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参数资料
| 型号： | LOG2112AIDW |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 模拟运算功能 |
| 英文描述： | LOG OR ANTILOG AMPLIFIER, 1.4 MHz BAND WIDTH, PDSO16 |
| 封装： | ROHS COMPLIANT, PLASTIC, MS-013AA, SOIC-16 |
| 文件页数： | 20/20页 |
| 文件大小： | 621K |
| 代理商： | LOG2112AIDW |
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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相关代理商/技术参数 |
参数描述 |
|---|---|
| LOG2112AIDWE4 | 功能描述:对数放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道数量:3 带宽:3 dB 共模抑制比（最小值）: 输入补偿电压:+/- 7 mV 输入电压范围（最大值）:5.5 V 工作电源电压:4.5 V to 5.5 V 电源电流:+/- 15 mA 工作温度范围:- 40 C to +85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-16 封装:Reel |
| LOG2112AIDWR | 功能描述:对数放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道数量:3 带宽:3 dB 共模抑制比（最小值）: 输入补偿电压:+/- 7 mV 输入电压范围（最大值）:5.5 V 工作电源电压:4.5 V to 5.5 V 电源电流:+/- 15 mA 工作温度范围:- 40 C to +85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-16 封装:Reel |
| LOG2112AIDWRE4 | 功能描述:对数放大器 Precision Log & Log Ratio Amp RoHS:否 制造商:Texas Instruments 通道数量:3 带宽:3 dB 共模抑制比（最小值）: 输入补偿电压:+/- 7 mV 输入电压范围（最大值）:5.5 V 工作电源电压:4.5 V to 5.5 V 电源电流:+/- 15 mA 工作温度范围:- 40 C to +85 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-16 封装:Reel |
| LOGIC | 制造商:SALEAE LLC 功能描述:8 Channel Logic Analyzer |
| LOGIC PCBA | 制造商:Misc 功能描述: |
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