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MCP607T-I/ST 开发手册 - Microchip（微芯）
制造商:
Microchip（微芯）
分类:
运算放大器
封装:
TSSOP-8
描述:
MCP607系列 6V 155kHz 微功耗 CMOS 运算放大器-TSSOP-8
Pictures:
3D模型
符号图
焊盘图
引脚图
产品图
页面导航:
技术参数、封装参数在P8
应用领域在P8
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MCP607T-I/ST数据手册
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of 10 Go
若手册格式错乱，请下载阅览PDF原文件
AN682
DS00682C-page 4 2000 Microchip Technology Inc.
The transfer function for this amplifier circuit is:
This circuit configuration will reliably take the difference
of two signals as long as the signal source impedances
are low. If the signal source impedances are high with
respect to R
1
, there will be a signal loss due to the volt-
age divider action between the source and the input
resistors to the difference amplifier. Additionally, errors
can occur if the two signal source impedances are mis-
matched. With this circuit it is possible to have gains
equal to or higher than one.
Summing Amplifier
Summing amplifiers are used when multiple signals
need to be combined by addition or subtraction. Since
the difference amplifier can only process two signals, it
is a subset of the summing amplifier.
Figure 7: Operational amplifier configured in a
sum- ming amplifier circuit.
The transfer function of this circuit is:
Any number of inputs can be used on either the invert-
ing or non-inverting input sides as long as there are an
equal number of both with equivalent resistors.
Current to Voltage Conversion
An operational amplifier can be used to easily convert
the signal from a sensor that produces an output cur-
rent, such as a photodetector, into a voltage. This is
implemented with a single resistor and an optional
capacitor in the feedback loop of the amplifier as shown
in Figure 8.
Figure 8: Current to voltage converter using an
amplifier and one resistor. The top light scanning
circuit is appropriate for precision applications. The
bottom circuit is appropriate for high speed
applications.
As light impinges on the photo diode, charge is gener-
ated, causing a current to flow in the reverse bias direc-
tion of the photodetector. If a CMOS op amp is used,
the high input impedance of the op amp causes the cur-
rent from the detector (I
D1) to go through the path of
lower resistance, R
2
. Additionally, the op amp input
bias current error is low because it is CMOS (typically
<200 pA). The non-inverting input of the op amp is ref-
erenced to ground which keeps the entire circuit biased
to ground. These two circuits will only work if the com-
mon mode range of the amplifier includes zero.
Two circuits are shown in Figure 8. The top circuit is
designed to provide precision sensing from the photo-
detector. In this circuit the voltage across the detector
is nearly zero and equal to the offset voltage of the
amplifier. With this configuration, current that appears
across the resistor, R
2
, is primarily a result of the light
excitation on the photodetector.
The photosensing circuit on the bottom of Figure 8 is
designed for higher speed sensing. This is done by
reverse biasing the photodetector, which reduces the
parasitic capacitance of the diode. There is more leak-
age through the diode which causes a higher DC error.
V
OUT
V
1
V
2
–()
R
2
R
1
--------
V
REF
R
2
R
1
--------
+=
R
2
V
OUT
R
2
*Bypass Capacitor, 1µF
V
3
V
4
R
1
R
1
V
1
V
2
MCP601
*
V
OUT
V
1
V
2
V
3
– V–
4
+()=
R
2
R
1
------
R
1
R
1
V
DD
V
OUT
V
1
V
2
V
3
– V–
4
+()=
R
2
R
1
------
V
BIAS
R
2
C
2
R
2
V
OUT
V
OUT
= R
2
I
D1
*Bypass Capacitor, 1µF
D
1
V
OUT
Light
D
1
Light
*
MCP601
*
MCP601
I
D1
I
D1
V
DD
V
DD
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