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參數(shù)資料
| 型號(hào)： | LMH6725MTX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運(yùn)算放大器 |
| 英文描述： | 250mA ULTRA-LOW DROPOUT POSITIVE VOLTAGE REGULATOR |
| 中文描述： | QUAD OP-AMP, 3700 uV OFFSET-MAX, PDSO14 |
| 封裝： | TSSOP-14 |
| 文件頁(yè)數(shù)： | 13/17頁(yè) |
| 文件大小： | 1057K |
| 代理商： | LMH6725MTX |
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Application Section
(Continued)
DRIVING CAPACITIVE LOADS
Capacitive output loading applications will benefit from the
use of a series output resistor as shown in
Figure 5
. The
charts "Suggested R
OUT
vs. Cap Load" give a recommended
value for selecting a series output resistor for mitigating
capacitive loads. The values suggested in the charts are
selected for .5 dB or less of peaking in the frequency re-
sponse. This gives a good compromise between settling
time and bandwidth. For applications where maximum fre-
quency response is needed and some peaking is tolerable,
the value of R
OUT
can be reduced slightly from the recom-
mended values.
There will be amplitude lost in the series resistor unless the
gain is adjusted to compensate; this effect is most noticeable
with heavy loads (R
L
<
150
).
An alternative approach is to place R
inside the feedback
loop as shown in
Figure 6
. This will preserve gain accuracy,
but will still limit maximum output voltage swing.
INVERTING INPUT PARASITIC CAPACITANCE
Parasitic capacitance is any capacitance in a circuit that was
not intentionally added. It is produced through electrical
interaction between conductors and can be reduced but
never entirely eliminated. Most parasitic capacitances that
cause problems are related to board layout or lack of termi-
nation on transmission lines. Please see the section on
Layout Considerations for hints on reducing problems due to
parasitic capacitances on board traces. Transmission lines
should be terminated in their characteristic impedance at
both ends.
High speed amplifiers are sensitive to capacitance between
the inverting input and ground or power supplies. This shows
up as gain peaking at high frequency. The capacitor raises
device gain at high frequencies by making R
appear
smaller. Capacitive output loading will exaggerate this effect.
One possible remedy for this effect is to slightly increase the
value of the feedback (and gain set) resistor. This will tend to
offset the high frequency gain peaking while leaving other
parameters relatively unchanged. If the device has a capaci-
tive load as well as inverting input capacitance, using a
series output resistor as described in the section on "Driving
Capacitive Loads" will help.
When higher currents are required than a single amplifier
can provide, the circuit of
Figure 7
can be used.Although the
example circuit was intended for the LMH6725 quad op amp,
higher thermal efficiency can be obtained by using four
separate SOIC op amps. Careful attention to a few key
components will optimize performance from this circuit. The
first thing to note is that the buffers need slightly higher value
feedback resistors than if the amplifiers were individually
configured.As well, R
and C
provide mid circuit frequency
compensation to further improve stability. The composite
amplifier has approximately twice the phase delay of a single
circuit. The larger values of R
, R
and R
10
, as well as the
high frequency attenuation provided by C
1
and R
11
, ensure
that the circuit does not oscillate.
Resistors R
, R
, R
, and R
are necessary to ensure even
current distribution between the amplifiers. Since they are
inside the feedback loop they have no effect on the gain of
the circuit. The circuit shown in
Figure 7
has a gain of 5. The
frequency response of this circuit is shown in
Figure 8
.
20078934
FIGURE 5. Decoupling Capacitive Loads
20078935
FIGURE 6. Series Output Resistor inside feedback loop
20078942
FIGURE 7. High Output Current Composite Amplifier
L
www.national.com
13
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|---|---|
| LMH6725MTX/NOPB | 功能描述:IC OP AMP CFA 1MA QUAD 14-TSSOP RoHS:是 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:PowerWise® 其它有關(guān)文件:Automotive Product Guide 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- 放大器類型:通用 電路數(shù):1 輸出類型:滿擺幅 轉(zhuǎn)換速率:3 V/µs 增益帶寬積:10MHz -3db帶寬:- 電流 - 輸入偏壓:1pA 電壓 - 輸入偏移:70µV 電流 - 電源:2.5mA 電流 - 輸出 / 通道:48mA 電壓 - 電源，單路/雙路(±):2.7 V ~ 5.5 V，±1.35 V ~ 2.75 V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 供應(yīng)商設(shè)備封裝:SOT-6 包裝:Digi-Reel® 其它名稱:MAX4475AUT#TG16DKR |
| LMH6732 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Speed Op Amp with Adjustable Bandwidth |
| LMH6732J | 制造商:Texas Instruments 功能描述: |
| LMH6732MA | 功能描述:運(yùn)算放大器 - 運(yùn)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(bǔ)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 |
| LMH6732MA/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sgl 900Mhz Video 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(bǔ)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 |
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