參數(shù)資料
型號： LOG112
元件分類： 跨阻放大器
英文描述： Precision, High-Speed Transimpedance Amplifier
中文描述： 精密，高速互阻抗放大器
文件頁數(shù)： 14/18頁
文件大?。?/td> 362K
代理商： LOG112
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SBOS291E NOVEMBER 2003 REVISED NOVEMBER 2004
www.ti.com
14
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
OPA380
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 OPA380 series op amps can drive up to 500pF pure
capacitive load. Increasing the gain enhances the
amplifier’s ability to drive greater capacitive loads (see
the Typical Characteristic curve,
Small Signal
Overshoot vs Capacitive Load
).
One method of improving capacitive load drive in the
unity-gain configuration is to insert a 10
to 20
resistor in series with the load. This reduces ringing with
large capacitive loads while maintaining DC accuracy.
DRIVING FAST 16-BIT ANALOG-TO-DIGITAL
CONVERTERS (ADC)
The OPA380 series is optimized for driving a fast 16-bit
ADC such as the ADS8411. The OPA380 op amp
buffers the converter’s input capacitance and resulting
charge injection while providing signal gain. Figure 12
shows the OPA380 in a single-ended method of
interfacing the ADS8411 16-bit, 2MSPS ADC. For
additional information, refer to the ADS8411 data sheet.
OPA380
R
F
15
6800pF
ADS8411
C
F
RC Values shown are optimized for the
ADS8411
values may vary for other ADCs.
Figure 12. Driving 16-bit ADCs
OPA380
R
F
R
1
(Provides highspeed amplification
with very low offset and drift.)
V
OUT
C
F
V
IN
Figure 13. OPA380 inverting gain configuration
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參數(shù)描述
LOG112AID 功能描述:對數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
LOG112AID 制造商:Texas Instruments 功能描述:IC AMP LOG SMD SOIC14 112
LOG112AIDE4 功能描述:對數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
LOG112AIDR 功能描述:對數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
LOG112AIDRE4 功能描述:對數(shù)放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道數(shù)量:3 帶寬:3 dB 共模抑制比（最小值）: 輸入補(bǔ)償電壓:+/- 7 mV 輸入電壓范圍（最大值）:5.5 V 工作電源電壓:4.5 V to 5.5 V 電源電流:+/- 15 mA 工作溫度范圍:- 40 C to +85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel
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