Distortion caused by controlling transistor implemented in the voltage controlled amplifier

This paper describes a voltage controlled amplifier with linearized response to the controlling voltage and discusses its harmonic distortion. As a controlling element, a JFET transistor has been utilized. The design of the amplifier has been made with the aid of Maple mathematical software and National Instruments Multisim circuit simulator. During the simulations, it was found that the controlling transistor would probably introduce significant distortion into the signal path. Therefore a set of measurements on real circuit was made in order to verify that the SPICE model of the transistor provided relevant results during the simulation. Both, the simulated and the really measured parameters of the amplifier are discussed within the framework of this paper.