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參數(shù)資料
| 型號： | LM3914VX |
| 元件分類： | 顯示驅(qū)動器 |
| 英文描述： | LED Display Driver |
| 中文描述： | LED顯示驅(qū)動器 |
| 文件頁數(shù)： | 7/12頁 |
| 文件大小： | 236K |
| 代理商： | LM3914VX |
Application Hints
(Continued)
TRANSIENT INTERMODULATION DISTORTION
There has been a lot of interest in recent years about tran-
sient intermodulation distortion. Matti Otala of University of
Oulu, Oulu, Finland has published several papers on the
subject. The results of these investigations show that the
open loop pole of the power amplifier should be above 20
kHz.
To do this with the LM391 is easy. Put a 1 M
X
resistor from
pin 3 to the output and the open loop gain is reduced to
about 46 dB. Now the open loop pole is at 30 kHz. The
current in this resistor causes an offset in the input stage
that can be cancelled with a resistor from pin 4 to ground.
The resistor from pin 4 to ground should be 910 k
X
rather
than 1 M
X
to insure that the shutdown circuitry will operate
correctly. The slight difference in resistors results in about
15 mV of offset. The 40W, 8
X
amplifier schematic shows
the hookup of these two resistors.
BRIDGE AMPLIFIER
A switch can be added to convert a stereo amplifer to a
single bridge amplifer. The diagram below shows where the
switch and one resistor are added. When operating in the
bridge mode the output load is connected between the two
outputs, the input is V
IN
Y
1, and V
IN
Y
2 is disconnected.
OSCILLATIONS & GROUNDING
Most power amplifiers work the first time they are turned on.
They also tend to oscillate and have excess THD. Most os-
cillation problems are due to inadequate supply bypassing
and/or ground loops. A 10
m
F, 50V electrolytic on each
power supply will stop supply-related oscillations. However,
if the signal ground is used for these bypass caps the THD
is usually excessive. The signal ground must return to the
power supply alone, as must the output load ground. All
other groundsDbypass, output R-C, protection, etc., can tie
together and then return to supply. This ground is called
high frequency ground. On the 40W amplifier schematic all
the grounds are labeled.
Capacitive loads can cause instabilities, so they are isolated
from the amplifier with an inductor and resistor in the output
lead.
AB BIAS CURRENT
To reduce distortion in the output stage, all the transistors
are biased ON slightly. This results in class AB operation
and reduces the crossover (notch) distortion of the class B
stage to a low level, (see performance curve, THD vs AB
bias). The potentiometer, R
B
, from pins 6–7 is adjusted to
give about 25 mA of current in the output stage. This current
is usually monitored at the supply or by measuring the volt-
age across R
E
.
Typical Applications
(Continued)
Bridge Circuit Diagram
TL/H/7146–7
Output Transistors Selection Guide
Table A.
Power
Output
Driver Transistor
Output Transistor
PNP
NPN
PNP
NPN
20W
@
8
X
30W
@
4
X
MJE711
MJE171
D43C8
MJE721
MJE181
D42C8
TIP42A
2N6490
TIP41A
2N6487
40W
@
8
X
60W
@
4
X
MJE712
MJE172
D43C11
MJE722
MJE182
D42C11
2N5882
2N5880
7
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3914VX/NOPB | 功能描述:LED照明驅(qū)動器 DOT/BAR DISPLAY DRVR RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風格:SMD/SMT 封裝 / 箱體:SO-16N |
| LM3915 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Dot/Bar Display Driver |
| LM3915J/A+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Display Driver |
| LM3915N | 制造商:Texas Instruments 功能描述: 制造商:Texas Instruments 功能描述:IC LED DISPLAY DRIVER 3915 DIP18 |
| LM3915N/A+ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LED Display Driver |
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