參數(shù)資料
型號： MCP6231_05
廠商： Microchip Technology Inc.
英文描述： 20 レA, 300 kHz Rail-to-Rail Op Amp
中文描述： 20レ甲，300千赫軌至軌運算放大器
文件頁數(shù)： 10/28頁
文件大小： 384K
代理商： MCP6231_05
MCP6231/2/4
DS21881C-page 10
2005 Microchip Technology Inc.
4.7
Application Circuits
4.7.1
MATCHING THE IMPEDANCE AT
THE INPUTS
To minimize the effect of input bias current in an ampli-
fier circuit (this is important for very high source-
impedance applications, such as pH meters and
transimpedance amplifiers), the impedances at the
inverting and non-inverting inputs need to be
matched. This is done by choosing the circuit resistor
values so that the total resistance at each input is the
same. Figure 4-7 shows a summing amplifier circuit.
FIGURE 4-7:
To match the inputs, set all voltage sources to ground
and calculate the total resistance at the input nodes. In
this summing amplifier circuit, the resistance at the
inverting input is calculated by setting V
IN1
, V
IN2
and
V
OUT
to ground. In this case, R
G1
, R
G2
and R
F
are in
parallel. The total resistance at the inverting input is:
Summing Amplifier Circuit.
At the non-inverting input, V
DD
is the only voltage
source. When V
DD
is set to ground, both R
x
and R
y
are
in parallel. The total resistance at the non-inverting
input is:
To minimize output offset voltage and increase circuit
accuracy, the resistor values need to meet the
conditions:
4.7.2
COMPENSATING FOR THE
PARASITIC CAPACITANCE
In analog circuit design, the PCB parasitic capacitance
can compromise the circuit behavior; Figure 4-8 shows
a typical scenario. If the input of an amplifier sees
parasitic capacitance of several picofarad (C
PARA
,
which includes the common mode capacitance of 6 pF,
typ.), and large R
F
and R
G
, the frequency response of
the circuit will include a zero. This parasitic zero
introduces gain-peaking and can cause circuit
instability.
FIGURE 4-8:
Capacitance at the Input.
Effect of Parasitic
One solution is to use smaller resistor values to push
the zero to a higher frequency. Another solution is to
compensate by introducing a pole at the point at which
the zero occurs. This can be done by adding C
F
in
parallel with the feedback resistor (R
F
). C
F
needs to be
selected so that the ratio C
PARA
:C
F
is equal to the ratio
of R
F
:R
G
.
MCP623X
+
V
OUT
V
IN2
–
V
IN1
R
G2
R
G1
R
F
R
Z
V
DD
R
X
R
Y
R
IN
–
R
G1
---------
R
G2
---------
R
F
------
+
+
---------------------------------------------
=
Where:
R
VIN–
= total resistance at the inverting input
R
VIN+
R
X
------
1
R
Y
-----
+
------------------------
R
Z
+
=
Where:
R
VIN+
= total resistance at the inverting
input
R
VIN+
R
IN
–
=
V
OUT
C
F
V
DC
+
–
V
AC
R
G
R
F
C
PARA
C
F
C
PARA
R
G
R
F
------
=
MCP623X
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MCP6231-E/MC 功能描述:運算放大器 - 運放 SNGL 18V 300 kHz OP E Temp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
MCP6231-E/MS 功能描述:運算放大器 - 運放 Single 1.8V 200KHz RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
MCP6231-E/P 功能描述:運算放大器 - 運放 Single 1.8V 200KHz RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
MCP6231-E/SN 功能描述:運算放大器 - 運放 Single 1.8V 200KHz RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
MCP6231RT-E/OT 功能描述:運算放大器 - 運放 Single 1.8V 200KHz RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel
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