參數(shù)資料
型號： LMH6732MAX
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 音頻／視頻放大
英文描述： High Speed Op Amp with Adjustable Bandwidth
中文描述： 1 CHANNEL, VIDEO AMPLIFIER, PDSO8
封裝： SOIC-8
文件頁數(shù)： 15/19頁
文件大?。?/td> 970K
代理商： LMH6732MAX
Application Information:
(Continued)
The terminal marked "R
P
" is tied to a potential through a
resistor R
P
. The current flowing through R
P
(I
P
) sets the
LMH6732’s supply current. Throughout the data sheet, the
voltages applied to R
P
and V
are both considered to be
5V. However, the two potentials do not necessarily have to
be the same. This is beneficial in applications where non-
standard supply voltages are used or when there is a need to
power down the op amp via digital logic control.
The relationship between I
CC
and I
P
is given by:
l
= I
CC
/57 (approximate ratio at I
CC
= 3.4mA; consult “I
CC
vs. I
P
CC
).
Knowing I
P
leads to a direct calculation of R
P
.
R
P
+ 5k
= [(V
+
-1.6)-V
]/ I
P
R
P
+ 5k
= =8.4 /I
P
(for V
+
= 5V and V
= 5V).
First, an operating point needs to be determined from the
plots & specifications as discussed above. From this, I
P
is
obtained. Knowing I
P
and the potential R
P
is tied to, R
P
can
be calculated.
EXAMPLE
An application requires that V
=
±
3V and performance in
the 1mAoperating point range. The required I
P
can therefore
be determined as follows:
I
P
=21μA
R
P
is connected from pin 8 to V
. Calculate R
P
under these
conditions:
R
P
+ 5k
= [(V
+
-1.6)-V
] / I
P
R
P
+ 5k
R
P
= 205k
The LMH6732 will have performance similar to R
= 412k
shown on the datasheet, but with 40% less power dissipation
due to the reduced supply voltages. The op amp will also
have a more restricted common-mode range and output
swing.
DYNAMIC SHUTDOWN CAPABILITY
The LMH6732 may be powered on and off very quickly by
controlling the voltage applied to R
. If R
is connected
between pin 8 and the output of a CMOS gate powered from
±
5V supplies, the gate can be used to turn the amplifier on
and off. This is shown in
Figure 4
below:
When the gate output is switched from high to low, the
LMH6732 will turn on. In the off state, the supply current
typically reduces to 1μA or less. The LMH6732’s "off state"
supply current is reduced significantly compared to the
CLC505. This extremely low supply current in the "off state"
is quite advantageous since it allows for significant power
saving and minimizes feed-through. To improve switching
time, a speed up capacitor from the gate output to pin 8 is
recommended. The value of this capacitor will depend on the
R
value used and is best established experimentally.
Turn-on and turn-off times of
<
20ns (I
CC
= 9mA) are achiev-
able with ordinary CMOS gates.
EXAMPLE
An open collector logic device is used to dynamically control
the power dissipation of the circuit. Here, the desired con-
nection for R
P
is from pin 8 to the open collector logic device.
When the logic gate goes low, the LMH6732 is turned on.
The LMH6732 V
+
connection would be to +5V supply.
Performance desired is that given for I
CC
= 3.4mA under
standard conditions. From the I
CC
vs. I
P
plot, I
P
= 61μA.
Then calculating R
P
:
R
P
+ 5k
= [(5V-1.6V)- 0] / 61μA
R
P
= 51k
20060246
FIGURE 3. Supply Current Control’s Simplified
Schematic
20060260
FIGURE 4. Dynamic Control of Power Consumption
Using CMOS Logic
20060261
FIGURE 5. Controlling Power On State with TTL Logic
(Open Collector Output)
L
www.national.com
15
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LMH6732MAX/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
LMH6732MF 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
LMH6732MF/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
LMH6732MFX 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
LMH6732MFX/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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