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參數(shù)資料
| 型號(hào)： | LOG102AIDR |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 模擬運(yùn)算功能 |
| 英文描述： | LOG OR ANTILOG AMPLIFIER, 1.4 MHz BAND WIDTH, PDSO14 |
| 封裝： | GREEN, PLASTIC, MS-012AB, SOIC-14 |
| 文件頁數(shù)： | 18/18頁 |
| 文件大?。?/td> | 490K |
| 代理商： | LOG102AIDR |
www.ti.com
LOG102
9
SBOS211B
A
2
A
1
I
1
Q
1
Q
2
V
OUT = (1V) 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
I
V
RR
R
nV
I
OUT
L
OUT
T
=
+
=
+
12
1
2
12
1
2
1
log
Using the base-emitter voltage relationship of matched
bipolar transistors, the LOG102 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 LOG102
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(9)
(10)
(11)
FIGURE 11. Simplified Model of Log Amplifier.
(8)
or
It should be noted that the temperature dependance
associated with VT = kT/q is internally compensated on
the LOG102 by making R1 a temperature sensitive resis-
tor with the required positive temperature coefficient.
USING A LARGER REFERENCE VOLTAGE
REDUCES OFFSET ERRORS
Using a larger reference voltage to create the reference
current minimizes errors due to the LOG102’s input offset
voltage. Maintaining an increasing output voltage as a func-
tion of increasing photodiode current is also important in
many optical sensing applications. All zeros from the A/D
converter output represent zero or low scale photodiode
current. Inputting the reference current into I1, and designing
IREF such that it is as large or larger than the expected
maximum photodiode current is accomplished using this
requirement. The LOG102 configured with the reference
current connecting I1 and the photodiode current connecting
to I2 is shown in Figure 12. A3 is configured as a level shifter
with inverting gain and is used to scale the photodiode
current directly into the A/D input voltage range.
The wide dynamic range of the LOG102 is useful for measuring
avalanche photodiode current (APD) (see Figure 13).
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LOG102AIDRG4 | 功能描述:對數(shù)放大器 Logarithmic and 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 |
| LOG104 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:LOGARITHMIC AND LOG RATIO AMPLIFIER |
| LOG104AID | 功能描述:對數(shù)放大器 LOGARITHMIC 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 |
| LOG104AID | 制造商:Texas Instruments 功能描述:IC AMP LOG SMD SOIC8 104 |
| LOG104AIDE4 | 功能描述:對數(shù)放大器 LOGARITHMIC 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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