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PDF LOG101 Data sheet ( Hoja de datos )
| Número de pieza | LOG101 | |
| Descripción | Precision LOGARITHMIC AND LOG RATIO AMPLIFIER | |
| Fabricantes | Burr-Brown Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LOG101 (archivo pdf) en la parte inferior de esta página. Total 13 Páginas | ||
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LOG101
LOG101
SBOS242B – MAY 2002 – REVISED JUNE 2004
Precision
LOGARITHMIC AND LOG RATIO AMPLIFIER
FEATURES
q EASY-TO-USE COMPLETE CORE FUNCTION
q HIGH ACCURACY: 0.01% FSO Over 5 Decades
q WIDE INPUT DYNAMIC RANGE:
7.5 Decades, 100pA to 3.5mA
q LOW QUIESCENT CURRENT: 1mA
q WIDE SUPPLY RANGE: ±4.5V to ±18V
APPLICATIONS
q LOG, LOG RATIO COMPUTATION:
Communication, Analytical, Medical, Industrial,
Test, and General Instrumentation
q PHOTODIODE SIGNAL COMPRESSION AMPS
q ANALOG SIGNAL COMPRESSION IN FRONT
OF ANALOG-TO-DIGITAL (A/D) CONVERTERS
DESCRIPTION
The LOG101 is a versatile integrated circuit that computes
the logarithm or log ratio of an input current relative to a
reference current.
The LOG101 is tested over a wide dynamic range of input
signals. In log ratio applications, a signal current can come
from a photodiode, and a reference current from a resistor in
series with a precision external reference.
The output signal at VOUT is trimmed to 1V per decade of input
current allowing seven decades of input current dynamic
range.
Low DC offset voltage and temperature drift allow accurate
measurement of low-level signals over a wide environmental
temperature range. The LOG101 is specified over the tem-
perature range –5°C to +75°C, with operation over
–40°C to +85°C.
Note: Protected under US Patent #6,667,650; other patents pending.
I2
I1
1
VOUT = (1V) • LOG (I1/I2)
V+
48
Q1 Q2
CC
LOG101
A1
A2
3
VOUT
R2
R1
56
GND
V–
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
www.ti.com
Copyright © 2002-2004, Texas Instruments Incorporated
1 page  
TYPICAL CHARACTERISTICS (Cont.)
At TA = +25°C, VS = ±5V, and RL = 10kΩ, unless otherwise noted.
17
15
13
11
9
7
5
3
1
–1
100pA
LOG CONFORMITY vs INPUT CURRENT
+85°C
+75°C
–40°C to +25°C
1nA 10nA 100nA 1µA 10µA 100µA 1mA
Input Current (I1 or I2)
LOG CONFORMITY vs TEMPERATURE
350
300 7 Decades
(100pA to 1mA)
250
6 Decades
200 (1nA to 1mA)
150
5 Decades
100 (1nA to 100µA)
50
0
–40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90
Temperature (°C)
APPLICATION INFORMATION
The LOG101 is a true logarithmic amplifier that uses the
base-emitter voltage relationship of bipolar transistors to
compute the logarithm, or logarithmic ratio of a current ratio.
Figure 1 shows the basic connections required for operation
of the LOG101. In order to reduce the influence of lead
inductance of power-supply lines, it is recommended that
each supply be bypassed with a 10µF tantalum capacitor in
parallel with a 1000pF ceramic capacitor, as shown in
Figure 1. Connecting the capacitors as close to the LOG101
as possible will contribute to noise reduction as well.
I1 I2
V+
10µF
1000pF
4
1
63
LOG101
VOUT
8
5
CC
10µF
1000pF
V–
FIGURE 1. Basic Connections of the LOG101.
INPUT CURRENT RANGE
To maintain specified accuracy, the input current range of the
LOG101 should be limited from 100pA to 3.5mA. Input currents
outside of this range may compromise LOG101 performance.
Input currents larger than 3.5mA result in increased
nonlinearity. An absolute maximum input current rating of
10mA is included to prevent excessive power dissipation that
may damage the logging transistor.
On ±5V supplies, the total input current (I1 + I2) is limited to
4.5mA. Due to compliance issues internal to the LOG101, to
accommodate larger total input currents, supplies should be
increased.
Currents smaller than 100pA will result in increased errors due
to the input bias currents of op amps A1 and A2 (typically 5pA).
The input bias currents may be compensated for, as shown in
Figure 2. The input stages of the amplifiers have FET inputs,
with input bias current doubling every 10°C, which makes the
nulling technique shown practical only where the temperature
is fairly stable.
R2
10kΩ
V+
R1
1MΩ
V–
5
1
I1
LOG101
8
I2
R1'
> 1MΩ
4
V– R2'
10kΩ
CC
V+
FIGURE 2. Bias Current Nulling.
3
VOUT
6 GND
LOG101
SBOS242B
www.ti.com
5
5 Page 
www.ti.com
PACKAGE OPTION ADDENDUM
9-Dec-2004
PACKAGING INFORMATION
Orderable Device
LOG101AID
LOG101AIDR
Status (1)
ACTIVE
ACTIVE
Package
Type
SOIC
SOIC
Package
Drawing
D
D
Pins Package Eco Plan (2)
Qty
8 100
None
8 2500
None
Lead/Ball Finish MSL Peak Temp (3)
CU SNPB
CU SNPB
Level-3-235C-168 HR
Level-3-235C-168 HR
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet LOG101.PDF ] | |
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