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参数资料
| 型号： | LOG2112AIDWR |
| 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： | 4/20页 |
| 文件大小： | 621K |
| 代理商： | LOG2112AIDWR |
LOG112, 2112
12
SBOS246D
www.ti.com
ERRORS RTO AND RTI
As with any transfer function, errors generated by the func-
tion may be Referred-to-Output (RTO) or Referred-to-Input
(RTI). In this respect, log amps have a unique property: given
some error voltage at the log amp’s output, that error corre-
sponds to a constant percent of the input regardless of the
actual input level.
LOG CONFORMITY
For the LOG112 and LOG2112, log conformity is calculated
the same as linearity and is plotted I1/I2 on a semi-log scale.
In many applications, log conformity is the most important
specification. This is true because bias current errors are
negligible (5pA compared to input currents of 100pA and
above) and the scale factor and offset errors may be trimmed
to zero or removed by system calibration. This leaves log
conformity as the major source of error.
Log conformity is defined as the peak deviation from the best
fit straight line of the VLOGOUT versus log (I1/I2) curve. This is
expressed as a percent of ideal full-scale output. Thus, the
nonlinearity error expressed in volts over m decades is:
VLOGOUT (NONLIN) = 0.5V/dec 2NmV
(7)
where N is the log conformity error, in percent.
INDIVIDUAL ERROR COMPONENTS
The ideal transfer function with current input is:
V
V LOG
I
LOGOUT =
(
)
05
1
2
.
(8)
The actual transfer function with the major components of
error is:
VV
K
II
Nm V
LOGOUT
B
OSO
=
(
) ±
(
)
±±
05
1
2
.
log
–
(9)
The individual component of error is:
K = gain error (0.10%, typ), as specified in the specifica-
tion table.
IB1 = bias current of A1 (5pA, typ)
IB2 = bias current of A2 (5pA, typ)
N = log conformity error (0.01%, 0.13%, typ)
0.01% for m = 5, 0.13% for m = 7.5
VOSO = output offset voltage (3mV, typ)
m = number of decades over which N is specified
For example, what is the error when:
I1 = 1A and I2 = 100nA
(10)
(11)
VmV
V
LOGOUT =±
(
)
±
( )(
) ±
=
05
0001
10
5 10
10
5 10
2 0 0001 5
3 0
0 505
612
712
.
log
..
.
Since the ideal output is 0.5V, the error as a percent of the
reading is:
%
.
%.
%
error
V
=
0 505
05
100
1 01
(12)
For the case of voltage inputs, the actual transfer function is:
(13)
VV
K
V
R
I
E
R
V
R
I
E
R
Nm
V
LOGOUT
B
OS
B
OS
OSO
=
(
) ±
(
)
±
±±
05
1
11
2
22
1
2
.
log
–
Where
E
R
and
E
R
OS
1
2
(offset error) are considered to be
zero for large values of resistance from external input current
sources.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 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: |
| LOGIC SIZE 11 | 制造商:DEWALT 功能描述:DEWALT LOGIC SIZE 11 |
| LOGIC SIZE 9 | 制造商:DEWALT 功能描述:DEWALT LOGIC SIZE 9 |
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