LOG101
LOG
101
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
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 V
OUT
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.
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
I
2
V+
4
I
1
1
V
OUT
= (1V) • LOG (I
1
/I
2
)
C
C
8
LOG101
Q
1
Q
2
A
1
A
2
R
2
3
V
OUT
R
1
5
GND
V–
6
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.
Copyright © 2002-2004, Texas Instruments Incorporated
www.ti.com
TI [ TEXAS INSTRUMENTS ]
