Design a 28Mhz colpitts oscillator

Hi am new to this oscillator design. I want to design a colpitts crystal oscillator with 28Mhz output using mosfet instead of bjt. can anyone please suggest any models which help me to generate 28Mhz o/p. Thank you

I would (for the moment) forget about the 28MHz part and use Google for basic Colpitts circuit designs. You will see many that use op-amps or transistors but the basic structure will be the same. You can also narrow the search down to those that use mosfets (such as http://www.datasheetdir.com/Nanopower-Lc-colpitts-Oscillator-Circuit+Application-Notes found at random).
After that you can start to design one that will oscillate at the frequency you are interested in.
What do you want it for? Are you looking for frequency stability, or low component count or what?
Susan

search "colpitts 28mhz" and select google "images" tab for examples.

Aussie Susan said:

I would (for the moment) forget about the 28MHz part and use Google for basic Colpitts circuit designs. You will see many that use op-amps or transistors but the basic structure will be the same. You can also narrow the search down to those that use mosfets (such as http://www.datasheetdir.com/Nanopower-Lc-colpitts-Oscillator-Circuit+Application-Notes found at random).
After that you can start to design one that will oscillate at the frequency you are interested in.
What do you want it for? Are you looking for frequency stability, or low component count or what?
Susan

Click to expand...

Its the reference frequency for a PLL

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Aussie Susan said:

I would (for the moment) forget about the 28MHz part and use Google for basic Colpitts circuit designs. You will see many that use op-amps or transistors but the basic structure will be the same. You can also narrow the search down to those that use mosfets (such as http://www.datasheetdir.com/Nanopower-Lc-colpitts-Oscillator-Circuit+Application-Notes found at random).
After that you can start to design one that will oscillate at the frequency you are interested in.
What do you want it for? Are you looking for frequency stability, or low component count or what?
Susan

Click to expand...

I want a Colpitts oscillator which uses an external off-chip crystal.

One point to consider is if your crystal is the fundamental type, or an overtone type.
The required circuits will be quite different.

Overtone oscillators almost always have a tuned circuit to ensure the oscillator has maximum gain (at around) the required frequency of oscillation to ensure oscillation starts in the right mode.

Fundamental oscillators are pretty straight forward. But if the crystal is the overtone type you are not going to get 28 Mhz, but possibly 9.33 Mhz even though the crystal is marked 28 Mhz.

If you are using it as the input to a PLL and want it crystal drive, then why not use a simple op-amp inverter circuit.
The Colpitts oscillator will give you a sinusoidal waveform whereas the PLL will probably want a square wave which the inverter will give you.
Susan

bachhuca005 said:

Its the reference frequency for a PLL

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I want a Colpitts oscillator which uses an external off-chip crystal.

Click to expand...

I think your PLL needs a stable VCO.
What are the design specs?