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參數資料
| 型號： | ADA4000-2 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Low Cost, Precision JFET Input Operational Amplifiers |
| 中文描述： | 低成本，精密JFET輸入運算放大器 |
| 文件頁數： | 10/16頁 |
| 文件大小： | 381K |
| 代理商： | ADA4000-2 |
ADA4000-1/ADA4000-2/ADA4000-4
APPLICATIONS
OUTPUT PHASE REVERSAL AND INPUT NOISE
Phase reversal is a change of polarity in the transfer function of
the amplifier. This can occur when the voltage applied at the
input of the amplifier exceeds the maximum common-mode
voltage. Phase reversal happens when the part is configured in
the gain of 1.
Rev. 0 | Page 10 of 16
Most JFET amplifiers invert the phase of the input signal if the
input exceeds the common-mode input. Phase reversal is a
temporary behavior of the ADA4000-x family. Each part
returns to normal operation by bringing back the common-
mode voltage. The cause of this effect is saturation of the input
stage, which leads to the forward-biasing of a drain-gate diode.
In noninverting applications, a simple fix for this is to insert a
series resistor between the input signal and the noninverting
terminal of the amplifier. The value of the resistor depends on
the application, because adding a resistor adds to the total input
noise of the amplifier. The total noise density of the circuit is
(
)
S
n
n
nTOTAL
R
i
e
e
4
S
kTR
2
2
+
+
=
where:
e
n
is the input voltage noise density of the part.
i
n
is the input current noise density of the part.
R
S
is the source resistance at the noninverting terminal.
k
is Boltzmann’s constant (1.38 × 10
23
J/K).
T
is the ambient temperature in Kelvin (T = 273 + °C).
In general, it is good practice to limit the input current to less
than 5 mA to avoid driving a great deal of current into the
amplifier inputs.
CAPACITIVE LOAD DRIVE
The ADA4000-1/ADA4000-2/ADA4000-4 are stable at all gains
in both inverting and noninverting configurations. The parts
are capable of driving up to 1000 pF of capacitive loads without
oscillations in unity gain configurations.
However, as with most amplifiers, driving larger capacitive loads
in a unity gain configuration can cause excessive overshoot and
ringing. A simple solution to this problem is to use a snubber
network (see Figure 30).
ADA4000-1
V+
V–
+15V
–15V
R
S
C
S
C
L
500pF
R
L
10k
0
SNUBBER NETWORK
400mV p-p
0
0
V1
3
2
1
U1
Figure 30. Snubber Network Configuration
The advantage of this compensation method is that the swing at
the output is not reduced because R
S
is out of the feedback
network, and the gain accuracy does not change. Depending on
the capacitive loading of the circuit, the values of R
S
and C
S
change, and the optimum value can be determined empirically.
In Figure 31, the oscilloscope image shows the output of the
ADA4000-x family in response to a 400 mV pulse. The circuit is
configured in the unity gain configuration with 500 pF in
parallel with 10 kΩ of load capacitive.
0
TIME (1μs/DIV)
V
INPUT SIGNAL
OUTPUT SIGNAL
Figure 31. Capacitive Load Drive Without Snubber Network
When the snubber circuit is used, the overshoot is reduced from
30% to 6% with the same load capacitance. Ringing is virtually
eliminated, as shown in Figure 32. In this circuit, R
S
is 41 Ω and
C
S
is 10 nF.
0
TIME (1μs/DIV)
V
INPUT SIGNAL
OUTPUT SIGNAL
Figure 32. Capacitive Load with Snubber Network
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ADA4000-2ARMZ | 功能描述:IC OPAMP JFET 5MHZ DUAL LP 8MSOP RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:50 系列:LinCMOS™ 放大器類型:通用 電路數:4 輸出類型:- 轉換速率:0.05 V/µs 增益帶寬積:110kHz -3db帶寬:- 電流 - 輸入偏壓:0.7pA 電壓 - 輸入偏移:210µV 電流 - 電源:57µA 電流 - 輸出 / 通道:30mA 電壓 - 電源，單路/雙路(±):3 V ~ 16 V，±1.5 V ~ 8 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應商設備封裝:14-SOIC 包裝:管件 產品目錄頁面:865 (CN2011-ZH PDF) 其它名稱:296-1834296-1834-5 |
| ADA4000-2ARMZ1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Cost, Precision JFET Input Operational Amplifiers |
| ADA4000-2ARMZ-R2 | 制造商:Analog Devices 功能描述:OP Amp Dual GP ±18V 8-Pin MSOP T/R |
| ADA4000-2ARMZ-RL | 功能描述:IC OPAMP JFET 5MHZ DUAL LP 8MSOP RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標準包裝:1,000 系列:- 放大器類型:電壓反饋 電路數:4 輸出類型:滿擺幅 轉換速率:33 V/µs 增益帶寬積:20MHz -3db帶寬:30MHz 電流 - 輸入偏壓:2nA 電壓 - 輸入偏移:3000µV 電流 - 電源:2.5mA 電流 - 輸出 / 通道:30mA 電壓 - 電源，單路/雙路(±):4.5 V ~ 16.5 V，±2.25 V ~ 8.25 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應商設備封裝:14-SOIC 包裝:帶卷 (TR) |
| ADA4000-2ARMZ-RL1 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Cost, Precision JFET Input Operational Amplifiers |
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