The LOG102 is a versatile integrated circuit that computes the logarithm or log ratio of an input current relative to a reference current.
The LOG102 is tested over a wide dynamic range of input signals. In log ratio applications, a signal current can be generated by a photodiode, and a reference current from a resistor in series with a precision external voltage reference.
In the block diagram shown below, A3 and A4 are identical, uncommitted op amps that can be used for a variety of functions, such as filtering, offsetting, adding gain or as a comparator to detect loss of signal.
The output signal at VLOG OUT is trimmed to 1V per decade of input current. It can be scaled with an output amplifier, either A3 or A4.
Low dc offset voltage and temperature drift allow accurate measurement of low-level signals over a wide environmental temperature range. The LOG102 is specified over the temperature range, 0°C to +70°C, with operation over 40°C to +85°C.
EASY-TO-USE COMPLETE LOG RATIO FUNCTION
OUTPUT AMPLIFIERS FOR SCALING AND SIGNAL LOSS INDICATION
HIGH ACCURACY: 0.15% FSO Total Error Over 6 Decades
WIDE INPUT DYNAMIC RANGE:
6 Decades, 1nA to 1mA
LOW QUIESCENT CURRENT: 1.25mA
SO-14 PACKAGE
APPLICATIONS
ONET, OPTICAL POWER METERS
LOG, LOG RATIO COMPUTATION: Communication, Analytical, Medical, Industrial, Test, General Instrumentation
PHOTODIODE SIGNAL COMPRESSION AMP
ANALOG SIGNAL COMPRESSION IN FRONT OF A/D CONVERTER
ABSORBANCE MEASUREMENT
OPTICAL DENSITY MEASUREMENT
NOTE: U.S. Patent Pending.
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