Design of active RC variable equalizers

A simple design for realizing a single operational amplifier and single variable resistor amplitude equalizer is proposed. It allows the variation within a specified range R_r of the variable resistor and can achieve the flat response at a specified value R_f of the same resistor with a restriction R_r > 2R_f. The total resistance required is the least and is, therefore, more suitable for economic fabrication in integrated circuit form. The variable equalizers using other active devices are also derived which can operate satisfactory at much higher frequencies compared to the operational amplifier-based ones. Simulation results are in good agreement with the theoretical ones.