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參數(shù)資料
| 型號： | OPA2381 |
| 元件分類： | 跨阻放大器 |
| 英文描述： | Precision, Low Power, 18MHz Transimpedance Amplifier |
| 中文描述： | 精密，低功耗，18MHz的阻放大器 |
| 文件頁數(shù)： | 13/19頁 |
| 文件大小： | 489K |
| 代理商： | OPA2381 |
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SBOS313B AUGUST 2004 REVISED NOVEMBER 2004
www.ti.com
13
BOARD LAYOUT
Minimize
capacitance at the summing junction (inverting input).
This capacitance causes the voltage noise of the op
amp to be amplified (increasing amplification at high
frequency). Using a low-noise voltage source to
reverse-bias a photodiode can significantly reduce its
capacitance.
Smaller
photodiodes
capacitance. Use optics to concentrate light on a small
photodiode.
Circuit board leakage can degrade the performance of
an otherwise well-designed amplifier. Clean the circuit
board carefully. A circuit board guard trace that
encircles the summing junction and is driven at the
same voltage can help control leakage. See Figure 11.
photodiode
capacitance
and
stray
have
lower
Guard ring
R
F
V
OUT
OPA381
λ
Figure 11. Connection of Input Guard
OTHER WAYS TO MEASURE SMALL
CURRENTS
Logarithmic amplifiers are used to compress extremely
wide dynamic range input currents to a much narrower
range. Wide input dynamic ranges of 8 decades, or
100pA to 10mA, can be accommodated for input to a
12-bit ADC. (Suggested products: LOG101, LOG102,
LOG104, LOG112.)
Extremely small currents can be accurately measured
by integrating currents on a capacitor. (Suggested
product: IVC102.)
Low-level currents can be converted to high-resolution
data words. (Suggested product: DDC112.)
For further information on the range of products
available, search
www.ti.com
using the above specific
model names or by using keywords
transimpedance
and
logarithmic
.
CAPACITIVE LOAD AND STABILITY
The OPA381 series op amps can drive greater than
100pF pure capacitive load. Increasing the gain
enhances the amplifier’s ability to drive greater
capacitive loads. See the
Phase Margin vs Load
Capacitance
typical characteristic curve.
One method of improving capacitive load drive in the
unity-gain configuration is to insert a 10
to 20
resistor inside the feedback loop, as shown in
Figure 12. This reduces ringing with large capacitive
loads while maintaining DC accuracy.
OPA381
V
OUT
V
B(1)
V+
R
F
R
S
20
C
F(3)
λ
NOTES: (1) V
B
= GND or pedestal voltage to reverse bias the photodiode.
(2) V
PD
= GND or
5V.
(3) C
F
x R
F
≥
2C
L
x R
S
.
C
L
R
L
V
PD(2)
V
Figure 12. Series Resistor in Unity-Gain Buffer
Configuration Improves Capacitive Load Drive
DRIVING 16-BIT ANALOG-TO-DIGITAL
CONVERTERS (ADC)
The OPA381 series is optimized for driving a 16-bit ADC
such as the ADS8325. The OPA381 op amp buffers the
converter input capacitance and resulting charge
injection while providing signal gain. Figure 13 shows
the OPA381 in a single-ended method of interfacing the
ADS8325 16-bit, 100kSPS ADC. For additional
information, refer to the ADS8325 data sheet.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| OPA2381AIDGKR | 功能描述:運算放大器 - 運放 Precision Lo-Power Transimpedance 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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA2381AIDGKRG4 | 功能描述:運算放大器 - 運放 Precision Lo-Power Transimpedance 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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA2381AIDGKT | 功能描述:運算放大器 - 運放 Precision Lo-Power Transimpedance 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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA2381AIDGKT | 制造商:Texas Instruments 功能描述:IC OP-AMP TRANSIMPED 18MHZ 8MSOP |
| OPA2381AIDGKTG4 | 功能描述:運算放大器 - 運放 Precision Lo-Power Transimpedance 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 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
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