LOG104_14 Datasheet, PDF (1/15 Pages) Texas Instruments – LOGARITHMIC AND LOG RATIO AMPLIFIER

LOG104
LOG104
SBOS243C – MAY 2002 – REVISED APRIL 2005
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, General Instrumentation
q PHOTODIODE SIGNAL COMPRESSION AMP
q ANALOG SIGNAL COMPRESSION IN FRONT
OF ANALOG-TO-DIGITAL(A/D) CONVERTER
DESCRIPTION
The LOG104 is a versatile integrated circuit that computes
the logarithm or log ratio of an input current relative to a
reference current.
The LOG104 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 V_OUT is trimmed to 0.5V per decade of
input current, allowing seven decades of input current, dy-
namic range.
Low DC offset voltage and temperature drift allow accurate
measurement of low-level signals over a wide environmental
temperature range. The LOG104 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
V_OUT = 0.5 LOG (I₁/I₂)
V+
4
8
Q₁
Q₂
C_C
LOG104
A₁
A₂
3
V_OUT
R₂
R₁
5
6
GND
V–
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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.
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