surface leakage effects
need to be considered. Surface leakage is caused by
humidity, dust or other contamination on the board.
Under low humidity conditions, a typical resistance
between nearby traces is 10
cause 5 pA of current to flow; which is greater than the
MCP6031/2/3/4 family’s bias current at +25°C
(±1.0 pA, typical).
The easiest way to reduce surface leakage is to use a
guard ring around sensitive pins (or traces). The guard
ring is biased at the same voltage as the sensitive pin.
An example of this type of layout is shown in
Figure
DS22041A-page 16
V
DD
¼ MCP6034 (A)
4-6.
R
R
Supply Bypass
Unused Op Amps
PCB Surface Leakage
DD
for single-supply) should have a local
V
DD
Unused Op Amps.
12
Ω. A 5V difference would
¼ MCP6034 (B)
Figure
V
DD
4-5. These
FIGURE 4-6:
for Inverting Gain.
1.
2.
Non-inverting Gain and Unity-Gain Buffer:
a.
b.
Inverting Gain and Transimpedance Gain Ampli-
fiers (convert current to voltage, such as photo
detectors):
a.
b.
Guard Ring
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.
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.
IN
–). This biases the guard ring to the
IN
DD
+). This biases the guard ring
Example Guard Ring Layout
© 2007 Microchip Technology Inc.
/2 or ground).
V
IN
– V
IN
+
IN
–) to the input
V
SS
IN
+) to the