In this paper

the basic nature of AGC systems is explained and a new method is presented

which generalizes the expressions for the gain control characteristic of controlled amplifiers. Known as logarithmic sub-region linearization （LSL）

this method has many advantages over common sub-region linearization. Using the LSL method

it is demonstrated that any AGC system may be resolved into some linear systems in first order approximation. It is also demonstrated that the AGC systems with exponential gain control characteristic may strictly be transformed into a linear system by using any logarithmic amplifier. And practical AGC systems may strictly be transformed into some linear systems by using a logarithmic amplifier. Based on the above analyses

the conception on transfer function of AGC systems is presented. Thus

the questions of AGC systems are simplified. In this paper

the stability of some pulse AGC systems is also discussed. The equations for stability condition are derived

and the associated curves are given.