参数资料
| 型号： | AD8220WARMZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 15/28页 |
| 文件大小： | 0K |
| 描述： | IC AMP INST JFET R-R 15MA 8MSOP |
| 标准包装： | 50 |
| 放大器类型： | 仪表 |
| 电路数： | 1 |
| 输出类型： | 满摆幅 |
| 转换速率： | 2 V/µs |
| -3db带宽： | 1.5MHz |
| 电流 - 输入偏压： | 25pA |
| 电压 - 输入偏移： | 250µV |
| 电流 - 电源： | 750µA |
| 电流 - 输出 / 通道： | 15mA |
| 电压 - 电源，单路/双路(±)： | 4.5 V ~ 36 V，±2.25 V ~ 18 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 8-MSOP |
| 包装： | 管件 |
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AD8220
Rev. B | Page 22 of 28
RF INTERFERENCE
RF rectification is often a problem in applications where there are
large RF signals. The problem appears as a small dc offset voltage.
The AD8220 by its nature has a 5 pF gate capacitance, CG, at its
inputs. Matched series resistors form a natural low-pass filter that
reduces rectification at high frequency (see Figure 61). The
relationship between external, matched series resistors and the
internal gate capacitance is expressed as follows:
G
DIFF
RC
FilterFreq
π
2
1
G
CM
RC
FilterFreq
π
2
1
AD8220
VOUT
CG
–VS
REF
–VS
R
+IN
–IN
+15V
–15V
0.1F
10F
0.1F
10F
03
57
9-
0
30
Figure 61. RFI Filtering Without External Capacitors
To eliminate high frequency common-mode signals while using
smaller source resistors, a low-pass RC network can be placed at
the input of the instrumentation amplifier (see Figure 62). The
filter limits the input signal bandwidth according to the following
relationship:
)
2
(
π
2
1
G
C
D
DIFF
C
R
FilterFreq
)
(
π
2
1
G
C
CM
C
R
FilterFreq
Mismatched CC capacitors result in mismatched low-pass filters.
The imbalance causes the AD8220 to treat what would have
been a common-mode signal as a differential signal. To reduce
the effect of mismatched external CC capacitors, select a value of
CD greater than 10 times CC. This sets the differential filter
frequency lower than the common-mode frequency.
R
AD8220
+15V
+IN
–IN
0.1F
10F
0.1F
REF
VOUT
–15V
CD
CC
10nF
1nF
4.02k
03
57
9-
00
3
Figure 62. RFI Suppression
COMMON-MODE INPUT VOLTAGE RANGE
The common-mode input voltage range is a function of the
input range and the outputs of Internal Amplifier A1, Internal
Amplifier A2, and Internal Amplifier A3, the reference voltage,
and the gain. Figure 27 to Figure 30 show common-mode
voltage ranges for various supply voltages and gains.
DRIVING AN ADC
An instrumentation amplifier is often used in front of an ADC
to provide CMRR and additional conditioning, such as a voltage
level shift and gain (see Figure 63). In this example, a 2.7 nF
capacitor and a 1 kΩ resistor create an antialiasing filter for the
AD7685. The 2.7 nF capacitor also serves to store and deliver
the necessary charge to the switched capacitor input of the
ADC. The 1 kΩ series resistor reduces the burden of the 2.7 nF
load from the amplifier. However, large source impedance in
front of the ADC can degrade THD.
The example shown in Figure 63 is for sub-60 kHz applications.
For higher bandwidth applications where THD is important,
the series resistor needs to be small. At worst, a small series
resistor can load the AD8220, potentially causing the output to
overshoot or ring. In such cases, a buffer amplifier, such as the
AD8615, should be used after the AD8220 to drive the ADC.
AD8220
AD7685
4.7F
ADR435
+5V
2.7nF
REF
1k
1.07k
+2.5V
+IN
–IN
±50mV
+5V
0.1F
10F
0
357
9-
0
33
Figure 63. Driving an ADC in a Low Frequency Application
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| AD8220WARMZ-R7 | 功能描述:IC AMP INST JFET R-R 15MA 8MSOP RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:1 系列:- 放大器类型:通用 电路数:4 输出类型:满摆幅 转换速率:0.028 V/µs 增益带宽积:105kHz -3db带宽:- 电流 - 输入偏压:3nA 电压 - 输入偏移:100µV 电流 - 电源:3.3µA 电流 - 输出 / 通道:12mA 电压 - 电源，单路/双路(±):2.7 V ~ 12 V，±1.35 V ~ 6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:14-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:14-TSSOP 包装:剪切带 (CT) 其它名称:OP481GRUZ-REELCT |
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