MCP602

Manufacturer Part NumberMCP602
DescriptionMCP601-2-3-4
ManufacturerN/A
MCP602 datasheet
 


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MCP601/2/3/4
1k
1,000
100
100
G
= +1
N
G
+2
N
10
10
10
100
1,000
10p
100p
1n
Normalized Load Capacitance; C
FIGURE 3-3:
Recommended R
for capacitive loads.
After selecting R
for your circuit, double-check the
ISO
resulting frequency response peaking and step
response overshoot in your circuit. Evaluation on the
bench and simulations with the MCP601/2/3/4 SPICE
macro model are very helpful. Modify R
the response is reasonable.
3.5
Supply Bypass
With this family of operational amplifiers, the power
supply pin (V
for single supply) should have a local
DD
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.
3.6
PCB Surface Leakage
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
12
between nearby traces is 10
. A 5V difference would
cause 5 pA of current to flow. This is greater than the
MCP601/2/3/4 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.
Guard Ring
V
V
IN–
IN+
FIGURE 3-4:
Example guard ring layout.
DS21314E-page 12
1.
Connect the guard ring to the inverting input pin
(V
) for non-inverting gain amplifiers, including
IN–
unity-gain buffers. This biases the guard ring to
the common mode input voltage.
2.
Connect the guard ring to the non-inverting input
pin (V
IN+
transimpedance amplifiers (convert current to
voltage, such as photo detectors). This biases
the guard ring to the same reference voltage as
the op amp (e.g., V
10,000
10n
3.7
Typical Applications
/ G
(F)
L
N
3.7.1
ANALOG FILTERS
values
ISO
Figure 3-5 and Figure 3-6 show low-pass, second-
order, Butterworth filters with a cutoff frequency of
10 Hz. The filter in Figure 3-5 has a non-inverting gain
of +1 V/V, and the filter in Figure 3-6 has an inverting
gain of -1 V/V.
’s value until
ISO
R
1
382 k
V
IN
FIGURE 3-5:
Key filter.
R
1
618 k
V
IN
C
2
47 nF
FIGURE 3-6:
Feedback filter.
The MCP601/2/3/4 family of operational amplifiers
have low input bias current, which allows the designer
to select larger resistor values and smaller capacitor
values for these filters. This helps produce a compact
PCB layout. These filters, and others, can be designed
using Microchip’s FilterLab
) for inverting gain amplifiers and
/2 or ground).
DD
G = +1 V/V
C
1
f
= 10 Hz
47 nF
P
R
2
641 k
C
V
MCP60X
2
OUT
22 nF
nd
2
order, low-pass Sallen-
G = -1 V/V
R
2
f
= 10 Hz
618 k
P
R
C
3
1
1.00 M
8.2 nF
V
OUT
MCP60X
V
/2
DD
nd
2
order, low-pass Multiple-
®
software.
2003 Microchip Technology Inc.