参数资料
| 型号： | AD8428ARZ |
| 厂商： | Analog Devices Inc |
| 文件页数： | 8/20页 |
| 文件大小： | 0K |
| 描述： | IC AMP INSTRUMENTATON 8SOIC |
| 标准包装： | 1 |
| 放大器类型： | 仪表 |
| 电路数： | 1 |
| 转换速率： | 50 V/µs |
| -3db带宽： | 3.5MHz |
| 电流 - 输入偏压： | 200nA |
| 电压 - 输入偏移： | 100µV |
| 电流 - 电源： | 6.5mA |
| 电流 - 输出 / 通道： | 30mA |
| 电压 - 电源，单路/双路(±)： | ±4 V ~ 18 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SO |
| 包装： | 管件 |
AD8428
Data Sheet
Rev. A | Page 16 of 20
RADIO FREQUENCY INTERFERENCE (RFI)
Because of its high gain and low noise properties, the AD8428
is a highly sensitive amplifier. Therefore, RF rectification can be
a problem if the AD8428 is used in applications that have strong
RF signal sources present. The problem is intensified if long leads
or PCB traces are required to connect the amplifier to the signal
source. The disturbance can appear as a dc offset voltage or as a
train of pulses.
High frequency signals can be filtered with a low-pass filter
network at the input of the instrumentation amplifier, as shown
in Figure 44.
R
AD8428
+VS
+IN
–IN
0.1F
10F
0.1F
REF
OUT
–VS
CD
10nF
CC
1nF
CC
1nF
33
0
97
31-
049
L*
*CHIP FERRITE BEAD.
Figure 44. RFI Suppression
The filter limits both the differential and common-mode band-
width, as shown in the following equations:
)
2
(
π
2
1
C
D
DIFF
C
R
uency
FilterFreq
+
=
C
CM
RC
uency
FilterFreq
π
2
1
=
where CD ≥ 10 CC.
CD affects the differential signal, and CC affects the common-
mode signal. Choose values of R and CC that minimize RFI. A
mismatch between R × CC at the positive input and R × CC at
the negative input degrades the CMRR of the AD8428. By using
a value of CD one order of magnitude larger than CC, the effect
of the mismatch is reduced, and performance is improved.
Resistors add noise; therefore, the choice of resistor and capac-
itor values depends on the desired trade-off between noise, input
impedance at high frequencies, and RFI immunity. To achieve
low noise and sufficient RFI filtering, the use of inductive ferrite
beads is recommended (see Figure 44). Using inductive ferrite
beads allows the value of the resistors to be reduced, which helps
to minimize the noise at the input.
For best results, place the RFI filter network as close to the
amplifier as possible. Layout is critical to ensure that RF signals
are not picked up on the traces after the filter. If RF interference
is too strong to be filtered, shielding is recommended.
Note that the resistors used for the RFI filter can be the same
as those used for input protection (see the Input Protection
section).
CALCULATING THE NOISE OF THE INPUT STAGE
The total noise of the amplifier front end depends on much
more than the specifications in this data sheet. The three main
contributors to noise are as follows:
Source resistance
Voltage noise of the instrumentation amplifier
Current noise of the instrumentation amplifier
In the following calculations, noise is referred to the input (RTI);
that is, all sources of noise are calculated as if the source appeared
at the amplifier input. To calculate the noise referred to the ampli-
fier output (RTO), multiply the RTI noise by the gain of the
instrumentation amplifier.
Source Resistance Noise
Any sensor connected to the AD8428 has some output resistance.
There may also be resistance placed in series with the inputs for
protection from either overvoltage or radio frequency interference.
This combined resistance is labeled R1 and R2 in Figure 45. Any
resistor, no matter how well made, has an intrinsic level of noise.
This noise is proportional to the square root of the resistor value.
At room temperature, the value is approximately equal to
4 nV/√Hz × √(resistor value in kΩ).
R2
R1
SENSOR
AD8428
09
73
1-
0
5
0
Figure 45. Source Resistance from Sensor and Protection Resistors
For example, assuming that the combined sensor and protec-
tion resistance is 4 kΩ on the positive input and 1 kΩ on the
negative input, the total noise from the input resistance is
(
) (
)
Hz
nV/
9
.
8
16
64
1
4
2
=
+
=
×
+
×
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相关代理商/技术参数 |
参数描述 |
|---|---|
| AD8428ARZ_PROMO | 制造商:Analog Devices 功能描述:IC AMP INSTR LOW NOISE SOI |
| AD8428ARZ-RL | 功能描述:IC AMP INSTRUMENTATON 8SOIC RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:2,500 系列:Excalibur™ 放大器类型:J-FET 电路数:1 输出类型:- 转换速率:45 V/µs 增益带宽积:10MHz -3db带宽:- 电流 - 输入偏压:20pA 电压 - 输入偏移:490µV 电流 - 电源:1.7mA 电流 - 输出 / 通道:48mA 电压 - 电源，单路/双路(±):4.5 V ~ 38 V，±2.25 V ~ 19 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:带卷 (TR) |
| AD8428BRZ | 功能描述:IC OPAMP INST 3.5MHZ LN 8SOIC RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:2,500 系列:Excalibur™ 放大器类型:J-FET 电路数:1 输出类型:- 转换速率:45 V/µs 增益带宽积:10MHz -3db带宽:- 电流 - 输入偏压:20pA 电压 - 输入偏移:490µV 电流 - 电源:1.7mA 电流 - 输出 / 通道:48mA 电压 - 电源，单路/双路(±):4.5 V ~ 38 V，±2.25 V ~ 19 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:带卷 (TR) |
| AD8428BRZ_PROMO | 制造商:Analog Devices 功能描述:INST AMP 3.5MHZ 2K V/V 0.2 |
| AD8428BRZ-RL | 功能描述:IC OPAMP INST 3.5MHZ LN 8SOIC RoHS:是 类别:集成电路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 标准包装:2,500 系列:Excalibur™ 放大器类型:J-FET 电路数:1 输出类型:- 转换速率:45 V/µs 增益带宽积:10MHz -3db带宽:- 电流 - 输入偏压:20pA 电压 - 输入偏移:490µV 电流 - 电源:1.7mA 电流 - 输出 / 通道:48mA 电压 - 电源，单路/双路(±):4.5 V ~ 38 V，±2.25 V ~ 19 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 供应商设备封装:8-SOIC 包装:带卷 (TR) |
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