Simple Logarithmic Dc Amplifier

Abstract
A logarithmic dc amplifier circuit is described using a type 12AU7A dual triode. The amplifier output follows the equation E0=9.00−2 log10Ei with an accuracy of 2% or better for positive input voltages from 5 to 500 v. The circuit parameters may be easily adjusted to compensate for tube aging and differences in characteristics between individual tubes. Output voltage drift is low and relatively independent of filament voltage drift.

This publication has 1 reference indexed in Scilit: