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參數(shù)資料
| 型號： | LMC6035ITL |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運動控制電子 |
| 英文描述： | Low Power 2.7V Single Supply CMOS Operational Amplifiers |
| 中文描述： | DUAL OP-AMP, 5000 uV OFFSET-MAX, 1.4 MHz BAND WIDTH, PBGA8 |
| 封裝： | MICRO, SMD-8 |
| 文件頁數(shù)： | 12/20頁 |
| 文件大小： | 786K |
| 代理商： | LMC6035ITL |
1.0 Application Notes
1.1 Background
The LMC6035/6 is exceptionally well suited for low voltage
applications. A desirable feature that the LMC6035/6 brings
to low voltage applications is its output drive capability—a
hallmark for National’s CMOS amplifiers. The circuit of
Fig-
ure 1
illustrates the drive capability of the LMC6035/6 at 3V
of supply. It is a differential output driver for a one-to-one
audio transformer, like those used for isolating ground from
the telephone lines. The transformer (T1) loads the op amps
with about 600
ofAC load, at 1 kHz. Capacitor C1 functions
to block DC from the low winding resistance of T1. Although
the value of C1 is relatively high, its load reactance (Xc) is
negligible compared to inductive reactance (X
I
) of T1.
The circuit in
Figure 1
consists of one input signal and two
output signals. U1A amplifies the input with an inverting gain
of 2, while the U1B amplifies the input with a non-inverting
gain of +2. Since the two outputs are 180 out of phase with
each other, the gain across the differential output is 4. As the
differential output swings between the supply rails, one of
the op amps sources the current to the load, while the other
op amp sinks the current.
How good a CMOS op amp can sink or source a current is
an important factor in determining its output swing capability.
The output stage of the LMC6035/6—like many op
amps—sources and sinks output current through two
complementary transistors in series. This “totem pole” ar-
rangement translates to a channel resistance (R
) at each
supply rail which acts to limit the output swing. Most CMOS
op amps are able to swing the outputs very close to the
rails—except, however, under the difficult conditions of low
supply voltage and heavy load. The LMC6035/6 exhibits
exceptional output swing capability under these conditions.
The scope photos of
Figure 2
and
Figure 3
represent mea-
surements taken directly at the output (relative to GND) of
U1A, in
Figure 1
.
Figure 2
illustrates the output swing capa-
bility of the LMC6035, while
Figure 3
provides a benchmark
comparison. (The benchmark op amp is another low voltage
(3V) op amp manufactured by one of our reputable competi-
tors.)
Notice the superior drive capability of LMC6035 when com-
pared with the benchmark measurement—even though the
benchmark op amp uses twice the supply current.
Not only does the LMC6035/6 provide excellent output swing
capability at low supply voltages, it also maintains high open
loop gain (A
) with heavy loads. To illustrate this, the
LMC6035 and the benchmark op amp were compared for
their distortion performance in the circuit of
Figure 1
. The
graph of
Figure 4
shows this comparison. The y-axis repre-
sents percent Total Harmonic Distortion (THD plus noise)
across the loaded secondary of T1. The x-axis represents
the input amplitude of a 1 kHz sine wave. (Note that T1 loses
about 20% of the voltage to the voltage divider of R
(600
)
and T1’s winding resistances—a performance deficiency of
the transformer.)
01283044
FIGURE 1. Differential Driver
01283045
FIGURE 2. Output Swing Performance of
the LMC6035 per the Circuit of
Figure 1
01283046
FIGURE 3. Output Swing Performance of Benchmark
Op Amp per the Circuit of
Figure 1
L
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMC6035ITL/NOPB | 功能描述:運算放大器 - 運放 2.7V Dual RRO CMOS Op amp 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 |
| LMC6035ITLNOPB | 制造商:National Semiconductor 功能描述:OP Amp Dual GP R-R O/P 15.5V 8-Pin uSMD T/R |
| LMC6035ITLX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Power 2.7V Single Supply CMOS Operational Amplifiers |
| LMC6035ITLX/NOPB | 功能描述:運算放大器 - 運放 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 |
| LMC6036 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Low Power 2.7V Single Supply CMOS Operational Amplifiers |
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