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參數(shù)資料
| 型號(hào)： | LM8272 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | RRIO, High Output Current & Unlimited Cap Load Op Amp in Miniature Package |
| 中文描述： | RRIO，高輸出電流 |
| 文件頁數(shù)： | 13/14頁 |
| 文件大?。?/td> | 667K |
| 代理商： | LM8272 |
Application Notes
(Continued)
OUTPUT SHORT CIRCUIT CURRENT AND
DISSIPATION ISSUES:
The LM8272 output stage is designed for maximum output
current capability. Even though momentary output shorts to
ground and either supply can be tolerated at all operating
voltages, longer lasting short conditions can cause the junc-
tion temperature to rise beyond the absolute maximum rat-
ing of the device, especially at higher supply voltage condi-
tions. Below supply voltage of 6V, output short circuit
condition can be tolerated indefinitely.
With the Op Amp tied to a load, the device power dissipation
consists of the quiescent power due to the supply current
flow into the device, in addition to power dissipation due to
the load current. The load portion of the power itself could
include an average value (due to a DC load current) and an
AC component. DC load current would flow if there is an
output voltage offset, or the output AC average current is
non-zero, or if the Op Amp operates in a single supply
application where the output is maintained somewhere in the
range of linear operation. Therefore:
P
total
= P
Q
+ P
DC
+ P
AC
P
Q
= I
S
· V
S
Op Amp Quiescent Power
Dissipation
DC Load Power
AC Load Power
P
DC
= I
O
· (V
r
- V
o
)
P
AC
= See Table 1 below
where:
I
S
: Supply Current
V
S
: Total Supply Voltage (V
+
- V
)
V
O
: Average Output Voltage
V
r
: V
+
for sourcing and V
for sinking current
Table 1 below shows the maximum AC component of the
load power dissipated by the Op Amp for standard Sinusoi-
dal, Triangular, and Square Waveforms:
TABLE 1. Normalized AC Power Dissipated in the
Output Stage for Standard Waveforms
P
AC
(W.
/V
2
)
Triangular
46.9 x 10
3
Sinusoidal
50.7 x 10
3
Square
62.5 x 10
3
The table entries are normalized to V
S2
/R
. To figure out the
AC load current component of power dissipation, simply
multiply the table entry corresponding to the output wave-
form by the factor V
S2
/R
. For example, with
±
12V supplies,
a 600
load, and triangular waveform power dissipation in
the output stage is calculated as:
P
AC
= (46.9 x 10
3
) · [24
2
/600] = 45.0mW
OTHER APPLICATION HINTS:
The use of supply decoupling is mandatory in most applica-
tions. As with most relatively high speed/high output current
OpAmps, best results are achieved when each supply line is
decoupled with two capacitors; a small value ceramic ca-
pacitor (
～
0.01μF) placed very close to the supply lead in
addition to a large value Tantalum or Aluminum (
>
4.7μF).
The large capacitor can be shared by more than one device
if necessary. The small ceramic capacitor maintains low
supply impedance at high frequencies while the large ca-
pacitor will act as the charge “bucket” for fast load current
spikes at the Op Amp output. The combination of these
capacitors will provide supply decoupling and will help keep
the Op Amp oscillation free under any load.
LM8272 ADVANTAGES:
Compared to other Rail-to-Rail Input/Output devices, the
LM8272 offers several advantages such as:
Improved cross over distortion
Nearly constant supply current throughout the output
voltage swing range and close to either rail.
Nearly constant Unity gain frequency (f
) and Phase
Margin (Phi
m
) for all operating supplies and load condi-
tions.
No output phase reversal under input overload condition.
L
www.national.com
13
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| LM8272MM | 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 |
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| LM8272MM/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RRIO HI OTPT UNLIMIT CAP LOAD OP 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 |
| LM8272MMX | 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 |
| LM8272MMX/NOPB | 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 |
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