MCP6004 MICROCHIP [Microchip Technology], MCP6004 Datasheet - Page 8

• Manufacturer Part Number: MCP6004
• Description: 1 MHz Bandwidth Low Power Op Amp
• Manufacturer: MICROCHIP [Microchip Technology]

MCP6001/2/4
3.4
With this family of operation amplifiers, the power sup-
ply 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 parts.
3.5
In applications where low input bias current is critical,
PCB (printed circuit board) 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, if current-to-flow; this is greater than the
MCP6001/2/4 family’s bias current at 25°C (1 pA, typ).
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 3-4.
FIGURE 3-4:
for Inverting Gain.
1.
2.
DS21733D-page 8
Non-inverting Gain and Unity Gain Buffer:
a.
b.
Inverting and Transimpedance Gain Amplifiers
(convert current to voltage, such as photo detec-
tors):
a.
b.
Supply Bypass
PCB Surface Leakage
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.
DD
for single supply) should have a local
IN
–). This biases the guard ring to the
V
IN
IN
Guard Ring
DD
+). This biases the guard ring
Example Guard Ring Layout
-
/2 or ground).
12
. A 5V difference would
V
IN
+
IN
–) to the input
IN
V
+) to the
SS
3.6
3.6.1
The rail-to-rail input and output capability of the
MCP6001/2/4 op amp is ideal for unity-gain buffer
applications. The low quiescent current and wide band-
width makes the device suitable for a buffer configura-
tion in an instrumentation amplifier circuit, as shown in
Figure 3-5.
FIGURE 3-5:
with Unity Gain Buffer Inputs.
3.6.2
The MCP6001/2/4 op amp’s low input bias current
makes it possible for the designer to use larger resis-
tors and smaller capacitors for active low-pass filter
applications. However, as the resistance increases, the
noise generated also increases. Parasitic capacitances
and the large value resistors could also modify the fre-
quency response. These trade-offs need to be
considered when selecting circuit elements.
It is possible to have a filter cutoff frequency as high as
1/10th of the op amp bandwidth (100 kHz). Figure 3-6
shows a second-order butterworth filter with 100 kHz
cutoff frequency and a gain of +1V/V.
The
Microchip’s FilterLab
FIGURE 3-6:
Pass Filter.
V
V
V
IN2
IN1
IN
component
14.3 k
Application Circuits
V
OUT
UNITY GAIN BUFFER
ACTIVE LOW-PASS FILTER
MCP6002
MCP6002
+
+
-
-
1/2
1/2
53.6 k
33 pF
=
V
values
®
IN2
software.
Instrumentation Amplifier
Active Second-Order Low-
–
100 pF
2003 Microchip Technology Inc.
V
R
R
2
IN1
2
were
MCP6002
R
+
+
V
-
-
MCP6001
1
R
----- -
R
REF
1
2
R
+
1
selected
V
REF
R
R
1
2
= 20 k
= 10 k
V
V
OUT
OUT
using