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In this electronic project circuit you can see a very simple high efficiency Colpitts oscillator. In the higher frequency ranges, above 50 MHz, Colpitts oscillators are used because stray circuit capacitance will be in parallel with desired feedback capacitance and not cause undesirable spurious resonances that might occur with the tapped coil Hartley design. The FM VCO shown is a grounded base design with feedback from collector to emitter. 50MHz-300MHz Colpitts Oscillator Circuit Diagram: A Colpitts oscillator is one of a number of designs for electronic oscillator circuits using the combination of an inductance with a capacitor for frequency determination. The distinguishing feature of the Colpitts oscillator circuit is that the feedback signal is taken from a voltage divider made by two capacitors in series. As you can see in the circuit diagram , this electronic project require few electronic parts an provide a 50 MHz-300MHz VCO with a tuning range of 2:1.

Crystal oscillators for digital circuits are normally built as Pierce oscillators with an inverter.The inverter operates as a linear amplifier and thus requires extra current. But you can also build a crystal oscillator using an  operational amplifier (op amp for short)! If a  very low frequency is involved, for instance  32.768 kHz (commonly used for clocks), you can get away with a comparatively ‘slow’ micro power op amp.  Micropower Crystal Oscillator Circuit Diagram   In the sample circuit shown a widely avail-able TLC271 is used. On pin 8 we have the  opportunity to set the ‘bias mode’, with three  choices ranging between fast operation with  higher current consumption and slower operation at low current. For our clock crystal the middle setting will suit us fine. Pin 8 is there-fore connected to the voltage divider R1/R2. The current consumption of the entire circuit  is impressively modest and at 5 V this is just  56 µA! The osci...