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:

Precision

LOGARITHMIC AND LOG RATIO AMPLIFIER

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.

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.

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

LOG104

www.ti.com

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

SBOS243B – MAY 2002 – REVISED JUNE 2004

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.

LOG

104

Note: Protected under US Patent #6,667,650; other patents pending.

A

2

A

1

1

5

8

4

6

3

Q

1

Q

2

C

C

I

2

I

1

R

1

R

2

V–

V

OUT

V+

GND

LOG104

V