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參數(shù)資料
| 型號： | LOG112AID |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 模擬運算功能 |
| 英文描述： | LOG OR ANTILOG AMPLIFIER, 1.4 MHz BAND WIDTH, PDSO14 |
| 封裝： | ROHS COMPLIANT, PLASTIC, MS-012AB, SOIC-14 |
| 文件頁數(shù)： | 20/20頁 |
| 文件大?。?/td> | 621K |
| 代理商： | LOG112AID |
LOG112, 2112
9
SBOS246D
www.ti.com
FIGURE 8. Precision Current Inverter/Current Source.
1k
+5V
1.5k
1.5k
100k
10nA to 1mA
LOG112
10nA to 1mA
100k
100k
(+3.3V Back Bias)
+3.3V(1)
1/2
OPA2335
1/2
OPA2335
Photodiode
Pin 1 or Pin 14
100k
NOTE: (1) +3.3V bias is an arbitrary dc level < 5V that also
appears on the
IN through the op amp where it
applies a reverse bias to the photodiode.
VOLTAGE INPUTS
The LOG112 and LOG2112 give the best performances with
current inputs. Voltage inputs may be handled directly with
series resistors, but the dynamic input range is limited to
approximately three decades of input voltage by voltage
noise and offsets. The transfer function of Equation 13
applies to this configuration.
ACHIEVING HIGHER ACCURACY WITH HIGHER
INPUT CURRENTS
As input current to the LOG112 increases, output accuracy
degrades. For a 4.5mA input current on
±5V supplies and a
10mA input current on
±12V supplies, total output error can
be between 15% and 25%. Applying a common-mode volt-
age to VCM of at least +1V and up to 2.5V, brings the log
transistors out of saturation and reduces output error to
approximately 10%. To avoid forward biasing a photodiode,
return the cathode to the VCM pin, as shown in Figure 9. To
reverse bias the photodiode, apply a more positive voltage to
the cathode than the anode.
APPLICATION CIRCUITS
LOG RATIO
One of the more common uses of log ratio amplifiers is
to measure absorbance. See Figure 10 for a typical application.
Absorbance of the sample is A = log
λ
1/ λ1
(3)
If D1 and D2 are matched A ∝ (0.5V) logI1/I2
(4)
FIGURE 9. Extending Input Current Level and Improving Accuracy by Applying a Common-Mode Voltage.
A
2
A
1
Q
1
Q
2
C
I
1
V
REF – GND
V
O3
V+ = +5V
GND
LOG112
A
3
R
2
R
1
V
REF
100k
+2.5V
150k
R
REF
+IN3
V
LOGOUT
–IN3
V– = –5V
V
CM
I
2
V
REF
65
3
4
7
9
10
13
11
8
14
1
+1.5V
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| 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 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-16 封裝:Reel |
| LOG114 | 制造商:BB 制造商全稱:BB 功能描述:Precision, High-Speed Transimpedance Amplifier |
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