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参数资料
| 型号： | LOG104AID |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 模拟运算功能 |
| 英文描述： | LOG OR ANTILOG AMPLIFIER, 0.01 MHz BAND WIDTH, PDSO8 |
| 封装： | GREEN, PLASTIC, MS-012AA, SOIC-8 |
| 文件页数： | 13/14页 |
| 文件大小： | 294K |
| 代理商： | LOG104AID |
www.ti.com
LOG104
8
SBOS243C
A
2
A
1
I
1
Q
1
Q
2
V
OUT = (0.5V) LOG
I
1
I
2
I
2
I
1
I
2
++
––
R
2
V
OUT
V
L
R
1
V
BE1
V
BE2
also
VV
RR
R
V
RR
R
nV
I
OUT
L
OUT
T
=
+
=
+
12
1
12
1
2
log
VV
I
OUT = 05
1
2
.
log
Using the base-emitter voltage relationship of matched
bipolar transistors, the LOG104 establishes a logarith-
mic function of input current ratios. Beginning with the
base-emitter voltage defined as:
VV
I
where V
kT
q
BE
T
C
S
T
==
ln
:
k = Boltzmann’s constant = 1.381 10–23
T = Absolute temperature in degrees Kelvin
q = Electron charge = 1.602 10–19 Coulombs
IC = Collector current
IS = Reverse saturation current
From the circuit in Figure 11, we see that:
VV
V
LBE
BE
=
12
–
Substituting (1) into (2) yields:
VV
I
V
I
LT
S
T
S
=
1
2
ln
–
ln
If the transistors are matched and isothermal and
VTI = VT2, then (3) becomes:
VV
I
VV
I
and
ce
xx
Vn V
I
LT
SS
LT
=
=
1
12
1
2
10
1
2
23
ln
– ln
ln
sin
ln
. log
log
where n = 2.3
INSIDE THE LOG104
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(9)
(10)
(11)
FIGURE 11. Simplified Model of a Log Amplifier.
(8)
or
FIGURE 13. Transfer Function with Varying I2 and I1.
(5)
3.0
3.5
2.0
2.5
1.0
1.5
0.5
0.0
–3.0
–3.5
–2.0
–2.5
–1.0
–0.5
–1.5
1nA
10nA
100nA 1
A
10
A
100
A
1m
A
10mA
100pA
V
OUT
(V)
I 2 =
100pA
I 2 =
1nA
I 2 =
10nA
I 2 =
100nA
I 2 =
1
A
I 2 =
10
A
I 2 =
100
A
I 2 =
1m
A
I
1
V
OUT = (0.5V) LOG (I1/I2)
DEFINITION OF TERMS
TRANSFER FUNCTION
The ideal transfer function is:
VOUT = 0.5V logI1/I2
See Figure 12 for the graphical representation of the transfer
over valid operating range for the LOG104.
ACCURACY
Accuracy considerations for a log ratio amplifier are some-
what more complicated than for other amplifiers. This is
because the transfer function is nonlinear and has two
inputs, each of which can vary over a wide dynamic range.
The accuracy for any combination of inputs is determined
from the total error specification.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LOG104AID | 制造商:Texas Instruments 功能描述:IC AMP LOG SMD SOIC8 104 |
| LOG104AIDE4 | 功能描述:对数放大器 LOGARITHMIC 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 |
| LOG104AIDG4 | 功能描述:对数放大器 LOGARITHMIC 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 |
| LOG104AIDR | 功能描述:对数放大器 LOGARITHMIC 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 |
| LOG104AIDRE4 | 功能描述:对数放大器 LOGARITHMIC 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 |
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