walid Posted September 8, 2005 Report Share Posted September 8, 2005 VCO used frequently in FM transmitter for modulation.In Fig.VCO shown below I cut the VCO section from a FM transmitter (http://hem.passagen.se/communication/bug_rf.html) for discussion.VCO start from BB149A and end at the emitter of T1. BB149A, 3.9 pF, 15 pF and L1 make LC circuit with C varied with the i/p voice signal.My question is if we assume (for discussion) that no voice at all (i.e. capacitance of BB149 is constant value) then the frequency is constant. How we calculate it, explain with math expression. Or can you give me a method to design VCO like that shown in the figure.thanks very much. Quote Link to comment Share on other sites More sharing options...
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