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參數資料
| 型號： | LMV821M7 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運算放大器 |
| 英文描述： | Low Voltage, Low Power, R-to-R Output, 5 MHz Op Amps |
| 中文描述： | OP-AMP, 3500 uV OFFSET-MAX, 5 MHz BAND WIDTH, PDSO5 |
| 封裝： | SC-70, 5 PIN |
| 文件頁數： | 12/24頁 |
| 文件大小： | 1068K |
| 代理商： | LMV821M7 |
1.3 Input Bias Current Consideration
Input bias current (I
) can develop a somewhat significant
offset voltage. This offset is primarily due to I
flowing
through the negative feedback resistor, R
. For example, if I
B
is 90nA (max room) and R
is 100 k
, then an offset of 9 mV
will be developed (V
=I
x R
).Using a compensation resis-
tor (R
), as shown in Figure 6 cancels out this affect. But the
input offset current (I
) will still contribute to an offset volt-
age in the same manner - typically 0.05 mV at room temp.
2.0 APPLICATION CIRCUITS
This section covers the following application circuits:
1. Telephone-Line Transceiver
2. “Simple” Mixer (Amplitude Modulator)
3. Dual Amplifier Active Filters (DAAFs)
a. Low-Pass Filter (LPF)
b. High-Pass Filter (HPF)
5. Tri-level Voltage Detector
2.1 Telephone-Line Transceiver
The telephone-line transceiver of Figure 7 provides a full-
duplexed connection through a PCMCIA, miniature trans-
former. The differential configuration of receiver portion
(UR), cancels reception from the transmitter portion (UT).
Note that the input signals for the differential configuration of
UR, are the transmit voltage (Vt) and Vt/2. This is because
R
is chosen to match the coupled telephone-line imped-
ance; therefore dividing Vt by two (assuming R1
>>
R
).
The differential configuration of UR has its resistors chosen
to cancel the Vt and Vt/2 inputs according to the following
equation:
Note that Cr is included for canceling out the inadequacies of
the lossy, miniature transformer. Refer to application note
AN-397 for detailed explanation.
2.2“Simple” Mixer (Amplitude Modulator)
The mixer of Figure 8 is simple and provides a unique form
of amplitude modulation. Vi is the modulation frequency
(F
), while a +3V square-wave at the gate of Q1, induces a
carrier frequency (F
). Q1 switches (toggles) U1 between in-
verting and non-inverting unity gain configurations. Offset-
ting a sine wave above ground at Vi results in the oscillo-
scope photo of Figure 9
The simple mixer can be applied to applications that utilize
the Doppler Effect to measure the velocity of an object. The
difference frequency is one of its output frequency compo-
nents. This difference frequency magnitude (/F
-F
/) is the
key factor for determining an object’s velocity per the Dop-
pler Effect. If a signal is transmitted to a moving object, the
reflected frequency will be a different frequency. This differ-
ence in transmit and receive frequency is directly propor-
tional to an object’s velocity.
DS100128-54
FIGURE 5. Pulse Response per
Figure 4
DS100128-59
FIGURE 6. Canceling the Voltage Offset Effect of Input
Bias Current
DS100128-33
FIGURE 7. Telephone-line Transceiver for a PCMCIA
Modem Card
www.national.com
12
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMV821M7/NOPB | 功能描述:運算放大器 - 運放 Low Volt Sgl Op Amp RoHS:否 制造商:STMicroelectronics 通道數量: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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV821M7NOPB | 制造商:TI 制造商全稱:Texas Instruments 功能描述:LMV821-N/LMV822-N/LMV822-N-Q1/LMV824/LMV824-N-Q1 Single/Dual/Quad Low Voltage |
| LMV821M7X | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數量: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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV821M7X/NOPB | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數量: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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMV821M7XNOPB | 制造商:TI 制造商全稱:Texas Instruments 功能描述:LMV821-N/LMV822-N/LMV822-N-Q1/LMV824/LMV824-N-Q1 Single/Dual/Quad Low Voltage |
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