Current compensation method for adjustment free stereo multiplex voltage control oscillator in FM receivers

An alternative solution of an adjustment free stereo multiplex (MPX) voltage control oscillator (VCO) circuit is proposed. The design approach taken was the utilization of a compensation circuit to change the VCO charging/discharging current, and hence, the natural frequency (f/sub n/). Manual adjustment of the external resonator was passed over which translated to a reduction in labor and timing cost.