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參數(shù)資料
| 型號： | LM246D |
| 廠商： | 意法半導(dǎo)體 |
| 元件分類： | 運動控制電子 |
| 英文描述： | PROGRAMMABLE QUAD BIPOLAR OPERATIONAL AMPLIFIERS |
| 中文描述： | 可編程四雙極運算放大器 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 423K |
| 代理商： | LM246D |
Application Hints
(Continued)
OPTIMIZING TRANSIENT RESPONSE
Referring to Figure 9 there are three components (R1, R2
and L1) that can be adjusted to optimize the transient
response of the application circuit. Increasing the values of
R1 and R2 will slow the circuit down while decreasing
overshoot. Increasing the value of L1 will speed up the circuit
as well as increase overshoot. It is very important to use
inductors
with
very
high
preferably above 300MHz. Ferrite core inductors from J.W.
Miller Magnetics (part
#
78FR--k) were used for optimizing
the performance of the device in the NSC application board.
The values shown in Figure 9can be used as a good starting
point for the evaluation of the LM2465. Using a variable
resistor for R1 will simplify finding the value needed for
optimum performance in a given application. Once the
optimum value is determined, the variable resistors can be
replaced with fixed values.
self-resonant
frequencies,
EFFECT OF LOAD CAPACITANCE
Figure 8 shows the effect of increased load capacitance on
the speed of the device. This demonstrates the importance
of knowing the load capacitance in the application. The rise
time increased about 0.12nsec for an increase of 1pF in the
load capacitance. The fall time increased about 0.10 nsec for
a 1pF increase in the load capacitance.
EFFECT OF OFFSET
Figure 7 shows the variation in rise and fall times when the
output offset of the device is varied from 40 to 50 V
DC
. The
rise time increases less than 0.20nsec from its fastest point
near 45V. The fall time becomes faster as the offset voltage
increases, but the 45V offset is only 0.1nsec slower than the
fastest fall time.
THERMAL CONSIDERATIONS
Figure 4 shows the performance of the LM2465 in the test
circuit shown in Figure 2 as a function of case temperature.
The figure shows that the rise time of the LM2465 increases
by approximately 13% as the case temperature increases
from 30C to 95C. This corresponds to a speed degradation
of 2% for every 10C rise in case temperature. The fall time
degrades around 0.3% for every 10C rise in case
temperature.
Figure 6 shows the maximum power dissipation of the
LM2465 vs. Frequency when all three channels of the device
are driving an 8pF load with a 40V
alternating one pixel
on, one pixel off signal. The graph assumes a 72% active
time (device operating at the specified frequency) which is
typical in a monitor application. The other 28% of the time
the device is assumed to be sitting at the black level (65V in
this case). This graph gives the designer the information
needed to determine the heat sink requirement for his
application. The designer should note that if the load
capacitance is increased, the AC component of the total
power dissipation will also increase.
The LM2465 case temperature must be maintained below
100C. If the maximum expected ambient temperature is
70C and the maximum power dissipation is 7.6W (from
Figure 6 75MHz bandwidth) then a maximum heat sink
thermal resistance can be calculated:
This example assumes a capacitive load of 8pF and no
resistive load.
TYPICAL APPLICATION
A typical application of the LM2465 is shown in Figure 10
and Figure 11 Used in conjunction with an LM1267 and a
LM2479/2480bias clamp, a complete video channel from
monitor input to CRT cathode can be achieved. Performance
is ideal for 1280 x 1024 resolution displays with pixel clock
frequencies up to 135 MHz. Figure 10 and Figure 11 are the
schematic for the NSC demonstration board that can be
used to evaluate the LM1267/2465 /2480 combination in a
monitor.
PC BOARD LAYOUT CONSIDERATIONS
For optimum performance, an adequate ground plane,
isolation between channels, good supply bypassing and
minimizing unwanted feedback are necessary. Also, the
length of the signal traces from the preamplifier to the
LM2465 and from the LM2465 to the CRT cathode should be
as
short
as
possible.
The
recommended:
Ott, Henry W., “Noise Reduction Techniques in Electronic
Systems”, John Wiley & Sons, New York, 1976.
“Video Amplifier Design for Computer Monitors”, National
Semiconductor Application Note 1013.
Pease,
Robert
A.,
“Troubleshooting
Butterworth-Heinemann, 1991.
Because of its high small signal bandwidth, the part may
oscillate in a monitor if feedback occurs around the video
channel through the chassis wiring. To prevent this, leads to
the video amplifier input circuit should be shielded, and input
circuit wiring should be spaced as far as possible from output
circuit wiring.
following
references
are
Analog
Circuits”,
DS200190-10
FIGURE 9. One Channel of the LM2465 with the Recommended Arc Protection Circuit
L
www.national.com
6
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| LM246N | PROGRAMMABLE QUAD BIPOLAR OPERATIONAL AMPLIFIERS |
| LM246DT | OP-AMP|QUAD|BIPOLAR|SOP|16PIN|PLASTIC |
| LM246J | Voltage-Feedback Operational Amplifier |
| LM346DT | OP-AMP|QUAD|BIPOLAR|SOP|16PIN|PLASTIC |
| LM346J | Voltage-Feedback Operational Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM246DT | 制造商:STMicroelectronics 功能描述:OP AMP QUAD GP 22V 16SOIC - Tape and Reel |
| LM246J | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM246N | 功能描述:運算放大器 - 運放 Quad Programmable 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(fēng)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 |
| LM2470 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Monolithic Triple 7.0 ns CRT Driver |
| LM2470TA | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Monolithic Triple 7.0 ns CRT Driver |
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