Circuit Project Electronic

A modification of the Colpitts circuit, called a Clapp oscillator, is shown at the left. This circuit can be built and tested. The tuning capacitor is in series with the inductance; here, it is a fixed capacitor, but in a VFO it would be variable. All three capacitors are 0.001 μF in this circuit, but in a practical circuit, the capacitance in series with the inductor would be much smaller than the other two (perhaps 50 pF), and would give a considerable range of frequencies. The inductor was a 120 μH (shown as uH on schematics) ferrite core inductor I happened to have on hand. The 1 mH inductor in the source lead is a radio-frequency choke or RFC, designed to retain its inductance when a reasonable DC current passes through it. Here, it separates the bias circuit from the RF circuit. The leads of the MPF 102 JFET are DSG, in that order, when looking at the flat side of the package with the leads downward.[...]
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http://mysite.du.edu/~etuttle/electron/elect16.htm