Datasheet

 2001-2017 Microchip Technology Inc. DS20001685E-page 17
MCP6021/1R/2/3/4
4.0 APPLICATIONS INFORMATION
The MCP6021/1R/2/3/4 family of operational amplifiers
is fabricated on Microchip’s state-of-the-art CMOS
process. The amplifiers are unity-gain stable and suitable
for a wide range of general purpose applications.
4.1 Rail-to-Rail Input
4.1.1 PHASE REVERSAL
The MCP6021/1R/2/3/4 operational amplifiers are
designed to prevent phase reversal when the input pins
exceed the supply voltages. Figure 2-42 shows the
input voltage exceeding the supply voltage without any
phase reversal.
4.1.2 INPUT VOLTAGE LIMITS
In order to prevent damage and/or improper operation
of these amplifiers, the circuit must limit the voltages at
the input pins. See the Absolute Maximum Ratings†
section.
The ESD protection on the inputs can be depicted as
shown in Figure 4-1. This structure was chosen to
protect the input transistors and to minimize Input Bias
(I
B
) current.
FIGURE 4-1: Simplified Analog Input ESD
Structures.
The input ESD diodes clamp the inputs when they try
to go more than one diode drop below V
SS
. They also
clamp any voltages that go well above V
DD
. Their
breakdown voltage is high enough to allow normal
operation, but not low enough to protect against slow
overvoltage (beyond V
DD
) events. Very fast ESD
events (that meet the specifications) are limited so that
damage does not occur. In some applications, it may
be necessary to prevent excessive voltages from
reaching the operational amplifier inputs. Figure 4-2
shows one approach to protecting these inputs.
A significant amount of current can flow out of the
inputs when the Common-Mode Voltage (V
CM
) is below
ground (V
SS
). See Figure 2-42.
FIGURE 4-2: Protecting the Analog Inputs.
4.1.3 INPUT CURRENT LIMITS
In order to prevent damage and/or improper operation
of these amplifiers, the circuit must limit the voltages at
the input pins. See the Absolute Maximum Ratings†
section. Figure 4-3 shows one approach to protecting
these inputs. The resistors, R
1
and R
2
, limit the pos-
sible currents in or out of the input pins (and the ESD
diodes, D
1
and D
2
). The diode currents will go through
either V
DD
or V
SS
.
FIGURE 4-3: Protecting the Analog Inputs.
4.1.4 NORMAL OPERATION
The input stage of the MCP6021/1R/2/3/4 operational
amplifiers uses two differential CMOS input stages in
parallel. One operates at a low Common-Mode Voltage
(V
CM
) input, while the other operates at high V
CM
. With
this topology, the device operates with V
CM
up to 0.3V
above V
DD
and 0.3V below V
SS
.
4.2 Rail-to-Rail Output
The maximum output voltage swing is the maximum
swing possible under a particular output load. According
to the specification table, the output can reach within
20 mV of either supply rail when R
L
= 10 k. See
Figure 2-31 and Figure 2-34 for more information
concerning typical performance.
Bond
Pad
V
IN

Bond
Pad
Bond
Pad
Bond
Pad
Input
Stage
V
DD
V
IN
+
V
SS
V
1
V
DD
D
1
V
2
D
2
MCP602X
V
OUT
U
1
V
1
R
1
V
DD
D
1
min(R
1
,R
2
)>
V
SS
–min (V
1
,V
2
)
2mA
min(R
1
,R
2
)>
max(V
1
,V
2
)–V
DD
2mA
V
2
R
2
D
2
MCP602X
V
OUT
U
1