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參數(shù)資料
| 型號： | LM6172AMJRQML |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 音頻／視頻放大 |
| 英文描述： | VIDEO AMPLIFIER, CDIP8 |
| 封裝： | CERDIP-8 |
| 文件頁數(shù)： | 4/21頁 |
| 文件大?。?/td> | 635K |
| 代理商： | LM6172AMJRQML |
Driving Capacitive Loads (Continued)
Layout Consideration
PRINTED CIRCUIT BOARDS AND HIGH SPEED OP
AMPS
There are many things to consider when designing PC
boards for high speed op amps. Without proper caution, it is
very easy to have excessive ringing, oscillation and other de-
graded AC performance in high speed circuits. As a rule, the
signal traces should be short and wide to provide low induc-
tance and low impedance paths. Any unused board space
needs to be grounded to reduce stray signal pickup. Critical
components should also be grounded at a common point to
eliminate voltage drop. Sockets add capacitance to the
board and can affect frequency performance. It is better to
solder the amplifier directly into the PC board without using
any socket.
USING PROBES
Active (FET) probes are ideal for taking high frequency mea-
surements because they have wide bandwidth, high input
impedance and low input capacitance. However, the probe
ground leads provide a long ground loop that will produce er-
rors in measurement. Instead, the probes can be grounded
directly by removing the ground leads and probe jackets and
using scope probe jacks.
COMPONENTS SELECTION AND FEEDBACK
RESISTOR
It is important in high speed applications to keep all compo-
nent leads short because wires are inductive at high fre-
quency.
For
discrete
components,
choose
carbon
composition-type resistors and mica-type capacitors. Sur-
face mount components are preferred over discrete compo-
nents for minimum inductive effect.
Large values of feedback resistors can couple with parasitic
capacitance and cause undesirable effects such as ringing
or oscillation in high speed amplifiers. For LM6172, a feed-
back resistor less than 1 k
gives optimal performance.
Compensation for Input
Capacitance
The combination of an amplifier’s input capacitance with the
gain setting resistors adds a pole that can cause peaking or
oscillation. To solve this problem, a feedback capacitor with
a value
C
F > (RG xCIN)/RF
can be used to cancel that pole. For LM6172, a feedback ca-
pacitor of 2 pF is recommended.
Figure 4 illustrates the com-
pensation circuit.
Power Supply Bypassing
Bypassing the power supply is necessary to maintain low
power supply impedance across frequency. Both positive
and negative power supplies should be bypassed individu-
ally by placing 0.01 F ceramic capacitors directly to power
supply pins and 2.2 F tantalum capacitors close to the
power supply pins.
DS012581-45
FIGURE 1. Isolation Resistor Used
to Drive Capacitive Load
DS012581-51
FIGURE 2. The LM6172 Driving a 510 pF Load
with a 30
Isolation Resistor
DS012581-52
FIGURE 3. The LM6172 Driving a 220 pF Load
with a 50
Isolation Resistor
DS012581-46
FIGURE 4. Compensating for Input Capacitance
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM6172AMWGFQMLV | 制造商:TI 制造商全稱:Texas Instruments 功能描述:Dual High Speed, Low Power, Low Distortion, Voltage Feedback Amplifiers |
| LM6172AMWG-QML | 制造商:National Semiconductor Corporation 功能描述:OP Amp Dual Volt Fdbk ±18V/36V 16-Pin CPAK 制造商:National Semiconductor 功能描述:OP Amp Dual Volt Fdbk ±18V/36V 16-Pin CPAK |
| LM6172IM | 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 |
| LM6172IM/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual High Speed,Low Pwr 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 |
| LM6172IM/NOPB | 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC |
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