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參數(shù)資料
| 型號： | LOG114AIRGVT |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 模擬運算功能 |
| 英文描述： | LOG OR ANTILOG AMPLIFIER, PQCC16 |
| 封裝： | 4 X 4 MM, GREEN, PLASTIC, QFN-16 |
| 文件頁數(shù)： | 8/29頁 |
| 文件大?。?/td> | 637K |
| 代理商： | LOG114AIRGVT |
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LOG114
SBOS301A MAY 2004 REVISED MARCH 2007
www.ti.com
16
SETTING THE REFERENCE CURRENT
When the LOG114 is used to compute logarithms, ei-
ther I1 or I2 can be held constant to become the refer-
ence current to which the other is compared.
If IREF is set to the lowest current in the span of the signal
current (as shown in the front page figure), VLOGOUT will
range from:
V
LOGOUT + 0.375
log
10
I
1 min
I
1 max signal
^ 0V
to some maximum value:
V
LOGOUT + 0.375
log
10
I
1 min
I
1 max signal
While convenient, this approach does not usually result
in best performance, because I1 min accuracy is difficult
to achieve, particularly if it is < 20nA.
A better way to achieve higher accuracy is to choose
IREF to be in the center of the full signal range. For
example, for a signal range of 1nA to 1mA, it is better
to use this approach:
I
REF
+ I
SIGNAL min
1mA 1nA
+ 1mAdc
than it is to set IREF = 1nA. It is much easier and more
precise (that is, dc accuracy, temperature stability, and
lower noise) to establish a 1mA dc current level than a
1nA level for the reference current.
The reference current may be derived from a voltage
source with one or more resistors. When a single resis-
tor is used, the value may be large depending on IREF.
If IREF is 10nA and +2.5V is used:
RREF = 2.5V/10nA = 250M
A voltage divider may be used to reduce the value of the
resistor, as shown in Figure 5. When using this method,
one must consider the possible errors caused by the
amplifier input offset voltage. The input offset voltage of
amplifier A1 has a maximum value of 4mV in a ±5V sup-
ply system, and a maximum value of 7mV in a +5V sup-
ply system. Resistor temperature stability and noise
contributions should also be considered.
A
1
+
R
2
R
1
+5V
R
3
V
REF =100mV
R
3 >> R2
I
REF
V
OS
1
Figure 5. T-Network for Reference Current.
VREF may be an external precision voltage reference, or
the on-chip 2.5V voltage reference of the LOG114.
IREF can be derived from an external current source,
such as that shown in Figure 6.
2N2905
I
REF
R
REF
2N2905
+15V
15V
I
REF =
6V
R
REF
3.6k
6V
IN834
Figure 6. Temperature-Compensated Current Source.
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| LOG114AIRGVTG4 | 功能描述:對數(shù)放大器 Prec High-Speed 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 |
| LOG114EVM | 功能描述:放大器 IC 開發(fā)工具 LOG114 Eval Mod RoHS:否 制造商:International Rectifier 產(chǎn)品:Demonstration Boards 類型:Power Amplifiers 工具用于評估:IR4302 工作電源電壓:13 V to 23 V |
| LOG1527 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:由CMOS工藝設(shè)計制造的可內(nèi)燒的學習碼編碼IC. |
| LOG2112 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:LOGARITHMIC AND LOG RATIO AMPLIFIERS |
| LOG2112AIDW | 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 |
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