A 2.5 V temperature compensated CMOS logarithmic amplifier

Abstract

A new temperature compensated low voltage current-mode CMOS logarithmic amplifier is presented. The logarithmic amplifier uses seven cascaded limiting current amplifiers for piece-wise approximation of the logarithmic function and a current peak detector for detecting signal amplitude with a dynamic range of 60 dB. The circuit uses a current reference to stabilize the temperature dependencies down to /spl plusmn/1 dB. The designed amplifier is fabricated with a 1.2 /spl mu/m CMOS process. It operates with down to a 2.2 V single supply voltage and the power consumption is 3 mW with a 2.5 V supply.