Improving the linearity of the steady-state gain characteristic by use of nonlinear feedback

The problem of linearizing the over-all response of a device with a nonlinear gain characteristic (mainly of the saturation type) is solved by using nonlinear feedback. The nonlinear curve is approximated by an exponential which has the advantage of matching the over-all response for two conditions. To the extent that the actual gain is exactly equal to a portion of an exponential curve, the device can, theoretically, be linearized exactly over any given range extending up to saturation for any finite gain. Deviation from linearity caused by approximating the required nonlinear feedback function as a result of physical or practical considerations is investigated. Stability requirements are developed. Extensions to duodirectional devices and general systems with one nonlinear forward gain are discussed.