MCP601-I-SN N/A, MCP601-I-SN Datasheet - Page 15

• Manufacturer Part Number: MCP601-I-SN
• Description: 2.7V to 5.5V Single Supply CMOS Op Amps
• Manufacturer: N/A

An advantage of the three op amp configuration is that
it is capable of unity gain operation. A disadvantage, as
compared to the two op amp instrumentation amplifier,
is that the common mode range reduces with higher
gains.
The two op amp configuration uses fewer op amps, so
power consumption is also low. Disadvantages of this
configuration are that the common-mode range
reduces with gain and it must be configured in gains of
two or higher.
3.6.3
The amplifiers in the MCP601/602/603/604 family of
devices can be used to easily convert the signal from a
sensor that produces an output current, such as a pho-
todiode, into a voltage. This is implemented with a sin-
gle resistor and an optional capacitor in the feedback
loop of the amplifier as shown in Figure 3-14.
FIGURE 3-14: Photo Sensing Circuits Using the
MCP60X Amplifier
A photodiode that is configured in the photovoltaic
mode has no voltage potential placed across the ele-
ment or is zero biased (Figure 3-14). In this mode, the
light sensitivity and linearity is maximized making it
best suited for precision applications. The key amplifier
specifications for this application are low input bias cur-
rent, low noise and rail-to-tail output swing. The
MCP601/602/603/604 family is capable of meeting all
three of these difficult requirements.
 2000 Microchip Technology Inc.
Photodiode in Photoconductive Mode
Photodiode in Photovoltaic Mode
Light
Light
PHOTO DETECTION
D
V
BIAS
1
D
1
I
D1
I
D1
V
OUT
MCP60X
MCP60X
= R
C
R
2
2
2
R
I
D1
2
V
OUT
V
OUT
In contrast, a photodiode that is configured in the pho-
toconductive mode has a reverse bias voltage, which is
applied across the photo sensing element as shown in
Figure 3-14. The width of the depletion region is
reduced when this voltage is applied across the photo
detector, which reduces the photodiode parasitic
capacitance significantly. This reduced parasitic capac-
itance facilitates high speed operation, however, the lin-
earity and offset errors are not optimized. The design
trade off for this action is increased diode leakage cur-
rent and linearity errors. A key amplifier specification for
this application is high speed digital communication.
The MCP601/602/603/604 family is well suited for
medium speed photoconductive applications with their
wide bandwidth and rail-to-rail output swing.
MCP601/602/603/604
DS21314D-page 15