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參數(shù)資料
| 型號： | LMH6720MFX |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | Wideband Video Op Amp; Single, Single with Shutdown and Quad |
| 中文描述： | 1 CHANNEL, VIDEO AMPLIFIER, PDSO6 |
| 封裝： | SOT-23, 6 PIN |
| 文件頁數(shù)： | 10/15頁 |
| 文件大?。?/td> | 597K |
| 代理商： | LMH6720MFX |
Application Section
(Continued)
to be avoided. See Application Notes OA-7 and OA-26 for
more information on Active Filter applications for Current
Feedback Op Amps.
ENABLE/DISABLE OPERATION USING
±
5V SUPPLIES
(LMH6720 ONLY)
The LMH6720 has a TTL logic compatible disable function.
Apply a logic low (
<
.8V) to the DS pin and the LMH6720 is
disabled. Apply a logic high (
>
2.0V), or let the pin float and
the LMH6720 is enabled. Voltage, not current, at the Disable
pin determines the enable/disable state. Care must be exer-
cised to prevent the disable pin voltage from going more
than .8V below the midpoint of the supply voltages (0V with
split supplies, V
/2 with single supplies) doing so could
cause transistor Q1 to Zener resulting in damage to the
disable circuit. The core amplifier is unaffected by this, but
disable operation could become slower as a result.
Disabled, the LMH6720 inputs and output become high im-
pedances. While disabled the LMH6720 quiescent current is
approximately 500μA. Because of the pull up resistor on the
disable circuit the I
and I
currents are not balanced in
the disabled state. The positive supply current (I
) is ap-
proximately 500μA while the negative supply current (I
) is
only 200μA. The remaining I
EE
current of 300μA flows
through the disable pin.
The disable function can be used to create analog switches
or multiplexers. Implement a single analog switch with one
LMH6720 positioned between an input and output. Create
an
analog
multiplexer
with
LMH6720 is at it’s best at a gain of 1 for multiplexer appli-
cations because there is no R
G
to shunt signals to ground.
several
LMH6720’s.
The
DISABLE LIMITATIONS (LMH6720 ONLY)
The feedback Resistor (R
F
) limits off isolation in inverting
gain configurations. During shutdown the impedance of the
LMH6720 inputs and output become very high (
>
1M
),
however R
F
and R
G
are the dominant factor for effective
output impedance.
Do not apply voltages greater than +V
or less than 0V
(V
/2 single supply) to the disable pin. The input ESD
diodes will also conduct if the signal leakage through the
feedback resistors brings the inverting input near either sup-
ply rail.
LAYOUT CONSIDERATIONS
Whenever questions about layout arise, use the evaluation
board as a guide. The following Evaluation boards are avail-
able with sample parts:
LMH6714
SOT
SOIC
SOT
SOIC
SOIC
CLC730216
CLC730227
CLC730216
CLC730227
CLC730231
LMH6720
LMH6722
To reduce parasitic capacitances, the ground plane should
be removed near the input and output pins. To reduce series
inductance, trace lengths of components in the feedback
loop should be minimized. For long signal paths controlled
impedance lines should be used, along with impedance
matching at both ends.
Bypass capacitors should be placed as close to the device
as possible. Bypass capacitors from each rail to ground are
applied in pairs. The larger electrolytic bypass capacitors
can be located anywhere on the board, the smaller ceramic
capacitors should be placed as close to the device as pos-
sible. In addition
Figure 2
shows a capacitor (C1) across the
supplies with no connection to ground. This capacitor is
optional, however it is required for best 2nd Harmonic sup-
pression. If this capacitor is omitted C2 and C3 should be
increased to .1μF each.
VIDEO PERFORMANCE
The LMH6714/6720/6722 has been designed to provide ex-
cellent performance with both PAL and NTSC composite
video signals. Performance degrades as the loading is in-
creased, therefore best performance will be obtained with
back terminated loads. The back termination reduces reflec-
tions from the transmission line and effectively masks ca-
pacitance from the amplifier output stage. While all parts
offer excellent video performance the LMH6714 and
LMH6722 are slightly better than the LMH6720.
20056521
FIGURE 4. Enable/Disable Operation
20056524
FIGURE 5. Typical Application with Suggested Supply
Bypassing
L
www.national.com
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMH6720MFX/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(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 |
| LMH6722 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Wideband Video Op Amp; Single, Single with Shutdown and Quad |
| LMH6722J-QML | 制造商:Texas Instruments 功能描述: |
| LMH6722MA | 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(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 |
| LMH6722MA/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(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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