集成對數放大器的工業應用:Integrated logarithmic amplifiers for industrial applications

Many industrial applications measure physical quantities
over a wide dynamic range. These applications use logarithmic
amplifiers (log amps) to match a transmitter’s
dynamic output to the linear input range of a signal gauge.
Figure 1 shows a typical signal chain to measure photo
currents over a dynamic range of seven decades.
Log amps of the past were built with hybrid techniques.
Today’s CMOS technology enables the integration of the logging
circuit and additional support functions, such as voltage
references and uncommitted op amps, into a single chip.
This article describes the operation and architecture of
integrated log amps and provides two application examples
using the Texas Instruments (TI) LOG112 and LOG2112.